Complexation of Europium(III) with the Zwitterionic Form of Amino Acids Studied with Ultraviolet–Visible and Time-Resolved Laser-Induced Fluorescence Spectroscopy

摘要

The complex formation of europium(III) with the zwitterionic form ofnamino acids (alanine, phenylalanine, and threonine) has been studied innaqueous solution. Measurements were performed at I ¼ 0.1 M (NaClNaClO4), room temperature, and trace metal concentrations in the rangenof pH 2 to 8 using ultraviolet–visible (UV-Vis) and time-resolved laser-ninduced fluorescence spectroscopy (TRLFS). While complexation leads tona significant luminescence enhancement in the emission spectrum of thenmetal ion, absorption in the UV-Vis spectrum of the amino acid (AA)ndecreases. As zwitterionic species (AAH), all three ligands form weakncomplexes with 1 : 1 stoichiometry and a general formula of EuAAH3þnwith the metal. The complex stability constants were determined to be lognK ; 1 for all complexes, indicating the negligible contribution of thenamino acid side chain to the complex formation reaction.