Use of coated capillaries for nonaqueous capillary electrophoresis

Abstract

The performance and stability of different hydrophilic capillary coatings have been examined using nonaqueous electrolytes. Coated capillaries can be successfully applied to nonaqueous capillary electrophoresis (CE) separations as well as in the normal aqueous mode. Capillaries coated with polyethylene glycol (PEG) and polyvinyl alcohol (PVA) show high stability toward a large number of methanol rinsing steps. The stability of PVA-coated capillaries in a long series of separations performed in methanol was superior to that of the PEG capillaries. The electroosmotic flow (EOF) characteristics of PVA, PEG, and uncoated fused silica capillaries have been examined using methanolic electrolytes. In PVA-coated capillaries the EOF was strongly reduced with aqueous and nonaqueous electrolytes. Surprisingly the EOF of PEG-coated capillaries in methanolic electrolytes was found to be anodic, whereas a reduced cathodic EOF is observed in aqueous systems as expected. The selectivity for the separation of weak electrolytes using nonaqueous media was influenced by the addition of acids or bases. ©1999 John Wiley & Sons, Inc. J Micro Sep 11: 209–213, 1999