title: Dual chiral recognition system involving cyclodextrin derivatives in capillary electrophoresis II. Enhancement of enantioselectivity.
abstract: The enantiomer separation of hexobarbital was investigated by open tubular electrochromatography (OTEC) using the chiral stationary phase (CSP) CHIRASIL-DEX (a permethylated beta-cyclodextrin covalently linked to a dimethylpolysiloxane) and by cyclodextrin-electrokinetic chromatogaphy (CD-EKC) using anionic beta-cyclodextrin-sulfo-n-propyl ether (SPE-beta-CD) and cationic beta-cyclodextrin-2-hydroxy-3-trimethylammoniumpropyl ether chloride (HTAP-beta-CD) added to the running buffer. By employing two chiral selectors, the enantiomer separation of hexobarbital was then studied simultaneously by OTEC with CHIRASIL-DEX and by CD-EKC with either SPE-beta-CD or HTAP-beta-CD in the dual chiral recognition mode. In conjunction with CHIRASIL-DEX, anionic SPE-beta-CD decreased the chiral separation factor alpha due to compensation of enantioselectivity whereas the cationic additive HTAP-beta-CD increased the chiral separation factor alpha due to enhancement of enantioselectivity. It is concluded that CHIRASIL-DEX imparts an opposite enantioselectivity to the enantiomers of hexobarbital as compared to the charged CDs SPE-beta-CD and HTAP-beta-CD. Unusual peak broadening phenomena are observed in the dual chiral recognition system comprised of CHIRASIL-DEX and HTAP-beta-CD. The possible consequences of accidental dual chiral recognition systems caused by wall stacking effects of the mobile phase additives onto the inner surface of the capillary column are discussed.
authors.affiliation: Institut für Organische Chemie, Universität Tübingen, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Jakubetz
authors.forename: M
authors.initials: M
authors.lastname: Juza
authors.forename: V
authors.initials: V
authors.lastname: Schurig
mesh_terms: D000180:Acrylic Resins; D002240:Carbohydrate Sequence; D003505:Cyclodextrins / Q000737:chemistry; D019075:Electrophoresis, Capillary / Q000379:methods*; D006591:Hexobarbital / Q000302:isolation & purification*; D006993:Hypnotics and Sedatives; D008969:Molecular Sequence Data; D015394:Molecular Structure; D011412:Propanolamines / Q000737:chemistry; D012822:Silicon Dioxide; D013451:Sulfonic Acids / Q000737:chemistry; D047392:beta-Cyclodextrins; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D003505:Cyclodextrins; D006591:Hexobarbital; D006993:Hypnotics and Sedatives; D011412:Propanolamines; D012822:Silicon Dioxide; D013451:Sulfonic Acids; D047392:beta-Cyclodextrins; D000099166:Polyacrylamides; C113663:beta-cyclodextrin-2-hydroxy-3-trimethylammoniumpropyl ether chloride; C113664:beta-cyclodextrin-sulfo-n-propyl ether