Preparation and Evaluation of HPLC Chiral Stationary Phases Based on Cationic/Basic Derivatives of Cyclofructan 6

The cyclofructan 6 (CF6) macrocyclic-oligosaccharide was derivatized with five different substituents able to bear positive charges: propyl imidazole, methyl benzimidazole, dimethyl aminopropyl, pyridine, and dimethyl aminophenyl. The derivatized cyclofructans were reacted with triethoxysilyl-propylisocyanate as a linker to bond them to 5 mu m spherical silica gel particles and then used to prepare liquid chromatography columns. The bonded silica particles were analyzed to establish the bonding densities. A set of 34 chiral compounds including acids, neutral compounds, and bases was tested with nine different mobile phase compositions including two reverse phase (RP) acetonitrile/pH 4 buffer, three polar organic (PO) acetonitrile/methanol, and four normal phase (NP) heptane/ethanol mobile phases. No compounds could be separated in the RP mode. Eight compounds only could be enantioseparated in the PO mode and 21 compounds in the NP mode. The most effective chiral stationary phase was the propyl imidazole derivatized CF6 phase, provided no more than six imidazole substituents and two linkers are attached per CF6 unit.