Production of the class-specific antibody and development of direct competitive ELISA for multi-residue detection of organophosphorus pesticides

Based on the common structure of organophosphorus pesticides, O,O-dimethylphosphorothioate, two haptens were synthesised with different spacer arms. The class-specific polyclonal antisera were prepared from the conjugates of haptens and keyhole limpet hemocyanin. Under optimum conditions, a homologous direct competitive enzyme-linked immunosorbent assay (ELISA) method was developed for multi-residue detection of 23 organophosphate pesticides. The most sensitive IC₅₀ values of the multi-residue analysis were estimated as 0.25, 0.65 and 0.80 mg L⁻¹ for methyl parathion (PM), fenitrothion and fenthion, respectively. Furthermore, when the developed ELISA was applied to detection of PM in water samples, adequate spike recoveries in the range from 70.3 to 131% were obtained. It provided a useful multi-residue determination method of organophophorus pesticides.