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.

• Klíčová slova
• chiral separation, electroosmotic flow, helicene, permanent capillary coating, polyacrylamide,
• MeSH
• akrylamid MeSH
• akrylové pryskyřice MeSH
• alkylsulfonany MeSH
• anionty MeSH
• elektroforéza kapilární * metody   MeSH
• elektrolyty MeSH
• elektroosmóza * MeSH
• fosfáty MeSH
• monosacharidy MeSH
• oxid křemičitý MeSH
• polymery MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• akrylamid MeSH
• akrylové pryskyřice MeSH
• alkylsulfonany MeSH
• anionty MeSH
• elektrolyty MeSH
• fosfáty MeSH
• monosacharidy MeSH
• oxid křemičitý MeSH
• poly(acrylamide-co-2-acrylamido-2-methyl-1-propanesulfonate) MeSH Prohlížeč
• polymery MeSH

Electroosmotic flow (EOF) plays a pivotal role in optimization of capillary electrophoresis (CE) separations of (bio)molecules and (bio)particles. EOF velocity is directly related to analysis time, peak resolution and separation efficiency. Here, we report a concept of charged polymer coatings of the inner fused silica capillary wall, which allows anodic EOF with mobility ranging from 0 to ∼(30-40) × 10-9 m2V-1s-1. The capillary wall is modified by covalently bound cationic copolymer poly(acrylamide-co-(3-acrylamidopropyl)trimethylammonium chloride) (PAMAPTAC) containing variable ratio of the charged monomer in the 0-60 mol. % interval. The EOF mobility showed minor variability with composition of background electrolyte (BGE) and pH in the 2-10 interval. The coatings were evaluated by CE-UV and nanospray CE-MS in the counter-EOF arrangement for a series of basic drug molecules in acetic acid based acidic BGE. Tunable EOF velocity was demonstrated as a useful tool for optimization of peak resolution, separation efficiency and migration time of analytes. Electrostatic repulsion of positively charged capillary surface was shown as beneficial for suppression of analyte adsorption, notably for hydrophobic cationic analytes.

• Klíčová slova
• Capillary electrophoresis, Electroosmotic flow, Mass spectrometry, Permanent polymeric coating, Sorption suppression,
• MeSH
• adsorpce MeSH
• elektroforéza kapilární * MeSH
• elektroosmóza * MeSH
• kationty MeSH
• polymery MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• kationty MeSH
• polymery MeSH

Eight different stationary phases based on two aminopropyl silicas of different brands suitable for multimodal chromatography applications have been prepared by a four-component Ugi reaction. The intention was to synthesize stationary phases significantly differing in their properties hereby demonstrating flexibility of the Ugi synthetic protocol. Diverse functional groups including a nonpolar long aliphatic chain, phenyl moiety, cholic acid scaffold, phenylboronic and monosaccharide units, charged betaine, and arginine moieties were immobilized on a silica surface. The novel sorbents were extensively characterized by elemental analysis, Raman spectroscopy, and chromatography. Considering the anchored chemical structures covalently bonded to the silica surface, reversed-phase, hydrophilic, and ion-exchange separation modes were expected. The chromatographic evaluation was performed directed to map the potential of the individual columns specifically in the mentioned chromatographic modes. The Ugi synthetic protocol has proven to be a simple, feasible, and versatile tool for the synthesis of sorbents of variable properties. The newly prepared stationary phases differed considerably in hydrophobicity and ion-exchange ability. A significant influence of the supporting aminopropyl silica on the final chromatographic behavior was observed. Finally, one practical example confirming applicability of the newly prepared sorbents was demonstrated in separation of cytarabine.

• Klíčová slova
• Ugi reaction, hydrophilic interaction, hydrophobic interaction, ion-exchange interaction, multimodal phase,
• Publikační typ
• časopisecké články MeSH