Enzyme-linked immunosorbent analysis (ELISA) of atrazine in raw and finished drinking water

Enzyme-linked immunosorbent (ELISA) tests are commonly used to measure atrazine concentrations in raw and treated drinking water for monitoring variations in atrazine concentrations, process control (e.g., powdered activated carbon dosing), and other purposes. ELISA has also been considered for compliance monitoring. The purpose of this study was to evaluate the accuracy of common commercial atrazine ELISA tests in a variety of surface waters. Seventeen raw and finished drinking water samples from various water supplies were analyzed using three different commercial ELISA test kits and using gas chromatography/mass spectrometry (GUMS) with solid-phase extraction. Each sample was analyzed in duplicate, as received, and also with 1-mu g/L atrazine spike to test recoveries. The results showed that the commercial ELISA kits provided reproducible results though their accuracy varied between waters. Recoveries in raw and finished waters for the Abraxis (TM), Beacon (TM), and SDI (TM) kits averaged 129, 132, and 113% in raw water, respectively, and 113, 141, and 112% in finished water, respectively. Overall recoveries of a 1 mu g/L spike ranged from 71-222, 69-294, and 58-229% for the three kits, respectively. While most biases observed were positive, negative biases were also observed, which is significant in that the ELISA results underestimated the true atrazine concentrations present.