Acid-based Deep Eutectic Solvents Research Articles

Acid-based deep eutectic solvents followed by GFAAS for the speciation of As(III), As(V), total inorganic arsenic and total arsenic in rice samples

In the present study, an efficacious, safe, inexpensive and eco-friendly microextraction was provided by deep eutectic solvents based on dispersive liquid–liquid microextraction (DLLME − DES) followed by GFAAS. A series of DESs were synthesised using l-menthol as hydrogen bond acceptor (HBA) and carboxylic acids with 4, 6, 8 and 10 carbon atoms as hydrogen bond donors (HBD). The synthesised DESs were used as extractants of arsenic ions. Under optimised conditions, good linearity with coefficient of determination (r 2) 0.992 and an acceptable linear range of 0.3–100 µg kg−1 was obtained. The limit of detection was 0.1 µg kg−1 (S/N = 3) for arsenite (As(III)) ions, and a high enrichment factor (EF = 200) was obtained. The enhancement factor and extraction recovery (ER%) of the method were 340 and 60%, respectively. RSDs including inter- and intra-day ranged from 3.2% to 5.8% in three examined concentrations. After a specific digestion, the capability of the synthesised DES in the extraction of As(III) from rice was tested. Total inorganic arsenic was separated similarly after reduction of arsenate (As(V)) to As(III), and As(V) concentration was calculated by difference. Using a second digestion method, total arsenic concentration (sum of organic and inorganic arsenic) in the samples was determined.

Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents.

The glass formation and the dipolar reorientational motions in deep eutectic solvents (DESs) are frequently overlooked, despite their crucial role in defining the room-temperature physiochemical properties. To understand the effects of these dynamics on the ionic conductivity and their relation to the mechanical properties of the DES, we conducted broadband dielectric and rheological spectroscopy over a wide temperature range on three well-established carboxylic acid-based natural DESs. These are the eutectic mixtures of choline chloride with oxalic acid (oxaline), malonic acid (maline), and phenylacetic acid (phenylaceline). In all three DESs, we observe signs of a glass transition in the temperature dependence of their dipolar reorientational and structural dynamics, as well as varying degrees of motional decoupling between the different observed dynamics. Maline and oxaline display a breaking of the Walden rule near the glass-transition temperature, while the relation between the dc conductivity and dipolar relaxation time in both maline and phenylaceline is best described by a power law. The glass-forming properties of the investigated systems not only govern the orientational dipolar motions and rheological properties, which are of interest from a fundamental point of view, but they also affect the dc conductivity, even at room temperature, which is of high technical relevance.

Natural Deep Eutectic Solvents as Rust Removal Agents from Lithic and Cellulosic Substrates.

The peculiar physicochemical features of deep eutectic solvents (DESs), in particular their tunability, make them ideal media for various applications. Despite their ability to solubilize metal oxides, their use as rust removers from valuable substrates has not yet been thoroughly investigated. In this study, we chose three known DESs, consisting of choline chloride and acetic, oxalic or citric acid for evaluating their ability to remove corrosion products from a cellulose-based material as linen fabric and two different lithotypes, as travertine and granite. The artificial staining was achieved by placing a rusty iron grid on their surfaces. The DESs were applied by means of cellulose poultice on the linen fabrics, while on the rusted stone surfaces with a cotton swab. Macro- and microscopic observations, colorimetry and SEM/EDS analysis were employed to ascertain the cleaning effectiveness and the absence of side effects on the samples after treatment. Oxalic acid-based DES was capable of removing rust stains from both stone and cellulose-based samples, while choline chloride/citric acid DES was effective only on stone specimens. The results suggest a new practical application of DESs for the elimination of rust from lithic and cellulosic substrates of precious and artistic value.

Dissolving and Efficient Fractionation of Chitin and Synchronous Preparation of Calcium Lactate from Crayfish Shell Waste Using Amino Acid-Based Deep Eutectic Solvents

Dissolving and Efficient Fractionation of Chitin and Synchronous Preparation of Calcium Lactate from Crayfish Shell Waste Using Amino Acid-Based Deep Eutectic Solvents

Efficient synthesis of novel thiadiazolo[2,3-b]quinazolin-6-ones catalyzed by diphenhydramine hydrochloride-CoCl2⋅6H2O deep eutectic solvent

In this research, a new Lewis acid-based deep eutectic solvent (LA-DES) was synthesized using diphenhydramine hydrochloride and CoCl2·6H2O, (2[HDPH]:CoCl42−), and identified by FT-IR and 1HNMR techniques. The physicochemical properties of this LA-DES, such as thermal behavior, thermal stability, and solubility in common solvents were also investigated. The catalytic ability of 2[HDPH]:CoCl42− was ascertained in the efficient synthesis of a novel array of thiadiazolo[2,3-b]quinazolin-6-one scaffolds via a one-pot three-component reaction of dimedone/1,3-cyclohexanedione, aldehydes, and 5-aryl-1,3,4-thiadiazol-2-amines/3-(5-amino-1,3,4-thiadiazol-2-yl)-2H-chromen-2-one under solvent-free conditions. This catalyst was also successfully utilized for the synthesis of mono- and bis-thiadiazolo[2,3-b]quinazolin-6-ones from dialdehydes or bis-1,3,4-thiadiazol-2-amine. The simplicity of enforcement, short reaction time, avoidance of toxic organic solvents, scalability of the synthesis procedure, excellent atom economy, high reaction mass efficiency, and low E-factor are other outstanding advantages of this newly developed method. Furthermore, due to the convenient recovery and reuse of LA-DES, this protocol is economically justified and environmentally friendly.

Corrosion inhibition activity of a natural polysaccharide from Dysosma versipellis using tailor-made deep eutectic solvents

In this work, a total of 18 types of choline chloride, betaine, and L-proline-based deep eutectic solvents (DESs) were synthesized to determine the extraction yield of a natural polysaccharide (PSA) from Dysosma versipellis using an ultrasound-assisted extraction method. Results indicate that the choline-oxalic acid-based DES has the best extraction yield for PSA due to the proper physical-chemical properties between PSA and DES. To evaluate the optimal extraction conditions, a response surface methodology was carried out. Under the optimal conditions, the extraction yield of PSA reaches 10.37 % (± 0.03 %), higher than the conventional extraction methods. Findings from FT-IR and NMR suggest that the extracted PSA belongs to a neutral polysaccharide with (1 → 6)-linked α-d-glucopyranose in the main chain. Interestingly, results from various electrochemical measurements show the extracted PSA exhibits excellent corrosion inhibition performance for mild steel (MS) in a 0.5 M HCl solution, with 90.8 % of maximum corrosion inhibition efficiency at 210 mg L−1. SEM and XPS measurements reveal the formation of a protective layer on the MS surface. The adsorption behaviour of extracted PSA well obeys the Langmuir adsorption isotherm containing the chemisorption and physisorption. Additionally, theoretical calculations validate the experimental findings.

The protocatechuic acid-based deep eutectic solvent-mediated green synthesis of 1,2,4,5-tetrasubstituted imidazoles.

A novel protocatechuic acid-based deep eutectic solvent (ETPPBr/PCA-DES) was prepared by mixing ethyltriphenylphosphonium bromide (ETPPBr) and protocatechuic acid (PCA = 3,4-dihydroxybenzoic acid), and its structure was fully investigated by using the FT-IR, TGA/DTA, densitometer, eutectic point and 1H NMR techniques. Different molar ratios of ETPPBr to PCA were examined and the eutectic point phase diagram showed that the best ratio for the synthesis of the new DES is the one-to-one ratio of the two starting materials (ETPPBr and PCA). Then, the novel DES was used as a new and capable catalyst for the green synthesis of diverse 1,2,4,5-tetrasubstituted imidazoles a1-a12 from the four-component condensation reaction of phenanthrene-9,10-dione, aromatic amine, aromatic aldehyde, and ammonium acetate with high yields and very short reaction times. High yields and very short reaction times are two advantages of our proposed method compared with the previous reported methods.

Green synthesis approach using deep eutectic solvents to enhance the surface functional groups on porous carbon for CO2 capture

This study explores the potential of green solvents using amino acids-based deep eutectic solvents to alter surface functionality of activated carbon thus enhancing the carbon dioxide (CO2) adsorption capacity. Green solvent is prepared by mixing an amino acid (L-Arginine) with ethylene glycol to form amino acid-based deep eutectic solvents. Amino acid-based deep eutectic solvents were used to modify the surface functionalities of activated carbon derived from palm shell waste. The change in surface functional groups and surface morphology of the modified activated carbon samples were characterized by Fourier-transform infrared spectroscopy and Scanning electron microscopy-energy dispersive X-ray analysis. Then, CO2 removal performance was performed using a packed-bed CO2 adsorption reactor to evaluate CO2 breakthrough time and adsorption capacity. CO2 adsorption experiments were measured at a certain temperature (25–45°C), at a fixed feed flow rate and CO2 concentration of 200 mL/min and 15%. It was observed that modified activated carbon showed the highest breakthrough time (15.2 min) compared to raw palm shell (5.2 min) at an adsorption temperature of 25°C. CO2 breakthrough times significantly decreased with increasing adsorption temperature because of physical adsorption.

Ultrasonic-Assisted Extraction of Antioxidants from Perilla frutescens Leaves Based on Tailor-Made Deep Eutectic Solvents: Optimization and Antioxidant Activity.

The development of natural antioxidants to replace synthetic compounds is attractive. Perilla frutescens leaves were proven to be rich in antioxidants. The extraction of antioxidants from Perilla leaves via ultrasonic-assisted extraction (UAE) based on choline chloride-based deep eutectic solvents (DESs) was studied. Firstly, several DESs were prepared, and their extraction effects were compared. Secondly, the extraction process was optimized by single-factor experiments and response surface methodology (RSM). Finally, the optimization results were verified and compared with the results of traditional solvent-based UAE. The effects of solvents on the surface cell morphology of Perilla frutescens leaves were characterized by scanning electron microscopy (SEM). Choline chloride-acetic acid-based DES (ChCl-AcA) extract showed a relatively high ferric-reducing antioxidant activity (FRAP) and 2,2-diphenyl-1-picrylhyldrazyl radical scavenging rate (DPPH). Under the optimal operating conditions (temperature 41 °C, liquid-solid ratio 33:1, ultrasonic time 30 min, water content 25%, ultrasonic power 219 W), the experimental results are as follows: DPPH64.40% and FRAP0.40 mM Fe(II)SE/g DW. The experimental and predicted results were highly consistent with a low error (<3.38%). The values of the DPPH and FRAP were significantly higher than that for the water, ethanol, and butanol-based UAE. SEM analysis confirmed that ChCl-AcA enhanced the destruction of the cell wall, so that more antioxidants were released. This study provides an eco-friendly technology for the efficient extraction of antioxidants from Perilla frutescens leaves. The cytotoxicity and biodegradability of the extract will be further verified in a future work.

Developing amino acid-citric acid-based deep eutectic solvent for food applications: Preparation, characterization, antibacterial activity, biosafety, and formation mechanism exploration

The deep eutectic solvent (DES) is a novel environmentally-friendly solvent that shows promising potential for applications in the field of functional food. However, the current development of choline-based DESs faces limitations due to their toxicity levels, which restrict their application in the food industry. Therefore, in this study, amino acid (AA)-citric acid (CA) DESs suitable for functional food applications were developed using natural food additives as raw materials. The purity and thermodynamic properties of the AA-CA DESs were characterized by simultaneous thermogravimetry/differential scanning calorimetry (TG-DSC) and DSC analysis. The molecular interactions within the AA-CA DESs were investigated using FT-IR, NMR, and molecular dynamics (MD) simulations. The rheometer was used to study the viscosity of AA-CA DESs. The density of the AA-CA DESs was tested using a pycnometer and mutually verified with MD simulations. The antibacterial activity and biological safety of DESs were investigated by bacteriostatic and cell experiments. FT-IR, NMR, and MD simulations studies indicated that AA-CA DESs primarily form through hydrogen bonding interactions. Antibacterial experiments demonstrated that AA-CA DESs exhibited significantly enhanced antibacterial activity against P. aeruginosa and E. coli compared to pure substrates Gly, Ala, and Arg, respectively, indicating improved antibacterial properties. The cell experiments showed that AA-CA DESs possess good biological safety. In conclusion, this study successfully developed a class of AA-CA DESs and found that AA-CA DESs have good antibacterial activity and biosafety. This finding provides theoretical guidance for the sustainable development and application of DESs in the field of functional foods.

Malic acid-based deep eutectic solvent and its application in Insulin's structural stability

Deep eutectic solvents (DESs) and Ionic Liquids (ILs) have been recently used as a solvent for insulin delivery via subcutaneous, transdermal, oral, and nasal ways. However, due to their high viscosity, DESs are usually impractical for delivery applications in their pure solution. The addition of water decreases the viscosity of DESs, but it can also influence the structural stability of the proteins. Hence, DES-water solutions and their effect on insulin's structural stability need to be investigated. In this study, molecular dynamics simulations on insulin dimer in DES consisting of malic acid and choline chloride (MA-ChCl) with varying amounts of water were performed. Insulin is strongly stabilized in the DES and its aqueous solutions as compared to water. However, in the DES solutions with 50 % and 75 % water content, malic acid was observed to interact readily with insulin dimer and its binding site, causing the separation of the two monomers. Therefore, while the insulin dimer is stable in the DES with low water content, in the presence of higher amounts of water it is destabilized and the monomers are separated. Considering that insulin's active form is monomeric, and the decomposition of insulin into monomers before reaching the bloodstream can increase the pharmacokinetics of insulin delivery, the use of the aqueous DES for rapid insulin delivery is highly relevant.

One-step selective separation and efficient recovery of valuable metals from spent lithium batteries by phosphoric acid-based deep eutectic solvent

With more and more lithium-ion batteries (LIBs) being put into production and application, precious metals such as lithium and cobalt are scarce, so it is imminent to recover various strategic metal resources from spent LIBs. Meanwhile, the complex and difficult problem of separating and recovering metals from leaching solutions has been an urgent question that needs to be resolved. In this work, a phosphoric acid-based deep eutectic solvent (DES) was developed for extracting metals from spent LIBs and one-step selectively separating and efficiently recovering transition metal. The prepared DES shows excellent extraction performance for Li (100%) and Co (92.8%) at 100 °C. In addition, the extraction system can effectively separate and precipitate Co through its own components, avoiding the introduction of new precipitants and the destruction of the original composition structure of DES. This also contributes to the good cycle stability of the extraction system with excellent extraction performance for Li (94.3%) and Co (80.8%) after 5 cycles. This work proposes a green method for one-step selectively separating and recovering valuable metals from spent LIBs.

Optimization of experimental conditions for bioactive compounds recovery from raspberry fruits (Rubus idaeus L.) by using combinations of ultrasound-assisted extraction and deep eutectic solvents

Raspberry fruits (Rubus idaeus L.) have been reported to contain phenolic compounds, of which anthocyanins are the most abundant. A novel procedure of ultrasound-assisted extraction (UAE) using deep eutectic solvent (DES) for efficient extraction phenolic compounds and anthocyanins from raspberries is considered. Namely, the green approach for optimization by response surface methodology (RSM) based on Box-Behnken Design (BBD) was proposed in this study. Three carboxylic acid-based DES, like acetic acid/glucose (DESAAGLU), formic acid/glucose (DESFAGLU), and lactic acid/maltose (DESLAMA), were tested for their efficiency in the recovery of phenolic compounds and anthocyanins from raspberries. The optimum extraction parameters were obtained; extraction time of 60 min, a solvent volume of 35 mL, and added water on DES of 30 mL (v/v). The results of this study indicated that optimizing extraction conditions are critical for quantifying phenolic compounds and anthocyanins. The present model can contribute to finding a cheap way of delivering natural bioactive compounds in the food, cosmetic, and pharmaceutical industriesas well as a natural food colorant in dietary applications with potential health benefits.

Impact of water addition on fluctuation dynamics in viscous solvents with varied heterogeneity: A 2D IR spectroscopic study

The addition of cosolvent, such as water, influences the overall fluctuation dynamics as sensed by the probe. It is crucial to unravel the fluctuation dynamics when water is added, particularly in viscous solvents with varying degrees of heterogeneity. In this study, we employed two-dimensional infrared spectroscopy to examine the solvation dynamics of two viscous solvents: glycerol, a molecular solvent, and malicine, an acid-based deep eutectic solvent. Additionally, we explored the relative changes in fluctuation dynamics upon water addition. Our results indicate that water disrupts the hydrogen bond network in glycerol, but no significant effect is observed in malicine. Our experimental findings align well with previously reported simulation studies.

The gentisic acid-based deep eutectic solvent mediated green synthesis of acridines

A novel gentisic acid-based deep eutectic solvent (ETPPBr/GA-DES) was prepared by mixing of ethyltriphenylphosphonium bromide (ETPPBr) and gentisic acid (GA = 2,5-dihydroxy-benzoic acid), and its structure fully investigated by using the FT-IR, TGA/DTA, densitometer and 1HNMR techniques. Different mole ration of ETPPBr to GA were examined and the eutectic point phase diagram showed that the best ratio for the synthesis of a novel gentisic acid-based DES is the one-to-one mole ratio of the two starting materials (ETPPBr and GA).Then, ETPPBr/GA-DES was used as a novel and capable catalyst for the green synthesis of diverse N-substituted decahydroacridine-1,8-diones a(1−12) from the three-component condensation reaction of aromatic aldehyde, aromatic amine and dimedone in solvent-free conditions at 80 °C.

Development and validation of a deep eutectic solvent-assisted liquid-liquid extraction method for simultaneous quantification of six steroid hormones in serum by liquid chromatography-tandem mass spectrometry

Steroid hormones have been reported to be associated with endocrine system diseases. This paper proposes a novel procedure of deep eutectic solvent (DES)-assisted liquid–liquid extraction (LLE) to extract six steroid hormones (including cortisone, cortisol, androstenedione, testosterone, 17-hydroxyprogesterone, and progesterone) from serum coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of five types of L-proline, choline chloride, and citric acid-based DESs were tailored; the DES from L-proline and ethylene glycol at a molar ratio of 1:4 with 20 % acetonitrile was selected as the best-fit assisted solvent for the six steroid hormones compared with other DESs. The parameters for extraction by selected DES were optimized using Box-Behnken design (BBD), and the optimal extraction conditions are 200 µL of acetonitrile, 100 µL of the sample, and 80 µL of DES. Under optimum conditions, the method has good linear calibration ranges (between 0.07 ng mL−1 and 600 ng mL−1), correlation coefficients of determination (r2>0.99), and low limits of quantification (between 0.02 and 0.60 ng mL−1). The extraction recoveries were in the range of 81.84–114.43 %, and the intra-day and inter-day relative standard deviations (RSDs) were less than 10 %.In general, the DES-LC-MS/MS method is a simple and environmentally-friendly method, which can be complementary to the presently available methods for determining steroid hormones in serum.

Solvometallurgical recycling of spent LiNixCoyMnzO2 (NCM) cathode material using ternary choline chloride-ethylene glycol-p-toluenesulfonic acid deep eutectic solvent

In recent years, recycling lithium-ion batteries (LIBs) has become imperative considering their growing demand will soon lead to massive disposal of spent LIBs which causes critical environmental problems. In this study, solvometallurgy using deep eutectic solvents (DESs) is used to efficiently recover valuable metals from spent LIBs. The potential of different types of DES (binary and ternary) to leach LIB samples is evaluated. Initial leaching tests demonstrate that p-toluenesulfonic acid (PTSA) -based DES results in high metal extraction at 100 °C with 10 g/L pulp density and 72 h residence time. Cyclic voltammetry indicates a high current density of PTSA, a strong leaching agent in the DES structure. A ternary DES containing choline chloride, ethylene glycol, and p-toluenesulfonic acid (ChCl-EG-PTSA) show better performance as a leachant than other DESs. The formation of hydrogen bonds between p-toluenesulfonic acid-based DES components is examined by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. This study provides a new ternary DES for solvometallurgical recycling of LIBs while considering principles for sustainable development.

Comparative of malonic acid aqueous solution and malonic acid-based deep eutectic solvent for LiCoO2 cathode materials recovery: Leaching efficiency and mechanism

Deep eutectic solvents (DESs) and aqueous organic acids are two leaching systems that have achieved remarkable results in hydrometallurgical recovery of spent lithium-ion batteries (LIBs). However, previous studies have only evaluated a single leaching system at a time and thereby failed to compare the differences between DES and organic acids systems in detail. In this study, our purpose was to clarify the differences between the efficiencies of two leaching systems—a malonic acid (MA) aqueous solution and a DES of choline chloride: malonic acid (ChCl:MA) via a systematic investigation of the conditions and mechanisms associated with the leaching of LiCoO2 cathode materials using these two systems. The effects exerted by various process parameters, such as reaction time, temperature, and liquid-to-solid ratio, on the leaching efficiency of these two systems were investigated. The results showed that the Co and Li leaching efficiencies of the DES were higher than those of the MA aqueous solution under identical experimental conditions. The kinetic differences between the two systems were reflected in the fact that the MA aqueous solution was regulated by diffusion, whereas the DES leaching was regulated by chemical reactions. Spectroscopic analysis and density functional theory calculations indicated that MA acts as both a ligand and a reducing agent in aqueous solutions, whereas MA in the DES only acts as a reducing agent. In addition, Co was present in the MA aqueous and DES leaching solutions as octahedral (Co(H2O)2(C3H2O4)2) and tetrahedral ([CoCl4]2-), respectively.

The Novel Catalyst (Hypogallic Acid-Based Deep Eutectic Solvent) for Preparation of the New Compounds (Pyrano[2,3-d]Pyrimidines)

A novel Deep Eutectic Solvent (MTPPBr/HGA-DES) was prepared by a mixture of methyl triphenylphosphonium bromide (MTPPBr) and hypogallic acid (HGA: 2,3-dihydroxybenzoic acid). The eutectic point phase diagram showed that the one mole of MTPPBr to two moles of HGA is the best mole ratio for the synthesis of a novel DES. Then, MTPPBr/HGA-DES was characterized by the FT-IR, TGA/DTA, densitometer, eutectic points, and 1H NMR techniques, and used as a novel catalyst for the green synthesis of new pyrano[2,3-d]pyrimidines 2(a-j) via a one-pot four-component condensation reaction of 4-hydroxycoumarin, barbituric acid, morpholine and benzaldehydes at 80 °C in solvent-free conditions.

Sustainable extraction of polyphenols from vine shoots using deep eutectic solvents: Influence of the solvent, Vitis sp., and extraction technique

Vine shoots are the main by-products of grapevine pruning with no added value. In the present study, deep eutectic solvents (DESs) were used as alternatives to traditional chemical solvents, for the extraction of phytochemicals from grapevine shoots. Three levulinic acid-based DESs were tested for the first time, and their performance was compared to methanol (a standard chemical solvent) regarding the extraction of phenolic compounds from thirteen Vitis sp. shoots. Two extraction methods have been applied: ultrasound-assisted extraction and solid-liquid extraction. A total of eleven polyphenols which belongs to four families (proanthocyanins, stilbenes, hydroxycinnamic acids, and flavonols) have been identified and quantified in the extracts.The statistical analysis shows that the levulinic acid-based DES systems are novel and important alternatives to chemical solvents due to favourable eco-friendly properties and remarkable extraction performance of polyphenols. On the other hand, the ultrasound-assisted extraction technique has significantly increased the extraction rate in comparison to the solid-liquid extraction method with p-values lower than 0.05 for most compounds. The genetic factor has been shown to play an important role in the content of extracted polyphenols, being V. riparia pubescente the one that presented the highest concentrations of extracted polyphenols. Finally, the polyphenol-enriched extracts have proven important properties such as antioxidant activity and significant delay in bacteria growth against both gram-positive and gram-negative bacteria. It is important to note that, to the best of our knowledge, this is the first time that deep eutectic solvents have been used for the extraction of bioactive compounds from vine shoot residues.