Experimental study of difference between streaming current and electroosmosis in single fused silica capillaries

Two electrokinetic phenomena, electroosmosis and streaming current are compared and examined whether these two are identical as the measuring methods of zeta potential, using a single capillary method. In addition of zeta potentials by both methods, variation of apparent radius of fused silica capillaries, which were used in this study, were measured with time for a long period. Two sort of experimental results were obtained. First, it was revealed that the capillary radius reduces in order of day. The extent of the change was as huge as exceeding micrometers. This origin is speculated to be a sort of soft substances, which may be a silicate polymer, generating on the surface. This may be reflecting difference of the surface properties, that is, difference of materials. And second, it was found that there exists a difference between electroosmosis and streaming current measurements. The electroosmosis values are about 10% larger than the streaming potential values for non-varied capillaries. When the surface is varied and capillary radius is reduced, the electroosmosis is affected more seriously than the streaming current.

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► It is concluded that electroosmosis and streaming current are not identical.
► Using fused silica capillary–water system, long time tests were carried out.
► The surface of fused silica capillary is varied and reduces the radius slowly.
► The electroosmosis values are about 10% larger for non-varied capillaries.
► Electroosmosis is seriously affected by the variation of the surface of capillary.