Measurement and modeling of the equilibrium behavior of the Tröger's base enantiomers on an amylose-based chiral stationary phase.
The binary isotherms of the two enantiomers of Tröger's base were measured on a system made of pure 2-propanol as the mobile phase and of Chiralpak AD, a chiral stationary phase (CSP) based on amylose tri-(3,5-dimethylphenyl carbamate). The experimental data were acquired using both frontal analysis and the perturbation method. The results obtained are most unusual. The adsorption of the more-retained (-)-enantiomer is not competitive: the amount adsorbed onto the CSP at equilibrium with a constant concentration of the (-)-enantiomer is independent of the concentration of the (+) enantiomer. On the other hand, the adsorption of the less-retained enantiomer is cooperative: the amount of this (+)-enantiomer adsorbed by the CSP at equilibrium with a constant concentration of this enantiomer increases with increasing concentration of the (-)-enantiomer. Such a phenomenon has hardly ever been reported. A model equation is proposed that accounts well for all these isotherm data.
Mihlbachler
K
K
Department of Chemistry, University of Tennessee, Knoxville 37996-1600, USA.
Kaczmarski
K
K
Seidel-Morgenstern
A
A
Guiochon
G
G
D000327:Adsorption; D000688:Amylose / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000379:methods*; D013237:Stereoisomerism
D000688:Amylose