Rapid Detection of Four Organophosphorous and Neonicotinoid Toxicants Using Bi-enzyme Tracer Competitive Enzyme-Linked Immunosorbent Assay

Abstract

A bi-enzyme tracer direct competitive enzyme-linked immunosorbent assay (dc-ELISA) based on two generic antibodies was developed. The effects of several physicochemical factors, such as heterologous antigen–horseradish peroxidase (HRP), methanol concentration, ionic strength, and pH value, were optimized to obtain satisfactory sensitivity of the assay. Under the optimized conditions, the 50 % inhibition concentration (IC₅₀) value for parathion, parathion-methyl, imidaclothiz, and imidacloprid was 57.28 ± 2.73, 169.82 ± 5.64, 52.48 ± 3.46, and 53.08 ± 2.05 μg L⁻¹, with a limit of detection (LOD, IC₁₀) of 0.56, 3.16, 0.62, and 0.51 μg L⁻¹, respectively. There was no obvious cross-reactivity (CR) with most of the neonicotinoids and organophosphorus pesticides. The recoveries of parathion, parathion-methyl, imidaclothiz, and imidacloprid in environmental and agricultural samples, including river water, soil, and cabbage, ranged from 82.54 to 116.29 %. The relative standard deviation (RSD) ranged from 1.59 to 8.09 %. The ELISA results were confirmed by gas chromatography (GC) with a high correlation coefficient of 0.9882. These results showed that the bi-enzyme tracer competitive enzyme-linked immunosorbent assay could be used as a sensitive tool for monitoring parathion, parathion-methyl, imidaclothiz, and imidacloprid in environmental samples and agricultural products.