Preparation and evaluation of silica-based ionic liquid-modified stationary phase for HPLC.

A new high-performance liquid chromatography (HPLC) stationary phase was firstly synthesized based on the ionic liquid 2-ethyl-4-methylimidazole chloride. And the performances of the resulting stationary phase were determined by Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), and (13)C nuclear magnetic resonance (NMR) spectroscopy. The retention characteristics of the resulting stationary phase were evaluated by normal phase HPLC conditions to separate tanshinone I and tanshinone IIA in Danshen herb. The results demonstrated that the synthesized ionic liquid was bond-linked to the silica surface successfully and that IL-modified silica is more effective than unmodified silica when separating tanshinone I and tanshinone IIA in Danshen herb.