| Cyclic olefin copolymer (COC) is a new type of thermoplastic material that is very suitable for microchip fabrication, due to its promising properties, such as good optical transparency, ease of fabrication and high chemical resistance. However, there are difficulties in the use of COC microchips without surface modification, because they may adsorb molecules with high hydrophobic moieties, particularly biomacromolecules, such as proteins or biogenic amines, which may cause the loss of analytes and adversely affect the repeatability of the analysis. Using appropriate additives or buffer solvent in the separation medium is an effective way to eliminate these adverse effects. The main purpose of this thesis is to select the appropriate additives or buffer solvents to eliminate the unexpected adsorption in order to achieve high efficient separation of substances which easily be adsorbed on COC surface. The dissertation consists of four chapters:Chapter I:The μTAS was reviewed comprehensively. Surface modification of microchannels and the analytical standard operations of μTAS were introduced.Chapter II:A microchip electrophoresis method with COC microchips and laser-induced fluorescence (LIF) detection has been established. After dynamic surface treatment of COC channels with HPC, ethanolamine, butylamine and dibutylamine were efficiently separated within100s using10mmol/L borate buffer (pH9.5) containing2.0%(m/v) HPC under an electric field of264V/cm. The limit of detection (LODs)(S/N=3) of the three three kinds of biological amines were in the range of0.16-0.32nmol/L. A linear correlation (r>0.99) of the three kinds of biological amines was obtained from1nmol/L to5μmol/L. The relative standard deviations (RSDs) of peak areas and migration times for the three biological amines were less than3.2%and0.48%, respectively. This method was successfully used to determine these biological amines in beer and red wine with satisfactory recoveries of93%-105%.Chapter III:Ethylene glycol solution was used as the electrophoretic running buffer in unmodified cyclic olefin copolymer (COC) microchips to minimize the interactions between the analytes and the hydrophobic walls of the plastic microchannels. Five amino acids that were labeled with fluorescein isothiocyanate (FITC) were used as model analytes to examine the separation efficiency. Five FITC-labeled amino acids were effectively resolved using a COC microchip with an effective length of2.5cm under optimum conditions, which included using a running buffer of20mmol/L sodium tetraborate in ethylene glycol and water mixture (80:20v/v), at pH6.7. A theoretical plate number of4.8x105/m was obtained for aspartic acid. The system exhibited good repeatability, and the RSDs (n=5) of the peak areas and migration times were no more than0.7%and3.4%, respectively. Furthermore, the system was successfully applied to elucidate these five amino acids in human saliva.Chapter Ⅳ: Carbon nanoparticles (CNPs) were synthesized by nitric acid based oxidation of kerosene soot and a mixture of water and acetonitrile was used to separate the CNPs by ultracentrifugation according to their size, moreover, their properties were studied by several characterization methods. The size and shape of the CNPs were characterized by using the COC microfludic-based electrophoresis combined with LIF. As the running buffer containing10mmol/L sodium dihydrogen phosphate and2%(m/v) HPC, the electrophorogram suggested that COC microchip-based electrophoresis could be used to determine the size distribution and fluorescence properties of CNPs, which was in favor of optimizing the synthesis and pretreatment conditions of CNPs, and provided a fast and sensitive tool for the characterization of CNPs.
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