Ultrasound-assisted dispersive liquid-liquid microextraction based on a hydrophobic deep eutectic solvent for the preconcentration of pyrethroid insecticides prior to determination by high-performance liquid chromatography

Abstract

In this study, a green and effective ultrasound-assisted dispersive liquid-liquid microextraction method based on a hydrophobic deep eutectic solvent (UA-DLLME-DES) was developed for the preconcentration and determination of pyrethroid insecticides (deltamethrin, fenvalerate, permethrin, etofenprox, and bifenthrin) in environmental water samples using high-performance liquid chromatography combined with an ultraviolet detector (HPLC-UVD). Hydrophobic deep eutectic solvents (DESs) are green solvents prepared by mixing quaternary phosphonium salts and straight-chain monobasic acids. DESs were synthesized and characterized by Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). Several key parameters, including the types and amounts of DESs, pH value, sample volume, ultrasound time, salt addition, and centrifugation rate and time, were researched and optimized. Under the optimal experimental conditions, the proposed method required only a small amount of DES to complete extraction and recovery in a very short time. The validated method showed good linearity, with a coefficient of determination (R2) ranging from 0.9992 to 0.9995, and good repeatability, with relative standard deviations (RSDs) ranging from 1.45 to 4.86%, for all analytes. The limits of detection (LODs) varied from 0.30 to 0.60 μg/L. Finally, the presented method was implemented to determine the pyrethroid insecticides in environmental water samples, and acceptable recoveries within the range of 80.93–109.88% were obtained.