Synthesis of haptens and conjugates for an enzyme immunoassay for analysis of the herbicide bromacilt

A competitive enzyme-linked immunosorbent assay (ELISA) was developed for quantitative detection of bromacil. Two haptens were synthesized, the handles having been attached at the N-1 and 6-methyl groups of the target molecule; both carboxylic acids were coupled to several proteins to obtain two sets of conjugates and then polyclonal antibodies. The standard curve based on the heterologous system with the antibody raised against immunizing antigen of the latter hapten conjugated to KLH and the coating antigen prepared from the former hapten and BSA was nearly linear at around the 0.25 ppb level, which is promising for the environmental monitoring of bromacil. There was only moderate handle recognition observed. Cross-reactivities for terbacil, a related herbicide, for metabolites of bromacil, and for the major metabolite of terbacil were less than 4%.