Fast dispersive liquid–liquid microextraction of pesticides in water based on a thermo-switchable deep eutectic solvent

Accurate measurements of pesticide levels in the environment are necessary to set policies, yet actual analytical methods are limited by the use of toxic solvents and tedious procedures. Here, we used a thermo-switchable deep eutectic solvent, a mixture of oleic acid and lidocaine in dispersive liquid–liquid microextraction to improve the extraction of four organophosphorus pesticides and five pyrethroids in simulated water samples. Concentrations were measured by high-performance liquid chromatography. Results show that the deep eutectic solvent can be dispersed by shaking and aggregated by heating in the water during the extraction process, which shortened the extraction time to 5 min. Concentrations were measured with good precision, 0.8–9.7% standard deviation, and low detection limit of 0.16–0.81 µg L−1. Analysis of natural river waters spiked with pesticides showed 81–113% recovery.