Campus Units

Chemistry

Document Type

Article

Publication Version

Published Version

Publication Date

12-5-2005

Journal or Book Title

Analytical Chemistry

Volume

78

Issue

1

First Page

113

Last Page

119

DOI

10.1021/ac051289b

Abstract

The theory and use of the “three-phase” model in enantioselective gas−liquid chromatography utilizing a methylated cyclodextrin/polysiloxane stationary phase is presented for the first time. Equations are derived that account for all three partition equilibria in the system, including partitioning between the gas mobile phase and both stationary-phase components and the analyte equilibrium between the polysiloxane and cyclodextrin pseudophase. The separation of the retention contributions from the achiral and chiral parts of the stationary phase can be easily accomplished. Also, it allows the direct examination of the two contributions to enantioselctivity, i.e., that which occurs completely in the liquid stationary phase versus the direct transfer of the chiral analyte in the gas phase to the dissolved chiral selector. Six compounds were studied to verify the model:  1-phenylethanol, α-ionone, 3-methyl-1-indanone, o-(chloromethyl)phenyl sulfoxide, o-(bromomethyl)phenyl sulfoxide, and ethyl p-tolylsulfonate. Generally, the cyclodextrin component of the stationary phase contributes to retention more than the bulk liquid polysiloxane. This may be an important requirement for effective GC chiral stationary phases. In addition, the roles of enthalpy and entropy toward enantiorecognition by this stationary phase were examined. While enantiomeric differences in both enthalpy and entropy provide chiral discrimination, the contribution of entropy appears to be more significant in this regard. The three-phase model may be applied to any gas−liquid chromatography stationary phase involving a pseudophase.

Comments

Reprinted (adapted) with permission from Analytical Chemistry 78 (2006): 113, doi:10.1021/ac051289b. Copyright 2006 American Chemical Society.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

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