Determination of 23 Residual Pesticides in Vegetables by Gel Permeation Chromatographic Purification and Capillary Gas Chromatography

Residual pesticides in vegetables were extracted with ethyl acetate and purified by passing the extract through a gel permeation chromatographic column.Elute the column with cyclohexane-ethyl acetate (1∶1,V/V) at a flow rate of 5 mL·min-1 and collect the fractions between 85-175 mL.Concentrate the collected eluate to dryness and dissolve it with 1 mL of cyclohexane-ethyl acetate.The residual pesticides were detected with a capillary gas chromatograph equipped with nitrogen-phosphorus detector.Using the established three steps-heating program,23 peaks of pesticides were resolved.Detection limits of the proposed method were in the range of 0.002-0.005 mg·kg-1,and linearity relationship between 0.5-5.0 mg·L-1 was obtained.Recovery was ranged in 75.6%-110.7% and RSDs of determination were ranged in 0.56%-8.26%.The method has been applied to the analysis of the residual pesticides in vegetables and fruits.