Standardization for trace metal ion speciation by the electrochemical

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To establish the procedure of the standardization for trace metal ion speciation, fundamental data, such as complexing capacity(CC) and the conditional stability constants(K'), for the interaction of metal ion (copper and nickel) and humas(humic(HA) and fulvic acids(FA)) were collected. HA and FA were prepared as standard materials by The Japan Society for Humic Substances. CC and K' were estimated from metal ion titration by adsorptive stripping voltammetry. Quinoline-8-ol(OX) and dimethylglyoxime(DMG) were used as complexing ligands for copper and nickel, respectively. As the increase of the concentration of OX and DMG, CuCC and NiCC for HA and FA were decreased while K's were increased. This indicates the presence of various coordination sites having different coordination ability, because HA and FA are the mixture of organic compounds having various functional groups and large molecular weights. The relative values for CuCC(HA), NiCC(HA), CuCC(FA) and NiCC(FA) were ca. 450, 30, 30 … More and 1, respectively. To explain these results based on chemical equilibria, three coordination groups, having different number of sites(that is,CC) and K', were assumed. And then, the simulated metal ion titration curve were analyzed by the normal procedure for obtaining CC and K' based on the assumption that one metal ion reacts with one coordination site. This calculation was repeated for different initial CC and K' for assumed coordination sites till the calculated CC and K' were within the range of observed values. For the interactions of Cu-HA, Ni-HA, Cu-FA, good agreement was obtained between observed and calculated values. This enabled us to discuss about the distribution of coordination sites in HA and FA. Additional projects for speciation were also carried out on popularization of the concept of speciation, contamination-free pre-treatment of water samples by UV irradiation with high output low-pressure mercury lamp, electrochemical ultra trace analysis using catalytic effect, synthesis of multidentate ligands to specaiate lanthanide ions and their application to solvent extraction, and production of big wheel mixed-valence compounds to speciate giant molecules. Novel results were also obtained for these projects. Less