Desulfinyl-fipronil

The Ottawa sand (20-30 mesh size) and extraction solvents (Optima grade) were purchased fi om Fisher Scientific (Pittsburgh, Pennsylvania). Fipronil (( )-5-amino-l-(2,6-dichloro-a,a,a-trifIuoro-/7-tolyl)-4-trifluoromethylsulfinylpyrazole -3-carbonitrile) and the metabolites fipronil sulfide (A) [5-amino-1-(2,6-dichloro-a, a, oc-trifluoro-/ -tolyl)- 4-trifluoromethylthiopyrazole-3-carbonitrile], fipronil sulfone (B) [5-amino-l-(2,6-dichloro-a, a, a-trifluoro-/7-tolyl)-4-tri-fluoromethylsulfonylpyrazole-3-carbonitrile], and desulfinyl fipronil (C) [5-amino-1 -(2,6-dichloro-a, a, a-trifluoro-p-tolyl)- 4-trifluoromethylpyrazole-3-carbonitrile] were the US EPA standards with respective purities of 99.4%, 99.8%, 99.7%, and 98.5%. 

The reference dose (RfD) and acceptable daily intake (ADI) for fipronil are both 0.0002 mg kg day RfD and ADI values for fipronil-desulfinyl are about an order of magnitude lower, 0.00003 and 0.0002, respectively. 

Hainzl, D. and J.E. Casida. Fipronil insecticide novel photochemical desulfinylation with retention of neurotoxicity. Proc. Natl Acad. Sci. USA 93 12764-12767, 1996. 

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