Cationic poly(methacryl oxyethyl trimethylammonium) and its poly(ethylene glycol)‐grafted analogue as capillary coating materials in electrophoresis

Abstract

Cationic polyelectrolytes were synthesized and used as semipermanent coating materials for capillaries in electrophoresis. The polyelectrolytes used were a homopolymer of poly(methacryl oxyethyl trimethylammonium chloride) (PMOTAC) and its poly(ethylene glycol) (PEG)-grafted analogue. Two PMOTAC polyelectrolytes, with molar masses of 85,000 and 300,000 g/mol, and PEG-grafted PMOTAC with a molar mass of 280,000 g/mol were synthesized and then characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Attachment of the polyelectrolytes to the wall of the fused silica capillary for electrophoresis caused the electroosmotic flow (EOF) to reverse. The polyelectrolyte coatings were tested over the pH range 2-11 at different buffer ionic strengths, and the most stable and strongest anodic EOFs were obtained at acidic pH values with low ionic strength buffers. Between runs the capillary is merely rinsed for 2 or 3 min with the background electrolyte solution. With the PMOTAC coatings at pH values 5, the RSDs of the EOFs were less than 2.9% after 60 injections. The effects of the molar mass of the polycation and of PEGylation of PMOTAC on the interactions between the polycations and basic proteins were studied at acidic pH values. The differences in the effective electrophoretic mobilities, resolution values, and plate numbers of the proteins with the different coatings were due to the EOF, as demonstrated through calculations of reduced mobilities, relative resolution values, and relative plate numbers.

Surface initiated polymerization of a cationic monomer on inner surfaces of silica capillaries: Analyte separation by capillary electrophoresis versus polyelectrolyte behavior

“…The reproducibility of the EOF mobility was still as low as 0.5% (RSD) for 25 repetitions after 1 month. The stability of the capillaries was excellent and greatly improved compared to that observed earlier in studies of PMOTAC‐coated capillaries due to the covalent grafting of the capillary surface.…”

Novel cationic polyelectrolyte coatings for capillary electrophoresis

“…The EOF directly after the coating process was ‐4.57·10 −8 m 2 ·V −1 ·s −1 (RSD 0.68%; n = 5) for PMOTAI and ‐4.14·10 −8 m 2 ·V −1 ·s −1 (RSD 1.62%; n = 5) for PIL‐1 using phosphate buffer at pH 7.4 (ionic strength of 10 mM). Lower stability for freshly coated capillary was found with similar structure polyelectrolyte poly(methacryl oxyethyl trimethylammonium chloride) with M W of 85 000 and 300 000 g/mol . Both PECs exhibited bleeding from the capillary, which can be seen from the continuously decreasing mobility of EOF (Fig.…”

“…In our study, we observed further decrease of EOF at pH 11 (especially for PIL‐1) and a substantial increase in the RSD values (5.44% for PMOTAI and 9.29% for PIL‐1; n = 5). Higher instability in the basic pH region has also been observed earlier when using similar PECs in CE . Moreover, Nehmé et al .…”

Brush‐like copolymer as a physically adsorbed coating for protein separation by capillary electrophoresis

“…‘Static’ adsorbed coatings are particularly attractive, including numerous homopolymers such as poly(ethylene oxide) (PEO) 19, hydroxyethylcellulose (HEC) 20, poly(vinyl alcohol) (PVA) 21, poly( N , N ‐dimethylacrylamide) (PDMA) 22, 23, poly( N ‐hydroxyethylacrylamide) (PHEA) 1, polyethyleneimine 24, polybrene 25, chitosan 26, and so on. Among them, PEO, poly(ethylene glycol) (PEG, the low‐molecular mass form of PEO), and their derivatives (such as PEG methyl ether methacrylate (PEGMA)), are well known to be the most desirable and effective molecules for reducing the surface adsorption of proteins 27–29. However, they still face some problems, e.g.…”