Studies On Microfluidic Capillary Electrophoresis Fluorescence Detection System Based On Silver-coated Liquid-core Waveguide

With the development of science and technology, the analysis instruments have been more and more miniaturized, automated, and portable. Miniaturized total analysis systems were just proposed for this purpose. Owing to its high efficiency, fast analysis speed, low sample and reagent consumption, and other advantages, the microfluidic CE system has been developed fast and becomes an important analysis method. Meanwhile, with the sample for detection being less and less, the detector with higher sensitivity was demanded. Liquid-core waveguides (LCWs) not only have the function to confine the light signal in a special path based on the inner total reflection, but also can be used as the separation and detection cell. Since much less light loss and longer effective absorbance path have been achieved in the LCWs, the LCWs have been used widely to simplify the optical structure and improve the detection sensitivity. In this paper, silver-coated LCW has been developed, and a simple and high sensitivity microfluidic capillary electrophoresis (CE) fluorescence detection system was estabilished with an automated sampling system.In Chapter1, the recent progress in microfluidic CE fluorescence detection system was reviewed. The LCWs with different claddings of air, low refractive index nonmetals, metals were introduced respectively, and their application in the optical detection systems was summarized. Finally, the purpose and design of this work were proposed.In Chapter2, silver-coated LCW with a large numerical aperture was developed, and a microfluidic CE fluorescence detection system based on the silver-coated LCW was established. The cladding materials, the fabrication method of the cladding, and the protecting approach of the cladding were optimized. The silver cladding was deposited to the outer surface of the silica capillary by silver deposit reaction and protected by coating a quick drying glue. A window was opened on the LCW capillary at the position illuminated by the laser. Then CE chips have been made with the silver-coated capillary, and used in microfluidic CE fluorescence detection system. The fluorescence collection efficiency of silver-coated LCW and Teflon AF-coated LCW was calculated and discussed, and the influence of the silver cladding thickness on LCW efficiency was investigated. The detection limitation for rhodamine6G was7.0×10-13mol/L(S/N=3) which was at the similar sensitivity of the system based on commercial Teflon AF-coated LCW. Baseline separation was achieved for all11fragments of ΦX174-HaeⅢ digest DNA marker, and the427bp DNA sample has been successfully detected.The RSD of the retention time and peak height were0.0%-0.4%and6.7%-8.3%(n=9) respectively for the107bp DNA sample.In Chapter3, the microfluidic capillary electrophoresis fluorescence detection system based on the silver-coated LCW was summarized.