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

•Liquid-liquid chromatography was studied in sample pretreatment for quantification.•Continuous-stirred tank reactors model was used to predict collection time of analytes.•Determination of wilforlide A in Tripterygium wilfordii and tablets was established.•A new method for sample pretreatment in analysis of trace component was developed.