| Cyclic Olefin Copolymer (COC) has been taken as an ideal material for microfluidic chips due to its excellent optical properties and chemical inertness. However, its hydrophobic surface, which easily leads to non-specific adsorption of the bio-molecules and poor separation efficiency and sensitivity, has been proved to be a big problem. In addition, the unstable electroosmotic flow caused by the unexpected adsorption also deteriorated the repeatability of the electrophoretic separation. To solve these problems, addition of some additives with special functional groups or other characteristics to the buffer solutions can effectively eliminate the problems. In this thesis, we studied the role of buffer additives containing multi-hydroxyl groups in the electrophoresis on COC microchips, and established two rapid analysis methods for several amino compounds. The thesis contains four following chapters:Chapter1:A brief introduction for micro total analysis system was made, which includes the materials and processes of the microfluidic chip production, the technologies for micro-channel modification, the detectors of microfluidic analysis and their applications in chemistry and life sciences.Chapter2:A series of compunds containing multi-hydroxyl group molecules, including ethylene glycol, glycerol, PVA and HPC were investigated as buffer additives in order to improve of the separation efficiency and repeatability of microchip electrophoresis on unmodified COC chips. Factors including viscosity, concentration of the background electrolyte, conductivity and pH of the buffer solutions were maintained same to evaluate the effectiveness of the type of the additives. Three FITC labeled biogenic amines (putrescine, cadaverine, tryptamine) were used as the model analytes for the comparison. The results showed that with the presence of any one of the additives, the separation efficiency was improved significantly. The macromolecules, such as PVA and HPC, can form gel-like structure in the aqueous solution due to the long backbone chain and huge number of hydroxyl groups, may act as a sieving medium and contribute to the more efficient separation than small molecules.Chapter3:A COC chip electrophoresis method with LIF detection was established for the rapid analysis of biogenic amines. HPC was chosen as a buffer additive based on the conclusion of the previous chapter. With10mM borate buffer containing2%HPC, the separation voltage of1800V, the effective separation distance of2.5cm, five FITC labeled biogenic amines could be baseline resolved within2min. The limits of detection (LOD, S/N=3) were in the range of2.5-17nM. Linear ranges of the calibration curves were0.02-5μM for methylamine and o-toluidine,0.05-10μM for putrescine, cadaverine and tryptamine (r>0.99), repectively. The relative standard deviation of the peak areas and migration times were less than4.0%and2.4%respectively. This method was successfully used for the analysis of tryptamine, putrescine, cadaverine in carp and snakefish samples, the recoveries of standard addition were83.6%-112.7%.Chapter4:A method for rapid analysis of catecholamines and certain amino acids with COC microchip with LIF detection was established. With2.5%HPC as the buffer additive in10mM borate (pH9.5) under the selected condition, two kinds of catecholamines and two amino acids completely separated within60s, with a separation voltage of1800V and an effective separation distance of2.5cm. The relative standard deviation of migration times and peak heights were less than3.2%and4.5%respecitvely. The method is simple and rapid with good reproducibility. It has been successfully used in the detection of catecholamines in some sports drinks. |
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