Abstract: The back-flush technique was used in the determination of organophosphorus pesticide residues in vegetables by gas chromatography. The pesticide residues were extracted with acetonitrile and sodium chloride under mechanical shaking, and separated by centrifuging and partitioning. The extract was analyzed by gas chromatograph equipped with a flame photometric detector and a micro fluidic device with back-flush function. The results showed that the 16 organophosphorus pesticides have good linearity within the concentration range of 0.040~3.20 mg/L. The recoveries varied from 75.2% to 111.5%, with the relative standard deviations (RSDs) in the range of 2.8%~10.4%. The detection limits of these target compounds were from 0.003 to 0.01 mg/kg. The application of back-flush technique in this method significantly reduced the cycle time and matrix effect and improved the analysis efficiency.

Key words: back-flush, matrix effect, pesticide residues , gas chromatography (GC)