| Capillary electrophoresis is a type of micro-separation methods that separates samples by their various properties using capillary as the separation channel and high-voltage electric fields as driving force. For the features of its efficient, fast, and trace quantity, capillary electrophoresis is becoming to the fastest growing areas of analytical chemistry. As one of six kinds of separation modes of CE, capillary electrochromatography is a hybrid technique that combines the high efficiency of capillary electrophoresis and good selectivity of high performance liquid chromatography, which is the new aspect and have been focus of chromatography development. Chromatography column is the heart of chromatography technique, while stationary phase is the key component of chromatography column. However, the stationary phases existed could not meet the demand of analysis as the samples are becoming more complicated, therefore, the development of new stationary phases for CEC to address this issue is of great significance.Monolithic column is a kind of chromatography column which can be prepared by sol-gel and in-situ free radical polymerization technology. Silica based monolith exhibits high permeability and column capacity, excellent solvent tolerance ability, and mechanical stability, however, there are only siloxane bonds in this kind of monolithic column which is restricted for further use by its poor hydrolytic stability, which could be improved by modification and organic-inorganic hybrid. Hybrid silica monolith was synthesized through a "one pot" approach by inserting a functional group and content with the separation demand. The characteristic of structure and selectivity of the stationary phase could be controlled by changing the ratio of the precursor. The Si-C bond and monolith were combined by covalent bonds, which could overcome the disadvantage of poor stability of the stationary phase modified after column.Supramolecular chemistry is a kind of emerging subject, which deals with the specific recognitions between molecules. The host-guest interactions, which are exerted by supramolecular compounds, can provide a promising prospect for chromatographic separations with high selectivity. They have been widely used for purification and separation of complicated mixtures. Nowadays, it has been attracted considerable attentions that the synergistic reaction of two kind supramolecular compounds on the separation of complicated samples, and the use as stationary phase on CEC has been reported, while it has received scant attention on CEC monolithic columns. Several kinds of novel supramolecular liquid crystal and liquid crystal crown ether with terminal vinyl were synthesized, and vinyl hybrid silica monolithic column was prepared in this paper, then the supramolecular was bonded to the monolith by free radical polymerization reaction. The electrochromtographic performance of the column was systematically studied, and was used in real samples. The main points of this dissertation are listed as follows:1. Terminal-vinyl supramolecular liquid crystal 4’-(ω-undeceny-1-lyoxy)-4-xenol (UX), liquid crystal crown ether 4-allyloxy -4’-(4’-carboxylbenzo 15-crown-5)-biphenyl (PCB),2-[4-(ω-undeceny-1-yloxy)-phenyl]-2-[4’-(4’- carboxybenzo-15-crown-5)-phenyl] propane (UCP) and 4- (ω-undecenyl-1-lyoxy)-4’-(4’-carboxylbenzo 15-crown-5)-biphenyl(UCB) were synthesized, which could be bonded to vinyl hybrid silica monolithic column. Melting point test, infrared spectrum, Raman spectrum and mass spectrum were used to confirm the structure and purity of the compounds. Vinyl hybrid silica monolith was prepared, the condition such as the dosage of porogenic agent, silylating reagent and urea were investigated. After optimizing preparation conditions, the pore diameter was measured by mercury porosimetry, and the median pore diameter was around 3μm.2. The terminal-vinyl liquid crystal 4’-(ω- undeceny-1-lyoxy)-4-xenol (UX) was used to modify terminal-vinyl organic-inorganic hybrid silica monolithic column by free radical polymerization procedure. Naphthol, PAHs, phthalate ester and steroids were successfully separated on the column and the separation effects were compared with unmodified column. The separation conditions including organic solvent, pH, and buffer agent on the effect of separation were investigated. The mechanism was inferred to hydrophobic interaction supplied by alkyl chain and hydrogen bonding supplied by hydroxide on liquid crystal.3. The terminal-vinyl liquid crystal crown ether 2-[4-(ω-undeceny-1-yloxy)-phenyl]-2-[4’-(4’-carboxybenzo-15-crown-5)-phenyl] propane (UCP) was firstly used to modify hybrid silica-based monolithic column possessing vinyl ligands by free radical polymerization procedure. Polycyclic aromatic hydrocarbons, benzenediols, carbamate pesticides and steroids, were successfully separated on the column. Compared with unmodified monolithic column, the selectivity was observably improved, which was caused by the high electron cloud hydrogen bonding on crown ether and hydrophobic interaction on liquid crystal chains.4. Two terminal-vinyl liquid crystal crown ethers 4-allyloxy -4’-(4’-carboxylbenzo 15-crown-5)-biphenyl (PCB) and 4-(ω-undecenyl-l-lyoxy)-4’-(4’-carboxylbenzo 15-crown-5)-biphenyl (UCB) with different alkyl groups were introduced to modify hybrid silica monolithic columns possessing vinyl ligands. Phthalate esters, phenols and nucleotide acids, were successfully separated on the column and the results were compared with UX modified column and unmodified column. The results indicated that the hydrophobic interaction played an important role on UCB column and UX column, the separation effect on phthalate esters was better than PCB column, while the synergy of hydrogen bonding interaction and hydrophobic interaction makes the separation on phenols better.5. Determination of imidacloprid and carbendazim residues in tomato was performed using capillary electrochromatography with a terminal-vinyl organic-inorganic hybrid silica monolithic column modified by liquid crystalline crown ether (UCB-VTMS-TMOS). Standard addition method was employed to overcome the matrix effects which were thoroughly investigated in the article. Satisfactory recoveries were obtained and the limits of detection were both below the MRL values stipulated by CAC. The result showed the method developed was applicable to the determination of imidacloprid and carbendazim residues in tomato with rapid analysis and simplicity.6. A kind of ionic liquid,1-allyl-3-methyl imidazole chloride (AMC) was synthesized; the structure was examined by infrared spectrum and nuclear magnetic resonance and was used to modify the vinyl hybrid silica monolith by free radical polymerization procedure. Nucleotide acids, phenols and benzoic acid compounds were separated on the column and the separation mechanism was discussed. Compared with unmodified column, the selectivity improved, which was believed to the hydrophobic interaction on carbon chain, hydrogen bonding interaction and electrostatic interaction on imidazole ring. |
PDF Full Text Request