High-performance liquid chromatographic determination of oxytetracycline in channel catfish (Ictalurus punctatus) muscle tissue

A high-performance liquid chromatographic method for the determination of oxytetracycline in channel catfish muscle tissue is presented. Oxytetracycline is extracted three times from muscle tissue with an ethylenediaminetetraacetic acid disodium salt–McIlvaine buffer (pH 4.0) by using an Ultra Turrax. Analysis is carried out by using high-performance liquid chromatography and an acetonitrile–oxalic acid (0.05 mol l–1, pH 2.2) mixture (14 + 86, v/v) is used as mobile phase. Oxytetracycline is separated on a Lichrosorb RP-8 125 × 4.0 mm i.d. column and ultraviolet detection at 355 nm is used. The limit of quantification is 10 ng g–1 and the linearity, tested in the spiking range 20–500 ng g–1, is 0.9997. Recovery from muscle spiked at 20, 50, 100, 200 and 500 ng g–1 levels is in the range 70–80%. Precision, expressed as percentage relative standard deviation, is below 7%. The method is applied to muscle tissue from channel catfish fed on a medicated diet