Metrohm 892 Professional Rancimat - Manual (Page 40)

4.3 Determinations
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892 Professional Rancimat
NOTE
In order to carry out at least one double determination on the 892
Professional Rancimat, you have to extract approx. 10 g pure oil or
fat, allowing for a certain transfer loss (for more than two determi-
nations, an accordingly higher amount is necessary).
￭ Prepare a clean 250 mL round-bottom flask with standard
ground-joint and a folded filter.
￭ Filtrate, if possible protected from light. Rewash the residue with
a little petroleum ether.
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 per
batch.
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 rotary evaporator; in a
slight vacuum, protected from direct light (cover the water bath
e.g. with aluminum foil) and at a temperature of +30 - 35 °C the
petroleum ether can gently and efficiently be removed.
￭ Dry the oil/fat sample after the distillation has been completed for
approx. 30 min at a pressure of < 1,330 Pa (13.3 mbar).
￭ Filtrate the oil/fat sample now present together with water-free
Na
2
SO
4
with 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.