Abstract: An effective multi-residue method for the trace analysis of fipronil and four metabolites (fipronil-desulfinyl, fipronil-sulfide, fipronil-sulfone and fipronil-carboxamide) in tea was developed based on solid-phase microextraction coupled with gas chromatography (SPME-GC). The targets were extracted with a fused-silica fiber coated with 85 μm polyacrylate (PA). The extraction was performed in a pH 9 buffer (containing 0.1 mol/L boracic acid, 0.1 mol/L KCl and 0.1 mol/L NaOH) at 60 ℃ and under 2500 r/min for 30 min. With the concentration range of 2~10 μg/kg, the recoveries ranged from 71.2% to 109.3% and the relative standard deviations (RSDs) were lower than 10% (n=6). The limits of detection (LODs) and limits of quantitation (LOQs) of the studied compounds ranged from 0.3 μg/kg to 1.2 μg/kg and 1.0 μg/kg to 4.0 μg/kg, respectively, with the values well below the residue limits set by Japan, European Union and China. By the proposed method, 1 positive samples of 30 tea samples were found with fipronil and fipronil-sulfone. The identification of the method was done by gas chromatography-mass spectrometry (GC-MS). The method can be applied as a monitoring tool for tea, in the investigation of food to fipronil and its metabolites.

Key words: gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), metabolites, residue, tea, fipronil, solid-phase microextraction (SPME)