CAPILLARY ELECTROPHORESIS AND SAMPLE INJECTION SYSTEMS INTEGRATED ON A PLANAR GLASS CHIP

The feasibility of miniaturizing a chemical analysis system on a planar substrate has been demonstrated for a system utilizing electrokinetic phenomena for sample separation and solvent pumping. Using micromachining techniques, a complex manifold of capillary channels has been fabricated in a planar glass substrate and the separation of a mixture of fluorescein and caicein within the channels was achieved using electrophoresis. The maximum number of theoretical plates obtained was about 35 000 for caicein, with 5000 V applied, corresponding to 2100 V between the injection and fluorescence detection points in the channels. The number of theoretical plates observed was in agreement with theory, indicating no interactions between the analyte and the glass walls. The electroosmotic flow rate in the glass channels was (4.5 +/- 0.1) X 10(-4) cm2/(V.s) using a pH 8.5 50 mM boric acid, 50 mM Tris buffer, comparable to (5.87 +/- 0.08) X 10(-4) cm2/(V.s) measured in fused-silica capillaries. Solvent flow could be directed along a specified capillary by application of appropriate voltages, so that valveless switching of fluid flow between capillaries could be achieved. These results provide a foundation for the design of more complex sample treatment and separation systems Integrated on glass or silicon substrates.