LC-MS determination of sterols in olive oil

Sterols in olive oils have been analyzed by liquid chromatography coupled to mass spectrometry with atmospheric-pressure chemical ionization in positive-ion mode. A simple procedure based on saponification and extraction of the compounds from olive oils was studied. Validation of the method included calibration and determination of recovery and repeatability was carried out. Good linearity was obtained up to 100 mg kg(-1) for all the sterols studied except beta-sitosterol, for which linearity was obtained up to 2,000 mg kg(-1). Recovery ranged from 88 to 110%, detection limits from 0.9 to 3.1 mg kg(-1) and precision was good. The method has been successfully used for analysis of sterols in different types of oil. The predominant sterol was beta-sitosterol; other minor components, for example sitostanol and cholesterol, were also detected. Total sterol content depended on the type of oil, and ranged from 687 to 2,479 mg kg(-1). Stigmasterol and the amount of erythrodiol plus uvaol can be used to distinguish between olive oil and seed oil.