Monoclonal antibody-based enzyme-linked immunosorbent assays for the detection of the organophosphorus insecticide diazinon

Four haptens of the organophosphorus (OP) insecticide diazinon were synthesized to develop enzyme-linked immunosorbent assays (ELISAs) for this pesticide. One of them was conjugated to KLH to be used as the immunogen for production of monoclonal antibodies. By using the antibodies and a coating antigen, an indirect competitive ELISA was developed, which showed an IC₅₀ of 4.0 ng/mL with a detection limit of 0.7 ng/mL. A direct competitive ELISA using an enzyme tracer was also developed, which showed an IC₅₀ of 6.0 ng/mL with a detection limit of 0.9 ng/mL. The antibodies in both assays showed negligible cross-reactivity with metabolites of diazinon and other OP pesticides. Recovery of diazinon from fortified lettuce and rice samples was satisfactory except at the fortified concentration of 100 ppb.