EVALUATION OF PARTICLE-BEAM HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY FOR ANALYSIS OF CHOLESTEROL OXIDES

The capabilities of using particle beam (PB) liquid chromatography-mas s spectrometry (LC-MS) was investigated for the analysis of cholestero l and oxycholesterols; normal-phase (NP) and reversed-phase (RP) chrom atographic methods making use of narrow-bore columns were set up for t he simultaneous separation of these compounds. The influence of PB int erface parameters, LC conditions (solvent composition and flow-rate) a nd MS conditions was explored. PB mass spectra were recorded in electr on impact (EI), positive-ion chemical ionization (PCI) and negative-io n chemical ionization (NCI) modes and the corresponding spectral data discussed. Better performance in terms of ion abundance were observed in EI mode both under NP and RP conditions. Using EI source and operat ing in selected-ion monitoring (SIM) mode, linearity, sensitivity and precision of the analysis were explored. The experimental data fitted a quadratic model in the overall range studied. Using the RP-LC-PB-MS method detection limits at the low-ng level were achieved for all the analytes; in addition, repeatability ranging from 3% for triol to 9% f or cholesterol and 7-ketocholesterol at the 4 ng level was obtained. ( C) 1998 Elsevier Science B.V.