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

A multi-residue liquid chromatography-mass spectrometry (LC-MS) assay metho d is described for the determination of four nitroimidazoles in poultry mus cle. The extraction procedure is based on liquid-liquid extraction with eth yl acetate followed by an evaporation step. A deuterated internal standard is used. The LC separation was made on a C-18 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 [MCH ](+) is obtained for each compound. Monitoring several ions for each nitroi midazole provides the specificity required for confirmatory assay. Validati on of the method was performed to estimate linearity, intra-day and inter-d ay repeatability, accuracy and detection limit. The present method is capab le of identifying nitroimidazole residues in muscle at levels below 5 mu g/ kg. (C) 2000 Elsevier Science B.V. All rights reserved.