Determination of underivatised sterols and bile acid trimethyl silyl ether methyl esters by gas chromatography–mass spectrometry–single ion monitoring in faeces

A method for quantification of total faecal sterols and bile acids (BAs) in human stool by using gas chromatography–mass spectrometry–single ion monitoring (GC–MS–SIM) is described. Cholesterol, coprostanol, coprostanone, cholestanol, iso-lithocholic acid (iso-LCA), lithocholic acid (LCA), iso-deoxycholic acid (iso-DCA), deoxycholic acid (DCA), chenodeoxycholic acid (CDCA), cholic acid (CA), and 12-oxo-deoxycholic acid (12-oxo-DCA) in faeces of 86 healthy subjects were determined. The sample preparation for sterol analysis requires hydrolysis and liquid extraction from matrix, but no derivatisation. The GC-flame ionisation detection (FID) and total ion current (TIC) in GC–MS were not sufficient for sterol and BA determination, whereas selectivity and specificity of the GC–MS–SIM ensured the analysis of sterols and BAs in faeces.