Synthesis, characterization and application of polymeric surfactants in micellar electrokinetic chromatography: use of ionic liquids as modifiers

Abstract

The goal of the research presented in this dissertation is to synthesize, characterize, and apply a novel chiral amino acid-based surfactant and achiral sulfate-based surfactants for the effective separations of chiral and achiral compounds in micellar electrokinetic chromatography (MEKC). The first part of this research involves novel synthesis, characterization, and application of polysodium oleyl-L-leucyl-valinate (poly-L-SOLV) for the separation of chiral compounds in MEKC. Surface tensiometry, proton nuclear magnetic resonance, infrared spectroscopy, densitometry and analytical ultracentrifugation were used as the characterization techniques. Optimal MEKC separating conditions were established by varying surfactant concentration, buffer concentration and pH, applied voltage, and capillary temperature. Poly-L-SOLV was used successfully in the separation of various enantiomers of neutral, acidic, and basic analytes. The second part of this research focuses on the synthesis, characterization, and application of poly sodium undecylenic sulfate (poly-SUS) for the separation of achiral compounds. The use of ionic liquids (ILs) as modifiers in the separation of achiral and chiral analytes in MEKC was also investigated. In this study, polymeric surfactants and ILs were added to a low-conducting buffer solution. Also, select ILs were compared with select organic solvents as modifiers for the separation of chiral compounds in MEKC. The results indicated that ILs could stabilize the current and at the same time lead to faster and better separations. Finally, another surfactant, sodium dodecyl sulfate (SDS), was used to develop a method for the separation of 2-pyrrolidone, vinylacetate, and N-vinyl-2-pyrrolidone monomer residues in polyvinylpyrrolidone (PVP) homo-polymer and polyvinylpyrrolidone/vinyl acetate (PVP/VA) copolymer in MEKC. A capillary electrophoresis (CE) high-sensitivity cell was used for these separations because the conventional CE cell could not achieve the required sensitivity. The method developed was then evaluated for quantitative analysis of the monomer residues from the polymer samples. Although the method was not versatile for the quantitative analysis of the three monomer residues, it was robust, fast, and economical for the separation of these monomer residues.