Studies on Residual Antibacterials in Foods (I) Determination of Tetracyclines by High-Performance Liquid Chromatography

A simple and reproducible method for the determination of residual tetracyclines (TCs) in livestock products by high-performance liquid chromatography was established. Tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) in a sample were extracted with 5% aquous perchloric acid. The extract was passed through SEP-PAK C18 cartridge. After washing the cartridge with water, TCs was eluted with a mixture of N, N-dimethylformamide (DMF)-water (4 : 6) containing 0.02 M phosphoric acid. The eluate was injected on a Li Chrosorb RP-8 column by using a mixture of DMF-water (1 : 4) containing 0.02M phosphoric acid as a mobile phase. The effluent was monitored with a UV detector at a wavelength of 340 nm. The recoveries of TCs from cattle muscle, liver, kidney and milk fortified with 1μg/g of TC and OTC and 2μg/g of CTC were 34.7-52.9% for muscle, 37.7-51.6% for liver, 53.1-68.3% for kidney and 74.8-88.7% for milk, respectively. The quantitative analysis was carried out by the method of standard addition and the minimum detectable amount of TC and OTC was 0.1 ppm and CTC was 0.2 ppm.