EFFECT OF PHYSICOCHEMICAL HETEROGENEITY OF NATURAL COMPLEXANTS .1. VOLTAMMETRY OF LABILE METAL FULVIC COMPLEXES

A theoretical study of the effect of the physico-chemical heterogeneity of complexants such as fulvic compounds on d.c. polarographic curves is described. These compounds have been strongly implicated in playing a decisive role in trace cation complexation in natural systems. Their main feature is their wide range of complexation energy, which stems from their intrinsic properties: polyfunctionality, polyelectrolytic character and conformational properties. The whole of these complexing properties may be represented by complexation distribution functions. It is shown that, in the formation of labile metal-fulvic complexes and in the absence of adsorption and kinetic effects, it is possible to obtain from a single voltammetric curve important parameters related to metal speciation, namely the average diffusion coefficient of the complexes and the parameters describing the equilibrium complexation distribution functions. © 1990.