Enantioseparation of α‐hydroxy acids by chiral ligand exchange CE with a dual central metal ion system

Abstract

Using two kinds of central metal ions in a background electrolyte, ligand exchange CE was investigated for the simultaneous enantioseparation of dl-malic, dl-tartaric, and dl-isocitric acids. Ligand exchange CE with 100 mM d-quinic acid as a chiral selector ligand and 10 mM Cu(II) ion as a central metal ion could enantioseparate dl-tartaric acid but not dl-malic acid or dl-isocitric acid. A dual central metal ion system containing 0.5 mM Al(III) ion in addition to 10 mM Cu(II) ion in the background electrolyte enabled the simultaneous enantioseparation of the three α-hydroxy acids. These results suggest that the use of a dual central metal ion system can be useful for enantioseparation by ligand exchange CE.

Determination of α‐hydroxy acids and their enantiomers in fruit juices by ligand exchange CE with a dual central metal ion system

“…We previously reported a chiral ligand exchange CE with d ‐quinic acid ligand and Cu(II) and Al(III) ions as a dual central metal ion system for enantioseparation of dl ‐malic, dl ‐tartaric, and dl ‐isocitric acids . The optimum BGE was 20 mM acetate buffer (pH 5.0) containing 100 mM d ‐quinic acid, 10 mM CuSO 4 , and 0.5 mM AlCl 3 .…”

“…An advantage of ligand exchange CE is that it is possible not only to change the chiral selector concentration but also to mix the ligand and the central metal ion at any ratio. Recently, we have used a ligand exchange CE with a dual central metal ion system to simultaneously enantioseparate dl ‐malic, dl ‐tartaric, and dl ‐isocitric acids . In this study, however, citric acid, a major α‐hydroxy acid in fruit juices, could not be analyzed by the above method with Cu(II) and Al(III) ions as a dual central metal ion system.…”

Chiral selectors in CE: Recent development and applications (mid‐2014 to mid‐2016)

“…The use of SDS was crucial for the simultaneous separation of the amino acid enantiomers. Although in other LE‐CE methods reported, a pH value of 5 was required and a slow, irreproducible cathodic EOF and long analysis times (∼15 min) were generated ; in the method reported here, the negatively charged analytes were resolved in less than 8 min. The use of hexadecyltrimethylammonium hydroxide generated a reversed EOF, which, in turn, made the anions to migrate first.…”

Composition and stability constants of copper(II) complexes with succinic acid determined by capillary electrophoresis

“…The copper(II) complexes are also employed in CE for the metal determination [24] and in ligand-exchange CE for the separation of different organic analytes [36][37][38][39][40], including enantiomers [37]. But the CE technique has not been used early for studying the copper(II) complexes with succinic acid ions.…”