Abstract: A method was developed for the determination of fipronil and its three metabolites including fluorocarbonitrile, fipronil sulfone and fipronil sulfide in vegetables by gas chromatography-negative ion chemical ionization-mass spectrometry (GC-NCI/MS). The target compounds were extracted from samples with acetonitrile, and then purified by the QuEChERS method before analysis. Quantification was performed using a matrix-matched calibration curve with external standards. The results indicated that the linearity of the method was good in the concentration range between 0.2 and 10.0 μg/L, and the average recoveries were 88.9%–105.8% with relative standard deviations (RSDs) of 2.2%–7.6% at three spiked levels (1.0, 5.0 and 10.0 μg/kg). The limits of detection (LODs) were 0.2–0.3 μg/kg，and the limit of quantification (LOQ) was 1.0 μg/kg. The developed method was simple, sensitive and accurate, and could be used for the routine analysis of the residues of fipronil and its three metabolites in vegetables.

Key words: gas chromatography-negative ion chemical ionization-mass spectrometry; quick, easy, cheap, effective, rugged and safe extraction; vegetables; fipronil and its metabolites