Improved CZE capabilities with new dynamic coatings.

Electroosmotic flow (EOF) is one of the fundamental processes affecting both resolution and separation times in capillary zone electrophoresis (CZE). EOF is a function of pH and buffer composition (zeta potential) in bare-silica capillaries at any pH above 3 and runs in the cathodal direction, decreasing the effective separation length for cationic species. On the other hand, the absence of EOF at low pH can significantly increase separation times, particularly for low pl zwitterionic species. This interdependence of pH and EOF limits the ability to design effective separations by capillary zone electrophoresis. The EOTrol family of dynamic coatings (Target Discovery, Inc., Palo Alto, CA, U.S.A.) allows both the magnitude and direction of EOF to be adjusted independently of the buffer composition and pH. Here we report the use of EOTrol in two challenging CZE separations: (1) inorganic cations with small mobility differences, and (2) the rapid separation of organic zwitterions that are only resolvable at low pH.