Evaluation of fatty acid/alcohol-based hydrophobic deep eutectic solvents as media for extracting antibiotics from environmental water

Hydrophobic Deep Eutectic Solvents as New Supported Liquid Membranes for Extraction of β-Blockers by Hollow Fiber-Electromembrane Extraction

In this work, an electromembrane extraction method is presented to extract some β-blockers in biological samples. A new hydrophobic deep eutectic solvent, as a green solvent, was synthesized. The hydrophobic deep eutectic solvent was immobilized in the wall pores of the hollow fiber membrane and used as a supported liquid membrane. β-Blockers were transported from the sample solution through an SLM, including tris-(2-ethylhexyl) phosphate, into the acceptor phase located in the lumen of the hollow fiber. High-performance liquid chromatography with ultraviolet detection has been used to separate and analyze the β-blockers. Effective parameters on the extraction efficiency of the β-blockers such as hydrophobic deep eutectic solvent molar ratio (2:1), extraction voltage (75 V), type of ion carrier and its concentration (tris-(2-ethylhexyl) phosphate, 5%), pH of donor and acceptor phases (ultrapure water and 100 mM of HCl), hollow fiber length (7 cm), extraction time (20 min), stirring speed of sample solution (600 rpm), and salt effect (0%) were investigated and optimized. The method provides a decent linearity by the coefficient of determination values higher than 0.9946. Limits of detection were in the range of 0.25-3.3 ng mL-1, and limits of quantification were found in the range of 0.75-10.0 ng mL-1 in water. Finally, the method was successfully used to determine the β-blockers concentrations in real urine and plasma samples with relative recoveries between 90.6% and 108.6%.

Hydrophobic binary mixtures containing amphotericin B as lipophilic solutions for the treatment of cutaneous leishmaniasis

Cutaneous leishmaniasis, caused by Leishmania parasites, requires treatments with fewer side effects than those currently available. The development of a topical solution based on amphotericin B (AmB) was pursued. The considerable interest in deep eutectic solvents (DESs) and their remarkable advantages inspired the search for a suitable hydrophobic excipient. Various mixtures based on commonly used hydrogen bond donors (HBDs) and acceptors (HBAs) for DES preparations were explored. Initial physical and in-vitro screenings showed the potential of quaternary phosphonium salt-based mixtures. Through thermal analysis, it was determined that most of these mixtures did not exhibit eutectic behavior. X-ray scattering studies revealed a sponge-like nanoscale structure. The most promising formulation, based on a combination of trihexyl(tetradecyl)phosphonium chloride and 1-oleoyl-rac-glycerol, showed no deleterious effects through histological evaluation. AmB was fully solubilized at concentrations between 0.5 and 0.8 mg·mL-1, depending on the formulation. The monomeric state of AmB was observed by circular dichroism. In-vitro irritation tests demonstrated acceptable viability for AmB-based formulations up to 0.5 mg·mL-1. Additionally, an ex-vivo penetration study on pig ear skin revealed no transcutaneous passage, confirming AmB retention in healthy, unaffected skin.

Deep Eutectic Solvents for Extraction and Preconcentration of Organic and Inorganic Species in Water and Food Samples: A Review

Deep eutectic solvents (DESs) have been developed as green solvents and these are capable as alternatives to conventional solvents used for the extraction of organic and inorganic species from food and water samples. The continuous generation of contaminated waste and increasing concern for the human health and environment have compelled the scientific community to investigate more ecological schemes. In this concern, the use of DESs have developed in one of the chief approach in the field of chemistry. These solvents have appeared as a capable substitute to conventional hazardous solvents and ionic liquids. The DESs has distinctive properties, easy preparation and components availability. It is not only used in scienctific fields but also used in quotidian life. There are many advantages of DESs in analytical chemistry, they are largely used for extraction and determination of inorganic and organic compounds from different samples. In previous a few years, several advanced researches have been focused on the separation and preconcentration of low level of pollutants using DESs as the extractants. This review summarizes the use of DESs in the separation and preconcentration of organic and inorganic species from water and food samples using various microextraction processes.

Harnessing therapeutic deep eutectic solvents in self-emulsifying systems to improve CBD delivery

In this study, Cannabidiol crystals (CBD) were used as a BCS class II model drug to generate a novel therapeutic deep eutectic solvent (THEDES) with easy preparation using caprylic acid (CA). The hydrogen bonding interaction was confirmed by different techniques such as FT-IR and NMR, resulting in a hydrophobic system suitable for liquid formulations. The CBD-based THEDES, combined with a specific mixture of surfactants and co-surfactants, successfully formed a self-emulsifying drug delivery system (SEDDS) that generated uniform nano-sized droplets once dispersed in water. Hence, the THEDES showed compatibility with the self-emulsifying approach, offering an alternative method to load drugs at their therapeutic dosage. Physical stability concerns regarding the unconventional oily phase were addressed through stress tests using multiple and dynamic light scattering, demonstrating the robustness of the system. In addition, the formulated SEDDS proved effective in protecting CBD from the harsh acidic gastric environment for up to 2 h at pH 1.2. Furthermore, in vitro studies have confirmed the safety of the formulation and the ability of CBD to permeate Caco-2 cells when formulated. This investigation highlights the potential incorporation of THEDES in lipid-based formulations like SEDDS, expanding the avenues for innovative oral drug delivery approaches.

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.

Hydrophobic Deep Eutectic Solvents as Greener Substitutes for Conventional Extraction Media: Examples and Techniques

Deep eutectic solvents (DESs) are multicomponent designer solvents that exist as stable liquids over a wide range of temperatures. Over the last two decades, research has been dedicated to developing noncytotoxic, biodegradable, and biocompatible DESs to replace commercially available toxic organic solvents. However, most of the DESs formulated until now are hydrophilic and disintegrate via dissolution on coming in contact with the aqueous phase. To expand the repertoire of DESs as green solvents, hydrophobic DESs (HDESs) were prepared as an alternative. The hydrophobicity is a consequence of the constituents and can be modified according to the nature of the application. Due to their immiscibility, HDESs induce phase segregation in an aqueous solution and thus can be utilized as an extracting medium for a multitude of compounds. Here, we review literature reporting the usage of HDESs for the extraction of various organic compounds and metal ions from aqueous solutions and absorption of gases like CO₂. We also discuss the techniques currently employed in the extraction processes. We have delineated the limitations that might reduce the applicability of these solvents and also discussed examples of how DESs behave as reaction media. Our review presents the possibility of HDESs being used as substitutes for conventional organic solvents.

A new application of continuous sample drop flow microextraction using octanoic acid as a green extraction solvent for the determination of antibiotic drugs in urine samples

In this study, octanoic acid (OA) was used as an extraction solvent for the pre-concentration and determination of three antibiotic drugs (levofloxacin, metronidazole, and tinidazole) in urine samples. To extract the antibiotic drugs, a green solvent was used as the extraction solvent in the continuous sample drop flow microextraction method, followed by a high-performance liquid chromatography photodiode array detector. According to the findings, the present study offers an environmentally friendly analytical method with a high capacity for the microextraction of the antibiotic drugs at very low concentrations. The calculated detection limits were 6.0-10.0 µg/L and the linear range was found between 20 and 780 µg/L. The proposed method showed excellent repeatability with the RSD values ranging from 2.8 to 5.5%. The relative recoveries were between 79.0 and 92.0% in the urine samples with spiked levels of 40.0-100.0 µg/L for metronidazole and tinidazole, and 100.0-200.0 μg/L for levofloxacin.

Menthol and Fatty Acid-Based Hydrophobic Deep Eutectic Solvents as Media for Enzyme Activation

This research aims to provide insights into the biological efficacy of a newly formed hydrophobic deep eutectic solvent (DES). A DES based on menthol was successfully synthesized with fatty acids. The DESs’ properties as enzyme activators were examined against a neat counterpart. The menthol:decanoic acid (1:1) combination showed improved thermal stability, strong catalytic activity, and reusability for up to four subsequent cycles under ideal conditions (pH 7.0, 40 °C for 2 h). The hydrophobic DES replaced hexane in ester synthesis, where RNL@DES5 showed better fatty acid conversion compared to neat RNL. This study demonstrated promising applications of hydrophobic DESs in non-aqueous organic reactions.

Determination of quinolone antibiotics in honey by pH-induced natural deep eutectic solvent combined with vortex-assisted dispersive liquid-liquid microextraction

A green, fast, and efficient pH-induced natural deep eutectic solvent combined with vortex-assisted dispersive liquid-liquid microextraction method (pH-NADES-VA-DLLME) followed by HPLC was established for determination of ofloxacin (OFL), ciprofloxacin (CIP) and enrofloxacin (ENR) in honey. In this method, NaOH, as an emulsifier, can increase the contact area between the NADES and the sample solution, which can efficiently improve the extraction efficiency of the analytes. Moreover, HCl acts as the phase separation agent without centrifugation in the process, which can greatly enhance the efficiency of the sample analysis process. In addition, the main factors affecting the extraction effect were optimized by single factor experiments. Under the optimal conditions, the limits of detection (LODs), the limits of quantification (LOQs) and recoveries were in the range of 0.004-0.015 μg mL^-1, 0.012-0.050 μg mL^-1, and 98.0-112.5%, respectively. The RSD values of intra-day and inter-day precisions were no more than 5.5% and 6.0%, respectively. The developed method was successfully applied to determine the three quinolone antibiotics in honey.

Development and application of a membrane assisted solvent extraction-molecularly imprinted polymer based passive sampler for monitoring of selected pharmaceuticals in surface water

In this work, we demonstrate the development, evaluation and pre-liminary application of a novel passive sampler for monitoring of selected pharmaceuticals in environmental waters. The samplers were calibrated in laboratory-based experiments to obtain sampling rates (Rs) for carbamazepine, methocarbamol, etilefrine, venlafaxine and nevirapine. Passive sampling was based on the diffusion of the target pharmaceuticals from surface water through a membrane bag which housed an ionic liquid as a green receiving solvent and a molecularly imprinted polymer. Effects of biofouling, deployment time and solvent type for the receiver phase were optimized for selective uptake of analytes in surface water. Notably, there was a decrease in the uptake of selected pharmaceuticals and consequently a decrease in their sampling rates in the presence of biofouling. The optimum matrix-matched sampling rates ranged from 0.0007 - 0.0018 L d^-1 whilst the method detection and quantification limits ranged from 2.45 - 3.26 ng L^-1 and 8.06 - 10.81 ng L^-1, respectively. The optimized passive sampler was deployed in a dam situated in the heart of a typical highly populated township in the Gauteng Province of South Africa. Only etilefrine and methocarbamol were detected and quantified at maximum time weighted average concentrations of 12.88 and 72.29 ng L^-1, respectively.

Natural Deep Eutectic Solvent-Based Dispersive Liquid-Liquid Microextraction Coupled with Direct Analysis in Real Time Mass Spectrometry: A Green Temperature-Mediated Analytical Strategy

Green analytical chemistry (GAC) represents a rapidly growing research field that aims at developing novel analytical approaches with minimal consumption of hazardous reagents and solvents. The current study reports on a GAC methodology exploiting the unique physicochemical properties of natural deep eutectic solvents (NADESs), a supposedly environmentally friendly class of solvents. Based on a temperature-mediated strategy, the NADESs were manipulated to undergo multiple phase transitions for favorable functionality and performance. As proof-of-concept demonstrations, both hydrophobic and hydrophilic NADESs were prepared for the extraction and analysis of eight phthalate esters in aqueous samples (food simulants) and three aflatoxins in oily samples (edible oils), respectively. NADES-based dispersive liquid-liquid microextraction (DLLME) was employed to achieve high-efficiency sample pretreatment. Afterward, the NADESs were transformed from liquids into solids by tuning the peripheral temperature for a convenient phase separation from the sample matrices. The solidified NADES extracts were melted and vaporized at elevated temperatures by transmission-mode direct analysis in real time (DART) for further quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS) analysis. The developed protocol was validated, achieving good repeatability with relative standard deviations (RSDs) of less than 9% and satisfactory sensitivity with limits of detection (LODs) and quantitation (LOQs) ranging from 0.1 to 0.8 and 0.2 to 2.0 μg/kg, respectively. The greenness of the analytical methodology was assessed with the calculated scores of 0.66 and 0.57 for the hydrophobic and hydrophilic NADES-based protocols, respectively. The method was applied to marketed samples, highlighting the great potential for green chemical analysis.

Hydrophobic deep eutectic solvent-based ultrasonic-assisted liquid-liquid microextraction combined with GC for eugenol, isoeugenol, and methyl isoeugenol determination in aquatic products

The use of deep eutectic solvents (DESs) has great prospects because of the green and efficient characteristics, which can be used for developing analytical methods for foods. In this research, assisted by ultrasonic waves, a liquid-liquid microextraction detection method combined with gas chromatography was established for three anaesthetics (eugenol, isoeugenol, and methyl isoeugenol) in aquatic food. The processing conditions including the components, ratio of hydrogen bond acceptor and hydrogen bond donor, DES volume, ultrasonic time, and pH were evaluated and optimised to improve the extraction efficiency, which was based on the DES structures and properties. In-house method validation was carried out by applying to real samples. A Thymol: levulinic acid DES (with a molar ratio of 1:2) was used as the extractant and the recoveries were as high as 93-101% for eugenol, 90-100% for methyl isoeugenol, and 86-94% for isoeugenol with RSDs <5% under optimum conditions. The limit of detection and quantification of the eugenol compounds were 0.08-0.10 μg/mL and 0.26-0.33 μg/mL, respectively. The method has green credentials and comparable LOD to homologous apparatus, which can be used for the determination of eugenol components in aquatic food.

Functionalized monolithic columns: Recent advancements and their applications for high-efficiency separation and enrichment in food and medicine

The chromatographic column is the core of a high-performance liquid chromatography (HPLC) system, and must have excellent separation efficiency and selectivity. Therefore, functional modification materials for monolithic columns have been rapidly developed. This study is a systematic review of the recently reported functionalized monolithic columns. In particular, the study reviews the types of functional monomers under different modification conditions, as well as the separation and detection techniques combined with chromatography, and their development prospects. In addition, the applications of functionalized monolithic columns in food analysis, biomedicine, and the analysis of active ingredient of Chinese herbal medicines in recent years are also discussed. Also reviewed are the functionalized monolithic columns for qualitative and quantitative analysis. It provided a reference for further development and application of organic polymer monolithic columns.

pH-Responsive Regulation of a Surfactant-Free Microemulsion Based on Hydrophobic Deep Eutectic Solvents

Microemulsions containing a responsive hydrophobic deep eutectic solvent (HDES) as the oil phase that can replace conventional organic solvents are considered to be a green strategy. It is anticipated that a pH-responsive HDES is synthesized to prepare rapid responsive surfactant-free microemulsions (SFMEs), which enable the transition from SFMEs to nanoemulsions. Menthol and n-octanoic acid (OA) were assembled into HDES by hydrogen bonding at a molar ratio of 1:2. The pH-responsive HDES as the oil phase and isopropyl alcohol (IPA) as the double solvent could form HDES/IPA/water SFMEs, which have unique responsiveness. Specifically, from the nuclear magnetic resonance hydrogen spectrum, pH, thermogravimetry, and Fourier transform infrared spectroscopy investigations, the excellent switchability and stability of menthol-OA were demonstrated. On the basis of these complexes, microemulsions were successfully prepared. Electrical conductivity and pH measurements were used to determine the structures of microemulsions and the phase inversion process. The effects of the contents of water and HDES, NaCl concentration, and pH of the system were investigated. Nanoemulsions were successfully prepared on the basis of the pH response of the microemulsions. In addition, the prepared nanoemulsion has a unique pH-responsive behavior that can be controllably regulated among nanoemulsions, microemulsions, and phase separation systems.

Enhancing the electrochemical sensitivity of hydroquinone using a hydrophobic deep eutectic solvent-based carbon paste electrode

The present study reports the synthesis and characterization of hydrophobic deep eutectic solvents (HDES) based on fatty acids and tetrabutylammonium bromide (TBAB) or 1-octanol using Fourier transform infrared spectroscopy, and the analysis of the physicochemical properties (viscosity, density, electrical conductivity, and water content) of these solvents. A carbon paste electrode modified with 6.0% (m/m) decanoic acid and TBAB-based HDES was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The oxidation peak currents of the proposed electrode were enhanced by its high electrochemical activity, fast electron transfer rate, and high surface area, while a remarkable decrease was observed in the peak potential separation. The electrochemical determination of hydroquinone (H₂Q) was carried out using square-wave adsorptive anodic stripping voltammetry (SWAdASV). The electrode response was found to be linear in the H₂Q concentration range of 2.5 × 10^-6-3.0 × 10^-3 mol L^-1, with the limit of detection (LOD) of 7.7 × 10^-7 mol L^-1. The method was successfully applied for H₂Q determination in dermatological creams.

Lab-In-Syringe automation of deep eutectic solvent-based direct immersion single drop microextraction coupled online to high-performance liquid chromatography for the determination of fluoroquinolones

Lab-In-Syringe direct immersion single drop microextraction is proposed as an automated sample pretreatment methodology and coupled online to HPLC with fluorescence detection for the determination of fluoroquinolones in environmental waters. For the first time, a drop of a natural deep eutectic solvent (NADES), synthesized from hexanoic acid and thymol, has been used as an extractant in automated single-drop microextraction. The extraction procedure was carried out within the 5 mL void of an automatic syringe pump. A 9-position head valve served the aspiration of all required solutions, air, waste disposal, and hyphenation with the HPLC instrument. Sample mixing during extraction was done by a magnetic stirring bar placed inside the syringe. Only 60 μL of NADES were required omitting toxic classical solvents and improving the greenness of the proposed methodology. By direct injection, linear working ranges between 0.1 and 5 μg L^-1 were achieved for all fluoroquinolones. The limit of quantification values and enrichment factors ranged from 20 ng L^-1 to 30 ng L^-1 and 35 to 45, respectively. Accuracies obtained from the analysis of spiked surface water and wastewater treatment plant effluent analysis at two concentration levels (0.5 and 4 μg L^-1) ranged from 84.6% to 119.7%, with RSD values typically <3%.

A review of green solvent extraction techniques and their use in antibiotic residue analysis

Antibiotic residues are being continuously recognized in the aquatic environment and in food. Though the concentration of antibiotic residues is typically low, adverse effects on the environment and human health have been observed. Hence, an efficient method to determine numerous antibiotic residues should be simple, inexpensive, selective, with high throughput and with low detection limits. Liquid-based extractions have been exceedingly used for clean-up and preconcentration of antibiotics prior to chromatographic analysis. In order to make methods more green and environmentally sustainable, conventional hazardous organic solvents can be replaced with green solvents. This review presents sampling strategies as well as comprehensive and up-to-date methods for chemical analysis of antibiotic residues in different sample matrices. Particularly, solvent-based sample preparation techniques using green solvents are discussed along with applications in antibiotic residue analysis.

Interfacial Properties of Hydrophobic Deep Eutectic Solvents with Water

Hydrophobic deep eutectic solvents (DESs) have recently gained much attention as water-immiscible solvents for a wide range of applications. However, very few studies exist in which the hydrophobicity of these DESs is quantified. In this work, the interfacial properties of hydrophobic DESs with water were computed at various temperatures using molecular dynamics simulations. The considered DESs were tetrabutylammonium chloride–decanoic acid (TBAC–dec) with a molar ratio of 1:2, thymol–decanoic acid (Thy–dec) with a molar ratio of 1:2, and dl-menthol–decanoic acid (Men–dec) with a molar ratio of 2:1. The following properties were investigated in detail: interfacial tensions, water-in-DES solubilities (and salt-in-water solubilities for TBAC–dec/water), density profiles, and the number densities of hydrogen bonds. Different ionic charge scaling factors were used for TBAC–dec. Thy–dec and Men–dec showed a high level of hydrophobicity with negligible computed water-in-DES solubilities. For charge scaling factors of 0.7 and 1 for the thymol and decanoic acid components of Thy–dec, the computed interfacial tensions of the DESs are in the following order: TBAC–dec (ca. 4 mN m^–1) < Thy–dec (20 mN m^–1) < Men–dec (26 mN m^–1). The two sets of charge scaling factors for Thy–dec did not lead to different density profiles but resulted in considerable differences in the DES/water interfacial tensions due to different numbers of decanoic acid–water hydrogen bonds at the interfaces. Large peaks were observed for the density profiles of (the hydroxyl oxygen of) decanoic acid at the interfaces of all DES/water mixtures, indicating a preferential alignment of the oxygen atoms of decanoic acid toward the aqueous phase.

Vortex-assisted natural deep eutectic solvent dispersive liquid-liquid microextraction based on the solidification of a floating organic drop for the determination of benzoic acid and sorbic acid in condiments

A simple, inexpensive, reliable and environmentally friendly method based on vortex-assisted dispersive liquid-liquid microextraction combined with solidification of a floating organic drop (VA-DLLME-SFO) followed by high performance liquid chromatography with a diode array detector (HPLC-DAD) was developed to determine benzoic acid (BA) and sorbic acid (SA) in ketchup and powder bags of instant noodles. Hydrophobic natural deep eutectic solvents (NADESs), as the microextraction solvent, were prepared with ternary components. Acetic acid can reduce the viscosity of hydrophobic NADESs and vortex can promote the dispersion of NADESs in aqueous solvents. In the DLLME process, several key parameters were optimized, including the type and volume of hydrophobic NADES, pH value, vortex time and salt content. Meanwhile, these parameters were assessed using response surface methodology based on the Box-Behnken design (BBD). Under optimal conditions, the developed method showed good linearity in the selected range (r², 0.9997). The limits of detection were 0.2 μg mL^-1 and 0.07 μg mL^-1 for BA and SA, respectively. Recoveries were in the range of 82.21% to 102.70% and the relative standard deviations (intra-day and inter-day precisions) were less than 5.66%. The proposed method was successful in analyzing BA and SA in ketchup and powder bags of instant noodles.

Determination of benzotriazole and benzothiazole derivatives in human urine by eco-friendly deep eutectic solvent-based ultrasound-assisted liquid-liquid microextraction followed by ultrahigh performance liquid chromatography quadrupole-time-of-flight mass spectrometry

Benzotriazole (BTRs) and benzothiazole (BTHs) derivatives have been classified as high production volume pollutants of emerging concern. The present work describes a rapid and simple process using an eco-friendly deep eutectic solvent (DES) based-ultrasound-assisted liquid-liquid microextraction (DES-UALLME) technique to effectively extract five BTRs and four BTHs in human urine samples, and then applying ultrahigh-performance liquid chromatography and electrospray ionization (+)-quadrupole time-of-flight mass spectrometry (UHPLC-ESI(+)-QTOF-MS) for their detection and quantification. DESs are a group of novel "green" solvents, and their applications in sample pretreatment are appropriate for the requirements for green chemistry, environmental protection and sustainable development. Furthermore, to overcome the challenges related to different experimental conditions, multivariate experimental design approaches conducted by means of a multilevel categorical design and a Box-Behnken Design were applied to screen and optimize parameters that have significant influences on the extraction efficiency of DES-UALLME. After optimization, the method was validated and shown to possess low limits of quantitation (LOQs; 0.4 - 9 ng mL^-1), high precision (3-12%), and high accuracy (mean spiked recoveries; 80-101%). The developed method was then successfully applied for the analysis of BTRs and BTHs in human urine samples. Interestingly, 5,6-dimethyl-1H-benzotriazole (XTR) was detected in almost all of the urine samples, which correlates with its high production and widely applications in industry processes and consumer products in Taiwan. These target analytes could potentially be used as biomarkers to assess exposure of BTRs and BTHs in biomonitoring programs and studies.

Phase separation property of a hydrophobic deep eutectic solvent-water binary mixture: A molecular dynamics simulation study

Over the past decade, deep eutectic solvents (DESs) have earned applicability in numerous fields as non-flammable, non-volatile, and greener alternatives to conventional organic solvents. In a first of its kind, a hydrophobic DES composed of a 1:1 mixture of oleic acid and lidocaine was recently reported, possessing a lower critical solution temperature in water. The thermoreversible phase property of this DES-water system was utilized to sequester out dye molecules from their aqueous solutions. In this article, we explore the phase separation phenomena for this particular DES in its aqueous solution using an all-atom molecular dynamics simulation. A 50 wt. % solution of the DES in water was studied at three different temperatures (253, 293, and 313 K) to understand the various molecular interactions that dictate the phase segregation property of these systems. In this work, we have elaborated on the importance of hydrogen bonding interactions and the non-bonding interactions between the components and the competition between the two that leads to phase separation. Overall, we observe that the increase in unfavorable interaction between the DES components and water with increasing temperature determines the phase separation behavior. We have also studied the modification in the dynamical properties of water molecules close to the phase boundary. Such molecular insights would be beneficial for designing novel solvent systems that can be used as extraction-based media in industries.

Thermodynamic, transport, and structural properties of hydrophobic deep eutectic solvents composed of tetraalkylammonium chloride and decanoic acid

With the emergence of hydrophobic deep eutectic solvents (DESs), the scope of applications of DESs has been expanded to include situations in which miscibility with water is undesirable. Whereas most studies have focused on the applications of hydrophobic DESs from a practical standpoint, few theoretical works exist that investigate the structural and thermodynamic properties at the nanoscale. In this study, Molecular Dynamics (MD) simulations have been performed to model DESs composed of tetraalkylammonium chloride hydrogen bond acceptor and decanoic acid hydrogen bond donor (HBD) at a molar ratio of 1:2, with three different cation chain lengths (4, 7, and 8). After fine-tuning force field parameters, densities, viscosities, self-diffusivities, and ionic conductivities of the DESs were computed over a wide temperature range. The liquid structure was examined using radial distribution functions (RDFs) and hydrogen bond analysis. The MD simulations reproduced the experimental density and viscosity data from the literature reasonably well and were used to predict diffusivities and ionic conductivities, for which experimental data are scarce or unavailable. It was found that although an increase in the cation chain length considerably affected the density and transport properties of the DESs (i.e., yielding smaller densities and slower dynamics), no significant influence was observed on the RDFs and the hydrogen bonds. The self-diffusivities showed the following order for the mobility of the various components: HBD > anion > cation. Strong hydrogen bonds between the hydroxyl and carbonyl groups of decanoic acid and between the hydroxyl group of decanoic acid and chloride were observed to dominate the intermolecular interactions.

Vortex assisted liquid-liquid microextraction based on in situ formation of a natural deep eutectic solvent by microwave irradiation for the determination of beta-blockers in water samples

In this study, a simple, green, and reliable method combining vortex-assisted liquid-liquid microextraction based on in situ formation of a novel hydrophobic natural deep eutectic solvent (NADES-VA-LLME) and high-performance liquid chromatography (HPLC) was developed for the determination of metoprolol and propranolol in water samples. The novel NADES was synthesized in situ within only 20 s by subjecting the water sample containing azelaic acid and thymol to microwave irradiation at 50 ˚C. Initial studies indicated that a 17:1 ratio of thymol to azelaic acid yielded the highest response for analytes. The influence of 7 parameters, including NADES volume, salt amount, sample pH, vortex time, centrifugation time, microwave time, and temperature, were screened using a 2^7-3 fractional factorial design. The obtained significant parameters were optimized by response surface methodology employing a Box-Behnken design. The method displayed satisfactory linearity (r=0.9996) for metoprolol and propranolol with limits of detection of 0.2 and 0.1 µg/L, respectively. The relative standard deviation at 2.5, 40, and 80 µg/L levels was lower than 6%, with accuracy in the range of 90.8-100.2%. Enrichment factors were 147.0 and 144.4 for metoprolol and propranolol, respectively. This study demonstrates that the developed in situ NADES-VA-LLME-HPLC technique can be considered as a fast and environmentally friendly alternative for isolation/preconcentration of β-blockers from water samples.

The study and application of biomolecules in deep eutectic solvents

Deep eutectic solvents offer stimulating possibilities for biomolecular stabilization and manipulation, biocatalysis, bioextraction, biomass processing, and drug delivery and therapy.

Hydrophobic deep eutectic solvent-based ultrasonic-assisted liquid-liquid micro-extraction combined with HPLC-FLD for diphenylamine determination in fruit

In this paper, novel high extraction efficiency hydrophobic eutectic solvents (DESs), n-octanoic acid as a hydrogen bond donor (HBD) and menthol as a hydrogen bond acceptor (HBA), were selected from five hydrophobic DESs to extract trace diphenylamine (DPA) in fruits apple, pear and orange under ultrasonic-assisted liquid-liquid micro-extraction (UA-LLME) technology before high-performance liquid chromatography (HPLC) analysis. Working parameters such as the DESs type, molar ratio, extractant volume, and ultrasonic time of the LLME hydrophobic DESs technology were optimised. Average recoveries between 96% and 108% were obtained on actual samples. This method gave lower detection limit (LOD) than other existing methods due to combining the high-efficiency extraction of hydrophobic DES and high sensitivity of fluorescence detector. This method was sensitive and eco-friendly, and can be used for the determination of trace components in fruits.

A rapid and simple method for the removal of dyes and organophosphorus pesticides from water and soil samples using deep eutectic solvent embedded sponge

A new treatment method using a deep eutectic solvent embedded melamine sponge (DES-MS) was studied for the removal of organic pollutants from water and soil samples. Five organophosphorus pesticides (OPPs) consisting of azinphos-methyl (AZP), parathion-methyl (PRT), fenitrothion (FNT), diazinon (DIZ) and chlorpyrifos (CPF), and two dyes including acid blue 29 (AB29) and malachite green (MG) were used as the model pollutants. DESs were easily prepared from tetrabutylammonium bromide (TBABr) and various fatty acids. The synthesised DESs were loaded into the sponge before being utilized for the removal of the studied pollutants. After the removal, the residual OPPs or dyes in the supernatant was quantified by high performance liquid chromatography or derivative spectrophotometry, respectively. The proposed method was simple, rapid, environmentally friendly and effective with the removal efficiency higher than 70% for various samples. Moreover, the removal of various dyes was successfully achieved with the efficiency greater than 65% under the optimum condition.

A Review of the Use of Eutectic Solvents, Terpenes and Terpenoids in Liquid–liquid Extraction Processes

Diverse and abundant applications of the eutectic solvents have appeared in the last years. Their promising tunable properties, eco-friendly character and the possibility of being prepared from numerous compounds have led to the publication of numerous papers addressing their use in different areas. Terpenes and terpenoids have been employed in the formulation of eutectic solvents, though they also have been applied as solvents in extraction processes. For their hydrophobic nature, renewable character, low environmental impact, cost and being non-hazardous, they have also been proposed as possible substitutes of conventional solvents in the separation of organic compounds from aqueous streams, similarly to hydrophobic eutectic solvents. The present work reviews the application of eutectic solvents in liquid–liquid extraction and terpenes and terpenoids in extraction processes. It has been made a research in the current state-of-the-art in these fields, describing the proposed applications of the solvents. It has been highlighted the scale-up feasibility, solvent regeneration and reuse procedures and the comparison of the performance of eutectic solvents, terpenes and terpenoids in extraction with conventional organic solvents or ionic liquids. Ultimately, it has been also discussed the employ of predictive methods in extraction, the reliability of thermodynamic models in correlation of liquid–liquid equilibria and simulation of liquid–liquid extraction processes.

Processing of Functional Composite Resins Using Deep Eutectic Solvent

Deep eutectic solvents (DESs)—a promising class of alternatives to conventional ionic liquids (ILs) that have freezing points lower than the individual components—are typically formed from two or more components through hydrogen bond interactions. Due to the remarkable advantages of biocompatibility, economical feasibility and environmental hospitality, DESs show great potentials for green production and manufacturing. In terms of the processing of functional composite resins, DESs have been applied for property modifications, recyclability enhancement and functionality endowment. In this review, the applications of DESs in the processing of multiple functional composite resins such as epoxy, phenolic, acrylic, polyester and imprinted resins, are covered. Functional composite resins processed with DESs have attracted much attention of researchers in both academic and industrial communities. The tailored properties of DESs for the design of functional composite resins—as well as the effects of hydrogen bond on the current polymeric systems—are highlighted. In addition to the review of current works, the future perspectives of applying DESs in the processing of functional composite resins are also presented.