The effect of the three different surfactants, sodium dodecyl sulfate (SDS), diethylhexyl sodium sulfosuccinate (AOT), and taurodexycholic acid sodium salt (STDC) on the nonaqueous capillary electrophoretic separations of hydrophobic compounds were compared with formamide containing 20 mM K2HPO4 as electrolyte solvent. Separations of all selected uncharged hydrophobic compounds, e.g., p-arylacetophones were shown to be strongly dependent on the kind of surfactant. The electrolyte containing 180 mM SDS provided the best result for the selected samples.

SummaryUsing an organic solvent and a surfactant, the uncharged, hydrophobic p-arylacetophenones have been separated by micellar electrokinetic chromatography. As an example, the effect of formamide containing sodium n-dodecyl sulfate (SDS) on the separation has been studied. Separations of all selected uncharged hydrophobic compounds were shown to be strongly dependent on the concentration of surfactant. It is suggested that if there is no micelle formed in the formamide solvent, the uncharged hydrophobic compound cannot be separated even though in the presence of surfactant. The electro-migration of solutes was considered zero. After micelle formation, the uncharged compounds were partitioned between the micellar and the organic solvent phases. Neutral molecule partition in and out ofmicelles depends on the hydrophobicity of each analyte. Based on this suggestion the critical micelle concentrations of SDS, di-(ethylhexyl) sodium sulfosuccinate (AOT) and taurodexycholic acid sodium salt (STDC) in formamide were determined.

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A simple surface plasmon resonance (SPR) experimental set-up has been made for investigating further applications of the SPR detection method in analytical chemistry. In the home-made SPR experimental set-up, a Ag film with a thickness about 50 nm was deposited on the flat surface of a hemicyclindrical prism, and a flow cell was attached directly to the flat surface of the prism. It has been confirmed that SPR occurred in the experimental setup using model samples of water and alcohols. The SPR detection modes, based on changes in the coupling angle and reflectivity at a fixed angle, were investigated both theoretically and experimentally. It has been shown that the SPR detection mode based on the reflectivity change is much more sensitive than that based on a change in the coupling angle, for the SPR experimental set-up. A preliminary investigation indicates that the SPR method can be used as a universal detector for HPLC or FIA or other analytical methods. Its problems, improvements, and future applications in analytical chemistry are also discussed.

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