Optimization of soil-based QuEChERS extraction and comparative assessment of analytical efficiency by physicochemical...

This study aimed to optimize the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) extraction method specifically tailored for pesticide residue analysis in soil samples and to establish standardized soil sample criteria for enhanced analytical reliability. Initially, twelve QuEChERS extraction reagent combinations were evaluated using TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) analysis, resulting in the selection of an optimal condition (MgSO₄ 6 g + calcium acetate 1.5 g) that effectively minimized soil particle interference and improved purification efficiency. The analytical performance under varying soil physicochemical conditions (pH, organic matter, clay content) was systematically assessed, revealing significant impacts primarily in soils with high organic matter (≥3 %) and clay content (∼30 %). Consequently, these challenging conditions were established as representative worst-case scenarios for method validation. Method validation conducted across three laboratories demonstrated high accuracy and reproducibility, with recovery rates within acceptable limits (70-120 %) for 98 % of 489 pesticides tested and relative standard deviations (RSD) below 20 % for 95 % of compounds. Application of the optimized method in actual field monitoring of greenhouse soils highlighted significantly higher pesticide residues and associated environmental risk quotients (RQ) compared to open-field soils. Specifically, median pesticide residues in greenhouse soils were markedly higher (0.697 mg/kg) than in open-field soils (0.09 mg/kg), with corresponding RQ medians of 4.5 and 0.6, respectively, indicating heightened environmental risks associated with greenhouse cultivation practices.