Isotope-ratio-monitoring gas chromatography-mass spectrometry

RECEIVED for review February 21, 1978. Accepted June 19, 1978. NMR spectra since two distinct peaks (6 -3.38, 3.78 ppm) caused by these protons are observed in CDCA vs. only one peak (6 -3.45 ppm) caused by the same protons in UDCA. T h e fingerprint region of the spectrum (6 1-2.5 ppm) and the relative position of the CIS methyl peak with respect to tha t of the doublet caused by the Cpl methyl group provide additional confirmation of the identity of the particular epimer. Accurate quantitative results are obtained from careful integration of the C3 and C7 methine proton peaks. The specific method of identification and quantitation described in this report provides an efficient alternative to the rather nonspecific identification and assay procedures by conventional techniques, some of which involve making derivatives of the bile acid epimers. This paper, which is the first publication of its kind dealing with the quantitation of

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