Preparation Of Mixed Stationary Phase Based On Graphene And Its CEC Separation

Capillary electrochromatography (CEC) is a micro separation and analysis technology combined with the merits of both capillary electrophoresis (CE) and high performance liquid chromatography (HPLC). Stationary phases were prepared through physical or chemical methods to modify the capillary wall with different materials. Samples were separated based on the different distribution coefficients and the different electrophoretic mobilities of the samples on the stationary phase. The open-tubular (OT) column is easy to be prepared. It does not require the frits and packing particles. Therefore, it does not have the problem of bubble formation. It has the advantage of high separation efficiency. However, the column capacity is small because the stationary phase only existed on the capillary wall surface. So it is very important to develop different ways to improve the surface area of stationary phase and consequently increase the column capacity.In this paper, based on the grapheme oxide (GO), different types of OT-columns modified mainly with mixed mode stationary phases were prepared. Polycyclic aromatic hydrocarbons (PAHs). protein、amino acids were used to evaluate the chromatographic performance of these columns. The chromatographic separation mechanisms of these columns were explored and the separation conditions of all the samples were optimised. This thesis includes mainly the following contents:1. Preparation of the OT-column using β-cyclodextrin (β-CD) modified graphene oxide as the stationary phase and the separation performance in CEC.First,3-AMDS was modified onto the capillary wall and used as the coupling agent to bond GO onto the inner surface of capillary column. This process was allowed to repeat for more than one time to increase the surface coverage. Then β-CD was modified on graphene oxide through 3-AMDS. The column was characterized by scanning electron microscope (SEM). PAHs and L/D-tiyptophan were used to evaluate the chromatographic performance on two layers GO+β-CD@column. The effects of the content of MeOH in the mobile phase, separation voltage, and the concentration of buffer on the separation performance were studied systematically. The experimental results showed that PAHs and L/D-tryptophan were successfully separated on the two layers GO+β-CD@column.2. Preparation of the OT-column using gold nanoparticles modified graphene oxide as the stationary phase and the separation performance in CEC.First,3-AMDS was modified onto the capillary wall and used as the coupling agent to bond GO onto the inner surface of capillary column. Then gold nanoparticles was modified on GO through 3-AMDS. After that, one column was further derived with n-octadecylmercaptan (C18-SH). The separation performances of these two columns were compared. We investigate the effects of the content of MeOH in the mobile phase, on the separation of thiourea, naphthalene, and biphenyl were investigated. The separation ability of GO+Au+C18-SH@column was tested using white egg as analytes. The separation results showed that the GO+Au+C18-SH@column has the great potential application for protein separation.3. Preparation of the OT-column using silica sol modified graphene oxide as the stationary phase and the separation performance in CEC.Using AMDS as coupling agent, GO and silica sol were bonded onto the inner surface of capillary column. Three columns with different compositions were prepared. The structures of these stationary phases were characterized by SEM and energy dispersive X-ray spectrometry (EDS). The effects of the content of MeOH in the mobile phase, separation voltage, and concentration of buffer on the retention factors of three neutral compounds were studied systematically. The experimental results showed that the best separation performance was obtained on GO/SiO2-C18@column. The separation performance of GO/SiO2-C18@column was further tested by separating seven neutral samples and egg white.