Electroosmotic pumping and electrophoretic separations for miniaturized chemical analysis systems

Electroosmotic pumping is highly efficient in capillaries of less than 100 mu m inner diameter bearing an immobilized surface charge. Electric fields in the kV cm^-1 range allow for liquid motion of several mm s^-1 in the case of an aqueous electrolyte. This pumping mechanism is used for miniaturized chemical analysis systems. Flow and mixing behaviour in branched channels are characterized. A capillary electrophoresis device allows for repetitive, electroosmotic injections of 100 pL samples, for efficiencies of up to 200000 theoretical plates in less than a minute, and for external laser induced fluorescence detection at any capillary length of choice between 5 and 50 mm.