Low Transition Temperature Mixtures Research Articles

Dispersive liquid-liquid microextraction, an effective tool for the determination of synthetic cannabinoids in oral fluid by liquid chromatography–tandem mass spectrometry

In the present work, dispersive liquid-liquid microextraction (DLLME) was used to extract six synthetic cannabinoids (JWH-018, JWH-019, JWH-073, JWH-200, or WIN 55,225, JWH-250, and AM-694) from oral fluids. A rapid baseline separation of the analytes was achieved on a bidentate octadecyl silica hydride phase (Cogent Bidentate C18; 4.6 mm × 250 mm, 4 μm) maintained at 37 °C, by eluting in isocratic conditions (water:acetonitrile (25:75, V/V)). Detection was performed using positive electrospray ionization–tandem mass spectrometry. The parameters affecting DLLME (pH and ionic strength of the aqueous phase, type and volume of the extractant and dispersive solvent, vortex and centrifugation time) were optimized for maximizing yields. In particular, using 0.5 mL of oral fluid, acetonitrile (1 mL), was identified as the best option, both as a solvent to precipitate proteins and as a dispersing solvent in the DLLME procedure. To select an extraction solvent, a low transition temperature mixture (LTTM; composed of sesamol and chlorine chloride with a molar ratio of 1:3) and dichloromethane were compared; the latter (100 μL) was proved to be a better extractant, with recoveries ranging from 73% to 101 % by vortexing for 2 min. The method was validated according to the guidelines of Food and Drug Administration bioanalytical methods: intra-day and inter-day precisions ranged between 4 % and 18 % depending on the spike level and analyte; limits of detection spanned from 2 to 18 ng/mL; matrix-matched calibration curves were characterized by determination coefficients greater than 0.9914. Finally, the extraction procedure was compared with previous methods and with innovative techniques, presenting superior reliability, rapidity, simplicity, inexpensiveness, and efficiency.

Experiment and simulation for CO2 capture using low transition temperature mixtures as solvents

CO2 capture and storage technology, which is used to control the rate of global warming, is the most promising and feasible solution to reduce the concentration of CO2 in the atmosphere. In this work, experiment and simulation of CO2 capture process using low transition temperature mixtures (LTTMs) as solvents are studied. First, LTTMs were synthesized by using levulinic acid as hydrogen bond donor (HBD) and tetraethylammonium chloride as hydrogen bond acceptor (HBA). The solubility of CO2 in LTTMs was measured and effects of the mole ratio of HBD to HBA on solubility were also examined. It demonstrated that the solubility of CO2 in LTTMs increased with the increasing pressure or the decreasing temperature. Henry’s constants and thermodynamic properties such as Gibbs energy, enthalpy and entropy of dissolution were deduced by correlating the solubility data. Second, in order to explain the absorption mechanism, σ-profiles were adopted to study the molecular interactions between HBD/HBA/LTTMs and CO2. The analysis for geometry, interaction energy, independent gradient model and atoms in molecules were performed to explain the interaction mechanisms between CO2 and HBD/HBA/LTTMs. Moreover, CO2 capture process with LTTMs as solvents was simulated using Aspen Plus software. The design variables of CO2 capture process were optimized using multi-objective generic algorithm, and the optimal operating parameters were obtained. At last, the dynamic controllability of CO2 capture process was studied and an effective control structure was proposed, which worked quite well for the disturbances in both feed flow rate and feed composition.

Monosaccharides Dehydration Assisted by Formation of Borate Esters of α-Hydroxyacids in Choline Chloride-Based Low Melting Mixtures.

The synthesis of 5-hydroxymethylfurfural (5-HMF) and 2-furfural (2-F) by hexoses and pentoses dehydration is considered as a promising path to produce materials from renewable resources. Low-transition-temperature mixtures (LTTMs) enable selective (>80%) dehydration of ketoses to furanic derivatives at moderate temperature (<100°C). However, aldoses dehydration generally requires higher temperatures and an isomerization catalyst. Chromium trichloride has been reported as one of the most efficient catalyst but its kinetic inertness could limit its performances below 100°C. Consequently, we investigate herein boric acid catalysis of aldoses dehydration in LTTMs based on choline halides and organic acids at 90°C. The limited activity of boric acid regarding furanic compounds synthesis (e.g., 5% 5-HMF yield and 23% glucose conversion after 1 h at 90°C with maleic acid) can be enhanced through tetrahydroxyborate esters (THBE) formation with α-hydroxyacids (e.g., 19% 5-HMF yield and 61% glucose conversion after 1 h at 90°C). THBE formation is however associated with H3O+ generation favoring the appearance of side products (humins). We demonstrate that boric acid catalysis is not straightforward and that the use of THBE under moderate acidity should be further investigated to limit humins formation and promote furanic derivatives synthesis.

Mild and efficient prepare disperse yellow 184, disperse yellow 232 and their analogues via LTTM promoted three-component reaction

A convenient protocol for the synthesis of disperse yellow 184, disperse yellow 232 and their analogues via a three-component one-pot reaction of salicylaldehyde, o-aminophenol and ethyl cyanoacetate has been established. Cheap and eco-friendly ethanol was employed as solvent. One drop of low-transition-temperature mixture (LTTM) which formed from l(−)-Proline and oxalic acid could smoothly promote the reaction of 0.5 mmol raw materials. Compared to the classical methodologies, the present pathway has broad reaction scope and affords all products in good to excellent yields. Furthermore, this process could reduce the reaction temperature from 135 to 85 °C and avoid the problems associated with catalyst cost, handling, safety and pollution. On the basis of comparative experiments and DFT calculation, possible mechanism of this strategy is discussed in detail.

Synthesis and characterization of green menthol-based low transition temperature mixture with tunable thermophysical properties as hydrophobic low viscosity solvent

Abstract The liquid transition temperature mixture (LTTM) is a new type of tunable solvent analogous to deep eutectic solvent (DES). LTTMs have been favorable choice of researchers as they are green solvents, having potential to be an alternate to ionic liquids (ILs) and the traditional solvents, as they can be formulated from natural and biodegradable resources. The aim of this work is to design low viscosity, cheap, biodegradable and hydrophobic LTTMs from natural resources. In this study, LTTMs based on DL-menthol as hydrogen bond accepter (HBA) with naturally occurring hydrogen bond donor (HBD), namely thymol, sesamol, and 3-hydroxybenzoic acid were synthesized and characterized. The formation of LTTMs was monitored by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The functional group and purity of LTTMs were studied by Fourier transform infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR), respectively. Density, viscosity and water content of LTTMs were determined to analyse its solvent characteristics. Thermogravimetric analysis (TGA) was investigated to identify the thermal stability and working temperature range of LTTMs. The tuneability, the physicochemical properties of LTTMs at various temperature by changing the HBDs revealed that these LTTMs have the potential for a wide range of applications. Taking the advantage of their hydrophobic and low viscosity properties, these LTTMs have been applied as green extraction solvent in vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME) for the extraction of pyrethroid pesticides (bifenthrin, deltamethrin, fenpropathrin permethrin and tetramethrin) from aqueous solution.

An Expedient Four Component Synthesis of Substituted Pyrido-Pyrimidine Heterocycles in Glycerol:Proline Based Low Transition Temperature Mixture and Their Antioxidant Activity with Molecular Docking Studies

The present work describes an efficient and environmentally benign four component synthesis of structurally diverse substituted pyrido-pyrimidines involving the reaction of barbituric acid, 4-hydroxy 6-methyl 2-pyrone, an aromatic aldehyde and ammonium acetate in low transition temperature mixture (LTTM) (glycerol:proline: 1:1). The LTTM serves as green solvent which is an inexpensive, nontoxic and plays a dual function (reusable catalyst and solvent), and is found to be an excellent reaction endorsing medium. The present protocol offers some advantages such as easy work up, shorter reaction time, an excellent yield with higher atom economy, maximum reaction efficiency with an excellent green chemistry metrics. The synthesized compounds have been evaluated for their antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay as well as molecular docking studies performed on myeloperoxidase enzyme. Tested scaffolds exhibits an excellent results of virtual screening and antioxidant activity.

Kinetics and optimization of microwave-assisted lignin fractionation with Protic low transition temperature mixture of Sesamum indicum straw for enhanced bioethanol production

Six novel low transition temperature mixtures were synthesized as two groups of ternary protic (tpLTTM) and binary amphiphilic (aLTTM) mixtures. The thermophysical assessment of these LTTMs was evaluated as a function of temperature. Sustainable delignification for sesame straw and Hansen solubility using kraft lignin was determined as a function of relative energy difference (RED). CLG exhibited lowest RED (0.86) implying elevated lignin affinity (63.2%). Pretreatment kinetics and optimization for lignin removal was defined as a function of time. The samples were observed prior to and after treatment under SEM. The treated biomass (78.3%) was subjected to enzymatic digestion with immobilized cellulase (Cellic CTec2) and fermentation was accomplished with the same (68.3%) to produce bioethanol (81.3%).

Oxalic acid dihydrate: L-proline (LTTM) mediated synthesis of 2-substituted benzothiazole derivatives

Abstract An efficient, selective and green route for the synthesis of 2-substituted Benzothiazole derivatives (3a-i) developed by the reaction of 2-aminothiophenol (1) and various aromatic aldehydes (2a-i) using oxalic acid dihydrate: proline low transition temperature mixture (LTTM) as green reaction medium at room temperature. The attractive features of this protocol are simple reaction conditions, recyclability and reusability of the LTTM, good product yield and easy workup procedure. The method is operationally simple and ecofriendly.

Low Transition Temperature Mixtures (LTTM) Containing Sugars as Potato Starch Plasticizers

For the first time, low transition temperature mixtures – LTTM based on sugars: fructose (Fruc), glucose (Gluc) or sucrose (Suc), and glycerol (G) are prepared, characterized by DSC and applied as potato starch plasticizers. Sugar‐based LTTM exhibits good plasticizing activity leading to homogenous transparent, flexible thermoplastic starch (TPS) materials. Mechanical, dynamic mechanical (DMA), X‐ray diffractometry (XRD), and FTIR analysis of obtained TPS/LTTM films are performed for their relative comparison. For TPS/Fruc:G films, tensile strength (TS) and Young's modulus (YM) decreases and elongation at break (EB) increases with increase of G. However, for TPS/Gluc:G molar ratio of Gluc to G did not affect significantly on films mechanical properties. Comparing two monosugars, i.e., Gluc and Fruc, TPS/Gluc:G materials exhibit slightly higher TS (4.8–5.8 MPa) but lower EB (44–61%) in comparison with TPS/Fruc:G films (TS 3.2–5.0 MPa; EB 90–115%) at 25 °C, RH 50%. LTTM as whole mixture of components led to TPS products with not only higher TS, YM but even EB in comparison with films where sugars and G were added separately into starch. Mutual interaction between sugar, polyol and starch is confirmed by DMA. XRD reveals that starch with LTTM undergone amorphization and TPS/Suc:G 1:6 is the most amorphous among investigated TPS films.

Recovery of cellulose fibers from oil palm empty fruit bunch for pulp and paper using green delignification approach

The aim of this work was to recover the cellulose fibers from EFB using low-transition-temperature-mixtures (LTTMs) as a green delignification approach. The hydrogen bonding of LTTMs observed in 1H NMR tends to disrupt the three-dimensional structure of lignin and further remove the lignin from EFB. Delignification process of EFB strands and EFB powder were performed using standard l-malic acid and cactus malic acid-LTTMs. The recovered cactus malic acid-LTTMs showed higher glucose concentration of 8.07 mg/mL than the recovered l-malic acid LTTMs (4.15 mg/mL). This implies that cactus malic acid-LTTMs had higher delignification efficiency which led to higher amount of cellulose hydrolyzed into glucose. The cactus malic acid-LTTMs-delignified EFB was the most feasible fibers for making paper due to its lowest kappa number of 69.84. The LTTMs-delignified EFB has great potential to be used for making specialty papers in pulp and paper industry.

A low transition temperature mixture for the dispersive liquid-liquid microextraction of pesticides from surface waters

This paper illustrates the development of a procedure based on the use of a low transition temperature mixture (LTTM) for the dispersive liquid-liquid microextraction (DLLME) of fungicides, insecticides and acaricides from surface waters. The LTTM preparation involves the heat-mixing of choline chloride and acetylsalicylic acid in a molar ratio 1:2 (ChCl(ASA)2). The resulting mixture appears as a clear viscous liquid at room-temperature, denser than water (1.20 ± 0.01 g mL−1). For its characterization, differential scanning calorimetry (DSC) provided crucial evidence to classify it as a LTTM rather than as a deep eutectic solvent (DES) since it revealed an intense glass transition at −37 °C. Large-angle X-ray scattering (LAXS) confirmed the lack of any long-distance order. Due to the LTTM immiscibility with water, an evaluation study was carried out to test ChCl(ASA)2 as an effective alternative to the conventional chlorinated solvents for DLLME. To this end, 24 pesticides were used as model compounds, extracted from surface water samples (5 mL) and analyzed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The definitive procedure required the optimization of some key parameters such as volume of extracting solvent, type and volume of dispersing solvent, volume of the aqueous sample, LTTM dispersion procedure, and extraction time. Depending on pKa and logP values, recoveries ranged from 18 (for very polar compounds) to 96%, revealing that the ideal candidates for the extraction with ChCl(ASA)2 are neutral compounds with logP >2. After complete validation, the method was applied to analyze water samples from the River Tiber where dodine and dimetomorph were found at low μg L−1 concentration levels.

Study on the desulfurization performance of metal-based low transition temperature mixtures: Removal of hydrogen sulfide and sulfur recovery

Four metal-based low transition temperature mixtures (LTTMs) were synthesized in this work and used for the oxidation of hydrogen sulfide. The LTTMs were prepared from metal chlorides (ZnCl2, FeCl3·6H2O, CrCl3·6H2O and SnCl2·2H2O) and choline chloride (ChCl) with different mixing ratios. The synthesized LTTMs and desulfurization product were characterized using Fourier transform infrared (FT-IR) spectra, Raman spectroscopy, X-Ray Diffraction (XRD) and energy dispersive spectrum (EDS). The results showed that the Fe-based LTTM possesses the highest desulfurization ability. The LTTM of 4Fe/ChCl was identified as the best desulfurizer, and the effect of H2S concentration and temperature was investigated. It was found that a relatively low temperature was in favor of the oxidation of H2S. H2S could be removed excellently by LTTMs within H2S concentration of 1500–2300 mg/m3. The Fe-based LTTMs was proved to have good regeneration performance for at least 4 times. The desulfurization product was determined as sulfur with high purity and good crystal form, and could be recovered easily.

Optimization and control of CO2 capture using low transition temperature mixtures

In this work, low transition temperature mixture (LTTM) tetrabutylammonium chloride-lactic acid (TBA-LA 1:2) is selected as the solvent for CO2 absorption. Firstly, the binary interaction parameters of TBA-LA 1:2-CO2 are calculated by the regression of experimental data which are obtained from literature, and some other binary interaction parameters, such as the binary interaction parameters of TBA-LA 1:2-N2 and TBA-LA 1:2-H2O, are predicted by COSMO-SAC model. And then, the design variables of CO2 absorption process are optimized using multi-objective generic algorithm (MOGA). The results show that the absorptive capacity of TBA-LA 1:2 is similar to monoethanolamine (MEA), but lower than that of ionic liquid 1-decyl-3-methyl imidazolium trifluoromethanesulfonate ([C10mim][TfO]). At last, the dynamic controllability of CO2 capture process is studied and an effective control structure is proposed, which works pretty well for the disturbances in both feed rate and feed composition.

Liquid–Liquid Extraction of Benzene Using Low Transition Temperature Mixtures: COSMO-SAC Predictions and Experiments

To screen suitable low transition temperature mixtures (LTTMs) as solvents for the extraction process of a benzene and cyclohexane mixture, the extraction performance of the LTTMs (25 hydrogen-bond donors (HBDs) and 13 hydrogen-bond acceptors (HBAs)) was assessed based on COSMO-SAC predictions of infinite dilution activity coefficients of benzene and cyclohexane in different LTTMs. The effects of the molar ratio of HBD to HBA on extraction efficiency were also observed in the meantime. It is found that the LTTM sulfolane-tetrabutylammonium bromide 5:1 (ST 5:1), which has excellent extraction performance, is the most promising solvent. To explain the difference of extraction efficiency of various LTTMs, σ-profiles were adopted to study the molecular interactions between LTTMs and benzene or cyclohexane. The analysis for geometry, interaction energy, independent gradient model (IGM) and atoms in molecules (AIM) was performed to explain interaction mechanisms between benzene/cyclohexane and HBD/HBA. Moreover...

Production of 5-Hydroxymethylfurfural from D-Fructose in Low-Transition-Temperature Mixtures Enhanced by Chloride Anions and Low Amounts of Organic Acids.

The use of safe and sustainable solvents able to solvate reagents and to catalyze their reactions at temperatures below 100 °C is an innovative strategy to develop future lignocellulosic biorefineries. Many low-transition-temperature mixtures (LTTMs) have been investigated for this purpose. Among them, natural deep eutectic solvents (NADESs) have been proposed as cheap and renewable alternatives to ionic liquids for the synthesis of bio-based chemical building blocks. We compare herein the ability of several organic acids/choline chloride/water LTTMs to perform D-fructose dehydration to 5-hydroxymethylfurfural (5-HMF). The addition of chloride salts as well as an increased proportion of choline chloride promotes 5-HMF formation, which seems to indicate a beneficial effect of chloride anions on D-fructose dehydration. Besides improving selectivity by at least 10 %, increasing the choline chloride/acid ratio could enhance the biodegradability of the LTTMs. Unlike other acidic components, maleic and citric acids are especially selective at early D-fructose conversion. Maleic acid was the most selective acidic component among the tested chemicals, achieving an 80 % 5-HMF molar yield in 1 h at 90 °C.

Polyphenol extraction from Origanum dictamnus using low-transition temperature mixtures composed of glycerol and organic salts: Effect of organic anion carbon chain length

ABSTRACTNovel low-transition temperature mixtures (LTTMs), composed of glycerol and sodium acetate, sodium propionate, and sodium butyrate, were synthesized with the aim to investigate the organic anion chain length effect on the performance of polyphenol extraction from the medicinal plant Origanum dictamnus. The LTTMs used as hydrogen bond donor:hydrogen bond acceptor molar ratio of 6:1 and after establishing optimal conditions of water content and liquid-to-solid ratio by response surface methodology, kinetics was performed to identify the highest efficient system. The results drawn indicated that the longer the anion chain length, the higher the requirement for water content to achieve optimal total polyphenol yield. Extractions with LTTMs comprising of sodium propionate and sodium butyrate gave virtually equal yields in total polyphenols, yet extraction with the former solvent was significantly less energy-demanding, with the activation energy being 8.77 kJ mol−1. Liquid chromatography-diode array-mass spectrometry analyses revealed that the extract obtained with glycerol/sodium propionate at 70 °C also displayed a richer polyphenolic profile, while the antioxidant activity of the extract was not negatively affected up to this temperature. This novel green solvent is therefore proposed as a highly efficient means of recovering bioactive polyphenols from plant material.

Combining the preconcentration column and recovery column for the extractive distillation of ethanol dehydration with low transition temperature mixtures as entrainers

Extractive distillation using low transition temperature mixtures (LTTMs) is a promising technology to separate ethanol and water azeotrope. In this work, the separation of water and ethanol by extractive distillation using LTTMs (choline chloride/urea 1:2) as entrainer was designed and simulated in Aspen Plus. Firstly, database of ChCl/urea = 1:2 (Reline) was established in Aspen Plus. Secondly, the simulation and optimization of the conventional extractive distillation process for ethanol dehydration with Reline or ethylene glycol as entrainer were worked out. The results showed that the TAC (total annual cost) of the process with Reline as entrainer was reduce by 14.61% than that of the process with EG as entrainer. In addition, in order to reduce energy consumption in distillation, an energy-efficient extractive distillation process which combining the preconcentration section and entrainer recovery section in one column was developed. The results showed that the proposed process with Reline as entrainer could save 29.48% and 17.42% of TAC compared with the conventional extractive distillation with EG and Reline as entrainer, respectively.

Delignification kinetics of empty fruit bunch (EFB): a sustainable and green pretreatment approach using malic acid-based solvents

Recently, the development of efficient and environmentally benign solvents has received great attention to replace current harsh organic solvents. In this context, low-transition-temperature mixtures (LTTMs) have emerged as favorable green solvents for biomass delignification. Palm oil biomass, empty fruit bunch (EFB) was pretreated with commercial l-malic acid and microwave hydrothermally extracted cactus malic acid-derived LTTMs at 60, 80, and 100 °C. The LTTMs applied in this study were derived from malic acid–choline chloride–water and malic acid–monosodium glutamate–water with a molar ratio of 2:4:2 and 3:1:5, respectively. Three first-order reactions were used to express the delignification kinetic model of EFB. The first term was based on the initial stage and assigned as infinite due to the fast rate of delignification which could not be detected. The second and third terms were proportional to bulk and residual delignification stages. A good agreement was obtained between the kinetic model and the experimental data obtained in this study with R2 ≥ 0.91. The activation energies for the delignification reactions using l-malic acid and cactus malic acid-based LTTMs in the bulk and residual stages were approximated as 36–56 and 19–26 kJ/mol and 34–90 and 47–87 kJ/mol, respectively.

Life cycle assessment of oil palm empty fruit bunch delignification using natural malic acid-based low-transition-temperature mixtures: a gate-to-gate case study

In future biorefineries, the development of cheap and environmentally friendly solvents for biomass pretreatment is highly desirable. In this sense, low-transition-temperature mixtures (LTTMs) have high potential to serve as green solvents for replacing conventional pretreatment technologies. In this study, a life cycle assessment of LTTMs pretreatment was conducted to determine the environmental impacts caused by biomass delignification. A gate-to-gate analysis which started with harvested oil palm empty fruit bunch and ended with lignin was selected. The environmental impacts such as acidification potential, global warming potential, eutrophication potential, photochemical ozone creation potential, human toxicity potential and volatile organic compounds emission were evaluated. The comparable environmental balances of commercial l-malic acid and cactus malic acid-based LTTMs pretreatment processes verified the suitability of the process with natural malic acid as the source of proton donor. This study concludes that biomass delignification using natural cactus malic acid-based LTTMs had promising features such as high delignification efficiency and environmentally friendly compared to commercial l-malic acid-based LTTMs. Based on environmental point of view, the overall process of biomass delignification using sucrose-based LTTMs had lower CO2 emissions compared to the monosodium glutamate- and choline chloride-based LTTMs. These findings are important for verifying the greenness and sustainability of LTTMs to be applied at industrial scale.

Acetonitrile Dehydration via Extractive Distillation Using Low Transition Temperature Mixtures as Entrainers

Low transition temperature mixtures (LTTMs) are versatile alternatives to ILs. They share many properties with ILs, so they become a suitable choice for entrainers in extractive distillation processes. In this study, glycolic acid and choline chloride in a 3:1 molar ratio (GC3:1) were synthesized and explored as entrainers for separation of acetonitrile + water azeotropic mixtures. Isobaric vapor–liquid equilibrium data for the pseudobinary mixtures of ACN + GC3:1 and water + GC3:1 were measured at atmospheric pressure (101.32 kPa). For the pseudoternary system ACN + water + GC3:1, also VLE data were measured at different GC3:1 mole fractions of 0.05, 0.1, and 0.15. The thermodynamic modeling of these systems was performed using the nonrandom two-liquid (NRTL) model. Furthermore, a study was conducted for synthesized GC3:1 recoverability. A good agreement were found between experimental data and predicted values for these systems. Results showed that LTTM (GC3:1) eliminated the acetonitrile + water azeotr...