A selected ion flow tube, SIFT, study of the reactions of H3O+, NO+ and O2+ ions with several N- and O-containing heterocyclic compounds in support of SIFT-MS

We present the results of a selected ion flow tube (SIFT) study of the reactions of H3O+, NO+ and O2+ ions with 11 N-containing heterocyclic compounds and seven O-containing heterocyclic compounds, M. Most of these compounds have more than one functional group and some of them are known to occur in biological fluids and other media. The major objective is to provide the required kinetic data (rate coefficients and product ions) to extend the library for selected ion flow tube mass spectrometry, SIFT-MS, to allow these compounds to be detected and quantified in humid air samples. The results show that the H3O+ reactions are very simple, leading only to a stable protonated molecule, MH+, which facilitates SIFT-MS analyses. The NO+ reactions are also relatively simple, again mostly producing a single product ion species, which is variously M+, (M-H)+ and NO+M, so NO+ is a suitable precursor ion species for the analysis of these compounds. Generally speaking, the O2+ reactions result in more than one product ion following dissociative charge transfer and so O2+ precursor ions are less suitable for SIFT-MS analyses of these heterocyclics. Some attention is given to the formation of the hydrates of the MH+ product ions via three-body association and/or switching reactions (in most cases only the monohydrate is produced), since these hydrates must be included in the SIFT-MS analyses of these heterocyclic compounds.