To investigate the characteristics of mass spectra of some drug metabolites, solutions of glucuronide conjugates of N
(4 ethoxyphenyl) 2 hydroxyl benzamide (etofesalamide), 4 (3H 1,2 dihydro 1 pyrrolizinone 2 methylamino) benzoic acid, 5 hydroxypropafenone and propafenone were analyzed using
electrospray ion trap mass spectrometry in a multi stage full scan mode performed on a Finnigan LCQ instrument. Sample solutions were directly introduced into the ESI source at a flow rate of 15～30 μl·min -1 by a syringe pump. The mass spectrometer was operated in the negative ion mode. A full scan mass spectra of each analyte provided
quasimolecular ion m/z M-1 , and full scan MS 2 and MS 3 spectra gave characteristic fragment ions m/z 175 and m/z 113, respectively, which were derived from the glucuronate moiety of each analyte. The proposed interpretation of m/z 175 is the negative ion of glucuronic acid with a loss of 18 u (H 2O), which produces m/z 113 after further losing 18 u (H 2O) and 44 u (CO 2). Fragmentation pathway has been established for each analyte. The results show that quasimolecular ion m/z M-1 and the characteristic fragment ions m/z 175 and m/z 113 in the multi stage full scan mass analysis of each analyte can be predicted for future structure elucidation or quantitative determination of glucuronide conjugates by LC/MS.