Temperature-responsive ionic liquids to set up a method for the simultaneous extraction and in situ preconcentration of hydrophilic and lipophilic compounds from medicinal plant matrices†
In this work, we developed a novel and green method for the simultaneous extraction and in situ preconcentration of both lipophilic and hydrophilic compounds from a complex matrix by using a switchable temperature-responsive ionic liquid (TRIL)–water system. As a case study, the representative TRIL–water mixture, the 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM][BF4])–water system, and chrysanthemums containing both lipophilic and hydrophilic compounds were selected. Then we investigated the influence of the extraction temperature, liquid/solid ratio and ionic liquid content on the extraction efficiency for the target compounds and the influence of the temperature and ionic liquid content on the in situ separation process. Our results indicated that the IL–water mixture has a higher extraction efficiency for target compounds compared with the conventional organic solvents. More importantly, after the extraction, the IL phase and the aqueous phase were separated when the IL–water mixture was cooled to room temperature. The hydrophilic and lipophilic compounds were separately re-dissolved in the aqueous phase and the IL phase, respectively, and thus the in situ separation of target compounds was achieved. The integrated method avoided the use of volatile toxic organic solvents, which showed great application potential. In addition, the method also provided a new idea for the application of ionic liquids in the extraction and separation of natural products.