Validation of commercially available ELISA microtiter plates for triazines in water samples

Comparative trials were carried out on triazine microtiter plate tests distributed by Millipore, Riedel-de Haen, Transia and CIFEC. Sensitivity and reproducibility were tested with standard solutions of atrazine. Cross-reactivity was studied for hydroxyatrazine, deisopropylatrazine, deethylatrazine, simazine, hydroxysimazine, terbutylazine, hydroxyterbutylazine and deetylterbutylazine. A set of 19 surface-, 16 ground- and 6 lysimetric plate water samples were also analysed. Liquid chromatography with diode array detection or gas chromatography with nitrogen-phosphorus detection were used as validated control techniques for those natural samples. Laboratory assays developed by GEC-Marconi as part of a collaborative European Union research project (BIOPTICAS) have also been assessed. The lowest detectable dose were those of Riedel and Transia tests, 0.003 and 0.014 μg/l, respectively. The other tests also enable the detection of atrazine below 0.1 μg/l. All tests showed inter-assay coefficients of variation (C.V.) below 20%, the Transia, GEC-Marconi and Riedel tests producing the lowest inter-assay C.V.s. The mean intra-assay C.V.s were below 7% for all tests, the most homogeneous results being those of Transia and CIFEC. Except for the GEC-Marconi test which appeared very specific for atrazine, the most interfering triazines were terbutylazine, simazine and deethylatrazine. For the complete set of 41 water samples, the triazine concentrations measured by all the immunoassays and the sum of the triazines determined by gas chromatography-liquid chromatography were correlated at the 0.001 level, while for the water samples collected from lysimetric plates, the correlation coefficients were less significant, except for the Riedel test whose correlation coefficient remained significant at the 0.001 level. The laboratory-based assay from GEC-Marconi, still under development, showed promising characteristics with respect to sensitivity and specificity. The Riedel-de Haen test gave the best overall results.