Determination of metal ion binding parameters for humic substances Part 1.Application of a simple calculation method for extraction of meaningful parameters from reverse pulse polarograms

Extraction of valid metal ion complexation parameters for heterogeneous lig ands from voltammetric data is fraught with difficulties. We apply a straig htforward calculation method to pulse polarograms, which overcomes some of the limitations. Our method takes into account the heterogeneity of complex ants such as fulvic acids through the use of two parameters which are inher ent properties of the substance under study and which allow complexation pa rameters to be calculated for other metal-loading conditions. The results o btained are used to generate theoretical polarograms, by using a numerical simulation model that allows kinetic effects to be taken into account. Appl ication of this methodology to Cu(II)- and Pb(II)-complexation by Suwannee River fulvic acid showed that RPP polarographic waves for both of these met als are affected to some extent by adsorption of the ligand on the working electrode surface. For Cu(II), the complexation parameters were strongly de pendent on the experimental conditions, implying that the overall impact of adsorption is far more significant than for Pb(II). (C) 2000 Elsevier Scie nce S.A. All rights reserved.