The pretreatment methods for determination of dichlorvos and trichlorfor in pickled foods were developed using ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). MethodsSamples were ultrasonically extracted with acidified acetonitrile and cleaned up with dispersivesolid phase extraction (d-SPE) or gel-permeation chromatography (GPC) respectively. The extract components were separated and gradient eluted on a BEH C₁₈ column with acetonitrile-0.1% formic acid solutions, and external standard calibration was used for quantification. ResultsThe linearity was satisfying within certain range of concentration, and the coefficients of determination (r) were above 0.999 for dichlorvos and trichlorfor. The limits of detection (LODs) and the limits of quantitation (LOQs) were 1.0 and 2.0 μg/kg for d-SPE cleanup, 0.5 and 1.0 μg/kg for GPC cleanup, respectively. The recoveries of the spiked samples at the levels of 2,0, 20, and 40 μg/kg ranged from 81.7% to 104.2% for d-SPE cleanup, and from 72.4% to 89.8% for GPC cleanup, with the relative standard deviations (RSDs)less than 7.8%. There was no significant difference between the results obtained by the two kinds of cleanup.ConclusionThe proposed method is rapid, simple, sensitive and specific enough for the supervision of the illegal use of dichlorvos and trichlorfor in pickled foods. Dichlorvos was detected in 1 out of 8 pickled foods collected from local market.