Determination of antibiotics and their metabolites in milk by liquid chromatography-tandem mass spectrometry method

The aim of this study was to investigate the presence of antibiotic residues and metabolites in the samples of colostrum, raw cow milk, raw goat milk, and ultra-high temperature treated milk by liquid chromatographytandem mass spectrometry. The calibration curves for all the studied compounds showed good linear correlation coefficients (r2 >= 0.999). The recovery rates were 73.33-87.78%, also the limit of detection and limit of quantification values were 0.68-3.16 mu g/kg and 2.24-10.43 mu g/kg, respectively. Antibiotic residues including tetracycline, 4-epitetracycline, 4-epioxytetracycline, 4-epichlorotetracycline, and ciprofloxacin were detected in 72 (55.38%) out of 130 milk samples. However, 6 (28.57%) of 21 raw goat milk and 6 (8.82%) of 68 raw cow milk samples were found to be above maximum residue limits for the sum of tetracycline and its 4-epimer. Since residues of antibiotics were detected, the results suggest that good veterinary practices are not followed by all milk producers.