Solid-phase extraction of tanshinones from Salvia Miltiorrhiza Bunge using ionic liquid-modified silica sorbents

New ionic liquid-modified silica sorbents were developed by the surface chemical modification of the commercial silica using synthesized ionic liquids. The obtained ionic liquid-modified particles were successfully used as a special sorbent in solid-phase extraction process to isolation of cryptotanshinone, tanshinone I and tanshinone IIA from Salvia Miltiorrhiza Bunge. Different washing and elution solvents such as water, methanol and methanol–acetic acid (90/10, v/v) were evaluated. A comparison of ionic liquid-modified silica cartridges and traditional silica cartridge show that higher recovery was observed using ionic liquid-modified silica sorbents. A quantitative analysis was conducted by high-performance liquid chromatography using a C18 column (5 μm, 150 mm × 4.6 mm) with methanol–water (78:22, v/v, and containing 0.5% acetic acid) as a mobile phase. Good linearity was obtained from 0.5 × 10−4 to 0.5 mg/mL (r2 > 0.999) with the relative standard deviations less than 4.8%.