Capillary electrophoresis separation of neutral organic compounds, pharmaceutical drugs, proteins and peptides, enantiomers and anions

摘要

Addition of a novel anionic surfactant, namely lauryl polyoxyethylene sulfate, to an aqueous-acetonitrile electrolyte makes it possible to separate nonionic organic compounds by capillary electrophoresis. Separation is based on differences in the association between analytes and the surfactant. Highly hydrophobic compounds such as polyaromatic hydrocarbons are well separated by this new surfactant. Migration times of analytes can be readily changed over an unusually large range by varying the additive concentration and the proportion of acetonitrile in the electrolyte. Several examples are given, including the separation of four methylbenz (a) anthracene isomers and the separation of normal and deuterated acetophenone;The effect of adding this new surfactant to the acidic electrolyte was also investigated. Working at acidic condition at pH 2.4 has the advantage that electroosmotic flow is virtually eliminated. Neutral compounds are dragged by their association with the surfactant, moving as the same direction as the surfactant, resulting in fast separations. Basic compounds are also investigated under the same conditions. Excellent resolution of a mixture of 19 polyaromatic hydrocarbons was obtained in only 20 min;Incorporation of cetyltrimethylammonium bromide in the electrolyte is shown to dynamically coat the capillary and reverse electroosmotic flow. The coating prevents basic proteins and peptides adsorption into the capillary wall, resulting in high separation efficiencies. A systematic study of experimental parameters demonstrated the importance of selecting a suitable buffer and an appropriate pH;Chiral recognition mechanism is studied using several novel synthetic surfactants as chiral selectors, which are made from amino acids reacting with alkyl chloroformates. It was found that enantiomeric resolution can be readily manipulated by varying the alkyl groups (different chain lengths), amino acids and surfactant concentrations. Sulfonated [beta]-cyclodextrin is also employed as a chiral selector to compare chiral selectivity with these synthetic surfactants. A duo-chiral selectors system is further investigated for the possibility of eliminating some tedious steps in chiral compounds method development;A satisfactory separation of both inorganic and organic anions is obtained using electrolyte solutions as high as 5 M sodium chloride using direct photometric detection. The temperature inside the capillary that resulted from Joule heating is calculated, and used to explain the unexpected fast and efficient separations. Since electroosmotic flow is suppressed, a quaternary ammonium additive (Q+), which is normally used to reverse the electroosmotic flow in anion separations, is not utilized in our study. The effect of various salts on electrophoretic and electroosmotic mobility is further discussed. Several examples are given under high-salt conditions.