Metrohm 743 Rancimat - Manual (Page 87)

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743 Rancimat ￭￭￭￭￭￭￭￭ 79
Preparing emulsion fats
You can use water-soluble fats as pure substances and prepare them as
follows:
1 Weigh in the sample
￭ Weigh in the sample.
Note
As the water evaporates right at the beginning of the analysis and
is carried away by the air blown through, you have to use corre-
spondingly more sample material.
2 Mount foam barrier
￭ Mount the foam barrier (see figure 5, page 14), as the samples
can significantly foam.
Note
If the water-soluble fat samples are not immediately measured
out, you need to store the samples in a cool place and protec-
ted from light; for storing the samples, they should be covered
over in their vessels with a nitrogen layer. This type of storage
does not provide complete protection against unintended and
uncontrolled changes in the oxidation stability, but represents a
usable preservation in many cases.
Alternatively you can melt out the emulsion fats (e.g. butter, margarine) at
a temperature, exceeding the melting point of these fats by 10 °C (i.e. at
approx. +50 °C), centrifuge them and pipette off the resultant oil phase.
4.6.2 Preparing the instrument and the accessories
The cleanliness of instrument and accessories is an indispensable prerequi-
site for reliable, reproducible and correct analysis results. Even the
slightest contamination could catalytically accelerate the oxidative decom-
position and lead to completely incorrect results. Therefore always observe
the instructions for use of measuring and reaction vessels in this section.