CZE separations of basic proteins at low pH in fused silica capillaries with surfaces modified by silane derivatization and/or adsorption of polar polymers

Abstract

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.

Capillary electrophoresis of peptides and proteins in fused‐silica capillaries coated with derivatized polystyrene nanoparticles

“…Therefore, all washing and coating steps were performed with a fused-silica capillary mounted in a commercial CE instrument, although longer pieces of fused-silica capillaries were pretreated and coated with an apparatus similar to that described by Gilges et al [17]. First, the fused-silica capillary was rinsed with tetrahydrofuran to remove organic impurities and then with 1 M sodium hydroxide to remove inorganic impurities and to hydrolyze the siloxane bonds at the silica surface to silanols.…”

“…Adsorption of the analytes is undesirable in capillary electrophoresis because it results in peak dispersion and peak asymmetry; several mathematical models have been elaborated to quantitate the consequences of this chromatographic effect in capillary electrophoresis [5][6][7][8][9]. The various experimental attempts to prevent protein-wall interactions can be classified into four categories [lo]: (i) use of buffers of extreme pH [4] or high ionic strength [3], and utilization of buffer additives such as zwitterions [ll], amines [12], or surfactants [ 131; (ii) traditional silane coupling chemistry [14-161; (iii) physical adsorption of polymers, e. g. polyvinylalcoho1 [17], polyethyleneimine [18,191, nonionic surfactants [20], cellulose acetate [21] or hexadimethrin bromide [22], onto the capillary surface; and (iv) chemically bonding a polymer to the capillary wall, which is the most frequently applied strategy to eliminate adsorption sites [23]. Some of the more prominent examples of immobilized polymers are polyacrylamide [24-261, polyoxyethylene [27, 281, polyethyleneimine [29], polysaccharides [30], and polyvinylalcohol [3 13.…”

“…Number of theoretical plates (m-') Coatings with polyhydroxyl polymers have been demonstrated to be effective in suppressing protein-fused silica interactions [16,17,27,31, 381 because the formation of hydrogen bridges between the surface silanols and the hydroxyls of the polymer may be strongly involved in the suppression of electrostatic interactions of silanols with charged solutes. Electrostatic interactions are also prevented by the relatively long chains of the polymeric coatings that are believed to sterically hinder the access of macromolecules to the charged silica surface.…”

Cellulose acetate-coated fused-silica capillaries for the separation of proteins by capillary zone electrophoresis

“…Four different approaches have been reported and involve, briefly, (i) elimination of the interaction by adjusting the pH of the buffer to such a value that the silanol groups are non-charged [1]; (ii) adjusting the pH of the buffer of such a value that the charges of the silanol groups and protein have the same sign [2,3]; (iii) dynamic modification of the surface by neutral and cationic additives in the buffer [4][5][6][7][8][9]; and (iv) chemical modification using covalent bonding of the fusedsilica surface [10][11][12][13][14][15][16][17][18].…”

Surface treatment and characterization: Perspectives to electrophoresis and lab‐on‐chips

“…In spite of this difficulty, several matrices with dynamic coating properties have been successfully proposed. Dynamic coating effects during CE in fusedsilica capillaries were indeed recognized and used rather early on [147][148][149][150][151], but only became popular with the discovery of the very good properties of poly(N,N-dimethyl acrylamide) (PDMA) by Madabhushi [152,153]. PDMA-based matrices are still used (e.g.…”