Cyclic voltammetry was used to determine the stability constants for the complexation of cadmium and zinc ions with hydroxyl-terminated polyamidoamine generation 2 dendrimers with an ethylenediamine core (PAMAM G2-OH) at a mercury ultramicroelectrode. Cadmium and zinc ions were found to form poly-metal complexes through the interactions with interior amino groups rather than hydroxyl groups and the maximum number of metal ions per dendrimer or stoichiometry was 4. Complexation is accompanied by a significant decrease in the limiting current and by measuring the changes in the magnitude of cathodic current with the analytical dendrimer:metal ion ratio and fitting the resulting curves. the four cumulative consecutive complexation constants were determined: 1.3 x 10(5) M-1, 1.6 x 10(9) M-2, 3.3 x 10(12) M-3 and 4.6 x 10(14) M-4 for Cd2+ and 1.0 x 10(6) M-1, 1.6 x 10(9) M-2, 4.6 x 10(14) M-3 and 2.6 x 10(17) M-4 for Zn2+. The stronger interaction of' zinc ions with PAMAM G2-OH compared to cadmium was accompanied with a sharper decrease of the cathodic current with the addition of' dendrimer and a larger half-wave potential shift than cadmium. This was rationalized by evaluating the changes of the diffusion coefficients for these two different systems by electrochemical means. (c) 2008 Elsevier B.V. All rights reserved.