Abstract:

AA pretreatment method was developed based on solid phase extraction(SPE) and applied to determine the residual pyrimethanil and fluazifop-butyl in green onion, scallion and onion by gas chromatographymass spectrometry(GC-MS). The samples were extracted from homogenized tissue with acetonitrile， separated with liquidliquid partition. The supernatants were purified by SPE(Envi-18 and Florisil columns) prior to the GC-MS analysis. Determination was performed in a selected ion monitoring(SIM) mode and external standard method was used in the quantification. The method was convenient and rapid after investigating the conditions of pretreatment and determination. Under the optimal conditions， the detection limits of pesticides by the method(S/N=10) were under 0.01 mg/kg. Tests for recovery were carried out by addition of standard at a concentration of 0.01~0.2 mg/kg, the recoveries of pyrimethanil and fluazifopbutyl were 81.4％～94.6％ and 107％～129％ with relative standard deviations of 3.3％～11％ and 4.0％～9.7％, respectively.

Key words: solid phase extraction(SPE), gas chromatography-mass spectrometry(GC-MS), sample pretreatment, pyrimethanil, fluazifop-butyl, onion