23
Applying a Sample to the Sample Pan
§ Apply the sample to the sample pan in a thin, even layer
(height: 2 to 5 mm, weight: 5 to15 g); otherwise:
– a sample applied unevenly will result in a non-uniform distribution of heat
– a sample will not be dried completely
– the analysis time will be prolonged unnecessarily
– the sample burns or a crust/ skin forms on its surface as a result of a very thick layer
– the crust makes it difficult or impossible for moisture to escape from the sample
during the drying process
– an uncertain and unknown quantity of moisture remains in the sample
§ Apply liquid samples, pasty samples or samples that can melt to a glass fiber filter
(order no. 6906940); advantages include:
– uniform distribution due to capillary effect
– liquids prevented from beading together and forming drops
– moisture can evaporate faster with larger surfaces
– considerably more convenient than the “sea-sand method”
When drying samples containing sugar, a crust or skin can form and seal the surface.
A glass fiber filter is particularly useful in such cases. The moisture can evaporate
downwards through the surface of the filter. You can prevent or limit crust/skin formation
by placing the glass fiber filter on top of the sample.
§ Cover solid, heat-sensitive samples with a glass fiber filter (order no. 6906940);
advantages include:
– gentle heating; sample surface is shielded from excessive heat
– higher temperature setting can be selected
– uniformity of the sample surface
– faster evaporation of the moisture
– excellent reproducibility for samples containing fat
Preventing the formation of crust/skin
Solvents can be applied to the sample to prevent the formation of crust/skin during anal-
ysis. The solvent applied has no bearing on the final result of an analysis.
§ Re-open the sample chamber within 2 seconds of closing it (after the beep tone).
§ Apply a solvent to the sample
§ Close the sample chamber and start the analysis as usual
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