Separation Of Non-ionic Compounds By Non-aqueous Capillary Electrophoresis

Non-aqueous capillary electrophoresis, as a new branch of capillary electrophoresis, witnesses great development in recent years. Because of the different physiochemical properties of non-aqueous solvents, the interaction between molecules or ions is much difference with aqueous media. Usually, the electrostatic interaction becomes stronger, while solvophobic interaction weaker. That difference can be used to improve the selectivity of separation. In this thesis, through electrostatic interaction and solvophobic interaction of additive-analyte, the separation of non-ionic compounds was demonstrated. This thesis mainly includes two parts. In the first part, the separation of phenol and aniline compounds using electrostatic interaction of addictive-analyte was studied. This part consists of Chapter 2, 3, and 4. In chapter 2, the separation of three derivatives of naphthalin, i.e. α-naphthylamine, α-naphthol and β-naphthol, was studied using cetyltrimethyl ammonium bromide, CTAB as additive in methanol/acentonitrile media. The mechanism of separation, and the effect of concentration of CTAB, composition of solvent and the characteristic of CTAB were discussed. And analytical grade reagent, β-naphthol, was analyzed by non-aqueous capillary electrophoresis. In chapter 3, the separation of non-ionic phenols was studied in acentonitrile based on electrostatic interaction using short chain tetra-alkyl ammonium bromide as additive. The research reveals that acentonitrile is a kind of appropriate solvent for electrostatic interaction. The separation using tetra-alkyl ammonium bromide with different alkyl suggested tetra-alkyl ammonium bromide with shorter alkyl chain might have higher separation efficiency. The addition of water and methanol into running solution deteriorates the separation. The study reveals that the structures of phenols have great influence on the strength of electrostatic interaction of phenol-Br-. Through analysis of phenols'structure, we can predict the result of separation primarily. In chapter 4, the separation of anilines, including m-nitroaniline, o-nitroaniline, p-nitroaniline, p-toluidine, aniline, benzidine and o-phenylenediamine, using tetra-ethyl ammonium bromide, TEAB as additive in acentonitrile based on the electrostatic interaction of additive-analyte was studied by non-aqueous capillary electrophoresis. The influence of water and methanol in running solution on the separation was investigated. The research on the mechanism of the interaction revealed that it is the amino group that interacts with the bromide anion. In the second part, Chapter 5, the separation of dialkyl phthalates by non-aqueous micellar electrokinetic chromatography (NAMEKC) in formamide media based on solvophobic interaction was investigated. The separation of three kinds of priority pollutions by U.S. Environmental Protection Agency (EPA), i.e. dimethyl phthalate, diethyl phthalate and dibutyl phthalate, was realized in 15 min using sodium dodecyl sulfate, SDS micelle as pseudo-stationary phase in formamide under optimized conditions. The study suggested that NAMEKC has great potential in the separation of hydrophobic compounds.