Preparation And Evaluation Of The Polyethylene Glycol Embedded Silica Monolithic Column For Gas Chromatography

Monolithic column was applied to chromatographic study since the 1960 s for the first time. Because of its simple preparation, long service life and low cost, it has been extensively and deeply researched in capillary electrochromatography, high performance liquid chromatography and hydrophilic chromatography. In gas chromatography, capillary chromatographic monolithic column has a large capacity of column and low permeability and its particular porous structure makes it simple and efficient for rapid separation of compounds even with a shorter length of the capillary. It has a great significance in improving the efficiency of gas chromatographic separation.But, the study on its application in gas chromatography technology is relatively few both at home and abroad. This article discussed the interaction mechanism between the stationary phase and the probe molecules by studying the thermodynamic parameters and linear solvation energy relationship in gas chromatography.In this thesis, a review focused on the preparation of monolithic column and its application in gas chromatography. Then a discussion on the influence of preparation conditions on the monolith structure was carried out and the optimal preparation condition was obtained, and then a polyethylene glycol embedded capillary silica monolithic column was prepared. On this stationary phase, the separation of some nonpolar compounds, n-alkanes, benzenes was carried out, the retention mechanism between probe molecules and stationary phase was analyzed through thermodynamic parameters and linear solvation energy relationship.The experimental results showed that:Firstly, in the process of the preparation of silica monolith, some factors, for example, concentration of acid, polyethylene glycol(PEG) content, alcohol content,water bath temperature, mixing time and aging temperature, had an influence on the mechanical strength and permeability of the monolithic column. Among them, the acid concentration and polyethylene glycol content played a dominant role in this study.Secondly, the result of the thermodynamic parameters showed that for each probe molecule, the interaction forces between probe molecule and stationary phase were invariable within the temperature range studied due to an excellent linear relationship between lnk and 1/T. The chromatographic retention of all probe molecules on this stationary phase was enthalpy-driven process.Thirdly, according to the result of the solvation parameters, the main interaction forces of this stationary phase with probe molecules were dipole-dipole interaction,hydrogen bonding interaction and dispersive interaction. And the contribution of each interaction was in the order of dipole-dipole interaction > hydrogen bonding interaction > dispersive interaction.Fourthly, the result of the application of the silica monolithic column showed that the separation effect of nonpolar compounds is better than the polar ones.