10 DUO OPERATION (OPTIONAL) AquaLab
now appears in the upper right column on the detailed information
screen.
10.4 Moisture Content Adjustment
The AquaLab DUO calculate moisture content values based on water
activity readings by utilizing models stored within the instrument.
Because moisture content results vary between reference methods,
it is important to ensure that the model in the instrument corre-
lates well with your reference method moisture contents (i.e. Karl
Fischer titration, oven loss on drying, etc.). Moisture content dif-
ferences among various methods are usually linear and can be easily
corrected with a linear offset. Therefore, if moisture contents calcu-
lated with the AquaLab DUO instrument are not agreeing with your
reference method, the problem can likely be addressed by adjusting
a linear offset.
When to Adjust for Linear Offset
Reference methods can differ between labs, so it is a good idea to
check for a linear offset upon receipt of a new isotherm model from
Decagon. In addition, the linear offset should be adjusted if moisture
contents being calculated by the AquaLab DUO instrument are con-
sistently higher or lower for a product than your reference method
values over several samples.
10.5 How to Adjust for Linear Offset or Create a New
Model Based Off an Old Model
1. For the product whose model is to be offset, collect three sub-
samples for analysis.
2. Use two of the subsamples to determine duplicate reference
method moisture contents and then combine to determine the
average moisture content.
3. Once you have obtained a reference moisture content, navi-
gate to the Calibration screen in the Configuration tab of the
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