Analysis of eight pyrethroids in water samples by liquid-liquid microextraction based on solidification of floating organic droplet combined with gas chromatography

A novel method was developed for the determination of eight pyrethroids in water samples by liquid liquid microextraction based on solidification of floating organic droplets followed by gas chromatography with electron capture detection. The type and volume of the extraction solvents, extraction time, sample solution temperature, stirring rate and ionic strength were studied and optimized. Under the optimum conditions, enrichment factors ranged from 824 to 1,432, and the limit of detection range from 2.0 to 50 ng.L-1. The calibration graph is linear from 0.15 to 80 mu g.L-1 for cyfluthrin, fenvalerate, fluvalinate and deltamethrin, 0.09 to 80 mu g.L-1 for fenpropathrin, 0.006 to 80 mu g.L-1 for lambda-cyhalothrin, 0.026 to 80 mu g.L-1 for pennethrin, 0.01 to 80 mu g.L-1 for cypermethrin. The correlation coefficients (r) varied from 0.9961 to 0.9988. The method was successfully applied to the determination of pyrethroid pesticide residues in tap water, well water, reservoir water, and river water. Recoveries ranged from 79.0% to 113.6%, and relative standard deviations are between 4.1% and 8.7%.