title: High-Performance Liquid Chromatographic Enantioseparation of Cyclic β-Amino Acids on Zwitterionic Chiral Stationary Phases Based on Cinchona Alkaloids.
abstract: Stereoselective high-performance liquid chromatographic separations of eight sterically constrained cyclic β-amino acid enantiomer pairs were carried out using the newly developed Cinchona alkaloid-based zwitterionic chiral stationary phases Chiralpak ZWIX(+) and ZWIX(-). The effects of the mobile phase composition, the nature and concentrations of the acid and base additives, the counterions and temperature on the separations were investigated. The changes in standard enthalpy, Δ(ΔH°), entropy, Δ(ΔS°), and free energy, Δ(ΔG°), were calculated from the linear van't Hoff plots derived from the ln α vs. 1/T curves in the studied temperature range (10-50°C). The values of the thermodynamic parameters depended on the nature of the selectors and the structures of the analytes. Unusual temperature behavior was observed on the ZWIX(-) column: decreased retention times were accompanied by increased separation factors with increasing temperature. On the ZWIX(+) column only enthalpically, whereas on the ZWIX(-) column both enthalpically and entropically driven separations were observed. The elution sequence was determined in all cases and was observed to be the opposite on ZWIX(+) and on ZWIX(-).
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary.
authors.forename: István
authors.initials: I
authors.lastname: Ilisz
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary.|Institute of Pharmaceutical Chemistry, University of Szeged, Szeged, Hungary.
authors.forename: Zsanett
authors.initials: Z
authors.lastname: Gecse
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary.|Institute of Pharmaceutical Chemistry, University of Szeged, Szeged, Hungary.
authors.forename: Gyula
authors.initials: G
authors.lastname: Lajkó
authors.affiliation: Institute of Pharmaceutical Chemistry, University of Szeged, Szeged, Hungary.
authors.forename: Enikõ
authors.initials: E
authors.lastname: Forró
authors.affiliation: Institute of Pharmaceutical Chemistry, University of Szeged, Szeged, Hungary.
authors.forename: Ferenc
authors.initials: F
authors.lastname: Fülöp
authors.affiliation: Department of Analytical Chemistry, University of Vienna, Vienna, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lindner
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary.
authors.forename: Antal
authors.initials: A
authors.lastname: Péter
mesh_terms: D000598:Amino Acids, Cyclic / Q000737:chemistry* / Q000302:isolation & purification*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D002930:Cinchona Alkaloids / Q000737:chemistry*; D013237:Stereoisomerism; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000598:Amino Acids, Cyclic; D002930:Cinchona Alkaloids
keywords: Cinchona alkaloid-based chiral stationary phases; HPLC; cyclic β-amino acids; enantiomer separation