Preparation, characterization and evaluation of an imidazolium ionic liquid copolymer stationary phase for mixed-mode chromatography†
A novel imidazolium ionic liquid mixed-mode stationary phase (named IBON) was successfully prepared by a controlled thiol-initiated radical polymerization method. The successful preparation of the IBON stationary phase was certified by Fourier transform infrared (FT-IR) spectrometry, elemental analysis, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Meanwhile, the zeta potential showed the surface potential of the IBON stationary phase, while the results of gel permeation chromatography (GPC) demonstrated the successful control of the surface-initiated polymerization. The retention behaviour was investigated by various types of analytes, including acidic compounds, basic compounds and neutral compounds (containing polar nucleosides and bases, non-polar benzene series). Through investigating the influence of the acetonitrile content, pH of the mobile phase, buffer concentration on the retention and by employing the van't Hoff equation and linear solvation energy relationships model, it was found that the various test solutes could undergo multiple interactions with the IBON stationary phase, including hydrophobic, electrostatic, dipole–dipole, hydrogen bonding, ion exchange and π–π interactions. The prepared stationary phase was employed to separate polar solutes, benzene series, and inorganic anions, and it displayed different separation characters when compared to the commercial Acclaim™ Mixed-mode WAX-1 column.