Figure 2 Typical sterol structure (sitosterol) with the general reaction scheme for esterification with a fatty acid (linoleate) to the corresponding plant sterol ester.

The analytical methodologies used for sterols/stanols in the past focused on the low levels as found in natural sources. These methods provided detailed information on the composition typical for the plant or animal source. It was used for identification purposes or detection of adulteration (24,25). Most methods as described in normative references are based on an extensive sample clean-up followed by a derivatization step, and finally a

form of chromatography, e.g., the typical sequence of saponification, thin-layer chromatography (TLC), derivatization, and gas chromatography (GC) (26-28). These methods are time consuming and have a limited precision but provide detailed structural information. For low sample numbers this approach proved to be satisfactory. However, some authors looked for faster liquid chromatography (LC) approaches, but at the cost of a less optimal detection compared to GC flame ionization detection (FID) (29-31). Recently, a sample clean-up step, which has been used with success in environmental analysis, proved to be compatible with sterol analysis as well. Carstensen and Schwack used GPC to isolate the sterol-containing fraction from edible oils before a final GC run (32). Alternatively, LC methods are applied to answer very specific situations in the analysis of sterol/stanol epimers (33).