Methods development for separation of inorganic anions, organic acids and bases, and neutral organic compounds by ion chromatography and capillary electrophoresis

Li, Jie
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A new polymeric anion-exchange resin with triamine functional groups was prepared, and its performance for separating common inorganic anions was studied in detail. Small ionic additives, such as ethanesulfonic acid and protonated triethylamine, were proven to be effective in improving the separation of substituted anilines by capillary electrophoresis. Compared with additives of larger molecules, such as surfactants and polymers, these small additives appears to form thin layer of coatings on the silica capillary surface, thus are easier to remove. Nonaqueous capillary electrophoretic method was developed for separation of nonionic organic compounds with methanol as separation medium. Depending on their structure, these neutral compounds can move at different apparent velocities by interacting with anionic surfactants to varying degrees. Their apparent mobilities are also affected by the properties of the separation media, including dielectric constant and viscosity. Fast and efficient separations of both organic and inorganic anions were achieved by Ion Chromatography - Capillary Electrophoresis (IC - CE) with a water soluble ion-exchange polymer added to the CE background electrolyte. This technique combines the separation mechanisms of IC and CE, and anions with a variety of structures and mobilities can be well resolved. For example, excellent resolution was achieved for positional isomers of phthalates and tri-benzenecarboxylates. And 17 inorganic and organic anions were separated within 6 min, and no peak distortion was observed for any of these sample ions. The applications of polymer and moderately high concentration of added salts in the background electrolytes also provided very good reproducibility for anion analysis (1.0% RSD for migration time).

Chemistry, Analytical chemistry