Gas chromatographic-mass spectrometric analyses of cholesterol and its precursors in rat plasma as tert-butyldimethylsilyl derivatives

BackgroundCholesterol and its metabolic precursors occurring in metabolic pathways are important biochemical indicators in pathological conditions.MethodsA method for the simultaneous determination of cholesterol and its metabolic precursors, such as lanosterol and 7-dehydrocholesterol, in rat plasma is demonstrated. It involves their extraction after saponification, followed by conversion to tert-butyldimethylsilyl (TBDMS) derivatives for analysis by gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode (GC-SIM-MS).ResultsThe characteristic fragment ions of [M-57], m/z 443, 483, and 441 permitted the accurate and selective detection of cholesterol and its precursors in rat plasma. The whole procedure of TBDMS derivatization, with subsequent GC-SIM-MS analysis, was linear (r ≥ 0.9994), reproducible (% relative standard deviation = 2.2 to 7.5), and accurate (% relative error = − 5.6 to 7.7), with detection limits of 0.02 to 0.07 ng/ml. Recoveries were measured to be ranged from 89.5 to 95.4%.ConclusionThe present method was useful for the quantification of cholesterol and its precursors in rat plasma samples of 1 µl.