Covalent anionic copolymer coatings with tunable electroosmotic flow for optimization of capillary electrophoretic separations

Abstract

We present a method for finely adjustable electroosmotic flow (EOF) velocity in cathodic direction for the optimization of separations in capillary electrophoresis. To this end, we use surface modification of the separation fused silica capillary by the covalently attached copolymer of acrylamide (AM) and 2‐acrylamido‐2‐methyl‐1‐propanesulfonate (AMPS), that is, poly(AM‐co‐AMPS) or PAMAMPS. Coatings were formed by the in‐capillary polymerization of a mixture of the neutral AM and anionic AMPS monomers premixed in various ratios in order to control the charge density of the copolymer. EOF mobility varies in the 0 to ∼40 × 10−9 m2 V−1 s−1 interval for PAMAMPS coatings ranging from 0 to 60 mol.% of charged AMPS monomer. For EOF in PAMAMPS‐treated capillaries, we observed (i) a negligible dependence on pH in the 2–10 interval, (ii) a minor variance among background electrolytes (BGEs) in function of their components and (iii) its standard decrease with increasing ionic strength of the BGE. Interest in variable cathodic EOF was demonstrated by the amelioration of separation of two kinds of isomeric anionic analytes, that is, monosaccharides phosphates and helquat enantiomers, in counter‐EOF mode.

Preparation and Properties of PDMS Surface Coating for Ultra-Low Friction Characteristics

“…Therefore, the surface roughness and thickness of the as-prepared coatings were reduced by increasing AMPS concentration, causing the surface of the coatings to become smoother. In the process of UV curing, the two monomers polymerized in PDMS to form a coating; meanwhile, the two monomers polymerized to form a PAM/AMPS binary copolymer on the surface. − This is potentially why the roughness and thickness of the coating surface decrease with increasing AMPS concentration. Because further increasing the concentration of AMPS added was not conducive to the formation of the coating, the maximum concentration of AMPS was set to 6 wt %.…”

Preparation of open tubular capillary column covalently coated with polystyrene sulfonate with 4,4′‐Azobis(4‐cyanopentanoyl chloride) as polymerization initiator for electrochromatographic separation of alkaloids, sulfonamides, and peptides

“…The buffer inside the capillary is set into motion due to an electrical double layer formed at the surface of the capillary after applying an electric field, for negatively charged surfaces, as for fused silica and anionic polymers such as in Azo-Co-PSS column, positive counter ions in the diffuse double layer will move in the direction to the cathode dragging the liquid along with them. This movement of the buffer is known as EOF which plays a vital role in electrophoretic separation [43][44][45].…”

Recent developments and applications of capillary and microchip electrophoresis in proteomics and peptidomics (mid‐2018–2022)

“…Another often observed problem during CZE separations is the adsorption of the analytes, especially proteins, and peptides, on the inner wall of the commonly used bare fused silica (BFS) capillary. To avoid this phenomenon, and to reduce or eliminate EOF, BGEs with very low pH, various additives of BGEs or different permanent capillary coatings are utilized [37][38][39][40]. The absence of EOF results in slower CE separation but it enlarges the separation window for MS and MS/MS analysis, which is necessary for large-scale proteomics.…”