Synthesis and characterization of cellulose derivative-based hybrid beads as chiral stationary phases for efficient chromatographic enantioseparation

Abstract

Polysaccharide derivatives have become the most attractive polymer candidates for the preparation of chiral stationary phases (CSPs) for efficient chromatographic enantioseparation due to their regular structure and high chiral recognition ability. However, the organic contents of traditional polysaccharide-based CSPs usually accounted for 20%, indicating that a big percentage of composition of the CSPs had no contribution to their enantioseparation powers. To resolve this bottleneck problem, four hybrid bead-type CSPs with organic contents of higher than 20% have been developed using cellulose tris(3,5-dimethylphenylcarbamates) and tetraethyl orthosilicate by a modified Stöber process in basic conditions. The hybrid beads could be formed more efficiently in basic conditions without using surfactant than in acidic conditions. The preparation conditions significantly affected the organic contents and morphology of the hybrid CSPs. Their enantioseparation properties were then evaluated by high-performance liquid chromatography. The obtained hybrid CSPs with higher organic contents exhibited better enantioseparation powers than those with lower organic contents and previous analogues derived from acidic conditions. For some chiral compounds, the hybrid CSPs exhibited even higher enantioselectivity than the commercial Chiralpak IB, which is also prepared from cellulose tris(3,5-dimethylphenylcarbamate) and is considered as one of the most popular immobilized-type CSPs nowadays.