Determination of four nitroimidazole residues in poultry meat by liquid chromatography–mass spectrometry

A multi-residue liquid chromatography–mass spectrometry (LC–MS) assay method is described for the determination of four nitroimidazoles in poultry muscle. The extraction procedure is based on liquid–liquid extraction with ethyl acetate followed by an evaporation step. A deuterated internal standard is used. The LC separation was made on a C18 bonded silica column with an aqueous formic acid (0.2%) solution–methanol–acetonitrile (81:13:6) mobile phase. Following electrospray ionization, the protonated molecular ion [M+H]+ is obtained for each compound. Monitoring several ions for each nitroimidazole provides the specificity required for confirmatory assay. Validation of the method was performed to estimate linearity, intra-day and inter-day repeatability, accuracy and detection limit. The present method is capable of identifying nitroimidazole residues in muscle at levels below 5 μg/kg.