LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY DETERMINATION OF PLASMA 24S-HYDROXYCHOLESTEROL WITH CHROMATOGRAPHIC SEPARATION OF 25-HYDROXYCHOLESTEROL

摘要

Concentrations of circulating 24S-hydroxycholesterol are of interest as a practical measure of cholesterol efflux from the human brain. The current method of choice for 24S-hydroxycholesterol quantification is with GC-MS. LC-MS methods to detect 24S-hydroxycholesterol have been described but they lack rigorous HPLC separation of a closely eluting isomeric oxysterol, 25-hydroxycholesterol. This is important as 25-hydroxycholesterol can be present in significant amounts and MS/MS cannot completely differentiate 24S-hydroxycholesterol. We describe an LC-MS method with rapid chromatographic separation of the oxysterols to permit accurate determination of plasma 24S-hydroxycholesterol. The availability of an LC-MS method offers advantages including simplified sample work-up and analysis.