Determination of 6 Kinds of Veterinary Drug Residues in Milk by Ultra Performance Liquid Chromatography-tandem Mass Spectrometry

Objective: To establish a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the determination of six veterinary drug residues in milk samples. Methods: The sample was extracted with acetonitrile solution, purified with MAX solid phase extraction column, and separated by Waters X Bridge BEH-C₁₈ chromatographic column. The mobile phase was eluted with a gradient of acetonitrile and 0.1% formic acid aqueous solution, and electrospray ion source was used, positive and negative ion switching scanning mode for detection, external standard method for quantification. Results: The 6 veterinary drugs showed a good linear relationship in the range of 0~10 ng/mL, and the coefficient of determination (R²) was greater than 0.995. The detection limit of the 6 veterinary drugs was 0.06~0.18 μg/kg. The limit of quantification of the method was 0.5~2.0 μg/kg. With the addition of 0.5~8.0 μg/kg in the standard recovery experiment, the recovery rates of the 6 veterinary drugs were 67.1%~105.5%, and the relative standard deviations were all less than 10%. Conclusion: This method is easy to operate, fast in analysis, and high in sensitivity. It can be used for the determination of veterinary drug residues in milk samples.