Evaluation of Cation Influence on the Formation and Extraction Capability of Ionic-Liquid-Based Aqueous Biphasic Systems

Abstract

In addition to the large range of applications proposed in literature, ionic liquids (ILs) have been recently reported to be able to form aqueous biphasic systems (ABS). They could thus be interesting media in biotechnological applications for the separation and purification of vital biomolecules. Therefore, in this work, a systematic study involving a large number of imidazolium-based ILs was conducted to provide new information related to ILs' ABS-promoting capability and extraction ability. For that purpose, the influence of the number of alkyl groups present at the cation, the cation side alkyl chain length, and the presence of double bonds, aromatic rings, and hydroxyl groups on this alkyl chain were evaluated. Ternary phase diagrams of the ABS formed by these ILs and K 3 PO 4 and the respective tie-lines were measured and presented. The ABS here investigated were further characterized for the first time accordingly to their extractive potential for amino acids, where L-tryptophan was selected as a model biomolecule. The partition coefficients here obtained were shown to be substantially larger than those observed in conventional ABS, demonstrating therefore the fine potential of IL-based ABS for biomolecules separation and purification.

Extraction of vanillin using ionic-liquid-based aqueous two-phase systems

“…The presence of a double bound, an aromatic moiety or an hydroxyl group at the imidazolium alkyl chain increases the IL hydrophilicity or the IL affinity for water [10]. Nevertheless, the partition coefficients of vanillin were not significantly enhanced using [C 7 The results indicate that an increase in the IL cation hydrophilic character by the inclusion of additional functional groups does not improves the vanillin extraction.…”

“…Only for [OHC 2 mim]Cl a different composition (15 wt% of K 3 PO 4 , 40 wt% of IL and 45 wt% of the aqueous solution of vanillin) was used due to the smaller two-phase region obtained within this IL. The ternary mixtures compositions were chosen based on the phase diagrams of each IL reported in previous works [6,10]. The ternary compositions were prepared by weight with an uncertainty of ±10 −5 g. The vanillin content influence was studied using different concentrations of the compound at the aqueous phase composition (0.5 g dm −3 , 1.0 g dm −3 , 2.5 g dm −3 , 5.0 g dm −3 and 7.5 g dm −3 which correspond to 3.3 × 10 −3 mol dm −3 , 6.6 × 10 −3 mol dm −3 , 1.6 × 10 −2 mol dm −3 , 3.3 × 10 −2 mol dm −3 and 4.9 × 10 −2 mol dm −3 , respectively).…”

“…Organic solvents may be substituted by hydrophobic ILs as a second immiscible liquid phase with aqueous media [9] or by the use of ATPS incorporating hydrophilic ILs [6,[10][11][12][13]. Indeed, few years ago, Gutowski et al [12] showed that aqueous solutions of imidazolium-based ILs can form ATPS under the addition of appropriate inorganic salts, such as K 3 PO 4 .…”

“…Since then, the equilibrium properties of systems comprising ILs, for the development of specific extraction and isolation procedures, have been inves- tigated at our laboratory [9,[13][14][15][16][17][18][19]. It was already shown that ATPS formed by K 3 PO 4 and ILs are extremely advantageous for the partition of several biomolecules yielding larger partition coefficients than those conventionally obtained with polymer-inorganic salts or polymer-polymer ATPS [6,10,13]. The extractive potential of biomolecules using IL-based ATPS was previously studied for distinct compounds, such as testosterone and epitestosterone, alkaloids, antibiotics, bovine serum albumin, penicillin G, ltryptophan and food coulorants [6,10,13,[20][21][22][23][24].…”

Ionic Liquids in Separation Techniques

“…That is why after addition of water-structuring salts (kosmotropic salts) they are salted out and aqueous biphasic systems are formed (Bridges et al, 2007;Zafarani-Moattar & Hamzehzadeh, 2009;Neves et al, 2009;Deng et al, 2007;Pei et al, 2007). Classification of salts is based on the Hofmeister series ordered from kosmotropic to chaotropic accordingly to the ability of salt to protein precipitation.…”