Abstract
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.