Determination of nitroimidazole residues in aquaculture tissue using ultra high performance liquid chromatography coupled to tandem mass spectrometry.

An UHPLC-MS/MS method was developed for the quantitative confirmatory analysis of residues of nitroimidazole drugs (dimetridazole, ipronidazole, metronidazole, ornidazole and ronidazole) and their corresponding hydroxy metabolites (HMMNI, ipronidazile-OH and metronidazole-OH) in aquaculture tissue. Samples were extracted by shaking in acetonitrile, water, MgSO4 and NaCl before being defatted with n-hexane pre-saturated with acetonitrile and concentrated under nitrogen. Nitroimidazole residues were determined by UHPLC-MS/MS operating in positive electrospray ionisation mode using a reversed phase BEH C18 column.