Quantitative studies on the adsorption of proteins to the bare silica wall in capillary electrophoresis

Abstract

The efficacy of two classes of surfactants, non-ionic and zwitterionic, in quenching the interaction of proteins with the naked silica wall in capillary electrophoresis, is evaluated. The class of non-ionic detergents is found to be rather inefficient in preventing protein binding to the fused-silica surface, since large amounts (up to 10%) are required for reducing such interactions by 90%. Conversely, zwittergents appear to be much more efficient, since, in the case of sulphobetain SB-16, 90% binding inhibition is achieved at a concentration of surfactant of only 0.3%. In this last case, it is found that the binding inhibition closely follows the values of critical micellar concentrations (CMCs) of the various surfactants, those having the lowest CMC value exhibiting the highest inhibition power. The CMC values also follow a hydrophobicity scale, suggesting that the most hydrophobic zwittergents are the ones that shield more efficiently the silica surface.

A very thin coating for capillary zone electrophoresis of proteins based on a tri(ethylene glycol)‐terminated alkyltrichlorosilane

“…Alkylamines are believed to interact strongly with silanol groups at the capillary surface, modifying the charge at the surface, and potentially reversing EOF [46][47][48][49][50]. Various types of surfactants, including cationic [40,51,52], anionic, zwitterionic [53][54][55], nonionic [54], and fluorosurfactants [56] have been used as buffer additives to suppress adsorption and tune EOF, and can allow separation of both cationic and anionic proteins in a single run. The double-chained cationic surfactant didodecyldimethylammonium bromide (DDAB) [57] and the double-chained, zwitterionic phospholipid 1,2-dilauroylsn-phosphatidylcholine (DLPC, C 12 ) [58] have found utility as semipermanent coatings that remain stable on the capillary surface with no surfactant present in the running buffer.…”

Mechanism of action of quaternary diamino quenchers in capillary zone electrophoresis

“…Soon, a vast body of literature, as reviewed in [9][10][11][12][13][14], appeared on how to control and modulate the electroendoosmotic flow (EOF), in search of ways and means for optimizing separations and minimizing sample interaction with the silica wall. In the case of dynamic coatings, we have recently evaluated the performance of amines and oligo-amines [15], neutral synthetic and natural polymers [16] and neutral and zwitterionic surfactants [17]. Such coatings, as well as the use of acidic, isoelectric buffers for peptide separations [18], have generated a vast interest in users of CZE, since they are easy to implement and do not require any complex chemistry, such as in the case of covalent polymer coatings.…”

Feasibility of nonvolatile buffers in capillary electrophoresis‐electrospray ionization‐mass spectrometry of proteins

“…The protein peaks (and especially BSA) are somewhat broadened, indicating that the CE performance was not optimal. It should be noted, however, that in this study no attempts were made to prevent the proteins from adsorbing to the capillary wall, a notorious source of band broadening in protein CE [9,[29][30][31]. Moreover, the mixing of the capillary effluent with sheath liquid and the potentially unsuccessful circumvention of pressure differences across the capillary inherently may lead to increased peak widths.…”