Electroosmotic flow modulation in capillary electrophoresis by organic cations from ionic liquids

Abstract

This paper describes the ability of several ionic liquids cations for electroosmotic flow modulation in capillary electrophoresis. Organic salts based on phosphonium, sulfonium, cysteinium, ammonium, and guanidinium cations were selected to study this property. In addition, the synergistic effect of these compounds in cyclodextrin chiral separation was also evaluated. In comparison with most studied imidazolium-based ionic liquids, several of the cations studied, are stronger modifiers in terms of electroosmotic flow (EOF) modulation. Phosphonium-based compounds and tri-octyl methylammonium chloride ([Aliquat]Cl) had the strongest ability to reverse EOF both in acidic and in basic conditions and had the lowest EOF reversal concentrations in the presence of hydroxypropyl-β-cyclodextrin. EOF modulation ability of phosphonium cations also contributed to the improvement of chiral separation of DL-propranolol by hydroxypropyl-β-cyclodextrin at lower concentrations in comparison with most commonly used EOF modulators such as tetrabutylammonium phosphate.

Effect of ionic liquids on the interaction between liposomes and common wastewater pollutants investigated by capillary electrophoresis

“…The long-chain [P 14444 ]Cl reversed the mobility of EOF at an IL concentration of 0.05 mM (0.002%), while using the shorter-chained IL, the mobility of EOF did not reverse until the [P 8444 ]Cl concentration was increased to 28.4 mM (1%). Long alkylchain phosphonium based ILs are known to enhance EOF mobility suppression and its reversal [21][22][23], which is in accordance with our results.…”

“…Concentrations of [emim][OAc] above 5.9 mM (0.1%) slightly suppressed the EOF mobility, most likely due to altered viscosity and ionic strength of the buffer. Longer-chain imidazolium ILs have been tested at similar concentrations (10-20 mM IL in phosphate buffer at pH 7.4; ionic strength of 100 mM) and those results are in accordance with ours, even though the ionic strength used was much higher than in our system [22]. However, the mobility of EOF is highly dependent on the alkyl chain length of the IL [24] and some more lipophilic ILs, for example 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ]), have shown to reverse the mobility of EOF when used as additives in the BGE [25].…”

Application of cyclodextrins in chiral capillary electrophoresis

“…The non‐CD selectors can interact with CD itself and thus change the CD's binding properties. A typical example of this behavior are ionic liquids that have become popular in the last few years in many fields . Ionic liquids change both the EOF (due to their charge) and the interaction abilities of CDs with analytes.…”

Recent advances in electrodriven enantioseparations

“…Another study described the enantioselective separation of naphthylimidazole derivatives of D / L ‐monosaccharides . Additionally, the enantiomers of amlodipine and propranolol were separated using polybrene and ionic liquids, respectively, as EOF modifiers.…”