The content and composition of the sterol fraction is an important indicator of the value of vegetable oils, mainly due to the cholesterol-lowering effect of certain sterol compounds. Although many methods have been described in the literature, various steps may still cause errors during sample preparation. The present article covers some of the key steps in sterol analysis that are necessary to consider while implementing these procedures in laboratory and when dealing with different types of oils. The importance of the right solvents and the amount and concentration of the alkali solution is explained. The variation between results of analysing underivatized sterols compared to the derivatized ones is discussed. In our experiment with various rapeseed oil samples, the underivatized sterols resulted in lower values (9–11%). This outcome enables to (re)evaluate previous results. We also proposed fast and easy check-up methods for several sample preparation steps in order to avoid deviation in results and possible damage to GC apparatus.
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