title: 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.
abstract: 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.
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama, Japan.
authors.forename: Sen-Ichi
authors.initials: S
authors.lastname: Aizawa
authors.forename: Shuji
authors.initials: S
authors.lastname: Kodama
mesh_terms: D002413:Cations, Divalent / Q000737:chemistry; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods*; D008024:Ligands; D009532:Nickel / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D011801:Quinic Acid / Q000737:chemistry*; D013237:Stereoisomerism; D013644:Tartrates / Q000032:analysis / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D008024:Ligands; D013644:Tartrates; D011801:Quinic Acid; D003300:Copper; D009532:Nickel; C029768:tartaric acid