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Mechanism of change in enantiomer migration order of enantioseparation of tartaric acid by ligand exchange capillary electrophoresis with Cu(II) and Ni(II)– D ‐quinic acid systems
Author(s) -
Aizawa SenIchi,
Kodama Shuji
Publication year - 2012
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.201100512
Subject(s) - quinic acid , chemistry , tartaric acid , enantiomer , ligand (biochemistry) , ternary operation , ternary complex , carboxylate , circular dichroism , capillary electrophoresis , stereochemistry , inorganic chemistry , crystallography , citric acid , organic chemistry , chromatography , biochemistry , enzyme , receptor , computer science , programming language
The mechanism of change in the enantiomer migration order (EMO) of tartarate on ligand exchange CE with Cu(II)– and Ni(II)– D ‐quinic acid systems was investigated thoroughly by circular dichroism (CD) spectropolarimetry. The 13 C NMR spectra of solutions containing D ‐quinate (pH 5.0) with Cu(II) or Ni(II) revealed the coordination of carboxylate and hydroxyl groups on D ‐quinate. The D ‐quinic acid concentration dependence of the CD spectra at a fixed Cu(II) concentration at pH 5.0 indicates that the 1:1, 1:2 and 1:3 Cu(II)– D ‐quinate complexes were formed with an increase in the concentration of D ‐quinic acid. The CD spectral behavior revealed that D ‐tartarate is selectively coordinated to the 1:1 complex to give the 1:1:1 Cu(II)– D ‐quinate– D ‐tartarate ternary complex while L ‐tartarate is selectively bound to the 1:2 and 1:3 complexes to form the 1:2:1 ternary complex. In the Ni(II)– D ‐quinic acid system, it became apparent that the 1:2 Ni(II)– D ‐quinate complex is mainly formed in the wide range of D ‐quinic acid concentration at pH 5.0 and D ‐tartarate is selectively coordinated to the 1:2 complex to form the 1:2:1 ternary complex. The change in EMO of tartarate on ligand exchange CE was explainable by the change in coordination selectivity for D ‐ and L ‐tartarates in the Cu(II)– and Ni(II)– D ‐quinic acid systems depending on the compositions of the complexes formed in BGE.