Chiral capillary electrophoretic resolution of baclofen, gabaergic ligand, using highly sulfated cyclodextrins

Abstract

Using cyclodextrin-capillary zone electrophoresis (CD-CZE), baseline separation of baclofen, a potent GABA(B) agonist; was achieved. A method for the enantioresolution of this gamma-aminobutyric acid (GABA) and determination of enantiomeric purity was developed using CDs (highly sulfated-CD or highly S-CD) as chiral selectors and capillaries dynamically coated with polyethylene oxide (PEO). Operational parameters, such as the nature and concentration of the chiral selectors, buffer concentration, organic modifiers, and applied voltage, were investigated. The use of charged CDs provides a driving force in the opposite direction of the positively charged baclofen in the running buffer and enantiomeric resolution by inclusion of compounds in the CD cavity. Highly S-beta-CD was found to be the most effective complexing agent, allowing good enantiomeric resolution. The complete resolution was obtained using 25 mM phosphate buffer, pH 2.5, containing 3% w/v highly S-beta-CD at 25 degrees C with aN applied field of 0.40 kV/cm. The apparent association constants of the inclusion complexes were calculated. This optimized method was validated in terms of repeatability and limits of detection (0.13 microg x mL(-1)) and quantification. The migration order was determined.