Review of aqueous chiral electrokinetic chromatography (EKC) with an emphasis on chiral microemulsion EKC

Abstract

Review of aqueous chiral electrokinetic chromatography (EKC) with an emphasis on chiral microemulsion EKCThe separation of enantiomers using electrokinetic chromatography (EKC) with chiral microemulsions is comprehensively reviewed through December 1, 2006. Aqueous chiral EKC separations based on other pseudostationary phases such as micelles and vesicles or on other chiral selectors such as CDs, crown ethers, glycopeptides, ligand exchange moeities are also reviewed from both mechanistic and applications perspective for the period of

Influence of microemulsion chirality on chromatographic figures of merit in EKC: Results with novel three‐chiral‐component microemulsions and comparison with one‐ and two‐chiral‐component microemulsions

“…In order to delineate the involvement of individual chiral microemulsion components in the overall free energy difference, single-chirality formulations of RXX for the chiral surfactant, XSX for the chiral cosurfactant, and XXR for the chiral oil were previously tested. In the previously completed studies, it was found that XSX [29] and XXR [31] did not give any discernable enantioselectivity, thereby precluding contributions from the cosurfactant or oil. The one-chiralcomponent microemulsion SXX was not analyzed because it has the opposite stereochemistry from RXX and as such should differ only in elution order [40].…”

“…In cases where Eq. (10) does not hold, the reason is postulated to be a synergistic interaction between two or more different chiral components of the microemulsion [29][30][31]. The nature of the synergistic effects, beneficial (higher than expected enantioselectivity) or detrimental (lower than expected enantioselectivity), is defined in Eqs.…”

“…Table 1. b) Previously reported [31]. c) Results averaged over triple-chirality microemulsions only.…”

“…7)) [29][30][31]. In the absence of any cooperativity between chiral microemulsion components, the difference in the free energy of transfer for a given pair of enantiomers from the mobile phase to the triple-chirality microemulsion should be the sum of the differences in the free energies of transfer from the corresponding single-chirality microemulsions: nnG7 triple-chirality = nnG7 chiral surfactant 1 DDG7 chiral cosurfactant 1 DDG7 chiral oil (10) Each term in Eq.…”

“…Enantioselective synergies were discovered with dualchirality systems, and the combination of S-DDCV and S-2-hexanol provided higher efficiencies and resolution than R-DDCV and S-2-hexanol. Next, we investigated two-chiralcomponent microemulsions formed from a chiral surfactant (R-or S-DDCV), an achiral cosurfactant (racemic 2-hexanol), and a chiral oil (dibutyl tartrate [30] or diethyl tartrate [31]). Dibutyl tartrate containing systems were shown to have higher efficiencies but lower enantioselectivities and resolution.…”