title: Two-chiral component microemulsion EKC - chiral surfactant and chiral oil. Part 2: diethyl tartrate.
abstract: In this second study on dual-chirality microemulsions containing a chiral surfactant and a chiral oil, a less hydrophobic and lower interfacial tension chiral oil, diethyl tartrate, is employed (Part 1, Foley, J. P. et al.., Electrophoresis, DOI: 10.1002/elps.200600551). Six stereochemical combinations of dodecoxycarbonylvaline (DDCV: R, S, or racemic, 2.00% w/v), racemic 2-hexanol (1.65% v/v), and diethyl tartrate (D, L, or racemic, 0.88% v/v) were examined as pseudostationary phases (PSPs) for the enantioseparation of six chiral pharmaceutical compounds: pseudoephedrine, ephedrine, N-methyl ephedrine, metoprolol, synephrine, and atenolol. Average efficiencies increased with the addition of a chiral oil to R-DDCV PSP formulations. Modest improvements in resolution and enantioselectivity (alpha(enant)) were achieved with two-chiral-component systems over the one-chiral-component microemulsion. Slight enantioselective synergies were confirmed using a thermodynamic model. Results obtained in this study are compared to those obtained in Part 1 as well as those obtained with chiral MEEKC using an achiral, low-interfacial-tension oil (ethyl acetate). Dual-chirality microemulsions with the more hydrophobic oil dibutyl tartrate yielded, relative to diethyl tartrate, higher efficiencies (100,000-134,000 vs. 80,800-94,300), but lower resolution (1.64-1.91 vs. 2.08-2.21) due to lower enantioselectivities (1.060-1.067 vs. 1.078-1.081). Atenolol enantiomers could not be separated with the dibutyl tartrate-based microemulsions but were partially resolved using diethyl tartrate microemulsions. A comparable single-chirality microemulsion based on the achiral oil ethyl acetate yielded, relative to diethyl tartrate, lower efficiency (78 300 vs. 91 600), higher resolution (1.99 vs. 1.83), and similar enantioselectivities.
authors.affiliation: Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Kahle
authors.forename: Joe P
authors.initials: JP
authors.lastname: Foley
mesh_terms: D053801:Capillary Electrochromatography; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D004655:Emulsions / Q000737:chemistry*; D009821:Oils; D013237:Stereoisomerism; D013501:Surface-Active Agents; D013644:Tartrates
chemical_list: D004655:Emulsions; D009821:Oils; D013501:Surface-Active Agents; D013644:Tartrates; C064501:diethyl tartrate