Retention characteristics of a new butylimidazolium-based stationary phase

Abstract

A new HPLC stationary phase has been synthesized based on the ionic liquid n-butylimidazolium bromide. Imidazolium was covalently immobilized on a silica substrate through an n-alkyl tether and the retention characteristics of the resulting stationary phase were evaluated systematically. Using 28 small aromatic test solutes and reversed phase conditions, the linear solvation energy relationship approach was successfully used to characterize this new phase. The retention characteristics of the test solutes show remarkable similarity with phenyl stationary phases, despite the presence of a positive charge on the new imidazolium phase. Operated in the reversed phase mode, this new stationary phase shows considerable promise for the separation of neutral solutes and points to the potential for a truly multi-modal stationary phase.

Ionic Liquids in Separation Techniques

“…Imidazolium-based ILs were applied for synthesis of anion exchange stationary phases by Qiu and coworkers (Qiu et al, 2006a,b) enabling to separate inorganic and organic anions. In turn Sun and coworkers using the same modifier synthesized stationary phase attaching IL (1-butyl-3-heptylimidazolium bromide) to silica matrix through an alkyl tether receiving column with properties similar to conventional phenyl stationary phase (Sun et al, 2005). Wang (Wang et al, 2006) modified the surface of 3 µm diameter silica particles with the following derivatives: 1-methyl-3-(trimethoxysilylpropyl) imidazolium bromide and 1-butyl-3-(trimethoxysilylpropyl) imidazolium bromide.…”

Mutual Solubility of Hydrophobic Ionic Liquids and Water in Liquid-Liquid Two-phase Systems for Analytical Chemistry

“…Several reviews on extraction with ILs are available. 26,[86][87][88][89][90][91] The possibility of using ILs as a stationary phase in HPLC [92][93][94][95] and countercurrent chromatography 96,97 has been examined.…”

Application of Ionic Liquids in Liquid Chromatography

“…A schematic diagram of SilprMim synthesis and separation results is shown in Fig.10 and Fig.11. Next, Stalcup and co-workers (Sun et al 2005) received new column thanks to the reaction of silica gel with 1-butyl-3 heptylimidazolium bromide. IL's cation was covalently immobilized through an n-alkyl ether chain.…”

“…12. Plot of log k obtained using 60% MeOH on the butylimidazolium column versus log k obtained on conventional aliphatic reversed phase columns under the same mobile phase conditions (Sun et al 2005). …”