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Recent innovations in enantiomer separation by electrochromatography utilizing modified cyclodextrins as stationary phases
Author(s) -
Schurig Volker,
Wistuba Dorothee
Publication year - 1999
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/(sici)1522-2683(19990801)20:12<2313::aid-elps2313>3.0.co;2-f
Subject(s) - capillary electrochromatography , enantiomer , chemistry , chromatography , electrochromatography , cyclodextrin , chiral column chromatography , elution , capillary action , chirality (physics) , enantioselective synthesis , phase (matter) , high performance liquid chromatography , stationary phase , organic chemistry , materials science , catalysis , chiral symmetry breaking , physics , quantum mechanics , nambu–jona lasinio model , composite material , quark
Enantiomer separation by electrochromatography employing modified cyclodextrins as stationary phases is performed in two ways. (i) Polysiloxane‒linked permethylated β‒cyclodextrin (Chirasil‒Dex 1 ) or related selectors are coated and immobilized onto the inner surface of a capillary column. Enantiomer separation is performed in the open tube and the method is referred to as open‒tubular capillary electrochromatography (o‒CEC). (ii) Silica‒linked native β‒cyclodextrin, permethylated β‒cyclodextrin (Chira‒Dex 2 ) or hydroxypropyl‒β‒cyclodextrin are filled into a capillary column and the bed is secured by two frits. Enantiomer separation is performed in a packed column and the method is referred to as packed capillary electrochromatography (p‒CEC). In a unified instrumental approach, method (i) as well as method (ii) can be operated both in the electro‒ and pressure‒driven modes (o‒CEC vs. open‒tubular liquid chromatography (o‒LC) and p‒CEC vs. p‒LC). It is demonstrated that the electro‒driven variant affords higher efficiencies at comparable elution times. Employing a single open‒tubular column coated with Chirasil‒Dex 1 , a unified enantioselective approach can be realized in which the same selectand is separated using all existing chromatographic modes for enantiomers, i.e. , gas chromatography (GC), supercritical fluid chromatography (SFC), o‒LC and o‒CEC. As the chiral selector is utilized as a stationary phase, an additional chiral selector may be added to the mobile phase. In the resulting dual chiral recognition systems, enhancement of enantioselectivity (matched case) or compensation of enantioselectivity (mismatched case) may be observed. The overall enantioselectivity is dependent on the sense of enantioselectivity of the selectors chosen and their influence on the electrophoretic and electroosmotic migration of the enantiomers of a selectand.