Abstract: An analytical method was established for the determination of three pyrethroids (bifenthrin, fenpropathrin and flucythrinate) in tomatoes using the quick, easy, cheap, effective, rugged and safe (QuEChERS) cleanup and gas chromatography. The tomato samples were extracted with acetonitrile, cleaned-up by dispersive solid-phase extraction using primary secondary amine as sorbents, concentrated by dispersive liquid-liquid microextraction (DLLME), and analyzed by gas chromatography. Factors affecting the extraction efficiency such as the type and volume of extraction solvent and the volume of dispersive and extraction time were investigated in detail. In the DLLME procedure, 40 μL chloroform was used as the extraction solvent and 1000 μL acetonitrile was used as the dispersive solvent and the extraction time was 60 s. Under the optimized conditions, the limits of detection for bifenthrin, fenpropathrin and flucythrinate were 0.5, 0.5 and 0.3 μg/kg, and the average recoveries in tomato samples at the spiked levels of 1, 10 and 50 μg/kg were 89%~109%, 92.5%~105% and 90%~108% with the relative standard deviations of 2.5%~7.6%, 2.8%~5.7% and 3.8%~9.1%, respectively. The proposed method is simple, quick, safe, reliable and applicable to analyze pyrethroid residues in tomato samples.

Key words: gas chromatography (GC), pyrethroid pesticides, QuEChERS, tomatoes, dispersive liquid-liquid microextraction