Abstract: To establish a reliable pretreatment method for cyadox in milk with UPLC-MS/MS. The sample was extracted by ethyl acetate, then the results was analysed after PEP cartridge purification. The objective compounds were separated using Inertsil ODS-3column（3 μm,2.1 mm×100 mm）with acetonitrile/ methanol（3∶11） -water （0.1% formate） as mobile phase and analyzed by mass spectrometry in the positive electrospray ionization under multiple reaction monitoring mode（MRM）. The results showed that PEP cartridge had good recovery rate. The detection limit of cyadox was 0.01 μg/g, limit of quantitation was 0.04 μg/g, the average recoveries for spiked levels of 0.384, 0.960,1.920 μg were 136.0%, 116.0%, 62.6%. The method is suitable for the detection of cyadox residual in milk.

Key words: cyadox, solid phase extraction colum, UPLC-MS/MS