Development and Optimization of a Dispersive Liquid-Liquid Microextraction Method for the Simultaneous Determination of Multiclass Pesticides in Environmental Waters.

The widespread use of pesticides in modern agriculture necessitates sensitive and sustainable methods to monitor their residues in environmental waters. This study reports the development and optimization of a dispersive liquid-liquid microextraction (DLLME) method combined with high performance liquid chromatography with diode array detector (HPLC-DAD) for the simultaneous determination of multiclass pesticides (metalaxyl, benalaxyl, chlorpyrifos, endrin, 4,4'-DDT and bifenthrin). Key extraction variables-including the type and volume of extraction/disperser solvents, pH, salt addition and vortex speed/time-were systematically evaluated. The optimized method employed tetrachloroethylene as the extraction solvent, acetonitrile as the disperser, pH 7, 3% w/v NaCl, a vortex speed of 1200 rpm and an extraction time of 80 s. Under these conditions, excellent enrichment factors, recoveries (87%-108%) and precision (intradays: 2.8%-8.6%; interday: 4.2%-8.6%) were achieved. The correlation coefficients (r 2) exceeded 0.9977, and the limits of detection ranged from 0.3 to 1.3 µg/L. Compared to conventional extraction techniques, the proposed DLLME method provides faster analysis and uses less solvent. This approach provides a robust, sensitive and environmentally friendly alternative for monitoring multiclass pesticide residues in diverse water matrices.