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

Abstract

We describe the use of a tri(ethylene glycol)-terminated alkyltrichlorosilane to create a very thin, protein-resistant "self-assembled monolayer" coating on the inner surface of a fused-silica capillary. The same compound has been demonstrated previously on flat silica substrates to resist adsorption of many proteins. As a covalently bound capillary coating, it displays good resistance to the adsorption of cationic proteins, providing clean separations of a mixture of lysozyme, cytochrome c, ribonuclease A, and myoglobin for more than 200 consecutive runs. Electroosmotic flow (EOF) was measured as a function of pH; the coated capillary retains significant cathodal EOF, with roughly 50% of the EOF of an uncoated capillary at neutral pH, making this coating promising for applications requiring some EOF. The EOF was reasonably stable, with a 2.9% relative standard deviation during a 24 h period consisting of 72 consecutive separations of cationic proteins. Efficiencies for cationic protein separations were moderate, in the range of 190,000-290,000 theoretical plates per meter. The coating procedure was simple, requiring only a standard cleaning procedure followed by a rinse with the silane reagent at room temperature. No buffer additives are required to maintain the stability of the coating, making it flexible for a range of applications, potentially including capillary electrophoresis-mass spectrometry (CE-MS).

Advances in the analysis of proteins and peptides by capillary electrophoresis with matrix‐assisted laser desorption/ionization and electrospray‐mass spectrometry detection

“…BCQ, but also physically adhered PB coating, were superior to APS in separating peptides and glycopeptides in terms of theoretical plate numbers and reduced contribution to the chemical background [37,114]. Recently, a simple coating procedure has been published creating a thin layer of tri(ethylene glycol)-terminated alkyltrichlorosilane by selfassembling [183]. In general, covalent coatings of the Si-O type suffer from restricted durability [24,178,184] or, as in the case of the more persistent Si-C bonds, are laborious to prepare [185].…”

Capillary electrophoresis–mass spectrometry as a powerful tool in clinical diagnosis and biomarker discovery

“…It still remains to be seen whether this type of coating is compatible with clinical samples, but it appears to be a very promising approach. Some other coatings like a physically adsorbed methacrylate-based coating (Gonzalez et al, 2003) or an alkyltrichlosilane-based approach (Meagher et al, 2004) or a recently commercial available coating (UltraTrol TM , Target Discovery, Palo Alto, CA) need to be tested for their suitability for routine protein applications in clinically relevant approaches.…”

Capillary electrophoresis of proteins 2003–2005

“…Some low-molecular-weight compounds have been used to reduce EOF in capillary including tri(ethylene glycol) terminated alkyl trichlorosilane [68], ionic liquids based on 1-alkyl-3-methylimidazolium [69], and 1-(4-iodobutyl)4-aza-1-azoniabicyclo[2,2,2]octane iodide [53]. The last compound interacts after its addition to BGE with the wall, and thus exhibits some properties of a static coating.…”