Separatory Determination of Bile Acid 3-Sulfates by Liquid Chromatography/Electrospray Ionization Mass Spectrometry

Abstract

A method for the separatory determination of bile acid 3-sulfates by liquid chromatography (LC)/electrospray ionization (ESI) mass spectrometry (MS) was developed. The sulfates were characterized by an abundant pseudo-molecular ion [M-H]- with a doubly charged ion [M-2H]2-, and the ratio of these negative ions was markedly influenced by an acidic component of salt added to the mobile phase according to the pKa value of the conjugated form at C-24. The resolution into unconjugated and glycine-and taurine-conjugated cholic acid, chenodeoxycholic acid, deoxycholic acid, ursodeoxycholic acid and lithocholic acid 3-sulfates was achieved on a Capcell Pak C18 column with 20 mM ammonium acetate–methanol (10:12, v/v) by selected ion monitoring, monitored with their corresponding pseudo-molecular ions. The combined use of stable isotope-labeled compounds as internal standards in LC/MS was applied to the determination of bile acid 3-sulfates in human urine. © 1997 by John Wiley & Sons, Ltd.