Complexation of europium(III) with the zwitterionic form of amino acids studied with ultraviolet-visible and time-resolved laser-induced fluorescence spectroscopy.
The complex formation of europium(III) with the zwitterionic form of amino acids (alanine, phenylalanine, and threonine) has been studied in aqueous solution. Measurements were performed at I = 0.1 M (NaCl/NaClO(4)), room temperature, and trace metal concentrations in the range of pH 2 to 8 using ultraviolet-visible (UV-Vis) and time-resolved laser-induced fluorescence spectroscopy (TRLFS). While complexation leads to a significant luminescence enhancement in the emission spectrum of the metal ion, absorption in the UV-Vis spectrum of the amino acid (AA) decreases. As zwitterionic species (AAH), all three ligands form weak complexes with 1:1 stoichiometry and a general formula of EuAAH(3+) with the metal. The complex stability constants were determined to be log K approximately 1 for all complexes, indicating the negligible contribution of the amino acid side chain to the complex formation reaction.
Heller
Anne
A
Institute of Radiochemistry, Forschungszentrum Dresden-Rossendorf e. V., P.O. Box 510119, Dresden 01314, Germany. a.heller@fzd.de
Rönitz
Olivia
O
Barkleit
Astrid
A
Bernhard
Gert
G
Ackermann
Jörg-Uwe
JU
D000596:Amino Acids / Q000737:chemistry*; D005063:Europium / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013696:Temperature; D013997:Time Factors
D000596:Amino Acids; D007477:Ions; D019216:Metals, Heavy; D005063:Europium