Determination of stigmasterol and cholesterol oxides using atmospheric pressure chemical ionization liquid chromatography/mass spectrometry

A new sensitive HPLC–MS method for the detection of sterol oxidation products was developed. The method was developed and optimized with commercially available cholesterol oxidation products. MS detection was carried out with an ion-trap mass spectrometer using atmospheric pressure chemical ionization in positive ion mode. With this new method, both primary and secondary oxidation products of cholesterol and stigmasterol, including epoxides, could be detected. Applicability of the method was investigated using thermo-oxidized (180 °C) stigmasterol as a model compound. Formation and degradation of two hydroperoxides were observed and formation of eight secondary oxidation products quantitatively determined. In conclusion, this method proved to be a powerful tool for investigating oxidation mechanisms of sterols.