[Determination of organophosphorus pesticide residues in milk of cows and sheep by ultra-high-performance liquid chromatography- tandem mass spectrometry combined with passing type purification method].

OBJECTIVE:A method for the rapid determination of dichlorvos, trichlorfon, fenthion, fenthion-sulfone, fenthion-sulfoxide, fenthion-oxon, fenthion-oxon-sulfone, fenthion-oxon-sulfoxide, phoxim, propetamphos, malathion, diazinon and coumaphos 13 common organophosphorus pesticides and their metabolites poison residues in milk of cows and sheep by ultra-high-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) with passing type solid phase extraction(SPE) purification was developed. METHODS:After centrifugation at 4 ℃, the milk was purified by passing type SPE with acetonitrile precipitating protein and determined by UPLC-MS/MS in electrospray positive ion mode(ESI+) and multi-reaction monitoring scanning(MRM), external standard method for quantitative analysis with matrix matching standard curve. RESULTS:The recoveries of 13 target compounds were between 81.5% and 107.5% and relative standard deviation was between 1.24% and 6.23% at three spiked levels of 5, 10, 20 μg/L. The detection limits of 13 target compounds were between 0.015 and 0.15 μg/L, and the quantitative limits were between 0.05 and 0.50 μg/L. No organophosphorus pesticide residues were detected in 20 samples of cows and sheep milk. CONCLUSION:The method has the advantages of good linear independence, low detection limit, high precision and accuracy, and can be used for daily monitoring of milk and related products.