Solid-phase extraction of liquiritin and glycyrrhizic acid from licorice using ionic liquid-based silica sorbent

A new ionic liquid-based silica sorbent was developed by a process involving surface chemical modification of commercial silica using a synthesized ionic liquid. The obtained particles were successfully used as a special sorbent in a solid-phase extraction process to isolate liquiritin and glycyrrhizic acid from licorice. Different washing and elution solvents, such as water, methanol/water (v/v), and pure methanol were evaluated. Ionic liquid-based silica sorbent was compared with traditional C-18 sorbent and it exhibited higher selectivity. Quantitative analysis was carried out by using a C-18 column. Good linearities of two compounds were obtained from 5 x 10(-4) to 0.2 mg/mL (r(2) > 0.99) with the relative standard deviations <1.0%. The target compounds in commercial herbal medicines containing licorice were determined, and the bound rates between the target compounds and protein were obtained by this sorbent.