THERMAL-TREATMENT OF SUPPORTS FOR CHIRAL STATIONARY PHASES AND ITS INFLUENCE ON ENANTIOSELECTIVITY

Thermal treatment of silica at temperatures above 800-degrees-C leads to a significant decrease in the silanol surface concentration. Chiral modification of such thermally treated silicas gives derived stationary phases with lower specific surface areas and lower surface concentrations of ligands. The resolution of chiral amides was in some instances better with thermally treated pi-donor chiral stationary phases based on (R)-1-(1-naphthyl)ethylamine in comparison with the corresponding untreated phases. Correlation experiments with two homologous series indicate that retention also depends on other hydrogen-bond acceptors such as secondary hydroxyl groups near the chiral selector.