Capillary liquid chromatography combined with tandem mass spectrometry for the study of neurosteroids and oxysterols in brain

Neurosteroids and neurosterols are found in brain at low levels (ng/g–μg/g) against a high background of cholesterol (mg/g). As such their analysis can be challenging. Traditionally, these molecules have been analysed by gas chromatography (GC)–mass spectrometry (MS), however, the absence of molecular ions in GC–MS spectra, even from derivatised molecules, can make the discovery and identification of novel neurosteroids/sterols difficult. To avoid this scenario, liquid chromatography (LC) combined with desorption ionisation methods are employed. In this review we discuss the application of LC–MS and LC–tandem mass spectrometry (MS/MS) for the identification of neurosteroids/sterols, paying particular attention to the use of low-flow-rate LC to maximise chromatographic and mass spectrometric performance.