across-sectional study on oxytetracycline and tetracycline residues in pasteurized milk supplied in tehran by an hplc method

tetracyclines (tcs) are broad-spectrum antibiotics that are used widely in veterinary medicine. the present study was carried out to trace the residues of oxytetracycline (otc) and tetracycline (tc) in pasteurized milk that is marketed in tehran with the use of a high performance liquid chromatography (hplc). ninety milk samples were collected during five sequential days from the products of six major dairy companies. otc and tc residues were extracted and quantified by an hplc method with an ultraviolet radiation detector. tc residues were found in seven (7.8%) milk samples. the otc and tc in almost all samples were lower than 100 ppb (parts per billion), which is the maximum residue level advised. however, the total residue of otc and tc in one milk sample was 138.8 ppb. in conclusion, due to the presence of a significant amount of tc residues in a number of milk samples, more studies and further supervision of the quality of milk products are required.