Immunoassay Analysis and Gas Chromatography Confirmation of Atrazine Residues in Water Samples from a Field Study Conducted in the State of Wisconsin

In 1990 Ciba Crop Protection entered into a cooperative study with the State of Wisconsin Department of Agriculture Trade and Consumer Protection and Department of Natural Resources. The objective of the study was to assess the level of atrazine in Wisconsin groundwater by immunoassay techniques and confirm detections of regulatory significance by gas chromatography. The study was conducted in two phases. In phase I, 2177 rural well water samples were screened at an immunoassay response level equivalent to 0.10 ppb or greater of atrazine. In phase II all wells that produced an immunoassay response equivalent to 0.35 ppb or greater were resampled and assayed by immunoassay and gas chromatography with mass selective (GC/MS) and thermionic specific detection (nitrogen mode) (GC/TSD). Immunoassay results were shown to correlate highly with results obtained by GC/MS (r = 0.95) and GC/TSD (r = 0.95). Immunoassay analyses conducted in Ciba and Wisconsin laboratories also correlated well (r = 0.93)