Potential application of immunoassays for simple, rapid and quantitative detections of phytoavailable neonicotinoid insecticides in cropland soils

Abstract

This study evaluated the applicability of commercially available kit-based enzyme-linked immunosorbent assay (ELISA) to simple, quick, and quantitative detection for three water-extractable (phytoavailable) neonicotinoid insecticides: dinotefuran, clothianidin, and imidacloprid in soils. ELISA showed excellent analytical sensitivity for determination, but with cross-reaction to structurally related neonicotinoid analogues, which might produce false positives. To analyze insecticides in soil samples of diverse physicochemical properties, they were extracted with water. The aqueous soil extracts were assayed directly with ELISA. No matrix interference was observed without additional dilution with water. Recovery experiments for the insecticides from aqueous soil extracts spiked at 2-10 ng/mL showed good accuracy (72-126%) and precision (<16%). Kit-based ELISAs were used to estimate soil-water distribution coefficients (Kd). Values estimated using this method showed positive correlation between organic carbon contents in soil and those for evaluated insecticides. Results indicate that the evaluated kit-based ELISA has applicability for simple, quick, and reliable detection of phytoavailable insecticides in soils and for estimating Kd values in soil.

Keywords: Enzyme-linked immunosorbent assay; Matrix interference; Organic solvent-free analysis; Soil–water distribution coefficients; Water-based extraction.