Hydrophobic deep eutectic solvent as a green extractant for high‐performance liquid chromatographic determination of tetracyclines in water samples

A green extractant, hydrophobic deep eutectic solvent was first introduced for extraction of tetracycline, oxytetracycline, and chlortetracycline from environmental water samples prior to high‐performance liquid chromatography determination. Deep eutectic solvents consist of methyltrioctylammonium chloride and various medium‐chain alcohols/acids, and are easy in preparation, low cost and toxicity, desirably biodegradable, and biocompatible. The overall time required for sample preparation was 6 min and the volume of organic solvent used for extraction was only 400 µL. Under the optimized extraction condition, the present method yielded low limit of detection (0.5–2.0 ng/mL), acceptable precision (relative standard deviations < 9.7%), good linearity from 2.0 to 500 ng/mL (r² ≥ 0.9991). This optimized procedure was applied for determination of tetracyclines in different water samples with desirable spiked recovery ranged from 77.5 to 87.6%. There is, therefore, a great potential to further expand application of the method for investigation of other ultra‐trace analyte(s) in environmental matrixes.     

低共熔液相微萃取-高效液相色谱法测定食用油中双酚AEI北大核心CSCD

建立了一种基于低共熔溶剂(DESs)的液液微萃取-高效液相色谱联用(LLME-HPLC)技术用于测定食用油中的双酚A(BPA)的方法,对比了3种DES和甲醇、乙二醇对食用油中BPA的萃取效率,研究了温度、萃取时间和萃取剂体积对萃取效率的影响。结果表明:氯化胆碱/乙二醇组成的DES萃取率最高;低共熔溶剂用量100μL,萃取温度25℃,萃取时间5 min时,萃取效率最高。BPA的检测限和定量限分别为0.10 mg/L和0.50 mg/L,加标回收率在86.3%~109.9%范围内,RSD小于6%。方法可用于食用油中BPA的检测。     

Ternary deep eutectic solvent magnetic molecularly imprinted polymers for the dispersive magnetic solid‐phase microextraction of green tea

Ternary deep eutectic solvent magnetic molecularly imprinted polymers grafted on silica were developed for the selective recognition and separation of theophylline, theobromine, (+)‐catechin hydrate, and caffeic acid from green tea through dispersive magnetic solid‐phase microextraction. A new ternary deep eutectic solvent was adopted as a functional monomer. The materials obtained were characterized by FTIR spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, NMR spectroscopy, and powder X‐ray diffraction. The practical recovery of the theophylline, theobromine, (+)‐catechin hydrate, and caffeic acid isolated with ternary deep eutectic solvent magnetic molecularly imprinted polymers in green tea were 91.82, 92.13, 89.96, and 90.73%, respectively, and the actual amounts extracted were 5.82, 4.32, 18.36, and 3.69 mg/g, respectively. The new method involving the novel material coupled with dispersive magnetic solid‐phase microextraction showed outstanding recognition, selectivity and excellent magnetism, providing a new perspective for the separation of bioactive compounds.     

Green and enhanced extraction of coumarins from Cortex Fraxini by ultrasound‐assisted deep eutectic solvent extraction

Green and enhanced extraction of bioactive ingredients from medicinal plants has become a hot research field, and deep eutectic solvents have been considered as a novel kind of sustainable solvents in the extraction process. In this study, hydrogen bond acceptor (choline chloride, etc.) and hydrogen bond donor (l ‐malic acid, etc.) were used to prepare different kinds of deep eutectic solvents to extract coumarins from Cortex Fraxini. The extraction conditions, including the composition and moisture content of deep eutectic solvents, extraction time, and liquid‐solid ratio, were systematically optimized basing on the extraction yield of coumarins. To further investigate the extraction mechanism, Fourier transform infrared spectroscopy was performed, and the microstructures of Cortex Fraxini powders were observed before and after extraction using scanning electron microscope. Results showed that the novel ultrasound‐assisted extraction with conditions of deep eutectic solvent containing betaine/glycerin (1:3), aqueous solution (20%), solid‐liquid ratio (15 mg/mL), and extraction time (30 min) exhibited the best extraction yields for the four target coumarins and much better extraction efficiency than with conventional solvent extractions. This suggests that the new ultrasound‐assisted deep eutectic solvent extraction could be used as a green and high‐efficient approach for extraction of the main coumarins from Cortex Fraxini.     

A novel vortex-assisted liquid phase microextraction method for parabens in cosmetic oil products using deep eutectic solvent

ABSTRACT

The parabens, which are harmful to our bodies, are primarily utilized as preservatives in medicine, personal care products and cosmetics. A novel, more efficient, fast and cheap vortex-assisted liquid phase microextraction method based on deep eutectic solvents (DESs) was developed for the determination of parabens. The microextraction conditions were optimized using these solvents and the analytical parameters of the method were determined under optimal microextraction conditions. After extraction, the chromatographic separation of parabens was undertaken using high-performance liquid chromatography-UV detection. Experimental parameters, such as DES type, DES volume, dilution solvent volume and vortex extraction time were optimized. DES6 [ChCl-Ethylene glycol (1/2)] was the most suitable DES to work in this study. Detection limits for this method of 0.053 µg mL^?1 for methylparaben, 0.061 µg mL^?1 for ethylparaben, 0.049 µg mL^?1 for propylparaben and 0.052 µg mL^?1 for butylparaben were obtained. Correlation coefficients (R²) for a concentration range of 0.1–100 µg mL^?1 were higher than 0.9992 and relative standard deviation (RSD) values below 2.91% at parabens concentration of 2.5 µg mL^?1 were obtained. The results of spike/recovery values of real samples were greater than 84%. When compared with other methods, the main advantages include lower LOD, short extraction time, rapidity, repeatability and simplicity.     

Use of green alternative solvents in dispersive liquid-liquid microextraction: A review

Dispersive liquid-liquid microextraction is one of the most widely used microextraction techniques currently in the analytical chemistry field, mainly due to its simplicity and rapidity. The operational mode of this approach has been constantly changing since its introduction, adapting to new trends and applications. Most of these changes are related to the nature of the solvent employed for the microextraction. From the classical halogenated solvents (e.g., chloroform or dichloromethane), different alternatives have been proposed in order to obtain safer and non-pollutants microextraction applications. In this sense, low-density solvents, such as alkanols, switchable hydrophobicity solvents, and ionic liquids were the first and most popular replacements for halogenated solvents, which provided similar or better results than these classical dispersive liquid-liquid microextraction solvents. However, despite the good performances obtained with low-density solvents and ionic liquids, researchers have continued investigating in order to obtain even greener solvents for dispersive liquid-liquid microextraction. For that reason, in this review, the evolution over the last five years of the three types of solvents already mentioned and two of the most promising solvent alternatives (i.e., deep eutectic solvents and supramolecular solvents), have been studied in detail with the purpose of discussing which one provides the greenest alternative.     

Pipette‐tip solid‐phase extraction based on deep eutectic solvent modified graphene for the determination of sulfamerazine in river water

A green and novel deep eutectic solvent modified graphene was prepared and used as a neutral adsorbent for the rapid determination of sulfamerazine in a river water sample by pipette‐tip solid‐phase extraction. Compared with conventional graphene, deep eutectic solvent modified graphene can change the surface of graphene with wrinkled structure and higher selective extraction ability. The properties of deep eutectic solvent modified graphene and graphene were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Static adsorption showed deep eutectic solvent modified graphene had a higher adsorption ability (18.62 mg/g) than graphene. Under the optimum conditions, factors such as kinds of washing solvents and elution solvents and volume of elution solvent were evaluated. The limits of detection and quantification were 0.01 and 0.03 μg/mL, respectively. The method recoveries of sulfamerazine were in the range of 91.01–96.82% with associated intraday relative standard deviations ranging from 1.63 to 3.46% and interday relative standard deviations ranging from 0.68 to 3.84%. Deep eutectic solvent modified graphene showed satisfactory results (recovery was 95.38%) and potential for rapid purification of sulfamerazine in river water sample in combination with the pipette‐tip solid‐phase extraction method.     

Aqueous two‐phase systems based on deep eutectic solvents and their application in green separation processes

As a new environmentally friendly separation technology, deep eutectic solvent based aqueous two‐phase systems are extensively applied in various fields. Herein, we review recent advances in this field and highlight the possible directions of future developments. This article focuses on the effects of deep eutectic solvent and inorganic salts on the phase equilibrium, the microstructure of deep eutectic solvent based aqueous two‐phase systems, the applications of deep eutectic solvent based aqueous two‐phase systems in separation (proteins, biopolymers, saponins, and organic acids), and removal and recovery technologies for deep eutectic solvent from aqueous two‐phase systems.     

Effervescence-assisted dispersive liquid-liquid microextraction based on deep eutectic solvent for preconcentration and FAAS determination of copper in aqueous samples

A new effervescence-assisted dispersive liquid-liquid microextraction, EA-DLLME, technique was developed for preconcentration and flame atomic absorption spectrometric determination of copper in aqueous samples. Effervescence assistance and DES combination for metal ion extraction was used for the first time. In the presented study, six different effervescence powders were examined to achieve maximum extraction efficiency. In addition, 1,5 diphenyl carbazide was used as complexing agent and DES prepared by mixing choline chloride and phenol was used as extraction solvent. The effect of several parameters such as pH, concentration of complexing agent, composition and volume of DES, amount of THF, composition and amount of effervescent agent were examined. Performed experiments showed that optimum pH was 6.0, the best effervesce powder composition was NaH₂PO₄:Na₂CO₃ with 2 × 10^?3:1 × 10^?3 molar ratio and the amount of effervesce powder was 0.4 g. Under optimum conditions enhancement factor, limit of detection and limit of quantification were calculated as 78, 2.9 and 9.7 μg L^?1, respectively. In addition, to prove precision of the method intra-day relative standard deviations were calculated for 10 and 50 μg L^?1 Cu²⁺ concentrations and found as 2.1% and 1.3%, respectively. The proposed method showed good linearity within the range of 10.0–100 μg L^?1. Finally, proposed method was successfully applied to determination of copper traces in aqueous samples.     

Vortex‐assisted natural deep eutectic solvent microextraction using response surface methodology optimization for determination of orthophosphate in water samples by molybdenum blue method

A new, rapid, and efficient microextraction technique named vortex‐assisted natural deep eutectic solvent microextraction has been developed for the preconcentration and determination of orthophosphate in real water samples. The method is based on the formation of the phosphomolybdenium blue complex followed by proposed microextraction procedure and subsequent spectrophotometric determination in a microcell. Screening study for the optimal composition of natural deep eutectic solvent was initially performed with different solvents, including choline chloride as hydrogen bond acceptor and different hydrogen bond donors. A ternary mixture of glucose‐choline chloride‐water was used as the most efficient extraction solvent. Response surface methodology based on the central composite design was used to optimize experimental parameters. Under optimal conditions, the calibration graph for orthophosphate determination was linear over the range of 2.0–80.0 µg/L (correlation coefficient of 0.9971) with a detection limit of 0.2 µg/L. The repeatability, reproducibility, and relative error values of the method were below 7%, indicating acceptable precision and accuracy. This approach, using natural deep eutectic solvent as an eco‐friendly solvent with high solubilization power and vortex mixing as an alternative energy source, represents a promising choice for a green separation and preconcentration methodology for determination of orthophosphate in real water samples.     

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

Deep eutectic solvents are considered as new and green solvents that can be widely used in analytical chemistry such as microextraction. In the present work, a new dl‐ menthol‐based hydrophobic deep eutectic solvent was synthesized and used as extraction solvents in an air‐assisted dispersive liquid–liquid microextraction method for preconcentration and extraction of benzophenone‐type UV filters from aqueous samples followed by high‐performance liquid chromatography with diode array detection. In an experiment, the deep eutectic solvent formed by dl‐ menthol and decanoic acid was added to an aqueous solution containing the UV filters, and then the mixture was sucked up and injected five times by using a glass syringe, and a cloudy state was achieved. After extraction, the solution was centrifuged and the upper phase was subjected to high‐performance liquid chromatography for analysis. Various parameters such as the type and volume of the deep eutectic solvent, number of pulling, and pushing cycles, solution pH and salt concentration were investigated and optimized. Under the optimum conditions, the developed method exhibited low limits of detection and limits of quantitation, good linearity, and precision. Finally, the proposed method was successfully applied to determine the benzophenone‐type filters in environmental water samples with relative recoveries of 88.8–105.9%.     

Three‐phase hollow‐fiber liquid‐phase microextraction based on deep eutectic solvent as acceptor phase for extraction and preconcentration of main active compounds in a traditional Chinese medicinal formula

A three‐phase hollow‐fiber liquid‐phase microextraction based on deep eutectic solvent as acceptor phase was developed and coupled with high‐performance capillary electrophoresis for the simultaneous extraction, enrichment, and determination of main active compounds (hesperidin, honokiol, shikonin, magnolol, emodin, and β,β′‐dimethylacrylshikonin) in a traditional Chinese medicinal formula. In this procedure, two hollow fibers, impregnated with n‐heptanol/n‐nonanol (7:3, v/v) mixture in wall pores as the extraction phase and a combination (9:1, v/v) of methyltrioctylammonium chloride/glycerol (1:3, n/n) and methanol in lumen as the acceptor phase, were immersed in the aqueous sample phase. The target analytes in the sample solution were first extracted through the organic phase, and further back‐extracted to the acceptor phase during the stirring process. Important extraction parameters such as types and composition of extraction solvent and deep eutectic solvent, sample phase pH, stirring rate, and extraction time were investigated and optimized. Under the optimal conditions, detection limits were 0.3–0.8 ng/mL with enrichment factors of 6–114 for the analytes and linearities of 0.001–13 μg/mL (r² ≥ 0.9901). The developed method was successfully applied to the simultaneous extraction and concentration of the main active compounds in a formula of Zi‐Cao‐Cheng‐Qi decoction with the major advantages of convenience, effectiveness, and environmentally friendliness.     

Synthesis and characterization of novel ternary deep eutectic solvents简

A series of room-temperature ternary deep eutectic solvents(TDESs) were prepared from imidazolium halides, zinc halides and amides. The [BMIM]Cl–ZnCl2 –acetamide(1:1:1) system shows the lowest freezing point( 60 8C) and lowest density in the series. The viscosity and conductivity of TDESs have an exponential relationship with temperature and can be fitted by Arrhenius equation.     

Advances of responsive deep eutectic solvents and application in extraction and separation of bioactive compounds

In recent years, it has been found that changing ambient conditions (CO₂/N₂, temperature, pH) can trigger a switchable phase transition of deep eutectic solvents, and such solvents are known as responsive deep eutectic solvents. In this work, we present the development history, properties, and preparation of responsive deep eutectic solvents, followed by the application of responsive deep eutectic solvents in the extraction and separation of bioactive compounds are presented. Importantly, the mechanism of responsive deep eutectic solvents in the extraction of bioactive compounds is discussed. Finally, the challenges and prospects of responsive deep eutectic solvents in the extraction and separation of bioactive compounds are proposed. Responsive deep eutectic solvents are considered green and efficient solvents. Some methods for extraction and separation of bioactive compounds by responsive deep eutectic solvents can increase the possibility of recycling the deep eutectic solvents, and provide higher efficiency in the extraction and separation field. It is hoped that this will provide a reference for the green and sustainable extraction and separation of various bioactive compounds.     

In‐process prepared deep eutectic solvent based homogeneous liquid–liquid microextraction for the determination of irgaphos 168 and irganox 1010 in polypropylene packed drinks

In situ synthesis of a deep eutectic solvent and homogeneous liquid–liquid microextraction performed in a narrow bore tube was developed for efficient extraction of irgaphos 168 and irganox 1010 in doogh and water samples packed in polypropylene packages. First, pH of the aqueous sample solutions containing the analytes is adjusted at 9. Then a hydrogen bond acceptor (choline chloride) and a hydrogen bond donor (oleic acid) are dissolved in the solution and vortexed to obtain a homogeneous solution. The solution is filled into a narrow bore tube, in which its bottom was clogged by a septum. Then hydrochloric acid solution is injected into the solution by a syringe. The tube is placed in an ultrasonic bath. During this step, the droplets of choline chloride:oleic acid deep eutectic solvent are produced. The method indicated high enrichment factor (435 for irgaphos 168 and 488 for irganox 1010), low limits of detection (0.03 and 0.09 ng/mL for irgaphos 168 and irganox 1010, respectively) and quantification (0.13 and 0.29 ng/mL for irgaphos 168 and irganox 1010), good recovery (74 and 83% for irgaphos 168 and irganox 1010, respectively), and satisfactory repeatabilities (relative standard deviations ≤12%) can be obtained using the developed method.     

A simple and efficient sample preparation for taxanes in Taxus chinensis needles with natural menthol‐based aqueous deep eutectic solvent

Taxanes are natural anticancer constituents, and the sample preparation from matrix normally depends on organochlorine solvents. In this study, green and natural menthol‐based aqueous deep eutectic solvent was synthesized and used for sample preparation for taxanes. Five key parameters were optimized and the optimal preparation conditions were as follows: menthol/1‐propanol ratio 1:1 (mol/mol), solid–liquid ratio 1:30 g/mL, extraction time 30 min, ultrasonic power 250 W, and water content 80%. Under the above conditions, the total extraction efficiency of seven main taxanes was 1.25‐ to 1.44‐fold to the conventional methods. In addition, a high‐performance liquid chromatography method with C₁₈ column was established for quantitation of seven main taxanes in <25 min, which had excellent linearity (R² > 0.9986), precision (relative standard deviation < 3.00%), repeatability (relative standard deviation < 3.69%), and recovery (90.26–109.00%). This method performed the extraction, and enrichment processes simultaneously, and it had advantages such as high extraction efficiency, simple operation, low cost, and eco‐friendliness. This work indicated that the natural menthol‐based deep eutectic solvent aqueous could be an excellent alternative to the sample preparation from Taxus or other plants.     

Dispersive liquid–liquid microextraction based on the solidification of deep eutectic solvent for the determination of benzoylureas in environmental water samples

We present a novel dispersive liquid–liquid microextraction method based on the solidification of deep eutectic solvent coupled with high‐performance liquid chromatography with a variable‐wavelength detection for the detection of five benzoylureas in real water samples. In this work, a green solvent consisting of 1‐octyl‐3‐methylimidazolium chloride and 1‐dodecanol was used as an extraction solvent, yielding the advantages of material stability, low density, and a suitable freezing point near room temperature. Parameters that significantly affect extraction efficiency were optimized by the one‐factor‐at‐a‐time approach. Under optimal conditions, the recoveries of five target compounds were obtained ranging from 87.39 to 98.05% with correlation coefficients ranging from 0.9994 to 0.9997 for pure water. The limits of detection were in the range of 0.09–0.16 μg/L. The enrichment factors were in the range of 171–188. Linearities were achieved in the range of 0.5–500 μg/L. The proposed method was successfully applied to determine benzoylureas in environmental water samples with a satisfactory recovery of approximately 81.38–97.67%.     

EMIES/p-TsOH型低共熔溶剂的合成及其氧化脱硫性能的研究

通过1-乙基-3-甲基咪唑硫酸乙酯离子液体（EMIES）和对甲苯磺酸（p-TsOH）的混合物制备EMIES/p-TsOH型低共熔溶剂。其结构特征通过红外光谱、氢谱和热重技术进行了分析。并以EMIES/p-TsOH作为催化剂与萃取剂,H₂O₂作为氧化剂研究了其对模拟油中的硫化物的脱除性能。考察了反应温度、n（H₂O₂）/n（S）比、低共熔溶剂加入量及硫化物类型对脱硫效果的影响。在最佳的条件下,模拟油中二苯并噻吩（DBT）、4,6-二甲基二苯并噻吩（4,6-DMDBT）和苯并噻吩（BT）的脱除率分别为96.2%、92.2%和88.8%。经过五次循环使用后,DBT的脱除率仍达到93.6%。对该脱硫体系进行了动力学分析,其表观活化能为66.4kJ/mol。     

Evaluation of green and efficient deep eutectic solvents as media for extracting alkaloids from lotus leaf

Deep eutectic solvents (DESs) were applied as eco-friendly solvents in this study for the extraction of alkaloids from lotus leaf, including O-nornuciferine, N-nornuciferine, nuciferine and roemerine. A series of hydrophilic and hydrophobic DESs with different hydrogen bond donors and a acceptors were synthesized and screened for a suitable DESs for extraction of alkaloids from lotus leaf. The study results showed that the hydrophilic DES with choline chloride and propanediol had the highest extraction yield. The main factors affecting the extraction efficiency—choline chloride–propanediol ratio, water content in deep eutectic solvents, solid–liquid ratio and extraction time—were investigated via a single-factor experiment. The optimized extraction conditions were 30% of water in choline chloride–propanediol (1:4) for heated extraction for 30 min and solid–liquid ratio 1:100 g/ml. Under optimum conditions, the extraction yields of O-nornuciferine, N-nornuciferine, nuciferine and roemerine were 0.069, 0.152, 0.334 and 0.041 g/100 g respectively, which were higher than those of methanol in acidified aqueous solution. This study suggests considerable potential for DESs as promising materials for the green and efficient extraction solvents for bioactive alkaloids from natural sources.