A Simplified Method of Quantitating Selected Bile Acids in Human Stool by Gas ChromatographyMass Spectrometry with a Single Extraction and One-Step Derivatization. Supplement: The Unusual Mass Spectral Behavior of Silylated Chenodeoxycholic Acid - Abstract
A method for quantitating selected bile acids in human stool was developed for lithocholic acid (LCA), cholic acid (CA), deoxycholic acid (DCA), chenodeoxycholic acid (CDCA), and ursodeoxycholic acid (UDCA), using D5-chenodeoxycholic acid (D5-CDCA) as an internal standard. The method is a three step process: extraction with hot pyridine and hydrochloric acid, extraction into diethyl ether, and derivatization (silylation) with BSTFA/TMCS. The extracts were analyzed by GC-MS operating in selected ion monitoring (SIM) mode. Separation was achieved with an Rtx-50 column followed by an Rtx-5MS column. The LDR (linear dynamic range) was 0.25 to 5.00 µmol/g. The lower limit of quantitation (LOQ) and the detection limit was 0.25 µmol/g. Interday and intraday precision were good, with most CVs less than 5%; Interday and intraday relative recoveries were also good, with most relative recoveries being between 90 and 110%. Interday precision and accuracy were similar without an internal standard.