グラジエントミセル動電クロマトグラフィー

抄録

A Surfactant gradient method was developed for miceller electrokinetic chromatography (MEKC). In the present method, electroosmotic flow was suppressed almost completely and thus, micelles in a running solution of the inlet vial were introduced in turn into the capillary during operations. Under such situations, we can perform surfactant gradient MEKC separations only by changing the composition of surfactants in the inlet vial during a single run. Here, we represented MEKC separations of unsubstituted benzoate and nine substituted benzoates as model organic anions using mixed systems of CTAC as a cationic surfactant and Tween 20 or Brij 35 as non-ionic surfactants possessing polyoxyethylene chains (POE-NSs). In a pure CTAC system, the synergistic influences of attractive electrostatic and hydrophobic interactions gave rise to quite large retention factors of many of the benzoate anions, resulting in their co-elution. Addition of an adequate amount of the POE-NSs to the pure CTAC system decreased the electrostatic interaction significantly to give remarkably improved separation of the analytes, but long analysis time was required. Surfactant gradient methods decreasing the concentration of POE-NSs in the mixed systems were useful to decrease analysis time and to improve separation simultaneously in both stepwise manners and continuous manners. The fundamentals of the present method were discussed in detail. We also mentioned its availability as a platform to construct highly functional separation systems.