In House Laboratory Method Validation and Uncertainty Determination of 28 Pesticides in Spinach by Gas Chromatography Using Electron Capture (ECD) and Mass Spectrometric (MS) Detector

Study conducted to develop and validate laboratory method using QuEChERS method. QuEChER method was used for the determination of 28 pesticide residues belongs to organochlorine, synthetic pyrethroids and herbicides in Spinach. Sample was extracted by ethyl acetate. Removal of moisture using from sample extract by anhydrous sodium sulphate and magnesium sulphate. Cleaning of matrix and other interferences was done by Primary Secondary Amine (PSA), C18 and activated charcoal. Agilent 7890B model GC-ECD with 7693 auto sampler and 7890A-Agilent Technologies GC with 5975C inert XL EI/CI MSD triple axis mass detector with DB-5MS fused silica capillary column were used for analysis of samples taken for study. Each pesticide spiking concentration was 0.05 ppm level in three replicate whose recovery lies between Codex permissible limit i.e. 70–120%. Relative standard deviation (RSD) < 15%. Codex norms were followed for repeatability and reproducibility check of the instrument. For Linearity check, taking area of lambda cyhalothrin against five different concentration levels of 0.003, 0.010, 0.100, 0.70, 1.00 mg/kg, calibration curve was plotted with regression co-efficient (r²) 0.993. Total uncertainty or combined uncertainty comprise of three main independent uncertainties arise due to weighing of standards, purity of the standard and repeatability of instruments. Expanded uncertainty is twice of the combined uncertainty which lies in three ranges viz., (a) ≤10% (b) 11–15% and (c) 15–20%. All pesticides taken for study were in the range (a) i.e. ≤10%.