Rational approach to solvent system selection for liquid–liquid extraction–assisted sample pretreatment in counter–current chromatography

Abstract A rational liquid–liquid extraction approach was established to pre–treat samples for high–speed counter–current chromatography (HSCCC). n -Hexane–ethyl acetate–methanol–water (4:5:4:5, v/v) and (1:5:1:5, v/v) were selected as solvent systems for liquid–liquid extraction by systematically screening K of target compounds to remove low- and high-polarity impurities in the sample, respectively. After liquid–liquid extraction was performed, 1.4 g of crude sample II was obtained from 18.5 g of crude sample I which was extracted from the flowers of Robinia pseudoacacia L., and then separated with HSCCC by using a solvent system composed of n –hexane–ethyl acetate–methanol–water (1:2:1:2, v/v). As a result, 31 mg of robinin and 37 mg of kaempferol 7– O –α– l –rhamnopyranoside were isolated from 200 mg of crude sample II in a single run of HSCCC. A scale–up separation was also performed, and 160 mg of robinin with 95% purity and 188 mg of kaempferol 7– O –α– l –rhamnopyranoside with 97% purity were produced from 1.2 g of crude sample II.