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

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.