QUININE AND QUINIDINE DERIVATIVES AS CHIRAL SELECTORS .1. BRUSH TYPE CHIRAL STATIONARY PHASES FOR HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY BASED ON CINCHONAN CARBAMATES AND THEIR APPLICATION AS CHIRAL ANION-EXCHANGERS

Quinine and quinidine carbamates, respectively, have been immobilized onto porous silica utilizing two different types of spacer and/or graf ting modes, obtaining four brush type chiral stationary phases (CSPs). These CSPs have preferentially been operated with buffered aqueous mo bile phases to resolve the enantiomers of acidic analytes involving io n pair mechanisms as the dominating binding and/or retention principle beside additional adsorption towards the modified silica surface. The spectrum of successfully resolved racemates contains chiral aryl-, ar yloxy- and arylthiocarboxylic acids, as well as N-derivatized amino ac ids (DNB-, B-, Ac-, F-, DNP-, DBD-, Fmoc-, Boc-, Z-, DNS-amino acids, etc.) and many other chiral acids including also sulfonic, phosphonic and phosphoric acids. The influence of mobile phase parameters, as wel l as of structure variations of analytes on retention and enantioselec tivity was evaluated. Thus, a chromatographically derived tentative ch iral recognition model is proposed for DNB-amino acids which are resol ved into enantiomers with exceptionally high alpha-values (e.g., DNB-L eu with an alpha-value of about 7).