Influence of the ELISA Format and the Hapten-Enzyme Conjugate on the Sensitivity of an Immunoassay for s-Triazine Herbicides Using Monoclonal Antibodied

A variety of formats for enzyme-linked immunosorbent assays have been examined for the analysis of environmental samples using a single monoclonal antibody raised to the herbicide atrazine. The most favorable combination of several ELISA formats and a variety of synthesized hapten-enzyme conjugates resulted in a highly sensitive enzyme immunoassay with 50% inhibition (160) at 0.25 pg/L and a detection limit of 0.03 pg/L. This assay is the most sensitive atrazine assay, based on monoclonal antibodies published so far, and can be performed in less than 1 h. All formats were based on the use of haptenenzyme conjugates (enzyme tracers). Direct coating and precoating with goat anti-mouse antibodies or protein A were used. The formats using precoating steps turned out to be the most sensitive. Enzyme tracers based on two different atrazine and simazine haptens each with two different spacers (Cg or CS) were conjugated using either alkaline phosphatase or horseradish peroxidase. The atrazine derivative with the CS spacer arm conjugated to horseradish peroxidase provided highest sensitivity.