atrazine MCL. Stratified data suggests that the ELISA diaminoatrazine method would be
a good choice for screening private water samples.
Table 7 shows the results of the two different ELISAs performed on randomly chosen
private well water samples (i.e., there was no known history that these wells might
contain high levels of atrazine or atrazine metabolites). The table shows that some
diaminoatrazine would be missed if only the atrazine ELISA were used to test the
samples. Six samples (out of eleven total) indicated measurable concentrations of
diaminoatrazine were present while none of the samples measured by the atrazine ELISA
produced detects. No GC results were run for this set of samples. One sample had a
diaminoatrazine concentration of 0.55 ppb. So this further suggests that the
diaminoatrazine might be a useful screen. From a regulatory perspective, perhaps a
concentration for the diaminoatrazine ELISA could be established whereby samples with
concentrations less than that value would have very little chance of having a total atrazine
concentration greater than the MCL. For example, there are no sample cases in table 3
with ELISA diaminoatrazine concentrations less than 1.0 ppb that have GC total atrazine
concentrations greater than the MCL.
Overall the new diaminoatrazine ELISA is straightforward to perform, the test following
a similar procedure as other ELISAs. The test is inexpensive to perform compared to
conventional gas chromatographic procedures. Interpretation of the results is
complicated by fact that other triazine compounds, including the parent compound
atrazine, can cross react. Nevertheless, given the public health concern for
diaminoatrazine, the test, which was found to respond to very low concentrations of
diaminoatrazine, the ELISA test might be used as valuable screening tool or as a
supplemental analysis. More specific conclusions are given below.
1. While the new diaminoatrazine ELISA correlates with conventional gas
chromatographic measurements of diaminoatrazine, the ELISA produced results
that were generally higher (about double) than those obtained from gas
2. Some samples in which neither atrazine nor any of its metabolites could be
detected by conventional gas chromatography, had detects using the
diaminoatrazine ELISA.
3. Total atrazine measured by the conventional GC technique (sum of the parent
compound concentration and the concentration of all detected metabolites) gave
similar results to the sum of the diaminoatrazine ELISA concentration and the
older atrazine ELISA for the samples studied.
It is hoped that the ELISA diagnostic test industry will soon develop kits that will
simultaneously detect multiple compounds and avoid the problem of cross-reactivity.
Assays using Immuno-flourescent conjugates have been developed for other classes of
analytes using differing wave lengths of light on various analyte-conjugates that can
detect and quantify several components in one pass through the immunoassay system.