GC/EI-MS method for the determination of phytosterols in vegetable oils

Sterols are a highly complex group of lipophilic compounds present in the unsaponifiable matter of virtually all living organisms. In this study, we developed a novel gas chromatography with mass spectrometry selected ion monitoring (GC/MS-SIM) method for the comprehensive analysis of sterols after saponification and silylation. A new referencing system was introduced by means of a series of saturated fatty acid pyrrolidides (FAPs) as internal standards. Linked with retention time locking (RTL), the resulting FAP retention indices (RIFAP) of the sterols could be determined with high precision. The GC/MS-SIM method was based on the parallel measurement of 17 SIM ions in four time windows. This set included eight molecular ions and seven diagnostic fragment ions of silylated sterols as well as two abundant ions of FAPs. Altogether, twenty molecular ions of C-27- to C-31-sterols with 0-3 double bonds were included in the final method. Screening of four common vegetable oils (sunflower oil, hemp oil, rapeseed oil, and corn oil) enabled the detection of 30 different sterols and triterpenes most of which could be identified.

Automated summary

A novel GC/MS-SIM method was developed for comprehensive analysis of sterols, using a new referencing system and retention time locking. This method involved measuring multiple SIM ions, including molecular ions of sterols and abundant ions of FAPs. The screening of common vegetable oils enabled the detection and identification of numerous sterols and triterpenes.