초록
As a green solvent, ionic liquid was developed as a substitute for conventional volatile organic solvents in the extraction field. In this work, several task-specific acidic ionic liquids (TAILs) were applied for ultrasonic-assisted extraction (UAE) of chlorogenic acid (CGA) from ramie leaves. The influencing parameters, viz. ionic liquid (IL) concentration, liquid-solid ratio, and ultrasonic time, were optimized using response surface methodology (RSM). Of the ILs examined, 1-butyl-3-methylimidazolium hydrogen sulfate ([C<SUB>4</SUB>mim]HSO<SUB>4</SUB>) exhibited the best extraction ability. The RSM results revealed that optimized conditions are IL concentration 52.28% (w/w), liquid-solid ratio 89.05:1, and ultrasonic time 49.88min. An aqueous two-phase system (ATPS) formed by IL extract and salt was then developed for further extraction and purification of CGA. The influencing factors of salt type and concentration, pH, and temperature were investigated in detail. The maximum extraction efficiency of 96.18% was obtained in the IL-rich phase under the conditions of 35.83% (w/w) [C<SUB>4</SUB>mim]HSO<SUB>4</SUB> and 14.13% (w/w) Na<SUB>2</SUB>SO<SUB>4</SUB>, pH 3 and temperature 37<SUP>o</SUP>C. After extraction, the isolation of CGA and recycling of IL were achieved by back-extraction using a water immiscible organic solvent. This simple and efficient IL-UAE coupled with ATPS has potentiality for the extraction and purification of CGA and other compounds in pilot- or large-scale operations.