Hexafluoroisopropanol-salt aqueous two-phase system for extraction and purification of chlorogenic acid from ramie leaves

Hexafluoroisopropanol (HFIP) was used as a phase-separation solvent to develop novel alcohol-salt aqueous two-phase systems (ATPSs) with various salts. Phase diagram and effective excluded volume (EEV) study proved that HFIP has much better phase-separation ability compared to traditional small molecule alcohols (ethanol, isopropanol and n-propanol). Then, the HFIP-NaCl ATPS was applied for the extraction and purification of chlorogenic acid (CGA) from ramie leaves. Under the optimum conditions (2 M NaCl solution with pH 3.0, the volume ratio of NaCl solution to HFIP at 6, vortex time 5 s and centrifugation time 7 min), the extraction efficiency of CGA in the salt-rich phase was 99.3%, meanwhile the HFIP-rich phase could extract a large amount of impurities. Furthermore, the CGA product with the purity of 91.0% was obtained from the salt-rich phase by semi-preparative liquid chromatography and salt removal, and its chemical structure was identified. Compared with other ATPSs, the HFIP-NaCl ATPS consumed much less organic solvent and salt, but acquired much higher extraction efficiency and obvious impurity-removal effect. Therefore, the HFIP-based alcohol-salt ATPSs are promising in the extraction and purification of CGA and other polar compounds as well.