Separation mechanism of chiral stationary phase based on quinine and crown ether for the direct stereoselective separation of amino acids

A novel chiral stationary phase combining quinine and crown ether (QN-CR CSP) was developed to separate amino acid enantiomers. This CSP showed good enantioselectivity for some amino acids. Since the synergistic effect of ion exchange and complexation in chiral recognition of amino acids, a new adsorption isotherm was built. Using the method of frontal analysis by characteristic point (FACP), the adsorption isotherms of tryptophan (Trp) under different mobile phase conditions were determined and fitted the proposed adsorption isotherm model well. With the increase of the competition between metal cationic and amino to crown ether, the equilibrium constant of complexing adsorption was found increased. The chiral separation ability was decreased. The adsorption isotherm improved the understanding of the retention behavior of amino acids on QN-CR CSP, which was also benefit to optimize the structure of the stationary phase.