Preparation Of Nanometer Stationaries And Their Application In The Capillary Electrophoresis

This dissertation consists of five chapters, including research progress of nanoparticles used as modifier stationary and pseudostationary; etched bare fused-silica capillaries for online preconcentration of amino acids in CE; preparation of nanometer silica particles and their application in the capillary electrophoresis, and the prospect of the present research work.In chaper 1, applications of nanoparticles are reviewed. The theory of capillary electrophoresis and its application, using nanoparticles as coating materials and pseudostationary were given. The goal of this dissertation was also presented.In chaper 2, capillary electrochromatographic separation of aromatic compounds using gold nanoparticle as stationary phase was reported. This technique used octadecylamine-capped gold nanoparticles to coat the inner surface of the fused silica capillary column. The hydrophobic gold nanoparticles protected by octadecylamine were prepared by using ethanol as reduction in reverse micelle through microwave dielectric heating. The average diameter of octadecylamine-stabilized gold nanoparticles was 4.53±0.79 nm. The separation performance of this type of column was studied using open tubular capillary electrochromatography (ot-CEC) mode. By changing the percentage of the organic modifier, pH value and concentration of the buffer, and the method used to prepare the column, the mixture of thiourea, phenol and biphenyl was well separted. The results showed that the separation repeatability of these columns were acceptable.In chaper 3, etched bare fused-silica capillaries for online preconcentration of amino acids in CE are studied. An online preconcentration method based on electrostatic interaction between the analytes and inner surface of the capillary column was developed for the determination of zwitterionic analytes such as amino acids in CE coupled with a DAD. The amino acids possessed positive charges when they were dissolved in an acidic solvent. When they were injected into the column, they were attracted by the negatively charged inner surface of the fused-silica capillary column. An etched column was used to increase the area of the capillary's inner surface and, consequently increase the electrostatic interaction between the amino acids and the inner surface of the capillary column. It was found that when the sample was injected at 10 psi for 1 min and the pH value of the sample was 4, the amount of amino acids attracted to the inner surface of the capillary was maximum. Under these optimized experimental conditions, the detection sensitivity of CE-DAD was enhanced by 5200, 2800, and 3100 times for asparagine, tryptophan and phenylalanine, respectively, compared with normal CE separation. The method provided good reproducibility in terms of both migration time and peak height. It can be successfully used for the preconcentration zwitterion.In chaper 4, preparation of nanometer silica particles and their application in the capillary electrophoresis are investigated. Nanometer silica particles used as pseudostationary in CE can separate neutral samples such as aniline and thiourea. The structure and character of silica particles are briefly reviewed. The effect of the contents of water in the solution on the diameter of the nanometer silica particles were studied at 25℃. The effect of the diameter of the silica particles used, pH value, etc. on the separation efficiency were also studied.In chaper 5, the final part of the dissertation, the summing-up of the dissertation is presented and the prospect of this research is discussed.