Occurrence of tetracycline, chlortetracycline, and oxytetracycline residues in raw cow's milk

Abstract

The objective of this study was the detection of tetracycline, chlortetracycline and oxytetracycline residues in raw cow’s milk. When analysing bulk milk (<i>n</i> = 57) and tanker trailer’a (<i>n</i> = 113) samples, two methods were used simultaneously: a specific rapid test Milk Tetrasensor Kit and high performance liquid chromatography (HPLC) with ultraviolet detection and isocratic elution. For HPLC analysis, Breeze (Waters, USA), a liquid chromatographic system, was used. The samples underwent solid phase extraction before the HPLC analysis. The Nova Pack C8 column (3.9 × 150 mm, 4 μm, Waters) and mobile phase (0.8 ml/min) consisting of acetonitrile, methanol, and 0.05 mol/l of oxalic acid in a 13:13:74 ratio were used. None of the samples analysed with the use of the specific rapid test displayed the presence of tetracycline antibiotics. In all of the samples analysed by means of HPLC, low concentrations of tetracycline antibiotics residues were detected. None of the samples displayed the presence of chlortetracycline. All of the analysed samples displayed residues of tetracycline. Oxytetracycline residues were detected only in 50.6% of analysed samples.