DETERMINATION OF THE CROSS-REACTIVITIES OF IMMUNOASSAYS - EFFECT OF COMMON CROSS-REACTANTS FOR CHLORPYRIFOS-ETHYL IN WATER MATRICES USING MAGNETIC PARTICLE-BASED ELISA

A novel approach to assess the cross-reactivity of immunoassays in the simultaneous presence of potential cross-reactant analytes was report ed. The magnetic particle-based ELISA for chlorpyrifos-ethyl was used as a model assay in various water matrices (distilled, ground, and est uarine) in the presence of other organophosphorus pesticides commonly applied: chlorpyrifos-methyl, pyridafenthion, diazinon, fenitrothion, azinphos-ethyl, dichlorvos, temephos, and fenthion. The interferences were studied at a fixed concentration of 0.5 mu g/L chlorpyrifos-ethyl and varying concentrations of the common cross-reactants from 0.05 to 1000 mu g/L. The method for determining cross-reactivities gave much lower values (25-50%) as compared to conventional methods. A slight va riation (<3%) on the cross-reactivity values was detected according to the water type used.