A New Separation Mode for Non-aqueous Capillary Electrophoresis Using Excess Adsorption of Cationic Species Electrolytes

Non-aqueous capillary electrophoresis (NACE) has been developed as a powerful analytical method for a group of compounds having both a weak charge and high hydrophobicity, including pharmaceuticals. NACE is possible to apply a high voltage because of the low current value, compared to the commonly used aqueous system, which enables to shorten the analysis time. In addition, an improvement in the detection sensitivity can be attainable by sample stacking using an increased concentration of electrolytes. Hitherto, NACE has been limited to use as an alternative to aqueous capillary electrophoresis method, such as suppression of the current value, improving of the solubility of a hydrophobic compound, and adjusting the electroosmotic flow. In the process of searching for new analysis conditions for NACE, we found that the electroosmotic flow is reversed from the cathode to the anode by using boric acid/potassium borate with 1-propanol buffer solution. This phenomenon mainly occurs specifically in a solvent system containing 1-propanol, and the speed can be controlled by the mixing ratio of the solvents. In this study, we examined in detail the effect of the buffer composition for EOF direction and separation, and developed a new analysis method.