Accuracy and interferences for enzyme-linked immunoassay tests for atrazine

Enzyme-linked immunosorbent assay (ELISA) methods have become a common alternative to gas chromatography methods for analyzing atrazine in raw and finished drinking water. This study investigated several leading ELISA atrazine test kits currently in use. This work demonstrates that although all the kits analyzed provided precise results, their accuracy varies greatly between kits and water matrixes. In most cases, the ELISA test kits provided positively biased results, although some negatively biased results were also observed. That is, the ELISA atrazine concentrations were usually greater than the actual concentrations. Although a part of this positive bias was because of cross-reactivity with other chloro-s-triazines in the water matrix, much of the observed interference appeared to be related to natural organic matter, chlorination and/or quenching, and other factors. Even though the observed positive bias tends to cause the kits to provide a conservative result with respect to atrazine concentration, the role of ELISA test kits for regulatory purposes requires more study and discussion.