2-(2-Mercapto-5-methyl-1,3,2-dioxaphosphorinan-5-yl,2-sulphide) methoxyacetic acid has been synthesized and used to prepare an azinphos hapten and protein conjugates. Monoclonal antibodies of high affinity against the pesticide azinphos-methyl were prepared from mice immunized with the hapten-ovalbumin conjugate. The best monoclonal antibody could be used in an indirect enzyme-linked immunosorbent assay (ELISA) to quantify azinphos methyl at concentrations from 50 pg ml(-1) to 2 ng ml(-1) (2.5-100 pg/assay). The corresponding limit of detection of the pesticide was less than 40 pg ml(-1). Only the closely related pesticide azinphos-ethyl showed any appreciable cross-reactivity in this assay.
