Quality assessment of environmental water by a simple and fast non-ionic hydrophobic natural deep eutectic solvent-based extraction procedure combined with liquid chromatography tandem mass spectrometry for the determination of plastic migrants

Developing of an eco-friendly liquid-liquid microextraction method by using menthol-based hydrophobic deep eutectic solvent for determination of basic fuchsin dye: assessment of the greenness profile

Herein, we aimed to develop a new environmentally friendly liquid-liquid microextraction (LLME) method based on hydrophobic deep eutectic solvent (hDES) synthesized using biodegradable dl-menthol and decanoic acid for the spectrophotometric determination of toxic basic fuchsin dye in environmental water samples. The parameters affecting the extraction efficiency such as pH, mole ratio, and volume of hDES (1:2) and type and volume of organic solvent, sample volume, times of vortex, ultrasonic bath and centrifuge, ionic strength, and matrix effect were investigated and optimized. Under optimal conditions, the calibration curve showed linearity in the range of 7.4-167 μg L-1 with a coefficient of determination of 0.9994. The limit of detection, intra-day and inter-day precision, and recovery values were 2.25 μg L-1, 2.46% and 4.45%, and 105 ± 3%, respectively. The preconcentration and enrichment factors were found to be 30 and 61.5, respectively. The proposed hDES-LLME methodology was successfully applied to the environmental water samples to detect toxic BF dye (95-105%). Finally, the ecological impact of the suggested method was evaluated using the analytical eco-scale (PPS:88), complementary green analytical procedure indexe (ComplexGAPI), and the Analytical GREEnness tool (0.63). The assessment results showed that the presented analytical method can be regarded as a green LLME approach for the determination of the BF in water.

Analysis and remediation of phthalates in aquatic matrices: current perspectives

Phthalic acid esters (PAEs) are high production volume chemicals used extensively as plasticizers, to increase the flexibility of the main polymer. They are reported to leach into their surroundings from plastic products and are now a ubiquitous environmental contaminant. Phthalate levels have been determined in several environmental matrices, especially in water. These levels serve as an indicator of plasticizer abuse and plastic pollution, and also serve as a route of exposure to different species including humans. Reports published on effects of different PAEs on experimental models demonstrate their carcinogenic, teratogenic, reproductive, and endocrine disruptive effects. Therefore, regular monitoring and remediation of environmental water samples is essential to ascertain their hazard quotient and daily exposure levels. This review summarises the extraction and detection techniques available for phthalate analysis in water samples such as chromatography, biosensors, immunoassays, and spectroscopy. Current remediation strategies for phthalate removal such as adsorption, advanced oxidation, and microbial degradation have also been highlighted.

Critical overview on the use of hydrophobic (deep) eutectic solvents for the extraction of organic pollutants in complex matrices

During the last decades, many efforts have been devoted to the adaptation of sample preparation techniques and methods to the principles of Green Analytical Chemistry. Among them, this article review focusses on those aimed to green the solvents involved in sample treatment. Research in this field started in the late 1990s with the synthesis of room temperature ionic liquids, which were later replaced by the deep eutectic solvents (DESs). During the last years, a subclass of DESs, the so-called hydrophobic deep eutectic solvents (HDESs) have attracted attention. HDESs have contributed to circumventing some of the limitations of early-synthesised hydrophilic DESs regarding the cost of raw materials, the simplicity of synthesis, and the biocompatibility and, apparently, the biodegradability of the mixtures. In addition, these mixtures allowed the treatment of aqueous samples and the extraction of non-polar analytes. This article discusses fundamental aspects regarding the nomenclature used concerning HDESs, summarises the main physicochemical properties of these mixtures, and through discussion of key application studies, describes current progress in the use of these green solvents for the extraction of trace organic contaminants from a variety of matrices. Remaining gaps and possible lines of future development in this emerging, active and attractive research area are also identified and critically discussed.

Deep eutectic solvents with solid supports used in microextraction processes applied for endocrine-disrupting chemicals

The determination of endocrine-disrupting chemicals (EDCs) has become one of the biggest challenges in Analytical Chemistry. Due to the low concentration of these compounds in different kinds of samples, it becomes necessary to employ efficient sample preparation methods and sensitive measurement techniques to achieve low limits of detection. This issue becomes even more struggling when the principles of the Green Analytical Chemistry are added to the equation, since finding an efficient sample preparation method with low damaging properties for health and environment may become laborious. Recently, deep eutectic solvents (DESs) have been proposed as the most promising green kind of solvents, but also with excellent analytical properties due to the possibility of custom preparation with different components to modify their polarity, viscosity or aromaticity among others. However, conventional extraction techniques using DESs as extraction solvents may not be enough to overcome challenges in analysing trace levels of EDCs. In this sense, combination of DESs with solid supports could be seen as a potential solution to this issue allowing, in different ways, to determine lower concentrations of EDCs. In that aim, the main purpose of this review is the study of the different strategies with solid supports used along with DESs to perform the determination of EDCs, comparing their advantages and drawbacks against conventional DES-based extraction methods.

Deep eutectic solvents for the determination of endocrine disrupting chemicals

The harmful effects of endocrine disrupting chemicals (EDCs) to humans and other organisms in the environment have been well established over the years, and more studies are ongoing to classify other chemicals that have the potential to alter or disrupt the regular function of the endocrine system. In addition to toxicological studies, analytical detection systems are progressively being improved to facilitate accurate determination of EDCs in biological, environmental and food samples. Recent microextraction methods have focused on the use of green chemicals that are safe for analytical applications, and present very low or no toxicity upon disposal. Deep eutectic solvents (DESs) have emerged as one of the viable alternatives to the conventional hazardous solvents, and their unique properties make them very useful in different applications. Notably, the use of renewable sources to prepare DESs leads to highly biodegradable products that mitigate negative ecological impacts. This review presents an overview of both organic and inorganic EDCs and their ramifications on human health. It also presents the fundamental principles of liquid phase and solid phase microextraction methods, and gives a comprehensive account of the use of DESs for the determination of EDCs in various samples.

Vortex-assisted hydrophobic natural deep eutectic solvent liquid-liquid microextraction for the removal of silver ions from environmental water

This study presents a novel approach for the quantification of silver ions in environmental water through the utilization of liquid-liquid microextraction, employing natural deep eutectic solvents in conjunction with inductively coupled plasma emission spectroscopy. The extracted solvent was characterized by Fourier transform infrared spectroscopy (FT-IR). The impact of various extractant types, extractant molar ratio, extractant volume, extraction time, and salt concentration on the efficacy of silver ion extraction was investigated. The findings indicate that the optimal extraction efficiency was attained by utilizing a 5-mL aqueous solution volume, containing 1000 μL thymol/lactic acid NADES 1:3, a salt concentration of 1 mg mL-1, a pH value of 4, and a vortex time of 4 min. Upon implementing the optimized experimental conditions, the recovery of target metal ions was from 96.9 to 101.0%. The relative standard deviations were observed to be within the range of 1.5 to 2.7%. The present study demonstrates the reproducibility, accuracy, and reliability of the method for detecting silver ions in environmental water, with linear range of 5~1000 ng mL-1 and limits of detection (LOD) and limits of quantification (LOQ) of 1.52 ng mL-1 and 5.02 ng mL-1, respectively.

Assessment of endocrine disruptor pollutants and their metabolites in environmental water samples using a sustainable natural deep eutectic solvent-based analytical methodology

In this work, an evaluation of the occurrence of fifteen phthalates, four metabolites and one adipate in different groundwater, seawater and wastewater samples has been carried out due to their relevance on human health as they act as endocrine disruptors. For this purpose, a sustainable, fast and easy-handling vortex-assisted liquid-liquid microextraction method using a natural hydrophobic deep eutectic solvent based on menthol and carvacrol as extraction agent, combined with ultra-high performance liquid chromatography-mass spectrometry technique, has been developed and applied for the first time. An optimization was performed to evaluate four important factors affecting the extraction performance, and an analytical validation was carried out in terms of matrix effect, linearity, extraction efficiency, and sensitivity. Recovery values were obtained in the range 72-119% for all analytes (except for monoethyl phthalate: 61.1-72.3%) with relative standard deviation values lower than 17%. Limits of quantification were found between 0.91 and 8.09 μg L-1. As a result of the assessment of 31 different environmental water samples, monoethyl phthalate, diethyl phthalate, dibutyl phthalate and bis (2-ethylhexyl) phthalate were detected and quantified at different concentrations in the range 2.59-21.17 μg L-1 in 6 samples, and diallyl phthalate, butyl benzyl phthalate, dipentyl phthalate, dicyclohexyl phthalate, dihexyl phthalate and bis (2-ethylhexyl) adipate were detected in 20 more, showing the exposition of the population to these hazardous substances.

International Comparison, Risk Assessment, and Prioritisation of 26 Endocrine Disrupting Compounds in Three European River Catchments in the UK, Ireland, and Spain

Endocrine-disrupting compounds (EDCs) constitute a wide variety of chemistries with diverse properties that may/can pose risks to both humans and the environment. Herein, a total of 26 compounds, including steroids, flame retardants, and plasticizers, were monitored in three major and heavily urbanized river catchments: the R. Liffey (Ireland), the R. Thames (UK), and the R. Ter (Spain), by using a single solid-phase extraction liquid chromatography-mass spectrometry (SPE-LC-MS/MS) method. Occurrence and frequency rates were investigated across all locations over a 10-week period, with the highest concentration obtained for the flame retardant tris(2-chloroethyl) phosphate (TCEP) at 4767 ng∙L-1 in the R. Thames in Central London. Geographical variations were observed between sites and were partially explained using principal component analysis (PCA) and hierarchical cluster analysis (HCA). In particular, discrimination between the R. Ter and the R. Thames was observed based on the presence and concentration of flame retardants, benzotriazole, and steroids. Environmental risk assessment (ERA) across sites showed that caffeine, a chemical marker, and bisphenol A (BPA), a plasticizer, were classified as high-risk for the R. Liffey and R. Thames, based on relative risk quotients (rRQs), and that caffeine was classified as high-risk for the R. Ter, based on RQs. The total risks at each location, namely ΣRQriver, and ΣrRQriver, were: 361, 455, and 723 for the rivers Liffey, Thames, and Ter, respectively. Caffeine, as expected, was ubiquitous in all 3 urban areas, though with the highest RQ observed in the R. Ter. High contributions of BPA were also observed across the three matrices. Therefore, these two compounds should be prioritized independently of location. This study represents a comprehensive EDC monitoring comparison between different European cities based on a single analytical method, which allowed for a geographically independent ERA prioritization to be performed.

Everything You Wanted to Know about Deep Eutectic Solvents but Were Afraid to Be Told

Are deep eutectic solvents (DESs) a promising alternative to conventional solvents? Perhaps, but their development is hindered by a plethora of misconceptions. These are carefully analyzed here, beginning with the very meaning of DESs, which has strayed far beyond its original scope of eutectic mixtures of Lewis or Brønsted acids and bases. Instead, a definition that is grounded on thermodynamic principles and distinguishes between eutectic and deep eutectic is encouraged, and the types of precursors that can be used to prepare DESs are reviewed. Landmark works surrounding the sustainability, stability, toxicity, and biodegradability of these solvents are also discussed, revealing piling evidence that numerous DESs reported thus far, particularly those that are choline based, lack sufficient sustainability-related traits to be considered green solvents. Finally, emerging DES applications are reviewed, emphasizing their most remarkable feature: the ability to liquefy a solid compound with a target property, allowing its use as a liquid solvent.

Monitoring of the presence of plasticizers and effect of temperature and storage time in bottled water using a green liquid-liquid microextraction method

In this work, a natural deep eutectic solvent was used for the liquid-liquid microextraction of fourteen phthalates and one adipate from bottled waters. The methodology was validated in terms of matrix effect, linearity, recovery, and limits of quantification (LOQs). Optimum extraction conditions (10 mL of water at pH 8.0 with 100 μL of thymol: menthol 2:1 (n/n) as solvent) provided satisfactory determination coefficients (≥ 0.9977), recovery values (82-127%), and LOQs (0.018-0.523 μg/L). The effects of temperature and storage time on plasticizer presence were studied for 36 different brands stored at 4 °C, room temperature, and 45 °C, and analyzed at 0, 24, 48, 72 h, and 1 week. Only diethyl-, dibutyl-, bis-(2-ethylhexyl) phthalates, and bis-(2-ethylhexyl) adipate were detected. The results showed that there is no relationship between the storage conditions, the bottle material or water carbonation, and the occurrence of these plasticizers, suggesting that residues are introduced during production or by the water supply. The estimated daily intake was lower than the total daily intake set by the European Food Safety Authority.

Applications of Deep Eutectic Solvents in Sample Preparation and Extraction of Organic Molecules

The use of deep eutectic solvents (DES) is on the rise worldwide because of the astounding properties they offer, such as simplicity of synthesis and utilization, low-cost, and environmental friendliness, which can, without a doubt, replace conventional solvents used in heaps. In this review, the focus will be on the usage of DES in extracting a substantial variety of organic compounds from different sample matrices, which not only exhibit great results but surpass the analytical performance of conventional solvents. Moreover, the properties of the most commonly used DES will be summarized.

Pressurized natural deep eutectic solvents: An alternative approach to agro-soy by-products

Soybeans are mainly used for food and biodiesel production. It is estimated that soy crops worldwide will leave about 651 million metric tons of branches, leaves, pods, and roots on the ground post-harvesting in 2022/23. These by-products might serve as largely available and cheap source of high added-value metabolites, such as flavonoids, isoflavonoids, and other phenolic compounds. This work aimed to explore green approaches based on the use of pressurized and gas expanded-liquid extraction combined with natural deep eutectic solvents (NADESs) to achieve phenolic-rich extracts from soy by-products. The total phenolic and flavonoid contents of the generated extracts were quantified and compared with conventional solvents and techniques. Pressurized liquid extraction (PLE) with choline chloride/citric acid/water (1:1:11 – molar ratio) at 120°C, 100 bar, and 20 min, resulted in an optimized condition to generate phenolic and flavonoid-rich fractions of soy by-products. The individual parts of soy were extracted under these conditions, with their metabolic profile obtained by UHPLC-ESI-QToF-MS/MS and potential antioxidant properties by ROS scavenging capacity. Extracts of soy roots presented the highest antioxidant capacity (207.48 ± 40.23 mg AA/g), three times higher than soybean extracts (68.96 ± 12.30). Furthermore, Hansen solubility parameters (HSPs) were applied to select natural hydrophobic deep eutectic solvents (NaHDES) as substituents for n-heptane to defat soybeans. Extractions applying NaHDES candidates achieved a similar yield and chromatography profile (GC-QToF-MS) to n-heptane extracts.

Analysis of alkylphenols, bisphenols and alkylphenol ethoxylates in microbial-fermented functional beverages and bottled water: Optimization of a dispersive liquid-liquid microextraction protocol based on natural hydrophobic deep eutectic solvents

In this work, the analysis of alkylphenols, bisphenols and alkylphenol ethoxylates in bottled waters, kombuchas and water kefir was performed through a vortex-assisted dispersive liquid-liquid microextraction method based on a natural hydrophobic eutectic solvent. For this purpose, mixtures of monoterpenes and fatty acids were employed. Different factors affecting extraction were optimized and the method was validated in terms of matrix effect, linearity, limits of detection and recovery. Recovery values varied between 70.0 and 124.3% (except for 4-tert-butylphenol: 67.0% and 4-n-nonylphenol: 60.8% in water kefir) and limits of detection were in the range 0.10 ng/L - 2.99 µg/L. Finally, 8 bottled waters, 8 kombuchas and 4 water kefirs were analyzed and 4-tert-octylphenol monoethoxylate was detected in water (20.28 ± 0.99 - 62.08 ± 3.63 µg/L). This is the first application analyzing xenobiotic contaminants in kombucha and water kefir and the first time in which the three types of compounds are simultaneously extracted by dispersive liquid-liquid microextraction.

Liquefying Flavonoids with Terpenoids through Deep Eutectic Solvent Formation

The formation of deep eutectic solvents (DES) is tied to negative deviations to ideality caused by the establishment of stronger interactions in the mixture than in the pure DES precursors. This work tested thymol and menthol as hydrogen bond donors when combined with different flavonoids. Negative deviations from ideality were observed upon mixing thymol with either flavone or flavanone, two parent flavonoids that only have hydrogen bond acceptor (HBA) groups, thus forming non-ionic DES (Type V). On the other hand, the menthol systems with the same compounds generally showed positive deviations from ideality. That was also the case with the mixtures containing the more complex hydroxylated flavonoid, hesperetin, which resulted in positive deviations when mixed with either thymol or menthol. COSMO-RS successfully predicted the behavior of the solid-liquid phase diagram of the studied systems, allowing for evaluation of the impact of the different contributions to the intermolecular interactions, and proving to be a good tool for the design of DES.

Hybrid Materials Formed with Green Metal-Organic Frameworks and Polystyrene as Sorbents in Dispersive Micro-Solid-Phase Extraction for Determining Personal Care Products in Micellar Cosmetics

Hybrid materials based on polystyrene (PS) and green metal-organic frameworks (MOFs) were synthesized, characterized, and evaluated as potential sorbents in dispersive micro-solid-phase extraction (µ-dSPE). Among the resulting materials, the hybrid PS/DUT-67(Zr) was selected as the adequate extraction material for the monitoring of six personal care products in micellar cosmetic samples, combining the µ-dSPE method with ultra-high performance liquid chromatography (UHPLC) coupled to ultraviolet/visible detection (UV/Vis). Univariate studies and a factorial design were performed in the optimization of the microextraction procedure. The compromise optimum extraction conditions included 20 mg of PS/DUT-67(Zr) for 10 mL of sample, 2 min of extraction time, and two desorption steps using 100 µL of acetonitrile and 5 min assisted by vortex in each one. The validated μ-dSPE-UHPLC-UV/Vis method presented limits of detection and quantification down to 3.00 and 10.0 μg·L⁻¹, respectively. The inter-day precision values were lower than 23.5 and 21.2% for concentration levels of 75 μg·L⁻¹ and 650 μg·L⁻¹, respectively. The hydrophobicity of the resulting PS/DUT-67(Zr) material was crucial for the improvement of its extraction capacity in comparison with its unitary components, showing the advantages of combining MOFs with other materials, getting new sorbents with interesting properties.

Sensitive determination of vincristine in plasma of children with leukaemia using vortex-assisted dispersive liquid-liquid microextraction based on hydrophobic deep eutectic solvent

Vincristine has a wide spectrum of clinical activity and is currently used in the treatment of leukemia. Despite its high therapeutic properties, vincristine has common side effects. Accordingly, it is desirable to determine vincristine in plasma for the use of the drug with strict monitoring. In the present research, for the first time a hydrophobic deep eutectic solvent (DES) composed of methyltrioctylammonium chloride (MTOAC) and n-butanol in a molar ratio of 1 : 3 was used as the extractant in dispersive liquid–liquid microextraction (DLLME) for the extraction and determination of vincristine in the plasma of children with leukemia prior to its analysis by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). Under optimal experimental conditions, the method showed good linearity with a correlation coefficient (R²) of 0.9986 in the linear range of 0.06–300 μg L⁻¹, low limit of detection of 0.02 μg L⁻¹ and acceptable extraction efficiency (EE) of 88.4%. In the final stage of the study, this proposed technique was successfully applied to determine vincristine in real plasma, and the obtained results demonstrated the ability of the synthesized DES to extract drugs from biological fluids.

Vincristine has a wide spectrum of clinical activity and is currently used in the treatment of leukemia.

Application of a Liquid-Liquid Microextraction Method Based on a Natural Hydrophobic Deep Eutectic Solvent for the Extraction of Plastic Migrants from Kombuchas

A vortex-assisted liquid-liquid microextraction, based on a natural hydrophobic deep eutectic solvent made from the monoterpene thymol and octanoic fatty acid, was employed for the analysis of 11 phthalate esters and one adipate in kombucha (a tea-based fermented beverage). Separation and determination were performed using an ultra-high performance liquid chromatography (UHPLC) system coupled to a single quadrupole mass spectrometer. Confirmatory analyses were carried out through UHPLC tandem mass spectrometry. The full method was validated in terms of matrix effect, matrix-matched calibration, sensitivity, recovery, limits of detection and quantification and repeatability. Satisfactory determination coefficients for quadratic calibration curves (≥0.9938), recovery values (67–120%) and limits of detection (0.07–5.45 µg/L) were obtained. Analysis of 26 kombucha samples reported concentrations for dibutyl phthalate and dimethyl phthalate in the range between the limit of quantification (LOQ) and 16.18 ± 1.14 µg/L, although these phthalates were also detected under the LOQ in some of the analyzed samples. Only one of the samples bottled in plastic containers (7) did not present residues while only five of the 19 samples in glass bottles contained any plasticizer. However, the highest concentration was found in a kombucha bottled in food-grade glass. This work represents the first application in which phthalates and adipates are analyzed in kombuchas.

Properties and Kinetics of Selective Zinc Leaching with Choline Chloride and Urea

A choline chloride-urea (ChCl-urea) deep eutectic solvent (DES) was used to experimentally investigate the secondary recovery of zinc from zinc-bearing dust sludge via a leaching process. The effects of varying the liquid–solid ratio, leaching temperature, stirring speed, and leaching time on the zinc leaching efficiency were determined, and the optimum values of these parameters were found to be 15:1, 90 °C, 400 rpm, and 600 min, respectively, at which a leaching efficiency of 86.87% was achieved. XRF and EDS analyses confirmed that the zinc content in the sludge decreased noticeably after leaching, while those of other elements did not, indicating the selective and efficient leaching of zinc. A study of the leaching kinetics showed that the reaction conforms to the nuclear shrinkage model without solid product layer formation, and the calculated apparent activation energy is 22.16 kJ/mol.

Recent Applications of Deep Eutectic Solvents in Environmental Analysis

The incessant generation of toxic waste and the growing concern over the environment have led the scientific community to delve into the search for more sustainable systems. In this regard, the application of deep eutectic solvents (DESs) has become one of the main strategies in green chemistry. These solvents have emerged as a promising alternative to conventional toxic solvents and even to the well-known ionic liquids. Their unique properties, components availability, and easy preparation, among others, have led to a new trend within the scientific community and industry, based on the use of these up-and-coming solvents not only in science but also in quotidian life. Among the areas that have benefited from the advantages of DESs is analytical chemistry, in which they have been largely used for sample preparation, including the extraction and determination of organic and inorganic compounds from environmental samples. The considerable number of applications developed in the last year in this field and the increasing generation of new data necessitate the continuous updating of the literature. This review pretends to compile the most relevant applications of DESs in environmental analysis and critically discuss them to provide a global vision about the advantages and drawbacks/limitations of these neoteric solvents in the area of environmental analysis.