Synthesis of haptens of organophosphorus pesticides and development of enzyme-linked immunosorbent assays for parathion-methyl Original Research Article

A simple synthetic method for haptens of organophosphorus (OP) pesticides with a spacer arm (aminocarboxylic acid) attached at the pesticide thiophosphate group was developed. While the previous synthetic approach for this type of haptens requires seven steps, the present method involves only two steps. Using this method, four haptens of the OP insecticide parathion-methyl were synthesized. Rabbits were immunized with either one of the two haptens coupled to bovine serum albumin for production of polyclonal antibodies. Using the serum with the highest specificity, an antigen-coated ELISA was developed, which showed an IC50 of 6.4 ng/ml with a detection limit of 0.2 ng/ml. An antibody-coated ELISA using an enzyme tracer was also developed, which showed an IC50 of 3.5 ng/ml with a detection limit of 0.3 ng/ml. The antibodies showed negligible cross-reactivity with other OP pesticides tested except with the insecticides parathion and paraoxon only in the antigen-coated ELISA.