Validation of a method for the detection and confirmation of nitroimidazoles and corresponding hydroxy metabolites in turkey and swine muscle by means of gas chromatography–negative ion chemical ionization mass spectrometry

The results of a validation study of a GC–NCI–MS method for the quantitative determination of 5-nitroimidazoles {1,2-Dimethyl-5-nitroimidazole (dimetridazole, DMZ), 1-methyl-2-[(carbamoyloxy)methyl]-5-nitroimidazole (ronidazole, RNZ), 1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole (metronidazole, MNZ) and 2-isopropyl-1-methyl-5-nitroimidazole (ipronidazole, IPZ)} including the hydroxy metabolites of these agents {2-hydroxymethyl-1-methyl-5-nitroimidazole (HMMNI), 1-(2-hydroxyethyl)-2-hydroxymethyl-5-nitroimidazole (MNZOH), and 1-methyl-2-(2′-hydroxyisopropyl)-5-nitroimidazole (IPZOH)} in turkey and swine muscle are presented. The validation was carried out according to the requirements of the draft for the revision of Commission Decision 93/256/EC, which is expected to be adopted by the European Commission in due course. The determination of the method’s performance parameters revealed decision limits (CCα) between 0.65 and 2.8 μg/kg for DMZ, RNZ/HMMNI, MNZ and MNZOH. Confirmatory analyses according to the requirements of the forthcoming EC decision are possible for all analytes except for IPZ and IPZOH where already the decision limits (CCα) were higher (5.2 μg/kg) than for the above-mentioned nitroimidazoles. The within-laboratory reproducibility and the mean recovery were in an acceptable range for all analytes.