Micellar Electrokinetic Chromatographic Separation of Basic Polypeptides with Equal Mass to Charge Ratio Using Dynamically Modified Silica Capillaries

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Abstract
A method using 3-(N, N-dimethylhexadecylammonium) propanesul-fonate (PAPS) as an additive to the buffer for performing micellar electrokinetic chromatography in dynamically modified silica capillaries has been developed. PAPS is a zwitterionic surfactant. The advantage of zwitterions is that they do not increase the conductivity of the buffer. Therefore these surfactants can be added to the buffer at high concentrations while still allowing the application of high voltages and the use of capillaries of larger internal diameter. The separation mechanisms involved in CE with PAPS were investigated and found to be a combination of electrophoresis and hydrophobic interactions. The critical micelle concentration of PAPS was determined to be 25 μM. Above this concentration, an increase in electroosmotic flow due to dynamic surface modification was observed. High-efficiency separations of basic polypeptides with equal or nearly equal mass to charge ratios have been achieved using PAPS as an additive to the running buffer. The influence of pH on the separation has been examined.