GC Determination of Residual Amounts of Organophosphorus and Pyrethroid Pesticides in Vegetables with QuEChERS

Gas chromatography was applied to the determination of residual amounts of 30 organophosphorus pesticides and 7 pyrethroid pesticides in vegetables with sample pre-treatment by QuEChERS method. The pesticides were separated from vegetable samples by extraction with acetonitrile and the extract was purified by dispersive-SPE. After centrifugation, 2 aliquots (2 mL each) of the supernatant were taken and evaporated to dryness by N2-blowing, and the residues were taken up with 0.5 mL of dichloromethane and n-hexane separately, which were used for separation on HP-5MS chromatographic column. Flame photometric detector was used in the determination for organophosphorus pesticides and electron capture detector was used in the determination for pyrethroid pesticides. Linearity ranges for the 30 organophosphorus pesticides were found same between 0.05-1.0 mg·L-1 with detection limits (3S/N) in the range of 0.003 7-0.015 7 mg·kg-1; linearity ranges for the pyrethroid pesticides were same between 0.02-0.5 mg·L-1 with detection limits (3S/N) in the range of 0.000 3-0.001 7 mg·kg-1. Recovery was tested at 2 different concentration levels and values of recovery found were ranged from 81.2% to 104.7% with RSD′s (n=6) in the range from 3.0% to 11.4%.