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

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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.

SummaryMixtures of several basic proteins have been used to test CZE capillaries with surfaces modified by new pretreatment procedures; the performance obtained has been compared with that achieved using capillaries treated by procedures described in the literature.It has been shown that addition of non-ionic polyvinylalcohols (PVA) to CZE buffer solutions deactivates even bare, be. untreated, fused silica surfaces and renders them suitable for separations of basic proteins. The performance obtained from such surfaces was comparable with that of capillaries modified by the more elaborate procedures of etching, silanol derivatization, and/or adsorptive coating (again with polymers).A home-made device is described which enables derivatization and coating reactions to be performed on fused silica capillaries under an inert atmosphere, be. one free from oxygen and water.

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