An Enzyme Linked Immunosorbent Assay (ELISA) has been developed for the estimation of paraquat. The amount of paraquat present in samples of human plasma was estimated in terms of the degree to which it combined with a rabbit antibody raised to a conjugate to paraquat with bovine serum albumin. The amount of residual, uncombined, antibody after being allowed to react with a conjugate of paraquat with keyhole-limpet haemocyanin bound to the surface of a polystyrene micro-titre plate, was estimated by the addition of an enzyme-labelled anti-rabbit IgG, followed after washing by addition of substrate and subsequent determination of optical density. Concentrations of paraquat in the range 0.3-10 ng/ml could be measured and the antibody showed a high degree of specificity. Results correlated well with those of a widely-validated radio-immunoassay but the ELISA was simpler and more sensitive.
