Common Deep Eutectic Solvents Research Articles

Fluorescently Labeling Amino Acids in a Deep Eutectic Solvent.

The increased use of deep eutectic solvents (DESs) in recent years has been significant and provides new approaches to sample collection and preparation. At the same time, the use of these new solvents to prepare samples can present challenges for subsequent analyses. Common analytical approaches, such as fluorescent labeling, may not be compatible with the solvents. In this work, we explore how effective three traditional fluorescent labels can be at derivatizing amino acids in the most common DESs, formed from choline chloride and ethylene glycol. We demonstrate that the unique solvent characteristics of the DESs still allow for two of the fluorophores, fluorescein isothiocyanate and 5-carboxyfluorescein succinimidyl ester, to effectively label amino acids. Initial optimizations of the reaction conditions demonstrate that we can effectively label both d- and l-amino acids, in solution with concentrations of amino acids down to 4 μM. Capillary electrophoretic separations following this preparation can detect as little as 50 nM. This is possible without removal of any DES from the sample matrix. These results represent the first complete fluorescent labeling reaction in a DES and subsequent capillary electrophoretic separation of the analytes.

Mild and efficient recovery of lithium-ion battery cathode material by deep eutectic solvents with natural and cheap components

Dissolution of lithium cobalt oxide (LCO) is the key step for the recovery of valuable metals (e.g., Co and Li) from spent LCO-based lithium-ion batteries (LIBs). However, the dissolution process of LCO either needs toxic solvents, and high temperature, or shows low efficiency. Deep eutectic solvents (DESs) are potential green solvents to dissolve LCO. Here, DESs with polyethylene glycol (PEG) as hydrogen bond acceptor and ascorbic acid (AA) as hydrogen bond donor are found to dissolve LCO with 84.2% Co leaching efficiency at 80 oC and 72 h, which is higher than that from the reported references by common DESs. Furthermore, both DESs components (i.e., PEG and AA) are cheap, biodegradable, and biocompatible. AA could be easily and abundantly extracted from natural fruits or vegetables. It provides a new guide for the green, mild, and efficient dissolution of LCO aiming at sustainable recovery of spent LIBs.

Computational Evaluation of Mixtures of Hydrofluorocarbons and Deep Eutectic Solvents for Absorption Refrigeration Systems.

We used computational tools to evaluate three working fluid mixtures for single-effect absorption refrigeration systems, where the generator (desorber) is powered by waste or solar heat. The mixtures studied here resulted from combining a widely used hydrofluorocarbon (HFC) refrigerant, R134a, with three common deep eutectic solvents (DESs) formed by mixing choline chloride (hydrogen bond acceptor, HBA) with urea, glycerol, or ethylene glycol as the hydrogen bond donor (HBD) species. The COSMOtherm/TmoleX software package was used in combination with refrigerant data from NIST/REFPROP, to perform a thermodynamic evaluation of absorption refrigeration cycles using the proposed working fluid mixtures. Afterward, classical MD simulations of the three mixtures were performed to gain insight on these systems at the molecular level. Larger cycle efficiencies are obtained when R134a is combined with choline chloride and ethylene glycol, followed by the system where glycerol is the HBD, and finally that where the HBD is urea. MD simulations indicate that the local density profiles of all species exhibit very sharp variations in systems containing glycerol or urea; furthermore, the Henry's law constants of R134a in these two systems are larger than those observed for the HFC in choline chloride and ethylene glycol, indicating that R134a is more soluble in the latter DES. Interaction energies indicate that the R134a-R134a interactions are weaker in the system where ethylene glycol is the HBD, as compared to in the other DES. Radial distribution functions confirm that in all systems, the DES species do not form strong directional interactions (e.g., hydrogen bonds) with the R134a molecules. Relatively strong interactions are observed between the Cl anions and the hydrogen atoms in R134a; however, the atom-atom interactions between R134a and the cation and HBD species are weaker and do not play a significant role in the solvation of the refrigerant. In all systems, R134a has the largest diffusion coefficients, followed by the HBD, the anion and the cation; the diffusion coefficients are the largest in the systems containing ethylene glycol, followed by those having glycerol and urea. This work is our first step toward our long-term goal of designing and demonstrating optimal working fluid mixtures for use in absorption refrigeration systems. Our results suggest that COSMO-RS can be used to perform a rapid screening of a large number of working fluid mixtures, and select a few candidates for further exploration using molecular simulations and experiments. These latter approaches can be used to refine the accuracy of the COSMO-RS predictions, and to optimize the selection of optimal working fluid mixtures for demonstration in absorption refrigeration systems powered by solar or waste heat sources.

The effect of deep eutectic solvents on catalytic function and structure of bovine liver catalase

Aqueous solutions of reline and glyceline, the most common deep eutectic solvents, were used as a medium for Catalase reaction. By some spectroscopic methods such as UV–vis, fluorescence and circular dichroism (CD) function and structure of Catalase were investigated in aqueous solutions of reline and glyceline. These studies showed that the binding affinity of the substrate to the enzyme increased in the presence of 100mM glyceline solution, which contrasts with reline solution that probably relates to instructive changes in secondary structure of protein. Meanwhile, enzyme remained nearly 70% and 80% active in this concentration of glyceline and reline solutions respectively. In the high concentration of DES solutions, enzyme became mainly inactive but surprisingly stayed in nearly 40% active in choline chloride solution, which is the common ion species in reline and glyceline solvents. It is proposed that the chaotropic nature of choline cation might stop the reducing trend of activity in concentrated choline chloride solutions but this instructive effect is lost in aqueous deep eutectic solvents. In this regard, the presence of various concentrations of deep eutectic solvents in the aqueous media of human cells would be an activity adjuster for this important enzyme in its different operation conditions.

Solvation analysis of some Solvatochromic probes in binary mixtures of reline, ethaline, and glyceline with DMSO

Binary mixtures of solvents are widely used in chemical processes in order to tune the polarity properties of the media and to facilitate chemical and physical processes. In this study, deep eutectic solvents (DESs) were considered as new green media for chemical processes. Solvatochromic behavior was investigated at 25°C over the whole range of mole fractions of binary mixtures of dimethyl sulfoxide with urea-choline chloride (reline), ethylene glycol-choline chloride (ethaline), and glycerol-choline chloride (glyceline) with as common DESs. In these DESs the molar ratio of choline chloride to urea, ethylene glycol and glycerol is 1:2. Results showed that the polarity and hydrogen bond donor ability of the DESs decreases with increasing mole fraction of dimethyl sulfoxide as a molecular solvent, while hydrogen bond acceptor ability of the media increases with mole fraction of DMSO. Deviation from ideal behavior, observed for solvatochromic parameters, confirmed preferential solvation of the solutes in these media. On the other hand, molecular dynamic simulations and quantum mechanics calculations concluded interaction energies between DES components and showed clearly different compositions in the solvation shells of the solutes in the solvent mixtures.

Densities and dynamic viscosities of (choline chloride + glycerol) deep eutectic solvent and its aqueous mixtures in the temperature range (283.15–363.15) K

Deep eutectic solvents (DESs) are emerging as one of the most promising environmentally benign and cost-effective alternatives to the conventional organic solvents. Many common DESs are readily miscible with water. Aqueous mixtures of DESs have potential to afford modified properties for specific applications. Densities and dynamic viscosities of a common and popular DES composed of choline chloride and glycerol in 1:2 mole ratio, named glyceline, and its aqueous mixtures in the temperature range 283.15–363.15K are reported. Decrease in density with increasing temperature is found to follow a quadratic expression. Excess molar volumes of the aqueous mixtures of glyceline are found to be negative and significant at all temperatures and compositions. Absolute excess molar volume is found to decrease as the temperature is increased from 283.15K to 323.15K. For temperature above 323.15K, the excess molar volume does not change much with further increase in temperature till 363.15K. Temperature dependence of dynamic viscosity of aqueous mixtures of glyceline in the temperature range 283.15–363.15K at all compositions is found to be better described by a Vogel–Fulcher–Tamman (VFT) model. Excess logarithmic viscosities for aqueous mixtures of glyceline are found to be positive at all temperatures and compositions investigated. The results highlight relatively stronger interactions, preferably H-bonding type, between water and glyceline, as compared to those among water and among glyceline molecules, respectively. Facile interstitial accommodation of water within H-bonded glyceline network also appears to contribute to the experimental observations.