Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The binding of Pb²⁺ and Cu²⁺ ions to starch and amylose 2,3-dicarboxy derivatives of degrees of oxidation DO = 0.09-0.74 was investigated. The interaction of the metal cations with the carboxy groups of the derivatives was evaluated in terms of the counter-ion activity, determined with ion specific electrodes. The binding is very strong; at DO ≥ 0.34, lead ions are bound quantitatively ( degree of association β = 0.999), copper ions are also bound to a great extent (β = 0.94-0.97). The complexation of copper with the ligands at ionic strength I = 0.15 mol 1^-1 was treated in terms of multiple equilibria theory. Different complexes were found in dependence on the concentration ratios of the reactants; at a high excess of COO^- groups with respect to Cu²⁺ ions, the latter are strongly bound and the number of COO^- groups binding a Cu²⁺ cation is greater than 2, whereas at a sufficiently high concentration of Cu²⁺ ions the number of COO^- groups binding a Cu²⁺ cation approaches the stoichiometric value of 2.