Covalent anionic copolymer coatings with tunable electroosmotic flow for optimization of capillary electrophoretic separations
Color online: See the article online to view Figures 2–5 in color.
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.
CONFLICT OF INTEREST
The authors have declared no conflict of interest.
DATA AVAILABILITY STATEMENT
The data that support the findings of this study is available from the corresponding author upon reasonable request.
|elps7704-sup-0001-SuppMat.pdf1.7 MB||Supporting Information|
Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
- 1. Protein attachment onto silica surfaces – a survey of molecular fundamentals, resulting effects and novel preventive strategies in CE. Electrophoresis. 2009; 30: 2032–61.
- 2, , . Non-covalent capillary coatings for protein separations in capillary electrophoresis. J Chromatogr A. 2008; 1184: 81–105.
- 3, , , . Quantification of adsorption and optimization of separation of proteins in capillary electrophoresis. Anal Chem. 2020; 92: 10743–50.
- 4, . Surface deactivation in protein and peptide analysis by capillary electrophoresis. Anal Chim Acta. 1999; 383: 1–26.
- 5, , , . Relevance and use of capillary coatings in capillary electrophoresis-mass spectrometry. Anal Bioanal Chem. 2010; 396: 297–314.
- 6, . Polymer wall coatings for capillary electrophoresis. Electrophoresis. 2001; 22: 644–55.
- 7, . Recent advances in column coatings for capillary electrophoresis of proteins. TrAC Trends Anal Chem. 2017; 90: 38–44.
- 8, . Pressure-assisted capillary electrophoresis for cation separations using a sequential injection analysis manifold and contactless conductivity detection. Talanta. 2011; 84: 1228–33.
- 9, , , . Heart-cutting two-dimensional capillary electrophoresis for the on-line purification and separation of derivatized amino acids. Anal Chem. 2008; 80: 1730–6.
- 10, , , , , . Pressure-assisted capillary electrophoresis electrospray ionization mass spectrometry for analysis of multivalent anions. Anal Chem. 2002; 74: 6224–9.
- 11, , , . Large volume sample stacking of antiepileptic drugs in counter current electrophoresis performed in PAMAPTAC coated capillary. Talanta. 2021; 221:121626.
- 12, , , . Electrophoretic determination of symmetric and asymmetric dimethylarginine in human blood plasma with whole capillary sample injection. Int J Mol Sci. 2021; 22: 14.
- 13, , , . Separation of anaesthetic ketamine and its derivates in PAMAPTAC coated capillaries with tuneable counter-current electroosmotic flow. Talanta. 2020; 217:121094.
- 14, , , . Measuring venous-arterial differences of valine, isoleucine, leucine, alanine and glutamine in skeletal muscles using counter-current electrophoresis with contactless conductivity detection. J Electroanal Chem. 2020; 857:113772.
- 15, , , , , , et al. Capillary zone electrophoresis-top-down tandem mass spectrometry for in-depth characterization of hemoglobin proteoforms in clinical and veterinary samples. Anal Chem. 2020; 92: 10531–9.
- 16, , , , . Modulation of the electroosmotic mobility using polyelectrolyte multilayer coatings for protein analysis by capillary electrophoresis. Anal Chim Acta. 2019; 1057: 152–61.
- 17, , . Polyelectrolyte multilayer coatings for the separation of proteins by capillary electrophoresis: influence of polyelectrolyte nature and multilayer crosslinking. J Chromatogr A. 2015; 1399: 80–7.
- 18, , , , . Covalent cationic copolymer coatings allowing tunable electroosmotic flow for optimization of capillary electrophoretic separations. Anal Chim Acta. 2021; 1178:338789.
- 19, , , . Interfacing monolith-based electrochromatography in microchips with inductively coupled plasma mass spectrometry for elemental speciation. J Anal Atom Spectrom. 2016; 31: 1869–76.
- 20, . Poly(carboxyethyl acrylate-co-ethylene glycol dimethacrylate) precursor monolith with bonded octadecyl ligands for use in reversed-phase capillary electrochromatography. Electrophoresis. 2021; 42: 2656–63.
- 21, , . Development and in situ synthesis of monolithic stationary phases for electrochromatographic separations. Electrophoresis. 2004; 25: 3204–15.
- 22, , , . Capillary electrochromatography-mass spectrometry of kynurenine pathway metabolites. J Chromatogr A. 2021; 1651:462294.
- 23, , . Using scanning contactless conductivity to optimise photografting procedures and capacity in the production of polymer ion-exchange monoliths. Analyst. 2009; 134: 1314–21.
- 24, . Establishing repeatability and ruggedness of chiral separations in micellar electrokinetic chromatography mass spectrometry: Combined use of covalently bonded capillary column and molecular micelles. J Chromatogr A. 2020; 1617:460835.
- 25, , , , . Effects of structure on the performance of latex nanoparticles as a pseudostationary phase in electrokinetic chromatography. Anal Chim Acta. 2018; 1000: 293–302.
- 26, . Effect of pendant group structures on the chemical selectivity and performance of sulfonated copolymers as novel pseudophases in electrokinetic chromatography. Electrophoresis. 2002; 23: 1285–95.
- 27, , . Sulfonated acrylamide copolymers as pseudo-stationary phases in electrokinetic chromatography. J Chromatogr A. 2001; 905: 281–90.
- 28, , , , . Rapid analysis of peptides and amino acids by CE-ESI-MS using chemically modified fused-silica capillaries. Electrophoresis. 2009; 30: 2273–9.
- 29, , , . Synthesis and evaluation of anionic polymer-coated capillaries with pH-independent electroosmotic flow for capillary electrophoresis. J Chromatogr A. 1994; 685: 303–12.
- 30, , . Control of the EOF in CE using polyelectrolytes of different charge densities. Electrophoresis. 2007; 28: 925–31.
- 31, , , . Separation of polyelectrolytes of variable compositions by free-zone capillary electrophoresis. J Chromatogr A. 1997; 766: 233–6.
- 32, , , , . Determination of the compositional distribution of copolymers by frontal analysis continuous capillary electrophoresis. Anal Chem. 2000; 72: 255–8.
- 33, , , , . Prediction of polyelectrolyte complex stoichiometry for highly hydrophilic polyelectrolytes. Macromolecules. 2016; 49: 3881–8.
- 34, , , . Solvent effects on the copolymerization kinetics of ionic (AMPS) and non-ionic (HEAm) acrylamide derivatives. Eur Polym J. 2008; 44: 1843–8.
- 35, , , , , , et al. Helquats: a facile, modular, scalable route to novel helical dications. Chem Eur J. 2009; 15: 1072–6.
- 36, , , , , . Chiral analysis of helquats by capillary electrophoresis: resolution of helical N-heteroaromatic dications using randomly sulfated cyclodextrins. Electrophoresis. 2011; 32: 2683–92.
- 37, , , , , , et al. Resolution of a configurationally stable helquat: enantiocomposition analysis of a helicene congener by capillary electrophoresis. New J Chem. 2010; 34: 1063–7.
- 38, , , , , , et al. Preferential crystallization of a helicene-viologen hybrid – an efficient method to resolve [5helquat enantiomers on a 20 g scale. Eur J Org Chem. 2012; 2012: 489–99.
- 39, , , , , , et al. Search for conglomerate in set of helquat salts: multigram resolution of helicene-viologen hybrid by preferential crystallization. J Org Chem. 2013; 78: 1329–42.
- 40, , , , , , et al. Saddlequat: a helquat captured on its racemization pathway. Chem Sci. 2011; 2: 2314–20.
- 41, , , , , , et al. A chiral dicationic circulenoid: photochemical origin and facile thermal conversion into a helicene congener. Angew Chem Int Ed. 2012; 51: 11972–6.
- 42, , , , , , et al. Highly modular assembly of cationic helical scaffolds: rapid synthesis of diverse helquats via differential quaternization. Tetrahedron. 2010; 66: 3537–52.
- 43. Frequency-tuned contactless conductivity detector for the electrophoretic separation of clinical samples in capillaries with very small internal dimensions. J Sep Sci. 2017; 40: 940–7.
- 44, , , . Photopolymerization of acrylamide as a new functionalization way of silica monoliths for hydrophilic interaction chromatography and coated silica capillaries for capillary electrophoresis. J Chromatogr A. 2014; 1326: 89–95.
- 45, , . Photografting as a versatile, localizable, and single-step surface functionalization of silica-based monoliths dedicated to microscale separation techniques. J Sep Sci. 2013; 36: 993–1001.
- 46, , , , , , et al. Generalized model of the linear theory of electromigration and its application to electrokinetic chromatography: theory and software PeakMaster 6-next generation. Electrophoresis. 2019; 40: 683–92.
- 47, , , . Sheathless capillary electrophoresis-mass spectrometry for anionic metabolic profiling. Electrophoresis. 2016; 37: 1007–14.
- 48. Sheathless capillary electrophoresis-mass spectrometry for the profiling of charged metabolites in biological samples. Methods Mol Biol. 2018; 1738: 183–92.
- 49, , . Electrophoretic effects of the adsorption of anionic surfactants to poly(dimethylsiloxane)-coated capillaries. Anal Chem. 2007; 79: 6675–81.
- 50, , , , . Sensitive monitoring of 3-hydroxybutyrate as an indicator of human fasting in a PAMAMPS coated capillary. Talanta. 2022; 247:123582.