Vesicles as pseudostationary phase for enantiomer separation by capillary electrophoresis.

A vesicle-forming single-tailed amino acid derivatized surfactant, sodium N-(4-n-dodecyloxybenzoyl)-L-valinate (SDLV) has been used as a chiral selector in micellar electrokinetic chromatography to study the molecular recognition of sterically hindered atropisomeric compounds (+/-)binaphthol, (+/-)binaphthyl diamine, (+/-)binaphthol phosphate, Tröger's base and the chiral compound benzoin (BZN). The aggregation behavior and microstructure of the surfactant were studied in separation buffer. The amphiphile was found to form bilayer vesicles in dilute aqueous solutions. The chromatographic separation of enantiomers by use of large liposome-like vesicles spontaneously formed by the amphiphile was explored. The separations were optimized with respect to voltage, pH, and surfactant and buffer concentrations. The resolutions obtained for the above mentioned racemates by use of SDLV vesicles as chiral selectors are higher compared to those reported for other chiral surfactant monomers. The results have been discussed in light of the aggregation behavior of the amphiphile in buffered aqueous solutions.