By packing N-propylethylenediamine (PSA) and multi-walled carbon nanotubes (MWNTs) separately, a homemade double solid phase extraction purification column was made. A gas chromatographic method was developed for the simultaneous determination of 11 kinds of organophosphorus pesticides, including dichlorovos, methamidophos, acephate, phorate, omethoate, dimethoate, chlorpyrifos, malathion, parathion-ethyl, quinalphos and ethion in Xinhui dried orange peel and its products. The samples were centrifuged after extracted by ethyl acetate, and then cleaned up with a homemade double PSA/MWNTs solid phase extraction column. The separation of target compounds was performed on an Agilent RTS-1701 capillary column with temperature programmed within 25 min, then determined by a flame photometric detector and quantified by using external standard method. The factors affecting the determination, such as packing type, amount of packing, elution mode, extraction solution and ultrasonic time, were investigated. Under the optimized experimental conditions, the novel method showed a good linearity in the range of 0.020-1.0 mg/L with correlation coefficients of 0.9990-0.9998, the limits of detection were 3.5-9.6 μ g/kg for the pesticides. The new method was successfully applied to the analyses of organophosphorus pesticides in Xinhui dried orange peel and its products. The recoveries spiked with organophosphorus pesticides standards at three concentration levels of 10, 25 and 100 μ g/kg in samples were 50.8%-109% with relative standard deviations of 2.7%-8.5%. The established method is accurate, sensitive, simple and fast. The detection limits of the method meet the limited requirements of organophosphorus pesticide residues. The homemade column is cost saving and worthy of popularization and application. The study provides a useful method for the analysis of trace substance.
