Separation and simultaneous determination of water-soluble and fat-soluble vitamins by electrokinetic capillary chromatography

A comparative study of different surfactants, such as sodium dodecyl sulfate and bis(2-ethylhexyl) sodium sulfosuccinate (AOT), as pseudostationary phases was conducted in order to find the best conditions for the separation of the water- and fat-soluble vitamins by electrokinetic capillary chromatography. Separation was accomplished with AOT in a water–acetonitrile solution in the presence of boric acid–sodium borate buffer. A study of different variables was performed in order to obtain the best resolution and quantification of the vitamins: the variables explored were the pH and concentration of the buffer used, the percentage of acetonitrile, the concentration of surfactant and the applied voltage. Calibration curves and precision data were obtained for each analyte. Finally, a method to analyze these substances in pharmaceutical preparations is proposed.