Abstract:

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established for the simultaneous determination of 35 antibiotic residues of tetracyclines, sulfonamides, penicillins, macrolides and amphenicols in milk. The samples were extracted with alkaline acetonitrile and Mcllvaine buffer solution under ultrasonication. The separation of target compounds was performed on an Eclipse XDB-C₈ column (150 mm×2.1 mm, 3.5 μm) with gradient elution at a flow rate of 0.25 mL/min, and with an injection volume of 10 μL. The identification and quantification of the compounds were completed by liquid chromatography-tandem mass spectrometry in multiple reaction monitoring (MRM) mode. The limits of detection were all below 10.0 μg/kg. The average spiked recoveries of the method ranged from 70.1% to 109.9% with relative standard deviations (RSDs) of 2.89%-9.99%. After validation, the method was applied to the analysis of antibiotic residues in milk products in China. Fifty samples were screened under the well defined methodology, and the results showed that chloramphenicol, only in one sample, was monitored with the content of 0.48 μg/kg. A risk of contamination of milk with chloramphenicol has been determined to exist. Therefore this method is convenient, rapid, sensitive and reliable, and can be successfully applied to the simultaneous detection of the 35 antibiotic residues of tetracyclines, sulfonamides, penicillins, macrolides and amphenicols in milk.

Key words: antibiotics, liquid chromatography-tandem mass spectrometry (LC-MS/MS), milk