Effect of surface microstructures on the separation efficiency of neurotransmitters on a direct-printed capillary electrophoresis microchip

The effect of surface microstructures of microchannels on the separation efficiency in microchip electrophoresis has been studied. In order to understand the influence of the surface microstructures on the microchip electrophoresis performance, a thermostatic system was designed and fabricated for precisely control of the chip temperature since the surrounding temperature causes a significant effect on the separation efficiency. The periodically ordered microstructures (dams) of different sizes were fabricated on the microchannels by a simple printing process using different gray levels of the vector graphic software. And the influence of dam sizes in microchannels on the separation efficiency was evaluated by using the number of theoretical plates (N) and the relative resolution (Rs'). Analyzing the variations of mixing elements caused by the periodically ordered dams in the separate channel and elution time, we found that with small dam size fabricated at low gray level of ca. 30%, the resolution of dopamine and epinephrine increased slightly, while it decreased obviously with larger dam sizes especially fabricated at gray level of 50%. (C) 2009 Elsevier B.V. All rights reserved.