Fipronil belongs to a new class of insecticides known as phenylpyrazole, and is highly specific to the invertebrate ?-aminobutyric acid (GABA)-receptor. Research has shown that fipronil and its three metabolites (fipronil-thioether, fipronil sulfone and fipronil-desulfinyl) display high toxicity to bees and aquatic organisms, so it is only allowed to be used as a soil or seed treatment agent in some countries. Fipronil can be effectively used in peanut fields against soil insects, but the scientific literature is lacking about residue analysis methods and residue depletion studies of fipronil and its metabolites in peanuts under field conditions. In this study, a modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method was established for extraction and clean up of fipronil and the three metabolites in peanut matrices and soil, and HPLC-MS/MS was used for detection. Then their dissipation trend and final residue levels in peanut plant and soil under field conditions were investigated. The average recoveries of the four substances in peanut, peanut shell, peanut plant and soil were 74%-116% with the RSD<17%, and the method was simple and sensitive with LOQ of 0.0002 mg/kg in all matrices. The results of dissipation experiments demonstrated that fipronil is the main residue compound in peanut plant and soil after treatment and the half-lives were 5-16 days in peanut plants, and 17-43 days in soil, respectively. The photodegradation metabolite, fipronil-desulfinyl, and the oxidative product, fipronil sulfone, were the highest residue metabolites in peanut plant and soil samples, respectively. The final residues at harvest in peanut grains were all below 0.02 mg/kg, while in peanut shells the total residues were still high (0.09-0.98 mg/kg), and in soil were 0.003-0.16 mg/kg. Fipronil was the main residue compound and the oxidative metabolite fipronil sulfone was the highest metabolite in all terminal residue samples.

Residue study of fipronil and its metabolites in peanut field conditions

248th National Meeting (2014)

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