Thin-layer chromatography/liquid secondary ion mass spectrometry in the determination of major bile salts in dog bile

Positive and negative ion liquid-state secondary-ion mass spectrometry (LSIMS) was applied to several bile acids and bile salts and their spectra were measured directly from the surface of silica gel thin-layer chromatograms. Such spectra were identical to the LSIMS spectra of the pure compound at the same concentration. Three-dimensional ion images were obtained of a model mixture of cholic, chenodeoxycholic and lithocholic acids in both the positive and negative ion modes. A sample of dog bile was prepared, and the bile acids extracted from it were separated by high-performance TLC; TLC/LSIMS spectra were obtained for sodium taurocholate and sodium taurochenodeoxycholate/taurodeoxycholate, the predominant bile salts present. Quantitative estimates of the analytes were obtained by monitoring the ion intensity for the sample spot and a standard spot that had been developed in parallel on the same TLC plate. The concentration of sodium taurocholate in the bile of this particular dog was found to be 38 mg/ml.