Insight into the experiment and extraction mechanism for separating carbazole from anthracene oil with quaternary ammonium-based deep eutectic solvents

Carbazole is an irreplaceable basic organic chemical raw material and intermediate in industry.The separation of carbazole from anthracene oil by environmental benign solvents is important but still a challenge in chemical engineering.Deep eutectic solvents (DESs) as a sustainable green separation solvent have been proposed for the separation of carbazole from model anthracene oil.In this research,three quaternary ammonium-based DESs were prepared using ethylene glycol (EG) as hydrogen bond donor and tetrabutylammonium chloride (TBAC),tetrabutylammonium bromide or choline chloride as hydrogen bond acceptors.To explore their extraction performance of carbazole,the conductor-like screening model for real solvents (COSMO-RS) model was used to predict the activity coefficient at infinite dilution (γ^(∞)) of carbazole in DESs,and the result indicated TBAC:EG (1:2) had the stronger extraction ability for carbazole due to the higher capacity at infinite dilution (C^(∞)) value.Then,the separation performance of these three DESs was evaluated by experiments,and the experimental results were in good agreement with the COSMO-RS prediction results.The TBAC:EG (1:2) was determined as the most promising solvent.Additionally,the extraction conditions of TBAC:EG (1:2) were optimized,and the extraction efficiency,distribution coefficient and selectivity of carbazole could reach up to 85.74%,30.18 and 66.10%,respectively.Moreover,the TBAC:EG (1:2) could be recycled by using environmentally friendly water as antisolvent.In addition,the separation performance of TBAC:EG (1:2) was also evaluated by real crude anthracene,the carbazole was obtained with purity and yield of 85.32%,60.27%,respectively.Lastly,the extraction mechanism was elucidated byσ-profiles and interaction energy analysis.Theoretical calculation results showed that the main driving force for the extraction process was the hydrogen bonding ((N–H...Cl) and van der Waals interactions (C–H...O and C–H...π),which corresponding to the blue and green isosurfaces in IGMH analysis.This work presented a novel method for separating carbazole from crude anthracene oil,and will provide an important reference for the separation of other high value-added products from coal tar.

Oxidative Desulfurization of Fuel Oil with H_(3)PO_(4)-based Deep Eutectic Solvents

A series of Lewis-acid deep eutectic solvents (DESs) were synthesized by stirring phosphoric acid and zincchloride as raw materials at 80 °C to form H_(3)PO_(4)/nZnCl_(2) (n = 0.1, 0.25, 0.5, 0.75, 1). The DESs were characterized byFourier transform infrared spectrophotometry (FT-IR), thermogravimetry/differential thermogravimetry (TG/DTG), andelectron spray ionization mass spectrometry (ESI-MS). The DESs were used as both extractants and catalysts to removedibenzothiophene from fuels via oxidative desulfurization (ODS). Experiments were performed to investigated the influenceof factors such as composition of DES, temperature, oxidant dosage (molar ratio of O:S), DES dosage (volume ratio ofDES:oil), and number of cycles on desulfurization rate. The results indicated that the removal rate of dibenzothiophene (DBT)was affected by the Lewis acidic DESs, with that of H_(3)PO_(4)/0.25∙ZnCl_(2) reaching 96.4% under optimal conditions (Voil=5 mL,VDES=1 mL, an oxidant dosage of 6, T=50 ℃). After six cycles, the desulfurization rate of H_(3)PO_(4)/0.25∙ZnCl_(2) remained above94.1%. The apparent activation energy of dibenzothiophene (DBT) removal reaction was determined by a pseudo-first orderkinetic equation according to the Arrhenius equation to be 32.34 kJ/mol, as estimated. A reaction mechanism is proposedbased on the experimental data and characterization results.

Efficient and reversible separation of NH_(3) by deep eutectic solvents with multiple active sites and low viscosities

The efficient separation and collection of ammonia(NH_(3))during NH_(3) synthesis process is essential to improve the economic efficiency and protect the environment.In this work,ethanolammonium hydrochloride(EtOHACl)and phenol(PhOH)were used to prepare a novel class of deep eutectic solvents(DESs)with multiple active sites and low viscosities.The NH_(3) separation performance of EtOHACl+PhOH DESs was analyzed completely.It is figured out that the NH_(3) absorption rates in EtOHACl+PhOH DESs are very fast.The NH_(3) absorption capacities are very high and reach up to 5.52 and 10.74 mol·kg1 at 11.2 and 100.4 kPa under 298.2 K,respectively.In addition,the EtOHACl+PhOH DESs present highly selective absorption of NH_(3) over N_(2) and H_(2) and good regenerative properties after seven cycles of absorption/desorption.The intrinsic separation mechanism of NH_(3) by EtOHACl+PhOH DESs was further revealed by spectroscopic analysis and quantum chemistry calculations.

Research Progress of Deep Eutectic Solvents in Extraction of Plant Flavonoids

As a new type of green solvents,deep eutectic solvents(DESs)have the advantages of strong extraction ability,designability,simple preparation,low price,recoverability and biodegradation,and show great application potential in the field of plant flavonoid extraction.In this paper,the definition,classification and preparation methods of DESs were introduced.The effects of DES composition,molar ratio of DES components,water content of DES systems,liquid-material ratio,extraction temperature,extraction time and extraction auxiliary techniques on the extraction yield of plant flavonoids were expounded.The recycling methods of DESs were summarized.Existing problems of DESs in the field of plant flavonoids extraction were pointed out,and further research direction and trend were analyzed and prospected.

Enhancing effect of choline chloride-based deep eutectic solvents with polyols on the aqueous solubility of curcumin–insight from experiment and theoretical calculation

The development of green solvents for enhancing aqueous solubility of drug curcumin remains a challenge. This study explores the enhancing effect of deep eutectic solvents(DESs) on the aqueous solubility of curcumin(CUR) via experiment and theoretical calculation. Choline chloride-based DESs with polyols 1,2-propanediol(1,2-PDO), 1,3-propanediol, ethylene glycol, and glycerol as hydrogen bond donors were prepared and used as co-solvents. The CUR aqueous solubility increased with increasing the DESs content at temperature of 303.15-318.15 K, especially in aqueous ChCl/1,2-PDO(mole ratio 1:4) solutions. The positive apparent molar volume values and reduced density gradient analysis confirmed the existence of strong interactions between CUR and solvent. The van der Waals interactions and hydrogen bonding coexisted in DESs monomer retained the stability of DESs structure after introducing CUR. Moreover,the lower interaction energy of DESs…CUR system than that of the counterpart DESs further proved the strong interaction between CUR and DESs. The lowest interaction energy of ChCl/1,2-PDO…CUR system indicated that this system was the most stable and ChCl/1,2-PDO was promising for CUR dissolution.This work provides efficient solvents for utilizing curcumin, contributing to a deep insight into the interactions between DES and CUR at the molecular level, and the role of DESs on enhancing drugs solubility.

Volumetric and ultrasonic properties of thiamine hydrochloride drug in aqueous solutions of choline-based deep eutectic solvents at different temperatures

Important efforts have been made over the past years to improve the drug acts,which leads to the discovery of novel drug preparations and delivery systems.The optimal design of such processes requires a molecular-level understanding of the interactions between drug molecules and biological membranes.The thermodynamic investigation provides deep and complete knowledge of interactions and the choice of appropriate and suitable production compounds in pharmaceutical fields.Particularly,the analysis of drugs+co-solvents in aqueous media is the central issue in many types of research because they exert their impact by interacting with biological membranes.This work is aimed to measure the density and speed of sound for the thiamine hydrochloride in water+deep eutectic solvents(DESs)mixtures(choline chloride/urea,choline chloride/ethylene glycol and choline chloride/glycerol)at temperature range(293.15-308.15)K.By correlation of the evaluated parameters in some standard relations,the partial molar parameters i.e.apparent molar volumes,Vφ,m,and apparent molar isentropic compression,κ_(s,φ,m),are calculated.In addition,apparent molar isobaric expansion,E^(0)_(φ,m),and Hepler’s constant are computed from the density and speed of sound data.For fitting the experimental Vφ,m andκ_(s,φ,m)the Redlich-Meyer equation was employed that the important quantities;standard partial molar volume,V^(0)_(m),and partial molar isentropic compression,κφ,m0,were obtained.The thermodynamic analysis of the studied system also plays a crucial role in the pharmaceutical industry.

Intermolecular interactions induced property improvement for clean fracturing fluid by deep eutectic solvents

Fracturing fluid property play a critical role in developing unconventional reservoirs.Deep eutectic solvents(DESs)show fascinating potential for property improvement of clean fracturing fluids(CFFs)due to their low-price,low-toxicity,chemical stability and flexible designability.In this work,DESs were synthesized by mixing hydrogen bond acceptors(HBAs)and a given hydrogen bond donor(HBD)to explore their underlying influence on CFF properties based on the intermolecular interactions.The hydrogen-bonding,van der Waals and electrostatic interactions between DES components and surfactants improved the CFF properties by promoting the arrangement of surfactants at interface and enhancing the micelle network strength.The HBD enhanced the resistance of CFF for Ca^(2+) due to coordination-bonding interaction.The DESs composed of choline chloride(ChCl)and malonic acid show great enhancement for surface,rheology,temperature resistance,salt tolerance,drag reduction,and gel-breaking performance of CFFs.The DESs also improved the gel-breaking CFF-oil interactions,increasing the imbibition efficiencies to 44.2%in 74 h.Adjusting HBAs can effectively strengthen the intermolecular interactions(e.g.,HBA-surfactant and HBD-surfactant interactions)to improve CFF properties.The DESs developed in this study provide a novel strategy to intensify CFF properties.

An overview of deep eutectic solvents:Alternative for organic electrolytes,aqueous systems&ionic liquids for electrochemical energy storage

As the demand for sustainable energy sources continues to rise,the need for efficient and reliable energy storage systems becomes crucial.In order to effectively store and distribute renewable energy,new and innovative solutions must be explored.This review examines the deep eutectic solvents(DESs)as a green,safe,and affordable solution for the electrochemical energy storage and conversion field,offering tremendous opportunities and a promising future.DESs are a class of environment-friendly solvents known for their low toxicity and unique properties,such as their good conductivity,high thermal stability,and nonflammability.This review explores the fundamentals,preparations,and various interactions that often predominate in the formation of DESs,the properties of DESs,and how DESs are better than traditional solvents involving cost-ineffective and unsafe organic electrolytes and ionic liquids as well as inefficient aqueous systems due to low energy density for electrochemical energy storage applications.Then,a particular focus is placed on the various electrochemical applications of DESs,including their role in the electrolytes in batteries/supercapacitors,electropolishing and electrodeposition of metals,synthesis of electrode materials,recycling of electrodes,and their potential for use in CO_(2)capture.The review concludes by exploring the challenges,research gaps,and future potential of DESs in electrochemical applications,providing a comprehensive overview,and highlighting key considerations for their design and use.

Efficient and selective extraction of sinomenine by deep eutectic solvents

Sinomenine is the main bio-active ingredient of Sinomenii Caulis and usually produced by solventextraction techniques. However, the extraction of sinomenine suffers from the lack of highly efficient and environmentally-benign solvents. In this work, deep eutectic solvents(DESs) based on fragrances were synthesized, hydrogen-bond donors(HBDs) and hydrogen-bond acceptors(HBAs) components of DESs were identified and their extraction ability for sinomenine was evaluated and the extraction conditions were optimized by single-factor and orthogonal design experiments. It was found that the hydrogen-bonding interaction between sinomenine and DESs was the main extraction driving force and there was no explicit relationship between the extraction ability and the hydrophobicity of the DESs. The DESs could be recycled and sinomenine could be recovered quantitatively via backextraction. High-purity sinomenine((95.0 ± 2.3)%) could be produced. These findings suggest that DESs are highly-effective solvents for the isolation of sinomenine and exhibit great potential for the extraction of other bio-active compounds.

Catalytic oxidative desulfurization of fuels in acidic deep eutectic solvents with [(C_6H_(13))_3P(C_(14)H_(29))]_3PMo_(12)O_(40) as a catalyst

Deep eutectic solvents(DESs) are a new class of green solvents analogous to ionic liquids due to their biodegradable capacity and low cost. However, the direct extractive desulfurization of diesel oil by DESs cannot meet the government’s standard. In this work, amphiphilic polyoxometalates were synthesized and characterized by FT-IR and mass spectrometry.The oxidative desulfurization results showed that benzothiophene(BT) could be completely removed by employing a [(CH)P(CH)]PMoO, DES(ChCl/2 Ac) and HOsystem. It was also found that the organic cation of catalysts played a positive role in oxidative desulfurization. The reaction conditions, such as reaction temperature and time, the amount of catalyst and DES and HO/S(O/S) molar ratio, were optimized. Different sulfides were tested to determine the desulfurization selectivity of the optimal reaction system, and it was found that 97.2% of dibenzothiophene(DBT) could be removed followed by 80.7% of 4-MDBT and 76.0% of 4,6-DMDBT. After reaction, the IR spectra showed that the catalyst [(CH)P(CH)]PMoOwas stable during the reaction process and the oxidative product was dibenzothiophene sulfone(DBTO). Furthermore, the catalyst can be regenerated and recycled for four runs with little loss of activity.

Photocatalytic oxidative of Keggin-type polyoxometalate ionic liquid for enhanced extractive desulfurization in binary deep eutectic solvents

A series of novel binary deep eutectic solvents(DESs)composed of choline chloride(ChCl)and formic acid(HCOOH)with different molar ratios have been successfully synthesized and applied in extractive desulfurization(EDS).Keggin-type polyoxometallate ionic liquid[TTPh]_(3)PW_(12)O_(40) was prepared and used as catalyst to enhance the EDS capacity by means of photocatalytic oxidative process.Both of the DESs and[TTPh]_(3)PW_(12)O_(40) ionic liquid catalyst were characterized in detail by Fourier transform infrared spectroscopy spectra(FT-IR),elemental analysis,and X-ray photoelectron spectroscopy(XPS).It was found that the molar ratios of Ch Cl:HCOOH had a major impact on desulfurization performance,and the optimal desulfurization capacity 96.5%was obtained by ChCl/5 HCOOH.Besides dibenzothiophene(DBT),the desulfurization efficiencies of 4-methylbenzothiophene(4-MDBT)and 4,6-dimethyldibenzothiophene(4,6-DMDBT),two kinds of DBT derivatives,were also investigated under the same experimental conditions.Moreover,the free radical scavenging experiments manifested that superoxide radical(·O_(2)^(-)) and hole(h^(+)) played important roles in the desulfurization system.After further analysis of the oxidation products by gas chromatography-mass spectrometry(GC–MS),the possible reaction mechanism was proposed.Thus,photocatalytic oxidative has been proved to be one of the efficient approaches for enhancing the extractive desulfurization performance in DES.

Investigation of CO2 solubility in monoethanolamine hydrochloride based deep eutectic solvents and physical properties measurements

Deep eutectic solvents(DESs)have drawn a growing research interest for applications in a wide range of scientific and industrial arenas.However,a limited effort has been reported in the area of gas separation processes and particularly the carbon dioxide capture.This study introduces a novel set of DESs that were prepared by complexing ethylenediamine(EDA),monoethanolamine(MEA),tetraethylenepentamine(TEPA),triethylenetetramine(TETA)and diethylenetriamine(DETA)as hydrogen bond donors to monoethanolamide hydrochloride(EAHC)salt as a hydrogen bond acceptor.The absorption capacity of CO2 was evaluated by exploiting a method based on measuring the pressure drop during the absorption process.The solubility of different DESs was studied at a temperature of 313.15 K and initial pressure of 0.8 MPa.The DES systems 1 EAHC:9 DETA,1 EAHC:9 TETA and 1 EAHC:9 TEPA achieved the highest CO2 solubility of 0.6611,0.6572 and 0.7017 mol CO2·(mole DES)-1 respectively.The results showed that CO2 solubility in the DESs increased with increasing the molar ratio of hydrogen bond donor.In addition,the CO2 solubility increased as the number of amine groups in the solvent increases,therefore,increasing the alkyl chain length in the DESs,resulted in increasing the CO2 solubility.FTIR analysis confirms the DES synthesis since no new functional group was identified.The FTIR spectra also revealed the carbamate formation in DES-CO2 mixtures.In addition,the densities and viscosities of the synthesized DESs were also measured.The CO2 initial investigation of reported DESs shows that these can be potential alternative for conventional solvents in CO2 capture processes.

Ternary deep eutectic solvents catalyzed D-glucosamine self-condensation to deoxyfructosazine: NMR study

Ternary deep eutectic solvents(TDESs) comprising choline chloride(Ch Cl), glycerol and L-arginine were synthesized as catalysts and solvents for the conversion of D-glucosamine(GlcNH_(2)) into deoxyfructosazine(DOF). The interactions between these three components in the prepared TDESs were studied by ^(1)H-,^(35)Cl-NMR spectra and ^(1)H diffusion-ordered spectroscopy(DOSY) measurements. The chemical shift changes of active hydrogen in the ^(1)H-NMR spectra of TDES system and widening of signals in the^(35)Cl-NMR spectra confirmed the hydrogen bonding interaction between the components, which was further supported by the decrease of diffusion coefficients(D) of the TDES components according to ^(1)H DOSY measurements. The influences of reaction temperature and L-arginine content in the TDESs on the yield of DOF were also studied. The experimental results have shown that when the molar ratio of Ch Cl, glycerol, and L-arginine was 1:2:0.1, DOF was the major product with a yield of 22.6% at 90℃ for 120 min. The chemical shift titration indicated that the carboxyl group of L-arginine in the TDES is the catalytical active site, so the mechanism of the catalytic reaction between Glc NH_(2) and the TDES was proposed. Moreover, a reaction intermediate, dihydrofructosazine, was identified in the self-condensation reaction of Glc NH_(2) by an in situ ^(1)H NMR technique.

Overview of acidic deep eutectic solvents on synthesis,properties and applications

This review divides the acidic deep eutectic solvents(ADES) into Br?nsted and Lewis DES according to their diversity of acidic character.The hydrogen bond donors and halide salts for formulating an ADES are classified, the synthesis methods are described, and the physicochemical properties including freezing point, acidity, density, viscosity and conductivity are presented. Furthermore, the applications of Br?nsted acidic deep eutectic solvents(BADES) and Lewis acidic deep eutectic solvents(LADES) are overviewed, respectively, covering the fields in dissolution, extraction, organic reaction and metal electrodeposition. It is expected that the ADES has great potential to replace the pollutional mineral acid, expensive and unstable solid acid, and costly ionic liquid in many acid-employed chemical processes, thus meeting the demands of green chemistry.

Ionic liquids/deep eutectic solvents for CO_(2) capture:Reviewing and evaluating

The CO_(2)solubilities(including CO_(2)Henry’s constant)in physical-and chemical-based ILs/DESs and the COSMO-RS models describing these properties were comprehensively collected and summarized.The summarized results indicate that chemical-based ILs/DESs are superior to physical-based ILs/DESs for CO_(2)capture,especially those ILs have functionalized cation and anion,and superbase DESs;some of the superbase DESs have higher CO_(2)solubilities than those of ILs;the best physical-and chemical-based ILs,as well as physical-and chemicalbased DESs are[BMIM][BF4](4.20 mol kg^(-1)),[DETAH][Im](11.91 mol kg^(-1)),[L-Arg]-Gly 1:6(4.92 mol kg^(-1))and TBD-EG 1:4(12.90 mol kg^(-1)),respectively.Besides the original COSMO-RS mainly providing qualitative predictions,six corrected COSMO-RS models have been proposed to improve the prediction performance based on the experimental data,but only one model is with universal parameters.The newly determined experimental results were further used to verify the perditions of original and corrected COSMO-RS models.The comparison indicates that the original COSMO-RS qualitatively predicts CO_(2)solubility for some but not all ILs/DESs,while the quantitative prediction is incapable at all.The original COSMO-RS is capable to predict CO_(2)Henry’s constant qualitatively for both physical-based ILs and DESs,and quantitative prediction is only available for DESs.For the corrected COSMO-RS models,only the model with universal parameters provides quantitative predictions for CO_(2)solubility in physical-based DESs,while other corrected models always show large deviations(>83%)compared with the experimental CO_(2)Henry’s constants.

Deep eutectic solvents and alkaline extraction of protein from seabuckthorn seed meal: a comparison study

Seabuckthorn seed meal(SSM) is a waste of oil extraction industry that rich in protein. In order to seek suitable protein extraction method, three different deep eutectic solvents(DESs)(including choline chlorideglycerol, choline chloride-oxalic acid and choline chloride-urea) were developed for extracting protein from SSM and compared with alkaline. Result indicated that alkaline could effectively extract 56.9% protein from SSM and its protein content was 73.1%, higher than DES at 31.0%-41.4% and 64.3%-67.5%, respectively. However, compared to alkali, DES led to a product with less β-sheet, more β-turn, more essential amino acids, higher total amino acid content, especially choline chloride-urea which extracted protein showing an integrated and similar protein weight distribution compared to SSM. Also, this protein extracted chloride-urea showed a highest digestibility in vitro(by pepsin)(54.2%). These results indicated that choline chloride-urea extraction is better than alkaline extraction for SSM.

Long-chain alkanol-alkyl carboxylic acid-based low-viscosity hydrophobic deep eutectic solvents for one-pot extraction of anthraquinones from Rhei Radix et Rhizoma

Natural long-chain alkanol and alkyl carboxylic acid were used to prepare novel hydrophobic deep eutectic solvents(HDESs).These HDESs are liquid at room temperature and have low viscosity(<12.26 mPa·s),low polarity(lower than that of methanol,ChCl-based deep eutectic solvents and other reported HDESs),and low density(<0.928 g/mL).A simple one-pot method based on a novel HDES-water two-phase extraction system was constructed for the extraction of weak-polarity bioactive components,anthraquinones,from Rhei Radix et Rhizoma.This HDES-based new extraction method does not consume hazardous organic solvents and can obtain a total anthraquinone yield of 21.52 mg/g,which is close to that obtained by the Chinese pharmacopoeia method(21.22 mg/g)and considerably higher than those by other reported HDESs-based extraction methods(14.20-20.09 mg/g,p<0.01).The high extraction yield can be mainly attributed to the severe destruction of the RRR cell walls by the extraction system and the excellent dissolving ability of novel HDESs for anthraquinones.

Reshaping the imprinting strategy through the thermo-responsive moiety-derived“deep eutectic solvents”effect

As a new concept having emerged in last few years,the“deep eutectic solvents”(DESs)effect integrated into the imprinting technology inevitably exposes design limitations of stimuli-responsive molecularly imprinted polymers(MIPs),as well as inadequate analysis of the adsorption performance of MIPs.Herein,a simple yet defined N-isopropylacrylamide/(3-acrylamidopropyl)trimethylammonium chloride(NIPAM/APTMAC)binary DESs system was proposed to prepare intelligent MIPs with thermo-sensitivity.Accordingly,magnetic and thermo-responsive MIPs based on functional monomers-derived DESs(TMDESs-MIPs1)were synthesized,revealing DESs effect-regulated affinity/kinetics for the enhanced adsorption capability,eco-friendly thermo-regulated elution for high release efficiency,and simple magnetic separation,along with superior selectivity to rhein(RH)and good regeneration ability.TM-DESs-MIPs1 were utilized to extract RH from Cassiae semen samples coupled with high performance liquid chromatography(HPLC),yielding satisfactory recoveries(79.47%−110.82%)and low limits of detection(LOD)(16.67μg/L).Another two kinds of MIPs adopting the thermo-responsive moiety-derived DESs effect strategy further demonstrated great applicability of such intelligent MIPs for analyses of complicated samples.

Extraction of Eugenol from Essential Oils by In Situ Formation of Deep Eutectic Solvents:A Green Recyclable Process

Eugenol is extensively utilized in chemical industry.In actual production,it is mainly separated from clove essential oils(EOs)through acid-base solutions.In this work,a simple,rapid and effective extraction process was developed for the extraction of eugenol from EOs samples by directly forming deep eutectic solvents(DESs)without using acid-base solutions.The proposed process is designed to dissolve EOs in n-hexane and eugenol was highly selective extracted into DESs with tetrabutylammonium chloride(TBAC).Hydrogen bonds in DESs can be broken by addition of water,resulting in a separation of the two phases,thus obtaining a hydrophobic yellowish eugenol in the upper layer.The quaternary ammonium salt in the lower aqueous solution can be reused after recovery.The most determining influence factors such as the structure of quaternary ammonium salt,the mole ratio of quaternary ammonium salt to eugenol and the amount of n-hexane were investigated.The forming conditions of DESs were studied by Box-Behnken design(BBD).Experiment was carried out under the optimal conditions and good experimental result was demonstrated by the developed process,a high extraction recovery of 92.51% and the purity was about 98.50%,which verifies the excellent performance for the proposed process.

Responsive switchable deep eutectic solvents:A review

Deep eutectic solvents(DESs)have drawn considerable attention as a new type of green solvent since they were reported.Subsequent studies have shown that DESs have the potential to be used as“designable”solvents,which means that the precursors of DESs with different structures and properties can be screened to customize DESs for specific functions.Researchers have found that during the sample preparation process involving DESs,the specific properties of some“smart”DESs can be switched by directing external driving forces,leading to a reversible phase transition of the target solution.These"smart"DESs are called switchable deep eutectic solvents(SDESs).The advent of SDES simplifies the sample pretreatment steps,reduces the use of organic solvents,and makes solvents easy to recycle,which matches the concept of green and sustainable chemistry.Compared with the number of previous experimental studies,the reviews and summaries on SDESs are rare.Therefore,this review made a summary of the concept and research progress of SDESs based on some related works in the past decade,including composition and type,characterization,switching mechanism,etc.It is expected to provide a certain reference and guidance for the subsequent in-depth research of SDESs in the analytical sample pretreatment.