Comparison With A Reference Procedure; Handling Samples - KERN DLB-A Operating Manual

13.4 Comparison with a reference procedure

Often legal regulations or sector or company-specific instructions must be observed
when measuring the moisture content of substances. The oven method (weight loss
by drying) or Karl Fischer titration are usually used as a reference method.
However, the use of a moisture analyzer is acceptable if you can demonstrate that
the results obtained using this method are equivalent to those obtained by the oven-
drying method and are equally accurate. To do this, you must create a drying method
for the moisture analyzer and compare this with the oven-drying method over several
sets of analyses.
You should also note that the samples are heated by convection in the drying oven.
This means that the samples need to be at the same temperature as the drying oven.
When a moisture analyzer is used, the sample is heated and dried by absorbing
infrared radiation from the heating element. The temperature and drying time of the
sample depend on its absorption properties.

13.5 Handling samples

Sample material
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Easy to determine are usually samples with the following
characteristics:
• Grainy to powdery, pourable solids
• Thermally stable materials, emitting the moisture to be
determined easily without other substances
evaporating at the same time
• Liquids that vaporize to leave a dry substance without
developing a film
Difficult to determine may be samples that are:
• Viscous or sticky
• Become incrusted easily or tend to form a film
• Decompose easily under the influence of heat or emit
various elements
TDLG_A-BA-e-2011