Excellent separations of nonionic organic compounds were obtained by adding sodium dioctyl sulfosuccinate (DOSS) to an acetonitrile (~40% v/v)-water electrolyte. Separation is based on differences in the strength of analyte-DOSS association "complexes" in solution, which results in differences in effective electrophoretic mobility. Micelle formation is not believed to occur. The effects of varying apparent pH, applied voltage, acetonitrile concentration, and DOSS concentration were studied with regard to electroosmotic mobility and effective electrophoretic mobility. Under optimum conditions, excellent separations of 23 organic compounds were obtained.Capillary electrophoresis (CE) of nonionic analytes cannot be performed in a free solution due to lack of electric charges of analytes. This problem can be solved by using an additive to form a pseudophase. In micellar electrokinetic capillary chromatography (MECC), which was introduced by Terabe,12 micelles are used as a pseudophase. MECC separations are based on different
SummaryVery good separations of non-ionic organic compounds have been achieved by capillary zone electrophoresis (CZE) using a tetraheptylammonium salt as an additive in aqueous acetonitrile as solvent. A systematic study was undertaken to determine the effect of experimental parameters on electroosmotic mobility and electrophoretic mobility. It was found that pH, acetonitrile concentration, and the type and concentration of quaternary ammonium salt are important experimental variables. Under appropriate conditions, the separation window was enlarged and a broad range of electrically neutral organics, including very hydrophobic compounds (e.g. polycyclic aromatic hydrocarbons) and fairly hydrophilic compounds were separated in a relatively short time. By adjusting the separation conditions, high resolution CZE of a specific group of neutral organic compounds could be achieved. A method for calculation of capacity factor was proposed and capacity factors for a variety of non-ionic organic compounds were calculated.
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