Enzyme-linked immunosorbent assay for the organophosphorus insecticide fenthion. Influence of hapten structure.

Novel procedures for fenthion hapten synthesis are described following three different strategies. The first one attaches the spacer arm to the oxygen atom of the aromatic fenthion ring. The second one binds it through the thiophosphate moiety and the third strategy consists on the attachment of the spacer arm to the sulfur atom of the molecule. A total of nine fenthion haptens have been synthesized and used for immunoreagent production (protein conjugates and polyclonal antibodies). The developed conjugate-coated format ELISA exhibited a detection limit of 0.03 ng/ml, an IC50 of 0.05 ng/ml and a dynamic range between 0.03 and 1 ng/ml. There was little or no cross-reactivity to similar tested compounds. The ELISA was used to determine fenthion residues in white wine samples without any purification or preconcentration steps. Recoveries ranged between 81% and 113%.