Large volume sample stacking of positively chargeable analytes in capillary zone electrophoresis without polarity switching: Use of low reversed electroosmotic flow induced by a cationic surfactant at acidic pH

A simple and effective way to improve detection sensitivity of positively c hargeable analytes in capillary zone electrophoresis more than 100-fold is described. Cationic species were made to migrate toward the cathode even un der reversed electroosmotic flow caused by a cationic surfactant by using a low pH run buffer. For the first time, with such a configuration, large vo lume sample stacking of cationic analytes is achieved without a polarity-sw itching step and loss of efficiency. Samples are prepared in water or aqueo us acetonitrile. Aromatic amines and a variety of drugs were concentrated u sing background solutions containing phosphoric acid and cetyltrimethylammo nium bromide. Qualitative and quantitative aspects are also investigated.