| Summary: | 博士 === 國立臺灣大學 === 化學研究所 === 87 === Abstract
The influence of buffer pH on the migration behavior and separation of isomeric trichloro-phenols (TCPs) was systematically investigated using capillary zone electrophoresis. Complete separation of isomeric trichlorophenols was achieved with a phosphate-borate buffer in the pH range 5.8~8.0 at 10 kV. The present results confirm that the optimum pH condition is indicated by the change in the shape of curves from concave to convex in the plots of electrophoretic mobilities of trichlorophenols at some given pH (roughly in the range pKa±2)versus the pKa value of each corresponding isomer. At this optimum pH, electrophoretic mobility of isomeric trichlorophenols correlates linearly with their pKa values. The similarity of such correlations in different pH ranges for trichlorophenols and dichlorophenols illustrates the dependence of the electrophoretic mobility of a chlorophenol isomer on both pKa and the molecular size. The pKa values of five isomeric trichlorophenols are reported.
The migration behavior and separation of various s-triazines, including five chloro-, three methoxy- and five alkylthio-s-triazines, were investigated in micellar electrokinetic chromatography (MEKC) using a cationic surfactant. In this study, tetradecyltrimethyl ammonium bromide (TTAB) was selected as a cationic surfactant. The results indicate that the selectivity of neutral species of s-triazines in each class is not significantly influenced by buffer pH and micelle concentration, but the overall selectivity is considerably affected by these two separation parameters when charged solutes are present, particularly, at buffer pH below 5.0. Complete separation of thirteen s-triazines was optimally achieved within six minutes on addition of TTAB (15 mM) to a phosphate buffer (70 mM) at pH 4.75 or 3.8. Based on a model that describes the relationship of the effective electrophoretic mobility of a neutral solute and micelle concentration in MEKC, the migration behavior of chloro-s-triazines at pH 6.0 is predicted and the binding constants of s-triazines to TTAB micelles are evaluated. The correlation between the binding constants and Pow (the partition coefficient of a solute between 1-octanol and water) reveals that the migration order of s-triazines in each class is primarily determined by the hydrophobicity of the solutes.
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