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

In our previous study, polyclonal antibodies against the organophosphorus insecticide isofenphos were generated and enzyme-linked immunosorbent assays (ELISAs) for this pesticide were developed. In this study, isofenphos ELISAs with higher performance were developed by using a monoclonal antibody and a larger number of immunoreagents. Using the antibody and a coating antigen, an indirect competitive ELISA for isofenphos was developed, which showed an IC50 value of 35 ng/mL with a detection limit of 5.8 ng/mL. A direct competitive ELISA using an enzyme tracer was also developed, which showed an IC50 value of 26 ng/mL with a detection limit of 4.8 ng/mL. The antibodies in both assays showed negligible cross-reactivity with other OP pesticides. Recoveries of isofenphos from fortified rice and lettuce samples ranged 30-328 and 52-197%, respectively. The bias in the recovery values was rationalized by using the standard curves obtained in the matrix extract.