A trace analysis of oxytetracycline and tetracycline residues in pasteurized milk supplied in Tehran: a one-year study (April 2011-March 2012)

Abstract

BACKGROUND: Tetracyclines (TCs) are broad-spectrum<br />antibiotics that are widely used in veterinary medicine. The<br />presence of TCs residues in milk is a public health concern all<br />over the world. OBJECTIVES:This study aimed to determine TCs<br />residuals in pasteurized milk marketed by some dairy companies<br />in Tehran from April 2011 to March 2012. METHODS: 432<br />pasteurized milk samples were purchased from supermarkets<br />supplying the milk products of 12 major dairy companies in<br />Tehran (3 samples from each company every month), and they<br />were stored at -20 0C until analysis. Oxytetracycline (OTC) and<br />Tetracycline (TC) residues in each sample were extracted by a<br />liquid - liquid phase procedure and quantitated using a high<br />performance liquid chromatographic (HPLC) method. Chromatographic<br />conditions included a mobile phase as oxalic acid<br />buffer- acetonitril (80: 20) with a flow rate of 1mL/min and UVdetection<br />at 355 nm. RESULTS: TCs residuals in most milk<br />samples were lower than 100 ppb, maximum residue level<br />(MRL); however, in seven samples (1.62%) the total residues of<br />OTC and TC were more than MRL. In the latter milk samples, the<br />median total TCs residue was 625 ppb, ranging between 274 and<br />1270 ppb. CONCLUSIONS: Because of the presence of TC<br />residues above the MRL level in a limited number of milk<br />samples, it is concluded that more studies and supervision of<br />health authorities are needed in this field.