Multiresidue method for the determination of nitroimidazoles and their hydroxy-metabolites in poultry muscle, plasma and egg by isotope dilution liquid chromatography–mass spectrometry

A multiresidue analytical procedure for the determination of four nitroimidazoles (metronidazole, dimetridazole, ronidazole, ipronidazole) and their hydroxy-metabolites in poultry muscle, plasma and egg is presented. The procedure is based on ion-exchange solid phase extraction with acetonitrile as an extractant followed by liquid chromatography–mass spectrometry. The separation of analytes was performed on a C18 column using a mobile phase of 0.1% formic acid in acetonitrile and 0.1% formic acid in water with gradient elution. The electrospray ionization was used to obtain the protonated molecules [M+H]+ and two product ions were monitored for each compound. For the quantification stable isotope-labelled analogues of the analytes were used as internal standards. The whole procedure was evaluated according to EU Commission Decision 2002/657/EC requirements. Specificity, decision limit (CCα), detection capacity (CCβ), recovery and precision were determined during validation process. The overall recoveries ranged between 93 and 103% with a good coefficient of variation, less than 14.0% under within-laboratory reproducibility conditions. CCα and CCβ were 0.05–0.44 and 0.08–0.90 μg kg−1 depending on analyte and matrix.