Development of an enzyme-linked immunosorbent assay for the insecticide imidacloprid

Enzyme-linked immunosorbent assays (ELISAs) were developed for imidacloprid, a neonicotinoid insecticide. Haptens were designed in such ways that spacer arms were introduced on either the pyridinyl or the imidazolidinyl ring of imidacloprid. Two sets of polyclonal antibodies were raised from rabbits immunized with two different immunogens and were characterized with an indirect ELISA format. Cross-reactivities and effects of organic solvents on the assays were evaluated. One set of antibodies shows approximately equal cross-reactivities to imidacloprid and its major metabolites with half-maximum inhibition concentrations (I(50)) of 73-88 ppb. Another is specific to imidacloprid with an I(50) of 35 ppb. The assay was initially applied to the analysis of imidacloprid in fortified water, coffee cherry, and bean extracts.