Determination of Twenty Organophosphorus Pesticides in Wheat Samples from Different Regions of Iran

Background: Organophosphorus pesticides are widely used in agriculture, homes, gardens, and veterinary practices. Extensive application of pesticides in agriculture often results in residues of these compounds being absorbed into the foods, including wheat. The aim of this study was to evaluate the residue levels of 20 organophosphorus pesticides in wheat samples collected from different regions of Iran. Methods: This research reports a rapid, specific and sensitive multiresidue method based on the Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method and gas chromatography with mass spectrometric detection in the selected ion monitoring mode (GC– SIM–MS) to evaluate 20 organophosphorus pesticides in wheat samples. Results: In the concentration range of 20-200 ng/g, the calibration curves for each analyte was linear with a determination coefficient (R2) of 0.993 to 0.999. The limits of detection (LODs) and quantitation (LOQs) were between 2.5-6.7 and 7.5-20 ng/g, respectively. The mean recoveries obtained for three fortification levels (25, 50 and 100 ng/g, five replicates each) were 80-114% with a satisfactory precision (RSD<20%). 31.1% samples contained residues of one or more target compounds. Chlorpyrifos was the most common residue (17.8%), followed by pirimiphos-methyl (6.7%), diazinon (4.4%), chlorpyrifos-methyl (1.1%) and malathion (1.1%). Conclusion: Among the detected pesticides, only diazinon and malathion are permitted pesticides for wheat production in Iran. However, their concentrations were below the maximum residue levels (MRLs) established by the Iranian National Standard Organization (INSO).