AquaLab 7 VERIFICATION AND CALIBRATION
Table 1: Verification Standards
Verification Standard @ 25
◦
C Dew Point A
w
Capacitive A
w
13.41 mol/kg LiCl 0.250 ±0.003 0.250 ±0.015
8.57 mol/kg LiCl 0.500 ±0.003 0.500 ±0.015
6.00 mol/kg NaCl 0.760 ±0.003 0.760 ±0.015
2.33 mol/kg NaCl 0.920 ±0.003 0.920 ±0.015
0.50 mol/kg KCl 0.984 ±0.003 0.984 ±0.015
USP Purified Water 1.000 ±0.003 1.000 ±0.015
Note: If you need to obtain a Safety Data Sheet (SDS) for any of
these standards, a printable version is available on our website at
http://www.decagon.com/education/safety-data-sheets/.
To use a verification standard, remove the twist top and pour the
contents into an AquaLab sample cup. Information about the stan-
dard value and molality can be found printed on the outside of the
plastic vial. If for some reason you cannot obtain Decagon’s ver-
ification standards and need to make a saturated salt solution for
verification, refer to Appendix A.
In TEV models, the capacitance sensor can hold a memory of high
water activity samples such as USP (United States Pharmacopia
Specifications) Purified Water or the 0.984 a
w
standard. If you verify
calibration with one of these high water activity standards, you must
wait an hour to allow the capacitance sensor and filter to dry before
testing samples of lower water activity or the results may be slightly
high.
Note: To avoid inaccurate water activity readings, verification stan-
dards should be used once immediately after opening and not stored
in sample cups for repeated use.
7.2 Verification of Calibration
When to Verify for Linear Offset
37
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