Progress in the Research on Ionic Liquid-modified Silica Stationary Phase----lanzhou Branch;Chinese Academy of Sciences

Recently, researchers of Hirotaka Iharaa of the Kumamoto University and their co-workers of the Lanzhou Institute of Chemical Physics have prepared ionic liquid-modified silica (SiImBr) using a modified method. They have characterized it in detail, and used it to separate polycyclic aromatic hydrocarbons (PAHs) containing positional isomers through multiple interactions such as hydrophobic, ∏–∏, and ion–dipole interactions between imidazolium and the analytes.

Synthesis of ionic liquid-modified silica stationary phase (SiImBr)

They found that SiImBr is less sensitive to the hydrophobicity of samples, or only has weak hydrophobic interactions with neutral samples compared to Sil-Stn and octadecylated silica (ODS). However, SiImBr is more sensitive to aromaticity than hydrophobicity. These phenomena lead to the suggestion that IL-modified silica stationary phase (SiImBr) is similar to a phenyl phase such as Sil-Stn. And SiImBr shows better planarity recognition than Sil-Stn. Another interest is that SiImBr is also sensitive for the dipoles of samples with ion–dipole interactions, especially for nitro-group-containing substances. In conclusion, the IL-modified silica stationary phase is like a phenyl phase in the separation of hydrophobic compounds such as alkylbenzenes and PAHs, but still possesses some special characteristics such as anion-exchange and ion–dipole interactions compared to conventional ODS and phenyl phases. For these reasons, its applicability may be expanded.

The detailed report of the work was published in Journal of Chromatography A (Journal of Chromatography A, 1217 (2010) 5190–5196).

Abstract of the paper published in Journal of Chromatography A