Comparison of cleanup methods for fipronil and its degradation products in sediment extracts

Gel permeation chromatography (GPC) and solid phase extraction (SPE) were compared for cleaning extracts containing fipronil, fipronil-sulfide, and fipronil-sulfone at sub-ppb concentrations in sediment. With both methods, analytes were extracted using accelerated solvent extraction, and analyzed with gas chromatography equipped with an electron capture detector. The GPC was performed with a Waters Envirogel GPC column with dichloromethane as the mobile phase, while SPE was conducted with dual-layer cartridges containing graphitized carbon black and primary and secondary amines with a mixture of acetone and hexane as the eluting solvent. Method detection limits for fipronil, fipronil-sulfide, and fipronil-sulfone from three sediments with varying organic carbon content ranged from 0.12 to 0.52 μg/kg dry weight, while percent recoveries were 72–119% from sediment aged from 0.24 to 14 d. Although both methods were effective at analyzing fipronil and its degradation products, SPE was the less expensive and less labor-intensive method.