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[Preliminary study on planar two-dimensional capillary electrophoresis].

Capillary Electrophoresis (CE) system with rectangular cross section columns is integrated on quartz monocrystal plate. Because of its high surface-to-volume ratio and excellent heat conductivity of quartz, rectangular capillary is extremely efficient in dissipating heat compared to conventional circular capillaries. Comparative study showed that much higher electric field strength can be applied to this system without bubble formation. Another advantage of rectangular geometry channel is better detection ability because of the elimination of optical path distortion. The effectiveness of the planar CE has been demonstrated by comparing the separation of two solutes in phosphate buffer between rectangular and circular cross section column with same area. We also found that the separation efficiency can be improved dramatically by decreasing the channel dimension, which underlies the miniaturization of planar CE. In addition, injection by micro injector eliminate sample biasing and increase reproductivity. A simple manifold of rectangular flow channels are fabricated on quartz substrate. By use of electroosmotic pumping it is possible to control the direction of fluid flow in the manifold of intersecting channels without the use of valves. The experimental results proved that the band dispersion after the valveless switching is almost negligible, showing that the two dimensional separation is possible. The main contribution to band-broadening in our capillary electrophoresis is longitudinal diffusion, injection delay time and wall adsorption. In some cases the wall adsorption make the most contribution. Optimum efficiency depends on minimization of these unavoidable sources causing band broadening.