Good’s buffers as novel phase-forming components of ionic-liquid-based aqueous biphasic systems
•Development of self-buffering and biocompatible systems for the separation of amino acids.•Novel class of aqueous biphasic systems composed of ionic liquids and biological buffers.•Adequate Good’s buffers and ionic liquids are able to undergo liquid–liquid demixing.•The extraction efficiencies of l-tryptophan and l-phenylalanine range between 22 and 100%.
Aiming at the development of self-buffering and benign extraction/separation processes, this work reports a novel class of aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and organic biological buffers (Good’s buffers, GBs). A large array of ILs and GBs was investigated, revealing than only the more hydrophobic and fluorinated ILs are able to form ABS. For these systems, the phase diagrams, tie-lines, tie-line lengths, and critical points were determined at 25 °C. The ABS were then evaluated as alternative liquid–liquid extraction strategies for two amino acids (l-phenylalanine and l-tryptophan). The single-step extraction efficiencies for the GB-rich phase range between 22.4 and 100.0% (complete extraction). Contrarily to the most conventional IL-salt ABS, in most of the systems investigated, the amino acids preferentially migrate for the more biocompatible and hydrophilic GB-rich phase. Remarkably, in two of the studied ABS, l-phenylalanine completely partitions to the GB-rich phase while l-tryptophan shows a preferential affinity for the opposite phase. These results show that the extraction efficiencies of similar amino acids can be tailored by the design of the chemical structures of the phase-forming components, creating thus new possibilities for the use of IL-based ABS in biotechnological separations.
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Journal: Biochemical Engineering Journal - Volume 101, 15 September 2015, Pages 142–149