Separation of dansylated amino acid enantiomers by chiral ligand‐exchange CE with a zinc(II) L‐arginine complex as the selecting system

Abstract

A facile chiral ligand-exchange capillary electrophoretic method has been explored for the enantioseparation and UV detection of dansyl-amino acids with Zn(II) L-arginine complex as a chiral selecting system. Successful enantioseparation of 17 pairs of amino acid enantiomers has been achieved with a buffer of 100 mM boric acid, 5 mM ammonium acetate, 3 mM ZnSO4 and 6 mM L-Arg at pH 8.0, of which 10 pairs were fully resolved with resolution in between 1.59 and 4.21. This new method was shown to be applicable to the separation of some mixed pairs of amino acids and to the quantitative analysis of some real samples such as rice vinegars, with a linear range between 0.8 and 150 microg/mL, correlation coefficient above 0.99 and recovery in between 90.1 and 112.4%. It was found that amino acids with low resistance side chain(s), low tendency to form intramolecular hydrogen bond or high tendency to form intermolecular hydrogen bonds are more easily enantioseparated than those with extra carboxyl and/or phenyl groups. By the use of the suggested buffer, the running pH should be selected at 7.4-9.0 to compromise the resolution and elution speed.

Investigation of Enantiomeric Separation of Chiral Drugs by CE Using Cu(II)–Clindamycin Complex as a Novel Chiral Selector

“…In order to acquire the optimum clindamycin concentration for the chiral separations of the studied drugs, we tested six different concentrations (5,10,15,20,25, and 30 mM); the molar ratio of copper(II) to clindamycin was kept at 1:2 (pH 9.06).…”

“…The advantages of CE, compared with other chromatographic methods, are that it is a simple, rapid, and practical method for providing high separation efficiency that requires small amounts of samples and reagents. Different types of chiral selectors, including cyclodextrins (CDs) and their derivatives [8][9][10], polysaccharides [11,12], antibiotics [13][14][15][16][17][18], and metal ion complexes [19][20][21][22][23], have been successfully applied as chiral additives in CE for chiral separations.…”

Chiral ligand‐exchange CE assays for separation of amino acid enantiomers and determination of enzyme kinetic constant

“…Cu(II) is the frequently used central ion in CLE-CE [23], but Cu(II) tends to adsorb onto silica capillary wall and has fairly high UV absorption background, thus other metal ions, such as Co(II), Mn(II), Ni(II) and Cd(II), have been tried to replace the Cu(II) [24]. In our previous study, Zn(II)-L-lysine and Zn(II)-L-arginine were used [25][26][27] In this paper, CLE-CE of D,L-aromatic AAs were studied as a first trial and positive results were produced: a complex of Zn(II)-L-Orn was able to separate three pairs of common aromatic AA enantiomers and four pairs labeled AAs. Some mixed D,L-AAs were also successfully resolved.…”

Enantioseparation of Dansylated Amino Acids by Ligand-exchange Capillary Electrophoresis Using L-phenylalaninamide, L-lysine or L-threonine as Chiral Selector

“…14 Schmid and Gübitz succeeded first in directly resolving underivatized AAs using L-Pro and L-Hypro as their Cu(II) complexes added to the electrolyte. 15 Meanwhile a multitude of different chiral selectors for the resolution of AAs and Dns-AAs racemates by LE were introduced by different groups, namely, Cu(II)-L-arginine, 16 Zn(II)-L-arginine, 17 Cu(II)-aspartame, 18,19 Cu(II)-L-alaninamide, 29,30 Cu(II)-L-proline 15,23 and Cu(II)-Lprolinamide 20 . In this research, experiments with the three chiral selectors L-phenylalaninamide, L-lysine and L-threonine were performed under different conditions, to resolve Dns-AAs by LECE.…”