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β‐Amino alcohol selectors for enantioselective separation of amino acids by ligand‐exchange capillary zone electrophoresis in a low molecular weight organogel
Author(s) -
Rizkov Dan,
Mizrahi Shaul,
Cohen Shmuel,
Lev Ovadia
Publication year - 2010
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.201000328
Subject(s) - chemistry , copper , micellar electrokinetic chromatography , amino acid , chromatography , ligand (biochemistry) , capillary electrophoresis , chiral ligand , cyclohexane , enantioselective synthesis , valine , organic chemistry , catalysis , biochemistry , receptor
A new family of copper ligand‐exchange selectors, L ‐ or D ‐β‐amino alcohols, is employed for the chiral separation of D , L ‐dansyl‐amino acids, unmodified amino acid racemates, phenylalanine and tryptophan, and β‐blocker L , D ‐propranolol by SDS–micellar electrokinetic chromatography and by electrophoretic chromatography in a low molecular weight organogel (LMOG)‐filled capillary. The LMOG comprised a self‐assembled fibrillar gel of trans ‐(1 S ,2 S )‐1,2‐bis‐(dodecylamido) cyclohexane in methanol. The di‐ L ‐valinol–copper complex exhibited the best performance on LMOG–CE compared with all other β‐amino alcohol–copper selectors. The dependence of chiral resolution on the pH*, the ratio between the copper and the L ‐valinol ligand and the concentration of added selector complex in the run buffer were investigated revealing a marked difference between the activity of the copper–valinol and the previously studied copper–valine selector. The optimal separation conditions were achieved using a 2:1 valinol/copper ratio, in accordance with the 2:1 structure of the complex, which was proven by single crystal and powder X‐ray diffractions and by elemental analysis. Unlike the copper–valine selectors that could be used only under acidic conditions (pH* 3.5), the copper–valinol selectors could be used under near‐neutral conditions and even at pH* 9.1. A comparison between SDS–micellar electrokinetic chromatography and LMOG–CE under otherwise identical conditions revealed a significant superior separation on the LMOG‐filled capillaries.