Abstract: A novel method for rapid determination of eight lipophilic pesticides in vegetables was developed using dispersive liquid-liquid micro-extraction (DLLME) coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS). The analyte in the vegetable was extracted with water-acetone (5:1, v/v) solution. Then, the extract was transferred into a centrifugal tube with 25 mg primary secondary amine (PSA), 50 mg C18 and 25 mg graphitized carbon black powder. The important parameters that affected the extraction efficiency were studied, such as the extraction and dispersed solvents, and the extraction time. The results showed that a good extraction efficiency was obtained, with acetone used as the dispersed solvent and 50.0 μL chlorobenzene used as the extraction solvent. Under the optimum conditions, the enrichment factors ranged from 526 to 878. The linearity ranges of the eight targeted compounds were 0.005~10 mg/kg, and the limits of detection (signal/noise=3) were 0.001~0.02 mg/kg, with the correlation coefficients varying from 0.9921 to 0.9989. The recoveries of the pesticides ranged from 60.1% to 82.5% with the relative standard deviations between 1.2% and 9.6%. The method has been used to analyze the eight lipophilic pesticide residues in vegetable samples with satisfactory results.

Key words: dispersive liquid-liquid microextraction, lipophilic pesticide residues, vegetables, gas chromatography-tandem mass spectrometry (GC-MS/MS)