Analysis of acetaminophen glucuronide conjugate accompanied by adduct ion production by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

Liquid chromatography-mass spectrometry (LC-MS) is an effective method for the analysis of polar compounds. A coupling of LG-MS, which is used under conventional conditions, and atmospheric-pressure chemical ionization (APCI), which applies mild ionization for the analysis of water-soluble drug conjugates, would offer a very convenient method. The APCI method is effective for ionizing low- and medium-polarized compounds, but not for highly polarized compounds. In this study, we have tried derivatization of carboxyl group of glucuronic acid, to which direct ionization is difficult to apply under the APCI method, was conducted using glucuronides. Methyl ester derivatives were found to be effectively ionized. Furthermore, acetaminophen glucuronide conjugate was investigated in detail. Methyl ester derivatives of acetarninophen glucuronide conjugate (ACEG) were detected at m/z 373 as O-2 adduct ion [M + O-2](-) in the negative mode, and p-nitrophenyl beta-D-glucuronide (PNPG) demonstrated ionization behaviors very similar to ACEG. Quantitation of ACEG was examined using PNPG as an internal standard, and satisfactory results were obtained for the recovery test and quantification. (C) 2002 Elsevier Science B.V. All rights reserved.