| Vitamins are a broad group of organic compounds that are minor, but essential, constituents of food required for the normal growth, self-maintenance and functioning of human and animal bodies. These compounds can be classified in two main groups: water- and fat-soluble vitamins. Microemulsion electrokinetic chromatography (MEEKC) is an electrodriven separation technique. The target of the present work was to separate water- and fat-soluble vitamins simultaneously by MEEKC within a short time. The thesis mainly includes the following four parts.1. The analytical methods for determination of vitamins were reviewed in this part, and the advantage and disadvantage of these diferent analytical methods was discussed. The principle, the important factors and the applications of MEEKC in various fields were also summarized, especially, the applications in analysis of vitamins, pharmaecutical, natural products and environmental analysis.2. Based on the common SDS microemulsion system used in MEEKC, the novel microemulsion systems were studied to shorten analysis time for fat-soluble analytes. Since Low SDS concentration could speed migration of the analytes due to decrease of backward electrophoretic mobility of microemulsion droplet and increase of electroosmotic flow (EOF), it is the key to lower SDS concentration, as well as to ensure the stability of microemulsion systems. In this part, two schemes were applied to solve the difficulty. Non-ionic surfactant, together with SDS constituted mixed surfactants used in microemulsion to low SDS content. On the other hand, a lot of 1-butanol was added to help reduce the tension between two layer of oil and water, stabilize the microemulsion system. Experimental results showed these two methods could shorten the analysis time, and the latter has more separation efficiency. Therefore, the novel microemulsion has potential to solve two difficulties of long migration time and poor resolution.3. The novel microelusion system was applied to rapid determine fat-soluble vitamins A, D3, and E with MEEKC. The microemulsion consisted of 1.2% (W/W) SDS, 21% (V/V) 1-butanol, 18%(V/V) acetonitrile, 0.8% (W/W) n-hexane and 20 mM borax buffer ( pH 8.4). The three analytes were baseline separated within 13 min at 25 kV and 25℃. The RSD values (n= 5) of migration time and peak area of the analytes were less than 2.5% and 4.5%, showing high reproducibility. Good linear relations between peak areas and concentrations of analytes were established in the range of 20-1000μg /mL for vitamin A, 5-1000μg /mL for vitamin D3, and 5-1000μg /mL for vitamin E. The detection limits (S/N=3) were 12μg/mL, 0.72μg/mL, 0.29μg/mL respectively. This method has been successfully applied for analysis commercial vitamin capsules, the determination results were accorded with the declared in the label.4. A rapid, reliable and reproducible method based on MEEKC for simultaneous determination of thirteen kinds of water- and fat-soluble vitamins has been developed in this work. The novel microemulsion system consisting of 1.2% (W/W) SDS, 21% (V/V) 1-butanol, 18% (V/V) acetonitrile, 0.8% (W/W) n-hexane, 20 mM borax buffer (pH 8.7) was applied to improve selectivity and efficiency, as well as shorten analysis time. Acetonitrile as the organic solvent modifier, pH of the running buffer and 1-butanol as the cosurfactant played the most important roles for separation of the fat-soluble vitamins, water-soluble vitamins and stabilization of system, respectively. The 13 water- and fat-soluble vitamins were baseline separated within 30 min. The system was applied to determine of water- and fat-soluble vitamins in commercial multivitamin pharmaceutical formulation, good accuracy and precision were obtained with recoveries between 97% and 105%, acceptable quantitative results corresponding to label claim except vitamin C.
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