Extraction Efficiency and HPLC Determination of Imidacloprid in Soil

Two extraction methods were successfully applied to study the extraction of imidacloprid from soil. The first method, using a mix of acetone and hexane, was based on Soxhlet extraction, and the second method, using acetonitrile, methanol, and water, was a modified version of a liquid extraction method. Quantification was performed by reversed-phase High Performance Liquid Chromatography (HPLC) with Diode Array Detection (DAD) at 270 nm using 40:60 (v/v) acetonitrile/water as a mobile phase. The mean recoveries for imidacloprid from soil ranged from 82.6 to 109%, with a relative standard deviation between 1.9 and 5.6% for both extraction methods. The detector linearity and the reproducibility of the method proved to be very precise. The limits of detection were 0.08 and 0.06 mg kg−1 for liquid extraction and Soxhlet extraction, respectively. Overall, the efficiency of the Soxhlet extraction at lower concentrations was better than at higher concentrations, while liquid extraction proved efficient for all spiked levels. Liquid extraction performed better at higher concentrations compared to Soxhlet extraction. Taken together, our study suggests that the analysis of imidacloprid in soil can be performed with the modified liquid extraction method with a higher recovery and a lower RSD than Soxhlet extraction.