Some Novel Liquid Partitioning Systems:  Water−Ionic Liquids and Aqueous Biphasic Systems

Abstract

Partition coefficients, as values of log P, between water and two room-temperature ionic liquids and between water and an aqueous biphasic system have been correlated with Abraham's solute descriptors to yield linear free energy relationships that can be used to predict further values of log P, to ascertain the solute properties that lead to increased or decreased log P values, and to characterize the partition systems. It is shown that, in all three of the systems, an increase in solute hydrogen-bond basicity leads to a decrease in log P and an increase in solute volume leads to an increase in log P. For the two ionic liquid systems, an increase in solute hydrogenbond acidity similarly decreases log P, but for the aqueous biphasic system, solute hydrogenbond acidity has no effect on log P. These effects are rather smaller than those observed in traditional water-solvent systems. However, the ionic liquids appear to have an increased affinity for polyaromatic hydrocarbons as compared to traditional organic solvents. Principal component analysis and nonlinear mapping show that the three unconventional partition systems are considerably different from conventional water-organic solvent systems. IntroductionA major contemporary industrial challenge is to continued manufacturing beneficial chemical products while eliminating or substantially reducing the detrimental environmental consequences of the processes adopted. The Montreal Protocol 1 identified the need to reevaluate chemical processes to take account of their environmental impact, especially with regard to the use of volatile organic solvents. In addition, some 90% of hazardous waste is aqueous in nature, 2 and thus, industry is reliant upon efficient separations from liquid media. To this end, liquid-liquid separations are widely applied in the chemical process industry. Typically, because of their immiscibility with water, volatile organic solvents are often employed in such processes. 3 Taken together, these issues suggest that the elimination of the use of flammable toxic and volatile organic solvents in separations processing represents a significant step in the creation of a sustainable industrial technology. 4 A number of different approaches to this problem have been identified, including solvent-free synthesis, the use of water as a solvent, 5 the use of supercritical fluids, 6 and the use of ionic liquids. Recently, roomtemperature ionic liquids (RTILs) have received worldwide attention 7,8 as replacements for organic solvents in catalysis, 9 synthesis, 10,11 and separations processes. 12,13 Room-temperature ionic liquids, in contrast to conventional ionic liquids such as molten sodium chloride, which are only liquids at temperatures above 800°C, represent ionic salts that are liquid at room temperature. Many RTILs are liquids over a wide temperature range, and RTILs with melting points as low as -96°C are known. The constituents of many RTILs (being ionic) are constrained by high Coulombic forces and thus exert practically no vapor pressure abo...

Use of Ionic Liquids for Liquid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons

“…This is because LPME is a nonequilibrium procedure, and the obtained peak area is a complex result of various parameters including partition coefficient, the diffusion coefficient of the solute, the solubility of the extraction solvent in the sample solution, and the viscosity of both sample solution and solvent. Abraham et al 15 calculated the partition coefficients (log P) of fluoranthene to be 4. 22 Extraction Mode.…”

“…These can be used to predict further values of log P, to ascertain the solute properties that lead to increased or decreased log P, and to characterize the partition systems. 15 More recently, Carda-Broch et al 16 The majority of the studies related to IL focus on their potential use in industrial processes, and limited efforts have been made to apply IL to analytical chemistry purposes. Shetty et al 17 studied the applicability of alkylammonium nitrate and thiocyanate as a mobile phase in microcolumn reversed-phase liquid chromatography.…”

“…Considering that naphthalene 10 and fluoranthene 15 have relative large partition coefficients in the [C n MIM][PF 6 ]/water (n ) 4, 6) systems, IL drop-based direct-immersion and headspace LPME procedures were tried for extraction of polycyclic aromatic hydrocarbons (PAHs) from aqueous samples.…”

Green Composites from Ionic Liquid-Assisted Processing of Sustainable Resources: A Brief Overview

“…Some ILs are considered as highly polar solvents due to their excellent solvation properties. A number of techniques could be used to predict the polarity of ILs, such as solvatochromic dyes [24], partition [25], and fluorescence probe methods [26]. Generally, ILs are immiscible with most of the organic solvents like hexane and ether but miscible with most of the polar solvents, such as ketones, lower alcohols, and dichloromethane [27].…”

Extraction of organic impurities using 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6]

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