Liquid-liquid chromatography in sample pretreatment for quantitative analysis of trace component in traditional Chinese medicines by conventional liquid chromatography

A method for sample pretreatment using liquid-liquid chromatography combined with a conventional liquid chromatography was developed for quantitative determination of trace chemical component in traditional Chinese medicine. The main effective component, wilforlide A, in the traditional Chinese medicinal herb Tripterygium wilfordii as well as in its Chinese patent medicine glycosides tablets was successfully determined after sample pretreatment by liquid-liquid chromatography. A biphasic solvent system n-hexane-ethyl acetate-ethanol-water (6:4:6:4, v/v) was screened for crude sample treatment by liquid-liquid chromatography. The collection time of eluted fractions containing target component could be well predicted using a continuous-stirred tank reactors model after determination of its retention time. Then, quantitative analysis of wilforlide A in Tripterygium wilfordii as well as in its tablets could be successfully determined by conventional reversed-phase high performance liquid chromatography with UV detector. Under the optimized conditions, the method showed good linearity (R2 = 0.9999) for wilforlide A in the range of 0.01 mg mL-1 -0.10 mg mL-1. The limit of detection and limit of quantity were 1.35 ng mL-1 and 4.50 ng mL-1, respectively. The average recovery rate, intra-day and inter-day precisions of wilforlide A were 96.43%, 0.67% and 1.14%, respectively. Compared with previous studies, the present method showed advantages of complete recovery of target component in the sample pretreatment and good repeatability.