Applicability of EmporeTMTLC Sheets for Forced-Flow Planar Chromatography. I. Characterization of the Silica Sheets

Abstract

Abstract Empore™ TLC silica sheets—a new separation medium for planar chromatography—are prepared from silica which is entrapped in an inert matrix of polytetrafluoroethylene (PTFE) microfibrils. It was established earlier that the separation power is only about 60% of that of conventional TLC. This was attributed to the very slow solvent migration velocity resulting from capillary action. In this paper the characteristics and applicability of EmporeTM TLC silica sheets are reported for the various forced-flow planar chromatographic (FFPC) techniques, such as overpressured layer chromatography (OPLC) and rotation planar chromatography (RPC). The preparation of the sheets and the relationship between the solvent front migration distance and migration time are given. The influence of the linear flow rate on the theoretical plate height and the relationship between the resolution and the linear flow rate are determined. Also, the influence of the development mode and solvent system on the densitometric evaluation is discussed. The influence of external force (overpressure or centrifugal force) on the structure of EmporeTM TLC silica sheets is demonstrated with the aid of scanning electron micrographs. The experiments show that Empore™ TLC silica sheets allow extremely rapid separations (5–20 min) by FFPC methods in all development modes. Good resolution is obtained because FFPC techniques are able to ensure the suitable mobile phase migration.