Abstract: [Objective] To develop a liquid chromatography-tandem mass spectrometry （LC-MS/MS） method for simultaneous detection of colistin A and colistin B in mutton. [Method] The samples were extracted with 10% trichloroacetic acid aqueous solution-acetonitrile solution, and then the targets were purified and enriched with WCX solid phase extraction column. The targets were gradiently eluted using 0.1% formic acid aqueous solution as mobile phase with a flow rate of 0.3 mL/min. After screening by multiple reaction monitoring （MRM） under positive ion mode, the targets were detected by LC-MS/MS and were quantitatively determined by external standard method with addition of standard solution in matrix. [Result] Colistin A and colistin B had a good linear relationship in the range of 5.0-110.0 μg/L, and the linear correlation coefficients were above 0.996. The limit of quantitation of the developed LC-MS/MS method was 0.50 μg/kg. At three adding levels, the average recoveries ranged from 73.2% to 115.6% with relative standard deviations （RSD） ≤10.0%. [Conclusion] The developed LC-MS/MS method is highly efficient and accurate, and is applicable for quantitative and confirmatory determination of colistin A and colistin B in mutton samples.

Key words: colistin, liquid chromatography-tandem mass spectrometry, detection method, mutton