APPLICATION OF IMMUNOASSAYS FOR THE HERBICIDES, MOLINATE AND DIURON, TO FIELD WATER ANALYSIS

Immunoassays based on microwells (for laboratory assay) and polystyren e tubes (for field assay) have been applied to the analysis of the her bicides, molinate and diuron, in field water samples. Development of a new immunoassay format for molinate, with detection limits of 0.5-1 p pb, enabled for the first time, the direct analysis of molinate in wat er samples across the full range of usual field residue levels, withou t need for pre-concentration. A highly sensitive field assay for urea herbicides (diuron limit of detection of 0.15 ppb) has also been devel oped based on a double-layer coating with protein A and urea herbicide -specific antibody. Each assay was only slightly affected by ions and turbidity, which are often problems in subsurface and surface water ma trices respectively. For both formats of the molinate and diuron immun oassays, close correlations were obtained between herbicide levels det ermined by the immunoassay and by instrumental analysis, using field w ater samples.