title: β-Amino alcohol selectors for enantioselective separation of amino acids by ligand-exchange capillary zone electrophoresis in a low molecular weight organogel.
abstract: 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-(1S,2S)-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.
authors.affiliation: The Chemistry Institute, Casali Institute of Applied Chemistry, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Dan
authors.initials: D
authors.lastname: Rizkov
authors.forename: Shaul
authors.initials: S
authors.lastname: Mizrahi
authors.forename: Shmuel
authors.initials: S
authors.lastname: Cohen
authors.forename: Ovadia
authors.initials: O
authors.lastname: Lev
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D000596:Amino Acids / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D003510:Cyclohexanes / Q000737:chemistry*; D003619:Dansyl Compounds / Q000737:chemistry*; D053841:Electroosmosis; D019075:Electrophoresis, Capillary / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D015203:Reproducibility of Results; D013237:Stereoisomerism
chemical_list: D000438:Alcohols; D000596:Amino Acids; D003510:Cyclohexanes; D003619:Dansyl Compounds; D003300:Copper