| 1. Research of Preparing Monodisperse Submicro-meter SiO2 Sphere Particles via Sol-Gel ProcessingThe synthesis of new novel monodisperse, submicro-meter SiO2 sphere particles by controlled hydrolysis and condensation of dilute and concentrated solutions of tetraethyl orthosilicate (TEOS) has been studied based St?ber processing. A media (ammonia) is used as a morphological catalyst of the reaction. The effects of solvents and TEOS concentration on the degree of monodispersity of the particles are discussed. Further, other factors which affect the formation of SiO2 particles, such as reaction temperature are also investigated. The scanning electron microscopy (SEM) is employed to monitor particle growth, particle number concentration, the surface formation of SiO2 particles and particle size distribution. Particles in the range of 300 to 1000 nm are produced with standard deviations around the mean diameter below 7.6%.2. Research of Preparing New Novel Monodisperse Micro-meter SiO2 Sphere Particles via two-phase ProcessingLarger monodisperse SiO2 sphere particles in the range of 1μm to 3μm are produced via two-phase processing for chromatography high-speed separation and analysis. The solution of containing initial SiO2 sphere particles produced by controlled concentration of tetraethyl orthosilicate (TEOS), water, ethanol and ammonia was fed continuously with TEOS and alcohol containing ammonia. At the same time, the factors that affect the preparation of SiO2 particles, such as initial SiO2 particles diameter, quantity, the order of continuously adding TEOS and alcohol containing ammonia, the quantity of addition, the interval time, the stirring time, reaction temperature and aging time were studied. Finally, micro-meter monodisperse SiO2 sphere particles with varied diameter were synthesized.3. Research of evaluation of 1-μm modified C18 silica stationary phase for pressurized capillary electrochromatographySelf-assembly 1-μm modified C18 silica stationary phase was used for the pressurized electrochromatography (p-CEC). The stationary phase was packed into fused silica capillaries of 100μm i.d. for a length of 20 cm (total length: 45cm) and also used for micro-high performance liquid chromatography (micro-HPLC) running the experiments with the same instrumentation; The efficiency of the C18 column was characterized through the height equivalent to a theoretical plate (HETP) of Thiourea, Naphthalene, Toluene, Benzene, and Styrene. The resolution of column efficiency by p-CEC was strongly influenced by several experimental parameters such as applied electric field, mobile phase composition, pH, ionic strength, etc. Optimum experimental conditions were found applying 15 kV at 27°C and eluting with methanol–sodium phosphate buffer at pH 7.8 (7:3, v/v). The same capillary was tested for micro-HPLC experiments. The column efficiency for organic compounds reached as high as nearly 200,000 theoretical plate numbers per meter. |
