Novel Concepts for the Immunological Detection of Bound Residues

Abstract

Immunoassays could be applied successfully to the determination of bound residues in soil and other complex matrices. Nevertheless, there was some doubt whether these assays could be regarded as quantitative and selective. We present some results, which imply that several approaches are quite promising. One approach is based on a non-competitive saturation immunoassay, which evens out the different cross-reactivities of the bound species. This may lead to a true molar sum value, which is not an equivalent concentration. For competitive assays, a method for the determination of the affinity constant(s) of the bound species is discussed. This would enable a correction for the cross-reactivity. The selectivity problem could be diminished very much, too. The application of special blocking reagents and the use of inhibition tests essentially solved the problem of non-specific binding (NSB). In addition, it could be proven experimentally that adsorbed analytes do not disturb the non-competitive assays, which have been suspected to be highly selective for covalently bound residues.

Key Words:

• Immunoassays
• bound residues
• non-extractable residues
• cross-reactivity