High-performance thin-layer chromatographic method for the fluorescence detection of three nitroimidazole residues in pork and poultry tissue

A high-performance thin-layer chromatographic method with fluorescence detection was developed for the qualitative determination of ronidazole, dimetridazole and their major metabolite, hydroxydimetridazole, in pork and poultry muscle. After extraction with dichloromethane and evaporation, the nitroimidazoles are redissolved in ammonium acetate buffer. The buffer phase is washed with hexane. The sample is cleaned-up by solid-phase extraction and the eluate evaporated. The final extract is resuspended in methanol and then spotted on an HPTLC plate. After multiple development with methanol and ethylacetate, the plate is dried, sprayed with pyridine and observed on an UV box (312 nm). The detection limits of this method are about 2 mu g/kg for ronidazole, 5 mu g/kg for dimetridazole and less than 5 mu g/kg for hydroxydimetridazole. Validation was performed to levels of 10 mu g/kg for dimetridazole, 5 mu g/kg for ronidazole and 5 mu g/kg for hydroxydimetridazole.