Determination Of Dissociation Constants By Capillary Electrophoresis Zone

Several methods of determination dissociation constant in capillary electrophoresis zone (CZE) were studied in this paper. The dissertation has 4 chapters and the main contents are as following:In chapter 1:This chapter introduced the methods for pKa measurement. The conventional methods of pKa determination included potentiometric titration, spectrophotometric, chromatography, etc. Capillary zone electrophoresis was mostly introduced in this chapter. The main steps such as electroosmosis flow measurement and shortening analysis time were detailed described.In chapter 2:Organic compounds have been used as EOF marker in many studies of determination dissociation constants. Although the amount of organic compounds is little, it can bring environmental pollution, and the neutral marker may react with some substance of sample solutions. Moreover, the appropriate neutral marker is hard to choose for analyzing the complex matter. Therefore, this chapter studied how to utilize the abrupt change of current which is ignored by people to measure the dissociation constants (pKa) of nitrophenols without using neutral marker. The determination values were 7.10,7.22,8.36, and the reference data were 7.15,7.22, 8.36, there was a good agreement between determined (pKa) values and reference data. This method has some advantages, such as no need adding extra equipments and reagents, reproducibility increased, environmental pollution reduced, and so on.In chapter 3:The effect of pressure on determination of pKa was studied. A comparative study of determination pKa values of quinolones by pressure-assisted capillary in aqueous and in different proportion hydro-organic media was investigated. And the scope of applying pressure was also discussed. The difference between determined pKa values with reference data was not exceeding 0.3. The experimental results indicated that the pressure-assisted capillary electrophoresis is suitable for determination the dissociation constants in water and in methanol-water media. The application of pressure not only reduces migration times, but also improves the repeatability of effective mobility measurements. However, the observed effective mobility shift by the applied pressure did not significantly affect the determined pKa values.In chapter 4:The effect of pKa values on segregation analysis of quinolones was investigated. The PeakMaster software was used as analysis instrument to simulate different experimental conditions. The predicted optimal pH at 8.0, and the buffer concentration is 25mmol/L. The experiment indicated that the predicted optimal conditions fitted well with the actual situation. The predicted results with PeakMaster software can be used as reference, and accordingly simplify experimental procedure.