Development of monoclonal ELISAs for azinphos-methyl. 2. Assay optimization and water sample analysis

Two enzyme-linked immunosorbent assays (ELISA) for the insecticide azinphos -methyl have been optimized and characterized. Both ELISAs are based on mon oclonal antibodies produced from an immunogen with a hapten containing a ph thalimido moiety and on protein conjugates of heterologous ligands containi ng a 1,2,3-benzotriazine group. Assay I was performed in the conjugate-coat ed ELISA format and assay II in the antibody-coated format. Several physico chemical factors (ionic strength, pH, incubation times, and Tween 20 and BS A concentrations) that influence assay performance were studied and optimiz ed. Regarding specificity, both monoclonal immunoassays highly crossreacted with azinphos-ethyl and phosmet. Finally, both assays were applied to the analysis of azinphos-methyl in spiked real water samples. For assay I the s ensitivity, estimated as the I-50 value, was 0.40 nM, with a practical work ing range between 0.10 and 1.75 ng/mL and a limit of detection of 0.05 ng/m L. For assay II the sensitivity was 1.01 nM, with a practical working range between 0.32 and 2.54 ng/mL and a limit of detection of 0.08 ng/mL.