Assay of Oxytetracycline Residues in Salmon Muscle by Liquid Chromatography with Ultraviolet Detection

Abstract

Abstract A novel method for the assay of oxytetracycline residues in salmon muscle is described. Tissue is homogenized with 4 volumes of 1 % metaphosphoric acid in the presence of a small amount of dichloromethane (0.4 volume), shaken, and centrifuged. The residue is washed twice (4 and 2 volumes, respectively) with 1 % metaphosphoric acid, and the combined aqueous supernatants are concentrated to about 2 mL by flash evaporation and then diluted to 5 mL. Filtered aliquots of the extract are subjected to liquid chromatography using a C18 column with a mobile phase of acetonitrile-tetrahydrofuran- 0.025M aqueous oxalic acid (9 + 1 + 30) containing octanesulfonic acid at a final concentration of 10mM. Eluted peaks are monitored at 355 nm. Calibration and standard curves were linear from 0.01 to 0.5 μg on-column, with a limit of quantitation better than 0.05 μg/g. Recoveries from spiked blanks varied from 85.8 to 90.3% (relative standard deviation, 13.1-2.4%) in the 0.05-1.00 μg/g concentration range and were 21.1% at 0.02 μg/g.