Use of on‐line hydrogen/deuterium exchange to facilitate metabolite identification

An Erratum for this article has been published in Rapid Communications in Mass Spectrometry 17(3) 2003, 264 Biotransformation studies performed on an investigational compound (I, represented by R1‐CH(NH 2 )‐CO‐N(R2)‐CH 2 ‐S‐R3) led to the identification of five metabolites (M1–M5). Based on LC/MS (liquid chromatography/mass spectrometry) analysis which included the use of H 2 O and D 2 O in the mobile phases, they were identified as the sulfoxide (M1), sulfone (M2), carbamoyl glucuronide (M3), N‐glucuronide (M4), and N‐glucoside (M5) metabolites, respectively. The structure of M3, a less commonly seen carbamoyl glucuronide metabolite, was established using on‐line H/D (hydrogen/deuterium) exchange experiments conducted by LC/MS. H/D exchange experiments were also used to distinguish the S‐oxidation structures of M1 and M2 from hydroxylation. Herein, the application of deuterium oxide as the LC/MS mobile phase for structural elucidation of drug metabolites in biological matrices is demonstrated. Copyright © 2001 John Wiley & Sons, Ltd.