Determination of Oxytetracycline in Raw and Cooked Channel Catfish by Capillary Electrophoresis

Oxytetracycline (OTC) residues exceeding 0.1 ppm tolerance level were detected by capillary electrophoresis (CE) in catfish fillets 18 h after oral feeding with 37.5, 75.0, and 150.0 mg OTC/kg in medicated feed for 10 days. The CE migration time of OTC was 10.9 min using a 24 cm × 25 μm capillary under 8 kV constant voltage. The mean OTC recovery rates in spiked catfish were 92.9% over the concentrations of 0.1−25 ppm. Cooking procedures (frying, baking, and smoking at 190 °C) could only reduce but not completely eliminate OTC residues in catfish fillets.