Poly(vinyl alcohols) (PVA) of a molecular weight of about 50 000 were applied to the modification of fused silica surfaces for the separation of large charged molecules such as proteins.Basic and acidic proteins could be separated in PVA-modified capillaries at highly optimized and analytically suitable performance with regard to efficiency, zone symmetry, and resolution. PVA can be used in the "dynamic" mode as an additive to the buffer medium or as a water-insoluble "permanent" coating on the fused silica surfaces which can be

Separation of DNA restriction fragments in dilute buffer solutions of network forming polymers such as linear polyacrylamide (PAA), hydroxyethyl cellulose (HEC) and polyvinylalcohol (PVA) in phosphate buffer were investigated. PVA in buffers already became inhomogeneous after a few separations with resultant deterioration of resolution. Hydroxylic polymers, capable of forming suitable networks in buffers, are strongly adsorbed to fused silica surfaces suppressing the electroosmotic flow. These polymers could be applied as surface modifiers in capillaries, filled with buffer media containing other polymers such as PAA. Suppression of the electroosmotic flow by adsorbed HEC at pH 7 was slightly more effective than with PVA but the former coating was less stable due to weaker binding to the fused silica surface. Good separations of restriction fragments could be achieved with solutions of PAA or HEC as separation media after surface pretreatment of fused silica capillaries by either PVA rinsing or coating according to Hjertén.

Abstract. Diffusion coefficients of oligonucleotides have been measured in polyacrylamide gel capillaries without application of an electrical field. A relationship between such diffusion coefficients and molecular size of the oligonucleotides could be achieved. The slower diffusion of larger oligonucleotides cannot explain the high separation efficiencies of capillary gel electrophoretic separations alone. By theoretical considerations it became obvious that diffusion coefficients of oligonucleotide molecules and also their intermolecular interaction with the polyacrylamide gel may be considerably changed by application of electrical fields.