Simultaneous multiresidue determination of tetracyclines and fluoroquinolones in catfish muscle using high performance liquid chromatography with fluorescence detection.

Efficient methods are needed for analysis of veterinary drug residues in food. A number of methods are available for single analytes. Multiresidue methods are now increasingly available. It is still rare, however, to find methods not involving mass spectrometry which allow for analysis of more than one class of drug residue. An efficient multiresidue method for the simultaneous determination of fluoroquinolones (FQs) and tetracyclines (TCs) in catfish muscle has now been developed. This method involves an extraction of the analytes with a mixture of acetonitrile and citrate buffer containing magnesium chloride. After centrifugation and evaporation of the supernatants, the residues are determined using high performance liquid chromatography with fluorescence detection. With this method, five fluoroquinolones and three tetracyclines were determined in fortified catfish muscle at levels of 20, 50, and 100 ng g(-1). Average recoveries for ciprofloxacin (CIP), sarafloxacin (SAR), danofloxacin (DANO), enrofloxacin (ENRO), difloxacin (DIF), oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) were in the range of 60-92% with good relative standard deviations. The limits of quantitation ranged from 0.15 to 1.5 ng g(-1). Utilization of the method to successfully analyze catfish muscle samples incurred with enrofloxacin and with oxytetracycline is described.