title: Temperature effects on the enantioselectivity of basic analytes in capillary EKC using sulfated beta-CDs as chiral selectors.
abstract: The thermodynamic processes were investigated to reveal the temperature effects during chiral separation by capillary EKC with reversed polarity mode using sulfated beta-CD (S-beta-CD) as chiral selectors. The temperature effects on enantioselectivities of basic analytes (ephedrine, norephedrine, synephrine, and epinephrine) were investigated in detail over a temperature range of 20-60 degrees C. An increase of the capillary temperature produced the decrease of enantioselectivities for ephedrine and norephedrine, but increase of enantioselectivities for synephrine and epinephrine. The thermodynamic variations showed that the interactions between the basic analytes and chiral selectors were always enthalpy- driven. However, the difference in enthalpy and entropy showed that the enantioseparation was an enthalpy-driven process for ephedrine and norephedrine, but an entropydriven process for synephrine and epinephrine. Just because of the different driving forces, there exist two kinds of temperature effects on enantioselectivities mentioned above.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: Zhen-Lei
authors.initials: ZL
authors.lastname: Peng
authors.forename: Fei
authors.initials: F
authors.lastname: Yi
authors.forename: Baoyuan
authors.initials: B
authors.lastname: Guo
authors.forename: Jin-Ming
authors.initials: JM
authors.lastname: Lin
mesh_terms: D000465:Algorithms; D053801:Capillary Electrochromatography / Q000379:methods*; D005591:Chemical Fractionation; D019075:Electrophoresis, Capillary / Q000379:methods*; D019277:Entropy; D004837:Epinephrine / Q000737:chemistry; D013237:Stereoisomerism; D013431:Sulfates / Q000737:chemistry*; D013578:Synephrine / Q000737:chemistry; D013696:Temperature; D013816:Thermodynamics; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D013431:Sulfates; D047392:beta-Cyclodextrins; D013578:Synephrine; D004837:Epinephrine