QuEChERS-GC-MS/MS Analysis of Multi-Class Pesticide Residues in Tropical Agricultural Soils

The determination of pesticide residues at trace levels in complex environmental matrices requires robust and reliable analytical methodologies. In this study, a multi-residue method for determining 48 pesticides across different chemical classes in agricultural soils was developed and validated using a modified QuEChERS extraction followed by GC-MS/MS analysis. The method exhibited good linearity (R² ≥ 0.9871) over a concentration range of 5-600 µg/kg. Matrix effects were observed for several compounds, requiring matrix-matched calibration for accurate quantification. Recoveries fulfilled the recommended 70-120% criterion in 91.0% of the evaluated cases, while more than 98% of the relative standard deviation values were ≤20%, demonstrating satisfactory overall accuracy and precision according to SANTE/2020/12830 (Rev. 2) guidelines. The validated method was subsequently applied to tropical agricultural soils from Puerto Carreño (Colombian Orinoquia), which exhibited predominantly sandy textures (>80% sand), slightly acidic pH (5.2-5.7), low total organic carbon (0.1-0.8%), and low cation exchange capacity (5.6-8.1 meq/100 g). No pesticide residues were detected in the analyzed samples. The proposed method provides a reliable analytical framework for multi-class pesticide determination in tropical agricultural soils and contributes to the application of QuEChERS-based methodologies in underrepresented tropical soil matrices.