Even though polysaccharide based chiral stationary phases are used widely in pharmaceutical industry for chiral drug separations, the chiral recognition mechanisms of these phases are not yet elucidated. Recently, we have studied these biopolymers in dry state, and also upon interactions with solvents and simple solutes in detail [1-3]. In this study, the adsorption of a chiral solute on the polysaccharide based chiral stationary phases are studied in detail using HPLC, attenuated total reflection infrared spectroscopy (ATR-IR), X-ray diffraction (XRD), and molecular modeling. The capacity factors and selectivities of enantiomers of norephedrine vary significantly with different adsorbents and solvents. The changes observed in the wavenumbers and the intensities of amide I and amide II bands of these polymers in the ATR-IR spectra upon adsorption of each of the enantiomer are stereo-specific and correlate strongly with the selectivities in HPLC. The IR wavenumbers, and the H-bonding interaction energies of the polymer side chains with each enantiomer in different configurations predicted using the DFT/B3LYP/6-311+g(d,p) level of theory are in agreement with the capacity factors observed in HPLC. The changes in the polymer crystallinity upon absorption of each enantiomer are characterized with XRD. We conclude that the H-bonding states of the polymer change significantly upon adsorption of each enantiomer and usually result in an increase in the polymer crystallinity. These results have implications in understanding the fundamental molecular recognition mechanisms of these polymers. The results should generate general guidelines for selecting solvents, and sorbents, to optimize retention times, selectivities, productivity, and solvent consumption in chiral chromatography for both analytical separation applications and large-scale production of single enantiomers.

1. R. B. Kasat, Y. Zvinevich, H. W. Hillhouse, K. T. Thomson, N.-H. Linda Wang, and E. I. Franses, Journal of Physical Chemistry B, 110, 2006, 14114-14122.

2. R. B. Kasat, C. Y. Chin, K. T. Thomson, E. I. Franses, and N.-H. Linda Wang, Adsorption, 12, 2006, 405-416.

3. R. B. Kasat, N.-H. Linda Wang, and E. I. Franses, Biomacromolecules, 8, 2007, 1676-1685.