API Support

Accurately weigh 2.0 g of homogenized sample into a 10 mL polypropylene centrifuge tube, then add 20 µL of 1.0 mg/L fipronil-13C2 15N2 and 4.0 mL of acetonitrile. Vortex the tube vigorously for 10 minutes to ensure better interaction between the solvent and the sample, then centrifuge at 10,000 g for 3 minutes. Collect the supernatant and transfer it to a new 10 mL polypropylene tube. Extract the residue again with 4 mL of acetonitrile, then centrifuge. Finally, combine the supernatants and dilute with acetonitrile to achieve a final volume of 10 mL for further cleanup procedures.
Analytical Performance
Spike fipronil-13C2 15N2 (2.0 µg/L) into blank fish samples and construct a calibration curve with concentration ranges for fipronil, fipronil sulfide, and fipronil sulfone of 0.05-10.0 µg/L, and for fipronil desulfinyl of 0.20-50.0 µg/L. The linearity for all analytes was found to be adequate, with determination coefficients (R2) greater than 0.9991. The limits of quantification (LOQ) for fipronil, fipronil sulfide, and fipronil sulfone were 0.40 µg/kg each, and for fipronil desulfinyl, it was 2.0 µg/kg. The method exhibited good precision, with relative errors (RE) less than 12.5%, and intra-day and inter-day relative standard deviations (RSD) less than 11.4%. Recovery rates for fipronil and its metabolites at three levels of spiking