Simultaneous determination of deltamethrin, permethrin and malathion in stored wheat samples using continuous sample drop flow microextraction followed by HPLC–UV

Abstract

Wheat (Triticum aestivum) is an important staple food worldwide used for the manufacture of flour-derived foodstuffs such as bread and noodles. The purpose of this study was to investigate common pesticides in stored wheat at Kermanshah province’s silos in Iran. Continuous sample drop flow microextraction coupled with high-performance liquid chromatography–ultraviolet (HPLC–UV) detection was applied for this purpose. In this technique, a few microliter of organic solvent is transferred to the bottom of a conical test tube and the aqueous solution transforms in form fine droplets while passing through the organic solvent. After extraction, 20 μL of organic solvent containing target analytes was injected into the HPLC–UV. The extraction conditions (including type and volume of extraction solvent, sample solution flow rate, sample solution volume, pH and salt addition) were varied to achieve optimized performance. Under the optimum conditions, the calibration graphs are linear in the range of 0.5–1000 µg kg−1 and limit of detections (LODs) are in the range of 0.2–0.5 µg kg−1. Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 100 µg kg−1 of target pesticides were in the range of 3.2–5.1% and 4.7–7.2%, respectively. Three out of 36 wheat grain samples contained permethrin exceeding safety levels, but the levels of the other two pesticides in all samples were below the maximum residue levels based on Europe standard level.