Preparation And Electrochromatographic Evaluation Of Some Novel Embedded Polar Groups Monolithic Silica Capillary Columns

Capillary electrochromatography (CEC) is a new micro-separation technique. Column is the core of CEC. Prepared novel CEC columns are effective ways that expand applications of CEC. Monolith played an important role in the field of separation science, which has attracted great concern of many chromatography workers. Monolithic silica column has been widely used in the field of micro-separation science due to its high mechanical strength, good solvent resistance, good penetrability and higher column efficiency.The literature published so far on CEC has concentrated mainly on the separation of nonpolar analytes using nonpolar traditional alkyl chains bonded-silica stationary phases (e.g., C18) in reversed phase (RP) mode, which provides relatively satisfactory results for separations of nonpolar analytes. However, the separation of polar substances is difficult in RP-CEC on this column. For many polar compounds, mobile phases employing little or no organic modifier must be used to achieve retention and separation. Organic modifier content is too low, the hydrophobic stationary phase has not been better wetting, which lead to bubble formation in CEC and interruption of the separation process. The embedded polar group silica-based stationary phase yield better performance in RP-CEC for polar compounds. The selectivity of polar compounds was improved because the embedded polar group enhanced the polarity of stationary phase. Now, Species of embedded polar groups stationary phase is still few in CEC. Some novel type of embedded polar group silica monolithic capillary columns were developed in this paper, the specific contents are as follows,1. A polar propylurea silica capillary monolith was prepared by in-situ synthesizing in fused-silica capillary by sol-gel process followed by surface chemical modification. The performance of prepared monolithic silica column was evaluated. The electrochromatographic behaviors of model polar solutes were investigated and the retention mechanism was also discussed.2. The phenyl amide propyl silica monolithic capillary column was prepared by sol-gel process followed by surface chemical modification. Alkylbenzene, alkaline compounds, phenolic compounds were used as model solutes to evaluate the performance of phenyl amide propyl silica monolithic stationary phase, and the retention mechanism was also discussed in detail. The experimental results indicate that neutral compounds were separated by RP mechanism. The basic solutes were separated by the mixed mode mechanism, which comprised hydrophobic interaction, electrostatic interaction and electrophoresis. In addition, polarity of stationary phases were enhanced the presence of amide. The mobile phases employing little organic modifier can be used to achieve effectively separation of polar phenolic compounds.3. A novel C16 monolithic silica column containing embedded amide-imine groups was successfully prepared for RP-CEC. The CEC properties of the new monolithic stationary phases were evaluated by using neutral, polar solutes as model compounds. The results indicate that the C16 monolithic silica column containing embedded amide-imine groups exhibit excellent RP electrochromatographic properties. In addition, the presence of amide-imine groups enhances polarity of stationary phase. Embedded polar groups of the stationary phase can improve the performance of separation of the polar analytes in RP-CEC.