Solvatochromic hydrogen bond donor acidity of cyclodextrins and reversed-phase liquid chromatographic retention of small molecules on a β-cyclodextrin-bonded silica stationary phase

Abstract

Values of the Kamlet-Taft hydrogen bonding (HB) donor acidity (α) and dipolarity/polarizability (π *) parameters for α-, β- and λ-cyclodextrins (CDs) are reported. They possess HB donor acidities in the range 0.21-0.12 and dipolarity/polarizability parameters of about 0.43. Both values are smaller than those for the aliphatic alcohol analogues. The reversed-phase liquid chromatographic retention behaviour of some small molecules on the β-CD bonded silica was compared with that on an octadecylsilylsilica based on the linear solvation energy relationship. It was found that he factors affecting retention on the two stationary phases are very different in that on the ODS column cavity formation and type A HB interactions determine retention whereas on the β-CD column dipolar and type A HB interaction determine retention. Differences in the retention properties of β-CD and ODS phases are rationalized in terms of types of solute-stationary phase interactions involved in the retention process.