Psutka, JarrodDion-Fortier, AnnickDieckmann, ThorstenCampbell, J. LarrySegura, PedroHopkins, W. Scott2021-10-202021-10-202018-04-17https://doi.org/10.1021/acs.analchem.8b00484http://hdl.handle.net/10012/17659This document is the Accepted Manuscript version of a Published Work that appeared in final form in, copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.analchem.8b00484.A transformation product of trimethoprim, a contaminant of emerging concern in the environment, is generated using an electro-assisted Fenton reaction and analyzed using differential mobility spectrometry (DMS) in combination with MS/MS techniques and computational calculations to develop a rapid method for identification. DMS is used as a pre-filter to separate positional isomers prior to subsequent identification by mass spectrometric analyses. Collision induced dissociation of each DMS separated species is used to reveal fragmentation patterns that can be correlated to specific isomer structures. Analysis of the experimental data and supporting quantum chemical calculations show that methylene-hydroxylated and methoxy-containing phenyl ring hydroxylated transformation products are observed. The proposed methodology outlines a high-throughput technique to determine transformation products of small molecules accurately, in a short time and requiring minimal sample concentrations (<100 ng/mL).enmass spectrometrydifferential mobilityenvironmentcontaminantArticle