CHARACTERIZATION OF MERCAPTURIC ACIDS BY 3 DIFFERENT MASS-SPECTROMETRIC METHODS

The determination of mercapturic acids, as metabolic end-products of a n important pathway in the biotransformation of xenobiotics, in human urine is becoming a standard tool for the biomonitoring of populations exposed to potential mutagens and carcinogens, Mass spectrometric met hods permit the direct identification and characterization of these su bstances without a previous derivatization step. In this work, N-acety lcysteine conjugates of synthetic origin were characterized by three d ifferent mass spectrometric methods: matrix-assisted laser desorption/ ionization (MALDI) mass spectrometry, positive and negative californiu m-252 plasma desorption mass spectrometry (PD-MS) and fast-atom bombar dment (FAB) mass spectrometry. For PD-MS, samples were prepared by the spin deposition technique on plain aluminium targets, alpha-Cyano-4-h ydroxycinnamic acid and 2,5-dihydroxybenzoic acid were used as MALDI m atrices and glycerol as a matrix for FAB. Complementary structural inf ormation on the N-acetylcysteine moiety and the xenobiotic moiety was obtained through PD-MS and FAB spectra. All three techniques could be used for relative molecular mass determination. The spectra exhibited protonated molecules [M + H](+) or [M + Na](+) ions with high abundanc e. MALDI was the most sensitive among the three tested methods. (C) 19 97 by John Wiley & Sons, Ltd.