Development of miniaturized capillary electrophoresis system with electrochemical detection

Abstract

Over the past decade, development of microanalytical devices has become an important trend in analytical research. An ideal miniaturized analytical device can shrink a laboratory full of instrumentation into one single lab-on-a-chip which incorporates sample acquisition, pretreatment, injection, separation, derivatization, and detection. The goal of this dissertation work was to develop a miniaturized capillary electrophoresis (CE) system with electrochemical detection (EC) to analyze biological and environmental samples. The miniaturized CE-EC system was first demonstrated on PDMS/glass hybrid chip in a urinary 4-aminophenol determination. The fabrication of hybrid chip involved the microfabrication of a Au thin-film electrode and fabrication of PDMS piece with patterned channels. This system was found to be unstable and give poor performance. To improve the overall performance, several steps were taken. First, a portable and cheap power supply was developed which could provide up to 4 kV output and perform three different types of sample injections. Second, to overcome the drawbacks of the Au thin-film electrode, a new microwire working electrode design was developed by placing a metallic microwire into the electrode alignment channel in the PDMS piece. The new working electrode proved to be more sensitive and flexible and have a higher collection efficiency than microfabricated electrode. The developed portable and sensitive microchip CE-EC system was then applied to aerosol analyses and antioxidant profiling.