Optimization of a QuEChERS Based Analytical method for the Determination of Organophosphorus and Synthetic Pyrethroid Pesticide Residues in Betel Leaf

ABSTRACT A novel method has been developed and validated for the first time in order to determine eight pesticide residues (acephate, diazinon, malathion, fenitrothion, chlorpyrifos, quinalphos, dimethoate and cypermethrin) in betel leaf using quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction in combination to Gas Chromatography (GC) coupled with Flame Thermionic Detector (FTD) and Electron Capture Detector (ECD). In this study, the optimisation of cleanup materials was done properly and found that 600 mg anhydrous MgSO4, 150 mg activated charcoal powder, and 120 mg PSA (Primary Secondary Amine) was the best combination for proper cleanup of betel leaf matrix. Recoveries for all the selected pesticides at fortification levels of 0.02, 0.1, and 0.3 mg/kg ranged from 86% to 108% with RSDr ≤ 9% and the matrix matched calibration curve showed good linearity (r2 ≥ 0.996). The limit of detection ranged from 0.003 to 0.005 mg/kg and the limit of quantification was 0.02 mg/kg, which was lower than the EU-MRLs. The matrix effects of the selected pesticides were also evaluated in this study and found that cypermethrin had a prominent matrix effect (+124%). The proposed method was applied successfully to analyse 110 fresh betel leaf samples and found that 12 were contaminated with cypermethrin, chlorpyrifos, and dimethoate at a level above EU-MRLs. The consumers are at high health risk as the detected levels of cypermethrin and chlorpyrifos residues were up to 78 and 39 times higher than the EU-MRLs, respectively, and the estimated highest Health Risk Index (HRI) was 5.40.