Development and validation of a modified QuEChERS-LC-MS/MS method for multi-class pesticide residue analysis in soils...

Soils at pesticide production sites typically exhibit complex mixed contamination profiles characterized by high residual concentrations and strong persistence due to the long-term, iterative production of multiple pesticide classes. However, research on multi-residue analytical methods currently produced mainstream pesticides in such complex matrices remains scarce. In this study, a multi-residue analytical method for 13 classes of pesticides (comprising 55 compounds, -0.7 ≤ logP ≤ 7.3) in soils from pesticide production sites was developed and validated based on a modified QuEChERS approach coupled with liquid chromatography-tandem triple quadrupole mass spectrometry (LC-MS/MS) detection. Suitable extraction and cleanup conditions were screened through a combination of single-factor optimization and interaction experiments, and the performance of the method was evaluated in comparison with a QuEChERS method developed for conventional soil matrices. The results demonstrated that the method achieved satisfactory recoveries for 53 target pesticides in both quartz sand and site soils, with values ranging from 70% to 120% and good precision (RSDs < 20%). The limits of quantification (LOQs) ranged from 0.5 to 5 μg/kg, and the calibration curves showed good linearity (R² > 0.991). Fortified-recovery testing of 21 site-soil samples from seven provinces in China showed reliable determination of 50-54 pesticides. Furthermore, the method was successfully applied to 22 soil samples collected from three pesticide production sites with different production histories, identifying 35 target pesticides. It maintained reliable quantitative performance even under high-residue conditions (1.23 × 10⁷ μg/kg). This study provides a reliable analytical basis for the investigation and risk assessment of mixed pesticide contamination in soils from pesticide production sites.