Covalent anionic copolymer coatings with tunable electroosmotic flow for optimization of capillary electrophoretic separations |
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Authors: | Veronika Šolínová Petr Tůma Maria Butnariu Václav Kašička Dušan Koval |
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Affiliation: | 1. Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czech Republic;2. Department of Hygiene, Third Faculty of Medicine, Charles University, Prague 10, Czech Republic;3. Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czech Republic Department of Analytical Chemistry, Faculty of Science, Charles University, Prague 2, Czech Republic |
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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. |
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Keywords: | chiral separation electroosmotic flow helicene permanent capillary coating polyacrylamide |
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