Deep Eutectic Solvents Composition Research Articles

Combination of a Deep Eutectic Solvent and Macroporous Resin for Green Recovery of Iridoids, Chlorogenic Acid, and Flavonoids from Eucommia ulmoides Leaves.

To increase the effectiveness of using typical biomass waste as a resource, iridoids, chlorogenic acid, and flavonoids from the waste biomass of Eucommia ulmoides leaves (EULs) were extracted by deep eutectic solvents (DESs) in conjunction with macroporous resin. To optimize the extract conditions, the experiment of response surface was employed with the single-factor of DES composition molar ratio, liquid-solid ratio, water percentage, extraction temperature, and extraction time. The findings demonstrated that the theoretical simulated extraction yield of chlorogenic acid (CGA), geniposidic acid (GPA), aucubin (AU), geniposide (GP), rutin (RU), and isoquercetin (IQU) were 42.8, 137.2, 156.7, 5.4, 13.5, and 12.8 mg/g, respectively, under optimal conditions (hydrogen bond donor-hydrogen bond acceptor molar ratio of 1.96, liquid-solid ratio of 28.89 mL/g, water percentage of 38.44%, temperature of 317.36 K, and time of 55.59 min). Then, 12 resins were evaluated for their adsorption and desorption capabilities for the target components, and the HPD950 resin was found to operate at its optimum. Additionally, the HPD950 resin demonstrated significant sustainability and considerable potential in the recyclability test. Finally, the hypoglycemic in vitro, hypolipidemic in vitro, immunomodulatory, and anti-inflammatory effects of EUL extract were evaluated, and the correlation analysis of six active components with biological activity and physicochemical characteristics of DESs by heatmap were discussed. The findings of this study can offer a theoretical foundation for the extraction of valuable components by DESs from waste biomass, as well as specific utility benefits for the creation and development of natural products.

Hydroxyl-rich ferrofluid for efficient liquid phase microextraction of cinnamic acid derivatives in traditional Chinese medicine.

In this study, a hydroxyl-rich ferrofluid was prepared by dispersing silica-coated magnetic nanoparticles into a methyltrioctylammonium chloride-glycerol deep eutectic solvent and then employed in the preconcentration of trace-level of cinnamic acid derivatives (caffeic acid, p-hydroxycinnamic acid, ferulic acid, and cinnamic acid) in traditional Chinese medicine prior to high-performance liquid chromatography analysis. The structures of the synthesized materials were characterized by X-ray diffraction and infrared spectroscopy. The experimental parameters affecting the extraction performance, such as deep eutectic solvent composition, dosage of ferrofluid, pH of aqueous sample solution, salt concentration, extraction time, type, and volume of desorption solvent, were studied and optimized. Under the optimum conditions, the enrichment factors of four cinnamic acid derivatives were in the range of 107-114. Low detection limits (0.2-0.9ng/mL), good precisions (relative standard deviations 1.2%-9.5%), and satisfactory recoveries (96.0%-104.7%) were achieved. Subsequently, the possible microextraction mechanism of the proposed method was explored and elucidated. It showed that the prepared ferrofluid is easily dispersed in the aqueous sample and achieved recovery after the extraction. The developed approach is a simple, convenient, and efficient method for preconcentration and determination of cinnamic acid derivatives in complex matrices.

Deep eutectic solvent extraction combined with magnetic bead ligand fishing for identification of α-glucosidase inhibitors from Pueraria lobata.

In this study, a deep eutectic solvent (DES) extraction combined with a magnetic bead ligand affinity analytical method was developed and used for α-glucosidase inhibitor identification from Pueraria lobata. Several critical parameters affecting the analysis performance, including the type of DES, molar ratio, water amount, pH, salt concentration, and volume of DES, were investigated. The selected analytical sample preparation conditions were as follows. The composition of DES is choline chloride-1,4-butanediol (1:3), the water content is 40%, pH is 7.0 and the volume of extraction solution is 2 mL. The obtained sample extraction solution was analyzed directly using α-glucosidase immobilized magnetic beads (GMBs). Three α-glucosidase inhibitors in Pueraria lobata, including puerarin, daidzin, and daidzein, were identified. Luteolin was used as a positive control to evaluate the method's selectivity. Results showed it could selectively bond to the GMBs in the DES. As the affinity analysis was performed directly in a DES, the solution-removing process could be avoided. The intra-day and inter-day precisions of the method are 5.21% and 6.38%, respectively. The solvent amount was 1/50-1/2000 of that used in traditional methods.

Study of the Effect of Water Content in Deep Eutectic Phases on the Extraction of Fatty Acids from Microalgae Biomass

Microalgae, as some of the oldest life forms on Earth, are of significant interest to industry and in terms of environmental policies, due to their ability to perform photosynthesis and consume atmospheric carbon dioxide. Moreover, they contain a wide variety of value-added compounds such as amino acids and proteins, carbohydrates, and fatty acids, which can be exploited in multiple fields like medicine, cosmetics, nutritional supplements, and for the production of biodiesel. In this article, Nannochloropsis gaditana, a type of microalgae that inhabits both fresh and salt water, is studied for fatty acid recovery using deep eutectic solvents (DES). This microalgae species is a natural source of eicosapentaenoic acid (EPA), an omega-3 compound that is commonly used in the nutritional industry. There are numerous extraction techniques and pretreatments to obtain these compounds. In this work, DES are studied as extractive agents due to their advantages as neoteric solvents. Specifically, this work focuses on an assessment of the effect of the composition of DES on the extraction yield of fatty acids from microalgae. Several DES compositions based on choline chloride, ethylene glycol, and fructose are studied to analyze the influence of water content in these phases. The results show that water content significantly influences recovery yields. The DES with higher extractive capacity were those based on choline chloride, ethylene glycol, and water at a molar ratio of 1:2:2. This composition offered 48.7% of the yield obtained with a conventional solvent like methanol for the recovery of EPA (11.2 mg/g microalgae). Furthermore, the choline chloride-fructose-based DES shows the capability of selective extractions of fatty acids with low carbon content—choline chloride:fructose:water (molar ratio 2:1:2) can extract 0.14 mg of decanoic acid/g of microalgae, indicating that this DES composition can recover 35.7% more decanoic acid in comparison to methanol.

A novel deep eutectic solvent as an extractant for the determination of bisphenol compounds in edible oils by high-performance liquid-phase fluorescence detection

In this study, an efficient, low-cost and environmentally friendly deep eutectic solvent (DES) was prepared using methanol and betaine, which was then employed as an extractant to detect BPA and BPF in several edible oils by high performance liquid chromatography-fluorescence detection (HPLC-FLD) with good results. The electrostatic potentials of methanol, betaine, water and BPs were analyzed by quantum chemical computational techniques to explain the mechanism of DES extraction. Several important parameters affecting the extraction efficiency, composition, volume and extraction time of DES were optimized. The optimum conditions for the use of DES were the molar ratio of 1:30 (betaine: methanol), the volume of DES of 200 μL and the extraction time of 1.5 min. The results of the method evaluation showed a wide linear range (0.01–0.8 μg g−1) and a high linear correlation coefficient (R2 ≥0.994). The limit of detection (LOD) and limit of quantification (LOQ) values ranged from 1.65 to 2.92 ng g−1 and 5.45–9.64 ng g−1, respectively. The greenness of the assay was evaluated by applying the green analytical procedure index method, and the results showed that the experimental method has the advantages of simple sample pre-treatment and low amount of waste generated during the assay. The experimental method has potential applications in the field of the detection of bisphenol compounds in edible oils.

Efficient Plutonium Extraction and Electrochemical Insights in a Hydrophobic Deep Eutectic Solvent for Radioactive Waste Management

In this study, we explore the extraction and electrochemical characteristics of Plutonium using a hydrophobic deep eutectic solvent (DES) consisting of tetra-Butyl Ammonium Bromide(TBABr) as the hydrogen bond acceptor and Decanoic acid (DA) as the hydrogen bond donor in a 1:2 ratio composition. Hydrophobic DES possesses unique attributes, such as low volatility and a high affinity for metal ions, making it a promising choice for Plutonium extraction. We systematically investigate the influence of various parameters, including DES composition, acid concentration, and extraction duration. Our extraction experiments reveal that the hydrophobic DES exhibits its maximum Plutonium extraction efficiency (95%) at a 4 M HNO3 concentration, with a distribution coefficient (D) reaching nearly 71. To gain insights into the electrochemical behavior of Plutonium within the hydrophobic DES, we conduct cyclic voltammetry experiments. The resulting voltammograms offer valuable insights into the redox properties and stability of Plutonium species within the DES. Furthermore, we analyze the impact of potential scan rate on the electrochemical response, shedding light on the kinetics and mechanisms underlying Plutonium electrochemistry within the hydrophobic DES. These findings underscore the considerable potential of hydrophobic DES for efficient Plutonium extraction and electrochemical separation. This research contributes to the development of sustainable and environmentally friendly approaches for managing Plutonium, particularly in the context of nuclear waste disposal

Application, structure, salts and complexes of lidocaine: a review. Part II. lidocaine in the composition of deep-eutectic solvents, microemulsions and coordination compounds

The review focuses on lidocaine (2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide), one of the most popular and widely used painkillers. In the first part, the use of lidocaine in various branches of medicine was considered, and the structure of lidocaine, as well as of its salts such as hydrochloride monohydrate, hydrohexafluoroarsenate, bis-p-nitrophenylphosphate, barbiturate and indomethacin-lidocaine complex was discussed. The present paper reports on the use of lidocaine in the composition of deep-eutectic solvents (DESs) with acrylic acids, with such hydrogen bond donors as ibuprofen, 1,8-octanediol, tetracaine, prilocaine and vanillin, with such nonsteroidal anti-inflammatory drugs as ketoprofen, flurbiprofen, aceclofenac, tenoxicam and meloxicam. The use of lidocaine in DES-microemulsions (MEs) is also considered: lidocaine-prilocaine and lidocaine-ibuprofen prepared and served as the oil phase in ME, and lidocaine-lauric acid as an amphiphilic DES utilized as surfactant in ME. Consideration of lidocaine in the composition of coordination compounds has begun: the results of studying the structure of complexes of lidocaine with chlorides of zinc, copper, cobalt, platinum and iron, as well as with copper bromide, have been discussed.

A catalase enzyme biosensor for hydrogen peroxide at a poly(safranine T)-ternary deep eutectic solvent and carbon nanotube modified electrode

A new electrochemical enzyme biosensor has been developed to monitor hydrogen peroxide. The sensor uses a multiwalled carbon nanotube modified glassy carbon electrode covered by a poly(safranine T) polymer film prepared by potential cycling electropolymerization in ternary deep eutectic solvent (DES), prepared from choline chloride (ChCl), ethylene glycol (EG) plus malonic acid (MA) or lactic acid (LA) with composition optimization. It is shown that this leads to greater polymer growth and improved film properties compared to binary DES; the process was monitored by an electrochemical quartz crystal microbalance. The best ternary DES composition was found to be 16 % ChCl:MA / 84 % ChCl:EG. Electrochemical characterisation was done by cyclic voltammetry and electrochemical impedance spectroscopy, and the morphology of the synthesized polymer films was examined by scanning electron microscopy. Catalase enzyme was immobilized on the modified electrode and the enzyme biosensor used for measurement of hydrogen peroxide, with a very low detection limit of 34 nM. The selectivity was found to be excellent in relation to common interferents and the biosensor showed very good recovery in peroxide measurements in commercial samples.

A surfactant-based quasi-hydrophobic deep eutectic solvent for dispersive liquid-liquid microextraction of gliflozins from environmental water samples using UHPLC/fluorescence detection

Despite the anticipated exceptional properties of deep eutectic solvents (DES) in microextraction techniques, their self-aggregation behaviour has only been sporadically studied in the previous literature. In the presented study, a novel surfactant-based quasi-hydrophobic deep eutectic solvent (DES) is synthesized and utilized in dispersive liquid-liquid microextraction (DLLME) of three gliflozins in environmental water samples as a proof-of-concept examples. The synthesized DES is composed of benzalkonium chloride (BZKCl) as a hydrogen bond acceptor and octanol (Oct) as a hydrogen bond donor. A full optimization of the extraction conditions was carried out including molar ratio and composition of DES, volume of DES, volume of water samples, extraction time and type of diluting solvent. Moreover, the extraction mechanism was thoroughly investigated, and it was established that the extraction of the target analytes is attributed to the analytes' incorporation into the micelles’ cores that facilitates mass transfer from the aqueous layer into DES layer. Furthermore, micelles formed by surfactant-based DES will provide adequate dispersion of extractant phase within water samples, which consequently improves the extraction efficiency. Micelles formation was confirmed by transmission electron microscopy (TEM). Furthermore, 1H NMR spectra verifies that the synthesized DES keeps its integrity even after extraction, which excludes any decomposition of DES after DLLME procedure. The extraction recovery is in an excellent agreement with the hydrophobicity of the investigated drugs, being the highest for the most hydrophobic one. The extracted analytes were separated by UHPLC coupled with fluorescence detection. Under the optimized experimental conditions, the method exhibits excellent linearity and a high detection sensitivity with a limit of detection of 0.5, 2.0 and 0.1 ng mL−1 for EMP (empagliflozin), DAP (dapagliflozin) and CAN (canagliflozin), respectively. The greenness of the developed microextraction approach was assessed by different greenness metrics such as Complex GAPI and AGREE tools. The developed method shows excellent greenness of synthetic procedure for preparation of DES, the environmentally benign nature of DLLME procedure as well as the greenness of the developed UHPLC approach.

A hydrophobic deep eutectic solvent-based vortex-assisted liquid-liquid microextraction applied for doping control of aromatase inhibitors from equine urine

Aromatase inhibitors (AIs) can indirectly cause increased testosterone in animals, which leads to the improvement of the athletic ability of horses. For the protection of horses and the consideration of fair competition, AIs were listed as prohibited drugs by the Federation Equestre Internationale (FEI). There were several disadvantages using traditional pretreatment methods before analyzing these drugs from biological samples. A rapid and green pretreatment method has been developed by utilizing the hydrophobic deep eutectic solvent (DES)-based vortex-assisted liquid-liquid microextraction (DES-VALLME) followed by ultra-high performance liquid chromatography tandem triple-quadrupole mass spectrometry (UHPLC-MS/MS) technique for the efficient extraction and sensitive detection of AIs in equine urine samples. The combination of menthol and 4-fluorophenol in a molar ratio 1:4 was chosen as the optimum composition of DES for extracting AIs. Under the optimum conditions, only 80 μL of DES, 1 mL equine urine and 2 min were expended. An external standard calibration method was utilized for determination, and a linear relationship was achieved with a concentration range of 0.02–4000 ng mL−1 (r2 ≥ 0.9983). The limits of detection of the method based on a signal-to-noise ratio of 3 were 0.01–4 ng mL−1. The accuracy recoveries ranged from 94.9% to 113.4% within the intra-day and inter-day relative standard deviations of less than 9.1%. Compared with traditional extraction methods, the DES-VALLME method had the advantages of rapidity, simplicity, efficiency, low toxicity, and low cost. This method has potential and possessed brilliant prospects for doping control.

A natural hydrophobic deep eutectic solvent-based microextraction method integrated with a spectrofluorimetric technique for the determination of daclatasvir as a direct-acting hepatitis C antiviral drug in plasma samples

An ultrasound-assisted emulsification microextraction method based on a natural hydrophobic deep eutectic solvent (USAEME-HDES) was developed for extraction and preconcentration of daclatasvir, a hepatitis C virus inhibitor, from plasma samples prior to spectrofluorimetric measurement. To make the deep eutectic solvent (DES) compatible with the fluorescence device, fatty acids were used as components of DES that can simultaneously act as hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA). Various parameters, such as the solvent effect on the fluorescence spectrum and the composition and ratio of DES, were investigated and optimized. Other parameters, including pH, DES volume, sonication time, and NaCl concentration, were investigated and optimized using the central composite design combined with the desirability function. Under optimal conditions, compared to other methods, this method had a wide linear range (5–600 ng/mL) with a good coefficient of determination (0.9985) and a low limit of detection (1.42 ng/mL). Drug analysis results in the plasma samples showed that the method has good accuracy. Finally, the Green Analytical Procedure Index (GAPI) tool was used to evaluate the greenness of the method, which demonstrates our method's superior eco-friendship in comparison to other reported methods.

Electrified interfaces of deep eutectic solvents

Many theoretical and experimental studies have been focused on the physicochemical properties of dense ionic fluids such as ionic liquids (ILs). However, less attention has been given to interfacial properties involving deep eutectic solvents (DES). The impact of the DES composition, hydrogen bond donor (HBD) structure, temperature, and electrode nature material on the DES-electrode vertical interactions remain vague. The lack of knowledge imposes significant constraints in proposing a suitable Electrical Double Layer model (EDL) to describe the DES at electrified interfaces. Measuring differential capacitance-potential curves is a strategy to assess the EDL structure and understand how ions interact with the electrode surface, which knowledge is fundamental to designing and optimizing electrochemical systems for various applications (e.g., energy storage devices). Accordingly, a set of choline chloride-based DESs was assessed containing distinct HBD at their eutectic composition (the polyalcohol's 1,2-ethanediol, 1,2-propylene glycol, 1,3-propylene glycol, and the amide urea) against glassy carbon (GC), gold (Au), and the platinum (Pt) electrode at different temperatures.The differential capacitance-potential curves were found to vary significantly in shape in the three different electrode surfaces studied, ranging from camel shape (Au electrode), U-shape (GC), and asymmetric bell shape (polycrystalline Pt). The carboxylic malonic and oxalic acids were also assessed for a proper comparison to understand better the role of the HBD's functional group in shaping the electrode-electrolyte structure against the trend found with diol isomers. A suitable EDL model must inevitably accommodate interfacial properties assessed at the capacitive region, namely the influence of the surface chemistry, potential dependence, DES structure molecules, and temperature in shaping the electrified interfacial anatomy.

Microfluidic formation of surface nanodroplets using green deep eutectic solvents for liquid–liquid nanoextraction and controlled precipitation

HypothesisSurface nanodroplets have recently been employed for in situ chemical analysis leveraging their low volume, e.g. O(10−15 L), that enables rapid analyte extraction and pre-concentration. So far, most surface nanodroplets have been formed using single organic solvents such as 1-octanol, toluene, among others. Designing multicomponent surface nanodroplet with controllable composition is highly desirable for extending their application as extractant. ExperimentHere, we formed surface nanodroplets using green deep eutectic solvent (gDES) composed of thymol and decanoic acid, both of which are naturally occurring chemicals. The influence of parameters such as flowrate and the composition of deep eutectic solvent on the surface nanodroplet formation were studied. As proof-of-concept, the gDES surface nanodroplets were further used to extract and detect trace amounts of fluorescent rhodamine 6G dye and copper ions from water. FindingsThe formation of gDES surface nanodroplets follows the theoretical model which states that the final droplet volume (Vf) scales with the Peclét number (Pe) of the flow during formation by the solvent exchange process, that is Vf ∼ Pe3/4, and the nanodroplets demonstrate excellent ability as extractant for rhodamine 6G and copper ions from water. Surprisingly, the confined volume of gDES surface nanodroplets enables fast and controlled formation of Cu (II)-decanoate crystal.

COSMO-SAC and QSPR combined models: A flexible and reliable strategy for screening the extraction efficiency of deep eutectic solvents

At present, the composition of deep eutectic solvents (DESs) is usually screened by trial and error, which requires a lot of experimental time and reagent consumption. A hierarchical DESs screening method was proposed in this work and used to develop a fast, cost-effective, and pollution-free method to extract oleocanthal from extra virgin olive oil (EVOO). The extractive performance of 220 DESs were predicted by the thermodynamic model Conductor-like Screening Model for Segment Activity Coefficient (COSMO-SAC), while their melting point (Tm) and viscosity (η) were evaluated by the regressed solid–liquid equilibria (SLE) diagram and Quantitative Structure-Property Relationship (QSPR) models, respectively. Choline chloride (ChCl)/phenol was found to be the best DES candidate due to its high infinite dilution distribution ratio of oleocanthal (C∞=1.89g/g) and excellent physical properties (Tm=243.02 K and η=39.70cP). The screening results were confirmed by comparing the predicted thermophysical properties with the experimental ones and the extraction conditions were optimized. The extraction efficiency of oleocanthal was 59.54 μg/g, higher than the acetonitrile (19.90%) and conventional DES methods composed of ChCl, xylitol and water (21.94%), significantly reduced the solvent consumption and extraction duration. The flexible and reliable DESs screening models established in this paper can reduce the experimental workload, and provides a new idea for the efficient extraction of trace components, which has extensive reference significance.

Intelligent modeling of the hydrogen sulfide removal by deep eutectic solvents for the environmental protection

Hydrogen sulfide (H2S) is an acidic gas which produces by both natural (hot spring, volcano, microorganism decomposition) and industrial (biogas production, natural gas, liquefied petroleum gas, and oil refineries) processes. Due to the highly toxic and corrosive nature of H2S, researchers continuously search to find a practical scenario for its elimination from gas and liquid mixtures. Hydrogen sulfide absorption by deep eutectic solvents (DES), has recently found considerable attention, mainly in laboratory-scale investigations. Despite a relatively comprehensive experimental analysis of H2S absorption by DESs, there is no reliable empirical or intelligent methodology to predict the amount of this removal. Thus, the current study utilizes three machine learning classes (i.e., artificial neural network, support vector regression, and hybrid neuro-fuzzy system) to estimate the amount of H2S removal by 18 different DESs. The DES composition and operating conditions are the independent variables of these intelligent tools. The relevancy analysis approves that the amount of absorbed H2S by DESs is mainly controlled by hydrogen bond acceptor type, pressure, and temperature. Statistical and graphical analyses approve that the hybrid neuro-fuzzy system (hybrid NFS) is the highest accurate model to estimate the DES-H2S phase equilibria. The hybrid NFS predicts 495 experimental samples of H2S removal by DESs with the AARD = 6.11 %, MAE = 0.064, RAE = 5.64 %, MSE = 0.0149, and R-value = 0.99709. The combination of [C1-TMHDA]Ac and acetamide (1:2) is the best DES to achieve the maximum level of H2S elimination.

Chitosan films plasticized with choline-based deep eutectic solvents: UV shielding, antioxidant, and antibacterial properties

Deep eutectic solvents (DES) as plasticizers of chitosan film show great potential for food packaging. This paper introduced some novel antioxidant and antibacterial films based on chitosan and DES consisting of choline chloride (ChCl) and organic acids. The effects of the composition and contents of choline-based DES on structures, mechanical properties, thermal stability, contact angle, optical, antioxidant and antibacterial properties of chitosan films were studied. FTIR analysis showed that choline-based DES did exist in the chitosan film with good polymer matrix compatibility. Most of the films exhibited uniform, flat surfaces and cross sections. The Young's modulus of the films decreased inversely to the level of choline-based DES, and maximal mechanical characteristics were achieved for films plasticized with ChCl and acetylsalicylic acid. The addition of choline-based DES apparently reduced water contact angles, decreased the decomposition temperature and the thermal stability of chitosan films. In terms of antioxidant capacities and ultraviolet (UV) shielding, chitosan films plasticized with choline-based DES containing acetylsalicylic acid and vitamin C had strong UV shielding and antioxidant properties. Chitosan films plasticized with choline-based DES containing acetylsalicylic acid, malonic acid and lactic acid showed excellent antibacterial properties against Escherichia coli and Staphylococcus aureus . In conclusion, the chitosan film with the choline-based DES, especially for ChCl and acetylsalicylic acid showed a good application prospect in food active packaging. Chitosan films plasticized with choline-based deep eutectic solvents: UV shielding, antioxidant, and antibacterial properties. • Novel chitosan films plasticized with 6 kind of deep eutectic solvents (DES) and 2 different levels addition were studied. • Chitosan films plasticized with choline-based DES containing acetylsalicylic acid or vitamin C had strong ultraviolet shielding and antioxidant activities. • Chitosan films plasticized with choline-based DES containing acetylsalicylic acid, malonic acid or lactic acid showed excellent antibacterial properties.

Subzero-temperature homogeneous liquid-liquid extraction for the stereoselective determination of chiral triadimefon and its metabolite in water, fruit juice, vinegar, and fermented liquor by HPLC.

A novel method based on homogeneous liquid-liquid extraction with deep eutectic solvents (DES) under subzero-temperature conditions in combination with high performance liquid chromatography (HPLC) for the determination of chiral fungicide triadimefon (TF) and its metabolite triadimenol (TN) in water, fruit juice, vinegar, and fermented liquor was developed in this study. The method involved using deep eutectic solvents (DES) under subzero-temperature conditions in combination with high performance liquid chromatography (HPLC). This novel technique, known as subzero-temperature homogeneous liquid-liquid extraction (STHLLE), offers several advantages, including high efficiency, time-saving, low-cost, and eco-friendliness. The enantiomers of chiral TF and TN were simultaneously separated and quantified using HPLC coupled with a Daicel Chiralpak OD-RH column. Various experimental parameters such as DES composition and volume, freezing condition, salt concentration, and pH were optimized to enhance the recoveries of the target analytes. Under the optimized conditions, spiked recoveries of six enantiomers (i.e., S-TF, R-TF, SR-TN, RS-TN, SS-TN, and RR-TN) in the water, fruit juice, vinegar, and fermented liquor samples were 82.2-100.1% with relative standard deviations of 0.4-10.1%. The current method demonstrated a detection range of 0.03-0.06 mg L-1 in the target analytes. This established technique exhibits potential for efficient and precise extraction and quantification of the enantiomers of TF and TN in water phase samples.

Carbon dioxide capture and its electrochemical reduction study in deep eutectic solvent (DES) via experimental and molecular simulation approaches

Electrochemical reduction of carbon dioxide (ERCO2) is one of the potential ways to tackle the problems associated with climate change due to this greenhouse gas. However, poor solubility of CO2 in the commonly used aqueous as well as organic electrolytes limits the availability of CO2 at the electrode surface for its efficient capture and conversion. In this regard, deep eutectic solvents (DES) offer new avenues to enhance the electrochemical reduction of carbon dioxide due to very good solubility of CO2 (1.3 mol CO2/mol DES; 329 K, 76.5kPa) in DES, which is tuneable with the DES composition. Nevertheless, the understanding about the mechanistic aspects of capture and electrochemical conversion of CO2 in DES are not clearly understood. Herein, we present the results from our systematic theoretical plus experimental investigations on CO2 capture and electrochemical conversion using a DES, i.e. Ethaline. Ethaline when used as electrolyte at gold sheet working electrode reveals enhanced current response, reduced charge transfer resistance, and lowering of the overpotential by 440 mV as compared to DMF (dimethyl formamide). The CO2 electrolysis in Ethaline gives CO as the main product with a high faradic efficiency of 81.8%. The theoretical studies using Molecular Dynamics (MD) simulation was performed to investigate the microscopic properties of the DES along with its ability for CO2 capture.

Controllable recovery and recycling of carboxylic acid-polyalcohol deep eutectic solvent for biomass pretreatment with electronically-controlled chemical methodology

Pretreatment of lignocellulosic biomass using deep eutectic solvent (DES) has been demonstrated environmental and valid. Co-existing of donor and acceptor of hydrogen bond makes DES composition more complicated than traditional solvents, which limits their further scale-up utilization. Advances in biomass pretreatment using green solvent DES should excogitate efficient methodology for DES recycling. Electronically-controlled chemical methodology was first put forward to resolve recovery and recycling issue of DES lactic acid-ethylene glycol after biomass pretreatment. The methodology worked based on selectively migrating of lactate Lac- and reserving of ethylene glycol using BP-A-BP bipolar membrane electrodialysis (BMED). Impact of primary factors on DES recovery was carefully studied. Lowest energy consumption for specific DES recovery reached 10.4 kw·h/kg and highest DES recovery rate approached 97.6 %. Cognition acquired from this research indicated a promising and efficient strategy for carboxylic acid-polyalcohol DES recovery with novel electronically-controlled chemical methodology.

Water Miscibility, Surface Tension, Density, and Dynamic Viscosity of Hydrophobic Deep Eutectic Solvents Composed of Capric Acid, Menthol, and Thymol

Deep eutectic solvents (DESs) are rapidly emerging as environmentally benign and viable alternatives not only to common organic solvents but to relatively toxic ionic liquids as well. By judicious selection of the constituents and subsequent variation in their composition, the key physicochemical properties of the DESs can be easily tailored for a specific application. Impact of variation in constituents as well as their composition on important physical properties of natural DESs (NADESs) prepared using a common fatty acid n-decanoic acid (DA) and two naturally occurring monoterpenoids, thymol (Thy) and L(−)-menthol (Men), is assessed. Specifically, water miscibility, surface tension, density, and dynamic viscosity of 17 different DESs of three combinations of constituents, Men:DA, Thy:DA, and Thy:Men in four, four, and nine compositions, respectively, are measured. The water intake by the DESs under ambient conditions varies from 0.6 to 2.7 mol·kg–1 offering a means to gauge their hydrophobicity. Water miscibility is relatively lower for Men:DA DESs and higher for Thy:DA DESs. Surface tension values are within 28.37 mN·m–1 to 31.14 mN·m–1 under ambient conditions; they are higher for the DESs with the Thy constituent and vary systematically with DES composition. The densities of all the DESs are lower than that of water and decrease linearly with increasing temperature. While density does not vary with composition for Men:DA, it is found to increase linearly with an increase in Thy mole fraction for Thy:DA and Thy:Men DESs. The dynamic viscosity of the DESs are relatively lower as compared to the common tetralkylammonium salt- and metal salt-based DESs, and exhibit strong constituent and composition dependence. Rather than the Arrhenius-type expression, the temperature-dependence of the dynamic viscosity better conforms to the Vogel–Fulcher–Tammann (VFT) model with activation energy of the viscous flow varying systematically with the constituent and composition. Reported physical properties and their dependence on constituents/composition of the NADESs will enhance their utility and help establish them as novel alternate media in science and technology.