Comparison of the Determination of Eight Cholesterol Oxides in Dry-Cured Shoulder by GC-FID, GC-MS, and GC Tandem Mass Spectrometry

The analysis of eight cholesterol oxidation products: 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, alpha-epoxycholesterol, beta-epoxycholesterol, 20 alpha-hydroxycholesterol, cholestanetriol, 25-hydroxycholesterol, and 7-ketocholesterol in dry-cured shoulder was carried out. The extraction of lipids was performed by using the Bligh and Dyer method (1959). Interferences were removed by solid-phase extraction (SPE) in two steps with silica and aminipropylsilica SPE columns. The separation of the eight cholesterol oxidation products was done by gas chromatography, and the detection was performed by flame ionization detection (FID) and mass spectrometry (MS). The results obtained from the use of both systems of detection were compared. The results showed that gas chromatography-mass spectrometry (GC-MS) was the most suitable technique to obtain reliable quantitative data, and significant differences (p < 0.05) between FID and MS determining 7 alpha-hydroxycholesterol, 20 alpha-hydroxycholesterol, and 25-hydroxycholesterol were observed. For the determination of cholesterol oxidation products, it was necessary to apply gas chromatography-tandem mass spectrometry to increase the sensitivity and to avoid interference from other compounds.