Quantitative isolation and gas–liquid chromatographic analysis of total fecal bile acids

Abstract

A method for isolation and quantification of fecal bile acids is described which allows sterol balance studies to be made in man or in small laboratory animals without requiring the use of radioisotopes in vivo. Bile acids are purified by column and thin-layer chromatography, converted to the trimethylsilyl ethers of their methyl esters, and quantified by GLC with detection by hydrogen flame ionization. Recoveries are complete when internal standard corrections are applied, with an error <±3%. The claim that the final fecal bile acid fraction accounts for all the bile acids and nothing but bile acids is validated in several ways. The sensitivity is such that fecal aliquots containing as little as 50 μg of mixed bile acids can be analyzed accurately, but the procedure lends itself well to preparative scale work for more definitive study of individual bile acids.After oral administration of cholic-24-C14 and chenodeoxycholic-24-C14 acids to one patient, 98% of the administered radioactivity was excreted in the bile acid fraction of the fecal extracts over a period of 38 days, and 2% in the urine. This experiment indicated the stability of bile acid structure during intestinal transit and provided additional evidence for the completeness of the described method of determining fecal bile acids.