Immunoassay for Simazine and Atrazine with Low Cross-Reactivity for Propazine

An antibody for simazine and atrazine has been developed that exhibits low cross-reactivity to propazine relative to most atrazine antibodies heretofore evaluated. The cross-reactivities obtained in an enzyme-linked immunosorbent assay were 100 ± 4% for simazine, 76 ± 9% for atrazine, and 12.6 ± 1.3% for propazine. This was achieved by immunizing rabbits with the hapten 6-[[[4-chloro-6-(methylamino)]-1,3,5-triazin-2-yl]amino]hexanoic acid coupled to keyhole limpet hemocyanin. The influence of tracer hapten structure on the assay sensitivity was investigated in two competitive formats. The performance of the assay with respect to pH differences and ionic strength was also examined. The lowest IC₅₀ values achieved for simazine were in the 0.1 μg/L range, with the limit of quantitation being 50 ng/L. Spike-recovery studies in tap and ground water as well as analysis of crude ground water samples show the usefulness of this sensitive antibody for simazine detection.