MECHANISTIC STUDIES OF ELECTROOSMOTIC CONTROL AT THE CAPILLARY SOLUTION INTERFACE

The electrokinetic phenomena at the silica-solution interface under the influence of applied radial electric potential gradient were analyzed by a theory based on the Gouy-Chapman-Stern-Grahame (GCSG) model and the induced effect across the capillary wall. The effect of adsorbed ions at the silica-solution interface on the direct control of electroosmosis was studied with the application of lithium ions, tin(IV) ions, and dodecyltrimethylammonium bromide (DTAB). In addition,various organic coatings, including butyl phase, amino phase, and (glycidoxypropyl)trimethoxysilane-ethylene glycol diglycidyl ether (GOX-EGDE), were employed for investigating the effect of surface deactivation on the direct control of electroosmosis. The fundamental relationship between the microenvironment at the silica-solution interface and the direct control of electroosmosis obtained from our experimental and theoretical results is presented and discussed.