Method Development and Validation of Multiclass Pesticide Residues and Metabolites in Wheat by GC-ECD and GC-MS

A method was developed and validated for analysis of 25 multiclass pesticide residues and their metabolites in wheat grains using GC-ECD for quantification, and GC-MS for confirmation. Samples were treated through a method developed by slight modification in QuEChERS technique. The GC-ECD instrument was calibrated at 6 calibration levels (viz. 0.005, 0.010, 0.050, 0.100,0.250, 0.500 mg/Kg) with regression co-efficient (r²) varying from 0.9993 to 0.9756. Sample preparation include extraction by Acetonitrile solvent (HPLC grade) and clean up by C-18, PSA and anhydrous MgSO₄. Limit of Detection (LOD) of pesticides in wheat matrix varies from 0.002-0.06 μg/g and Limit of Quantitation (LOQ) from 0.004 to 0.2 μg/g. Mean recovery percentage of pesticides at 1 LOQ lies in range of 79.77-128.04 with RSD below 16.35%. Uncertainty measured at three sources–purity of standards, weighing and instrument precision. Maximum expanded uncertainty (2U) falls between the range of 0.0008-0.487.