Mass spectrometric and tandem mass spectrometric behavior of nitrocatecholglucuronides: A comparison of atmospheric pressure chemical ionization andelectrospray ionization

The mass spectrometric (MS) and tandem mass spectrometric (MS/MS) behavior of six nitrocatechol-type glucuronides using atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) was systematically stud ied, and the effect of operation parameters on the fragmentations are prese nted. The positive ion APCI- and ESI-MS spectra showed an intense protonate d molecule and the respective negative ion spectra a deprotonated molecule with minimal fragmentation. The main fragment ions in the MS/MS spectra of the protonated and deprotonated molecules were [M + H - Glu](+) and [M - H - Glu](-), respectively, formed by the loss of the glucuronide moiety. The measured limits of detection indicated that ESI is a significantly more eff icient ionization method than APCI in the negative and positive ion modes f or the compounds studied. MS/MS was found to be less sensitive, but more re liable and simple than MS due to the absence of chemical noise. (C) 1999 Am erican Society for Mass Spectrometry.