Ionic liquid 1-butyl-3-methylimidazolium bromide as a promoter for the formation and extraction capability of poly(ethylene glycol)-potassium citrate aqueous biphasic system at T = 298.15 K

Abstract

In biotechnology, extraction by means of aqueous biphasic systems (ABS) is known as a promising tool for the separation and purification of bio-molecules. Polyethylene glycols (PEGs) are a class of polymers widely used in typical polymer-salt ABS. However, the hydrophilic nature of PEGs limits the applicability of this technique, specially, when the goal is to extract hydrophobic bio-molecules. To overcome this limitation, in recent years, a new approach has been proposed based on the use of ionic liquids (ILs) as adjuvants in ABS. In this regard, this work is devoted to evaluate the potential use of IL 1-butyl-3-methylimidazolium bromide ([C4mim]Br) as an adjuvant in the green {PEG 400+tri-potassium citrate (K3C6H5O7)} ABS for the separation of bio-molecules. For this purpose, phase diagrams and the liquid–liquid equilibrium (LLE) data for the {PEG 400+K3C6H5O7} ABS with the addition of small quantities of IL were determined at T=298.15K. The mutual immiscibility for the PEG 400 and K3C6H5O7 in water was observed to promote by the presence of IL. Moreover, the phase behavior of the studied ABS is described by the NRTL model. In addition, the partition coefficients of l-tryptophan (KTrp), as a model bio-molecule, were determined in the studied system at T=298.15K. The results obtained indicate that the addition of small quantities of [C4mim]Br to the {PEG 400+K3C6H5O7} ABS could largely enhance the extraction efficiency for l-tryptophan.