A green and sensitive hydrophobic deep eutectic solvent dispersive liquid-liquid microextraction coupled with gas...

Conventional extraction of organophosphorus (OP) pesticides from necrophagous larvae relies on toxic chlorinated solvents, risking environmental and analyst safety. To address this, we developed a green dispersive liquid-liquid microextraction using a hydrophobic deep eutectic solvent (HDES) as a sustainable alternative. For detection, gas chromatography-electron capture detector (GC-ECD) was chosen for its moderate cost relative to gas chromatography-mass spectrometry, while maintaining robust and accurate quantification. The HDES (menthol:octanoic acid, 1:1) was characterized for its organic composition, thermal behavior, and physicochemical properties. A 150 μL aliquot of HDES dispersed in 1000 μL acetonitrile was injected into aqueous larval samples (pH 6-7), followed by GCECD. The linear ranges for dimethoate, diazinon, malathion, and chlorpyrifos were 100-1000 μg/kg, 50-500 μg/kg, 50-500 μg/kg, and 20-120 μg/kg, respectively, with coefficients of determination (R²) exceeding 0.99 for all analytes. The lower limits of quantitation were 100, 50, 50, and 20 μg/kg for dimethoate, diazinon, malathion, and chlorpyrifos, respectively. Extraction recoveries ranged from 81.5% to 95.3%, and the intra- and inter-day relative standard deviations for all analytes were below 20%. In simulated larval specimens, all the target compounds were separated within 9.0 min. The method achieved Analytical Eco-Scale and Analytical Greenness scores of 82 and 0.64, confirming excellent eco-friendliness. Thus, this HDES-DLLME-GC-ECD method offers a green, cost-effective, and sensitive tool for simultaneous determination of dimethoate, diazinon, malathion, and chlorpyrifos in necrophagous larvae, well suited for forensic entomotoxicological investigations.