Monitoring of oxytetracycline in ovine milk by HPLC

A method for ‘in vivo’ determination of the oxytetracyclin residues in ovine milk at low levels is described. Two
groups of Sardinian breed sheep were treated with a dose of oxytetracycline by intramammary infusion and
intramuscular administration, respectively. Oxytetracycline residues in extracts obtained from a preliminary cleanup
procedure, were detected by an isocratic high-performance liquid chromatography (HPLC) method. Linear calibration
plots were obtained over a large concentration range of 1 mg ml1–10 ng ml1, with correlation coefficients
higher than 0.996. Recoveries between 85.8 and 98.9% were obtained. Limit of detection (LOD) and limit of
determination (LOQ) were 5.2 and 17.5 ng ml1, respectively. This method would be useful for routine monitoring
of oxytetracycline residues in ovine dairy milk.