Development of an Enzyme-Linked Immunosorbent Assay for Residue Analysis of the Insecticide Emamectin Benzoate in Agricultural Products

A direct competitive enzyme-linked immunosorbent assay (dc-ELISA) for the analysis of emamectin residues in agricultural products was developed using a prepared mouse monoclonal antibody. The working range was 0.3−3.0 ng/mL, and the 50% inhibition concentration (IC50) was 1.0 ng/mL. The assay was sufficiently sensitive for analysis of the maximum residue limits in agricultural products in Japan (>0.1 μg/g). Emamectin residues contain the following metabolites: the 4′′-epi-amino analogue, the 4′′-epi-(N-formyl)amino analogue, the 4′′-epi-(N-formyl-N-methyl)amino analogue, and the 8,9-Z isomer. The dc-ELISA reacted with these compounds at ratios of 113, 55, 38, and 9.1% of the IC50 value of emamectin benzoate. Seven kinds of vegetables were spiked with emamectin benzoate at concentrations of 15−300 ng/g, and the recoveries were 91−117% in the dc-ELISA. The dc-ELISA results agreed reasonably well with results obtained by liquid chromatography−tandem mass spectrometry (LC-MS/MS) using spiked samples and actual (incurred) samples. The results indicate that the dc-ELISA was useful for the analysis of emamectin benzoate residues in agricultural products.