Next Article in Journal
Trend and Attribution Analysis of Runoff Changes in the Weihe River Basin in the Last 50 Years
Next Article in Special Issue
Reactive Transport of NH4+ in the Hyporheic Zone from the Ground Water to the Surface Water
Previous Article in Journal
Hydrological Effects of Prefabricated Permeable Pavements on Parking Lots
Previous Article in Special Issue
Removal of Aqueous Para-Aminobenzoic Acid Using a Compartmental Electro-Peroxone Process
Review

Application of Extraction and Determination Based on Deep Eutectic Solvents in Different Types of Environmental Samples

Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China
*
Author to whom correspondence should be addressed.
Academic Editor: Donghai Wu
Water 2022, 14(1), 46; https://doi.org/10.3390/w14010046
Received: 22 November 2021 / Revised: 22 December 2021 / Accepted: 22 December 2021 / Published: 25 December 2021
(This article belongs to the Special Issue Ecological Risk Assessment of Emerging Pollutants in Drinking Water)

Abstract

Water sources are an indispensable resource for human survival. Monitoring the pollution status of the surrounding environment is necessary to protect water sources. Research on the environmental matrix of deep eutectic solvents (DESs) has expanded rapidly because of their high extraction efficiency for various target analytes, controllable synthesis, and versatile structure. Following the synthesis of hydrophobic deep eutectic solvents (HDESs), their application in aqueous matrices broadened greatly. The present review conducted a survey on the pollutant extraction methods based DESs in environmental matrices from two aspects, application methods and matrix types; discussed the potential risk of DESs to the environment and future development trends; and provided some references for researchers to choose DES-based extraction methods for environmental research.
Keywords: deep eutectic solvents; drinking water; environmental analysis; sample preparation; green solvents deep eutectic solvents; drinking water; environmental analysis; sample preparation; green solvents

1. Introduction

New pollutants continue to appear with the development of society, many of which cannot be decomposed in natural water as a source of drinking water [1]. The pollution process of these pollutants in water sources is slow and hidden. They enter the human body through drinking water and pose a threat to human health. In addition to the production and life of human beings, pollutants in water sources migrate from contaminated soil and the atmosphere into water bodies [2,3]. These pollutants have now been detected in environmental matrices, such as surface water, sewage/sludge, soil/sediments, and indoor air/dust. In order to further study their potential threat, the first step is to understand their occurrence in environmental samples. However, the matrices are complex, and the organic pollutant concentration is usually low to the nanogram level. Therefore, it is urgent to explore an effective pretreatment method.
At present, the main pretreatment method is SPE, but it has disadvantages such as high cost, complicated operation, and poor repeatability. Although LPME overcomes the shortcomings of traditional pretreatment technologies, these methods have disadvantages such as toxic and harmful solvents and poor biodegradability. Based on the concept of green chemistry, Abbott et al. proposed a new type of green solvent called DES [4]. According to the definition, DES is a liquid, and its melting point is lower than all its components. The reason is that hydrogen bonds are formed between the components. Due to their noteworthy properties, such as negligible vapor pressure, large polarity range, and high thermal stability, DESs have been applied in separation processes, analytical chemistry, synthesis, electrochemistry, etc. [5,6,7,8]. DES synthesis methods include heating, evaporation, and freeze-drying. The heating method is currently the most commonly used method due to its easy operation [9]. Some authors have developed alternative synthesis methods to make DESs greener. For example, Gomez et al. [10] developed an MA method with a short synthesis time (20 s) and low energy consumption.
Analytical sample pretreatment is one of the emerging applications of DESs. Due to their properties such as low cost, easy preparation and restructuring, and low toxicity and biodegradability, DESs are preferable over conventional solvents. Additionally, interactions between DESs and target analytes, including electrostatic, π–π, van der Waals (dispersion), hydrogen bonding, hydrophobic, and dipole–dipole and ion–dipole forces, provide DESs with high solubility to pollutants during pretreatment [11]. In addition, the density of DESs is usually higher than water, which helps them separate from the water phase during the extraction process. Thus, the number of reports on using DESs as extractants to concentrate analytes has increased rapidly since 2012 (Figure 1) [5]. DESs have been applied in various pretreatment techniques to extract different kinds of analytes (such as metal ions, fatty and organic acids, volatile organic compounds, dyes and pigments, pesticides, peptides and proteins, plant compounds) in real matrices, including water, air, soil, and biological samples [9].
With the increasing application of DESs in the analytical field, many review articles have been published. For example, the review article by Makoś et al. [12] focused on HDESs used in the microextraction method. The review article by Santana et al. [9] compiled two aspects, sample preparation and analytical techniques, related to the application of DESs in analytical chemistry in 2016–2020. A recent review by Tang et al. [13] paid attention to the development of DES-based microextraction procedures. Some recent papers gave a focused and comprehensive review of the applications of DESs during DLLME of pesticides in food samples [14] and coastal zone environmental samples [15]. This review systematically focused on recent applications of DESs in different environmental matrices to improve the general understanding of the use of DESs in analytical chemistry.

2. Deep Eutectic Solvents

2.1. Classification of DESs

DESs are commonly classified into four types: Type I (quaternary salt and metal halide), Type II (quaternary salt and hydrated metal halide), Type III (quaternary salt, terpene, and hydrogen bond donor), and Type IV (metal halide and HBD) (Figure 2).
Type I DESs are formed by quaternary ammonium salts and nonhydrated metal halides. Although the types of nonhydrated metal halides that can form type I DESs are limited, DESs vary with the molar fraction of nonhydrated metal halides, which is different from ionic liquids consisting of independent anions such as B F 4 and P F 6 . This kind of ionic DES is mainly used as a catalyst or to synthesize catalysts in the organic field [16].
Type II DESs are formed by quaternary salt and hydrated metal halide. Due to their low cost and insensitivity to components, they are easy to synthesize. However, only a few applications in extraction are available because of the toxicity of metal halide. Choi et al. [17] developed an efficient lipid extraction method from Chlorella vulgaris using a DES composed of [EMIM][OAc] and FeCl3·6H2O.
Type III DESs formed by quaternary salt or terpene with HBD are fundamentally different from the former two types of DES. In type III DESs, the halogen anion X forms a hydrogen bond with ligand Y, which reduces the Coulomb force between the anion and cation. Thus, these DESs possess excellent dissolution properties owing to their ability to donate protons or accept electrons to form hydrogen bonds [18]. Regarding environmental analysis, it has been successfully applied to extract and isolate organic compounds, inorganic analytes, pharmaceuticals, pesticides, and so on [9].
Moreover, DESs prepared from a combination of metal halide, generally with transition metals, and organic ligands (HBD) are classified as Type IV [19]. This kind of DES is usually used as an electroplating solution [20] in metal electroplating and a catalyst [21] in organic reactions. Liu et al. [22] used a DES catalyst to convert cellulose into gluconic acid.

2.2. Hydrophilic and Hydrophobic DESs

The presence of hydrophilic functional groups in the components, such as hydroxyl, carboxyl, or amino groups, will cause DESs to become hydrophilic (namely hydrophilic DESs), such as Type I, II, IV, and some Type III hydrophilic DESs. The application range of hydrophilic DESs is limited due to their instability in water. Conversely, hydrophilic DESs have great advantages in the extraction of hydrophilic analytes from nonaqueous samples. For example, phenolic compounds are extracted from a variety of plant samples [23,24,25,26,27], and bioactive carbohydrates, such as polysaccharides [28,29] and pectin [30], are extracted from plants. Although most bioactive compounds are hydrophilic, some lipid-soluble bioactive compounds are hydrophobic. Hydrophobic solvents can enhance the extraction efficiency of lipid-soluble bioactive compounds.
To expand the application of DESs, especially in aqueous samples, van Osch et al. [31] proposed the first HDESs in 2015, which consisted of decanoic acid and long-chain quaternary ammonium salt. Later, a series of HDESs composed of a variety of fatty alcohols and long-chain fatty acids combined with long-alkyl-chain quaternary ammonium salts were synthesized [31]. Ribeiro et al. [32] proposed another type of hydrophobic deep eutectic solvent consisting of DL-menthol as the HBA, which is a natural monoterpene, and several short-chain acids (i.e., acetic, lactic, and pyruvic acids) as the HBD. Other terpenes can also be used to synthesize HDESs, such as thymol [33], camphor [34], and lidocaine [35]. However, the presence of hydrophilic components will reduce the stability of HDESs. The extent of influence on stability depends on the hydrophilicity of the components. It is worth highlighting that although there is a leaching loss, the HDES-rich phase still exists independently [12]. HDESs can be used to extract compounds in various matrices, such as artemisinin from leaves [36], cannabinoids from raw cannabis plant [37], pesticides [38] and antibiotics from water [39], drugs from human urine [40], and endocrine disruptor compounds from water [41].

2.3. Toxicity of DES

Few reports on the potential toxicity of DESs are available. Generally, DESs synthesized from sugars, alcohols, sugar alcohols, and amides are more eco-friendly, while, in contrast, DESs synthesized from metal ions and organic acids are not “green” [42]. Studies have shown that ChCl-based DESs combined with urea, glycerine, triethylene glycol, and ethylene glycol have no toxic effect, but they do have cytotoxicity. The cytotoxicity of these DESs is higher than their components [43]. Recently, different test organisms were used to test the toxicity of ChCl-based DESs composed of organic acid and sugar. DESs combined with organic acid and sugar had higher cytotoxicity than those combined with organic alcohol. However, the cytotoxicity of the components of the tested DESs was higher than that of DESs [44]. In addition, the molar ratio of HBA and HBD, lipophilicity, and the Hofmeister effect can also affect the toxicity of DESs [45]. Recently, Torregrosa-Crespo et al. [46] proposed that it is more accurate to confine the discussion to a certain concentration range for the toxicity of DESs. Some studies used predictive computational models to evaluate the cytotoxicity of DESs [42,47,48]. However, the results from toxicity tests are even more convincing, and more factors need to be considered, including culture conditions, type of culture media, and sterilization methods [46]. In future research avenues, more types of test organisms should be considered to represent different functional levels. It can help us fully understand how aquatic ecosystems are affected by DESs. Moreover, in order to have a more comprehensive understanding of the environmental sustainability of DESs, more studies focusing on bioaccumulation and biodegradability are required.

3. Application Forms in Environmental Analysis

LLE is the process of separating and extracting components of liquid mixtures with solvents. The volume of the extractant is usually the same as the volume of the water sample. The type of DES used is determined based on the nature of the sample and analyte. Some studies have applied this method to the extraction of volatile organic acids, metal ions, and organic pollutants in environmental water samples. However, LLE is gradually replaced by LPME due to the large volume of organic solvents and poor enrichment effect (Table 1).
LPME is an extraction technology that greatly reduces the volume of the extractant compared with LLE. Many methods have been developed to assist the extraction process, such as vortex, heating, microwave, and ultrasonic. Some studies made the methods more convenient and faster by reducing the number of steps, such as the synthesis of DESs [49,50]. At the same time, in order to more thoroughly separate the organic phase and the water sample, researchers made the extractant magnetic and combined it with LPME [51]. The analyte selectivity of DESs is higher than ordinary organic solvents such as methanol, acetonitrile, and dichloromethane because of the special structure of DESs. Combined with LPME, the method not only has the advantages of extraction technology but also reduces costs and improves environmental friendliness. In general, LPME can be divided into three categories: DLLME, SDME, and HF-LPME.
Table 1. Extraction technique combined with DESs in environmental analysis.
Table 1. Extraction technique combined with DESs in environmental analysis.
TechniquesDESSampleOther FeaturesAnalytesInstrumental AnalysisLOD (ug/L,g)
HBAHBDMolar RatioVolumeTypeVolume
SLLE [52]N8881-ClOctanol/octanoic acid1:2:32 mLPlant leaves 0.2 gTwo DES phases were involvedFlavonoids
Terpene trilactones
Procyanidin
Polyprenyl acetates
HPLC-UV
LLE [53]MentholDodecanoic acid2:1 Water Lower alcohols Ethanol
1-Propanol
1-Butanol
NMR
LLE [54]Dodecanoic acidOctanoic acid
Nonanoic acid
Decanoic acid
1:3
1:3
1:2
2 mLWater2 mL Bisphenol AUV–vis
DLLME [55]N8881-ClOleic acid1:220 uLWater and biological samples5 mLVortex assistedNitriteHPLC-UV0.2
DLLME [56]Quaternary ammonium salt DL-menthol Aqueous samples Air assistedBenzophenoneHPLC-UV
DLLME [57]ChClTriethylamine1:1 Biological and environmental samples20 mLAir assisted
Volume of DES/triethylamine (TEA) (1:1) is 100 uL.
Heavy MetalsFAAS0.31–0.99
DLLME [58]ChClPhenol1:3450 uLLake water10 mLUltrasound assistedChromium (III/VI)FAAS5.5
DLLME [59]ChClPhenol1:31000 uLSoil, sediment, and water25 mLUltrasound assistedArsenicETAAS0.01
DLLME [60]N4444-ClDecanoic acid1:2200 uLLiver
samples
10 mLUltrasound assisted
DES (ChCl-lactic acid) is digestion solution
CopperMS-FAAS4.00
HS-SDME [61]N4444-BrDodecanol1:21.5 uLPlant
samples
50 mg TerpenesGC-MS0.87–86.40
HF-LPME [62]ChClPhenylethanol1:440 uLHuman plasma urine and pharmaceutical wastewater10 mLThree-phase (liquid–liquid–liquid) microextractionAntiarrhythmic agents
Propranolol
Carvedilol
Verapamil
Amlodipine
HPLC-UV
N8881-Cl: trioctylmethylammonium chloride (TAC); MS-FAAS: microsample injection system coupled with flame atomic absorption spectrometer; HS-SDME: headspace single-drop microextraction; SLLE: supported liquid–liquid extraction.

3.1. DLLME

In DLLME, the extractant is dispersed by the dispersive solvent or other auxiliary means to form small droplets, which are evenly distributed in the entire solution to increase the contact area. Using DESs as extractants in DLLME can obtain better application prospects [63]. Liu et al. [64] used the DES-DLLME method combined with HPLC-UV to determine SAs in river water. However, hydrophilic DESs cannot exist stably in water, and they can only be used for nonaqueous samples because water can break the hydrogen bond. Therefore, HDESs that use long-chain fatty acids, quaternary amine salts, and terpenes as HBD are applied as extractants for water samples. For example, Werner [65] established the UA-DES-DLLME method for the green and efficient determination of aromatic amines from environmental water samples. El-Deen et al. [66] extracted steroids in a water sample through tetrabutylammonium bromide/acetic acid DES. Wang et al. [67] evaluated the in situ applicability of HDESs for the extraction of UV filters dissolved in raw water samples by DLLME. A new type of DLLME is AA-LLME. By pumping and injecting several times, the extractant and water can be completely mixed. Lamei et al. [68] extracted methadone from biological and water samples using this technique.

3.2. SDME

SDME has been recognized as one of the simple miniaturized sample preparation tools for the isolation and preconcentration of several analytes from a complex sample matrix [69]. The application of DESs in SDME is rapidly growing in analytical practice for the extraction and preconcentration of several analytes, owing to their unique physicochemical and mechanical properties [70]. In SDME, droplets are commonly immersed in the sample. In addition, the method of suspending extractant droplets on the tip of a syringe to extract volatile compounds is called HS-SDME.
Yousefi et al. [71] used gel prepared from DES as an extractant in HS-SDME to concentrate volatile hydrocarbons from water and urine samples. Compared with traditional solvents, DESs have higher thermal stability, higher viscosity, lower volatility, and adjustable miscibility and are more capable of forming stable droplets of HS-SDME. A novel DES based on montmorillonite clay, Fe3O4-DL-menthol, and decanoic acid [51] is highly hydrophobic, with lower viscosity and density than that of water, and can extract explosive compounds from water and soil samples. Deep eutectic solvents were synthesized by mixing tetrabutylammonium bromide (HBA) with various alcoholic molecules and ChCl-urea with ChCl-lactic acid at different molar ratios [72] to analyze terpenes based on the HS-SDME method.

3.3. HF-LPME

Pedersen-Bjergaard [73] established a new microextraction method in which the extractant exists in the form of a liquid film. In the HF-LPME system, the extraction phase is usually SLM in the hollow fiber, which separates the target compound from the sample and then enters the acceptor phase in the cavity of the hollow fiber.
In 2018, Khatael et al. reported three-phase HF-LPME based on n-dodecane and DESs, which consisted of ChCl and MTPB as the acceptor phase of steroidal hormones from biological fluids [74]. Rajabi et al. first adopted a completely eco-friendly and high solubility HDES (ChCl/1-phenylethanol) for HF-LPME in biological and environmental samples [62]. In 2021, Pedersen-Bjergaard et al. first reported that a hydrophobic NADES (coumarin/thymol) was used as SLM for electromembrane extraction in a biological fluid sample and almost completely extracted different polar compounds [75]. This paper proved that DESs are very suitable for extraction in the form of SLM.

4. Applications in Environmental Matrix

When the analyte concentration is very low and the sample matrix is complex, the most important and unavoidable step in the analytical process is extraction. Choosing the right extractant can more efficiently analyze and determine the environmental matrix. DESs are novel, green, and designable solvents with high degradability and low cost. Therefore, the number of studies on the application of DESs in environmental sample preparation methods is rapidly increasing. As shown in Table 2, most methods using HDESs can be used to detect targets in various types of matrices. Hydrophilic DESs are mainly used for the extraction of active substances from plants and are rarely used for soil samples. The reason is that when detecting the content of organic matter in soil, the target substance is first extracted from the soil into the aqueous solution and then enriched and purified. This will also depend on whether the target is hydrophilic or hydrophobic.

4.1. Extraction from Aqueous Samples

For aqueous applications, HDESs are desirable due to their stability in aqueous solution. HDESs are mainly divided into two categories according to the type of HBA/tetraalkyl-quaternary-ammonium-based HDESs and terpene-based HDESs. Quaternary-ammonium-based HDESs can extract metals. Ruggeri et al. [86] investigated HDESs based on tetrabutylammonium chloride and decanoic acid and their application in the extraction of Cr(VI) species from an aqueous phase. In addition to extracting inorganic metal ions, this type of HDES can also be used to extract a variety of organic substances. Yousefi et al. [87] prepared a HDES consisting of TBAB and carboxylic acids and applied the synthesized HDES in the analysis of PAHs in environmental water samples. Terpene-based HDESs have also been applied to extract various organic analytes by liquid–liquid extraction. In 2015, HDESs consisting of DL-menthol (HBA) and various organic acids (HBD) were first reported [32]. Lower alcohols, ethanol, propanol, and butanol could be enriched in menthol-based HDESs [53]. In addition, the extraction of inorganic metals has been reported, and In [88] and Cu [89] can be transferred to menthol and thymol-based HDESs [89].
For aqueous samples, hydrophilic DESs are generally not advisable as the extractant phase for aqueous matrices unless other organic solvents (THF) are added to ensure phase separation. This will reduce the greenness of the method since the volume of organic solvents is increased. However, it should be noted that the efficiency of extracting water-soluble analytes will be significantly improved when a hydrophilic DES is used as the extractant. One of the most widely used hydrophilic DESs for the extraction of contaminants in aqueous samples is formed by ChCl and phenol in different molar ratios. In this case, the mixture of DES and water makes necessary the use of an emulsifier (aprotic solvent) that achieves phase separation because of the self-aggregation phenomenon. Some studies used choline chloride/phenol DES as an extractant and an aprotic solvent THF to separate microcystin [90], BTRs, and BTs [91] from surface water samples. Sometimes, the role of DES in the extraction process is not as an extractant but as an assistant agent to extract steroids from river and tap water [66].

4.2. Extraction from Air Samples and Soil/Sediment Samples

Most applications of DESs in air samples are used as absorption solutions for CO2, SO2, and NO [92]. However, only a few DESs have been used for the extraction and determination of analytes from air samples up to now. HDESs have been used as extractants using aqueous acid as an absorption solution in the VA-LLME method coupled with HPLC for the selective enrichment and indirect determination of formaldehyde from indoor air samples [85]. In the extraction and separation of analytes from solid samples, the choice of DES is not limited by its own hydrophilicity and hydrophobicity. Therefore, the choice of DES only depends on the solubility of contaminants in the DES when used as an extractant. Following the extraction of solid samples, the suspensions obtained by centrifugation usually need to be filtered before entering the instrument for analysis. The DES composed of choline chloride and oxalic acid was used as a solvent for extraction of As, Cr, Mo, Sb, Se, and V in real soil samples [79] and Cu in sediment samples [80]. Compared with the results determined using the conventional acid digestion method, the method was found to be accurate, precise, and eco-friendly. In addition, it can also be used for the extraction and determination of organic pollutants from soil such as pesticides [84] and nitrotoluene [83]. Furthermore, some studies use DESs to prepare ferrofluid to extract explosives from soil samples by suspended droplet microextraction [51]. The extraction procedure has a high potential for application in complex matrices.

4.3. Extraction from Organism Samples

Compared to environmental water, soil/sediment, and air, the extraction of biological samples based on DES is less explored. In applications related to the field of biological sample analysis, according to the sample classification, it can be divided into three different types: biological fluid, animal, and plant samples. Works related to biological samples mainly focus on digestion methods based on DESs, for example: determination of Cu, Zn, and Fe in fish samples [93]; Cu, Fe, Ni and Zn in marine biological samples [94]; As, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, P, and Zn in plants [95]; and polycyclic aromatic hydrocarbons in biological samples [96]. In general, various methods have been applied in the extraction of biological samples, such as heating [93] and microwave [94].
The air-assisted DLLME method was used to determine trace amphetamine and methamphetamine in human plasma [81]. HDESs consisting of ChCl and phenylethanol were used as the extraction medium during this microextraction process. Rastbood et al. [97] proposed ChCl:[email protected]2@Fe3O4 ferrofluid as a sorbent for the magnetic SPME of the anti-inflammatory drug meloxicam from human plasma and urine samples.
It is interesting to note that the application of DESs in plant samples to extract natural active substances and natural pigments from the herbaceous plant safflower is more stable in NADESs than in water [98]. Recently, Dai et al. [78] employed diverse NADESs to extract anthocyanins from the purple and orange petals of Catharanthus roseus. Cao et al. [52] suggested a two-phase DES system to extract and fractionate analytes of diverse polarity, i.e., hydrophobic polyprenyl acetates and partially hydrophilic components (flavonoids, terpene trilactones, and procyanidin) from ginkgo leaves. Compared with the traditional acid digestion method, the reagent consumption of the DES-based extraction method is greatly reduced, the required time is shorter, and the method is safer because neither high pressure nor concentrated acid is involved.

5. Concluding Remarks

To control the pollution of drinking water sources, it is necessary not only to conduct real-time detection of water samples in water sources but also to pay certain attention to the nearby soil and atmosphere [99,100]. Extraction is an important and unavoidable step in the environmental analysis process. DESs are ideal as extractants because of their combination of simple and cost-effective preparation and task-specific design to meet the needs of specific processes. Extraction based on DESs is a reliable analytical tool with wide potential applications in environmental analysis. This review summarized recent studies of DESs used in environment samples and briefly discussed the extraction modes and types of environmental matrices, which is beneficial for researchers to understand DES applications in environmental matrices.
Although DESs have been widely applied in the field of extraction and separation, several challenges in DES-based extractants remain. Some DESs are composed of substances with suspicious toxicity. Compared with a single component, the toxicity of the combination of toxic and nontoxic compounds cannot be confirmed [46]. In order to use DESs more safely in extraction technology, toxicity and the environmental impact of more types of DESs need to be further studied. Another problem with HDESs is that although people are more and more interested in the synthesis of HDESs, their number is still limited, and further efforts are needed to synthesize new HDESs as extractants [101]. Furthermore, the study of the physicochemical properties of DESs during the synthesis and extraction mechanism also needs more attention because research on DESs is still at the application level, and the changes in the microstructure and physical and chemical properties are not clear [102]. Structural-related studies need to be designed to be more accurately applied to different environmental samples. In the future, the great interest of many researchers will promote the more sustainable development of extraction technology using DESs.

Author Contributions

Conceptualization, Y.W.; data curation, N.L.; methodology, N.L.; software, S.J. and X.C.; writing—original draft preparation, Y.W.; writing—review and editing, N.L.; supervision, Y.W.; project administration, Y.W.; funding acquisition, Y.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Fundamental Research Funds for the Central Universities, B200202105, and the World-Class Universities (Disciplines) and Characteristic Development Guidance Funds for the Central Universities.

Institutional Review Board Statement

Not Applicable.

Informed Consent Statement

Not Applicable.

Data Availability Statement

Not Applicable.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

Abbreviations
AAAir assisted
BTRsBenzotriazole derivatives
BTsBenzothiazole derivatives
ChClCholine chloride
DESDeep eutectic solvent
DLLMEDispersive liquid–liquid microextraction
DNADeoxyribonucleic acid
[EMIM][OAc]1-Ethyl-3-methyl imidazolium acetate
HBAHydrogen bond acceptor
HBDHydrogen bond donor
HDESsHydrophobic deep eutectic solvent
HF-LPMEFiber-based liquid-phase microextraction
HPLCHigh-performance liquid chromatography
HS-SDMEHeadspace single-drop microextraction
LLELiquid-liquid extraction
LPMELiquid-phase microextraction
MAMicrowave assisted
MTPBMethyltriphenylphosphonium bromide
NADESNature deep eutectic solvent
PAHsPolycyclic aromatic hydrocarbons
SAsSulfonamides
SDMESingle-drop microextraction
SLMSupported liquid membrane
SPESolid-phase extraction
SPMESolid-phase microextraction
TBABTetrabutylammonium bromide
THFTetrahydrofuran
UAUltrasound-assisted
VA-LLMEVortex-assisted liquid–liquid microextraction
Nomenclature
--Dipole–dipole forces
ρDensity
--Ion–dipole forces
mpMelting point
SSolubility
--Polarity
ƞViscosity
--van der Waals (dispersion) forces
--π–π forces

References

  1. Acosta-Rodríguez, I.; Rodríguez-Pérez, A.; Pacheco-Castillo, N.; Enríquez-Domínguez, E.; Cárdenas-González, J.; Martínez-Juárez, V.-M. Removal of Cobalt (II) from Waters Contaminated by the Biomass of Eichhornia crassipes. Water 2021, 13, 1725. [Google Scholar] [CrossRef]
  2. Maurya, P.K.; Ali, S.A.; Alharbi, R.S.; Yadav, K.K.; Alfaisal, F.M.; Ahmad, A.; Ditthakit, P.; Prasad, S.; Jung, Y.-K.; Jeon, B.-H. Impacts of Land Use Change on Water Quality Index in the Upper Ganges River near Haridwar, Uttarakhand: A GIS-Based Analysis. Water 2021, 13, 3572. [Google Scholar] [CrossRef]
  3. Rahmawati, R.R.; Putro, A.H.S.; Lee, J.L. Analysis of Long-Term Shoreline Observations in the Vicinity of Coastal Structures: A Case Study of South Bali Beaches. Water 2021, 13, 3527. [Google Scholar] [CrossRef]
  4. Abbott, A.P.; Capper, G.; Davies, D.L.; Rasheed, R.K.; Tambyrajah, V. Novel solvent properties of choline chloride/urea mixtures. Chem. Commun. 2003, 39, 70–71. [Google Scholar] [CrossRef] [PubMed]
  5. Tang, B.; Zhang, H.; Row, K.H. Application of deep eutectic solvents in the extraction and separation of target compounds from various samples. J. Sep. Sci. 2015, 38, 1053–1064. [Google Scholar] [CrossRef]
  6. Shishov, A.; Bulatov, A.; Locatelli, M.; Carradori, S.; Andruch, V. Application of deep eutectic solvents in analytical chemistry. A review. Microchem. J. 2017, 135, 33–38. [Google Scholar] [CrossRef]
  7. Ndizeye, N.; Suriyanarayanan, S.; Nicholls, I.A. Polymer synthesis in non-ionic deep eutectic solvents. Polym. Chem. 2019, 10, 5289–5295. [Google Scholar] [CrossRef]
  8. Nkuku, C.A.; LeSuer, R.J. Electrochemistry in Deep Eutectic Solvents. J. Phys. Chem. B 2007, 111, 13271–13277. [Google Scholar] [CrossRef]
  9. Santana-Mayor, Á.; Rodríguez-Ramos, R.; Herrera-Herrera, A.V.; Socas-Rodríguez, B.; Rodríguez-Delgado, M. Ángel Deep eutectic solvents. The new generation of green solvents in analytical chemistry. TrAC Trends Anal. Chem. 2021, 134, 116108. [Google Scholar] [CrossRef]
  10. Gomez, F.J.V.; Espino, M.; Fernández, M.A.; Silva, M.F. A Greener Approach to Prepare Natural Deep Eutectic Solvents. Chem. 2018, 3, 6122–6125. [Google Scholar] [CrossRef]
  11. Faraji, M. Novel hydrophobic deep eutectic solvent for vortex assisted dispersive liquid-liquid micro-extraction of two auxins in water and fruit juice samples and determination by high performance liquid chromatography. Microchem. J. 2019, 150, 104130. [Google Scholar] [CrossRef]
  12. Makoś, P.; Słupek, E.; Gębicki, J. Hydrophobic deep eutectic solvents in microextraction techniques–A review. Microchem. J. 2020, 152, 104384. [Google Scholar] [CrossRef]
  13. Tang, W.; An, Y.; Row, K.H. Emerging applications of (micro) extraction phase from hydrophilic to hydrophobic deep eutectic solvents: Opportunities and trends. TrAC Trends Anal. Chem. 2021, 136, 116187. [Google Scholar] [CrossRef]
  14. Musarurwa, H.; Tavengwa, N.T. Deep eutectic solvent-based dispersive liquid-liquid micro-extraction of pesticides in food samples. Food Chem. 2021, 342, 127943. [Google Scholar] [CrossRef]
  15. Wang, Y.; Li, J.; Sun, D.; Yang, S.; Liu, H.; Chen, L. Strategies of dispersive liquid-liquid microextraction for coastal zone environmental pollutant determination. J. Chromatogr. A 2021, 1658, 462615. [Google Scholar] [CrossRef] [PubMed]
  16. Qin, H.; Hu, X.; Wang, J.; Cheng, H.; Chen, L.; Qi, Z. Overview of acidic deep eutectic solvents on synthesis, properties and applications. Green Energy Environ. 2020, 5, 8–21. [Google Scholar] [CrossRef]
  17. Choi, S.-A.; Lee, J.-S.; Oh, Y.-K.; Jeong, M.-J.; Kim, S.W.; Park, J.-Y. Lipid extraction from Chlorella vulgaris by molten-salt/ionic-liquid mixtures. Algal Res. 2014, 3, 44–48. [Google Scholar] [CrossRef]
  18. Abbott, A.P.; Frisch, G.; Hartley, J.; Ryder, K.S. Processing of metals and metal oxides using ionic liquids. Green Chem. 2011, 13, 471–481. [Google Scholar] [CrossRef]
  19. Abbott, A.P.; Barron, J.C.; Ryder, K.; Wilson, D. Eutectic-Based Ionic Liquids with Metal-Containing Anions and Cations. Chem. Eur. J. 2007, 13, 6495–6501. [Google Scholar] [CrossRef]
  20. Abbott, A.P.; Al-Barzinjy, A.A.; Abbott, P.D.; Frisch, G.; Harris, R.C.; Hartley, J.; Ryder, K.S. Speciation, physical and electrolytic properties of eutectic mixtures based on CrCl3·6H2O and urea. Phys. Chem. Chem. Phys. 2014, 16, 9047–9055. [Google Scholar] [CrossRef]
  21. Shahabi, D.; Tavakol, H. One-pot synthesis of quinoline derivatives using choline chloride/tin (II) chloride deep eutectic solvent as a green catalyst. J. Mol. Liq. 2016, 220, 324–328. [Google Scholar] [CrossRef]
  22. Liu, F.; Xue, Z.; Zhao, X.; Mou, H.; He, J.; Mu, T. Catalytic deep eutectic solvents for highly efficient conversion of cellulose to gluconic acid with gluconic acid self-precipitation separation. Chem. Commun. 2018, 54, 6140–6143. [Google Scholar] [CrossRef] [PubMed]
  23. Meng, Z.; Zhao, J.; Duan, H.; Guan, Y.; Zhao, L. Green and efficient extraction of four bioactive flavonoids from Pollen Typhae by ultrasound-assisted deep eutectic solvents extraction. J. Pharm. Biomed. Anal. 2018, 161, 246–253. [Google Scholar] [CrossRef] [PubMed]
  24. Yin, X.-S.; Zhong, Z.-F.; Bian, G.-L.; Cheng, X.-J.; Li, D.-Q. Ultra-rapid, enhanced and eco-friendly extraction of four main flavonoids from the seeds of Oroxylum indicum by deep eutectic solvents combined with tissue-smashing extraction. Food Chem. 2020, 319, 126555. [Google Scholar] [CrossRef] [PubMed]
  25. El Kantar, S.; Rajha, H.N.; Boussetta, N.; Vorobiev, E.; Maroun, R.G.; Louka, N. Green extraction of polyphenols from grapefruit peels using high voltage electrical discharges, deep eutectic solvents and aqueous glycerol. Food Chem. 2019, 295, 165–171. [Google Scholar] [CrossRef]
  26. Ali, M.C.; Chen, J.; Zhang, H.; Li, Z.; Zhao, L.; Qiu, H. Effective extraction of flavonoids from Lycium barbarum L. fruits by deep eutectic solvents-based ultrasound-assisted extraction. Talanta 2019, 203, 16–22. [Google Scholar] [CrossRef]
  27. Ozturk, B.; Parkinson, C.; Gonzalez-Miquel, M. Extraction of polyphenolic antioxidants from orange peel waste using deep eutectic solvents. Sep. Purif. Technol. 2018, 206, 1–13. [Google Scholar] [CrossRef]
  28. Nie, J.; Chen, D.; Lu, Y. Deep Eutectic Solvents Based Ultrasonic Extraction of Polysaccharides from Edible Brown Seaweed Sargassum horneri. J. Mar. Sci. Eng. 2020, 8, 440. [Google Scholar] [CrossRef]
  29. Gao, C.; Cai, C.; Liu, J.; Wang, Y.; Chen, Y.; Wang, L.; Tan, Z. Extraction and preliminary purification of polysaccharides from Camellia oleifera Abel. seed cake using a thermoseparating aqueous two-phase system based on EOPO copolymer and deep eutectic solvents. Food Chem. 2020, 313, 126164. [Google Scholar] [CrossRef]
  30. Shafie, M.H.; Yusof, R.; Gan, C.-Y. Deep eutectic solvents (DES) mediated extraction of pectin from Averrhoa bilimbi: Optimization and characterization studies. Carbohydr. Polym. 2019, 216, 303–311. [Google Scholar] [CrossRef]
  31. van Osch, D.J.; Zubeir, L.F.; Bruinhorst, A.V.D.; Rocha, M.A.; Kroon, M.C. Hydrophobic deep eutectic solvents as water-immiscible extractants. Green Chem. 2015, 17, 4518–4521. [Google Scholar] [CrossRef]
  32. Ribeiro, B.D.; Florindo, C.; Iff, L.C.; Coelho, M.A.Z.; Marrucho, I. Menthol-based Eutectic Mixtures: Hydrophobic Low Viscosity Solvents. ACS Sustain. Chem. Eng. 2015, 3, 2469–2477. [Google Scholar] [CrossRef]
  33. Martins, M.A.R.; Crespo, E.A.; Pontes, P.V.A.; Silva, L.P.; Bülow, M.; Maximo, G.J.; Batista, E.A.C.; Held, C.; Pinho, S.P.; Coutinho, J.A.P. Tunable Hydrophobic Eutectic Solvents Based on Terpenes and Monocarboxylic Acids. ACS Sustain. Chem. Eng. 2018, 6, 8836–8846. [Google Scholar] [CrossRef]
  34. Makoś, P.; Przyjazny, A.; Boczkaj, G. Hydrophobic deep eutectic solvents as “green” extraction media for polycyclic aromatic hydrocarbons in aqueous samples. J. Chromatogr. A 2018, 1570, 28–37. [Google Scholar] [CrossRef]
  35. van Osch, D.J.G.P.; Parmentier, D.; Dietz, C.H.J.T.; Bruinhorst, A.V.D.; Tuinier, R.; Kroon, M.C. Removal of alkali and transition metal ions from water with hydrophobic deep eutectic solvents. Chem. Commun. 2016, 52, 11987–11990. [Google Scholar] [CrossRef]
  36. Cao, J.; Yang, M.; Cao, F.; Wang, J.; Su, E. Well-Designed Hydrophobic Deep Eutectic Solvents As Green and Efficient Media for the Extraction of Artemisinin from Artemisia annua Leaves. ACS Sustain. Chem. Eng. 2017, 5, 3270–3278. [Google Scholar] [CrossRef]
  37. Křížek, T.; Bursová, M.; Horsley, R.; Kuchař, M.; Tuma, P.; Čabala, R.; Hložek, T. Menthol-based hydrophobic deep eutectic solvents: Towards greener and efficient extraction of phytocannabinoids. J. Clean. Prod. 2018, 193, 391–396. [Google Scholar] [CrossRef]
  38. Paul, N.; Naik, P.K.; Ribeiro, B.D.; Pattader, P.S.G.; Marrucho, I.M.; Banerjee, T. Molecular Dynamics Insights and Water Stability of Hydrophobic Deep Eutectic Solvents Aided Extraction of Nitenpyram from an Aqueous Environment. J. Phys. Chem. B 2020, 124, 7405–7420. [Google Scholar] [CrossRef]
  39. Florindo, C.; Lima, F.; Branco, L.C.; Marrucho, I.M. Hydrophobic Deep Eutectic Solvents: A Circular Approach to Purify Water Contaminated with Ciprofloxacin. ACS Sustain. Chem. Eng. 2019, 7, 14739–14746. [Google Scholar] [CrossRef]
  40. Shishov, A.; Chislov, M.; Nechaeva, D.; Moskvin, L.; Bulatov, A. A new approach for microextraction of non-steroidal anti-inflammatory drugs from human urine samples based on in-situ deep eutectic mixture formation. J. Mol. Liq. 2018, 272, 738–745. [Google Scholar] [CrossRef]
  41. Florindo, C.; Monteiro, N.V.; Ribeiro, B.D.; Branco, L.; Marrucho, I. Hydrophobic deep eutectic solvents for purification of water contaminated with Bisphenol-A. J. Mol. Liq. 2020, 297, 111841. [Google Scholar] [CrossRef]
  42. Bystrzanowska, M.; Tobiszewski, M. Assessment and design of greener deep eutectic solvents—A multicriteria decision analysis. J. Mol. Liq. 2021, 321, 114878. [Google Scholar] [CrossRef]
  43. Hayyan, M.; Hashim, M.A.; Hayyan, A.; Al-Saadi, M.A.; AlNashef, I.M.; Mirghani, M.E.; Saheed, O.K. Are deep eutectic solvents benign or toxic? Chemosphere 2013, 90, 2193–2195. [Google Scholar] [CrossRef]
  44. Radošević, K.; Zeleznjak, J.; Bubalo, M.C.; Redovniković, I.R.; Slivac, I.; Srček, V.G. Comparative in vitro study of cholinium-based ionic liquids and deep eutectic solvents toward fish cell line. Ecotoxicol. Environ. Saf. 2016, 131, 30–36. [Google Scholar] [CrossRef]
  45. Wen, Q.; Chen, J.-X.; Tang, Y.-L.; Wang, J.; Yang, Z. Assessing the toxicity and biodegradability of deep eutectic solvents. Chemosphere 2015, 132, 63–69. [Google Scholar] [CrossRef] [PubMed]
  46. Torregrosa-Crespo, J.; Marset, X.; Guillena, G.; Ramón, D.J.; Martínez-Espinosa, R.M. New guidelines for testing “Deep eutectic solvents” toxicity and their effects on the environment and living beings. Sci. Total Environ. 2020, 704, 135382. [Google Scholar] [CrossRef] [PubMed]
  47. Macário, I.; Oliveira, H.; Menezes, A.C.; Ventura, S.; Pereira, J.L.; Gonçalves, A.M.M.; Coutinho, J.; Gonçalves, F.J.M. Cytotoxicity profiling of deep eutectic solvents to human skin cells. Sci. Rep. 2019, 9, 3932. [Google Scholar] [CrossRef] [PubMed]
  48. Macário, I.P.; Jesus, F.; Pereira, J.L.; Ventura, S.P.; Gonçalves, A.M.; Coutinho, J.A.; Gonçalves, F.J. Unraveling the ecotoxicity of deep eutectic solvents using the mixture toxicity theory. Chemosphere 2018, 212, 890–897. [Google Scholar] [CrossRef]
  49. Li, K.; Jin, Y.; Jung, D.; Park, K.; Kim, H.; Lee, J. In situ formation of thymol-based hydrophobic deep eutectic solvents: Application to antibiotics analysis in surface water based on liquid-liquid microextraction followed by liquid chromatography. J. Chromatogr. A 2020, 1614, 460730. [Google Scholar] [CrossRef] [PubMed]
  50. Ge, D.; Wang, Y.; Jiang, Q.; Dai, E. A Deep Eutectic Solvent as an Extraction Solvent to Separate and Preconcentrate Parabens in Water Samples Using in situ Liquid-Liquid Microextraction. J. Braz. Chem. Soc. 2019, 30, 1203–1210. [Google Scholar] [CrossRef]
  51. Zarei, A.R.; Nedaei, M.; Ghorbanian, S.A. Ferrofluid of magnetic clay and menthol based deep eutectic solvent: Application in directly suspended droplet microextraction for enrichment of some emerging contaminant explosives in water and soil samples. J. Chromatogr. A 2018, 1553, 32–42. [Google Scholar] [CrossRef]
  52. Cao, J.; Chen, L.; Li, M.; Cao, F.; Zhao, L.; Su, E. Two-phase systems developed with hydrophilic and hydrophobic deep eutectic solvents for simultaneously extracting various bioactive compounds with different polarities. Green Chem. 2018, 20, 1879–1886. [Google Scholar] [CrossRef]
  53. Verma, R.; Banerjee, T. Liquid–Liquid Extraction of Lower Alcohols Using Menthol-Based Hydrophobic Deep Eutectic Solvent: Experiments and COSMO-SAC Predictions. Ind. Eng. Chem. Res. 2018, 57, 3371–3381. [Google Scholar] [CrossRef]
  54. Florindo, C.; Romero, L.; Rintoul, I.; Branco, L.C.; Marrucho, I.M. From Phase Change Materials to Green Solvents: Hydrophobic Low Viscous Fatty Acid–Based Deep Eutectic Solvents. ACS Sustain. Chem. Eng. 2018, 6, 3888–3895. [Google Scholar] [CrossRef]
  55. Zhang, K.; Li, S.; Liu, C.; Wang, Q.; Wang, Y.; Fan, J. A hydrophobic deep eutectic solvent-based vortex-assisted dispersive liquid-liquid microextraction combined with HPLC for the determination of nitrite in water and biological samples. J. Sep. Sci. 2019, 42, 574–581. [Google Scholar] [CrossRef] [PubMed]
  56. Ge, D.; Zhang, Y.; Dai, Y.; Yang, S. Air-assisted dispersive liquid-liquid microextraction based on a new hydrophobic deep eutectic solvent for the preconcentration of benzophenone-type UV filters from aqueous samples. J. Sep. Sci. 2018, 41, 1635–1643. [Google Scholar] [CrossRef]
  57. Ezoddin, M.; Lamei, N.; Siami, F.; Abdi, K.; Karimi, M.A. Deep Eutectic Solvent Based Air Assisted Ligandless Emulsification Liquid–Liquid Microextraction for Preconcentration of Some Heavy Metals in Biological and Environmental Samples. Bull. Environ. Contam. Toxicol. 2018, 101, 814–819. [Google Scholar] [CrossRef]
  58. Yilmaz, E.; Soylak, M. Ultrasound assisted-deep eutectic solvent based on emulsification liquid phase microextraction combined with microsample injection flame atomic absorption spectrometry for valence speciation of chromium(III/VI) in environmental samples. Talanta 2016, 160, 680–685. [Google Scholar] [CrossRef]
  59. Zounr, R.A.; Tuzen, M.; Khuhawar, M.Y. Ultrasound assisted deep eutectic solvent based on dispersive liquid liquid microextraction of arsenic speciation in water and environmental samples by electrothermal atomic absorption spectrometry. J. Mol. Liq. 2017, 242, 441–446. [Google Scholar] [CrossRef]
  60. Kanberoglu, G.S.; Yilmaz, E.; Soylak, M. Usage of deep eutectic solvents for the digestion and ultrasound-assisted liquid phase microextraction of copper in liver samples. J. Iran. Chem. Soc. 2018, 15, 2307–2314. [Google Scholar] [CrossRef]
  61. Triaux, Z.; Petitjean, H.; Marchioni, E.; Boltoeva, M.; Marcic, C. Deep eutectic solvent–based headspace single-drop microextraction for the quantification of terpenes in spices. Anal. Bioanal. Chem. 2020, 412, 933–948. [Google Scholar] [CrossRef] [PubMed]
  62. Rajabi, M.; Ghassab, N.; Hemmati, M.; Asghari, A. Highly effective and safe intermediate based on deep eutectic medium for carrier less-three phase hollow fiber microextraction of antiarrhythmic agents in complex matrices. J. Chromatogr. B 2019, 1104, 196–204. [Google Scholar] [CrossRef]
  63. Wu, B.; Guo, Z.; Li, X.; Huang, X.; Teng, C.; Chen, Z.; Jing, X.; Zhao, W. Analysis of pyrethroids in cereals by HPLC with a deep eutectic solvent-based dispersive liquid–liquid microextraction with solidification of floating organic droplets. Anal. Methods 2021, 13, 636–641. [Google Scholar] [CrossRef] [PubMed]
  64. Liu, L.; Zhu, T. Emulsification liquid–liquid microextraction based on deep eutectic solvents: An extraction method for the determination of sulfonamides in water samples. Anal. Methods 2017, 9, 4747–4753. [Google Scholar] [CrossRef]
  65. Werner, J. Novel deep eutectic solvent-based ultrasounds-assisted dispersive liquid-liquid microextraction with solidification of the aqueous phase for HPLC-UV determination of aromatic amines in environmental samples. Microchem. J. 2020, 153, 104405. [Google Scholar] [CrossRef]
  66. El-Deen, A.K.; Shimizu, K. Deep eutectic solvent as a novel disperser in dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFOD) for preconcentration of steroids in water samples: Assessment of the method deleterious impact on the environment using Analytical Eco-Scale and Green Analytical Procedure Index. Microchem. J. 2019, 149, 103988. [Google Scholar] [CrossRef]
  67. Wang, H.; Xu, Q.; Jiao, J.; Wu, H. A solidified floating organic drop-dispersive liquid–liquid microextraction based on in situ formed fatty acid-based deep eutectic solvents for the extraction of benzophenone-UV filters from water samples. New J. Chem. 2021, 45, 14082–14090. [Google Scholar] [CrossRef]
  68. Lamei, N.; Ezoddin, M.; Abdi, K. Air assisted emulsification liquid-liquid microextraction based on deep eutectic solvent for preconcentration of methadone in water and biological samples. Talanta 2017, 165, 176–181. [Google Scholar] [CrossRef]
  69. Kailasa, S.K.; Koduru, J.R.; Park, T.J.; Singhal, R.K.; Wu, H.-F. Applications of single-drop microextraction in analytical chemistry: A review. Trends Environ. Anal. Chem. 2021, 29, e00113. [Google Scholar] [CrossRef]
  70. Farooq, M.Q.; Zeger, V.R.; Anderson, J.L. Comparing the extraction performance of cyclodextrin-containing supramolecular deep eutectic solvents versus conventional deep eutectic solvents by headspace single drop microextraction. J. Chromatogr. A 2021, 1658, 462588. [Google Scholar] [CrossRef]
  71. Yousefi, S.M.; Shemirani, F.; Ghorbanian, S.A.; Ali, S. Enhanced headspace single drop microextraction method using deep eutectic solvent based magnetic bucky gels: Application to the determination of volatile aromatic hydrocarbons in water and urine samples. J. Sep. Sci. 2017, 41, 966–974. [Google Scholar] [CrossRef]
  72. Abbasi-Ahd, A.; Shokoufi, N.; Kargosha, K. Headspace single-drop microextraction coupled to microchip-photothermal lens microscopy for highly sensitive determination of captopril in human serum and pharmaceuticals. Microchim. Acta 2017, 184, 2403–2409. [Google Scholar] [CrossRef]
  73. Pedersen-Bjergaard, S.; Rasmussen, K.E. Liquid−Liquid−Liquid Microextraction for Sample Preparation of Biological Fluids Prior to Capillary Electrophoresis. Anal. Chem. 1999, 71, 2650–2656. [Google Scholar] [CrossRef]
  74. Khataei, M.M.; Yamini, Y.; Nazaripour, A.; Karimi, M. Novel generation of deep eutectic solvent as an acceptor phase in three-phase hollow fiber liquid phase microextraction for extraction and preconcentration of steroidal hormones from biological fluids. Talanta 2018, 178, 473–480. [Google Scholar] [CrossRef]
  75. Hansen, F.A.; Santigosa-Murillo, E.; Ramos-Payán, M.; Muñoz, M.; Øiestad, E.L.; Pedersen-Bjergaard, S. Electromembrane extraction using deep eutectic solvents as the liquid membrane. Anal. Chim. Acta 2021, 1143, 109–116. [Google Scholar] [CrossRef]
  76. Chen, Z.; Reznicek, W.D.; Wan, C. Deep eutectic solvent pretreatment enabling full utilization of switchgrass. Bioresour. Technol. 2018, 263, 40–48. [Google Scholar] [CrossRef] [PubMed]
  77. Huang, Y.; Feng, F.; Jiang, J.; Qiao, Y.; Wu, T.; Voglmeir, J.; Chen, Z.-G. Green and efficient extraction of rutin from tartary buckwheat hull by using natural deep eutectic solvents. Food Chem. 2017, 221, 1400–1405. [Google Scholar] [CrossRef]
  78. Dai, Y.; Rozema, E.; Verpoorte, R.; Choi, Y.H. Application of natural deep eutectic solvents to the extraction of anthocyanins from Catharanthus roseus with high extractability and stability replacing conventional organic solvents. J. Chromatogr. A 2016, 1434, 50–56. [Google Scholar] [CrossRef] [PubMed]
  79. Matong, J.M.; Nyaba, L.; Nomngongo, P.N. Determination of As, Cr, Mo, Sb, Se and V in agricultural soil samples by inductively coupled plasma optical emission spectrometry after simple and rapid solvent extraction using choline chloride-oxalic acid deep eutectic solvent. Ecotoxicol. Environ. Saf. 2017, 135, 152–157. [Google Scholar] [CrossRef]
  80. Bağda, E.; Altundağ, H.; Tüzen, M.; Soylak, M. A Novel Selective Deep Eutectic Solvent Extraction Method for Versatile Determination of Copper in Sediment Samples by ICP-OES. Bull. Environ. Contam. Toxicol. 2017, 99, 264–269. [Google Scholar] [CrossRef]
  81. Rajabi, M.; Ghassab, N.; Hemmati, M.; Asghari, A. Emulsification microextraction of amphetamine and methamphetamine in complex matrices using an up-to-date generation of eco-friendly and relatively hydrophobic deep eutectic solvent. J. Chromatogr. A 2018, 1576, 1–9. [Google Scholar] [CrossRef]
  82. Florindo, C.; Branco, L.; Marrucho, I. Development of hydrophobic deep eutectic solvents for extraction of pesticides from aqueous environments. Fluid Phase Equilibria 2017, 448, 135–142. [Google Scholar] [CrossRef]
  83. Nedaei, M.; Zarei, A.R.; Ghorbanian, S.A. Miniaturized matrix solid-phase dispersion based on deep eutectic solvent and carbon nitride associated with high-performance liquid chromatography: A new feasibility for extraction and determination of trace nitrotoluene pollutants in soil samples. J. Chromatogr. A 2019, 1601, 35–44. [Google Scholar] [CrossRef] [PubMed]
  84. Kachangoon, R.; Vichapong, J.; Santaladchaiyakit, Y.; Burakham, R.; Srijaranai, S. An Eco-Friendly Hydrophobic Deep Eutectic Solvent-Based Dispersive Liquid–Liquid Microextraction for the Determination of Neonicotinoid Insecticide Residues in Water, Soil and Egg Yolk Samples. Molecules 2020, 25, 2785. [Google Scholar] [CrossRef] [PubMed]
  85. Zhang, K.; Liu, C.; Li, S.; Fan, J. A hydrophobic deep eutectic solvent based vortex-assisted liquid-liquid microextraction for the determination of formaldehyde from biological and indoor air samples by high performance liquid chromatography. J. Chromatogr. A 2019, 1589, 39–46. [Google Scholar] [CrossRef]
  86. Ruggeri, S.; Poletti, F.; Zanardi, C.; Pigani, L.; Zanfrognini, B.; Corsi, E.; Dossi, N.; Salomäki, M.; Kivelä, H.; Lukkari, J.; et al. Chemical and electrochemical properties of a hydrophobic deep eutectic solvent. Electrochimica Acta 2019, 295, 124–129. [Google Scholar] [CrossRef]
  87. Yousefi, S.M.; Shemirani, F.; Ghorbanian, S.A. Hydrophobic Deep Eutectic Solvents in Developing Microextraction Methods Based on Solidification of Floating Drop: Application to the Trace HPLC/FLD Determination of PAHs. Chromatographia 2018, 81, 1201–1211. [Google Scholar] [CrossRef]
  88. Tereshatov, E.E.; Boltoeva, M.Y.; Folden, C.M. First evidence of metal transfer into hydrophobic deep eutectic and low-transition-temperature mixtures: Indium extraction from hydrochloric and oxalic acids. Green Chem. 2016, 18, 4616–4622. [Google Scholar] [CrossRef]
  89. Schaeffer, N.; Martins, M.A.R.; Neves, C.M.S.S.; Pinho, S.P.; Coutinho, J.A.P. Sustainable hydrophobic terpene-based eutectic solvents for the extraction and separation of metals. Chem. Commun. 2018, 54, 8104–8107. [Google Scholar] [CrossRef]
  90. Chen, Y.-C.; Ao, Y.-T.; Ding, W.-H. Determination of microcystins in water samples by deep eutectic solvent-based vortex-assisted liquid–liquid microextraction coupled with ultrahigh-performance liquid chromatography-high resolution mass spectrometry. RSC Adv. 2019, 9, 38669–38676. [Google Scholar] [CrossRef]
  91. Ao, Y.-T.; Chen, Y.-C.; Ding, W.-H. Deep eutectic solvent-based ultrasound-assisted emulsification microextraction for the rapid determination of benzotriazole and benzothiazole derivatives in surface water samples. J. Hazard. Mater. 2021, 401, 123383. [Google Scholar] [CrossRef] [PubMed]
  92. Shishov, A.; Pochivalov, A.; Nugbienyo, L.; Andruch, V.; Bulatov, A. Deep eutectic solvents are not only effective extractants. TrAC Trends Anal. Chem. 2020, 129, 115956. [Google Scholar] [CrossRef]
  93. Habibi, E.; Ghanemi, K.; Fallah-Mehrjardi, M.; Dadolahi-Sohrab, A. A novel digestion method based on a choline chloride–oxalic acid deep eutectic solvent for determining Cu, Fe, and Zn in fish samples. Anal. Chim. Acta 2013, 762, 61–67. [Google Scholar] [CrossRef] [PubMed]
  94. Ghanemi, K.; Navidi, M.-A.; Fallah-Mehrjardi, M.; Dadolahi-Sohrab, A. Ultra-fast microwave-assisted digestion in choline chloride–oxalic acid deep eutectic solvent for determining Cu, Fe, Ni and Zn in marine biological samples. Anal. Methods 2014, 6, 1774–1781. [Google Scholar] [CrossRef]
  95. Santana, A.P.; Andrade, D.F.; Vargas, J.A.M.; Amaral, C.; de Oliveira, A.P.; Gonzalez, M.H. Natural deep eutectic solvents for sample preparation prior to elemental analysis by plasma-based techniques. Talanta 2019, 199, 361–369. [Google Scholar] [CrossRef]
  96. Helalat–Nezhad, Z.; Ghanemi, K.; Fallah–Mehrjardi, M. Dissolution of biological samples in deep eutectic solvents: An approach for extraction of polycyclic aromatic hydrocarbons followed by liquid chromatography-fluorescence detection. J. Chromatogr. A 2015, 1394, 46–53. [Google Scholar] [CrossRef]
  97. Rastbood, S.; Hadjmohammadi, M.R.; Majidi, S.M. Development of a magnetic dispersive micro-solid-phase extraction method based on a deep eutectic solvent as a carrier for the rapid determination of meloxicam in biological samples. Anal. Methods 2020, 12, 2331–2337. [Google Scholar] [CrossRef] [PubMed]
  98. Dai, Y.; Verpoorte, R.; Choi, Y.H. Natural deep eutectic solvents providing enhanced stability of natural colorants from safflower (Carthamus tinctorius). Food Chem. 2014, 159, 116–121. [Google Scholar] [CrossRef] [PubMed]
  99. Song, M.; Jiang, Y.; Liu, Q.; Tian, Y.; Liu, Y.; Xu, X.; Kang, M. Catchment versus Riparian Buffers: Which Land Use Spatial Scales Have the Greatest Ability to Explain Water Quality Changes in a Typical Temperate Watershed? Water 2021, 13, 1758. [Google Scholar] [CrossRef]
  100. Vorobyev, S.; Kolesnichenko, Y.; Korets, M.; Pokrovsky, O. Testing Landscape, Climate and Lithology Impact on Carbon, Major and Trace Elements of the Lena River and Its Tributaries during a Spring Flood Period. Water 2021, 13, 2093. [Google Scholar] [CrossRef]
  101. Cunha, S.C.; Fernandes, J.O. Extraction techniques with deep eutectic solvents. TrAC Trends Anal. Chem. 2018, 105, 225–239. [Google Scholar] [CrossRef]
  102. Liang, X.; Zhu, Y.; Qi, B.; Li, S.; Luo, J.; Wan, Y. Structure-property-performance relationships of lactic acid-based deep eutectic solvents with different hydrogen bond acceptors for corn stover pretreatment. Bioresour. Technol. 2021, 336, 125312. [Google Scholar] [CrossRef] [PubMed]
Figure 1. Number of papers published during 2008–2020 in Web of Science (Keywords: “deep eutectic solvents”, “hydrophobic deep eutectic solvents”, and “nature deep eutectic solvents” with “extraction”).
Figure 1. Number of papers published during 2008–2020 in Web of Science (Keywords: “deep eutectic solvents”, “hydrophobic deep eutectic solvents”, and “nature deep eutectic solvents” with “extraction”).
Water 14 00046 g001
Figure 2. Classification of DESs according to their composition.
Figure 2. Classification of DESs according to their composition.
Water 14 00046 g002
Table 2. Compilation of application of DESs in extraction from various types of environmental matrix.
Table 2. Compilation of application of DESs in extraction from various types of environmental matrix.
Sample MatrixAnalytesDES Composition (Mole Ratio)Method of
Extraction
Instrumental
Analysis
LODs
Hydrophilic deep eutectic solvents
Waters (tap, lake, waste) [58]Cr (III/VI)ChCl/phenol (1:3)UALMEFAAS5.5 ug/L
Switchgrass [76]Cellulose-rich pulp, lignin, and xylose-rich liquor.ChCl/glycerol (1:2) HPLC-RID, NMR, ATR-FTIR, XRD
Tartary buckwheat
Hulls [77]
Flavonoid (rutin)ChCl/glycerol (1:1)UAMEHPLC-UV
Flower petals [78]AnthocyaninsLactic acid/glucose
1,2-propanediol/ChCl
UAEHPLC-DAD
Soil samples [79]As, Cr, Mo, Sb, Se and VChCl/oxalic acid UAEICP-OES0.009–0.1 ug/g
Sediment samples [80]CuChCl/oxalic acid (1.5:1)SLEICP-OES1.2 ug/L
Hydrophobic deep eutectic solvents
Wastewater and human plasma [81]Amphetamine-type stimulantsChCl/phenylethanol (1:4)AA-EMEHPLC-UV2.0–5.0 ng/mL
Surface water [49]FluoroquinolonesThymol/Heptanoic acid (2:1)In situ LPMEHPLC-UV3 ng/mL
Wastewater [82]NeonicotinoidsDL-menthol/organic acidsLLEUV–vis
River water [56]BP, BP-1, BP-3, BP-6, 4OH-BPDL-menthol/decanoic acid (1:1)Air-assisted DLLMEHPLC-DAD0.05–0.2 ng/mL
Water and soil samples [51]ExplosivesDL-menthol/decanoic acid (1:2)Ferrofluid-based LPMEHPLC-UV0.22–0.91, 0.01–0.04 mg/mL
Soil samples [83]NitrotolueneBorneol/mentholMSPDHPLC-UV0.12–0.33 ug/g
Water, soil, egg yolk samples [84]InsecticideN4444-Br/decanoic acidDLLMEHPLC-UV0.001–0.003 ug/mL
Water, and biological samples [55]NitriteN8851-Cl/oleic acid (1:2)Vortex-assisted DLLMEHPLC-UV0.2 ng/mL
Biological and indoor air sample [85]FormaldehydeN8851-Cl/4-cyanophenol (1:1)VA-LLMEHPLC-DAD0.2 ng/mL
AA-EME: air agitated-emulsification microextraction; MSPD: matrix solid-phase dispersion.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Back to TopTop