Abstract: A high-performance liquid chromatography (HPLC) method was developed for the simultaneous analysis of 5 nitroimidazole multi-residues (metronidazole, dimetridazole, ornidazole, tinidazole and ronidazole) in tilapia muscle tissues. Samples were homogenized and extracted by added sodium chloride, monopotassium phosphate and ethyl acetate. Afterwards, the organic phase was recovered and condensed. Finally, the residue was dissolved in hydrochloric acid/ethyl acetate, defatted by liquid-liquid extraction with added n-hexane, cleaned up on an MCX column by elution with 2% ammonia/methanol, separated chromatographically using acetate buffer solution/acetonitrile (86:14, V/V) as the mobile phase and detected at 320 nm. The results revealed that the limits of detection for 5 nitroimidazoles were all 1.0 μg/kg. The average recoveries for metronidazole, dimetridazole, ornidazole, tinidazole and ronidazole at the spike level of 2.0 μg/kg were 73.3%%, 74.7%, 62.9%, 74.4% and 80.1%, respectively with a RSD of less than 10% (n = 3). This method is simple, sensitive, accurate, precise, and in line with the requirements the Ministry of Agriculture for veterinary drug residue analysis.

Key words: solid phase extraction, high performance liquid chromatography (HPLC), tilapia, nitroimidazoles