Determination of oxytetracycline in meat and fish using metal chelate resin for clean-up

Abstract

A rapid and reliable quantitative screening procedure was developed for analysis of oxytetracycline (OTC) in animal-derived foods. The procedure involves clean-up using metal chelate (MC) resin and on-line confirmation. Samples were homogenized in 0.25% metaphosphoric acid-methanol-acetonitrile (6:2:2). OTC was selectively extracted onto MC resin preloaded with Cu2+ and determined by HPLC with fluorescence detection using a Mg2+-containing mobile phase. Recoveries at levels of 0.1 and 1μg/g were 80.8 ∼ 86.6% (average: 83.8%) with the coefficient of variation of 0.7 ∼ 6.0%. The limit of quantitation was set at 0.02μg/g. Forty samples of meal and fish were analyzed and OTC was found in unagi kabayaki (0.04/μg/g) and in shrimp (0.39 μg/g). The presence of OTC in the samples was confirmed by the on-line confirmatory technique, that gives visual evidence of whether the equivalent peak is OTC or not, based on its disappearance on the chromatogram when a Mg2+-free mobile phase is used.