VALIDATION OF A MONOCLONAL IMMUNOASSAY FOR DIURON IN GROUNDWATER

Diuron is one of the most heavily used herbicides in California, and w ell water and surface water are routinely monitored for diuron residue s. In a previous paper, we described haptens and monoclonal antibodies suitable for quantitative competition enzyme immunoassay (EIA) of diu ron. This paper documents the design and results of a study conducted with 49 blind-coded groundwater samples, analyzed by high-pressure liq uid chromatography (HPLC) and EIA. Diuron residues were recovered usin g a C-18 solid-phase extraction (SPE) protocol that also is applicable to the recovery of simazine, atrazine, prometon, and bromacil. To min imize analyst errors, all SPE and EIA steps were performed on automate d equipment. Overall correlation of the EIA and HPLC results was r(2) = 0.95, with a low bias in the EIA (ppb estimated by EIA = 0.77 x ppb estimated by HPLC). The detection limits of the EIA and HPLC were appr oximately 0.07 and 0.1 ppb, respectively. There were no false positive s or false negatives in the EIA. The results indicate that the residue extraction and EIA protocols are suitable for initial screening for c ompliance monitoring of diuron. The protocols are potentially adaptabl e to multiresidue screening for leachable herbicides in water samples.