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

Abstract

BACKGROUND: Cholesterol and its metabolic precursors occurring in metabolic pathways are important biochemical indicators in pathological conditions.

METHODS: A 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).

RESULTS: The 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>or=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%.

CONCLUSION: The present method was useful for the quantification of cholesterol and its precursors in rat plasma samples of 1 microl.