Characterizations of polymer/surfactant and aliphatic alcohol/surfactant micellar electrokinetic chromatography systems

Characterizations are performed on polymeric, surfactant, mixed polymeric/surfactant, and modified surfactant pseudo-stationary phases used in Micellar Electrokinetic Chromatography (MEKC) systems.; The polymer Elvacite 2669 is a triblock co-polymer, poly (methyl methacrylate/ethyl acrylate/methacrylic acid), that can be used as a MEKC pseudo-stationary phase. This polymer was mixed with an anionic surfactant, sodium dodecyl sulphate (SDS) and characterized using various analytical techniques. The interactions between these two phases were investigated using surface tension, conductance, and spectroscopic measurements. The mixed pseudo-stationary phase was also characterized using Linear Solvation Energy Relationships (LSER).; The anionic surfactant, SDS, is a popular pseudo-stationary phase used in MEKC. Characterizations of this pseudo-stationary phase after modification with aliphatic alcohols were performed using LSER. A homologous series of eight linear alcohols were grouped into short, intermediate, and long chain lengths. The changes in properties of the modified phases within each group were examined as the alcohol chain length was increased. The largest changes occurred with the dipolarity, polarizability and hydrogen bonding properties. The dipolarity and hydrogen bond donating ability of the phase decreased as the chain length increased. The polarizability and hydrogen bond accepting ability increased as the chain length increased. The largest changes in these properties occurred with the intermediate chain length alcohols. Co-micellization or the incorporation of alcohols in the SDS micelle can explain the changes in these LSER properties. As alcohols are added to SDS, water in the palisade and stem layers of the micelle is modified so that the micelle is less hydrated. Thus changing the micelle dipolarity and hydrogen bonding properties. Hexanol caused the largest changes in micellar properties and thus in solute selectivity. Addition of short chain length alcohols, methanol and ethanol, cause only small changes in the micelle, even though they were added at large concentrations. They mostly modify the bulk aqueous phase. The addition of long chain alcohols show small changes in LSER properties but this is because of their limited solubility in these micellar phases.