The use of ionic liquid as a mobile phase modifier in analytical supercritical fluid chromatography for the separation of flavonoids

Abstract

Due to the low viscosity of the carbon dioxide, supercritical-fluid chromatography (SFC) allows higher flow rates with lower back pressure, usually analytical SFC can provide much faster and more efficient separation compared to conventional chromatographic methods. The non-polar character of supercritical carbon dioxide (scCO2) limited SFC in separate hydrophobic compounds, but various modifiers can be used to improve the selectivity of SFC. Ionic liquids (ILs) exhibits various features including wide range of solubility, miscibility, high thermal stability, and low vapor pressure, were widely used as additive to modify the character of mobile phase, but the performance of ILs in improving SFC separation has not been evaluated. In this work, analytical SFC was applied for the separation of six flavonoid aglycones, 1-butyl-3-methyl imidazolium-based ILs were tested and compared as the mobile phase additives. ILs could significantly improve the resolution of flavonoid aglycones and the selectivity changed probably based on the hydrogen-bonding interaction.

Preparation and evaluation of 2-methylimidazolium-functionalized silica as a mixed-mode stationary phase for hydrophilic interaction and anion-exchange chromatography

“…ILs have been widely used in two aspects in high performance liquid chromatography (HPLC), which are either added in mobile phase as additives to shelter the adverse effect of residual silanols on separation of basic compounds [17][18][19] or bonded to stationary phases for chromatographic packing. Different with conventional stationary phases, ILs stationary phases can exhibit more interactions with solutes, including hydrophobic, -, electrostatic, hydrogen bonding and ion-dipole interactions [20], so it is very important for the development of mixed-mode chromatography.…”

Advanced Development of Supercritical Fluid Chromatography in Herbal Medicine Analysis

“…Sun and co-workers [63] used oxalic acid as an additive in the modifier (with MeOH/ACN, 50/50, v/v) in UHPSFC-QTOF/MS for the efficient separation of 51 prenyl flavonoids, including aglycone and glycosides from Epimedium species for the first time, then the developed method was successfully applied for the differentiation and quality assessment of Epimedium species. Gao et al [64] optimized an ionic liquid (IL) called 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ]) as an unconventional additive for the separation of six structurally similar flavonoid aglycones. The addition of IL improved the resolution and increased the retention factors.…”

A Rapid and Sensitive Method for the Simultaneous Determination of Multipolar Compounds in Plant Tea by Supercritical Fluid Chromatography Coupled to Ion Mobility Quadrupole Time-of-Flight Mass Spectrometry

“…Yang et al achieved baseline separation of 12 flavonoids on a ZORBAX RX-SIL column using SFC-DAD [ 6 ]. Gao et al isolated six flavonoid aglycones by using Poroshell 120 EC-CN as a chromatographic column and adding 20 mM [Bmim] [BF4] as a mobile phase modifier in SFC [ 7 ]. However, most of these studies only covered flavonoids widely present in traditional Chinese medicine and could not analyze compounds with different structures at the same time.…”