A new approach of preparing monolithic silica column was founded by adopting an improved sol-gel technology with tetramethoxysilane and polyethylene glycol as the matrix materials. The reason of resulting in crack and deformation of monolithic column was explained. By using N,N-dimethylformamide and a heat treatment procedure, the problems of crack and deformation in preparing the column were solved and the drying time was shortened greatly. In addition, the methods of fabricating mesopore and the effects of porogen solvent of different concentrations on monolithic silica column were investigated. The results show that the column prepared possessed bimodal pores structures with micrometer-size co-continuous through-pores and silica skeletons which have nanometer-size mesopores, straight appearance, high porosity, good chemical and mechanical stability. The characteristics would favour the separation with a rapid speed and high efficiency for both small molecules and macromolecules.
The formation origin of two peaks in micellar electrokinetic capillary chromatography by using cetyltrimethylaminium bromide (or sodium dodecyl sulfate) as pseudo stationary phase is studied. It is pointed out that two peaks may appear for one component in certain conditions. Experiments show that the relative areas of the two peaks of the corresponding component depend on the time and temperature of reaction between the analyte and the surfactant, and the concentration of surfactant in the sample solution. One of the two peaks increase with the increase of surfactant concentration in the sample solution while reverse for another peak. Temperature can accelerate the reaction process. This means that the interaction between analyte and surfactant is a slow process, and a stable substance can be produced from the interaction and leads to the formation of two peaks. The standpoint is confirmed by the infrared and nuclear magnetic resonance spectra of the product from the reaction between cetyltrimethylaminium bromide and m-hydroxyl benzoic acid.
