Abstract: To connect a capillary with an electrophoresis chip, a dead volume was usually created due to a hole with a conical-shaped bottom formed by drilling into the edge of the chip after the capillary was inserted into the hole. The effects of the dead volume on the electrophoretic separation were simulated and evaluated by using a simulation software. A novel connecting PMMA electrophoresis chips to capillaries with the minimal dead volume was presented. A hole was drilled into the edge of the chip by using a 500 μm standard drill bit, then a home-made flattened drill bit was used to flatten the conical area, so a flattened-bottom hole was created, and a 375 μm-o.d. fused-silica capillary was inserted into the hole and fixed by using epoxy, which decreases the dead volume from 3.9 to 0.1 nL. The detecting point of the UV-absorption detection was put on the fused-silica capillary, so the electrophoresis on the PMMA chip could be directly detected by an UV-absorption detector. The electrophoretic analysis of vitamin B₂ was performed on the chip, and the number of theoretical plates was 73 000/m; the electrophoretic separation of three components of sulfamethoxazole, sulfadiazine and trimethoprim tablet was also preformed, resolutions among these three components were 4.5 and 1.9, the relative standard deviations for migration time were 1.0%, 1.4% and 1.0%, and relative standard deviations for peak height were 4.1%, 3.0%, 4.1%, respectively(n=5).

Key words: Poly(methyl methacrylate)(PMMA), Electrophoresis chip, Dead volume, Capillary, UV-absorption detection