Synthesis, characterization, and applications of novel pseudostationary phases in micellar capillary electrophoresis for separation of chiral and archiral compounds h[electronic resource

Abstract

The research presented in this dissertation involves the synthesis, characterization, and the use of novel surfactants, including both micelles and vesicles, as pseudostationary phases in micellar capillary electrophoresis (MCE) for the separation of achiral and chiral compounds. Separation of environmental pollutants such as 2 to 6-ring polycyclic aromatic hydrocarbons (PAHs) was achieved using poly(sodium undecylenic sulfate). A baseline separation of all 16 PAHs was possible for the first time in MCE by a single-surfactant system. In addition, a surfactant with a phosphated head group, i.e., di(2-ethylhexyl)phosphate (DEHP), was also introduced as a novel pseudostationary phase for separation of 21 weakly and strongly hydrophobic neutral compounds. Acetonitrile at a concentration of 30% (v/v) in combination with 100 mM DEHP gave optimum separation for a mixture of 21 benzene derivatives and PAHs in under 16 minutes. An application of cyclodextrin modified MCE was used for separation of twelve mono-methylbenz[a]anthracene positional isomers using a combination of poly-SUS and b-CD, g-CD or b-CD derivatives. Tartaric acid based vesicular surfactants were synthesized and utilized as novel pseudostationary phases in MCE. Linear solvation energy relationship model was applied to understand the fundamental nature of the solute-surfactant interactions and to investigate the effect of the type and the composition of pseudostationary phases on the retention mechanism and selectivity in MCE. The solute size has the largest influence on the solute retention in MCE. The hydrogen bond accepting ability of the solute is the second most important factor on retention and is the largest contributor towards the selectivity differences between pseudostationary phases used. Another study conducted was the synthesis of sodium N-undecanoyl L-leucinate and co-polymerization of SUL with SUS to make a variety of co-polymerized molecular micelles having both chiral (leucinate) and achiral (sulfate) head groups. These surfactants were applied as novel pseudostationary phases in MCE for separation of chiral and achiral compounds. Aggregation numbers and partial specific volumes of these surfactant systems were determined using fluorescence spectroscopy and densitometry, respectively. Thermodynamic parameters such as enthalpy, entropy, and Gibbs free energy changes upon transfer of analyte(s) from aqueous phase to the pseudostationary phase were also determined.