Enzyme immunoassays for picloram detection: A comparison of assay formats

Two direct enzyme immunoassays for picloram (4‐amino‐3,5,6‐trichloro‐2‐pyridinecarboxylic acid) detection were developed. The assay using IgG isolated from a rabbit antipicloram antiserum had a working range from 5 to 5000 ng ml^?1 with a mean I₅₀ value of 180 ng mh^?1 and a limit of quantification of 10 ng ml^?1. The assay using a monoclonal anti‐picloram antibody had a working range from 1 to 200 ng mh^?1 with a mean I₅₀ value of 18 ng mh^?1 and a limit of quantification of 5 ng ml^?1. The direct assays were compared to an existing monoclonal antibody‐based indirect enzymes immunoassay for accuracy and precision of picloram determinations in fortified ground and surface waters. In both matrices, the monoclonal antibody‐based indirect enzyme immunoassay was shown to be the superior format in terms of greater precision and equal or greater accuracy.