Use of coated capillaries for nonaqueous capillary electrophoresis

The performance and stability of different hydrophilic capillary coatings h ave been examined using nonaqueous electrolytes. Coated capillaries can be successfully applied to nonaqueous capillary electrophoresis (CE) separatio ns as well as in the normal aqueous mode. Capillaries coated with polyethyl ene glycol (PEG) and polyvinyl alcohol (PVA) show high stability toward a l arge number of methanol rinsing steps. The stability of PVA-coated capillar ies in a long series of separations performed in methanol was superior to t hat of the PEG capillaries. The electroosmotic flow (EOF) characteristics o f PVA, PEG, and uncoated fused silica capillaries have been examined using methanolic electrolytes. In PVA-coated capillaries the EOF was strongly red uced with aqueous and nonaqueous electrolytes. Surprisingly the EOF of PEG- coated capillaries in methanolic electrolytes was found to be anodic, where as a reduced cathodic EOF is observed in aqueous systems as expected. The s electivity for the separation of weak electrolytes using nonaqueous media w as influenced by the addition of acids or bases. (C) 1999 John Wiley & Sons , Inc.