Quantitation of paraquat in biological samples by radioimmunoassay using a monoclonal antibody

We have developed a sensitive and specific radioimmunoassay for the quantitative determination of paraquat in plasma, urine, and bronchoalveolar lavage fluid using a monoclonal antibody. The synthesis of the iodinated paraquat tracer is novel and less complicated than a previously reported method. Regardless of the type of biological sample analyzed, the sensitivity of the assay was 0.46 ng/ml in a 200-μl aliquot. The results correlated well with those of another assay performed in a separate laboratory. Paraquat concentrations were determined in plasma and in urine of a dog over several days after the intravenous administration of 7.48 mg paraquat cation/kg and in bronchoalveolar lavage fluid obtained 34 hr after the 2-hr infusion was discontinued. Concentrations of paraquat measured ranged from 14.1 to 0.03 μg/ml in plasma and 2034 to 0.36 μg/ml in urine. Concentrations of paraquat in plasma obtained at various times after the ingestion of paraquat by three patients ranged from 51.0 to 0.010 μg/ml.