Adsorptive Interaction of Chiral Amino Acids on β -Cyclodextrin Bonded to Silica Particles

Abstract

The adsorption of certain chiral amino acids from aqueous solution onto β-cyclodextrin silica particles (CDS) had been investigated with the aim of in-depth understanding of the host-guest interaction. The adsorption intensity was found to be strongly dependent on the aqueous phase pH and this dependence could be interpreted from a model for neutral spe-cies adsorption in all cases. Adsorption equilibrium data fitted well to the Freundlich isotherm. The adsorption efficien-cies of L-amino acids were found to be higher compared to the corresponding D-isomers. Hydrogen bonding and hy-drophocities of amino acids were responsible for the differences in adsorption, by influencing the strength of interac-tions between the amino acid and CDS. The adsorption rate curves for all the molecules appeared to be typical of the pseudo second-order kinetics. Infrared spectral analysis has been performed to characterize adsorptive interaction. The porous structure of CDS as revealed by scanning electron micrograph thus shown to be promising materials for enanti-oselective separation of amino acids. In addition, molecular modeling studies performed on such molecules were found to correlate very well to the experimental results obtained.