Liquid chromatographic analysis of incurred amoxicillin residues in catfish muscle following oral administration of the drug

Improper application of antibiotic chemicals to livestock and aquaculture s pecies may lead to the occurrence of residues in food supplies. An appropri ate depletion period is needed after the administration of drugs to animals for ensuring that residues in edible tissues are below established toleran ce levels. This study was conducted to determine incurred amoxicillin resid ues in catfish muscle following oral administration. Dosed fish were harves ted after four depletion periods, and muscle fillets were analyzed for amox icillin residues using an HPLC method with precolumn derivatization and flu orescence detection. The residue levels in fish after a 6-h depletion range d from 40 to 64 ng/g with one exception at 297 ng/g. Average residue levels decreased to 5.4 and 2.8 ng/g after 24- and 48-h depletions, respectively. Residue levels after a 72-h depletion decreased to below the method's limi t of quantitation (1.2 ng/g). An LC-MS/MS confirmatory method was developed . Confirmation of the presence of amoxicillin was demonstrated in incurred fish samples containing residues at -50-300 ng/g.