Abstract. A highly efficient cross-linked polyacrylamide capillary coating has been developed for capillary electrophoresis of proteins. The fused silica capillary tubing was pretreated with 7-oct-1-enyltrimethoxysilane and then statically coated with the polymerization reagents. The copolymerization reaction was performed at 120°C when using a free-radical initiator. Coated columns were evaluated for the separation of both basic and acidic proteins. Methylene bisacrylamide was added in the preparation of the cross-linked polyacrylamide coating, and the cross-linking effects on column performance were evaluated. Both linear and cross-linked columns gave high separation efficiencies and good reproducibilities for proteins, and electroosmotic flow was eliminated. It was found that the cross-linked polyacrylamide coatings produced nearly double the efficiencies and only one third the relative standard deviations in migration times for proteins when compared to linear polyacrylamide coatings. Highly efficient and reproducible separations of proteins in human serum samples were achieved using the cross-linked column.

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Abstract.A procedure for bonding polyethylene glycol (PEG) and polyethylene imine (PEI) onto the capillary surface through a highly crosslinked polysiloxane layer containing epoxy groups has been developed. Systematic variation of the coatings can be used to (a) allow separations over a pH range of 3 to 9, (b) provide for adjustment of electro-osmotic flow, and (c) reduce the adsorption of peptides and proteins. The variation of electroosmotic flow on these coated columns at different operational conditions can be explained using electrical double layer theory. Separations of substituted aromatic compounds and peptides on these coated columns were much improved over similar separations on untreated columns. The results indicate that PEI coated columns are suitable for the separation of basic proteins and PEG coated columns are suitable for acidic proteins. Separations of simple oligonucleotides which differ by only one base were also achieved.

Abstract. In this paper, polymeric hollow fibers prepared from polypropylene and polybutylene terephthalate were used as CE columns. Surface modifications with polyacrylamide greatly improved the performance of the capillaries. Separations of substituted pyridines, model proteins and standard ribonucleotides were demonstrated. The column efficiency for model proteins was over 200,000 theoretical plates. Comparisons of electroosmotic flow, UV absorption properties, heat dissipation, and diameter variation between fused silica capillaries and polymeric hollow fibers were made. The practical potential of small diameter polymeric hollow fibers as CE columns was evaluated.

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