Gas-assisted three-liquid-phase extraction(GATE), which has the advantages of both three-liquid-phase extraction and solvent sublation, is a novel separation technique for separation and concentration of two organic compounds into different phases in one step. This highly effective and economically applicable method has been developed for separating emodin and rhein from herbal extract. In a GATE system composed of butyl acetate/PEG4000/ammonium sulfate aqueous solution, influence of various parameters including gas flow rate, flotation time, salt concentration, initial volume of PEG and butyl acetate was investigated. Within 50 min of 30 ml·min-1nitrogen flow, removal ratio of emodin and rhein from aqueous phase could be over 99% and 97%, respectively.Mass fraction of emodin in the BA phase and rhein in the PEG phase could reach 97% and 95%, respectively. It is demonstrated that gas bubbling is effective for partitioning of emodin and rhein into butyl acetate and PEG phase respectively, and dispersed PEG and butyl acetate could be captured from the aqueous solution. Experimental results show that GATE could be an effective and economical technology for concentration and separation of co-existed products in medicinal plants.
