SOL-GEL CHEMISTRY-BASED UCON-COATED COLUMNS FOR CAPILLARY ELECTROPHORESIS

A sol-gel chemistry-based novel approach for the preparation of a Ucon -coated fused-silica capillary column in capillary electrophoresis is presented. In this approach the sol-gel process is carried out inside 25 mu m I.D. fused-silica capillaries. The sol solution contained appr opriate quantities of an alkoxide-based sol-gel precursor, a polymeric coating material (Ucon), a crosslinking reagent, a surface derivatizi ng reagent, controlled amounts of water and a catalyst dissolved in a suitable solvent system. The coating procedure involves filling a capi llary with the sol solution and allowing the sol-gel process to procee d for an optimum period. Hydrolysis of the alkoxide precursor and poly condensation of the hydrolyzed products with the surface silanol group s and the hydroxy-terminated Ucon molecules lead to the formation of a surface-bonded sol-gel coating on the inner walls of the capillary. T he thickness of the coated film can be controlled by varying the react ion time, coating solution composition and experimental conditions. Co mmercial availability of high purity sol-gel precursors (e.g., TEOS 99 .999%), the ease of coating, run-to-run and column-to-column reproduci bility, and long column lifetimes make sol-gel coating chemistry very much suitable for being applied in analytical microseparations column technology. Test samples of basic proteins and nucleotides were used t o evaluate the column performance. These results show that the sol-gel coating scheme has allowed for the generation of bio-compatible surfa ces characterized by high separation efficiencies in CE. For different types of solutes, the sol-gel coated Ucon column consistently provide d migration time R.S.D. values of the order of 0.5%. (C) 1997 Elsevier Science B.V.