[The development of an enzyme immunoassay for the detection of the herbicide metolachlor in water samples].

Since December 1990, strict limits for pesticide content in drinking water have been in effect in the FRG. These limits have to be enforced and controlled regularly. Because the classical analytical methods, like GC/MS and HPLC are relatively expensive and complicated, concentration and clean up of the samples are necessary. Therefore, the significance of Enzyme Immunosorbent Assays has increased in environmental analysis. The topics of our research are synthesis of suitable Metolachlor conjugates for immunization and as coating antigen, as well as development of an Enzyme Immunosorbent Assay. The chloroacetanilide Metolachlor was coupled with an AMSA-Spacer on Sheep IgG and with AHT-Spacer on BSA. The epitope density was measured photometrically with TNB-derivate. Polyclonal antibodies were produced in white New Zealand rabbits. Metolachlor-AMSA-Sheep IgG conjugate was served as immunogen. The test is indirect and competitive. Microtiter plates are coated with the coating antigen (Metolachlor-AHT-BSA conjugate). In the next step the Metolachlor sample competes with the coating antigen for the antibodies. Detection of bounded antibodies is indirect with a peroxidase-labelled secondary antibody. The chromogenic substrates ABTS, TMB and OPD were tested. TMB showed the best qualities, fast turnover, as well as good and steady colour. Titer of serum and crossreactivity of other chloroacetanilide pesticides and their metabolites were tested. With the exception of Alachlor and Dimethachlor, no pesticide showed a high interaction with serum. Quantitative interpretation was done with the logit/log transformation, which allows comparison of different sera and test series. The antibodies are specific but the affinity is not good enough to detect the limits assigned by the "deutsche Trinkwasserverordnung". Raising the concentration, as is done in classical analytical methods, would solve the problems so that the test can be used as a screening test.