Diet, nutrition intake, and metabolism in populations at high and low risk for colon cancer. Amberlite XAD-2 in the determination of human fecal bile acids

A procedure for the isolation and quantification of the major bile acids in human feces is described. The methodology involves the use of a combination of thin-layer chromatographic and gas-liquid chromatographic techniques. Human stools generally contain pigments that interfere with the separation and recovery of steroids. These pigments found in the saponifiable extract were removed in the step preceding thin-layer chromatography by using Amberlite XAD-2 in an unconventional manner. The sample, dissolved in ethyl acetate, was run through a column of Amberlite resin on which the pigments were adsorbed. There was a dramatic improvement in the recovery of the acidic steroids by this technique. Final quantification of the bile acids in the form of their methyl ester trifluoroacetates was carried out by gas-liquid chromatography. The sensitivity of this step is such that 1 microgram of lithocholic acid gave a full-scale deflection.