Thermodynamics of acetaminophen and bovine serum albumin partitioning in ternary aqueous solutions comprising polyethylene glycol dimethyl ether 250 and choline bitartrate: Liquid-liquid equilibria, volumetric and acoustic investigations

Abstract

The present work reports the biocompatible and nontoxic aqueous biphasic system, ABS, for acetaminophen and bovine serum albumin, BSA, separation. First, the binodal curves and tie-lines for {polyethylene glycol dimethyl ether 250 (PEGDME250) + choline bitartrate ([Ch][Bit]) + water} system was measured at different temperatures under atmospheric pressure (≈ 85 kPa). The phase separation in this ABS was studied by the salting-out coefficents obtained from tie-lines correaltion with setschenow equation. The results indicated that the biphasic region was enhanced by enhancing temperatre. The experimental data were fitted by two semi-empirical equations including Marchuk and Zafarani-Moattar equations for binodals and Othmer-Tobias, Bancroft, Osmotic virial equations, and e-or m-NRTL models for the tie-lines. Later, the performance of this ABS in acetaminophen and BSA partitioning was examined via calculation of partition coefficients and extraction efficiencies at different tie-lines and temperatures, the trend showed that the acetaminophen could be partitioned preferentially into the polymer-rich top phase with a single step extraction efficiency up to 80%, in where the BSA was effectively transferred into the [Ch][Bit]-rich bottom phase. In order to evaluate the driving-force for acetaminophen preferentially transferring to top phase, density and sound speed for systems (acetaminophen + PEGDME250 + water) and (acetaminophen + [Ch][Bit] + water) were determined at 298.15 K and the obtained results utilized for calculation the infinite molar volume and compressibility, and the transfer molar volume and compressibility. From density and sound speed results, it may be concluded that the favorable interactions between acetaminophen and PEGDME250 is responsible for preferentially acetaminophen transferring into top phase.