The Study And Application Of Microchip Capillary Electrophoresis/Electrochemical Detection

For over a decade, the area of micro total analysis systems, also called "lab on a chip", has been growing rapidly. The numerous advantages of incorporating several previously distinct processes into a miniaturized format include faster analysis time, decreased cost and waste production, portability, disposability.Capillary electrophoresis microchip (CE chip) is an emerging technology that has generated a great deal of interests in analytical chemistry. Like conventional CE, laser- induced fluorescence (LIF) remains one of the most sensitive detection techniques for CE chip. However, the implementation of LIF can be quite difficult. On the other hand, electrochemical detection (ECD) is relatively simple, inexpensive, applicable to a wide range of analytes, and easily miniaturized. This thesis is concentrated on the study of CE – ECD chip and its application in analysis of pharmaceuticals and biochemicals as described below.The pattern of the microelectrodes for CE – ECD chip was directly made on the surface of a microscope slide through the micromolding in capillaries (MIMIC) techniques and electroless deposition procedure. The copper microelectrode is fabricated by selective electroless deposition. And the fabrication of decoupler is platinum electrochemical deposition on metal film formed by electroless deposition. The whole chip was built by reversibly sealing the slide to the poly(dimethylsiloxane) (PDMS) layer with electrophoresis microchannels at room temperature. The fabrication of a hybrid chip device is simple, rapid and costless compared with the conventional method of glucose detection using glucose oxidase. Factors influencing the performance, including the detection potential, separation field strength, buffer concentration, were studied. The electrodes exhibited good stability and durability in the analytical procedures. Under optimized detection conditions, (30 mM NaOH, separation field strength of 200 V/cm and detection potential at 0.7 V), seven consecutive injections of glucose were performed. The relative standard deviation (RSD) of the migration time was 2.2 %, with that of the peak height was 4.4 %. And the glucose responded linearly from 10 μmol/L to 1 mmol/L. Furthermore, the glucose in human plasma from healthy individuals and diabetics was successfully determined, which was close to those got with HITACHI 7020 Automatic Analyzer in Jilin University Hospital. This work gives a newly alternative way to the quick determination of glucose in real sample with high sensitivity. So the miniaturized CE–ECD analysis system has the application prospect and attraction for clinical bioassays. Cu is sputtered onto PMMA, and copper electrodes are formed by photolithograph and wet etching; an electrophoresis chip is fabricated by thermally bonding the PMMA with copper electrodes to a PMMA substrate with microchannels. When seven consecutive injections of standard glucose were performed, the relative RSD of the migration time was 3.52 %, with that of the peak height was 1.12 %. Furthermore, factors influencing the performance, including the detection potential, separation field strength were studied. Under optimized detection conditions, (30 mmol/L NaOH buffer, 0.7 V detection potential and 50 V/cm separation field strength), arginine responded linearly from 40 μmol/L to 3 mmol/L. The arginine and leucine got fast and good separation by 30 mm-long channel.