Optilab® and microOptilab™

User’s Guide
M1520 Rev. A

Wyatt Technology Corporation

6330 Hollister Avenue
Santa Barbara, CA 93117
Tel: +1 (805) 681-9009
Web: www.wyatt.com
:

Notices
Optilab and microOptilab User’s Guide
M1520 Rev. A
Copyright © 2019 Wyatt Technology Corporation. All rights reserved.

No part of this publication may be reproduced, stored in a retrieval system, or

transmitted in any form by any means, electronic, mechanical, photocopying,
recording, or otherwise, without prior written permission of Wyatt Technology
Corporation.
Wyatt Technology Corporation makes no warranties, either express or implied,
regarding this instrument, computer software package, its merchantability or its
fitness for any particular purpose. The software is provided “as is”, without
warranty of any kind. Furthermore, Wyatt Technology Corporation does not
warrant, guarantee, or make any representations regarding the use, or the results
of the use, of the software or written materials in terms of correctness, accuracy,
reliability, currentness, or otherwise. The exclusion of implied warranties is not
permitted by some states, so the above exclusion may not apply to you.
One or more of Wyatt Technology Corporation's trademarks may appear in this
manual. For a list of Wyatt Technology Corporation's trademarks, please see
https://www.wyatt.com/about/trademarks.
Windows and SQL Server are registered trademarks of Microsoft Corporation.
Other names may be trademarks of their respective owners.

Safety Notices
A CAUTION notice denotes a potential hazard or consideration and calls attention
to an operating protocol that, if not correctly followed or adhered to, could
potentially result in the damage to the product or personal injury. Please pay
particular attention to CAUTION notices and do not proceed until the indicated
conditions are fully understood.
A WARNING notice denotes a hazard and calls attention to an operating protocol
that, if not correctly followed or adhered to, could result in personal injury or
fatality. Please pay particular attention to WARNING notices and do not proceed
until the indicated conditions are fully understood.

Using this Manual

This user's guide describes how to set up and use the Optilab/microOptilab
instrument. Please refer to the ASTRA User's Guide for details on data analysis.
The chapters and appendices in this manual are organized as outlined in the
Contents that follow.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 2

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Manual Conventions
The IUPAC Definition Committee specifies the term molar mass for the sum of
the atomic weights of all atoms in a mole of molecules. The term molecular
weight is often used in the literature. The term molar mass will be used in this
manual.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 3

Contents

Preface ............................................................................................................8
Wyatt Technology Corporation .................................................................................... 8
Wyatt Technical Support ............................................................................................. 9
Wyatt Technology Technical Support Contact Information .......................................... 9
Sales Support ............................................................................................................ 10

Chapter 1: About the Optilab and microOptilab

Introduction to Optilab and microOptilab ......................................................................... 11
Using This Manual ........................................................................................................... 12

Chapter 2: Instrument Description

Overview .......................................................................................................................... 14
Front Panel ...................................................................................................................... 15
Rear Panel ....................................................................................................................... 16

Chapter 3: Quick Start

Setting Up the Optilab/microOptilab ................................................................................ 19

Chapter 4: Installation and Setup

Installing the Instrument .................................................................................................. 21
Power and Signal Connections ....................................................................................... 23
Power Connector ...................................................................................................... 23
Signal Connectors ..................................................................................................... 23
Communication Connectors ...................................................................................... 27
Fluid Connections ............................................................................................................ 28
Dry Gas Connection ........................................................................................................ 29
Attaching the Drain Port Connector ................................................................................. 30
Power On and Warm Up .................................................................................................. 30
Purging the Optilab/microOptilab ..................................................................................... 31
Instrument Stability Check ............................................................................................... 32

Chapter 5: Using the Front Panel Display

Using the Multi-Touch Controls ........................................................................................ 34
Front Panel Overview ...................................................................................................... 34
Dashboard Tab ................................................................................................................ 35
System Health Indicators .......................................................................................... 35
Dashboard Control Options ....................................................................................... 37
LED Control ............................................................................................................... 37
Purge Control ............................................................................................................ 37
ORBIT Control ........................................................................................................... 38
Temperature Control ................................................................................................. 39
Graph Tab ........................................................................................................................ 39

Optilab and microOptilab User’s Guide (M1520 Rev. A) 4

Contents

History Tab ....................................................................................................................... 41

Alarm Section ............................................................................................................ 41
History Section .......................................................................................................... 42
Settings Tab ..................................................................................................................... 44
Instrument Information Settings ................................................................................ 45
Network Settings ....................................................................................................... 46
Connected User Settings .......................................................................................... 46
LED Settings ............................................................................................................. 47
Temperature Settings ................................................................................................ 48
Auto Inject Settings ................................................................................................... 48
dRI Polarity Settings .................................................................................................. 48
Health Indicator Settings ........................................................................................... 48
Alarm Settings ........................................................................................................... 49
Analog Output Settings ............................................................................................. 50
System Constants Settings ....................................................................................... 51
System Control Settings ............................................................................................ 52

Chapter 6: Off-Line Measurements

Instrument Calibration for dRI .......................................................................................... 53
General Information and Sample Preparation ........................................................... 53
HPLC Pump with Injector .......................................................................................... 55
Syringe Pump Infusion .............................................................................................. 55
Collecting Data for Optilab/microOptilab dRI Calibration .......................................... 56
Instrument Calibration for aRI .......................................................................................... 58
General Information .................................................................................................. 58
Collecting Data for Optilab/microOptilab aRI Calibration .......................................... 59
dn/dc Measurement ......................................................................................................... 61
Absolute Refractive Index Measurement ......................................................................... 62

Chapter 7: In-Line HPLC Detection

Conditions for In-Line Operation ...................................................................................... 64
Sample Preparation ......................................................................................................... 65
Measurement ................................................................................................................... 65

Chapter 8: Service and Maintenance

General Maintenance ...................................................................................................... 67
Daily Maintenance ..................................................................................................... 68
Monthly Maintenance ................................................................................................ 68
Flow Cell Maintenance .................................................................................................... 69
On-line Cleaning ....................................................................................................... 69
Removing the Top Cover ................................................................................................. 71
Replacing the LED/Fiber Light Source ............................................................................ 73
Setting the LED Power to Zero ................................................................................. 73
Replacing the LED/Fiber Light Source ...................................................................... 74
Changing the Wavelength Setting ............................................................................. 77
Optimizing the LED/Fiber Light Source ..................................................................... 77
Cleaning the Air Intake Filter ........................................................................................... 77
Preventing Condensation (at Lower Temperatures) ........................................................ 78
Optilab/microOptilab Firmware Upgrades ....................................................................... 78

Chapter 9: Troubleshooting
Leak Sensors and Cleaning After a Fluid Leak ............................................................... 80

Optilab and microOptilab User’s Guide (M1520 Rev. A) 5

Contents

Replacing Plugged Tubing ............................................................................................... 83

Changing a Fuse ............................................................................................................. 83
Forward Monitor Alarm .................................................................................................... 84
LED Monitor Alarm .......................................................................................................... 85
Temperature Will Not Set Below 20 °C ............................................................................ 86
Unexpected RI Trace ....................................................................................................... 86
Wavy or Drifting Baselines ............................................................................................... 87
Noisy Baseline ................................................................................................................. 87
High Pressure .................................................................................................................. 88
Microsoft Windows Encounters Problems ....................................................................... 88

Appendix A: Acronyms and Abbreviations List

Appendix B: Operating Principles and Theory
Basic Principles ............................................................................................................... 91
Conventional Flow Cell ............................................................................................ 91
Optilab/microOptilab Flow Cell .................................................................................. 91
Measurement of the Beam Deflection Angle ................................................................... 93
Conventional Split Photodiode Based Instrument .................................................... 93
Wyatt Technology Corporation Beam Positioning Technology .................................. 94

Appendix C: Optilab Specifications

Optilab Specifications ...................................................................................................... 96
microOptilab Specifications ............................................................................................. 97

Appendix D: Wetted Materials/Cell Properties

Flow Cell Properties ........................................................................................................ 98
Thermal Properties .................................................................................................... 98
Refractive Indices ...................................................................................................... 98
Chemical Properties .................................................................................................. 98
Wetted Materials .............................................................................................................. 99
Definition of Terms ........................................................................................................... 99

Appendix E: Instrument Connectivity

Components .................................................................................................................. 101
Instrument Connections .......................................................................................... 101
LAN connection ....................................................................................................... 101
Computer connections ............................................................................................ 102
Crossover cable ...................................................................................................... 102
Ethernet cable ......................................................................................................... 103
Ethernet to USB adapter ......................................................................................... 103
Ethernet switch ........................................................................................................ 104
Connecting to a LAN ..................................................................................................... 104
One Instrument to LAN ........................................................................................... 104
One Instrument and Computer to LAN .................................................................... 105
Multiple Instruments to LAN .................................................................................... 105
Multiple Instruments and Computer to LAN ............................................................ 106
Connecting via USB ...................................................................................................... 107
One Instrument to USB via a Crossover Cable ....................................................... 107
One Instrument to USB Using an Ethernet Switch .................................................. 108
Multiple Instruments to USB .................................................................................... 108
Connecting via Ethernet When Not on a LAN ............................................................... 109

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One Instrument to Computer Using Crossover Cable ............................................. 109

One Instrument to Computer Using an Ethernet Switch ......................................... 109
Multiple Instruments to Computer Using an Ethernet Switch .................................. 110
Instrument Network Settings ......................................................................................... 110
Accessing Instruments with ASTRA .............................................................................. 111
Troubleshooting and Diagnostics .................................................................................. 112
Verifying Instrument Connections ........................................................................... 112

Appendix F: Warnings
Index

Optilab and microOptilab User’s Guide (M1520 Rev. A) 7

Preface

CONTENTS PAGE
Wyatt Technology Corporation ............................................................................. 8
Wyatt Technical Support....................................................................................... 9
Wyatt Technology Technical Support Contact Information ................................... 9
Sales Support..................................................................................................... 10

Wyatt Technology Corporation

Founded in 1982 by Dr. Phillip J. Wyatt, Wyatt Technology Corporation
(WTC) formed around his patents, ideas, and inventions to commercialize
the first light scattering instrumentation using lasers with initial support
from the Small Business Innovation Research (SBIR) contracts. Since
then we have defined and redefined the paradigm for laser light scattering
hardware, software, training, and services to meet customer needs,
including the development of related technologies such as dynamic light
scattering, refractometry, viscometry, zeta potential, and field-flow
fractionation. For additional information and the history of Wyatt
Technology®, visit us online at https://www.wyatt.com/.
Today, Wyatt Technology is a family-owned and operated company that
considers every customer to be part of the Wyatt Technology family. To
this end, we take the successes of our customers personally and welcome
opportunities to further develop our technology and strive for the utmost
level of product quality and innovation.
Our detectors are used in the world's most prestigious universities and
some the most influential companies in the world, assisting in the
research for over 14,000+ peer-reviewed articles. View our continuously
growing body of citations with an online bibliography available online at
https://www.wyatt.com/library/bibliography.html.
If you have a question about your Optilab®/microOptilab™, please refer to
this manual or consult the ASTRA® online help within the software. For
additional assistance, please contact Wyatt Technology or take advantage
of the online technical support options available to our customers in the
following section.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 8

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Wyatt Technical Support

Wyatt Technical Support offers a variety of support options for
maximizing the utility of your Optilab/microOptilab.
Located online at https://www.wyatt.com/Support, our Support Center
contains a wealth of useful resources on everything related to your Wyatt
Technology instruments, software, and applications. This center is free for
our customers and contains software updates and bug fixes, technical
notes for connecting to and using your instruments, tutorials, webinars,
certificates of analysis for Wyatt standards, and variety of additional
reference materials. We are continuously adding resources to our Support
Center.
Before contacting Wyatt Technical Support, try to resolve any issues or
problems through the ASTRA online help system, this manual, or our
Support Center online, where we provide both solutions and guidance
through a library of detailed technical notes and tutorials. If you need
additional assistance, please contact us online or by phone with the
contact information provided below but please first gather the following
information:
• The instrument serial number located on the back panel or in the front
panel display.
• The firmware version on the instrument. This can be found in the
Settings tab on the front panel display.
• The computer hardware you are using.
• If the problem is software related, please have available your Microsoft
Windows version, ASTRA version number, and software release
version, and the exact wording or screenshots of messages.
• What you were doing when the problem occurred or how to reproduce
the problem.
• How you have tried to resolve the problem before contacting us so that
we may offer you the most pertinent and relevant advice moving
forward.

Wyatt Technology Technical Support Contact Information

Electronic mail address: support@wyatt.com
E-mailing our support team will generate a ticket number and log your
request in our support system. Please be sure to whitelist
support@wyatt.com. You are encouraged to attach a representative
ASTRA data file for us to review and one of our scientific support team
members will get back to you soon!
For customers outside the United States, please feel free to contact
your local distributor for instrument support. You can find contact
information for our global offices at www.wyatt.com/Distributors.
European customers can reach Wyatt Technology Europe support at
support@wyatt.eu. Our Wyatt Technology UK office can be contacted
directly at WTUKsupport@wyatt.com.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 9

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Wyatt US & Canada Telephone Number: +1 (805) 681-9009; Option #4

Based in Santa Barbara, California, our support team can be reached
between the hours of 8:30 A.M. and 5:00 PM, Pacific Time (PST),
Monday through Friday. A voicemail can be left at any time and our
support team will return your call during business hours.
Wyatt Technical Support also offers remote support with an easy
transition from a support phone call or e-mail to a screen sharing session
via an internet connection for remote assistance with data acquisition and
processing, instrument communication, and application support.

Sales Support
For general inquiries, please contact info@wyatt.com or call +1 (805) 681-
9009. For information about purchasing additional instruments or
accessories to aid your light scattering measurements, you can contact
Wyatt Technology Corporation Sales or visit us online at
https://www.wyatt.com/products.html. You can purchase parts,
accessories, and columns at https://store.wyatt.com/.

Sales Phone: (805) 681-9009

Sales email: sales@wyatt.com

Optilab and microOptilab User’s Guide (M1520 Rev. A) 10

1 About the Optilab and microOptilab

This chapter provides a general introduction to the Optilab® and

microOptilab™ instruments and an overview of the sections in this
manual.
CONTENTS PAGE
Introduction to Optilab and microOptilab............................................................ 11
Using This Manual ............................................................................................. 12

Introduction to Optilab and microOptilab

The Optilab and microOptilab instruments are deflection-based
refractometers. They use an array of light sensitive detectors in the
measurement of differential refractive index (dRI), which is the difference
in refractive index between a sample fluid and a reference fluid.
Both instruments have a linear array of 512 photodiodes, rather than the
traditional two photodiodes used by other deflection-based instruments.
This photodiode array allows for unprecedented sensitivity and range.

With most RI instruments, users choose a gain setting, which essentially

means choosing between good sensitivity over a limited range, reduced
sensitivity over a large range, or some compromise. The Optilab and
microOptilab have no gain settings; maximum sensitivity exists over the
entire range. Tiny signals and huge signals may be measured in the same
data run. The ability to see both large and small signals may be quantified

Optilab and microOptilab User’s Guide (M1520 Rev. A) 11

Chapter 1: About the Optilab and microOptilab Using This Manual

by the instrument’s dynamic range (defined as range divided by noise).

The dynamic range of the Optilab and microOptilab is 6.27 million, orders
of magnitude greater than any other RI instrument on the market today.
In addition to the photodiode array, the Optilab and microOptilab contain
a flow cell design that allows the measurement of a fluid’s absolute
Refractive Index (aRI) in addition to the dRI between two fluids. The aRI
of a fluid is vital for characterizing a system and is a necessary input
parameter for light scattering measurements that determine the molar
mass of molecules in solution.
The Optilab is optimized for HPLC and batch applications, and the
microOptilab is optimized for UHPLC applications. As compared to the
Optilab, the microOptilab has reduced band broadening. (Refer to
Appendix C, Optilab Specifications for details.) The microOptilab has
smaller ID tubing from the input bulkhead union to the flow cell, which
increases back pressure on “upstream” instruments. Aside from these
performance and application differences, the Optilab and microOptilab
have identical interfaces and operation instructions.
This guide describes the components of the Optilab and microOptilab
refractomers, and how to set up and use the detector in both standalone
batch and online modes.

Using This Manual

This manual describes doth the Optilab and microOptilab. When a
discussion applies to both instruments, the instruments are referred to as
Optilab/microOptilab, otherwise the specific instrument is referenced.
The organization of this manual is as follows:
• Chapter 1, About the Optilab and microOptilab—Introduces the
Optilab/microOptilab and this manual.
• Chapter 2, Instrument Description—Describes the instruments’
control interfaces and connections.
• Chapter 3, Quick Start—Contains a summary of instructions for
setting up the instruments quickly and with minimal instruction.
• Chapter 4, Installation and Setup—Provides detailed connection
information for installation and setup.
• Chapter 5, Using the Front Panel Display—Provides detailed
information on how to use the front panel display to control, configure,
and monitor the Optilab/microOptilab.
• Chapter 6, Off-Line Measurements—Describes how to make static
measurements with the instruments, including calibration, off-line
dn/dc, and absolute refractive index measurements.
• Chapter 7, In-Line HPLC Detection—Describes using the Optilab/
microOptilab as in-line concentration-sensitive detectors for HPLC
and UHPLC.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 12

Chapter 1: About the Optilab and microOptilab Using This Manual

• Chapter 8, Service and Maintenance—Provides maintenance and

service instructions.
• Chapter 9, Troubleshooting—Provides troubleshooting tips.
• Appendix A, Acronyms and Abbreviations List—Contains a list of
acronyms and abbreviations used in this manual.
• Appendix B, Operating Principles and Theory—Provides a basic and
theoretical description of how the Optilab/microOptilab operate.
• Appendix C, Optilab Specifications—Provides the specifications of the
Optilab/microOptilab.
• Appendix D, Wetted Materials/Cell Properties
• Appendix E, Instrument Connectivity—Provides details about
connecting the instruments to a computer.
• Appendix F, Warnings—Lists warnings to be aware of when using the
Optilab/microOptilab.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 13

2 Instrument Description

This chapter provides an overview of the Optilab/microOptilab features.

CONTENTS PAGE
Overview ............................................................................................................ 14
Front Panel......................................................................................................... 15
Rear Panel ......................................................................................................... 16

Overview
The Optilab/microOptilab measures the differential refractive index (dRI)
between the current liquid sample stream and a liquid (usually neat
solvent) previously stored as a reference. The dRI is measured at a fixed
wavelength determined by a Light Emitting Diode (LED)/fiber light
source. The light source consists of a high-powered LED coupled to a
special optical fiber. This “pigtail” configuration allows you to easily
replace the light source. If you want to change the measurement
wavelength, installing a “pigtail” with a different wavelength
accomplishes this.
The dRI data can be read from the front panel display, the analog output
channel, or digitally through the Ethernet port. Since the dRI of liquids
depends critically on temperature, the instrument has a system that
precisely regulates the temperature of both the flow cell and the optics.
In addition to the dRI between two liquids, with the same liquid present in
the sample and reference chambers, the Optilab/microOptilab measures
the absolute refractive index (aRI) of that liquid.
For a more detailed theoretical description, see Operating Principles and
Theory on page 90.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 14

Chapter 2: Instrument Description Front Panel

Front Panel
The front panel, see Figure 2-1, provides fluid connections for the Optilab/
microOptilab and all of the necessary functions and displays for operating
the instrument and monitoring data.

In/Out Fluid Multi-Touch On/Off

Connectors Display Switch

Figure 2-1: Front panel

Multi-Touch Display—The display allows you to monitor, control, and

configure the Optilab/microOptilab. Chapter 5, Using the Front Panel
Display describes the use of the front panel display. The display is a
touchscreen, and the various front panel features may be accessed
directly.
IN/OUT Fluid Connections: Fluid comes into the Optilab/microOptilab
through the IN port, and exits through the OUT port. The Optilab/
microOptilab should be connected last in line if other detectors are
connected in series.

Note: The fittings used by Wyatt instruments are standard 10-32

chromatography fittings as supplied by Parker, Upchurch, or Valco.
Fittings supplied by Waters Corporation will seal but may cause a gap
within the fitting, giving rise to excessive mixing. Waters fittings are not
recommended.

Liquid Leak Port: The liquid leak port on the bottom of the instrument
provides an exit for any liquid that leaks from internal or external fittings.
When a liquid leak occurs, an internal liquid sensor activates an alarm
shown on the front panel display (see Alarm Section on page 41), and
activates an Alarm Out signal that may be used to shut off a pump.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 15

Chapter 2: Instrument Description Rear Panel

The Wyatt instrument stack is designed to direct leaks toward the bottom
instrument of the stack, where a drain connector can be installed to direct
leaks to a waste reservoir. An adapter and Versilon® tubing are provided
in the hardware kit to direct any fluid to a waste bottle. For more
information, see Attaching the Drain Port Connector on page 30.
Follow the instructions for cleaning after a fluid leak in the service and
maintenance section of this manual. See Leak Sensors and Cleaning After
a Fluid Leak on page 80.
On/Off Switch: The instrument has a front-facing on/off power button.
When the instrument is powered on, the button is illuminated. Pressing
the switch while off powers on the instrument. Pressing the switch while
on opens a confirmation window for turning off the instrument. Pressing
and holding the power button forces the instrument to shut down.

Rear Panel
The rear panel, see Figure 2-2, provides access for power, signal
connections, the cooling fan, air filter, the exhaust fan, and a purge port.
Signal Connectors Air Intake Fan Air Exhaust Fan USB

Ethernet Dry Gas Purge Port Fuse Power

Holder Connector

Figure 2-2: Rear panel

Air Intake and Exhaust Fans: The fans help to keep the instrument
electronics at a constant temperature.
Signal Connectors: There are 10 RJ-12 connectors that provide
connections to Transistor-Transistor Logic (TTL) inputs and outputs,
Analog input and output, Auto Inject input and output, and a solenoid
drive output. For a description of the signal connectors, see Power and
Signal Connections on page 23.

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Chapter 2: Instrument Description Rear Panel

Power Connector: Provides power to the instrument. See Power and

Signal Connections on page 23 for a complete description of the Optilab/
microOptilab power requirements.
Communications Connector: The Ethernet connector allows you to
connect to a computer or an Ethernet network.
Accessory In USB port: This port is reserved for future use and is
intended to be used to connect an optional USB accessory.
Dry Gas Purge Port: Provides the connection to purge the instrument
with dry air or nitrogen in order to prevent condensation on the optical
and measurement systems. For detailed information regarding the purge
port, see Dry Gas Connection on page 29.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 17

3 Quick Start

This chapter provides basic setup procedures for first-time or experienced

users who want to start the Optilab/microOptilab installation process
before reading the entire manual.
Detailed descriptions and important use instructions concerning the
Optilab/microOptilab are provided in the chapters that follow.
CONTENTS PAGE
Setting Up the Optilab/microOptilab................................................................... 19

Optilab and microOptilab User’s Guide (M1520 Rev. A) 18

Chapter 3: Quick Start Setting Up the Optilab/microOptilab

Setting Up the Optilab/microOptilab

This section describes basic setup procedures for those who want to begin
using the Optilab/microOptilab as soon as possible.
More details about setting up the Optilab/microOptilab are provided in
Installation and Setup on page 21. You may notice that the setup
procedure in this chapter differs from that in Chapter 4. The procedure in
this chapter allows you to begin stabilizing the temperature earlier in the
setup process.
See Instrument Description on page 14 for descriptions of the front and
rear panel controls and connections.
For instructions on using the front panel, see Using the Multi-Touch
Controls on page 34.

Note: The Optilab/microOptilab can be safely stacked above or below other

Wyatt instruments. To keep the instruments electronics cool, allow a
minimum of 10 cm (4 in) of open space on all sides and a minimum of 15
cm (6 in) of open space at the back panel.

1. Connect the power cable. The power outlet is located on the

Optilab/microOptilab rear panel (see Figure 2-2). The power supply is
universal, for immediate use with 100 V to 120 V or 220 V to 240 V
power at 50 Hz to 60 Hz. (See also Power and Signal Connections on
page 23.)
2. Power ON the Optilab/microOptilab. Time to full warm-up is
approximately 30 min. (See also Power On and Warm Up on page 30.)
3. Set temperature. The Optilab/microOptilab default temperature is
25 °C, with a range of 4 °C to 65 °C. If you are operating below 25 °C, it
is important that you see Dry Gas Connection on page 29 before
cooling the instrument.
4. Make fluid connections. Standard HPLC fittings: 1/16 in. OD
tubing, 10-32 threads. The Optilab/microOptilab should be connected
last in line if other detectors are to be connected in series. (See also
Fluid Connections on page 28.) The IN and OUT ports are located
behind a door on the front panel (see Figure 2-1). Tubing sizes are as
follows:
• Inlet tubing for microOptilab is 0.005 in. (0.127 mm) ID.
• Inlet tubing for Optilab is 0.010 in. (0.254 mm) ID.
• Outlet tubing for both instruments is 0.030 in. (0.762 mm) or
larger ID.
5. Flush the Optilab/microOptilab in purge mode. Use 20 mL of co-
miscible solvents stepwise as necessary to prepare the cell for data
collection. The Optilab/microOptilab is compatible with most common
mobile phases between pH 1 and pH 10. Refer to Wetted Materials/

Optilab and microOptilab User’s Guide (M1520 Rev. A) 19

Chapter 3: Quick Start Setting Up the Optilab/microOptilab

Cell Properties on page 98 for acceptable pH range. (See also Purging

the Optilab/microOptilab on page 31.) Turn the Purge On/Off by
toggling it on the front panel Dashboard tab.
The Optilab/microOptilab is shipped with Ethanol in the flow cell. A
typical series of solvents (from polar to non-polar) is shown below. Salt
solutions should be considered separate steps from pure solvents.

Water
Methanol, Ethanol
Isopropanol, Acetone
Tetrahydrofuran
Ethylacetate, Chloroform, Methylene chloride
Toluene, Carbon disulfide
Hexane, Petroleum ether
6. Zero the instrument. On the front panel go to the Graph tab and
zero the instrument by tapping the Zero dRI button.
7. Install software.
a. For in-line use with chromatography, install ASTRA and/or equiv-
alent chromatography software. See the appropriate software
manual for installation instructions.
b. For off-line use (for example, dn/dc determinations), install
ASTRA software. See the appropriate software manual for
installation instructions.

Note: This document is compatible with systems running ASTRA 7.3 or higher.
For a complete description of how to use ASTRA, please refer to the
ASTRA User's Guide.

8. Establish network communications. (See also Power and Signal

Connections on page 23.)

Optilab and microOptilab User’s Guide (M1520 Rev. A) 20

4 Installation and Setup

This chapter describes the fluid, power, and signal connections used in
setting up the Optilab/microOptilab.
CONTENTS PAGE
Installing the Instrument ..................................................................................... 21
Power and Signal Connections .......................................................................... 23
Power Connector ......................................................................................... 23
Signal Connectors........................................................................................ 23
Communication Connectors......................................................................... 27
Fluid Connections .............................................................................................. 28
Dry Gas Connection........................................................................................... 29
Attaching the Drain Port Connector ................................................................... 30
Power On and Warm Up .................................................................................... 30
Purging the Optilab/microOptilab ....................................................................... 31
Instrument Stability Check ................................................................................. 32

Installing the Instrument

The installation procedure for the Optilab/microOptilab involves some
initial tests to see that everything is working properly.
To install the Optilab/microOptilab, do the following:
1. Place the instrument on a flat, clean surface, standing on its feet and
positioned to allow air flow through the back panel. To keep the
instruments electronics cool, allow a minimum of 10 cm (4 in) of open
space on all sides and a minimum of 15 cm (6 in) of open space at the
back panel.
The Optilab/microOptilab is designed to stack with other Wyatt
detectors (for example, DAWN® and ViscoStar®). It can be installed
either at the top or bottom of the stack, but it must be the last
instrument in the flow path.
2. Make sure the supplied power plug is correct for the local power outlet.
The Optilab/microOptilab is equipped with a universal power supply,
which operates anywhere in the world. It accepts inlet voltages
between 90 V to 250 V and line frequencies from 50 Hz to 60 Hz.
3. Connect one end of the supplied Ethernet cable to the Ethernet port on
the back of the Optilab/microOptilab and the other end to your local
area network. Alternatively, you can use the supplied Ethernet-to-
USB converter and connect to the USB port on the host computer.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 21

Chapter 4: Installation and Setup Installing the Instrument

When the Optilab/microOptilab is on the local area network, it may be

accessed and controlled from any machine on the network. When using
the USB converter, it can be accessed only by the host computer. See
Instrument Connectivity on page 100 for more details about
implications for network security from the two different
configurations.
4. Switch on the instrument and let it warm up for 30 minutes before
proceeding. The power switch is on the front panel.

Note: The LED in the Optilab/microOptilab is software controlled and can be

turned on and off from the front panel display Dashboard tab.

5. When you have confirmed that the instrument is in good working

order, connect the Optilab/microOptilab to any other devices for your
application. (Auxiliary cable connection is described in the next
section.)
The ASTRA User’s Guide describes how to connect the Optilab/
microOptilab to your chromatography system.

Solvent reservoir

Pump
DAWN®

Degasser

ViscoStar®
(optional)
Column(s)

Autosampler

Optilab®
UV Detector
(optional)

An optional Orbit™ solvent recycler may be plumbed after the last instrument in the chain.

Figure 4-1: The Optilab/microOptilab in-line with a chromatography system.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 22

Chapter 4: Installation and Setup Power and Signal Connections

Power and Signal Connections

All power and signal connections to the Optilab/microOptilab are made
using the interfaces on the rear panel of the instrument. Refer to Figure 4-
2 to view the connectors on the rear panel of the Optilab/microOptilab.

Figure 4-2: Rear panel signal connections

Power Connector
The power input accepts 100 Vac to 250 Vac at 50 Hz to 60 Hz. The power
input module contains two fuses, each rated at 4 A (one for the line voltage
in, and the other for the line voltage return).

Signal Connectors
The instrument rear panel contains 10 RJ-12 connectors for TTL inputs
and outputs, analog input and output, auto inject input and output, and a
solenoid drive output.
Cables not supplied by Wyatt Technology may use a different color code
scheme or have a different correspondence between color and pin number.
If you are using non-Wyatt Technology supplied cables, refer to Figure 4-3
and Table 4-1 to determine the correct pin number and wire usage. We
recommend using only cables supplied by Wyatt Technology; wiring the
connection incorrectly could damage your instrument.
Pinouts for the RJ-12 connectors used in Wyatt Technology-supplied
cables are shown in Figure 4-3.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 23

Chapter 4: Installation and Setup Power and Signal Connections

Pin Wire Color

1 White
2 Black
3 Red
4 Green
5 Yellow
6 Blue

Figure 4-3: RJ-12 Connector and Pinouts

Several general-purpose cables are supplied for TTL inputs and outputs,
analog inputs and outputs, auto inject input and output, and solenoid
drive output.

Figure 4-4: General-purpose cable

See Table 4-1 for RJ-12 connector signal information when you connect
your Optilab/microOptilab to other instruments.
Table 4-1: RJ-12 Signal Function

Optilab/ RJ-12 Connector Wire Signal

microOptilab
Connector
White Black Red Green Yellow Blue
Zero In Signal Signal
Ground
Purge In Signal Signal
Ground
Recycle In Signal Signal
Ground
Alarm In Signal Signal
Ground
Auto Inject In Signal Signal
Ground
Analog In Positive Negative Ground

Optilab and microOptilab User’s Guide (M1520 Rev. A) 24

Chapter 4: Installation and Setup Power and Signal Connections

Table 4-1: RJ-12 Signal Function (Continued)

Optilab/ RJ-12 Connector Wire Signal

microOptilab
Connector
White Black Red Green Yellow Blue
Analog Out Positive Negative Ground
Recycle Out Signal Signal
Ground
Alarm Out Signal Signal
Ground
Auto Inject Out Contact Contact

The Zero In, Purge In, Recycle In, Alarm In, and Alarm Out signals all
follow the TTL voltage convention. In the TTL convention, 5 V on the
signal line is interpreted as a High signal, and 0 V on the signal line is
interpreted as a Low signal. Input signals to the Optilab/microOptilab
must have a duration of at least 100 ms in order to be reliably detected.
Zero In—TTL input on red (signal) and green (signal ground). When the
signal on this line transitions from 0 V to 5 V, the last measured value of
dRI is considered to be zero value, and is subtracted from the dRI data
before it is output. This is exactly equivalent to activating the Zero dRI
button on the front panel display Graph tab (see Graph Tab on page 39).
Purge In—TTL input on red (signal) and green (signal ground). When the
signal on this line transitions from 0 V to 5 V, the internal purge valve is
actuated, purging the reference chamber. While the signal on this line is
held at 5 V, the purge valve remains actuated. When the signal on this
line transitions from 5 V to 0 V, the purge valve is de-actuated. This is
exactly equivalent to activating the Purge toggle on the front panel
display Settings tab (see Settings Tab on page 44).
Recycle In—TTL input on red (signal) and green (signal ground). When
the signal on this line transitions from 0 V to 5 V, the instrument actuates
an external solenoid valve by supplying power to the Recycle Out
connector.
Alarm In—TTL input on red (signal) and green (signal ground). On the
front panel display Settings tab (see Alarm Settings on page 49), you may
select the active state of this input. If you select “Active High”, the
instrument considers a transition on this line from 0 V to 5 V to be an
Alarm In event. If you select “Active Low”, the instrument considers an
Alarm In event to occur when the signal on this line transitions from 5 V
to 0 V. When an Alarm In event occurs, the Alarm signal flashes on the
front panel display, and an Alarm Out signal is transmitted (see Alarm
Out).
Auto Inject In—TTL input or contact closure input between wires red
(TTL signal) and green (TTL signal ground). The red signal line is
internally held at 5 V. When the red signal line is brought to 0 V, the
instrument receives an Auto Inject signal. The signal line may be brought

Optilab and microOptilab User’s Guide (M1520 Rev. A) 25

Chapter 4: Installation and Setup Power and Signal Connections

to 0 V by simply connecting the red and green wires together (hence the
term contact closure). Most auto injectors supply a contact closure signal,
which simply brings the two wires into contact with each other.
In general, the same auto injector contact closure signal cannot be sent to
multiple instruments, since different instruments may be trying to
maintain different internal voltages to sense the contact closure, and the
instruments could be in conflict with each other.
The Optilab/microOptilab provides an Auto Inject Out signal that simply
retransmits the Auto Inject In signal as a contact closure output (see Auto
Inject Out), allowing you to bring an auto injector contact closure signal to
the Optilab/microOptilab, and then send the signal to another device. The
receipt of this signal by the Optilab/microOptilab causes a mark to appear
in the data on the front panel display Graph tab, changes the state
reported on the History tab, and causes a signal to be sent with the
digital data stream indicating the time of receipt of the signal.
Analog In—Analog input Positive on red, Negative on green, and Ground
on blue. The Optilab/microOptilab digitizes an analog input in the range of
±10 V with a resolution of 0.31 mV (16 bit).
Analog Out—Analog output Positive on white, Negative on black, and
Ground on yellow. The Optilab/microOptilab supplies a default analog
output in the range of ±1 V with a resolution of 0.031 mV (16 bit). In the
Constants dialog, you may set the instrument output voltage range to
include values up to ±10V. If a custom output voltage greater than 1 V or
less than –1 V is selected, then the resolution of the instrument decreases
(0.31 mV at ±10V). In the same dialog, you may set the dRI range to be
presented over that voltage range, which determines the analog out
calibration constant in Refractive Index Units per Volt (RIU/V).
Recycle Out—The solenoid valve drives current on the white and black
wires (the current direction is irrelevant for the solenoid). This signal may
be connected to a user-supplied solenoid valve or a Wyatt Technology
Recycle unit, which contains an internal solenoid valve that switches
between waste and recycle. When this connector is actuated via the
Dashboard tab (see ORBIT Control on page 38) or the Recycle In input,
the connector supplies current to drive a 12 V solenoid valve. The valve is
actuated with 12 V (up to 1 A, depending upon resistance of the solenoid),
held for 0.1 s, and then dropped down with 12 V across an internal 51 Ω
resistor.
Alarm Out—TTL output on white (signal) and black (signal ground). On
the front panel display Settings tab (see Alarm Settings on page 49), you
may select the active state of this output. If “Active High” is selected, the
instrument keeps this signal at 0 V for no alarm state, and brings the
signal to 5 V in the event of an alarm state. If “Active Low” is selected, the
instrument keeps this signal at 5 V for no alarm state, and brings the
signal to 0 V in the event of an alarm state. In this context, an alarm state
occurs if the internal liquid leak sensor detects liquid, or the internal
vapor alarm detects organic solvent vapors, or the rear panel connector
Alarm In signal is active (see Alarm In).

Optilab and microOptilab User’s Guide (M1520 Rev. A) 26

Chapter 4: Installation and Setup Power and Signal Connections

Auto Inject Out—Contact closure output between wires white and black.
This signal is a retransmit of Auto Inject In (see Auto Inject In). Internal
to the instrument, the white and black wires are normally not in contact
with one another. Upon actuation of this contact closure retransmit, the
white and black wires are brought into contact with each other inside the
instrument.

Communication Connectors
The rear panel has one Ethernet connector, allowing digital
communication to an external computer.
Ethernet—Standard Ethernet cable for connecting the instrument to an
Ethernet network, see Figure 4-5.

Figure 4-5: Ethernet cable

Detailed instrument digital connectivity instructions are given in

Instrument Connectivity on page 100.
Accessory In USB port—This port is reserved for future use and is
intended to be used to connect an optional USB accessory.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 27

Chapter 4: Installation and Setup Fluid Connections

Fluid Connections
Fluid connection tubing sizes are as follows:
• Inlet tubing for microOptilab is 0.005 in. (0.127 mm) ID.
• Inlet tubing for Optilab is 0.010 in. (0.254 mm) ID.
• Outlet tubing for both instruments is 0.030 in. (0.762 mm) or
larger ID.
The Optilab/microOptilab accepts standard HPLC fittings: 1/16 in. outer
diameter tubing with 10-32 threads.

Note: The Optilab/microOptilab should be connected last in line if other

detectors are connected in series.

The reasons for connecting the Optilab/microOptilab last in line are:

• The seals on the quartz flow cell inside the Optilab/microOptilab can
withstand fluid pressures up to 100 psi (7 bar). However, the solenoid
valve inside the Optilab/microOptilab will no longer function properly,
and may leak, with fluid pressures above 30 psi (2 bar). The back
pressure generated by some instruments can exceed 30 psi or even 100
psi with only moderate flow rates, and so the Optilab/microOptilab
may be damaged if it is placed upstream of another instrument.
• Pressure fluctuations, such as result from pump pulses, cause
measurable changes in a fluid’s refractive index. With the Optilab/
microOptilab plumbed upstream of another detector, any pump
pressure pulses are magnified due to the backpressure from the
downstream instrument, causing a larger pump pulse signal in the
data stream from the Optilab/microOptilab.
• The Optilab contains internally 0.010 in. (0.254 mm) ID stainless steel
tubing from the IN port to the input to the flow cell. The microOptilab
contains internally 0.005 in. (0.127 mm) ID stainless steel tubing from
the IN port to the input to the flow cell. Both instruments contain
0.030 in. (0.762 mm) ID tubing from the outlet from the flow cell to the
OUT port. The large diameter tubing from the flow cell to the OUT
port is intended to give the best possible pressure reference to
atmospheric pressure for the reasons discussed in the previous item.
However, large diameter tubing causes a great deal of mixing of the
sample, resulting in band broadening for any instrument placed
downstream of the Optilab/microOptilab. Large ID outlet tubing does
not effect the broadening between an instrument upstream of the
Optilab/microOptilab and the Optilab/microOptilab itself.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 28

Chapter 4: Installation and Setup Dry Gas Connection

Dry Gas Connection

If operating below ambient temperature, a dry gas purge is essential
to prevent condensation on the optical and measurement systems.
To prevent condensation, attach a dry air or nitrogen line to the Dry Gas
Purge fitting on the rear panel of the Optilab/microOptilab (see Figure 2-
2). Use the dry gas external connector (Wyatt p/n 161049, provided with
the Optilab/microOptilab) to connect to the dry gas purge on the back of
the instrument.

Figure 4-6: The dry gas external connector (Wyatt p/n 161049) ships with your Optilab/microOptilab.

The pressure in the dry air or nitrogen line should be 20 psi to 80 psi
(0.14 MPa to 0.55 MPa). With a pressure of 25 psi, the dry gas flows into
the temperature regulated box at a rate of approximately 38 mL/min. A
standard high pressure gas tank containing 8,600 L of gas at STP, should
supply a single Optilab/microOptilab for approximately 150 days.
For additional information regarding safe operation of Wyatt instruments
at sub-ambient temperatures, see TN9001: Operating Wyatt Instruments
in a Cold Room and TN9006: Preventing Condensation in Wyatt
Detectors.
The Optilab/microOptilab has an internal pressure sensor that measures
the pressure of the dry gas being supplied. The measured dry gas pressure
is viewable as a trace on the Graphs tab of the front panel display.
If the dry gas pressure drops below 20 psi (0.14 MPa), then the
temperature control set point cannot be set below 20.5 °C. If the system
temperature is set below 20 °C and the dry gas pressure subsequently
drops below 20 psi (for example, if a nitrogen tank is depleted), the
temperature control set point is automatically changed to 20.5 °C. A
warning will appear in the History tab on the front panel if the
temperature is automatically changed due to low dry gas pressure.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 29

Chapter 4: Installation and Setup Attaching the Drain Port Connector

Attaching the Drain Port Connector

If the Optilab/microOptilab is the instrument at the bottom of a
stack of instruments, tubing needs to be connected to the drain port on
the underside of the instrument to direct liquid originating within the
Optilab/microOptilab or cascading from an instrument further up to a
waste container.
The Wyatt instrument stack is designed
to direct leaks toward the bottom
instrument of the stack, where a drain
connector can be installed to direct leaks
to a waste reservoir. An elbow drain
(Wyatt p/n 165397) is included in your
hardware kit.
This drain is made of acetal and can be
connected to supplied tubing made of
Versilon®.

Note: The Wyatt-supplied leak drain plumbing contains Versilon and acetal
components. These are suitable for most solvents. If your mobile phase is
incompatible with these materials, please contact Wyatt Customer
Support for help in selecting a suitable alternative.

To install the elbow drain connector:

1. You may connect the Versilon tubing to the elbow drain connector.
2. Press the elbow drain connector firmly into place on the underside of
the instrument to secure it to the underside of the instrument.
3. Your instrument comes with a loop clamp on the
underside of the instrument for guiding the
tubing so that the instrument feet do not crush
the tubing. Connect the tubing to the connector
shown above. Use the loop to guide the tubing to
a nearby waste reservoir.

Power On and Warm Up

The power switch for the Optilab/microOptilab is located on the front of
the instrument in the lower right hand corner (see Figure 2-1). Start by
powering on the instrument using this switch.
After powering on, set the temperature control set point on the front panel
display Dashboard tab by pressing the blue Set button. The Optilab/
microOptilab has a temperature range from 4 °C to 65 °C. Subambient
temperature operations require the flow of dry gas into the temperature
controlled environment, as described in Dry Gas Connection on page 29.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 30

Chapter 4: Installation and Setup Purging the Optilab/microOptilab

After setting the temperature control set point, wait approximately

30 minutes for the instrument to stabilize. If the temperature set point is
quite different from room temperature, the instrument stability continues
to improve for several hours. Flushing the instrument, as described in
Purging the Optilab/microOptilab on page 31, may be performed during
this warm up period.
If the front panel display hangs (freezes) or crashes, see Microsoft
Windows Encounters Problems on page 88 for information about
rebooting.

Purging the Optilab/microOptilab

Turn the Purge on by toggling it on the front panel Dashboard tab.
If the purge valve is enabled, the System Health indicator turns orange
and an orange dot appears next to purge indicating that the instrument is
purging and is not ready for data collection. If the purge valve is disabled,
the orange dot disappears indicating that the purge is in the appropriate
position for collection.
With the purge valve disabled, liquid flows from the IN port, through the
flow cell sample chamber, and then through the OUT port, bypassing the
flow cell reference chamber.
If the purge valve is enabled, then liquid flows from the IN port, through
the flow cell sample chamber, through the flow cell reference chamber,
and finally to the OUT port, flushing liquid through both the sample and
reference chambers.
Flush the Optilab/microOptilab in purge mode with 20 mL of co-miscible
solvents stepwise as necessary to prepare the cell for data collection. In
addition, toggle the purge valve several times to remove any of the
previous solvent. The Optilab/microOptilab is compatible with most
common mobile phases between pH1 and pH 10. Refer to Wetted
Materials/Cell Properties on page 98 for acceptable pH range. The
Optilab/microOptilab is shipped with Ethanol in the flow cell.
A typical series of solvents (from polar to non-polar) is shown below.
Water
Methanol, Ethanol
Isopropanol, Acetone
Tetrahydrofuran
Ethylacetate, Chloroform, Methylene chloride
Toluene, Carbon disulfide
Hexane, Petroleum ether

Note: Salt solutions should be considered separate steps from pure solvents.

When the solvent required for data collection has been thoroughly flushed
through both the sample and reference chambers, disable the purge valve.
The fluid in the reference chamber is now captive, and the refractive index

Optilab and microOptilab User’s Guide (M1520 Rev. A) 31

Chapter 4: Installation and Setup Instrument Stability Check

difference between this captive reference fluid and the fluid stream
directed through the sample chamber is reported as the differential
refractive index (dRI). Tap the Zero aRI button on the front panel display
to set the current state as the “zero” differential refractive index.

Instrument Stability Check

To perform an instrument stability check, do the following:
1. Purge the Optilab/microOptilab as described in Purging the Optilab/
microOptilab on page 31.
2. Un-plumb the instrument from any fluid lines.
3. Insert a plug (shipped with the Optilab/microOptilab) into the OUT
port (see Figure 2-1) and leave the IN port open to the atmosphere.
4. On the front panel display Dashboard tab, set the temperature to
25 °C and wait approximately 30 minutes for the instrument to
stabilize. The instrument stability continues to improve for several
hours after the temperature set point has been changed. (See
Temperature Control on page 39.)
5. In the Settings tab, open the Instrument Information section. Tap
Set next to the Collection interval and set it to 2.0 s, which is
equivalent to a 4-second time constant. (See Instrument Information
Settings on page 45.)
6. In the Graph tab view the dRI trace through time. (See Graph Tab on
page 39.)
Short term noise should be seen to be less than ±7.5 x 10–10 RIU, when
measured as per ASTM-E1303-95 (2000) using a 2-second Collection
interval (equivalent to a 4-second time constant).

Optilab and microOptilab User’s Guide (M1520 Rev. A) 32

5 Using the Front Panel Display

This section describes the multi-touch controls and display interface on

the front panel of the instrument. This interface and its options allow you
to monitor, configure, and control the function and operation of the
Optilab/microOptilab.
CONTENTS
Using the Multi-Touch Controls .......................................................................... 34
Front Panel Overview......................................................................................... 34
Dashboard Tab ................................................................................................... 35
Graph Tab .......................................................................................................... 39
History Tab ......................................................................................................... 41
Settings Tab ....................................................................................................... 44

Optilab and microOptilab User’s Guide (M1520 Rev. A) 33

Chapter 5: Using the Front Panel Display Using the Multi-Touch Controls

Using the Multi-Touch Controls

You can tap, swipe, pinch, and spread your fingers to perform useful
actions on the screen.
Tap to click
Tap with one finger to select an interface option. You can tap
to view drop-down lists and tap to select commands such as
OK or Cancel.

Slide to scroll
Press and drag with one finger on the screen to scroll through
the interface. Press and slide up to scroll down through the
Settings tab, or press and slide left to scroll right through
the Status Indicators on the Dashboard tab, or vice-versa.
You can also press and drag the blue scroll bar shown on the
Dashboard and Settings tabs to scroll.
Press and pinch or spread to zoom
Two fingers are needed to zoom in or out on
display graphs. Using your thumb and
pointer finger, press the display and spread
your two fingers apart to zoom in on a graph.
Place two fingers on the display and move your finger together to zoom out
on a graph.

Front Panel Overview

The top ribbon on the display provides the Dashboard, Graph, History,
and Settings tabs, an alarm indicator, and alarm mute/unmute button.

Select a tab by tapping it. A blue underline indicates which tab is

currently shown. The tabs provide real-time data, instrument control, and
setting control. These tabs are explained in the sections that follow.
A green checkmark indicates there are no warnings or
alarms. A yellow caution icon means an issue requires
attention. A red warning icon means the system is not
ready or an alarm is active. Tapping these icons provides a shortcut to the
Alarms section on the History tab (see History Tab on page 41).
The Vapor alarm and all types of Leak alarms trigger
both visual and audible alarms. To mute alarms, tap the
sound button on the top ribbon.

Note: Even if the audible alarm is turned off, the back panel alarm output will
remain active.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 34

Chapter 5: Using the Front Panel Display Dashboard Tab

Dashboard Tab
The Dashboard tab provides most of the commonly used Optilab/
microOptilab functions as well as real-time monitoring of the system.
Basic functions are located on the Dashboard while more advanced
settings, such as instrument communication settings, are provided on the
Settings tab.

Figure 5-1: Dashboard tab

System Health Indicators

The system health indicators on the Dashboard are designed to provide an
overview of the system and its suitability for data collection.
The Dashboard tab provides real-time instrument status information in
the form of Health Indicators. There are five Optilab/microOptilab
indicators: a summary indicator, noise, wander, and drift. These are
measured and updated in real-time. Tapping a Health Indicator opens a
description of the parameter and potential solutions.

Figure 5-2: System Health Indicators on the Dashboard tab

Scroll right to view all five system health indicators.

The system status indicators can be green, yellow, or red.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 35

Chapter 5: Using the Front Panel Display Dashboard Tab

• Green indicates a ready state and that the system is ready for data
collection.
• Yellow indicates a cautionary state that conditions are not ideal.
Although you can proceed with data collection, it may be recommended
that you address the system health prior to data collection.
• Red indicates a warning state that conditions are not at recommended
specifications or an alarm has occurred. Data quality may be
negatively affected. It is strongly recommended that you address the
system health prior to data collection.
To learn more about any of the health indicators, tap the circle.
This expands the circle, and you can tap the information icon to
display additional information as well as troubleshooting guidance.
See Health Indicator Settings on page 48 to control the stringency or to
disable the health indicators.
System Status
This is a live indicator of the ready state of the instrument. If the system
status indicator is yellow or red, it suggests an instrument alarm or health
indicator should be addressed.
Detector Noise
This is a live indicator of the short-term noise, measured in RIU per
minute.

Detector Wander
This is a live indicator of the long-term noise, measured in RIU per
minute.
Detector Drift
This is a live indicator of the long-term signal stability, measured in RIU
per minute.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 36

Chapter 5: Using the Front Panel Display Dashboard Tab

Collection in Progress
When data collection is in progress, the health indicators are replaced by a
system status icon to reflect collection. While data is collecting, the health
indicators will be hidden.

Dashboard Control Options

The Dashboard tab also contains commonly used controls for your
instrument.

LED Control
Toggles the LED on or off. See LED Settings on page 47 for information
about controlling the LED power.

Purge Control
Toggles the Purge on or off. When the Purge is on, the Absolute
Refractive Index (aRI) will be shown. In order to measure the aRI, the
same liquid must be present in both the sample and reference chambers.
The purge valve must be ON and both chambers should be carefully
flushed with the liquid to be measured.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 37

Chapter 5: Using the Front Panel Display Dashboard Tab

In the ON state, the purge valve purges the reference chamber. Fluid
flows from the IN port, through the flow cell sample chamber, through the
flow cell reference chamber, and finally to the OUT port.
In the OFF state, the purge valve only purges the sample chamber. Fluid
flows from the IN port, through the flow cell sample chamber, and then
through the OUT port.

ORBIT Control
The optional Wyatt Orbit or an energized solenoid valve can be controlled
via the Orbit option to direct flow to waste or recycle. The Dashboard
allows you to toggle the Wyatt Orbit (if one is connected).

This option functions only if the back panel of the Optilab/microOptilab is

connected to a 12 V solenoid valve, such as the Wyatt Orbit solvent
recycling system, which can be plumbed to divert the flow from recycle to
waste. This accessory can be controlled in ASTRA or via the front panel.
Tap the clock icon to program the Orbit to switch from Waste to
Recycle after a specified amount of time. Use the touch screen to
type in values and tap OK.

When the Orbit is directing flow to recycle, a caution icon is displayed.

During an experiment run, you can use ASTRA or the front panel display
to direct flow to either the waste reservoir or to be recycled.
You can use the Settings tab to hide the Orbit toggle for instruments not
equipped with the Orbit. See Instrument Information Settings on page 45.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 38

Chapter 5: Using the Front Panel Display Graph Tab

Temperature Control
The temperature of Optilab/microOptilab instruments can be controlled
on the front panel. An indicator specifies whether temperature has
reached the setpoint or is ramping.
Tap the Set button enables a temperature set point in °C to be modified.
The temperature is stable (green) when it is within ±0.05 °C of the set
point value for a minimum period of 15 minutes.

Graph Tab
The Graph tab shows real-time data that assists in observing experiment
progress and system performance. It also allows you to see when your
instrument has received an auto-inject signal from an autosampler or
manual injector, after which a vertical green line is displayed on the graph
as shown below.

Zero dRI Button

Tap the Zero dRI button to update the value that is stored as the light
beam position that corresponds to a zero dRI.
This button is used during instrument calibration (see Collecting Data for
Optilab/microOptilab dRI Calibration on page 56) and prior to collecting
data for in-line experiments (see Measurement on page 65).

Optilab and microOptilab User’s Guide (M1520 Rev. A) 39

Chapter 5: Using the Front Panel Display Graph Tab

Selecting the Display Axes

You can select a data channel to display in the graph for each y-axis.
The y-axis on the left corresponds to the yellow trace. The default is to
show the dRI. You can select another data channel by tapping the Y LEFT
drop-down. Other options are instrument temperature, dry gas pressure,
LED monitor, LED power, forward monitor, and the Aux input.

The y-axis on the right corresponds to the blue trace. The default is to
show the output from the Forward Monitor. You can select another data
channel by tapping the Y RIGHT drop-down.
By default, the left and right y-axes scale to fit the real-time data streams
you choose to display. In the window for selecting a display axis, you can
customize the scale by tapping the Set Scale button.

Selecting the Time Axis

The x-axis always display time, but the time scale can be set from 10 min
to 2 hours using the drop-down options for Time.
You can zoom in or out on the chart by pinching or spreading your fingers
as discussed in Using the Multi-Touch Controls on page 34.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 40

Chapter 5: Using the Front Panel Display History Tab

History Tab
The History tab displays information about the alarm status for the
Optilab/microOptilab and the history of the system. This includes alarms
from the Optilab/microOptilab instrument itself and external alarms that
are collected through the back panel.
The Vapor alarm and all types of Leak alarms trigger
both visual and audible alarms. To mute alarms, tap the
sound button on the top ribbon.

Alarm Section
The Alarm section displays current alarms. To learn more about
an alarm, tap the information icon to display additional
information.
The alarms are color-coded for severity:
• Yellow alarms are cautionary and suggest the instrument is not ready
for operation (for example, a temperature lock has not been achieved).
• Red alarms suggest a hazard or severe warning, such as an external
alarm, vapor alarm, or liquid leak.
• Blue alarms refer to an information notice, such as the purge valve
being enabled.
• Alarms that are not active are not shown, so there are no green
alarms.

All types of Leak alarms also cause audible alarms unless alarms are
muted (see Front Panel Overview on page 34).

Optilab and microOptilab User’s Guide (M1520 Rev. A) 41

Chapter 5: Using the Front Panel Display History Tab

History Section
The History section contains a list of events tracked by the
instrument. this includes the type of alarm, severity, and the date/
time of the alarm. Tap the information icon next to an alarm to
display additional information.

The following events or alarms can be recorded by the Optilab/

microOptilab:
• Device Error: Instrument error. Restart the instrument, and if the
alarm persists contact Wyatt Customer Support for assistance.
• Inject Start: An auto-inject signal was received or manual data
collection has begun.
• External: If an external alarm cable is connected to the Alarm In port
on the rear panel, the Optilab/microOptilab can receive a voltage
signal to trigger an alarm state. By default, an input signal of 0 V is
considered a ready (non-alarm) state, and an input signal of 5 V is
considered an alarm state. If Alarm In is set to Active Low (see
Alarm Settings on page 49), this is reversed—an input signal of 5 V is
considered a non-alarm state, and an input signal of 0 V is considered
an alarm state.
• Forward Monitor: Instrument forward monitor light is low. This
occurs during a solvent change or if there is a bubble or obstruction in
the flow path. Please purge the flow cell. If the problem persists,
contact Wyatt Technical Support for assistance.
• Leak: Leak detected. Check that the inlet and outlet tubing are secure
and that no spills or leaks have occurred. Clean and dry the leak
sensors, as appropriate. Please see Leak Sensors and Cleaning After a
Fluid Leak on page 80 for more information.
• LED: The LED light has turned on.
• LED Monitor: The light from the LED/fiber dropped below 70 % of its
original power. This is an indication that the LED/fiber may need to be
replaced. See Replacing the LED/Fiber Light Source on page 73 and
contact Wyatt Technical Support for further assistance.
• Low Dry Gas Pressure: Temperatures below 20 °C require at least
20 psi dry gas, such as dry air or nitrogen, to prevent condensation.
The temperature is automatically set to 20.5 °C when this alarm

Optilab and microOptilab User’s Guide (M1520 Rev. A) 42

Chapter 5: Using the Front Panel Display History Tab

occurs. This prevents condensation from damaging the optics if the

nitrogen or dry air connection is not made or if the tank runs empty.
Check your gas supply and ensure there is sufficient flow.
• Overheat: The instrument temperature exceeds the maximum limit
of 82 °C. The heather/cooler is disabled and cannot be re-enabled until
the power has been cycled off and then on. Contact Wyatt Technical
Support for assistance.
• Purge In: The instrument received a request from an external device
to actuate the purge valve (set Purge On).
• Purge: Purge enabled. Sample and reference sides of the flow cell are
being flushed.
• Recycle In: The instrument received a request from an external
device to toggle the Orbit recycle valve.
• Temp Control Error: Instrument thermometer error. Please contact
Wyatt Technical Support for assistance.
• Temperature Lock: The temperature is stabilizing. The temperature
is considered stable when it is within ±0.05 °C of the set point value for
a minimum period of 15 minutes.
• Vapor: The voltage measured from the organic vapor sensor is higher
than the threshold voltage. This triggers an audible alarm.
• Zero In: The instrument received a request from an external device to
zero the dRI signal.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 43

Chapter 5: Using the Front Panel Display Settings Tab

Settings Tab
The Settings tab provides external alarm, temperature, network,
connected user, detector noise, analog output, system control, and
instrument information. It is organized into several collapsible sections.
Tap a drop-down icon to expand the relevant section.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 44

Chapter 5: Using the Front Panel Display Settings Tab

Instrument Information Settings

Expand the Instrument Information section to see information about
the instrument and optical bench, such as serial numbers, model number,
instrument type, LED wavelength, and collection interval. The serial
number and firmware version are useful to have when contacting Wyatt
Technical Support.

You can modify the following settings:

• Wavelength. Displays the current value of the wavelength of the
LED/fiber light source, which is stored in the instrument’s on-board
memory. This value should not be changed while a light source is
connected. See Changing the Wavelength Setting on page 77 for
instructions regarding changing the wavelength.
• Collection Interval. This specifies the time between each data slice
displayed on the front panel; it is the inverse of the frequency of data
slices. The default is 0.50 seconds. The time over which data are
averaged (the measurement time constant) is automatically set to be
2x the collection interval. This interval can also be controlled by
ASTRA.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 45

Chapter 5: Using the Front Panel Display Settings Tab

• Time and Date. Set the instrument time by rotating the dials to select
the hour, minute, and whether the time is AM or PM.
• Orbit Control. You can disable display of the Orbit in the front panel
by toggling the Orbit Control. See ORBIT Control on page 38.

Network Settings
Expand the Network section to see the network name of the instrument
as it would appear on a LAN, whether the IP address should be obtained
automatically (using DHCP) or be set manually (static IP).
If you disable obtaining the IP address automatically (as shown below),
you can set the IP Address and Subnet Mask.

See Appendix E, Instrument Connectivity for instructions regarding

network communications setup.

Connected User Settings

Expand the Connected User section to see if any computers are
currently connected to the instrument via ASTRA. If a computer is
connected, this section shows the user name and the computer
name.currently controlling the instrument via ASTRA.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 46

Chapter 5: Using the Front Panel Display Settings Tab

LED Settings
Expand the LED section to see options for setting the LED/fiber light
source power.

The LED Power displays the current LED power as a percent of the
maximum.
The Optimize button automatically determines the optimal percent of
the maximum power to send to the LED/fiber light source and sets the
LED Power. After optimization, the Forward Monitor should be
93 % to 100 % for the Optilab and 85 % and 100 % for the
microOptilab. The Power should be less than 100 %.
The Set button allows you to set the power. If you are changing the
LED/fiber light source, set the LED Power to 0 %. You can use the
LED control on the Dashboard (see LED Control on page 37) to turn
the LED on and off.
The LED Monitor displays the light level from the LED fiber tip before
the light is passed through the optical system, including the flow cell. The
difference between the LED Power and LED Monitor indicates how much
the intensity of the LED/fiber decays with time.
For optimal performance, the two values should be close together. If the
LED Monitor value drops below half of the LED Power, the LED Monitor
alarm turn reds, indicating that the LED/fiber source should be replaced.
See Replacing the LED/Fiber Light Source on page 73. Set the LED Power
to zero when changing the light source. (See LED Settings on page 47.)
The Forward Monitor displays the light level from the LED fiber tip
after the light has passed through the optical system and the flow cell. The
photodetector saturates slightly above 8 V, which corresponds to 100 %
Forward Monitor value. At this point, an increase in light intensity no
longer results in an increase in the signal voltage from the photodetector.
If the light intensity is saturating the detector, the instrument firmware
automatically reduces the forward monitor to an optimal setting between
93 % and 95 % for the Optilab and 85 % and 95 % for the microOptilab.
The Forward Monitor trace can by viewed on the Graph tab.

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Chapter 5: Using the Front Panel Display Settings Tab

Instrument performance degrades significantly if the photodetector

voltage is above 8 V and very slightly if the photodetector signal drops
below the optimal value. When the forward monitor drops below 50 %, the
Forward Monitor alarm is activated.

Temperature Settings
Expand the Temperature section to see the current and set point
temperature for the instrument. The Set Point can be set here or on the
Dashboard tab.

Auto Inject Settings

Expand the Auto Inject section to see the Zero On Auto Inject toggle.
When this setting is enabled and an Auto Inject signal is received, the last
measured value of dRI is considered to be a zero value. That value is
subtracted from the dRI data before they are output.

dRI Polarity Settings

Expand the dRI Polarity section to see the Reverse dRI Polarity
toggle. Enable this option if you are working with a sample with a
negative dn/dc value so that the peaks in the dRI signal will be positive

Health Indicator Settings

Expand the Health Indicators section to see and control the noise,
wander, and drift values that trigger a health indicator. See System
Health Indicators on page 35 for information about viewing health
indicators.
The default setting is Wide, which is appropriate for a wide range of
systems. Use the Narrow preset if very low noise levels are required, for
example when working with materials with a lower signal-to-noise ratio.

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Chapter 5: Using the Front Panel Display Settings Tab

The indicator is green below the lower threshold, yellow if between the
lower and upper, and red if above the upper threshold. You can set
Custom values for the lower and upper thresholds. If you disable the
Health Indicators, they will no longer appear on the Dashboard.

Alarm Settings
Expand the Alarm section to see and control the settings for alarms based
on the Alarm In and Alarm Out ports.
Different devices have different conventions for alarm states. Some
maintain a 5 V state on a wire to indicate no alarm, and bring the voltage
to 0 V to indicate an alarm condition. This is called the “Active Low”
convention. Others use 5 V to indicate an alarm condition; this is the
“Active High” convention.

If an external alarm cable is connected to the Alarm Out port on the rear
panel, the Optilab/microOptilab can send out a voltage signal to an
external destination in the event of an alarm being triggered. In the
default configuration (Active High), the Alarm Out port is kept at 0 V
during a ready (non-alarm) state, and increases to 5 V in the event a
serious (red) alarm is triggered.
If you select Active Low, the Alarm Out port is kept at 5 V during a ready
(non-alarm) state, and decreases to 0 V in the event a serious (red) alarm
is triggered.
See Signal Connectors on page 23 and Alarm Section on page 41.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 49

Chapter 5: Using the Front Panel Display Settings Tab

For example, multiple instruments in a chromatographic system typically

have liquid leak detectors. It is desirable that the solvent pump be shut off
in the event of a liquid leak in any one of those instruments. Since the
alarm outputs from each instrument cannot all be connected to the same
pump shut-off signal line, the alarm outputs from the instruments will be
combined (logical OR) with each other. The external alarm In is combined
in a logical OR with the Optilab/microOptilab internal vapor and liquid
leak alarms, and then retransmitted as the external alarm Out.

Analog Output Settings

Expand the Analog Output section to control settings related to the
voltage outputs presented on the rear panel Analog Out connector. These
outputs can be used to transmit data channels to a third-party
instrument. (See Signal Connectors on page 23.)

Select one of the four analog connectors from the Output Channel drop-
down menu. Then select the data channel to transmit for that channel
from the Signal drop-down menu.
Select a Preset to choose whether the output range should be Standard,
Wide, Full, or Custom. The Min and Max output Voltages and dRI values
are set to preset values as in Table 5-1.
Table 5-1: dRI Analog Out Range Settings

dRI Analog Output Voltage (V) dRI (RIU) Output Slope

Out Preset (RIU/V)
Min Max Min Max

Standard –1 +1 –2 x 10–4 +2 x 10–4 2 x 10–4

Wide –1 +1 –1 x 10–3 +1 x 10–3 1 x 10–4

Full –1 +1 –4.7 x 10–3 +4.7 x 10–3 4.7 x 10–3

Custom User defined User defined User selected User selected User defined

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Chapter 5: Using the Front Panel Display Settings Tab

For example, if you set the Preset to Standard, the voltage response
from a BSA solution (dn/dc at 660 nm = 0.185 RIU/g/mL) of concentration
1 mg/mL in the flow cell will remain barely below 1 V.
If you set the Preset to Custom, you may set the Min and Max output
Voltages to any value between -10 V and +10 V. You may also set the
Output Slope.

Note: The instrument dynamic range exceeds 22-bit resolution (more than 6x106
discrete steps). The 22-bit full range and sensitivity may be
simultaneously accessed only via digital communication. The Digital/
Analog converter has 18-bit resolution (262 143 discrete steps) between
–10 V and +10 V (16-bit Digital/Analog converter with a pulse width
modulation output and low pass filtering for sub bit level resolution). The
default voltage range is set to the subset of +/-1 V for higher resolution. If
the entire dRI range is selected for analog output, the smallest observable
signal on the analog output is set by the 18-bit Digital/Analog resolution,
effectively reducing sensitivity.

Output Slope: Relates the dRI change to voltage presented on the analog
out signal. The dRI analog output slope is calculated as:
(dRIMAX – dRIMIN) / (VoltageMAX – VoltageMIN)
Typical values range from ± 1e-6 RIU/V up to ± 5e-3 RIU/V.
Output Offset: You can set an offset value to cause the range of output
values to be centered above or below zero.
Maximum Output Voltage: By default, this is +1 V.

System Constants Settings

Expand the System Constants section if you want to view or set
constants used by the instrument when performing calculations.

System constants are loaded at the factory and should be checked

periodically by running known samples. Refer to Off-Line Measurements
on page 53 for more information regarding dRI and aRI calibration.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 51

Chapter 5: Using the Front Panel Display Settings Tab

• dRI calibration constant—This value relates light beam movement

to the dRI (differential Refractive Index) measurement.
• dRI offset—This value represents the light beam position that
corresponds to zero dRI. Zeroing the instrument (from the front panel
Graph tab) updates this value.
• aRI calibration constant—This values relates light beam
movement to aRI (absolute Refractive Index).
• aRI offset—A second calibration constant associated with the aRI
measurement.

System Control Settings

Expand the System Control section if you want to reset the instrument
to its Factory Default Configuration or Restart the instrument. You
can also restart the instrument by pressing and holding the On/Off button
on the front panel.

You should restart the instrument after installing a firmware update.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 52

6 Off-Line Measurements

This chapter provides general information for instrument calibration,

sample preparation, dn/dc measurement, and aRI measurement.
CONTENTS PAGE
Instrument Calibration for dRI ............................................................................ 53
General Information and Sample Preparation ............................................. 53
HPLC Pump with Injector............................................................................. 55
Syringe Pump Infusion................................................................................. 55
Collecting Data for Optilab/microOptilab dRI Calibration ............................. 56
Instrument Calibration for aRI ............................................................................ 58
General Information ..................................................................................... 58
Collecting Data for Optilab/microOptilab aRI Calibration ............................. 59
dn/dc Measurement ........................................................................................... 61
Absolute Refractive Index Measurement ........................................................... 62

Instrument Calibration for dRI

The Optilab/microOptilab dRI measurement can be calibrated as
described in this section. This procedure is also summarized in the ASTRA
User’s Guide section on RI Calibration.

General Information and Sample Preparation

The Optilab/microOptilab dRI measurement performance should be
checked regularly against a standard with a known dn/dc value.
Changing solvents does not affect the Optilab/microOptilab calibration
constant.

Note: For use with certain chromatography systems and the ASTRA software,
the dRI calibration may be performed by injecting a suitable standard
sample and verifying that the injected and calculated masses are equal.
This option is often much more efficient than the off-line approach
described below. Contact Wyatt Technical Support and/or consult the
ASTRA User's Guide for more information.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 53

Chapter 6: Off-Line Measurements Instrument Calibration for dRI

The off-line dRI calibration may be performed using any substance with a
well-characterized dn/dc value. The recommended standard is anhydrous
sodium chloride dissolved in pure deionized water. This solution has a
dn/dc of 0.174 mL/g at a wavelength of 658 nm (0.179 mL/g at 488 nm,
0.174 mL/g at 633 nm, 0.173 mL/g at 690 nm, 0.173 mL/g at 785 nm, and
0.172 mL/g at 900 nm).1
Appropriate concentrations should be prepared using neat HPLC grade
solvents and clean glassware. The lowest and highest recommended
concentrations are ~0.1 mg/mL and ~29 mg/mL respectively, although 0.1
mg/mL to 5 mg/mL is the most relevant range for Optilab/microOptilab
dRI calibration. Use six or more concentrations prepared within 1 % or
better accuracy to increase the precision of the final determination. Wyatt
Technology provides validated, pre-mixed NaCl solutions in the ideal
concentration range for this purpose. See below for details.
The Optilab/microOptilab can differentiate between solvent that has been
saturated with ambient gases and those that have been degassed. It is
possible to detect concentration differences in the 1 ppm range.
Consequently, standard samples and solvent blanks must be prepared
from the same solvent stock. After preparing the standard solutions, fill
two or three extra containers with solvent from the same solvent stock to
use for “blank” analyses.
Samples should be kept well-sealed to prevent evaporation. Some solvents
(such as water) keep fairly well for a number of months, but concentration
changes may occur over time due to evaporation or contamination.
Single-use sodium chloride solutions are available for purchase from
Wyatt Technology Corporation. Part Number: P8400; NaCl Solutions Kit.
Concentrations: 0.0 (blank), 0.1, 0.5, 1.0, 1.2, 2.0, 3.0, 4.0, and 5.0 mg/mL
in nanopure water.

1. Becker, A., Köhler, W. and Müller, B. (1995), A Scanning Michelson Interfer-

ometer for the Measurement of the Concentration and Temperature Deriva-
tive of the Refractive Index of Liquids. Berichte der Bunsengesellschaft für
physikalische Chemie, 99: 600–608. doi: 10.1002/bbpc.19950990403

Optilab and microOptilab User’s Guide (M1520 Rev. A) 54

Chapter 6: Off-Line Measurements Instrument Calibration for dRI

HPLC Pump with Injector

This arrangement is shown in Figure 6-1.

Optilab/microOptilab
Inline filter

HPLC degasser Injector

and pump with loop
Waste
flask
Figure 6-1: Setting up an HPLC pump and injector for calibration

• For Optilab use 0.010 in. (0.254 mm) ID tubing between the injector
and the Optilab and a flow rate of 0.5 mL/min to 1.0 mL/min.
• For microOptilab use 0.005 in. (0.127 mm) ID tubing between the
injector and the microOptilab and a flow rate of 0.3 mL/min to
0.5 mL/min.
• Use 0.030 in. (0.762 mm) ID tubing elsewhere.
• Use a large sample loop, 0.5 mL to 1.0 mL to ensure that each injection
produces a clear plateau and not a peak as it passes through the
Optilab/microOptilab. The Wyatt High Pressure Injection System
accessory (WISH™) may be used.
The objective is to inject known concentrations into the detector. If a peak
with a rounded top and no clear plateau is obtained, the concentration at
the top of the peak will be unknown; flat-topped plateaus indicate that the
cell has been fully flushed with sample solution.
A syringe pump fitted with a large syringe may be used instead of the
HPLC pump.

Syringe Pump Infusion

Another option is to connect the Optilab/microOptilab as shown in Figure
6-2, using a syringe pump. Use 0.030 in. (0.762 mm) ID tubing for both
connections. A recommended flow rate is 0.1 mL to 0.2 mL/min. The
syringe must be rinsed and dried thoroughly or replaced between samples
to avoid contamination of one concentration by the next sample. When the
syringe is disconnected to change samples, the pressure change and
injected air may cause an unstable baseline for several minutes.

PEEK
Syringe
tubing
Optilab/
microOptilab

Syringe pump
Waste
flask
Figure 6-2: Setting up a syringe pump for calibration

Optilab and microOptilab User’s Guide (M1520 Rev. A) 55

Chapter 6: Off-Line Measurements Instrument Calibration for dRI

Collecting Data for Optilab/microOptilab dRI Calibration

This procedure is also summarized in the ASTRA User's Guide section on
dRI Calibration.
Data Collection
1. The sample and reference cells should be flushed with neat solvent for
several minutes before making measurements.
2. Confirm that the temperature is stable at 25 °C.
3. On the Optilab/microOptilab front panel display Dashboard tab,
toggle the Purge on. (The orange indicator next to Purge is shown
when the Purge is on.)
4. Wait until the baseline is stable, then toggle the Purge off.
5. Monitor the baseline for a few minutes to ensure it is still stable.
6. Zero the Optilab/microOptilab by tapping the Zero dRI button on the
Graph tab. After the Optilab/microOptilab has been zeroed, it is ready
to collect data and should not zeroed again until the dRI Calibration
procedure is complete.
7. Collect data using ASTRA software as follows (see the ASTRA User's
Guide for more information):
a. Start the ASTRA software and select File→New→Experiment
from Method.
b. In the dialog that opens, open the System Methods folder, then
the RI Measurement folder, and select the RI calibration
method.
c. Expand the Configuration node and verify that the proper
experimental parameters have been entered.
d. Expand the Procedures node of the method. Click the Basic
collection procedure and enter appropriate values for each field.
e. Click Apply to save your settings, and run the experiment.
8. Introduce pure solvent (blank) into the reference cell, making sure the
solvent flows through the system at a constant rate.
dRI detectors are sensitive to sudden flow changes as the detector drift
can overwhelm the signal. Thus, it is important to maintain a nearly
constant flow through the instrument while measuring solutions.
9. While ASTRA collects data, begin to introduce the series of prepared
standards into the sample cell of the detector. Introduce each standard
solution one at a time, beginning with the lowest concentration.
10. Wait for the signal to stabilize (allow the signal to reach a plateau),
which may take several minutes while the previous solution is
completely rinsed out of the cell. After all standards have been
injected, reinject a pure solvent sample (blank) to re-establish the
baseline.
11. Once a good baseline signal is acquired, stop the data collection.

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Chapter 6: Off-Line Measurements Instrument Calibration for dRI

ASTRA Calculations
The dRI Calibration calculation procedure is as follows (see the ASTRA
User's Guide for more information):
1. After the data collection has ended, ASTRA may produce a message
box informing you that some parameters necessary to perform the
calculations are missing. Click OK, and the software will expand the
Procedures section of the experiment and open the Baselines
procedure. Otherwise click the Run button to proceed.
2. In the Define baselines window, define the baseline using the
solvent blanks that were injected before and after the standard
solutions. Click and drag from one solvent plateau to the other, such
that a baseline is drawn under the sample solution plateaus. Click OK
to close the Define baselines window.
3. In the Define peaks window define a peak for each of the flat plateau
regions associated with each injected standard. Click and drag over
the maximum flat region for each sample injection. Do not set peak
regions for the “blank” injections.
4. As peak regions are defined, a table beneath the Define peaks graph
shows a new column for each peak. In these columns, for the
Refractive index, enter the known concentration for each standard in
the row titled Concentration (mg/mL). Once all the peaks have been
assigned with their respective concentrations, click the OK button at
the bottom to close the pane.
5. Open the RI Calibration procedure. Enter the known dn/dc into the
row titled Known dn/dc (mL/g) and press Enter. The value listed in
the Calibration row should update once a known value is entered.
6. Expand the Results node and double click the Report (summary)
line. The report will display the new Calibration constant.
7. Go to the Settings tab on the Optilab/microOptilab front panel display
and scroll down to System Constants. (See System Constants
Settings on page 51.) Tap the blue Set button to the right of dRI
calibration constant. In the dialog that appears, enter the new dRI
calibration constant and tap Set.

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Chapter 6: Off-Line Measurements Instrument Calibration for aRI

Instrument Calibration for aRI

The Optilab/microOptilab aRI measurement can be calibrated as
described in this section. This procedure is also summarized in the ASTRA
User’s Guide on “aRI Calibration.”
We recommend that you verify and/or calibrate the absolute Refractive
Index (aRI) measurement before operating the instrument in aRI mode for
the first time, and it is recommended that you check these values for
accuracy on a periodic basis.

General Information
Optilab/microOptilab aRI measurement performance should be checked
against one or more standards. For a complete aRI calibration, at least 3
pure solvents with known aRI values (which are specific for the operating
wavelength of the Optilab/microOptilab) should be used. See Table 6-1 for
recommendations. It is imperative that each solvent infused into the
Optilab/microOptilab must be miscible with the solvent that it replaces.
The Optilab/microOptilab aRI is factory-calibrated using the following
four solvents in the following order:
1. High Purity Water (NANOpure water with a final 0.2 micron filter)
2. Methanol (HPLC-Grade Fisher A452-4)
3. Tetrahydrofuran (GPC-Grade w/BHT Burdick & Jackson Cat. 341-4)
4. Toluene HPLC Grade (HPLC-Grade Burdick & Jackson Cat. 347-4)

Table 6-1: Known aRI Values for Various Solvents at Various Wavelengthsa
Solvent 685nm 658nm 633nm 532nm 514nm 488nm
Water 1.3303 1.3309 1.3316 1.3347 1.3354 1.3364
Methanol 1.3242 1.3247 1.3253 1.3282 1.3289 1.3300
Tetrahydrofuran 1.4015 1.4022 1.4029 1.4069 1.4079 1.4094
Toluene 1.4882 1.4896 1.4910 1.4995 1.5017 1.5053

a. As compiled in Photothermal Spectroscopy Methods for Chemical Analysis,

Wiley, 1996, with preference to thermodynamic values specified in David R.
Lide, CRC Handbook of Chemistry and Physics, 76th Ed, 1995

Note: It is imperative that each solvent be miscible with the solvent it replaces
anytime the Optilab/microOptilab is flushed with a new solvent.

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Chapter 6: Off-Line Measurements Instrument Calibration for aRI

Collecting Data for Optilab/microOptilab aRI Calibration

Collect data using the ASTRA software.
1. Start ASTRA, and select File->New->Experiment from Method.
2. In the dialog that opens, select the System Methods folder, then the
RI Measurement folder, then the Calibration folder, and finally the
absolute RI calibration method.
3. Expand the Configuration node and verify that the proper
experimental parameters have been entered.
4. Expand the Procedures node of the method. Click on the Basic
collection procedure and enter appropriate values for each of the
fields. Close the pane by clicking the OK button.
5. In the Absolute RI calibration procedure in ASTRA, copy the numbers
from the second column in the New Abs. RI Calibration and New
Abs. RI Offset rows to the first column in the Old Abs. RI
Calibration and Old Abs. RI Offset rows as indicated in the
following figure. (Because ASTRA’s calibration calculation is an
adjustment, it needs the instrument’s current pre-calibration
constants.) Click OK to close the window.

Note: You must perform this step before collecting data. You will not be able to
edit the calibration constant after collection, which would result in
incorrect new calibration constants.

6. Run the experiment.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 59

Chapter 6: Off-Line Measurements Instrument Calibration for aRI

Introduce Solvents
1. The Optilab/microOptilab should be purged (flow liquid with the Purge
on) with high-purity water for several minutes before beginning the
aRI calibration procedure. Confirm that the temperature is stable at
25°C, and operate the Optilab/microOptilab with the Purge ON for all
data collection.
2. Flow the pure solvents directly into the Optilab/microOptilab at a
constant flow rate, using a syringe pump or an HPLC pump set in the
flow rate range of 0.5mL/min to 1.0mL/min.
3. After flowing roughly 4-5 mL of solvent, toggle the purge valve to
PURGE OFF for 15 seconds, and then toggle it back to PURGE ON
for 15 seconds. Repeat this cycle for 2-3 minutes. Cycling the purge
valve in this manner creates just enough agitation in the flow path to
displace air bubbles and thoroughly remove the previous solvent.
4. On the Optilab/microOptilab front panel display Settings tab, expand
the LED heading. Next to LED Power tap Optimize. (See LED
Settings on page 47.)
5. Complete the solvent introduction process by leaving the purge valve
in the PURGE ON state for roughly one minute, and then turn the
syringe pump off. After three minutes of stopped flow the Optilab/
microOptilab is stable. During this time ASTRA will record the stable,
flat no-flow region. Note the time of this no-flow period, which will be
referenced during data processing.
6. Repeat this solvent introduction procedure (beginning with step 1 of
this list) for each remaining solvent.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 60

Chapter 6: Off-Line Measurements dn/dc Measurement

ASTRA Calculations
Follow these steps in ASTRA:
1. After data collection, open the Procedures section of the experiment,
and click Define peaks. On the graph, identify the flat no-flow
regions associated with each solvent. Define a peak for each solvent by
selecting a plateau of approximately 30 seconds located near the end of
the flat region.
2. Beneath the graph a table is shown with a column for each defined
solvent. Expand the Particles index node. A row will now be visible
titled Sphere Real RI. In each solvent’s column, enter the known aRI
value. Make sure that it is the correct aRI value for the Optilab/
microOptilab’s operating wavelength. Table 6-1 lists aRI values for
several solvents at various wavelengths. Click the OK button to close
the window.
3. Click on the Absolute RI Calibration procedure. The new aRI
calibration constant and aRI offset will automatically be
calculated.
From here it is possible to upload the new values directly to the Optilab/
microOptilab.

dn/dc Measurement
The dn/dc value is the change in solution refractive index with change in
solute concentration, expressed in units of mL/g. It is possible to calculate
dn/dc from Optilab/microOptilab data if the Optilab/microOptilab dRI
calibration constant and sample solution concentrations are known.

Note: For use with certain chromatography systems and the ASTRA software,
dn/dc calculations may be performed by injecting the unknown sample
once, and assuming that the injected and calculated masses are equal.
This option is often much more efficient than the off-line approach. For
more instructions, refer to TN4001: Online dndc Determination.

The ideal sample concentration range for dn/dc measurements will vary
depending on the dn/dc value itself. In general, a set of 5 to 6
concentrations over a range of an order of magnitude in concentration,
such as 0.1 mg/mL to 1 mg/mL, is appropriate.
Use the general procedures described in Instrument Calibration for dRI on
page 53 for sample preparation, injection, and data collection, using the
ASTRA template named Batch (determine dn/dc). You can also find
step-by-step instructions in TN4000: Batch dndc Measurements.
After data collection define a peak for each of the flat plateau regions
associated with each injected sample solution, in the Define peaks
window. Click and drag over the maximum flat region for each sample
injection. Do not set peak regions for the “blank” injections.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 61

Chapter 6: Off-Line Measurements Absolute Refractive Index Measurement

As peak regions are defined, a table beneath the Define peaks graph
shows a new column for each respective. In these columns, under the
Refractive index node, enter the known concentration for each sample
solution in the row titled Concentration (mg/mL). Once all the peaks
have been assigned with their respective concentrations, click the OK
button to close the window. The sample dn/dc value will be reported in
the reports available in the Results section of the Experiment tree.

Absolute Refractive Index Measurement

In order to measure the absolute refractive index (aRI) of a liquid, the
liquid must be present in both the sample and reference chambers of the
Optilab/microOptilab. The purge valve must be ON and both chambers
should be carefully flushed with the liquid to be measured.
With the Purge valve set to On, the aRI of the liquid in the flow cell can
be displayed in the Graph tab on the front panel display.
It is also possible to measure the absolute refractive index of a solvent/
solution using ASTRA:
1. Launch ASTRA and select File→New→Experiment from Method.
2. Navigate to System→Methods→RI Measurement and select
absolute RI measurement.
3. Expand the Configuration node and verify that the proper
experimental parameters have been entered.
4. Expand the Procedures node of the method.
5. Click on the Script collection procedure and run the experiment.
6. Introduce the solvent/solution of interest into the instrument, making
sure that it flows through the system at a constant rate. Optilab/
microOptilab detectors are sensitive to sudden changes in flow as the
detector drift would overwhelm the signal. Thus, it is important to
maintain a nearly constant flow through the instrument while
measuring the solutions.
7. When data acquisition is complete, process the data as for any other
ASTRA experiment. The mean aRI for the selected peak region as well
as standard deviation will be reported in the Results section.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 62

7 In-Line HPLC Detection

This chapter provides details about preparing samples for optimal in-line
operation and measurement.
CONTENTS PAGE
Conditions for In-Line Operation ........................................................................ 64
Sample Preparation ........................................................................................... 65
Measurement ..................................................................................................... 65

Optilab and microOptilab User’s Guide (M1520 Rev. A) 63

Chapter 7: In-Line HPLC Detection Conditions for In-Line Operation

Conditions for In-Line Operation

In order to use the high sensitivity Optilab/microOptilab successfully, the
following are recommended:
• Solvents should be pre-mixed and stored in a covered reservoir. For
the lowest possible baseline noise, a stirrer should be used in the
solvent flask. The solvent should be degassed by vacuum, sonication,
or boiling, and blanketed with an inert gas—such as helium or argon—
that has a low solubility in the solvent. An in-line degasser may be
used effectively. The use of two or more pumps and a mixing chamber
is not recommended since even a one part per million deviation in the
mixed solvent ratio causes large deviations in the dRI signal, and
there are no known mixing techniques that are able to maintain a one
part per million level of stability.
• Thermal control and/or insulation of the system components are
important in order to obtain good results, particularly in:
• the column(s)
• the eluent before the column(s)
• the Optilab/microOptilab itself
Temperature Control on page 39 explains how to control the Optilab/
microOptilab temperature. The Optilab/microOptilab is extremely
stable thermally, so unless the ambient temperature fluctuates
considerably, the Optilab/microOptilab should be able to achieve a
stable temperature.
• A pump with a constant flow rate is required, and regularly checking
the pressure is an important routine in HPLC and UHPLC. A slowly
increasing or unstable pressure is an indication that the
chromatography conditions are changing, most often due to:
• blockage in the solvent reservoir filter
• blockage in the in-line filter after the pump
• blockage in the column
• malfunctioning pump
• air or gas in the system
These problems often create an unstable baseline due to an unstable
column environment. The instabilities result in fluctuating solution
density, hence a changing RI, which the Optilab/microOptilab
refractometer measures faithfully! The result is a signal with
oscillations, spikes, or drift.
• When changing solvents, special care should be taken to avoid leaving
residues of the old solvent in the chromatography system. It is best to
work with pre-conditioned columns and to change solvents with the
columns by-passed. The Optilab/microOptilab may be used as a

Optilab and microOptilab User’s Guide (M1520 Rev. A) 64

Chapter 7: In-Line HPLC Detection Sample Preparation

monitor during this process, to ensure that solvents are thoroughly

flushed through the detector. Purging the Optilab/microOptilab on
page 31 describes solvent change procedures.
The pump pressure should be noted regularly, and the system should be
checked for any short-term variations in flow rate, eluent, or operating
temperature. If variations are discovered, appropriate action should be
taken as recommended in the user’s manual for the questionable
component.
For further information regarding injection procedures, pumps,
thermostats, etc., refer to the various instruction manuals for these
devices and to the extensive literature on HPLC and UHPLC.

Sample Preparation
To avoid contamination of the column and obtain the best possible
separation, it is important to have a clean sample solution.
Additionally, the following guidelines may be helpful in sample
preparation:
• Solvent used for sample preparation should have the same
composition as the eluent solution. Only HPLC-grade solvents should
be used.
• Sample dissolution may be encouraged by shaking or swirling,
homogenizing, or sonication. Care should be taken to avoid
precipitation from excessively high concentrations. Several hours of
dissolving time may be required for the sample to fully dissolve.
• Particle removal by filtration (0.2 μm to 0.5 μm filter) and the use of a
guard column is highly recommended.
• Degassing improves the quality of the solvent/sample analysis.

Measurement
1. Prior to injecting a sample, confirm that the baseline is stable.
2. Zero the instrument on the front panel display Graph tab by tapping
the Zero dRI button. (See Zero dRI Button on page 39.)

Optilab and microOptilab User’s Guide (M1520 Rev. A) 65

8 Service and Maintenance

This chapter provides detailed instructions on minor maintenance tasks

that can be performed by the user on the Optilab/microOptilab. If you find
a problem that is not described in this manual, or if the suggestions given
here do not appear to work, please contact Wyatt Technology.

Note: Only trained personnel are authorized to perform work inside of the
instrument. These authorized individuals are the individuals or group
responsible for the safe use and maintenance of the equipment.
Authorized personnel must have been trained by a Wyatt representative.
Training may be achieved at Light Scattering University®, as part of on-
site instruction during installation or on-site visit, or other type of
instruction provided by a Wyatt representative. Please contact Wyatt
Technology at support@wyatt.com for any questions.

CONTENTS PAGE
General Maintenance......................................................................................... 67
Daily Maintenance ....................................................................................... 68
Monthly Maintenance................................................................................... 68
Flow Cell Maintenance....................................................................................... 69
On-line Cleaning .......................................................................................... 69
Removing the Top Cover.................................................................................... 71
Replacing the LED/Fiber Light Source............................................................... 73
Setting the LED Power to Zero .................................................................... 73
Replacing the LED/Fiber Light Source......................................................... 74
Changing the Wavelength Setting................................................................ 77
Optimizing the LED/Fiber Light Source........................................................ 77
Cleaning the Air Intake Filter .............................................................................. 77
Preventing Condensation (at Lower Temperatures)........................................... 78
Optilab/microOptilab Firmware Upgrades .......................................................... 78

Optilab and microOptilab User’s Guide (M1520 Rev. A) 66

Chapter 8: Service and Maintenance General Maintenance

General Maintenance
We suggest you do the following:
• Keep the instrument on a flat, clean surface, standing on its feet, and
positioned to allow air flow through all ventilation holes. To keep the
instruments electronics cool, allow a minimum of 10 cm (4 in) of open
space on all sides and a minimum of 15 cm (6 in) of open space at the
back panel.
• Keep the case clean. Periodically wipe down the outside case of the
instrument with a clean, moist cloth to keep it free from dust or
surface stains.
• Allow the instrument to warm up for 30 minutes before taking
measurements.

CAUTION: The Optilab/microOptilab contains electrostatic discharge (ESD) sensitive

parts. Wear an anti-static wristband whenever you open the Optilab/
microOptilab to help prevent potential damage to the instrument from
ESD.

• Ensure that the power is turned off prior to servicing the instrument
with the top cover removed. Wear an anti-static wrist strap that is
properly grounded to the instrument chassis (if the instrument is still
plugged in) or other suitable grounding site. A disposable anti-static
wrist strap is included in the instrument hardware kit.

Chassis
grounding

Figure 8-1: Anti-static Wristband

Optilab and microOptilab User’s Guide (M1520 Rev. A) 67

Chapter 8: Service and Maintenance General Maintenance

We recommend that any time a problem arises, you should turn off the
instrument immediately to avoid any possible damage. Refer to this
manual or contact Wyatt Technology to identify and resolve the problem.
Some errors can cause damage to the internal components if the user
allows the instrument to be powered-up for extended periods of time
before the problem is remedied.

Daily Maintenance
Monitor baseline noise levels and compare to the appropriate noise
specifications for your instrument. If noise increases beyond the
acceptable limit, refer to Noisy Baseline on page 87.
Turn the LED off when instrument is not in use to prolong the lifetime.
This can be done manually by toggling it off on the front panel display
Dashboard tab, or can be programed to be done automatically after the
last experiment of the day has been completed via commands in ASTRA.
See the ASTRA User’s Guide for details.
Activate the Purge valve whenever flowing mobile phase through the
system but not actively collecting data. This will ensure the reference
chamber is sufficiently flushed with fresh mobile phase and will improve
quality of signal. This can be done manually via the Dashboard tab on
the front panel display, or can be programed to be done automatically
after the last experiment of the day has been completed via commands in
ASTRA. See the ASTRA User’s Guide for details.

Monthly Maintenance
Check the air filters on the rear panel fans for dust. Clean with
compressed air or warm soapy water as needed. If the filters are damaged,
contact Wyatt Customer Support to order replacement filters.
Run appropriate validation standards (BSA, 30k PS, etc for dRI – water,
ethanol, etc for aRI) to ensure the Optilab/microOptilab is generating
accurate results. If results drift from the expected/true values, contact
Wyatt Customer Support to assist with troubleshooting.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 68

Chapter 8: Service and Maintenance Flow Cell Maintenance

Flow Cell Maintenance

The flow cell structure is critical to the operation of the Optilab/
microOptilab. If the flow cell is not cared for properly, erroneous results
may be reported.
To keep the flow cell free of contaminants, we recommend regular
maintenance as described here.

On-line Cleaning
At All Times
• Use solvents, including water, that are HPLC grade and filtered
through a 0.2 μm filter.

Note: Organic HPLC grade solvents with no salt added may be used as is.

• Activate the Purge Valve whenever flowing mobile phase through the
system but not actively collecting data. This will ensure the reference
chamber is sufficiently flushed with fresh mobile phase.
• If the instrument is connected to a chromatography system, keep pure,
filtered solvent pumping continuously through the flow cell even when
not actively collecting data.
• To prevent bacterial fouling when using aqueous buffers either include
an antimicrobial preservative such as 200 μg/mL sodium azide,
actively use a Wyatt SOLARIS UV sterilization device, or replace with
freshly prepared buffer after no longer than 3 days of use.
• If you do not plan to use the Optilab/microOptilab for some time, flush
the flow cell with organic solvent or 20 % or greater alcohol (EtOH,
MeOH, or IPA) in water to prevent bacterial growth. Check the solvent
in the cell about once a month. Add more filtered solvent as needed.
See T9004: Shutdown and Storage of Wyatt Detectors for additional
information regarding long-term storage.
Before and After Completing Experiments
• With the flow cell in place, disconnect the Optilab/microOptilab from
your HPLC system. Inject pure, filtered (0.2 μm) solvent to flush the
cell. We recommend that filtered ethanol or isopropanol be left in the
cell.
• A mild detergent solution may also help clean the flow cell, and may be
kept in it overnight when the instrument is not in use, then purged in
the morning.

Protease Cocktail
Some users have found that a simple protease “cocktail” rinse is effective
in removing protein deposits from glass flow cell surfaces. You might be
able to use this rinsing treatment rather than disassembling the flow cell:

Optilab and microOptilab User’s Guide (M1520 Rev. A) 69

Chapter 8: Service and Maintenance Flow Cell Maintenance

Ingredients for 3 mL of protease cleaning solution:

All enzymes are sequencing grade preparations from either
Boerhringer Manheim or Roche.
• Trypsin, modified—25 μg, lyophilized
• Chymotrypsin—25 μg, lyophilized
• Pepsin—25 μg, lyophilized

Note: Using pepsin alone may be sufficient, as it's so non-specific.

Procedure:
1. Reconstitute each with 1 mL of PBS (25 mM Na3PO4 / 150 mM NaCl,
pH 7.25
2. Mix the three solutions and vortex, load syringe fitted with 0.2 μm
filter for LS detector
3. Flush detector with 20 mL pure water, then infuse ~ 1 mL of cocktail
via syringe pump
4. Stop flow, turn on COMET™ and leave it for a few hours or overnight
5. The following morning, remove syringe, flush with 20 mL of HPLC
grade, filtered water, then mobile phase.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 70

Chapter 8: Service and Maintenance Removing the Top Cover

Removing the Top Cover

To replace components or work inside the Optilab/microOptilab, it is
necessary to remove the entire top cover.
To remove the top cover, follow these steps:

CAUTION: Be sure to always wear an anti-static wrist strap when working inside the
instrument.

1. Loosen the three finger-tight captive screws on the rear of the

instrument, indicated by the red circles in the following image.

2. Slide the entire top cover back a few inches. This reveals a gap
between the front panel of the instrument and the top cover.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 71

Chapter 8: Service and Maintenance Removing the Top Cover

3. After the top cover has been pushed back a few inches, remove the top
cover by pulling upward. You may need to pull the sides of the cover
slightly apart if there is resistance lifting the lid up. The top cover is
one continuous piece that includes the sides and cover.

4. Once the cover has been removed, you can access the inside of the
instrument, including the internal stainless-steel tubing.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 72

Chapter 8: Service and Maintenance Replacing the LED/Fiber Light Source

Replacing the LED/Fiber Light Source

The Optilab/microOptilab contains a light source consisting of a Light
Emitting Diode (LED) coupled to an optical fiber. The wavelength of the
light emitted from the LED defines the measurement wavelength. You can
change the measurement wavelength of the Optilab/microOptilab by
changing the LED/fiber light source. If the replacement LED/fiber light
source has a different wavelength than the current light source, you will
need to change the wavelength setting on the Optilab/microOptilab front
panel.
It may also be advisable to change the LED/fiber light source if the optical
power output from the LED/fiber has significantly diminished and the
instrument performance is being compromised. Refer to Troubleshooting
on page 79 to determine if the LED/fiber light source needs to be replaced.
Items required:
• 1.5 mm hex driver (provided with the instrument)
• 2.0 mm hex driver (provided with the instrument)
• 2.5 mm hex driver (provided with the instrument)
• Replacement LED/fiber light source

Setting the LED Power to Zero

1. On the Optilab/microOptilab front panel display, go to the Settings
tab and expand the LED section. Tap the Set button next to LED
Power. In the dialog box that opens, enter 0 (zero), then tap Set. (See
LED Settings on page 47.)
2. Go to the Dashboard tab and toggle the LED off. (See LED Control on
page 37.) Note that the Optilab/microOptilab Forward Monitor alarm
is activated when you set the LED Power to 0 %.
3. On the Settings tab, scroll down to System Control. Expand this
and tap the Restart button. Restarting the instrument ensures that
the LED Power is set to 0 %. (See System Control Settings on
page 52.)
4. After the instrument has fully restarted, power off the Optilab/
microOptilab and disconnect the power cord from the
instrument.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 73

Chapter 8: Service and Maintenance Replacing the LED/Fiber Light Source

Replacing the LED/Fiber Light Source

Use the steps that follow to change the LED/fiber light source.

CAUTION: The Optilab/microOptilab contains electrostatic discharge (ESD) sensitive

parts. Wear an anti-static wristband whenever you open the Optilab/
microOptilab to help prevent potential damage to the instrument from
ESD.

1. Ensure that the power is turned off prior to servicing the instrument
with the top cover removed. Wear an anti-static wrist strap that is
properly grounded to the instrument chassis (if the instrument is still
plugged in) or other suitable grounding site. A disposable anti-static
wrist strap is included in the instrument hardware kit.
2. Follow the instructions in Removing the Top Cover on page 71 to
remove the instrument cover.
3. Gently disconnect the LED/fiber light source connector from the utility
board at the spot labeled P5 by pushing the two side tabs apart. See
Figure 8-2.
4. Using a 2.5 mm hex driver, remove the 6 optical bench cover screws,
then remove the cover. See Figure 8-2.

Remove six
screws

Fiber Spool

LED Power
to P5

Figure 8-2: Optical bench cover and P5 location

Optilab and microOptilab User’s Guide (M1520 Rev. A) 74

Chapter 8: Service and Maintenance Replacing the LED/Fiber Light Source

5. Remove the foam piece inside the optical bench that covers the light
fiber connector, see Figure 8-3.

Foam to
remove

Figure 8-3: Removable foam cover

6. Using your fingers, unscrew the light fiber connector from the fiber
holder, see Figure 8-4.

Light fiber
connector

Figure 8-4: Light fiber connected (left) and disconnected (right)

Optilab and microOptilab User’s Guide (M1520 Rev. A) 75

Chapter 8: Service and Maintenance Replacing the LED/Fiber Light Source

7. Using your fingers, loosen the two screws that secure the fiber spool to
the optical bench. Remove the spool. See Figure 8-5.

Two screws

Figure 8-5: Removing the Fiber Spool

8. Mount the replacement fiber spool kit and tighten the two screws to
secure the spool to the bench.
9. Using fingers, insert and screw the new light fiber connector into the
fiber holder in the optical bench.
10. Reinstall the foam piece, optical bench cover, and screws.
11. Connect the power cable to the P5 position on the circuit board,
pressing the black tabs on the cable back together seat it.
12. Reinstall the instrument cover and screws.
13. Plug the power cable into the back of the instrument and power on.
14. Continue with Changing the Wavelength Setting and Optimizing the
LED/Fiber Light Source as required.

CAUTION: Unless you are replacing a damaged LED/fiber light source, you should
store the removed fiber in a safe place. Take care to ensure that extra
curvature is not introduced into the fiber during storage; this helps
prolong the LED/fiber light source lifetime.

CAUTION: Do not adjust the LED Power before changing the wavelength setting (if
necessary) as described in the following paragraphs.

15. Calibrate the LED monitor with the new LED/fiber by following the
steps described in Instrument Calibration for dRI on page 53 and
Instrument Calibration for aRI on page 58.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 76

Chapter 8: Service and Maintenance Cleaning the Air Intake Filter

Changing the Wavelength Setting

If the new LED/fiber light source has a different wavelength than the
previous light source, you need to change the wavelength setting on the
Optilab/microOptilab front panel.
1. Go to the Settings tab and scroll down. Expand the Instrument
Information section. Tap the Set button next to Wavelength. (See
Instrument Information Settings on page 45.)
2. Enter the wavelength of the LED fiber in nm in the dialog box and tap
Set. The new wavelength is shown under the Wavelength field.
3. To ensure that the LED Wavelength setting is saved, scroll down to
the System Control section. (See System Control Settings on
page 52.) Expand this section and tap Restart. Allow the Optilab/
microOptilab to shut down and restart.

Optimizing the LED/Fiber Light Source

Note: If the Optilab/microOptilab was disconnected from flow during the

replacement procedure, flush the flow cell with your mobile phase before
running the optimization procedure. The LED Optimization procedure
fails if there is a bubble in the flow cell.

The optimization process iteratively evaluates your system's optimum

LED settings.
1. Go to the Settings tab on the Optilab/microOptilab front panel
display. Expand the LED section and tap the Optimize button. (See
LED Settings on page 47.)
2. After optimization, the Forward Monitor (also shown in the LED
settings) should be 93 % to 100 % for the Optilab and 85 % and 100 %
for the microOptilab. The Power should be less than 100 %.

Cleaning the Air Intake Filter

Periodically remove and clean the foam filter for the instrument’s air
intake fan. The air intake fan is located on the rear panel of the
instrument in the center above the Dry Gas Purge port (see Figure 2-2).
1. Lift the filter bracket off of the rear panel of the instrument and
remove the air filter from the filter bracket.
2. Wash the air filter with mild soap and water.
3. When dry, place the air filter back into the filter bracket.
4. Attach the filter bracket with filter back on the rear panel of the
instrument.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 77

Chapter 8: Service and Maintenance Preventing Condensation (at Lower Temperatures)

Preventing Condensation (at Lower Temperatures)

When operating temperature-controlled Wyatt instruments at sub-
ambient temperatures (such as 5 °C), a dry nitrogen (or other inert gas)
purge is essential to prevent condensation. A minimum pressure of 20 psi
is necessary when using a temperature control set point below 20 °C. See
Dry Gas Connection on page 29 for how to connect a dry gas line.

CAUTION: Instruments operated below ambient temperature must reach ambient

temperature before they can be switched off. Fans and the dry gas purge
valves do not work if the unit is powered off, so it is crucial that the
instrument is brought up in temperature with fans operating and dry gas
flowing to avoid condensation.

Failure to follow the steps below may result in electronic failures and
corrosion damage to the instrument.
• Set the temperature to 25 °C after a low-temperature measurement
has been completed. This is best done be from the Dashboard tab on
the instrument’s front panel (see Temperature Control on page 39).
• Leave the instrument powered on for at least 12 hours (overnight)
after ambient temperature has been reached to ensure that any
residual moisture has been removed.
• Let the instrument warm up to 25 °C as described above at least every
4 weeks.

Note: Control the instrument temperature from the front panel of the Optilab/
microOptilab. Configuring the “Temperature Control” in ASTRA does not
set the instrument temperature.

For recommendations on how to operate Wyatt instruments in a cold

room, see TN9001: Operating Wyatt Instruments in a Cold Room and
TN9006: Preventing Condensation in Wyatt Detectors.

Optilab/microOptilab Firmware Upgrades

For peak performance and stability of your Optilab/microOptilab, check
regularly for the most recent firmware. The Optilab/microOptilab
firmware upgrades are available on the Wyatt web page. Visit
www.wyatt.com/firmware and navigate to the Optilab or microOptilab
firmware update page to obtain the latest firmware version and
instructions for installing new firmware.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 78

9 Troubleshooting

This chapter provides details about troubleshooting procedures for the

Optilab/microOptilab. Prior to troubleshooting any issues, ensure that the
Optilab/microOptilab firmware is updated to the current version. See
Optilab/microOptilab Firmware Upgrades on page 78.
CONTENTS PAGE
Leak Sensors and Cleaning After a Fluid Leak .................................................. 80
Replacing Plugged Tubing ................................................................................. 83
Changing a Fuse................................................................................................ 83
Forward Monitor Alarm....................................................................................... 84
LED Monitor Alarm ............................................................................................. 85
Temperature Will Not Set Below 20 °C .............................................................. 86
Unexpected RI Trace ......................................................................................... 86
Noisy Baseline ................................................................................................... 87
Wavy or Drifting Baselines ................................................................................. 87
High Pressure .................................................................................................... 88
Microsoft Windows Encounters Problems.......................................................... 88

Optilab and microOptilab User’s Guide (M1520 Rev. A) 79

Chapter 9: Troubleshooting Leak Sensors and Cleaning After a Fluid Leak

Leak Sensors and Cleaning After a Fluid Leak

Liquid from leaks of internal and external fittings is directed into a well
inside the instrument (located behind the fluid connections on the front
panel). If a liquid leak occurs, one of two sensors activates an alarm. For
more information about alarms, see Alarm Section on page 41.

Top view
of Optilab/microOptilab
with drip tray location

Drain Tubing from

Instrument Stack

Front Panel
Leak Sensor

Internal
Leak Sensor

Optical Bench
Leak Sensor
(inside)
Drip Tray

Drain Tubing from

Optical Bench

Figure 9-1: Leak sensor locations (circled in red)

The Optilab/microOptilab has the following three leak sensors:

• The inlet/outlet near the front panel (front panel leak sensor)
• Near the inlet/outlet connection to the optical bench (internal leak
sensor)
• Inside the optical bench (optical bench leak sensor)
Leaks trigger alarms on the front panel display and drain into the drip
tray, from which fluid can be drained to waste through the leak port on the
underside of the instrument.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 80

Chapter 9: Troubleshooting Leak Sensors and Cleaning After a Fluid Leak

To clean up after a leak, follow these steps:

1. Disable the pump or otherwise prevent additional liquid from being
sent into the Optilab/microOptilab.
2. Disconnect the power cord from the instrument.

CAUTION: The Optilab/microOptilab contains electrostatic discharge (ESD) sensitive

parts. Wear an anti-static wristband at a grounded workstation whenever
you open the Optilab/microOptilab to help prevent potential damage to the
instrument from ESD.

3. Put on an anti-static wrist strap and gloves or protection from solvent.

CAUTION: Be sure to wear gloves and other protection appropriate for handling the
solvent that has leaked. Always use absorbent paper or cotton to absorb as
much of the leak as possible before cleaning the leak sensor.

4. Front Panel Leak Sensor: Fluid passes this leak sensor before
draining through the bottom of the instrument.This sensor can be
cleaned entirely from the front panel without removing the cover.
Squirt some clean deionized water or alcohol (or a solvent that is co-
miscible with the leaked solvent) into the drip tray from the front of
the instrument and clean the sensor with a cotton swab (provided in
the hardware kit). Rinsing with clean water can help remove salt
deposits that may activate the alarm.

The leak sensors are conductivity sensors. Allow them to air dry or use
a cotton swab to accelerate the process.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 81

Chapter 9: Troubleshooting Leak Sensors and Cleaning After a Fluid Leak

5. Internal Leak Sensor: This sensor can be cleaned by removing the

cover. Please see Removing the Top Cover on page 71. The sensor can
be cleaned by squirting some clean water or alcohol (or a solvent that
is co-miscible with the leaked solvent) on it and cleaning with a cotton
swab. The sensor is shown below, circled in red.

6. Optical Bench Leak Sensor: This sensor is located inside the optical
bench. Make sure that you have thoroughly cleaned the other two
sensors before opening the optical bench to check for a leak. Remove
the screws on the optical bench to access this sensor. This sensor can
be cleaned with a cotton swab and clean water or alcohol (or a solvent
that is co-miscible with the leaked solvent).
7. Install and secure the cover with the screws you removed.
If the alarm continues after cleaning the sensor surface, contact Wyatt
Technical Support for assistance.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 82

Chapter 9: Troubleshooting Replacing Plugged Tubing

Replacing Plugged Tubing

The Optilab/microOptilab contains a short section of tubing directly after
the input bulkhead union, which is of slightly smaller inner diameter (ID)
than the rest of the tubing in the instrument. The intent of this section of
tubing is to provide a serviceable location where any particles which might
plug the instrument are likely to be trapped. In the event that the Optilab/
microOptilab instrument is plugged, the first step should be to replace this
section of tubing (spare tubing is located in your hardware kit). Contact
Wyatt Technology at support@wyatt.com for replacement parts, if
necessary.
It is important not to attempt to clear a plug by reversing the flow
direction through the instrument. The instrument has very small ID
tubing on the input, and large ID tubing on the output. Because of this,
reversing the flow direction can result in a large pressure in the
instrument flow cell, which can destroy the cell.

Changing a Fuse
The fuses are located in the power connection socket (see Figure 2-2).
In order to change fuses, you need a tool for prying the AC Power module
cover off, such as a small-bladed screwdriver and fuses from the spares
supplied in the accessory kit.
To replace a fuse, follow these steps:
1. Disconnect the power cord.
2. Open the cover of the AC Power
module using a small blade
screwdriver or similar tool.
3. Replace the burned out fuse(s).
Refer to Power Connector on
page 23 for fuse specifications. Both Figure 9-2: Fuseholder and Fuses
fuses must be installed for the
instrument to operate correctly.
4. Replace the cover of the AC Power module and reconnect the power
cord.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 83

Chapter 9: Troubleshooting Forward Monitor Alarm

Forward Monitor Alarm

A forward monitor alarm occurs if the light intensity on the photodiode
array drops too low. Such a situation can occur any time the refractive
index difference between the sample and reference fluids is large enough
to cause the light beam to move off the end of the photodiode array.
This happens in the following situations:
• You are changing solvents.
• The sample fluid refractive index is very different from the reference
fluid refractive index.
• The sample refractive index is changing dramatically, such as when a
very concentrated solution is injected directly into the Optilab/
microOptilab. When injecting a very concentrated solution directly
into the Optilab/microOptilab, the Forward Monitor alarm may
sometimes be observed at the leading and trailing edge of the injection.
A low light condition during the leading and trailing edge of an
injection does not observably effect the accuracy of the measurement.
The forward monitor alarm activates if the voltage measured from the
photodiode array, which is proportional to the light intensity on the
photodiode array, drops below a threshold value of 5 V for 660 nm light
sources. This is equivalent to the Forward Monitor dropping below a
threshold value of 50 %.
The Forward Monitor trace can be selected from a Y Axis drop-down
menu on the Graph tab. (See Selecting the Display Axes on page 40.) It
represents the intensity of the light on the photodiode array. This value
can give an indication of the problem causing the Forward Monitor alarm.
In addition to the expected low light condition that arises when changing
solvents or injecting a concentration that is beyond the capabilities of the
Optilab/microOptilab, other reasons the light intensity on the photodiode
array may be too low are as follows:
• LED Off—On the Dashboard tab, you can toggle the LED/fiber light
source On and Off. Check that the LED/fiber light source is On.
• Air bubble in the flow cell—If the LED light source is on, but the
voltage read from the photodiode array is low, there may be an air
bubble in the flow cell. Typically a bubble in the flow cell causes
intermittent episodes of low light and large noise. To prevent air
bubbles from forming in the flow cell, be sure to use degassed solvents.
To dissolve air bubbles present in the flow cell, flow degassed solvent
through the Optilab/microOptilab in purge mode. Purge in this state
for several hours to be sure that the bubble is 100 % dissolved.
Temporarily changing to a different solvent is another strategy for
removing an air bubble, particularly when troubleshooting bubbles in
aqueous solvents. Introducing alcohol, for example, breaks the surface
tension of a bubble.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 84

Chapter 9: Troubleshooting LED Monitor Alarm

• Dirty or occluded flow cell—If the flow cell glass is dirty or

occluded, less light will be able to pass through to the forward monitor.
If a dirty flow cell is suspected, proceed with On-line Cleaning on
page 69.
• Light source dimmed with time—If the LED light source is on, and
the voltage read from the photodiode array is stable but slightly below
a threshold value, the light source may simply have dimmed
somewhat with time. Increasing the power to the light source
increases the intensity of light on the photodiode array. When the
voltage read from the photodiode array rises above the threshold
value, the Forward Monitor alarm deactivates. In the LED section on
the Settings tab, tap the Optimize button to have the instrument
automatically set the optimal power to the LED/fiber light source. (See
LED Settings on page 47.) Changing the power to the light source does
not effect the instrument calibration constant.
• Light source burned out—If the LED light source is On and the
system has been carefully purged with degassed solvent, but the
Forward Monitor is close to 0 %, then the light source may be
burned out. The light source is easily replaceable, taking about 15
minutes from start to finish. Contact Wyatt Technology Corporation
for a replacement LED/fiber light source. If this is the case, the LED
Monitor alarm will be activated.

LED Monitor Alarm

An LED monitor alarm occurs if the amount of light detected at the tip of
the LED/fiber is too low before the light is passed through the Optilab/
microOptilab optical system. The power of the LED/fiber is auto-adjusted
to maintain the level of light received at the PDA at an optimum level.
This corresponds to a Forward Monitor level of 93 % to 95 % which can
be checked by selecting Forward Monitor from the drop-down menu in
the Graph Tab on page 39.
With time, the amount of power the LED/fiber needs to maintain this level
will increase. The LED Monitor Alarm will activate when the Monitor
percentage divided by the Power percentage becomes less than 0.5. Both
the Monitor and Power values are located under the LED Settings on
page 47.
When this happens, the LED/fiber should be replaced. Refer to Replacing
the LED/Fiber Light Source on page 73 for instructions on changing the
LED/fiber.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 85

Chapter 9: Troubleshooting Temperature Will Not Set Below 20 °C

Temperature Will Not Set Below 20 °C

For sub-ambient operation, dry gas must be slowly flowed into the cool
thermal environment to prevent water vapor from condensing on the
electronics or optics.
The Optilab/microOptilab contains a gas pressure sensor to measure the
pressure of the dry gas supplied to it. It will not set the temperature set
point below 20 °C unless at least 20 psi of pressure is sensed. If dry gas of
sufficient pressure is supplied to the Optilab/microOptilab and the
temperature is set below 20 °C, but the gas pressure subsequently drops
below 20 psi, then the temperature set point is automatically set to
20.5 °C.

Unexpected RI Trace
The Optilab/microOptilab LED beam image must be measured and fitted
properly in order for the recorded data to be accurately interpreted over
the full range of measurement. If the LED intensity is too strong or too
weak, a proper beam image will not be discernible by the internal optical
detection device. The “low light” (Forward Monitor) alarm was discussed
in a previous section. An overly powerful LED will cause sudden jumps in
an RI chromatogram, especially as the signal moves up and down along
the sides of an eluting peak. Such data are not valid for quantitative
analysis. An obscured beam (due to a heavily soiled flow cell) may result in
a scattered, irregular trace, but this effect is rarely seen.
If unexpected data traces are observed, the LED power should be checked
as described in Optimizing the LED/Fiber Light Source on page 77, and
the Optilab/microOptilab flow cell should be flush-cleaned with a solution
such as Contrad. Optilab/microOptilab firmware features automatic
optimization of the LED power for improved reliability, making it
essentially impossible to overpower an Optilab/microOptilab LED.
The goodness of the Optilab/microOptilab measurements may be assessed
by viewing the “peak lock” and “fit peak lock” traces in an ASTRA data
collection. In ASTRA, click Experiment→Graph→Add Custom Plot,
and add the peak lock and fit peak lock traces from the “Original Data”
category. See the ASTRA User’s Guide for additional instructions for
creating a custom graph, if needed. If a good Optilab/microOptilab optical
beam image is found for a given measurement slice, peak lock will be 1.00.
If the components of the beam image are each successfully fit, then fit
peak lock is also 1.00. If values lower than 1.00 are obtained for peak lock
or fit peak lock in a given data slice, then the LED is possibly too bright,
too dim, or the optics, cell, or cell contents are obscuring the beam.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 86

Chapter 9: Troubleshooting Wavy or Drifting Baselines

Wavy or Drifting Baselines

A wavy or drifting baseline can be caused by several conditions:
If the reference cell has not been purged thoroughly, these symptoms can
occur. It is recommended that the Purge Valve be turned on whenever
mobile phase is flowing through the system and an experiment is not
being actively run. Refer to General Maintenance on page 67.
If a salt containing mobile phase is not properly mixed, localized
concentration differences inside the mobile phase reservoir will cause
oscillations in signal. Adding a stir bar to the HPLC reservoir to
homogenize the mobile phase can help with this.
The Optilab/microOptilab can be sensitive to external temperature
fluctuations. Do not place the instrument next to heating/cooling vents
and try to keep the ambient laboratory temperature as constant as
possible. Ensure adequate space for ventilation around the instrument.
See General Maintenance on page 67.

Noisy Baseline
If the baseline noise of the instrument seems excessive, try the following:
1. Check that the LED light source is On, and that no Forward Monitor
alarm exists as described in Forward Monitor Alarm on page 84.
2. With the purge valve turned on, use a syringe pump to flush the flow
cell with no less than 10 mL solvent, filtered to 0.2 μm with a syringe
tip filter.
3. Un-plumb the Optilab/microOptilab from any flow system. Place a
plug in the OUT port, and leave the IN port open to the atmosphere.
See if the noise still exists.
If the noise no longer is present, then the noise could have its origin in the
chromatographic system, or could be due to a small bubble in the flow cell
that is forced into the measurement region only under flow conditions. Use
a syringe to inject solvent by hand into the Optilab/microOptilab. If the
noise is still not present, then the noise probably has its origins in the
chromatographic system. Refer to Conditions for In-Line Operation on
page 64 for ways to reduce noise in chromatographic systems.
If the noise is intermittent during flow conditions, or remains in the
absence of flow, the noise may be due to a bubble in the flow system that is
small enough to not block light through the system, but large enough to
significantly affect the measurement. Follow the procedure for eliminating
bubbles outline in Forward Monitor Alarm on page 84.
Noise can also be caused by a dirty flow cell. Follow the procedure for Flow
Cell Maintenance on page 69.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 87

Chapter 9: Troubleshooting High Pressure

High Pressure
A short length of tubing (0.007 in. ID in the Optilab; 0.004 in. ID in
microOptilab) is connected to the inlet union inside the chassis. This
relatively narrow tubing is designed to be the most likely place for a
blockage to form. The expected pressure generated by an Optilab is about
50 psi in water or aqueous buffer flowing at 1 mL/min and 25 °C. For a
microOptilab the expected pressure is about 200 psi in water or aqueous
buffer flowing at 0.5 mL/min and 25 °C. These values will be higher or
lower depending on the solvent, flow rate, and temperature.
If a blockage is suspected, a good first troubleshooting step is to replace
this narrow tubing. If high pressure persists, contact Wyatt Customer
Support for assistance.

Caution: Never flush the Optilab/microOptilab in reverse direction! Liquid should

only be pumped into the Optilab/microOptilab IN port while the Optilab/
microOptilab is powered on and fully initialized. Pumping liquid into the
OUT port may cause serious damage to the Optilab/microOptilab.

Inlet Union

Optilab
0.007 in. tubing,

microOptilab
0.004 in. tubing

Figure 9-3: Optilab/microOptilab with Top Cover Removed

Microsoft Windows Encounters Problems

If the Microsoft Windows operating system on the front panel display
encounters a problem that causes it to freeze or crash, the Optilab/
microOptilab reboots the operating system within one minute. You can
use the power switch on the front panel to turn the Optilab/microOptilab
off and on if you want to reboot the instrument yourself.
Experiments in progress when the operating system crashes must be
restarted.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 88

A Acronyms and Abbreviations List

The following acronyms and abbreviations are used in this manual:

Item Meaning
ac alternating current
A ampere
aRI absolute refractive index
°C degree celsius
cm centimeter
dc direct current
DHCP dynamic host configuration protocol
dRI differential refractive index
g gram
GPa gigapascal
HPLC high pressure liquid chromotography
Hz hertz
ID inside diameter
in. inch
IP internet protocol
LAN local area network
LED light emitting diode
mg milligram
MHz megahertz
MPa megapascal
μL microliter
μm micrometer
mL milliliter
mm millimeter
mV millivolt
nm nanometer
NMOS n-doped metal/oxide semiconductor
OD outside diameter
ppm parts per million
psi pounds per square inch
RI refractive index
RIU refractive index unit
STP standard temperature and pressure = 0 °c and 1 atmosphere of pressure
TTL transistor-transistor logic
V volt
Vac volts alternating current
Vdc volts direct current

Optilab and microOptilab User’s Guide (M1520 Rev. A) 89

B Operating Principles and Theory

This appendix provides a basic overview of the theory and operation of the
Optilab/microOptilab.
CONTENTS PAGE
Basic Principles.................................................................................................. 91
Conventional Flow Cell ............................................................................... 91
Optilab/microOptilab Flow Cell..................................................................... 91
Measurement of the Beam Deflection Angle...................................................... 93
Conventional Split Photodiode Based Instrument ....................................... 93
Wyatt Technology Corporation Beam Positioning Technology..................... 94

Optilab and microOptilab User’s Guide (M1520 Rev. A) 90

Appendix B: Operating Principles and Theory Basic Principles

Basic Principles
Conventional Flow Cell
The Optilab/microOptilab is a special variation of the deflection-type
differential refractometer. For this type of differential refractometer, a
light beam passes through a flow cell containing reference and sample
fluids, and undergoes an angular deflection based upon the refractive
index difference between the two fluids. A conventional deflection type
differential refractometer flow cell is shown in Figure B-1.

Figure B-1: Conventional deflection type flow cell

For this conventional flow cell, if the sample refractive index ns and
reference fluid refractive index nr are identical, then the light beam exits
the cell in a direction parallel to the incoming beam. If ns is not equal to nr,
then the light beam exits the cell at some angle θ to the incoming beam. To
the first order, this angle is proportional to the refractive index difference
between ns and nr. In addition to any angular deflection, the light beam
undergoes a slight translation due to passage through the material
comprising the body of the flow cell (i.e., the window between the sample
and reference fluid chambers). The optical system inside the differential
refractometer must separate angular deflections from translation of the
light beam.
To measure the refractive index difference between two fluids, both
sample and reference chambers are filled with the reference fluid, and the
starting position of the light beam is noted. This is considered the “zero”
position. The reference chamber is then capped, trapping the reference
fluid inside. Fluid is then directed through the sample chamber, and
changes in the refractive index of that fluid cause an angular deflection of
the light beam. Measurement of the light beam angular deflection yields
the refractive index difference between the sample fluid and the reference
fluid.

Optilab/microOptilab Flow Cell

The Optilab/microOptilab differs from the conventional design because its
flow cell contains a novel feature to allow, under certain conditions, the
measurement of the absolute refractive index (aRI) of a fluid, as well as the

Optilab and microOptilab User’s Guide (M1520 Rev. A) 91

Appendix B: Operating Principles and Theory Basic Principles

differential refractive index (dRI) between two fluids. The flow cell in the
Optilab/microOptilab is shown in Figure B-2. The reference chamber has a
non-90 angle on its exit face.

Figure B-2: Optilab/microOptilab differential and absolute refractive index flow cell

This unique flow cell has an extra internal wedge in its reference chamber.
The extra wedge lends an additional angular deflection φ to the light
beam. The value of the angle φ depends upon the wedge angle and the
refractive index difference between the reference fluid and the quartz body
of the Optilab/microOptilab flow cell. Knowing the wedge angle and the
refractive index of the quartz, a measurement of φ yields the refractive
index nr of the reference fluid. In practice, the wedge angle is determined
by measuring the angular deflection φ for a few fluids of known refractive
index.
The total angular deflection of the light beam depends upon both the
refractive index difference between the sample and reference fluids and
the aRI of the reference fluid. To determine the aRI of a fluid, it is required
that the same fluid be present in both the sample and reference chambers.
With the same fluid in the sample and reference chambers, the refractive
index difference is zero, and any angular deflection of the light beam is
due solely to the aRI of the reference fluid.
Measurement of the refractive index difference between two fluids is
accomplished by noting the angular deflection φ of the light beam at the
beginning of a data run, and considering this the “zero” position of the
light beam.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 92

Appendix B: Operating Principles and Theory Measurement of the Beam Deflection Angle

Measurement of the Beam Deflection Angle

Conventional Split Photodiode Based Instrument
Measurement of the deflection of the beam of light after it has passed
through the flow cell is the basic measurement made in a deflection type
refractometer. This deflection is proportional to the dRI of the two fluids
being measured. Conventionally, a split photodiode is used to measure the
light beam angular deflection, as pictured in the illustration below.

Figure B-3: Light beam angular deflection

The split photodiode contains two photodiode light detectors placed side to
side. As the light beam changes angle, the beam moves away from one
photodetector and onto the other. The voltage difference between the two
detectors gives a measure of the light beam position, which is proportional
to the light beam angular deflection, which is in turn proportional to the
differential refractive index.
The precision of a split photodiode detector based instrument is limited by
the precision with which the voltages may be read from the two
photodetectors and the intensity stability of the light source. The
maximum signal a split photodiode detector may observe depends upon
the width of the light beam and the width of the photodetectors. Once the
light beam has walked entirely off of one photodetector and onto the other,
there is no way to determine the beam position.

Figure B-4: Optilab/microOptilab photodiode display

Optilab and microOptilab User’s Guide (M1520 Rev. A) 93

Appendix B: Operating Principles and Theory Measurement of the Beam Deflection Angle

Wyatt Technology Corporation Beam Positioning Technology

Rather than using two photodetectors, the Optilab/microOptilab contains
512 light measuring elements in one photodiode array. Each element of
the photodiode array, called a pixel, precisely measures the intensity of
light impacting upon it.
The Optilab/microOptilab records voltages from each of the 512 elements
of the photodiode array 10 to 20 times per second. To obtain the most
precise possible measurement, the signal from each element is measured
many times and the results averaged together. Hundreds of thousands of
voltage measurements per second are required. The data from the 512
pixels are analyzed using mathematical algorithms to determine the
position of the light beam on the array.
The computational power to perform these mathematically intensive
operations at such rates was unavailable 15 years ago, but now fits into
the small Intel processor inside your Optilab/microOptilab. Using a
photodiode array, high-speed electronics, and advanced mathematical
analysis techniques, the light beam position may be measured to less than
1 nm. The photodiode array is 1.3 cm long, and so the beam can be
deflected more than 1 cm before reaching the end of the photodiode array.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 94

C Optilab Specifications

This appendix provides specification details for the Optilab instruments.

CONTENTS PAGE
Optilab Specifications......................................................................................... 96
microOptilab Specifications................................................................................ 97

Optilab and microOptilab User’s Guide (M1520 Rev. A) 95

Appendix C: Optilab Specifications Optilab Specifications

Optilab Specifications

Differential Refractive Index (dRI) Range and Sensitivity

Dynamic Range –0.0047 RIU to +0.0047 RIU
Peak-to-Peak Noisea ±7.5 x 10–10 RIU
Digital Output 21+ bit only via digital communication
Response Time 0.1 s to 5.0 s, user selectable
High Concentration Option Optilab dRI Range and Sensitivity
Range –0.0026 RIU to +0.034 RIU

Peak-to-Peak Noisea ±1.5 x 10–9 RIU

Absolute Refractive Index (aRI) Range and Sensitivity

Range 1.2 RIU to 1.8 RIU
Sensitivity ±0.002 RIU
Fluid Volumes and Pressures
Flow Cell Volume 7.4 µL
Inlet tubing (0.010” ID) 44 µL
Outlet tubing (0.03” ID) 370 µL
Backpressure created at 25.38 psi (1.75 bar) @ 1.0 mL/min of pure water at 20 °C.
input port
Maximum system pressure 30 psi (2 bar)
Power Requirements Universal input, AC 100/115/220/240 V, 50/60 Hz

Power Peakb 150 W

Power Typical 30 W
Light Source 660 nm (±10 nm) LED light source, standard
(other wavelengths available)
Sample Temperature Control Range 4 °C to 65 °C, temperature regulated to ±0.005 °C
Safety Sensors Vapor and liquid (leak)
Display/User Interface 7 in. 1280 x 800 color high resolution LCD
Digital Communication Ethernet
Auxiliary I/O
Inputs Analog In (16 bit, ±10 V Analog to Digital), Zero dRI, Purge,
Recycle In, Autoinject, Alarm In
Outputs Analog Out (16-bit dRI Digital to Analog), Autoinject
Retransmit, Alarm Out External, Recycle Out (to switch
Orbit between waste and recycle)
Dimensions 58 cm (L) x 36 cm (W) x 18 cm (H)
Weight 16.5 kg

a. Short term peak-to-peak noise is measured as per ASTM-E1303-95(2000) using a 4-second

time constant and temperature controlling at 25 °C.
b. Typical power consumption is measured after boot-up. Theoretical maximum transient pow-
er consumption during boot-up can reach up to 960 W (240 V x 4 A fuse).

Optilab and microOptilab User’s Guide (M1520 Rev. A) 96

Appendix C: Optilab Specifications microOptilab Specifications

microOptilab Specifications

Differential Refractive Index (dRI) Range and Sensitivity

Dynamic Range –0.0047 RIU to +0.0047 RIU
Peak-to-Peak Noisea ±1.5 x 10–9 RIU (across entire range)
Digital Output 22+ bit @ 25 Hz
Analog Output ±10 V or ±1 V output, 18-bit resolution
Response Time 0.04 s to 5.0 s, user selectable
Absolute Refractive Index (aRI) Range and Sensitivity
Range 1.28 RIU to 1.8 RIU
Sensitivity ±0.002 RIU
Fluid Volumes and Pressures
Band Broadeningb <4 µL
Flow Cell Volume 7.4 µL
Inlet tubing (0.005” ID) 6.5 µL
Outlet tubing (0.030” ID) 275 µL
Backpressure created at 118.2 psi (8.15 bar) @ 0.5 mL/min of pure water at 20 °C.
input port
Maximum permissible back 30 psi (2 bar)
pressure at output port
Power Requirements Universal input, AC 100/115/220/240 V, 50/60 Hz
c 150 W
Power Peak
Power Typical 30 W
Light Source 660 nm standard; Other wavelengths available
Sample Temperature Control Range 4 °C to 65 °C, temperature regulated to ±0.005 °C
Safety Sensors Vapor and liquid (leak)
Display/User Interface 7 in. 1280 x 800 color high resolution LCD
Digital Communication Ethernet
Auxiliary I/O
Inputs Analog In (16 bit, ±10 V Analog to Digital), Zero dRI, Purge,
Recycle In, Autoinject, Alarm In
Outputs Analog Out (16-bit dRI Digital to Analog), Autoinject
Retransmit, Alarm Out External, Recycle Out (to switch
Orbit between waste and recycle)
Dimensions 58 cm (L) x 36 cm (W) x 18 cm (H)
Weight 16.5 kg

a. Short term peak-to-peak noise is measured as per ASTM-E1303-95(2000) using a 0.5-second

collection interval (1-second time constant) and temperature controlling at 25 °C.
b. Peak broadening measured over full width at half max, flow rate = 0.3 mL/min
c. Typical power consumption is measured after boot-up. Theoretical maximum transient pow-
er consumption during boot-up can reach up to 960 W (240 V x 4 A fuse).

Optilab and microOptilab User’s Guide (M1520 Rev. A) 97

D Wetted Materials/Cell Properties

This appendix contains information about the wetted thermal and

chemical properties of the flow cell. All data and descriptions are from the
Schott Glass Optical Glass Catalog.

CONTENTS PAGE
Flow Cell Properties ........................................................................................... 98
Thermal Properties ...................................................................................... 98
Refractive Indices ........................................................................................ 98
Chemical Properties..................................................................................... 98
Wetted Materials ................................................................................................ 99
Definition of Terms ............................................................................................. 99

Flow Cell Properties

Thermal Properties
Glass Thermal Expansion Transformation Specific Heat
Classification Temperature
-30 to 70 °C 20 to 300 °C c p
= (J g × K )

Fused silica 4.7 x e-7 /K 4.7 x e-7/K 970 °C 0.749

Refractive Indices

Glass Classification Refractive Index

λ = 633nm
Fused silica 1.457055

Chemical Properties
To interpret the CR, FR, SR and AR values, see Definition of Terms on
page 99.
Glass Classification Bubble CR FR SR
Class
Fused silica 0 1 0 1
Acceptable mobile phase pH range: 1 - 11

Optilab and microOptilab User’s Guide (M1520 Rev. A) 98

Appendix D: Wetted Materials/Cell Properties Wetted Materials

Wetted Materials
The wetted materials are 316 stainless steel, PTFE, and fused silica.

Definition of Terms
Transformation Temperature
Temperature at which deformation of precision finished surfaces and a
change in the refractive index can occur.
Climate Resistance (CR 1−4)
Class CR 1; after 180 hours of exposure the glasses exhibit no or only
slight signs of deterioration due to changing climatic conditions. Under
normal humidity conditions that prevail during the processing and
storage of optical glasses, no surface deterioration of class CR1 glasses
is to be expected.
Resistance to Staining (FR 0−5)
Class FR 0; after exposure to a standard acetate solution (pH=4.6) for
over 100 hours, no interference color staining is observed.
Resistance to Acids (SR 1−4)
Class SR 1; after a 100 hour exposure to an aggressive solution of 0.3n
nitric acid (pH=0.3), the smallest visible detectable thickness, 0.1
micrometer, is not dissolved.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 99

E Instrument Connectivity

This appendix provides instrument connectivity instructions. For further

assistance, please contact support@wyatt.com.
CONTENTS PAGE
Components..................................................................................................... 101
Instrument Connections ............................................................................. 101
LAN connection.......................................................................................... 101
Computer connections ............................................................................... 102
Crossover cable ......................................................................................... 102
Ethernet cable............................................................................................ 103
Ethernet to USB adapter............................................................................ 103
Ethernet switch .......................................................................................... 104
Connecting to a LAN ........................................................................................ 104
One Instrument to LAN .............................................................................. 104
One Instrument and Computer to LAN ...................................................... 105
Multiple Instruments to LAN....................................................................... 105
Multiple Instruments and Computer to LAN ............................................... 106
Connecting via USB ......................................................................................... 107
One Instrument to USB via a Crossover Cable ......................................... 107
One Instrument to USB Using an Ethernet Switch .................................... 108
Multiple Instruments to USB ...................................................................... 108
Connecting via Ethernet When Not on a LAN.................................................. 109
One Instrument to Computer Using Crossover Cable ............................... 109
One Instrument to Computer Using an Ethernet Switch ............................ 109
Multiple Instruments to Computer Using an Ethernet Switch..................... 110
Instrument Network Settings ............................................................................ 110
Accessing Instruments with ASTRA..................................................................111
Troubleshooting and Diagnostics ..................................................................... 112
Verifying Instrument Connections .............................................................. 112
Please read over the Components section to gain an understanding of the
components to be used. Then read over either Connecting to a LAN on
page 104, Connecting via USB on page 107, or Connecting via Ethernet
When Not on a LAN on page 109 depending on your configuration. Finally,
read over Instrument Network Settings on page 110 for instrument
settings.
Please read Accessing Instruments with ASTRA on page 111 for
instructions on accessing instruments via ASTRA. Finally, if you
experienced problems connecting to your instrument, please read
Troubleshooting and Diagnostics on page 112.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 100

Appendix E: Instrument Connectivity Components

Components
Instrument Connections
Figure E-1 shows a detail of the instrument back panel. The Ethernet port
is to be used for all connections in these instructions.

Ethernet

Figure E-1: Detail of the instrument back panel

LAN connection
Figure E-2 shows a typical wall socket connection to a Local Area Network
(LAN). If you are going to connect the instrument to a LAN, you will need
access to this type of socket.

Figure E-2: Wall socket LAN connection indicated by an arrow.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 101

Appendix E: Instrument Connectivity Components

Computer connections
Computer connections are made via the Ethernet or USB port. Figure E-3
shows these ports on a standard laptop computer. Connecting to a LAN on
page 104 and Connecting via Ethernet When Not on a LAN on page 109
describe instrument connections made via the Ethernet port. Connecting
via USB on page 107 describes connections made via the USB port.

Ethernet Port USB Ports

Figure E-3: Ethernet and USB ports on the computer.

Crossover cable

Note: Many newer computers will automatically detect the Ethernet cable and
adjust to the requirements of the interface, whether it is a switch or
another computer. This allows using a standard Ethernet cable for the
connection between two computers.

A crossover cable can be used to make a direct connection from the

instrument to an Ethernet port on a computer or to an Ethernet to USB
adapter. Please note that the crossover cable shipped with Wyatt
Technology instruments is yellow to distinguish it from a standard
Ethernet cable. Please be careful to only use the yellow crossover cable
where indicated.

Figure E-4: The Ethernet crossover cable shipped by Wyatt Technology is yellow.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 102

Appendix E: Instrument Connectivity Components

Ethernet cable
A standard Ethernet cable is sometimes referred to as a patch cable, or a
straight-through cable to distinguish it from the crossover cable. Ethernet
cables provided by Wyatt Technology are black, blue, white, or gray, but
never yellow (yellow is reserved for the crossover cable). For these
instructions, the Ethernet cable will always be black.

Figure E-5: Standard Ethernet cable.

Ethernet to USB adapter

This device can be used to connect an Ethernet cable to a USB port on the
computer. Using this adapter, it is possible to have the computer
connected to a LAN via the computer’s Ethernet port, and the instruments
connected to the computer via USB. The Ethernet to USB adapter
supplied by Wyatt Technology will look similar to this. The first time you
connect an Ethernet to USB adapter to your computer, you may be
prompted to install USB drivers for the device. To do so, follow the
onscreen instructions.
Ethernet USB Connector
Port

Figure E-6: Standard Ethernet to USB adapter. The Ethernet cable is plugged into
the Ethernet port (shown with the arrow) and the USB connector is
plugged into a USB port on the computer.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 103

Appendix E: Instrument Connectivity Connecting to a LAN

Ethernet switch
Ethernet switches are used to connect several Ethernet cables to one
resource, such as the LAN socket in Figure E-2. The Ethernet switch
supplied by Wyatt Technology will look similar to the eight-port switch
shown below. Please note that although Ethernet cables can be connected
to the switch in any order or position, best practice is to use the Uplink
port to connect to a LAN while leaving port 8 empty. Also, the switch has
an external AC adapter (not shown) to provide power to the switch.

Figure E-7: Eight-port Ethernet switch.

Connecting to a LAN
If an instrument is connected to a LAN, it can be accessed by any
computer plugged into the same LAN.
The following sections describe various configurations for connecting one
or more instruments to a LAN and possibly to a computer also. (For
example, to a computer running ASTRA software.)
These sections use a LAN wall socket like the one in Figure E-2.

One Instrument to LAN

Plug the instrument into a LAN wall socket using a standard Ethernet
cable (Figure E-8). The computer that is to communicate with the
instrument must be on the same LAN.

Figure E-8: Connection for one instrument to LAN

Optilab and microOptilab User’s Guide (M1520 Rev. A) 104

Appendix E: Instrument Connectivity Connecting to a LAN

One Instrument and Computer to LAN

If there is only one LAN wall socket available for both the instrument and
computer, it is necessary to use an Ethernet switch (Figure E-9) to connect
both the computer and instrument to the LAN. In this configuration, the
computer can access the LAN and the instrument, and the instrument can
be accessed from any other computer on the LAN.

Figure E-9: Instrument and computer connected to LAN via Ethernet switch

Multiple Instruments to LAN

If there is only one LAN wall socket available, two or more instruments
can be connected to the LAN via an Ethernet switch (Figure E-10). The
instruments can be accessed via any computer on the LAN.

Figure E-10: Two instruments connected to LAN via an Ethernet switch

Optilab and microOptilab User’s Guide (M1520 Rev. A) 105

Appendix E: Instrument Connectivity Connecting to a LAN

Multiple Instruments and Computer to LAN

If there is only one LAN wall socket available for multiple instruments
and a computer, it is necessary to use an Ethernet switch to connect both
the computer and instruments to the LAN. In this configuration, the
computer can access the LAN and the instruments, and the instruments
can be accessed from any other computer on the LAN.

Figure E-11: Two instruments and computer to LAN via an Ethernet switch

Optilab and microOptilab User’s Guide (M1520 Rev. A) 106

Appendix E: Instrument Connectivity Connecting via USB

Connecting via USB

If it is not possible or desired to have the instruments connected to a LAN,
you can connect to the instruments via USB. In this way, the instruments
can be isolated from the LAN, even while the computer maintains its own
Ethernet connection with the LAN.
You may be prompted to install drivers for the Ethernet to USB adapter
the first time it is plugged into the computer. To install the drivers, insert
the CD that came with the adapter and follow the Windows instructions.

One Instrument to USB via a Crossover Cable

Note: Many newer computers will automatically detect the Ethernet cable and
adjust to the requirements of the interface, whether it is a switch or
another computer. This allows using a standard Ethernet cable for the
connection between two computers.

Connect the yellow crossover cable (Figure E-4) from the instrument to the
Ethernet to USB adapter (Figure E-6). Plug the Ethernet to USB adapter
into an available USB port on the computer.

Figure E-12: One instrument to USB via yellow crossover cable

Optilab and microOptilab User’s Guide (M1520 Rev. A) 107

Appendix E: Instrument Connectivity Connecting via USB

One Instrument to USB Using an Ethernet Switch

Connect the instrument to the Ethernet switch using a standard Ethernet
cable (Figure E-5). Then connect the Ethernet switch to the Ethernet to
USB adapter using a standard Ethernet cable. Plug the Ethernet to USB
adapter into an available USB port on the computer.

Figure E-13: Connecting one instrument to USB using an Ethernet switch

Multiple Instruments to USB

Two or more instruments can be connected to USB using an Ethernet
switch. Use a standard Ethernet cable to plug each instrument into the
Ethernet switch. Then connect the Ethernet switch to the Ethernet to
USB adapter using a standard Ethernet cable. Plug the Ethernet to USB
adapter into an available USB port on the computer. You may be
prompted to install drivers for the Ethernet to USB adapter the first time
it is plugged into the computer. To install the drivers, insert the CD that
came with the adapter and follow the Windows instructions.

Figure E-14: Connecting two instruments to USB via Ethernet switch and adapter

Optilab and microOptilab User’s Guide (M1520 Rev. A) 108

Appendix E: Instrument Connectivity Connecting via Ethernet When Not on a LAN

Connecting via Ethernet When Not on a LAN

If the computer is not on the LAN, it is possible to use the Ethernet port
directly to connect to the instruments.

One Instrument to Computer Using Crossover Cable

Note: Many newer computers will automatically detect the Ethernet cable and
adjust to the requirements of the interface, whether it is a switch or
another computer. This allows using a standard Ethernet cable for the
connection between two computers.

Connect the yellow crossover cable from the instrument directly to the
Ethernet port on the computer.

Figure E-15: Connecting one instrument to computer via yellow crossover cable

One Instrument to Computer Using an Ethernet Switch

Connect the instrument to the Ethernet switch using a standard Ethernet
cable. Then connect the switch to the computer Ethernet port using a
standard Ethernet cable.

Figure E-16: Connecting instrument to computer via an Ethernet switch

Optilab and microOptilab User’s Guide (M1520 Rev. A) 109

Appendix E: Instrument Connectivity Instrument Network Settings

Multiple Instruments to Computer Using an Ethernet Switch

Connect each instrument to the Ethernet switch using a standard
Ethernet cable. Then connect the switch to the computer Ethernet port
using a standard Ethernet cable.

Figure E-17: Connecting multiple instruments to computer via Ethernet switch

Instrument Network Settings

In the Network section of the Settings tab on the front panel display
(Network Settings on page 46), there is a choice to enable Obtain IP
Address Automatically, which will use an associated DHCP server. If
this is disabled, you can set a static IP address.
In general, this setting can be left to DHCP. With DHCP, once the
instrument is connected to a computer or LAN, the IP address and subnet
mask will be assigned automatically. This will even work with the USB
connections described in Connecting via USB on page 107.
When using DHCP, it might take several minutes for the IP address to be
assigned. During this time, the IP address and subnet mask will read
0.0.0.0. Once the IP address and subnet mask have been assigned, both
are automatically updated. At this point, it should be possible to connect to
the instrument from the computer.
If you wish to use a static IP address and subnet mask, please contact your
IT department to obtain a valid address and mask.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 110

Appendix E: Instrument Connectivity Accessing Instruments with ASTRA

Accessing Instruments with ASTRA

To access an instrument with ASTRA after you have connected it as
described in this chapter, you may use either the Method Builder or add
the instruments via the System drop down menu.
To use the Method Builder, select System→Method Builder Wizard
and follow the prompts for selecting an appropriate method, adding your
instruments, and inputting parameters. More information about the
Method Builder can be found in the ASTRA User’s Guide.
To add your instruments without the Method Builder, follow these steps:
1. From the main menu of ASTRA, select System→Instruments.
2. In the Instruments dialog, click Add to open the following dialog.

3. Select either Automatic or Manual.

• If using Automatic, click the Search button. Any detectable
Wyatt instruments will be listed. Highlight the desired instrument
and click Add. The selected instrument will then appear in the
Workgroup list in the Instruments dialog.
• If using Manual, add the instrument by name or IP address.
4. To add the instrument by name, type the instrument’s computer name
and click Add. The instrument’s computer name can be found on the
front panel, in the Settings tab under Network.
5. To add the instrument by IP address, type the IP address of the
desired instrument and click Add.
6. It may take several minutes for ASTRA to identify instruments on the
network, and an additional several minutes for the selected instru-
ment to appear in the Workgroup list. Once it is there, select the
instrument by clicking on it, then click the View button. The Diagnos-
tic Manager application should launch, which can be used to verify the
instrument connection.
If it is not possible to connect to an instrument after following these
instructions, read Troubleshooting and Diagnostics on page 112.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 111

Appendix E: Instrument Connectivity Troubleshooting and Diagnostics

Troubleshooting and Diagnostics

If you are experiencing instrument connectivity challenges, please go over
the following steps and consult TN1018: Instrument Connection Guide for
ASTRA in Wyatt Technology’s Customer Support Center. If you still
cannot connect to your instrument, please contact Wyatt Technology
Support at support@wyatt.com for assistance.
Computer Configuration: Please refer to Wyatt Technology's website
for current software and hardware specifications, such as Supported
Microsoft Operating Systems, System Requirements, and Computer
Connections.
ASTRA Settings: If the instrument is not connected to the LAN or you
are using a static IP address, it is critical that you type in the correct IP
address.

Verifying Instrument Connections

If the previous suggestions fail, please verify that the instrument is
communicating with the computer.
Open Windows Command Prompt on the computer. On the command line,
type “ping” plus the IP address of the instrument as shown on the
instrument front panel (see Instrument Network Settings on page 110).
If the instrument is connected properly, the result should be similar to
that shown in Figure E-18.
If the instrument is not connected properly, the result will be similar to
that shown in Figure E-19.

Figure E-18: Using ping to verify the instrument connection

Figure E-19: Failure to connect to instrument using ping

Optilab and microOptilab User’s Guide (M1520 Rev. A) 112

F Warnings

This appendix provides a list of warnings that should be read and

understood when using the Optilab/microOptilab.

WARNING
If the power cord is connected, line voltages of 120 Vac to 240 Vac, 50 Hz to
60 Hz are present within the system even when the power switch is off.
Always disconnect the power cord before opening the instrument cover.

WARNING
High voltage is stored in the instrument power supplies for some time
(hours) after the instrument is switched off and the power cord is
disconnected. Under no circumstances should the power supplies be
accessed by unqualified personnel.

WARNING
The instrument contains fluid. Under normal operating conditions, the
system may contain up to 0.5 mL of fluid introduced into the system by the
user. If a leak develops internal to the instrument, additional fluid may be
present in the system. The system has been designed to bring fluid leaks
to standard locations within the instrument, but there always exists the
possibility of fluid present in non-standard locations. Fluid introduced into
the instrument by the user or its vapors may be hazardous. Safety
precautions appropriate to the fluid within the system should be taken
under the assumptions that the fluid may not reside in standard locations
within the instrument, and may not be contained by the instrument.

Optilab and microOptilab User’s Guide (M1520 Rev. A) 113

Index
A flow cell on-line 69
abbreviations, list of 89 colors, wire 24
absolute RI (aRI) 12 columns, thermal control of 64
calibration constant 52 communication connections 17, 20, 27
measuring 62 computer
offset 52 connections to 17, 20, 27
range and sensitivity 96, 97 software for 20
acronyms, list of 89 condensation, preventing 29
adapter, Ethernet to USB 103 connecting to LAN 101
air intake fan 16 Constants dialog 51
air intake filter, cleaning 77 aRI calibration constant field 52
alarm aRI offset field 52
external 42 crossover cable 102
N2 pressure 42
D
overheat 43
data collection for calibration 56
recycle open 43
deflection based design 91
vapor 43
deflection-based measurement 11
Alarm In signal 25
degassing 65
Alarm Out signal 26
DHCP 110
Analog In signal 26
differential RI (dRI) 12
analog input and output 16, 23
analog out range 50
Analog Out signal 26
calibration constant 51
anhydrous sodium chloride 54
high concentration option 96
aRI. See absolute RI
offset 52
ASTRA software 20, 111
range and sensitivity 96, 97
calibration using 53
setting zero value of 25
collecting data with 56
value at minimum voltage 50
Auto Inject In signal 25
display
auto inject input and output 16, 23
specifications 96, 97
Auto Inject Out signal 27
display. See Multi-touch display
B dn/dc value 53, 61
baseline noise 87 dRI analog out range field 50
beam deflection angle, measuring 93 dRI at min voltage field 50
dRI calibration constant field 51
C dRI measurements
cables methodology for 14
Ethernet 27, 103 reading 14
for communication connections 20 dRI offset field, Constants dialog 52
for signal connectors 23 dRI. See differential RI
calibration 53 dry gas pressure requirements 29
calibration constants dry gas purge port 17
calculating 61 dry nitrogen connection 29
chromatography system 22
cleaning E
eluent, thermal control of 64

Optilab and microOptilab User’s Guide (M1520 Rev. A) 114

Index

environment injector 55
location 21 in-line operation 64
error condition 88 installation
Ethanol, shipped with Optilab 20, 31 Optilab 21
Ethernet installation and setup 19, 21
cable 103 installing software 20
connecting via 109 instrument stability check 32
connector 17, 27, 101 Instruments dialog in ASTRA 111
crossover cable 102
switch 104
K
to USB adapter 103 K5 cell specifications 98
exhaust fan 16 L
F LAN
F2 cell specifications 98 connecting to 104
fans 16 connecting via 109
filtration of sample 65 LCD display
Firmware update 78 specifications for 96, 97
flow cell leaks, fluid
chemical properties 98 alarm for 50
conventional 91 cleaning 80
maintenance 69 liquid leak port for 15
refractive index 98 LED
thermal properties 98 On/Off 37
used by Optilab 91 LED light source
fluid replacing 73
connections 15, 19, 28 See light source
pressure 28 light source
volume specifications 96, 97 Forward Monitor alarm 84
See also sample; solvents replacing 73
fluid leaks specifications for 96, 97
alarm for 50 liquid leak port 15
cleaning 80 liquid leaks 80
liquid leak port for 15 locating instrument 21
warning 113 M
flushing (purging) 31 maintenance
flushing (purging) Optilab 19 flow cell 69
Forward Monitor alarm 84 Optilab 66
front panel 15 Max voltage field, Constants dialog 50
fuses, changing 83 microOptilab
Future use USB port 17 specifications for 97
G Microsoft Windows 112
guard column 65 rebooting 88
Min voltage field, Constants dialog 50
H Multi-touch display 15
HPLC detection
in-line 64
N
off-line 53 nitrogen connection 29
HPLC fittings for fluid connections 19, 28 noise
HPLC pump with injector 55 acceptable levels of 32
baseline, excessive 87
I
ID tubing 55
O
IN port 15, 28, 31 off-line operation 53

Optilab and microOptilab User’s Guide (M1520 Rev. A) 115

Index

Optilab S
calibration of 53 sample
capabilities of 14 preparation of 53, 65
front panel of 15 temperature control range for 96
in-line operation of 64 See also fluid; solvents
installation and setup 19, 21 signal connectors 16, 23
instrument stability check for 32 software
LAN connection 101 ASTRA 100
maintenance of 66 installing 20
off-line operation of 53 types of 20
operating principles 14, 90 solenoid drive output 16, 23
purging (flushing) 19 solvents
rear panel of 16, 23 changing 64
specifications for 96 polarity of 20, 31
thermal control of 64 preparation of 64
OUT port 15, 28, 31 requirements for 65
See also fluid; sample
P
specifications
photodiode array 94
flow cell 98
photodiode, split 93
microOptilab 97
pinging instrument 112
Optilab 96
power connections 17, 19, 23
split photodiode 93
power rating 96, 97
stability check 32
power requirements 19, 23, 96, 97
standard Ethernet cable 103
power switch 16, 30
syringe pump 55
power warm up time 30
System Constants field 51
pressure
system crash 88
back pressure at inlet port 96, 97
dry gas 29 T
fluid 28 temperature
maximum for system 96, 97 default 19
pump for sample 96
HPLC pump with injector 55 setting 19
requirements for 64 will not set below 20 °C 86
syringe pump 55 thermal control of Optilab 64
Purge button, Dashboard tab 31 transformation temperature 99
Purge In signal 25 troubleshooting
Purge mode 19 Forward Monitor alarm 84
purge port, dry gas 17 noisy baseline 87
purging (flushing) 31 temperature will not set below 20 °C
purging (flushing) Optilab 19 86
TTL (Transistor-Transistor Logic) inputs
R
and outputs 16, 23
rear panel 16, 23
tubing
rebooting 31, 88
between injector and Optilab 55
recycle activation 38
for fluid connections 19, 28
Recycle In signal 25
for fluid leaks 15
Recycle Out signal 26
for syringe pump infusion 55
RI measurements
methodology for 91 U
See also aRI; dRI upgrade 78
RJ-12 connectors 16, 23 USB port
pinouts for 23 connecting via 107
signal function for 24 to Ethernet adapter 103

Optilab and microOptilab User’s Guide (M1520 Rev. A) 116

Index

USB port for future use 17 Wavelength field, Settings tab 45

Windows operating system 88, 112
V wire colors 24
ventilation 67 wrist strap 81
W wyatt.com 78
warm up time 19, 22, 30, 67 Z
warnings 113 Zero In signal 25
waste activation 38 Zero selection 20
Waste/Recycle field, Dashboard tab 38 on auto inject signal 48
wavelength
replacing light source 73

Optilab and microOptilab User’s Guide (M1520 Rev. A) 117