Determination of oxytetracycline in fish tissues by high performance liquid chromatography.

A method for determination of oxytetracycline (OTC) in fish tissues was developed using a high performance liquid chromatograph (HPLC).OTC was extracted from fish tissues with 5% trichloroacetic acid containing 0.5% disodium ethylenediaminetetraacetate (EDTA). The extract was centrifuged and concentrated. The concentrated solution was washed with n-hexane and passed through a Sep-pak C18 cartridge. The cartridge was pre-wetted with 5% EDTA before use. After washing the eluate was evaporated to dryness. The residue was dissolved in acetonitrile-water (3:7). The solution obtained was analysed by HPLC using M & S Pack C18 as an analytical column and methanol-acetonitrile-0.2 M oxalic acid (1:1:3:5), pH 2.0 as a mobile phase. OTC was detected at 360 nm.The average recoveries of OTC from muscle, serum, liver, kidney, bone, and skin of rainbow trout were 74, 82, 75, 72, 73, and 65%, respectively. Their coefficients of variation were 4.3-7.3%. The detection limits for muscle and serum were 0.05 ppm, and those for liver, kidney, bone, and skin were 0.1 ppm.