Enzyme-linked immunosorbent assay for paraquat and its application to exposure analysis

An enzyme-linked immunosorbent assay (ELISA) was developed for the determination of paraquat in human exposure samples. Using an antibody dilution of 1/5000, concentrations of paraquat cation in the range 0.1-27 ng/mL could be measured. Limit of detection ranged from 0.1 to 1.0 ng/mL depending on the matrix analyzed. The method had good precision, with less than 5% between-run and less than 4% within-run variation, and was selective for paraquat showing minimal cross reactivity with ethylparaquat, diquat, and other compounds. In comparison with a gas chromatographic method, the ELISA gave higher recoveries, was less labor intensive, and was more sensitive. The ELISA was applied to paraquat in high volume glass fiber filters, personal air monitors, worker clothing patches, and hand washes collected during aerial spraying of cotton. When the same filters were analyzed by both ELISA and GC, the ELISA consistently resulted in higher values in keeping with the greater efficiency of the sample preparation steps of ELISA.