Evaluation of Enzyme Linked Immunosorbent Assay (ELISA) for Diaminoatrazine Analysis of Water Samples in Comparison to Gas Chromatography

In Wisconsin the widespread use of the herbicide atrazine has led to the presence of atrazine and it’s metabolites in some groundwaters. One of the metabolites, diaminoatrazine, is of particular interest because it is reported to pose a greater health threat (to those drinking the water) than the other metabolites. Diaminoatrazine can be measured by conventional gas chromatography techniques, but the test is time consuming, expensive, and less robust than desirable. However, a new test for diaminoatrazine, using enzyme linked immunosorbent assay (ELISA) technology, has been commercially developed (although it is not yet on the market). The purpose of the present study was to evaluate this new ELISA by comparing the results of split samples analyzed by both the new ELISA and the conventional technique. Approximately 70 groundwater samples from Wisconsin wells, many of which were known by the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) to be contaminated by atrazine and atrazine metabolites, were collected and split. DATCP’s laboratory analyzed one set of the split samples using conventional extraction and chromatographic analysis techniques. The other set of split samples were analyzed using the new diaminoatrazine ELISA. This same set of samples was also analyzed by an atrazine ELISA, a test that has been in use for about ten years. The results indicate that while the new diaminoatrazine ELISA produces results that correlate with conventional measurements, the ELISA produced results that were higher (usually about double) than results obtained from the conventional technique. The higher results may relate to the fact that atrazine (parent compound) can cross react (i.e., the new ELISA is not as specific to diaminoatrazine as desired). The new diaminoatrazine atrazine ELISA appears to be very sensitive, as it detected the presence of diaminoatrazine (or possibly cross reactants) when the conventional technique was not able to detect it. Some samples in which neither atrazine nor any of its metabolites could by detected by conventional gas chromatography had detects using the diaminoatrazine ELISA. Interestingly, total atrazine measured by the conventional GC technique (sum of the parent compound plus all metabolites measured) gave similar results to the sum of the diaminoatrazine ELISA and the older atrazine ELISA for the samples studied. Despite the fact that the new diaminoatrazine ELISA does not produce the same results as conventional analyses, it still could be a useful (and relatively inexpensive) test for determining waters that could contain the diaminoatrazine metabolite (and thus pose an elevated drinking water health risk).