Silica-based inert packings for supercritical fluid chromatography.

Retention of polar and non-polar compounds on ODS-silica gel columns was investigated in terms of the pore structure of silica gel and surface modification. The purpose was to develop inert columns for supercritical fluid chromatography (SFC) using carbon dioxide as a mobile phase without a modifier. Utilization of silica gel having larger pore diameter and sufficient end-capping of residual silanol groups after primary surface modification promoted the preparation of inert packings. Three types of ODS-silica gel columns: without end-capping, end-capped in a liquid phase and end-capped in a vapor phase, were compared by applying each to the separation of carrot extract with supercritical CO2.