The separation of proteins and other charged compounds via capillary electrophoresis can be challenging due to their adsorption to the fused-silica capillary. This can result in peak tailing, possible loss of resolution, and even irreproducible electroosmotic flows (EOF). Several techniques exist for surface modifications to prevent these effects, such as buffer additives, dynamic and semipermanent coatings, as well as covalent modification of the silica surface. This work explores the direct fluorination of the capillary wall, to prevent analyte adsorption while also modifying the magnitude of the EOF. Though fluoride solutions (e.g. HF) are typically used to etch glass and not to modify the silica surface, recent work has shown that at low enough concentrations it is possible to form surface SI-F bonds. The replacement of a hydroxyl group by fluorine alters the EOF by removing the anionic charge. This may also limit the available locations for cationic molecules to electrostatically adsorb to the silica surface.<br/><br/>To test this method's effectiveness we have explored how exposing the capillary to various fluoride containing solutions cause a reduction in the EOF. With optimized derivitization of the silica surface we have seen diminishing of peak asymmetry, and decreased peak broadening for cationic analytes. The longevity of a single derivitization is also examined under a range of buffer pH values. Our work demonstrates that fluoride can be a quick, simple coating to prevent analyte adsorption while also resulting in minimal modification of the native EOF.<br/>

Direct fluorination of fused silica capillary surfaces

251st National Meeting (2016)

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