Ionic liquids as mobile phase additives for high‐performance liquid chromatography separation of phenoxy acid herbicides and phenols

Abstract

In this present study, 1-butyl-3-methylimidazolium chloride ([C 4 MIM]Cl), 1-octyl-3-methylimidazolium chloride ([C 8 MIM]Cl), and 1-decyl-3-methylimidazolium chloride ([C 10 MIM]Cl) were adopted as mobile phase additives in the high performance liquid chromatography (HPLC) to simultaneously separate phenoxy acid herbicides and phenols at neutral pH. It was found that by using 20 mM of [C 4 MIM]Cl, baseline separation and good chromatograms for all the acid compounds were obtained on a normal reversedphase C 18 column. The retention time of the target acid compounds shortened with the increase of the alkyl chain length and the concentrations of ionic liquids, probably due to the delocalization of the positive charge on the imidazolium cation, the repulsion between chlorine ions of ionic liquids and the acid compounds, as well as the stereo-hindrance effect. The mechanism with ionic liquids as mobile additives for the separation of acid compounds was discussed.

Ionic liquid‐based single‐drop liquid‐phase microextraction combined with high‐performance liquid chromatography for the determination of sulfonamides in environmental water

“…Compared with the traditional organic solvents, ionic liquids show unique advantages of low water solubility, high boiling point and viscosity and good thermostability [24] as well as the ability of being directly used for reversed-phase HPLC. Ionic liquids have been successfully applied in previous works [19,25].…”

Advances in analytical chemistry using the unique properties of ionic liquids

“…Our group [71] 4 ] and triethylamine are similar, as the cations of these additives are significantly adsorbed on the stationary phase, whereas the corresponding anions are weakly, or not, adsorbed [72].…”

Application of Ionic Liquids in Liquid Chromatography

“…Fig.8 presents example of improvement of 1,4 benzodiazepine separation by addition of 3 mM [BMIM][Cl] to acetonitrile-water mobile phase on Zorbax SB-Phenyl column. According to this scheme, positive charge on the surface is responsible for retention decrease of protonated amines at higher concentration of ionic liquid chloride in the mobile phase.Though, some papers (Hu et al, 2009;Stepnowski et al, 2006) demonstrated adsorption of ILs on hydrophobic surface, nobody has shown before real reflectance of these speculations in retention factor and connection with ILs concentration in the mobile phase.…”