AquaLab TDL 7 VERIFICATION AND CALIBRATION
order additional standards via sales.food@metergroup.com or 509-
332-5601.
Table 1: Verification Flowchart
Verification Standard @ 25
◦
C Water Activity
17.18 mol/kg LiCl 0.150 ±0.005
13.41 mol/kg LiCl 0.250 ±0.005
8.57 mol/kg LiCl 0.500 ±0.005
6.00 mol/kg NaCl 0.760 ±0.005
2.33 mol/kg NaCl 0.920 ±0.005
0.50 mol/kg KCl 0.984 ±0.005
USP Purified Water 1.000 ±0.005
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://sds.metergroup.com/.
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 METER’s ver-
ification standards and need to make a saturated salt solution for
verification, refer to Appendix A.
7.2 Verification of Calibration
When to Verify for Linear Offset
Linear offset should be checked against two known verification stan-
dards daily, either once per shift or before each use. Linear offset
should never be verified solely against steam distilled water, since
it does not give an accurate representation of the linear offset. For
batch processing, the instrument should be checked regularly against
a known standard of similar water activity. It is also a good idea to
check the offset with a standard of similar water activity when the
general water activity range of your sample is changing. Checking
the water activity of a standard solution alerts you to the possibility
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