Enantiomeric analysis of baclofen analogs by capillary zone electrophoresis, using highly sulfated cyclodextrins: Inclusion ionization constant pKa determination.
Using cyclodextrin-capillary zone electrophoresis (CD-CZE), baseline separation of baclofen phaclofen, saclofen, and hydroxy-saclofen, potent gamma-aminobutyric acid(B) (GABA(B)) agonist or antagonists was achieved. A method for the enantioresolution of those analogs of GABA was developed using anionic cyclodextrins (highly sulfated CD or highly S-CD) as chiral selectors and capillaries dynamically coated with polyethylene oxide (PEO). With charged CDs we observed good resolutions due to the large electrophoretic mobility of these chiral selectors opposite to the mobility of the solutes. The highly S-alpha-CD and S-beta-CD were found to be complementary and the most effective complexing agent, allowing good enantiomeric resolution in short runtimes. The complete resolution was obtained using 25 mM phosphate buffer at pH 2.5 containing 3% w/v of highly S-alpha-CD or S-beta-CD at 25 degrees C with an applied field of 0.30 kV/cm. The apparent binding constants of the inclusion complexes were evaluated and the migration order was determined. A comparison was possible to investigate the importance of the anionic group of the molecules in the separations. The pK(a) values were determined for all four compounds in order to explain relative electrophoretic migration of the solutes.
Vaccher
Marie-Pierre
MP
Laboratoire de Chimie Analytique, Faculté des Sciences Pharmaceutiques et Biologiques, Université de Lille, France. cvaccher@pharma.uni-lille2.fr
Lipka
Emmanuelle
E
Bonte
Jean-Paul
JP
Foulon
Catherine
C
Goossens
Jean-François
JF
Vaccher
Claude
C
D001418:Baclofen / Q000031:analogs & derivatives* / Q000032:analysis*; D002021:Buffers; D003505:Cyclodextrins / Q000737:chemistry*; D019075:Electrophoresis, Capillary; D018755:GABA Agonists / Q000032:analysis*; D058786:GABA-B Receptor Agonists; D006863:Hydrogen-Ion Concentration; D013237:Stereoisomerism; D013451:Sulfonic Acids / Q000737:chemistry
D002021:Buffers; D003505:Cyclodextrins; D018755:GABA Agonists; D058786:GABA-B Receptor Agonists; D013451:Sulfonic Acids; C052329:phaclofen; D001418:Baclofen; C080629:saclofen