Dissipation of fipronil granule formulation in sugarcane field soil

The dissipation and persistence of fipronil in soil was studied following application of fipronil (Regent 0.3G) @ 75 and 300 g a.i. ha(-1). The limit of quantification for the analysis of fipronil and its metabolites by gas liquid chromatography was 0.001 mg kg(-1) for soil. The total residues of fipronil and its metabolites in soil after 7 days of its application @ 75 and 300 g a.i. ha(-1) were found to be 0.025 and 0.098 mg kg(-1), respectively. These residues could not be detected after 210 and 240 days following the application of fipronil at lower and higher dosages, respectively. In soil, fipronil was found to be the main constituent, followed by its metabolites sulfone, sulfide, amide and desulfinyl. The presence of sulfone in significant higher amount as compared to other metabolites in the soil clearly demonstrates that oxidation process plays a major role in the metabolism of fipronil. The half-life values (T(1/2)) of fipronil were calculated to be 50.2 and 43.0 days, respectively when applied @ 75 and 300 g a.i. ha(-1).