Deep Eutectic Solvents Composition Research Articles

Design of a novel deep eutectic solvent for microextraction of Lissamine green B from food Samples: A green approach

The extraction of Lissamine Green B (LGB) from food matrices poses a challenge due to its low concentration and interference from other matrix compounds. In this study, a novel green approach utilizing a deep eutectic solvent (DES) for dispersive liquid microextraction (GDES- DLLME) of LGB is presented. The DES, formulated from eco-friendly components and synthesized through mechanochemical methods for the first time, presents a sustainable alternative to traditional solvents. The DES characterization was implemented via 1H and 13C Nuclear Magnetic Resonance spectroscopy (NMR) analysis. The microextraction procedure was optimized for maximum efficiency, considering factors such as extraction time, DES composition, and sample pH, THF volume, NaCl amount, sample volume etc. The developed method was then applied to various food samples using spectrophotometric detection for the quantitative analysis of LGB, including water samples, beverages and foods. Furthermore, analytical performance values such as limit of detection (LOD), limit of quantification (LOQ), relative standard deviation (RSD), and preconcentration factor (PF) were calculated as 0.76 ng/mL, 2.56 ng/mL, % 4.6, and 22.5 respectively. The results demonstrated the effectiveness of simply generated DES as an extraction solvent and enabled sensitive and selective determination of LGB in complex food matrices. This eco-friendly method is promising for food safety and quality control applications, providing a sustainable solution for the analysis of LGBs in food.

Biotransformation of ginsenoside compound K using β-glucosidase in deep eutectic solvents.

Ginsenoside compound K (CK) holds significant potential for application in the pharmaceutical industry, which exhibits numerous pharmacological activity such as cardioprotective and antidiabetic. However, the difficult separation technique and limited yield of CK hinder its widespread use. The study investigated the process of converting ginsenoside CK using β-glucosidase. It aimed to determine the specific site where the enzyme binds and the most favorable arrangement of the enzyme. Molecular docking was also employed to determine the interaction between β-glucosidase and ginsenosides, indicating a strong and spontaneous contact force between them. The effectiveness of the conversion process was further improved using a "green" deep eutectic solvent (DES). A univariate experimental design was used to determine the composition of DES and the optimal hydrolysis conditions for β-glucosidase to convert ginsenoside Rb1 into ginsenoside CK. The employment of β-glucosidase enzymatic hydrolysis in the synthesis of rare ginsenoside CK applying the environmentally friendly solvent DES is not only viable and effective but also appropriate for industrial use. The characterization methods confirmed that DES did not disrupt the structure and conformation of β-glucosidase. In ChCl:EG = 2:1 (30%, v/v), pH 5.0 of DES buffer, reaction temperature 50 ℃, enzyme substrate mass ratio 1:1, after 36h of reaction, the CK yield was 1.24 times that in acetate buffer, which can reach 86.2%. In this study, the process of using β-glucosidase enzymatic hydrolysis and producing rare ginsenoside CK in green solvent DES is feasible, efficient and suitable for industrial production and application.

Green Extraction of Reed Lignin: The Effect of the Deep Eutectic Solvent Composition on the UV-Shielding and Antioxidant Properties of Lignin.

Lignin, the second most abundant natural polymer, is a by-product of the biorefinery and pulp and paper industries. This study was undertaken to evaluate the properties and estimate the prospects of using lignin as a by-product of the pretreatment of common reed straw (Phragmites australis) with deep eutectic solvents (DESs) of various compositions: choline chloride/oxalic acid (ChCl/OA), choline chloride/lactic acid (ChCl/LA), and choline chloride/monoethanol amine (ChCl/EA). The lignin samples, hereinafter referred to as Lig-OA, Lig-LA, and Lig-EA, were obtained as by-products after optimizing the conditions of reed straw pretreatment with DESs in order to improve the efficiency of subsequent enzymatic hydrolysis. The lignin was studied using gel penetration chromatography, UV-vis, ATR-FTIR, and 1H and 13C NMR spectroscopy; its antioxidant activity was assessed, and the UV-shielding properties of lignin/polyvinyl alcohol composite films were estimated. The DES composition had a significant impact on the structure and properties of the extracted lignin. The lignin's ability to scavenge ABTS+• and DPPH• radicals, as well as the efficiency of UV radiation shielding, decreased as follows: Lig-OA > Lig-LA > Lig-EA. The PVA/Lig-OA and PVA/Lig-LA films with a lignin content of 4% of the weight of PVA block UV radiation in the UVA range by 96% and 87%, respectively, and completely block UV radiation in the UVB range.

A designed ZrOCl2/ethylene glycol deep eutectic solvent for efficient lignocellulose valorization

Deep eutectic solvents (DESs) hold great potential in biorefining because they can efficiently deconstruct the recalcitrant structure of lignocellulose. In particular, inorganic salts with Lewis acids have been proven to be effective at cleaving lignin–carbohydrate complexes. Herein, a Zr-based DES system composed of metal chloride hydrate (ZrOCl2·8H2O) and ethylene glycol (EG) was designed and used for poplar powder pretreatment. Zr4+-based salts provide sufficient acidity for lignocellulose depolymerization. The acidity of the DES was analysed by the Kamlet-Taft solvatochromic parameter, and the results demonstrated that the acidity can be regulated by the DES composition. Under the optimum conditions (ZrOCl2·8H2O:EG molar ratio of 1:2), the DES pretreatment removes nearly 100 % hemicellulose and 94.7 % lignin. The recovered lignin exhibited a low polydispersity of 1.7. The cellulose residues deliver an efficiency of 94.4 % upon enzymatic digestion. Moreover, the DES can be easily recovered with high yield and purity, and the recycled DES still maintains high delignification and enzymatic hydrolysis efficiencies. The proposed DES pretreatment technology is promising for biomass valorization.

Enhanced Antioxidant Extraction from Lonicerae japonicae Flos Based on a Novel Optimization Strategy with Tailored Deep Eutectic Solvents

Lonicerae japonicae Flos (LJF) is a natural plant containing abundant antioxidant ingredients. In order to extract more antioxidants from LJF, in this study, a novel strategy was proposed for optimizing the extraction factor level by response surface methodology with a tailored deep eutectic solvent (DES) as the extraction solvent and antioxidant ability as the evaluation index. After optimizing the composition of DES and the extraction condition, the extracts obtained by our proposed method yielded better antioxidant ability (229.1–249.1 μmol TE/g DW) and higher antioxidant contents (34.2–36.5 mg GAE/g DW for total phenolics and 119.6–123.0 mg RE/g DW for total flavonoids) from LJF in 5 min without organic solvent consumption that were significantly superior to the Chinese Pharmacopoeia extraction method. The K-T solvation parameter and a scanning electron microscope were adopted to explore the extraction mechanism, and the results showed that the polarity and damage effect on plant cells of DES were crucial for the extraction of antioxidants. In addition, after combining the HPLC fingerprint and partial least squares model, chlorogenic acid, rutin, and 3,5-O-Dicaffeoylquinic acid were screened as the antioxidant Q-markers of LJF. This work demonstrates that an optimization strategy based on antioxidant ability and tailored DES has the potential to extract more antioxidants from natural plants.

Efficient and promising oxidative desulfurization of fuel using Fenton like deep eutectic solvent

Oxidative desulfurization (ODS) has emerged as a prominent technique for the removal of sulfur compounds from fuels, aiming to comply with stringent environmental regulations and minimize sulfur dioxide emissions. Herein, Fenton-like deep eutectic solvents (DESs) were synthesized as a catalyst and reaction medium and their application for the ODS process was investigated. The study encompassed the optimization of DES composition, reaction conditions, and the influence of different parameters on the desulfurization efficiency. The experimental findings demonstrated that the Fenton-like DES exhibited outstanding catalytic activity in the oxidative desulfurization of fuel. The optimized conditions involved conducting the reaction at room temperature for 2.5 h, using 200 mg of the prepared DES (HNFM-FeCl4) as both the extraction solvent and catalyst. An oxidant-to-sulfur (O/S) ratio of approximately 3:1 was maintained, with a 30 wt% H2O2 solution utilized as the oxidant. The analysis of the reaction products using GC–MS revealed a remarkable yield of 98% for dibenzothiophene sulfone. The DES provided a suitable medium for the reaction, enhancing the solubility and availability of sulfur compounds. The iron catalyst, in the presence of hydrogen peroxide, facilitated the oxidation of sulfur-containing compounds to their corresponding sulfones, which can be easily separated from the fuel phase. The DES catalysts exhibited stability and recyclability, making them suitable for practical applications in fuel desulfurization processes.

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.

Unravelling the stabilization mechanism of mono-, di- and tri-cholinium citrate-ethylene glycol DESs towards α-chymotrypsin for preservation and activation of the enzyme.

Deep eutectic solvents (DESs) are considered as designer solvents that serve as alternatives to traditional solvents. Numerous favourable properties and advantageous characteristics promote their utility in bio-catalysis. Therefore, they have emerged as attractive sustainable media for different biomacromolecules. In the present work, we have synthesized cholinium-based DESs having a hydrogen bond acceptor (HBA) : hydrogen bond donor (HBD) molar ratio of 1 : 2 by varying the cationic ratio in the HBA, which led to the formation of the DESs such as monocholinium citrate ([Chn][Cit]), dicholinium citrate ([Chn]2[Cit]) and tricholinium citrate ([Chn]3[Cit]), keeping the HBD ethylene glycol (EG) constant to study their suitability for α-chymotrypsin (α-CT). Herein, we have systematically evaluated the influence of DES-1 ([Chn][Cit]-[EG]), DES-2 ([Chn]2[Cit]-[EG]) and DES-3 ([Chn]3[Cit]-[EG]) on the structural and thermal stability, thermodynamic profile, colloidal stability and enzymatic activity of α-CT using different spectroscopic techniques. The spectroscopic results explicitly show enhanced structural stability and activity of the enzyme as the cationic ratio in the HBA increases. Fascinatingly, temperature-dependent studies through both fluorescence and activity measurements showed that DES-2 and DES-3 have highly beneficial effects on α-CT stability. The transition temperature (Tm) of α-CT was augmented by 12.0 °C in DES-2, 10.0 °C in DES-3 and 9.1 °C in DES-1 when compared to the enzyme in buffer. Furthermore, transmission electron microscopy (TEM) analysis revealed that the morphology of α-CT in DES-2 and DES-3 closely mirrored the structure of α-CT, while DES-1 exhibited only minor structural deviations. These findings were corroborated by hydrodynamic size (dH) measurements and average decay time analysis, which confirmed the observed morphological similarities and perturbations. The long-term preservation ability and kinetics of DES-3 were eventually confirmed by Michaelis-Menten kinetics. Ultimately, these outcomes demonstrate that increasing the molar ratio of the cholinium cation in the HBA can enhance the ability of DESs to stabilize the α-CT structure. Our results also suggest that the effect imparted by DESs was due to DESs themselves rather than their constituent elements. Altogether, the present investigation provides a new insight into the dependence of protein's stability and conformational alterations on DES composition. Also, the biocompatibility of DESs towards enzymes can be varied by changing the molar ratios of the constituent components of DESs to facilitate the expansion of applicability of DESs in biocatalysis.

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.