Olive oil, eggs, margarine, soybean oil, and chocolate are a few of the foods that contain sterols, which occur naturally in plants and animals, and are ingested as part of the diet. These compounds perform many roles in human, such as various cellular functions and as precursors to several hormones and vitamins. Sterols of interest include brassicasterol, campesterol, cholestanol, cholesterol, coprostanol, desmosterol, ergosterol, lanosterol, b-sitosterol, and stigmasterol.

Fats in a sample typically must be extracted and saponified to isolate the sterols, which will be in the non-saponifiable fraction, along with other large molecular weight alcohols, fat-soluble vitamins, and hydrocarbons. Vegetable oils, which are almost pure fat, do not require extraction prior to saponification. The general saponification procedure outlined by the AOAC Method 970.51 is useful for preparing most samples. Analysis by GC can typically be performed without derivatization.