MULTIANALYTE EFFECT IN THE DETERMINATION OF CROSS-REACTIVITIES OF PESTICIDE IMMUNOASSAYS IN WATER MATRICES

An extension of Abraham's method to calculate cross-reactivity (CR) is presented, Over a wide concentration range the response curves of a c ross-reactant were compared with those of a standard applied to four i mmunoassay commercial kits (benomyl/carbendazim, chlorothalonil, metol achlor and parathion-ethyl). Various doses of cross-reactants (0-1000 mu g/l) were tested in the presence of various doses of the standard ( 0-100 mu g/l). The results showed that the percentage of the cross-rea ctivity (%CR) decreased as a function of the concentration of cross-re actant present in the water and high %CR values were found in comparis on with those reported in commercial kits. This indicates a better sen sitivity for many analytes as compared to values actually reported in the ELISA (Enzyme-Linked ImmunoSorbent Assay) kits. Applications of th e CR studies are also presented that should help in the acceptance or rejection of a concentration range of cross-reactants in a real sample . When determining the CR in estuarine waters, the matrix effect of es tuarine water underestimated the true extent of cross-reactivity of th e standard, making it necessary to calculate for cross-reactivity to c ompensate for matrix effect.