GLUCURONATE COMPLEXES WITH MG2- A POSSIBLE CHEMICAL SPECIATION MODEL FOR BIOCHEMICAL UNDERSTANDING(, CA2+, ZN2+ AND CD2+ IN AQUEOUS CHLORIDE SOLUTION )

Protonation constants and Na+-, Mg2+-, Ca2+-, Zn2+- and Cd2+-D-Glucuro nate complex formation constants have been determined potentiometrical ly in different ionic strength conditions. Glucuronate forms a very we ak complex species with Na+ (K similar to 1 dm(3) mol(-1)), and weak s pecies with Mg2+ and Ca2+ (K similar to 10 dm(3) mol(-1)). When glucur onate interacts with Zn2+ and Cd2+, two species, M(gluc) and M(gluc)(2 ) (gluc = glucuronate) having a stability intermediate between that of mono and dicarboxylate complexes, are formed. This can be due to the involvement of the ethereal oxygen in the coordination. Medium effects are considered in the light of speciation problems.