Preparation Of Ionic Coating Capillaries And Their Application In Capillary Electrophoresis

Capillary electrophoresis (CE) and capillary electrochromatography (CEC) are promising microseparation analysis techniques; they have the advantages of high efficiency, high speed, small sample consumption and high automation level. The development of CE and CEC is dependent on the improvements in instrumentation design, column technology and understanding of the underlying phenomena. However, it has a long way to go to become the routine analysis method as HPLC with high selectivity, good reproducibility and stability. The nature of capillary is critical for the separation. Based on these observations, the present author intends in this thesis to develop some fabrication techniques for ionic coating capillaries, and investigate their applications in CE and CEC. In addition, a novel macrocyclic molecule, cucurbit[7]uril, is for the first time proposed as an additive for CE separation.1.In Chapter 1, the development of the ionic coating for capillary electrophoresis and capillary electrochromatography is reviewed.2. In Chapter 2, a zirconia-coated capillary is prepared by means of sol-gel technique. Its electroosmotic flow (EOF) properties are investigated in a variety of nonaqueous media (methanol and mixtures of methanol and acetonitrile). The zirconia-coated capillary exhibits the switchable EOF whose direction and magnitude are strongly dependent on the properties of nonaqueous solvents composition, their apparent pHs (pH*), and the electrolytes used (hydroxymethyl aminomethane and ammonium acetate). It is found that the isoelectric point (pI) of the zirconia-coated capillary move to higher pH* with increasing acetonitrile content from 0 to 75%(V/V) when tris (hydroxymethyl) aminomethane is used as an electrolyte. The nonaqueous capillary electrophoresis (NACE) separations of several alkaloids are investigated in the positively charged zirconia-coated capillary. The effect of solvent composition on the separation resolution and selectivity is also studied. In addition,comparison of separation between coated and uncoated capillaries in nonaqueous media is performed.3. In Chapter 3, an ordered mesoporous titania film is introduced to coat a capillary by means of sol-gel technique. Its electroosmotic flow (EOF) property is investigated in a variety of nonaqueous media (methanol, formamide and N, N-dimethylformamide and mixtures of methanol and acetonitrile). The titania-coated capillary exhibits distinctive EOF behavior whose direction and magnitude are strongly dependent on various parameters such as the solvent composition, apparent pHs (pH*) and the electrolytes. The nonaqueous capillary electrophoresis (NACE) separation of several alkaloids is investigated in the positively charged titania-coated capillary. Comparison of separation between coated and uncoated capillaries under optimum nonaqueous condition is also carried out.4. In Chapter 4, two new methods, sol-gel and chemical bonding methods, are proposed for preparation of sulfonated fused-silica capillaries. In the sol-gel method, a fused-silica capillary is coated with the sol solution obtained by hydrolysis of 3-mercaptopropyl-trimethoxysilane (MPTS) and tetramethoxysilane, and followed by age; while in the chemical bonding method, a capillary is chemically bonded directly with MPTS. Then, the both resulting capillaries are oxidized with an aqueous solution of hydrogen peroxide solution (H2O2)(30%(m/m)) to obtain the sulfonated capillaries. The electroosmotic flow (EOF) for the sulfonated capillaries is found to remain almost constant within the studied pH range, and be greater than that of the uncoated capillary. However, the coating efficiency of the capillary prepared by chemical bonding method is higher than that by sol-gel method, by comparing their magnitude of the EOF, the degree of disguise of the silanol and reproducibility of prepar...