| Capillary zone electrophoresis (CZE) has emerged as a powerful method for analyzing ionic compounds, but is not applicable to the separation of uncharged analytes. Micella electrokinetic chromatography (MEKC) is capable of separating both neutral species and ions. The MEKC separation is based on the differential partitioning of analytes between the micelle (pseudostationary phase) and the aqueous phase. However, the presence of micellar additives in MEKC may cause detection problems in its combination with mass spectrometry and some other detection techniques. Additionally, MEKC is more restricted in size and hydrophobicity of the separated solutes than CEC. Because CEC combines high column efficiencies with the selectivities offered by certain chromatographic materials. CEC is a relatively new micro-separation technique that combines the high efficiency of capillary electrophoresis (CE) and the high selectivity of high performance liquid chromatography (HPLC). Accordingly, it has attracted more and more attention in recent years.Most of the reported work concerning CEC separation and analysis so far has been focused on the use of particle packed capillary column. The procedure is laborious and need high experimental skill for reproducible columns packing and especially retaining frits preparation. Moreover the problems associated with gas bubble formation and heterogeneity of electric field have to be eliminated as well. Recently introduced polymer-based monolithic capillary columns has quickly become well-established stationary phases in CEC as they eliminated the need of frits and packing procedures. The large variety of available chemistries make these columns an attractive alternative to columns packed with particulate materials.In this paper, we develop two new types of polyacrylamide-based monolithic columns. The traditional monomers have acrylamide, N-isopropylacrylamide, methacrylamide, butyl methacrylate, N-allyldimethylamine. And cross-linking agents include piperazine diacrylamide and methylene diacrylamide. The monomer N,N-diethylacrylamide and crosslinker lemonene diacrylamide were synthesized. They were used to replace the traditional acrylamide and methylene diacrylamide. Hydrophobicity of the stationary phase becomes stronger. So it is more conducive to the separation of hydrophobic compounds.The paper consists of three chapters. Chapter one:The basic theories and development of CEC are simply elucidated. The preparation, characterization and application are specified. Effect of CEC operating parameters on the separation behavior is briefly reviewed. Chapter two:In this chapter, the preparation of porous polyacrylamide-based monolithic columns via vinyl polymerization using N,N-diethylacrylamide, methylenebisacrylamide, vinylsulfonic acid and lauryl acrylate as monomers in mixtures of aqueous buffer and N-methylformamide has been developed. The effect of electric field strength, acetonitrile concentration, buffer concentration and buffer pH value on electroosmotic flow (EOF) and separation has been investigated. At the same time, the evaluation of EOF reproducibility and the useful life of column is elucidated. Under the optimum experimental conditions, a good baseline resolution for 7 aromatic ketones including single ketone and 1,2-diketone is obtained within 13 min. Chapter three:We have further developed a new kind of polyacrylamide monolithic column on the basis of Novotny and others. Lemonene diacrylamide which is synthesized in the laboratory is used in place of traditional methylene diacrylamide. Hydrophobicity of the stationary phase becomes stronger. So it is more conducive to the separation of hydrophobic compounds. It is found that its performance is good by studying electroosmotic flow, column efficiency, reproducibility and column life. In despite of there are some shortcomings, its research will be further strengthened toward their practicality. |
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