Determination of Association Constants in Cyclodextrin or Vancomycin-Modified Micellar Capillary Electrophoresis


The estimation of association constants of chiral analytes to chiral selectors is often useful in determining the nature and extent of interactions that exist between them. These determinations also provide insight into the mechanisms that are involved in the enantiorecognition of these analytes. Simple models have been developed previously to estimate association constants of analytes binding through a 1:1 stoichiometry with a ligand. These models have also been extrapolated to explain the binding behavior of analytes in systems containing two ligands. In the present study, the binding behavior of some chiral analytes was studied in micellar capillary electrophoresis (CE) systems modified with hydroxypropyl-β-cyclodextrin (HPBCD) or vancomycin as the chiral selectors. The pseudophase or three phase model was used as the basis for the determination of the absolute binding constants of the solutes to the selector and to the micellar phases. However, these systems are complicated due to the interactions that exist not only between the analyte and the chiral selector/micellar phase-but also between the ligands themselves. In the case of the hydroxypropyl-β-cyclodextrin/sodium dodecyl sulfate (SDS) system, the SDS monomers are included in the cyclodextrin cavity. Similarly, in the vancomycin/SDS system, vancomycin partitions itself into micelles. The limitations associated with the use of ideal mathematical models in these complex systems, are also discussed.




National Institutes of Health, Grant BMT 2RO 1 GM36292-05A2

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Article - Journal

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Publication Date

01 Jan 1997