Synthesis and evaluation of epoxy polymer coatings for the analysis of proteins by capillary zone electrophoresis

Abstract

This paper reports a diol-epoxy coating process to deactivate the inner surface of fused-silica capillaries for use in capillary zone electrophoresis. The most effective coating consists of an epoxy polymer covalently bonded to the silica surface through glycerylpropyl silane which eliminates a number of the negatively charged silanol groups. The epoxy polymer phase also further masks residual surface silanols and sterically limits interaction of proteins with the inorganic surface of the capillary. Application of the coating was a multi-step process. In the initial step, glycidylpropyltrimethoxy silane was used to derivatize the surface of fused-silica capillaries. This was followed by deposition at the capillary wall of a film of multifunctional oxirane. Polymerization was achieved by either boron trifluoride or tertiary amine. These coatings were of sufficient thickness and hydrophilicity to reduce protein adsorption but still allow sufficient electroosmotic pumping to carry both positive and negative species past the detector. The coatings provided capillaries with lifetimes exceeding 120 h. Proteins were resolved quickly and efficiently with high recovery of both cationic and anionic species between pH 5 to 10.