Survey of 11 nitroimidazole residues in hen and duck eggs from the Irish market

A liquid chromatography-tandem mass spectrometry method, recently developed, validated and accredited, was used to screen for metronidazole, ronidazole dimetridazole ipronidazole, ternidazole, tinidazole, ornidazole carnidazole and three hydroxy metabolites (hydroxy-metronidazole, HMMNI and hydroxy-ipronidazole) in Irish retail egg samples. The method used had decision limits (CCα) in the range 0.33-1.26 μgkg^-1 and detection capabilities (CCβ) ranging 0.56-2.15 μgkg^-1 for all analytes. Internal standard-corrected recovery, calculated for the various analytes, ranged 87.2-106.2%, while the coefficient of variance, expressed as % CV, ranged 3.7-11.3%. The method was applied to 160 samples of caged, free range and organic hen and duck eggs available on the Irish retail market as well as two incurred proficiency test egg samples. No nitroimidazole residues were detected in the survey samples above the CCα and the results achieved for the two proficiency test samples were acceptable when compared with the assigned values.