Planar dielectrochromatography — A perspective technique

Abstract

To simulate front displacement through porous media (TLC plates) the effect of the axisymmetric alternating electric fields on liquids confined in capillary tubes was studied. This electric field causes liquid displacement through capillary tubes with great velocity, the main action being on the liquid column meniscus. Capillary tubes were used to enable understanding of the flow phenomena which occur in porous media. It was observed that the displacement velocity of the liquids confined in capillary tubes depended on the magnitude of the alternating electric field, the electric properties (conductivity, permittivity) of the liquids, the frequency of the current, and the tube material.In normal TLC practice, migration of the mobile phase through the layer is controlled by capillary forces. The velocity and migration distance of the mobile-phase front in prous media can be increased by application of an external electric field, an effect called by us ‘dielectroosmotic flow’ (DEOF), because of its similarity with electrokinetic phenomena. DEOF is observed on different TLC plates and paper strips developed with non-polar and polar solvents. As a result the separation of some compounds was improved. This method is a hybrid of electric forced flow and classical TLC; we have named it ‘planar dielectrochromatography’ (PDEC).A horizontal chromatographic chamber has been constructed and has been used to investigate the principles of planar dielectrochromatography, specifically the increase in front velocity and the dielectrophoretic force generated at granule level on different ready-to-use plates.