Improved screening method for the detection of a range of nitroimidazoles in various matrices by optical biosensor

An immunobiosensor assay was developed for the multi-residue screening of a range of nitroimidazole compounds in various species and sample types including porcine, bovine and ovine kidney, avian liver, serum and eggs and bovine milk. A polyclonal antibody which binds at least seven of the major nitroimidazoles and their metabolites was raised in a sheep after inoculation with a metronidazole protein conjugate. Sample homogenates were extracted into acetonitrile and subjected to micro-centrifugation prior to biosensor analysis. Validation data obtained from the analysis of 20 fortified samples has shown that the method has a detection capability (CCβ) of less than 1 μg kg−1 (or μg L−1) for dimetridazole (DMZ) in all species and matrices investigated. In addition, cross-reactivity data and the analysis of a small number of fortified samples have shown that the method will also detect a range of other major parent nitroimidazoles and their metabolites including ronidazole (RNZ), ipronidazole (IPZ), metronidazole (MNZ), hydroxymetronidazole (MNZOH), hydroxydimetridazole (DMZOH) and hydroxyipronidazole (IPZOH). The cross-reactivity profile and validation data for the detection of these nitroimidazoles are presented together with the results obtained following the analysis of a small number of incurred samples using the developed method.