Aqueous biphasic system (ABS) which is a part of liquid-liquid extraction (LLE) has gained considerable importance as replacement of using volatile organic solvents in the extraction of various bioactive compounds [1]. The main advantage of using ABS is that it composed of two water soluble solutes that separate into two co-existing phases at their optimum concentration. Since major constituent is water ABS are more biocompatible and also provides benign media for extraction [2]. In the formation of ABS ionic liquid (IL) played an important role as phase forming promoters, which facilitates the tuning of the polarities and affinities of co-existing phase, which further helps in enhancing extraction efficiencies [3]. In recent years, ionic liquids (ILs) were proposed as efficient phase forming agents that could substitute polymers. ILs being designer solvents showed wide solubility for compounds of variable polarity and are thus capable of extracting or separating target compounds from fermentation broth, biomass etc. In this context, we proposed ABS based on monocationic and dicationic ionic liquids (MILs and DILs) and scrutinized for their ability to extract model non-steroidal anti-inflammatory drugs (NSAIDs). To date, active research has been done on MILs, and its properties and applications have been extensively studied. On the contrary, not much research was done on DILs, which composed of two cationic groups linked by a rigid or flexible spacer with counter anions [4]. In this work, we synthesized imidazolium, pyrrolidinium, morpholinium, and ammonium-based MILs and corresponding DILs with bromide as common anion. The ability of synthesized ILs to undergo phase separation was explored in combination with various potassium salts such as K3PO4, K2HPO4, and K2CO3 at 298.15 K and atmospheric pressure. The phase behavior of proposed MILs and DILs was analyzed with the help of binodal curve and tie lines of selected ternary system composed of MIL/DIL, potassium salts and water. The systematic comparison of phase formation by MILs and DILs has been carried out. Further, the extraction capability of the designed ABS was evaluated for NSAIDs by using UV-visible spectroscopy. The proposed MILs and DIL based ABS showed appreciable ability to undergo phase formation as well as to extract the pharmaceutical compound of interest.
References
[1] A. Basaiahgari and R. L. Gardas, J. Chem. Thermodyn, 2018, 120, 88-96.
[2] V. P. Priyanka, A. Basaiahgari and R. L. Gardas, J.Mol. Liq. 2017, 247, 207.
[3] A. Basaiahgari, S. K. Yadav and R. L. Gardas, Pure Appl. Chem. 2019, 91, 1279-1294.
[4] H. Shirota, T. Mandai, H. Fukazawa and T. Kato, J. Chem. Eng. Data.2011, 56, 2453.