QUANTIFICATION OF CHOLESTEROL TRACERS BY GAS CHROMATOGRAPHY-NEGATIVE ION CHEMICAL-IONIZATION MASS-SPECTROMETRY

Because of its high sensitivity, gas chromatography negative ion chemi cal ionization mass spectrometry (GC-NCI-MS) is a potentially valuable analytical tool for the study of cholesterol metabolism, Of several d erivatives prepared for potential use in tracer studies pentafluoroben zoyl cholesterol was selected because it formed rapidly at ambient tem perature and was stable for long periods, could be detected at a level of 1 fmol, and yielded a mass spectrum in which the molecular ion was the principal component, Hexadeuterated cholesterol tracer ([26,26,26 ,27,27,27-H-2(6)]cholesterol) could be detected in dilutions up to 270 0 in unlabeled cholesterol by selected ion monitoring with a coefficie nt of variation averaging 3.2%, In seven normal subjects tracer choles terol was infused intravenously and plasma cholesterol enrichment was determined after 4 h. The measured rapidly miscible cholesterol pool w as 391.0 +/- 38.6 mg cholesterol/kg, Negative ion mass spectrometry of pentafluorobenzyol cholesterol will facilitate analysis of both small amounts of natural cholesterol and labeled cholesterol in application s where sensitivity is critical.