An efficient and sensitive method for simultaneous determination of the insecticide fipronil and its main metabolites fipronil desulfinyl, fipronil sulfide and fipronil sulfone in surface water was developed and validated. Fipronil and its metabolites were determined by gas chromatography with electron capture detection (GC-ECD) after a preconcentration step using solid phase extraction (SPE). The evaluated validation parameters included analytical curve and linearity, limit of detection (LOD) and quantification (LOQ), precision and accuracy. GC-ECD presented a good response for fipronil and its metabolites, and all analytical curves showed determination coefficients higher than 0.995. The LOD values of the method were 2.5 ng L-1 for fipronil and 2.0 ng L-1 for each metabolite. All recovery values were between 81.3 and 112.3%, with relative standard deviation (RSD) values lower than 14.2%. The proposed method was successfully applied to the analysis of water samples from flooded rice fields.
pesticide residues; fipronil; metabolites; solid phase extraction
