Complexation of Eu with humic substances studied by time-resolved laser fluorescence spectroscopy and parallel factor analysis

時間分解レーザースペクトルのパラレル因子分析で解析された腐植物質と3価ユウロピウムの錯形成反応

斎藤 拓巳*; Lukman, S.*; 青柳 登   ; 木村 貴海 ; 長崎 晋也*

Saito, Takumi*; Lukman, S.*; Aoyagi, Noboru; Kimura, Takaumi; Nagasaki, Shinya*

Humic substances are heterogeneous and ill-defined organic nanoparticles widely found in soil and aqueous environments. They are known as effective complexants for inorganic and organic contaminants, mediating their migration through geosphere. In this research, we investigated the binding of Eu to various HS by time-resolved laser fluorescence spectroscopy hyphnated with parallel factor analysis. Time-resolved laser fluorescence spectroscopy (TRLFS) is an analytical technique sensitive to physico-chemical forms of a target fluorescent metal ion, which can be further reinforced by combining with a powerful multivariate data analysis, PARARAC. Binding of Eu to HS purchased from the International and Japanese Humic Substances Societies was examined by TRLFS as a function of pH. A series of TRLFS data obtained for a certain HS were processed by PARAFAC to determine the number, spectra, decays and relative concentrations of factors. Each of the factors has some similarity among different HS, suggesting the presence of similar binding environments in different HS. It was further revealed that there were systematic trends between the spectra, decays and concentrations of the factors and the physical and chemical properties of HS. The observed trends will be used to deduce the characteristics of the different binding environments for Eu in HS.