Determination of four pyrethroid insecticides in water samples through membrane emulsification-assisted liquid–liquid microextraction based on solidification of floating organic droplets

A novel membrane emulsification-assisted liquid–liquid microextraction method based on the solidification of floating organic drops was used to detect four pyrethroid pesticides (deltamethrin, etofenprox, fenpropathrin, and bifenthrin). In this method, [P₄₄₄₁₂]Br was used as a surfactant that could be removed from water via the addition of KPF₆. The extraction solvent was separated after centrifugation and solidification on the water surface. The parameters affecting the recovery of the target compounds, including the surfactant amount, [P₄₄₄₁₂]Br-to-KPF₆ molar ratio, addition of salt, extraction solvent volume, and temperature, were individually optimized and further analyzed through an orthogonal array design (OAD) experiment. The optimized conditions were based on the results of the OAD experiment and single-factor analysis. Using these experimental conditions, the recovery of the four pyrethroids ranged from 91.3% to 98.1% with relative standard deviation (RSD) values ranging from 1.7 to 2.2%. Good linearity was observed, with values from 0.9982 to 0.9997, and the linear range was between 1 and 500 μg/L (5–500 μg/L for fenpropathrin). The limit of detection (LOD) values based on a signal-to-noise ratio (S/N) of 3:1 were 0.37–0.75 μg/L. The enrichment factor ranged from 90 to 96. Therefore, this method is suitable for the determination of pyrethroid pesticides in environmental water samples.