beta-Amino alcohol selectors for enantioselective separation of amino acids by ligand-exchange capillary zone electrophoresis in a low molecular weight organogel

摘要

A new family of copper ligand-exchange selectors, l- or D-P-amino alcohols, is employed for the chiral separation of D,L-dansyl-amino adds, unmodified amino add racemates, phenylalanine and tryptophan, and P-blocker L,D-propranolol by SDS-micellar electro-kinetic chromatography and by electrophoretic chromatography in a low molecular weight organogel (LMOG)-filled capillary. The LMOG comprised a self-assembled fibrillar gel of trans-(l S,2S)-l,2-bis-(dodecylamido) cydohexane in memanol. The di-L-valinol-copper complex exhibited the best performance on LMOG-CE compared with all other P-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 seledors that could be used only under addic 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-fffled capillaries.