A SIFT study of the reactions of H3O+, NO+ and O2+ with hydrogen peroxide and peroxyacetic acid

We have carried out a selected ion flow tube, SIFT, study of the reactions of H3O+, NO+ and O-2(+) ions with hydrogen peroxide, H2O2, in the presence of excess water vapour and peroxyacetic acid, CH3C(O)OOH, in the presence of comparable concentrations of acetic acid, CH3COOH. This study was initiated to investigate if these peroxides could be analysed in humid air using selected ion flow tube mass spectrometry, SIFT-MS, using the above precursor ions. Rate coefficients and product ions have been determined for the NO+ and O-2(+) reactions with H2O2 molecules (H3O+ ions do not react at a measurable rate with H2O2 molecules) and for the rapid reactions of H3O+, NO+ and O-2(+) with CH3C(O)OOH molecules. It turns out that both H3O+ and O-2(+) ions are unsuitable for SIFT-MS analyses of these peroxides, either because of low reactivity and/or the production of common product ions for their reactions with H2O and CH3COOH molecules. However, the results of this study show that NO+ precursor ions can be useful for the SIFT-MS analysis of both these peroxides, NO+H2O2 being the monitor ion for hydrogen peroxide analysis in moist air, the production of this ion actually being catalysed by the presence of H2O molecules, and NO2+ ion being suitable monitor ions for peroxyacetic acid analysis in the presence of acetic acid. The kinetic data for these peroxide reactions are presented and the likely mechanisms of the reactions are alluded to. (C) 2003 Elsevier Science B.V. All rights reserved.