Insights into chiral recognition mechanism in supercritical fluid chromatography III. Non-halogenated polysaccharide...

The majority of published enantiomeric separations by supercritical fluid chromatography (SFC) utilize chiral stationary phases (CSP) based on chemically derivatized amylose or cellulose, coated or immobilized on silica. There is a large diversity among these polysaccharide-type CSP enhancing the scope of chiral separation applications. But on the other hand, identifying the appropriate support for a given separation problem is rather difficult. Hence, this study aims to provide insights on the difference and similarity among the non-halogenated polysaccharide CSP in terms of retention and selectivity at a molecular level. Firstly, the potential of the clones provided by different manufacturers is evaluated with carbon dioxide - methanol mobile phases. Then different aspects of the chiral recognition mechanism contributing to the separations on 16 different columns of five distinct chiral selectors will be explored based on a large amount of experimental data acquired with the help of modelling and chemometric techniques. We report the influence of the ligand bonded to the polysaccharide on the non-enantio-specific interactions between the solute and the CSP, comparing phenylcarbamate to 3,5-dimethylphenylcarbamate, and 4-methylphenylester to 3,5-dimethylphenylcarbamate. In addition, we evaluate the impact of the silica treatment on the quality of the separation. The phases are characterized in terms of their retention characteristics assessed by the solvation parameter model and separation capabilities assessed by discriminant analysis.