AquaLab 4 Series User manual

Water Activity Meter
Operator’s Manual
For Series 4, 4TE, 4TEV, DUO, and TEV DUO
Decagon Devices, Inc.
Version: August 2, 2016 — 09:05:15

AquaLab
Decagon Devices, Inc.
2365 NE Hopkins Court
Pullman WA 99163
Phone: [phone]
Fax: [phone]
Website: www.aqualab.com
Email: [email protected] or [email protected]
Trademarks
AquaLab is a registered trademark of Decagon Devices, Inc.
c
2008-2015 Decagon Devices, Inc.
ii

AquaLab CONTENTS
Contents
1 Introduction 1
1.1 Customer Support . . . . . . . . . . . . . . . . . . . . 1
1.2 About This Manual . . . . . . . . . . . . . . . . . . . 1
1.3 Warranty ......................... 2
1.4 Seller’s Liability . . . . . . . . . . . . . . . . . . . . . . 2
1.5 General Safety Information . . . . . . . . . . . . . . . 3
2 About AquaLab 4
2.1 AquaLab 4 Instrument Specifications . . . . . . . . . . 4
2.2 AquaLab 4 DUO Specifications . . . . . . . . . . . . . 5
2.3 AquaLab Model and Options . . . . . . . . . . . . . . 5
2.4 How AquaLab Works . . . . . . . . . . . . . . . . . . . 6
2.5 AquaLab and Temperature . . . . . . . . . . . . . . . 7
2.6 Chilled Mirror Dew Point Limitations . . . . . . . . . 8
3 Water Activity Theory 9
3.1 Moisture Content . . . . . . . . . . . . . . . . . . . . . 9
3.2 WaterActivity ...................... 9
3.3 Water Potential . . . . . . . . . . . . . . . . . . . . . . 11
3.4 Sorption Isotherms . . . . . . . . . . . . . . . . . . . . 13
4 Getting Started 15
4.1 Components of your AquaLab . . . . . . . . . . . . . . 15
4.2 Choosing a Location . . . . . . . . . . . . . . . . . . . 15
4.3 Preparing AquaLab for Operation . . . . . . . . . . . 16
5 Menus 18
5.1 Measurement Tab . . . . . . . . . . . . . . . . . . . . 18
5.2 Configuration Tab . . . . . . . . . . . . . . . . . . . . 19
5.3 Admin Settings . . . . . . . . . . . . . . . . . . . . . . 24
5.4 DataTab ......................... 28
6 Cleaning and Maintenance 31
6.1 Cleaning the Block Sensors . . . . . . . . . . . . . . . 32
6.2 Cleaning a Series 4TEV . . . . . . . . . . . . . . . . . 33
6.3 Cleaning Procedure: . . . . . . . . . . . . . . . . . . . 33
6.4 Verification of Calibration . . . . . . . . . . . . . . . . 35
iii

CONTENTS AquaLab
7 Verification and Calibration 36
7.1 Water Activity Verification . . . . . . . . . . . . . . . 36
7.2 Verification of Calibration . . . . . . . . . . . . . . . . 37
7.3 Multi-Point Calibration . . . . . . . . . . . . . . . . . 43
7.4 How to Restore Factory Defaults . . . . . . . . . . . . 47
8 Sample Preparation 49
8.1 Preparing the Sample . . . . . . . . . . . . . . . . . . 49
8.2 Samples Needing Special Preparation . . . . . . . . . . 50
8.3 Slow Water-Emitting Samples . . . . . . . . . . . . . . 51
8.4 Volatile Samples . . . . . . . . . . . . . . . . . . . . . 51
8.5 Low Water Activity . . . . . . . . . . . . . . . . . . . 52
8.6 Samples Not at Room Temperature . . . . . . . . . . . 52
9 Taking a Reading 54
9.1 Measurement Steps . . . . . . . . . . . . . . . . . . . . 54
9.2 How AquaLab Takes Readings . . . . . . . . . . . . . 54
10 DUO Operation (Optional) 57
10.1 Obtaining Product Isotherm Models . . . . . . . . . . 58
10.2 Loading and Organizing Product Models . . . . . . . . 58
10.3 Measuring Moisture Content . . . . . . . . . . . . . . 59
10.4 Moisture Content Adjustment . . . . . . . . . . . . . . 62
10.5 How to Adjust for Linear Offset or Create a New
Model Based Off an Old Model . . . . . . . . . . . . . 62
10.6 Restore Moisture Content Settings . . . . . . . . . . . 65
10.7 How to Delete Models . . . . . . . . . . . . . . . . . . 67
11 Computer Interface 69
11.1 AquaLink 4 Software . . . . . . . . . . . . . . . . . . . 69
11.2 AquaLink 4 Part 11 Compatible Software . . . . . . . 70
11.3 Using a Communication Program . . . . . . . . . . . . 70
12 Troubleshooting 72
13 Support and Repair 82
13.1RepairCosts ....................... 83
13.2 Loaner Service . . . . . . . . . . . . . . . . . . . . . . 83
14 Further Reading 84
iv

AquaLab CONTENTS
14.1 Water Activity Theory & Measurement . . . . . . . . 84
15 Appendix A 106
15.1 Preparing Salt Solutions . . . . . . . . . . . . . . . . . 106
16 Appendix B 108
17 Appendix C 109
18 Declaration of Conformity 114
19 Certificate of Traceability 115
v

AquaLab 1 INTRODUCTION
1 Introduction
Welcome to Decagon’s AquaLab Series 4, 4TE, 4TEV, and DUO,
the standard industry devices for measuring water activity (aw).
AquaLab is the quickest, most accurate, and most reliable instrument
available for measuring water activity. Whether you are researching
or working on the production line, AquaLab suits your needs. It is
easy to use and provides accurate and timely results.
1.1 Customer Support
If you ever need assistance with your AquaLab, have any questions
or feedback, there are several ways to contact us. Decagon has Cus-
tomer Service Representatives available to speak with you Monday
through Friday, between 7am and 5pm Pacific time.
Note: If you purchased your AquaLab through a distributor, please
contact them for assistance.
Email:
supp[email protected] or [email protected]
Phone:
1-509-332-5601
Fax:
1-509-332-5158
If contacting us by email or fax, please include as part of your mes-
sage your instrument serial number, your name, address, phone, fax
number, and a description of your problem or question.
1.2 About This Manual
This manual includes instructions for setting up your AquaLab, veri-
fying the calibration of the instrument, preparing samples, and main-
taining and caring for your instrument. Please read these instructions
1

1 INTRODUCTION AquaLab
before operating AquaLab to ensure that the instrument performs to
its full potential.
1.3 Warranty
AquaLab has a 30-day satisfaction guarantee and a one year warranty
on parts and labor. Your warranty is automatically validated upon
receipt of the instrument. We contact our customers within the first
90 days of your purchase to see how the AquaLab is working for you.
1.4 Seller’s Liability
Seller warrants new equipment of its own manufacture against de-
fective workmanship and materials for a period of one year from the
date of receipt of equipment.
Note: We do not consider the results of ordinary wear and tear,
neglect, misuse, accident and excessive deterioration due to corro-
sion from any cause as defects.
The Seller’s liability for defective parts shall in no event exceed the
furnishing of replacement parts Freight On Board the factory where
originally manufactured. Material and equipment covered hereby
which is not manufactured by Seller shall be covered only by the
warranty of its manufacturer. Seller shall not be liable to Buyer for
loss, damage or injuries to persons (including death), or to property
or things of whatsoever kind (including, but not without limitation,
loss of anticipated profits), occasioned by or arising out of the instal-
lation, operation, use, misuse, nonuse, repair, or replacement of said
material and equipment, or out of the use of any method or process
for which the same may be employed. The use of this equipment
constitutes the buyer’s acceptance of the terms set forth in this war-
ranty. There are no understandings, representations, or warranties
of any kind, express, implied, statutory or otherwise (including, but
without limitation, the implied warranties of merchantability and
fitness for a particular purpose), not expressly set forth herein.
2

AquaLab 1 INTRODUCTION
1.5 General Safety Information
Please read through this documentation carefully before putting the
instrument into operation. The documentation contains information
and warnings which the user must follow in order to ensure safe op-
eration. This instrument may only be operated in accordance with
the specifications in this documentation.
This instrument has left the factory in a flawless state in terms of
technical and electrical safety. To maintain this state and ensure
non-hazardous operation of the instrument, the following instruc-
tions must be observed carefully.
1. Only personnel qualified by Decagon Devices are authorized
to carry out service work on the electrical components. When
work is required a Certificate of Calibration will be issued upon
completion of the work.
2. Never remove the housing of the instrument. The instrument
could be damaged by this. There is also a risk of serious injury
if the live components are touched. There are no parts inside
the housing which can be serviced or replaced by the user.
3. An incorrect main power voltage can damage the instrument.
Only operate this instrument with a main power voltage spec-
ified for it (see rear label).
4. This product is grounded through the grounding conductor of
the power cord. To avoid electric shock, the grounding conduc-
tor must be connected to earth ground.
5. Should a fuse need to be replaced. Use only the fuse type and
rating specified for this instrument.
6. If the instrument is used in a manner not specified by the man-
ufacturer, the protection provided by the equipment may be
impaired.
3

2 ABOUT AQUALAB AquaLab
2 About AquaLab
AquaLab is the fastest and most accurate instrument for measuring
water activity, giving readings in five minutes or less. Its readings
are reliable, providing ±0.003 awaccuracy. The instrument is easy
to clean and checking calibration is simple.
Note: UL has listed this product to applicable UL Standards and
Requirements.
2.1 AquaLab 4 Instrument Specifications
Water Activity Range: 0.030 −1.000 aw
Water Activity Accuracy: ±0.003 (4TE Dew Point Mode) and ±0.015
(4TEV Capacitance Mode)
Water Activity Resolution: 0.0001
Read Time1:≤5 min.
Sample Temperature Range: 15 to 50 ◦C
Sample Temperature Accuracy: ±0.2◦C
Sample Temperature Resolution: 0.01 ◦C
Sample Temperature Adjustment Increments: 0.1 ◦C
Sample Dish Capacity: 15 mL Full
Operating Environment: 4 to 50 ◦C; 0 to 90% relative humidity
(non-condensing)
Case Dimensions: 26.7 x 17.8 x 12.7 cm
Weight: 3.1 kg
Case Material: POLYLAC PA-765 (ABS) with fire retardant
Display: 64 x 128 Graphical
1On samples with no significant impedance to vapor loss.
4

AquaLab 2 ABOUT AQUALAB
Data Communications: USB & RS 232 A serial, 9600 to 115200
baud
Power: 110 to 220 VAC, 50/60 Hz
Warranty: One year parts and labor
2.2 AquaLab 4 DUO Specifications
Moisture Content Repeatability: 0.02%
Accuracy to Moisture Content Ref.: 0.1% to 0.5%
2.3 AquaLab Model and Options
Series 4: Uses a chilled-mirror dew point sensor, but lacks the tem-
perature control features found in our premium models.
Series 4TE: User-selectable internal temperature control model,
uses thermoelectric (Peltier) components to maintain internal tem-
perature.
Series 4TEV: Uses both a chilled-mirror dew point sensor and a ca-
pacitance sensor for measuring non-volatile and volatile substances,
respectively. Either sensor is easily selected using the instrument
menu system.
Series 4TE DUO: Uses a chilled-mirror dew point sensor and pro-
grammed models obtained from isotherm data to give the user both
water activity and moisture content simultaneously in five minutes
or less.
Series 4TEV DUO: Uses both a chilled-mirror dew point sen-
sor or capacitance sensor as well as programmed models obtained
from isotherm data to give the user both water activity and mois-
ture content simultaneously for samples containing both non-volatile
and volatile substances.
AquaLab and Water Activity
5

2 ABOUT AQUALAB AquaLab
Water activity (aw) is a measurement of the energy status of the wa-
ter in a system. The value indicates how tightly water is “bound,”
structurally or chemically, within a substance. Water activity is the
relative humidity of air in equilibrium with a sample in a sealed
chamber. The concept of water activity is of particular importance
in determining product quality and safety. Water activity influences
color, odor, flavor, texture and shelf-life of many products. It predicts
safety and stability with respect to microbial growth, chemical and
biochemical reaction rates, and physical properties. For a more de-
tailed description of water activity as it pertains to products, please
refer to Section 3 of this manual, titled “Water Activity Theory.”
2.4 How AquaLab Works
AquaLab uses the chilled-mirror dew point technique to measure the
water activity of a sample. In an instrument that uses the dew point
technique, the sample is equilibrated with the head-space of a sealed
chamber that contains a mirror and a means of detecting conden-
sation on the mirror. At equilibrium, the relative humidity of the
air in the chamber is the same as the water activity of the sample.
In the AquaLab, the mirror temperature is precisely controlled by
a thermoelectric (Peltier) cooler. Detection of the exact point at
which condensation first appears on the mirror is observed with a
photoelectric cell. A beam of light is directed onto the mirror and
reflected into a photo detector cell. The photo detector senses the
change in reflectance when condensation occurs on the mirror. A
thermocouple attached to the mirror then records the temperature
at which condensation occurs. AquaLab then signals you by beeping
and displays the final water activity and temperature.
In addition to the technique described above, AquaLab uses an inter-
nal fan that circulates the air within the sample chamber to reduce
equilibrium time. Since AquaLab measures both dew point and sam-
ple surface temperatures simultaneously, it eliminates the need for
complete thermal equilibrium, thereby reducing measurement times
to less than five minutes for most samples. The AquaLab 4TEV and
4TEV DUO both use a capacitance humidity sensor to measure the
6

AquaLab 2 ABOUT AQUALAB
water activity of a sample. The sensor is suspended in the headspace
of the chamber and uses a special polymide material sandwiched be-
tween two electrodes to sense humidity changes. The sensor converts
the humidity value into a specific capacitance, which is then mea-
sured electronically by the circuit. This signal is then translated by
the software and displayed as water activity on the instrument screen.
At equilibrium, the relative humidity of the air in the chamber is the
same as the water activity of the sample.
2.5 AquaLab and Temperature
Samples not read at room temperature during the read cycle equili-
brate with the AquaLab temperature before the water activity dis-
plays. Large temperature differences cause longer reading times,
since the Series 4 does not make a complete and accurate reading un-
til the sample and the instrument equilibrate to ±4◦C of each other.
There are several advantages in having a temperature-controlled wa-
ter activity meter. A few major reasons are:
1. Research purposes. Researchers can use temperature con-
trol to study the effects of temperature on the water activity of
a sample, make a comparison of the water activity of different
samples independent of temperature, and conduct accelerated
shelf-life studies or other water activity studies where temper-
ature control is critical. There are many shelf-life, packaging,
and isotherm studies in which temperature control would be
very beneficial. (see Section 14 for further resources)
2. Compliance with government or internal regulations for
specific products. Though the water activity of most products
varies by less than ±0.002 per ◦C, some regulations require
measurement at a specific temperature. The most common
specification is 25 ◦C, though 20 ◦C is sometimes indicated.
3. Minimization of extreme ambient temperature fluctu-
ations. If the environmental and AquaLab temperatures fluc-
tuate by as much as ±5◦C daily, water activity readings vary
by ±0.01 aw. Temperature control eliminates variations due to
changes in ambient conditions.
7

2 ABOUT AQUALAB AquaLab
Series 4TE/4TEV/4TE-DUO
The AquaLab Series 4TE models have thermoelectric components
installed to allow the instrument to maintain a set chamber temper-
ature. Customers can set the temperature using the Configuration
tab of any of the Series 4TE models.
2.6 Chilled Mirror Dew Point Limitations
AquaLab limitation is its ability to accurately measure samples with
high concentrations (typically >1%) of certain volatiles such as
ethanol or propylene glycol, which can condense on the surface of
the chilled mirror. The extent of the effect is determined by how
readily the material volatilizes, which is both concentration and ma-
trix dependent. Therefore, even if your sample contains materials
that could volatilize, it may still be possible to make accurate read-
ings using the chilled mirror dew point sensor.
AquaLab Series 4TEV which incorporates both a chilled mirror sen-
sor and a capacitance sensor for measuring volatile substances is
Decagon’s solution for products containing volatile materials. If you
are unsure if you need the TEV model, please call and discuss your
product with a Decagon Representative. Refer to the Section 8 sec-
tion titled “Volatile Samples” or contact Decagon for more details.
8

AquaLab 3 WATER ACTIVITY THEORY
3 Water Activity Theory
Water is a major component of foods, pharmaceuticals, and cosmet-
ics. Water influences the texture, appearance, taste and spoilage of
these products. There are two basic types of water analysis: moisture
content and water activity.
3.1 Moisture Content
The meaning of the term moisture content is familiar to most people.
It implies a quantitative analysis to determine the total amount of
water present in a sample. There are two primary methods for deter-
mining moisture content: loss on drying and Karl Fisher titration,
but you can also use secondary methods such as infrared and NMR.
Moisture content determination is essential in meeting product nu-
tritional labeling regulations, specifying recipes and monitoring pro-
cesses. However, moisture content alone is not a reliable indicator for
predicting microbial responses and chemical reactions in materials.
The limitations of moisture content measurement are attributed to
differences in the intensity with which water associates with other
components.
3.2 Water Activity
Water activity is a measure of the energy status of the water in a
system, and thus is a far better indicator of perishability than water
content. Figure 1 shows how the relative activity of microorganisms,
lipids and enzymes relate to water activity. While other factors, such
as nutrient availability and temperature, can affect the relationships,
water activity is the best single measure of how water affects these
processes. Researchers measure the water activity of a system by
equilibrating the liquid phase water in the sample with the vapor
phase water in the headspace and measuring the relative humidity
of the head-space. In the AquaLab, you place a sample in a sam-
ple cup that seals inside the sample chamber. Inside the sample
chamber is a fan, a dew point sensor, a temperature sensor, and an
infrared thermometer. The dew point sensor measures the dew point
9

3 WATER ACTIVITY THEORY AquaLab
Figure 1: Water Activity Diagram adapted from Labuza
temperature of the air in the chamber, and the infrared thermome-
ter measures the sample temperature. From these measurements,
the relative humidity of the head-space is computed as the ratio of
dew point temperature saturation vapor pressure to saturation vapor
pressure at the sample temperature. When the water activity of the
sample and the relative humidity of the air are in equilibrium, the
measurement of the head-space humidity gives the water activity of
the sample. The purpose of the fan is to speed equilibrium and to
control the boundary layer conductance of the dew point sensor.
In addition to equilibrium between the liquid phase water in the
sample and the vapor phase, the internal equilibrium of the sample
is important. If a system is not at internal equilibrium, one might
measure a steady vapor pressure (over the period of measurement)
which is not the true water activity of the system. An example of this
might be a baked good or a multi-component food. Initially out of
the oven, a baked good is not at internal equilibrium; the outer sur-
face is at a lower water activity than the center of the baked good.
One must wait a period of time in order for the water to migrate
and the system to come to internal equilibrium. It is important to
remember the restriction of the definition of water activity to equi-
librium.
10

AquaLab 3 WATER ACTIVITY THEORY
Temperature Effects
Temperature plays a critical role in water activity determination.
Most critical is the measurement of the difference between sample
and dew point temperature. If this temperature difference were in
error by 1 ◦C, an error of up to 0.06 awcould result. In order
for water activity measurements to be accurate to 0.001, tempera-
ture difference measurements need to be accurate to 0.017 ◦C. The
AquaLab infrared thermometer measures the difference in temper-
ature between the sample and the block. It is carefully calibrated
to minimize temperature errors, but achieving 0.017 ◦C accuracy is
difficult when temperature differences are large. Best accuracy is
therefore obtained when the sample is near chamber temperature.
Another effect of temperature on water activity occurs when sam-
ples are near saturation. A sample that is close to 1.0 awand is
only slightly warmer than the sensor block condenses water within
the block. This causes errors in the measurement, and in subsequent
measurements until the condensation disappears. A sample at 0.75
awneeds to be approximately 4 ◦C above the chamber temperature
to cause condensation. The AquaLab warns the user if a sample is
more than 4 ◦C above the chamber temperature, but for high water
activity samples the operator needs to be aware that condensation
can occur if a sample that is warmer than the block is put in the
AquaLab.
3.3 Water Potential
Some additional information may be useful for understanding what
water activity is and why it is such a useful measure of moisture
status in products. Water activity is closely related to a thermody-
namic property called the water potential, or chemical potential (µ)
of water, which is the change in Gibbs free energy (∆G) when water
concentration changes. Equilibrium occurs in a system when (µ) is
the same everywhere in the system. Equilibrium between the liquid
and the vapor phases implies that (µ) is the same in both phases. It
is this fact that allows us to measure the water potential of the va-
11

3 WATER ACTIVITY THEORY AquaLab
por phase and use that to determine the water potential of the liquid
phase. Gradients in (µ) are driving forces for moisture movement.
Thus, in an isothermal system, water tends to move from regions of
high water potential (high aw) to regions of low water potential (low
aw). Water content is not a driving force for water movement, and
therefore can not be used to predict the direction of water movement,
except in homogeneous materials.
Factors In Determining Water Activity
The water activity of the water in a system is influenced by factors
that effect the binding of water. They include osmotic, matric, and
pressure effects. Typically water activity is measured at atmospheric
pressure, so only the osmotic and matric effects are important.
Osmotic Effects: Osmotic effects are well known from biology and
physical chemistry. Water is diluted when a solute is added. If
this diluted water is separated from pure water by a semi-permeable
membrane, water tends to move from the pure water side through
the membrane to the side with the added solute. If sufficient pressure
is applied to the solute-water mixture to just stop the flow, this pres-
sure is a measure of the osmotic potential of the solution. Addition
of one mole of an ideal solute to a kilogram of water produces an
osmotic pressure of 22.4 atm. This lowers the water activity of the
solution from 1.0 to 0.98 aw. For a given amount of solute, increasing
the water content of the systems dilutes the solute, decreasing the
osmotic pressure, and increasing the water activity. Since microbial
cells are high concentrations of solute surrounded by semi-permeable
membranes, the osmotic effect on the free energy of the water is im-
portant for determining microbial water relations and therefore their
activity.
Matric Effects: The sample matrix affects water activity by phys-
ically binding water within its structure through adhesive and cohe-
sive forces that hold water in pores and capillaries, and to particle
surfaces. If cellulose or protein were added to water, the energy sta-
tus of the water would be reduced. Work would need to be done to
extract the water from this matrix. This reduction in energy status
12

AquaLab 3 WATER ACTIVITY THEORY
of the water is not osmotic, because the cellulose or protein concen-
trations are far too low to produce any significant dilution of water.
The reduction in energy is the result of direct physical binding of
water to the cellulose or protein matrix by hydrogen bonding and
van der Waal forces. At higher water activity levels, capillary forces
and surface tension can also play a role.
3.4 Sorption Isotherms
Relating Water Activity to Water Content
Changes in water content affect both the osmotic and matric binding
of water in a product. Thus a relationship exists between the water
activity and water content of a product. This relationship is called
the sorption isotherm, and is unique for each product. Besides being
unique to each product, the isotherm changes depending on whether
it was obtained by drying or wetting the sample. These factors need
to be kept in mind if one tries to use water content to infer the
stability or safety of a product. Typically, large safety margins are
built into water content specifications to allow for these uncertainties.
While the sorption isotherm is often used to infer water activity
from water content, one could easily go the other direction and use
the water activity to infer the water content. This is particularly at-
tractive because water activity is much more quickly measured than
water content. This method gives particularly good precision in the
center of the isotherm. In order to infer water content from water
activity, one needs an isotherm for the particular product. Decagon
sells an Isotherm Generator called the AquaLab Vapor Sorption An-
alyzer (VSA) or you can also have Decagon run the isotherm for a fee.
For example, if you were using the AquaLab to monitor the water
content of dried potato flakes, you would measure the water activity
and water content of potato flakes dried to varying degrees using the
standard drying process for those flakes. You could then use that
data to construct an isotherm and infer the water content using the
measured water activity of samples and that isotherm. Decagon has
an upgrade available to Series 4TE users that would allow you to
13

3 WATER ACTIVITY THEORY AquaLab
determine moisture content and water activity simultaneously. This
instrument is called the Series 4TE DUO.
We cannot overemphasize the importance of the concept of water
activity for foods, pharmaceuticals, and cosmetics. Water activity
is a measure of the energy status of the water in a system. More
importantly, the usefulness of water activity in relation to microbial
growth, chemical reactivity, and stability over water content has been
shown.
14

AquaLab 4 GETTING STARTED
4 Getting Started
4.1 Components of your AquaLab
Your AquaLab should have been shipped with the following items:
•AquaLab water activity meter
•Calibration certificate
•Power cord
•USB interface cable
•50 disposable sample cups
•Operator’s Manual
•Quick Start Guide
•Cleaning kit
•Two vials each of the following verification solutions:
1.00 awUSP Purified Water
0.984 aw0.50 mol/kg KCl
0.920 aw2.33 mol/kg NaCl
0.760 aw6.00 mol/kg NaCl
0.500 aw8.57 mol/kg LiCl
0.250 aw13.41 mol/kg LiCl
•AquaLink 4 Software Package
4.2 Choosing a Location
To ensure that your AquaLab operates correctly and consistently,
place it on a level surface. This reduces the chance of spilling sam-
ple material and contaminating the sample chamber. Also select a
location where the temperature remains fairly stable to avoid tem-
perature changes that can affect accuracy. This location should be
well away from air conditioner and heater vents, open windows, etc.
Place the AquaLab in a location where cleanliness can be maintained
to prevent contamination of the sample chamber.
15