Effects of partial/asymmetrical filling of micelles and chiral selectors on capillary electrophoresis enantiomeric separation: Generation of a gradient

Abstract

The effect of several experimental parameters on enantiomeric separations in micellar capillary electrophoresis (MCE) was studied. A model separation system was tested. It was composed of an acidic phosphate buffer with sodium dodecyl sulfate (SDS) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as the chiral selector. A substituted angelicin was used as a chiral analyte. Changes in the concentration of SDS micelles/SDS monomers in the presence of HP-beta-CD and their impact on the enantioselective separation were investigated. Variation of the composition of electrolytes in the individual compartments of the separation system (inlet vial, capillary, and outlet vial) affected both the migration times and the resolution of the enantiomers. Current vs. time dependencies also were monitored during the separations. A mathematical model of electromigration in micellar systems with chiral selector present was proposed and a computer simulation was used to explain the observed phenomena and to confirm the generation of a CD/SDS-micelle concentration gradient under certain experimental conditions. This is the reported first attempt of a computer simulation of the complex, dynamic chiral environment of the CD-SDS-MCE system.

Simultaneous contactless conductivity detection and UV detection for the study of separation of tamsulosin enantiomers in discontinuous electrolyte systems by CE

“…Tesařová et al [18] published the separation of enantiomers of a coumarin derivative by hydroxypropyl-b-CD-modified MEKC. SDS was used for the micelle formation.…”

“…It was noted that the variation of experimental arrangements affected both the migration times and the resolution of the enantiomers. Also, a mathematical model was proposed for the confirmation of the observed data [18].…”

Dynamic computer simulations of electrophoresis: A versatile research and teaching tool

“…Because dissociationÀassociation reactions are fast compared with the mass transport [39,40], ion concentrations are constrained by a coupled set of mass action relations, namely the dissociation of water and the dissociationÀassociation equilibria of the components. Special versions of SIMUL [72][73][74] and GENTRANS [75] also feature secondary equilibria between analytes and buffer additives, which allow the performance of EKC simulations. Other codes included equilibria of solutes with paper surface [30,31] or channel walls [76][77][78], and one code dealt with the modeling of electrophoretic solute transport between two liquid phases [79].…”

“…This was used to estimate the stability constant of 4-hydroxyazobenzenesulfonic acid with bcyclodextrin and there was excellent agreement with spectroscopic values found in the literature. The next and most comprehensive work in this field was presented by Tesařová et al [73]. Equations were introduced into a new version of SIMUL, SIMULMIC, to account for the additional equilibria that occur in the separation of a neutral analyte in the presence of a neutral cyclodextrin and charged surfactant (SDS), including the monomer-micelle equilibrium of the surfactant.…”

High‐resolution computer simulations of EKC

“…This was used to estimate the stability constant of 4-hydroxyazobenzenesulphonic acid with b-cyclodextrin and there was excellent agreement with spectroscopic values found in the literature. The next and most comprehensive work in this field was presented by Tesařová et al in 2004 [52]. Equations were introduced into a new version of SIMUL to account for the additional equilibria that occur in the separation of a neutral analyte in the presence of a neutral cyclodextrin and charged surfactant (SDS), including the monomer-micelle equilibrium of the surfactant.…”