Metrohm 743 Rancimat - Manual (Page 86)

4.6 Determinations ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
78 ￭￭￭￭￭￭￭￭ 743 Rancimat
Note
If the folded filter becomes blocked (e.g. due to the consistency of
the sample material), a Soxhlet apparatus should be used for solid/
liquid separation. You can use up to 40 g of sample material here
per approach.
3 Distillation and filtration
￭ Distill the petroleum ether from the clear, perhaps slightly yellow
extract.
Note
It is safest and easiest if you do this in a rotation evaporator; in a
slight vacuum and at a temperature of +30...35 °C the petroleum
ether can gently and efficiently be removed, protected from direct
light (cover the water bath e.g. with aluminum foil).
￭ Dry the oil/fat sample obtained after completing the distillation:
during around 30 min at a pressure of p < 1330 Pa (13.3 mbar).
￭ Filter the oil/fat sample now present together with Na
2
SO
4
water-free over a folded filter. If necessary, work in the drying
oven at a temperature exceeding the melting point of this fat by
10 °C.
4 Further sample preparation
￭ Treat the isolated oil/fat samples afterwards just as pure oils and
fats.
Note
If the isolated oil/fat samples are not immediately measured out,
you have to store the samples in a cool place and protected
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 preserva-
tion in many cases.
You can find further information on the treatment of oil and fat samples
in Rancidity in Foods, Allen J.C., Hamilton R.J., Applied Science Publish-
ers, London and New York, 1983.