Determination of 5-nitroimidazoles and corresponding hydroxy metabolites in swine kidney by ultra-performance liquid chromatography coupled to electrospray tandem mass spectrometry

A rapid, sensitive and reliable multi-residue method for the simultaneous determination of four 5-nitroimidazoles (NIIMs) and their three corresponding metabolites in swine kidney was developed and validated. The compounds of interest were extracted from tissues with ethyl acetate. The crude extracts were subject to liquid–liquid partition with hexane followed by solid-phase extraction using mixed-mode strong cation-exchange column. Chromatographic separation was achieved on an AcQuity BEH C18 column and was completed within 4 min for each injection. Data acquisition under positive electrospray tandem mass spectrometry was performed by applying multiple reaction monitoring for both identification and quantification. Mean relative recoveries from fortified samples ranged from 83% to 111%, with coefficients of variation lower than 12%. The limits of detection and quantification for the NIIMs were in the range of 0.05–0.5 and 0.1–0.5 μg kg−1, respectively.