Application of ionic liquids based enzyme-assisted extraction of chlorogenic acid from Eucommia ulmoides leaves

A new approach for ionic liquid based enzyme-assisted extraction (ILEAE) of chlorogenic acid (CGA) from Eucommia ulmoides is presented in which enzyme pretreatment was used in ionic liquids aqueous media to enhance extraction yield. For this purpose, the solubility of CGA and the activity of cellulase were investigated in eight 1-alkyl-3-methylimidazolium ionic liquids. Cellulase in 0.5 M [C6mim]Br aqueous solution was found to provide better performance in extraction. The factors of ILEAE procedures including extraction time, extraction phase pH, extraction temperatures and enzyme concentrations were investigated. Moreover, the novel developed approach offered advantages in term of yield and efficiency compared with other conventional extraction techniques. Scanning electronic microscopy of plant samples indicated that cellulase treated cell wall in ionic liquid solution was subjected to extract, which led to more efficient extraction by reducing mass transfer barrier. The proposed ILEAE method would develope a continuous process for enzyme-assisted extraction including enzyme incubation and solvent extraction process. In this research, we propose a novel view for enzyme-assisted extraction of plant active component, besides concentrating on enzyme facilitated cell wall degradation, focusing on improvement of bad permeability of ionic liquids solutions.     

Methanolysis of poly(lactic acid) (PLA) catalyzed by ionic liquids

Poly(lactic acid) (PLA) was depolymerized by methanol in the presence of a novel catalyst: ionic liquids. It was found that the purification method of the main products in the methanolysis catalyzed by ionic liquids was simpler than that of traditional compounds, such as sulfuric acid. Qualitative analysis indicated that the main product in the methanolysis process was methyl lactate. The influences of experimental parameters, such as the amount of ionic liquids, methanolysis time, reaction temperature, and dosages of methanol on the conversion of PLA, yield of methyl lactate were investigated. Under the optimum conditions, using ionic liquid 1-butyl-3-methylimidazolium acetate ([Bmim][Ac]) as catalyst, results showed that the ionic liquid could be reused up to 6 times without apparent decrease in the conversion of PLA and yield of methyl lactate. The kinetics of the reaction was also investigated. The results indicated that the methanolysis of PLA was a first-order kinetic reaction with activation energy of 38.29 kJ/mol. In addition, a possible catalysis mechanism of the methanolysis of PLA was proposed.     

离子液体萃取阿魏酸和咖啡酸的性能研究

以1-甲基-3-丁基咪唑六氟磷酸盐([C4mim][PF6])和1-甲基-3-己基咪唑六氟磷酸盐([C6mim][PF6])离子液体为萃取剂,采用紫外分光光度法研究了溶液pH值、温度、相比率及盐的种类和浓度对其萃取阿魏酸和咖啡酸效率的影响,考察了被萃取物的回收及离子液体的循环使用,探讨了两种离子液体替代传统有机溶剂阿魏酸和咖啡酸的可能性。实验结果表明:萃取温度和无机盐的种类及浓度对FA和CA萃取效率的影响较小;水相pH值对萃取效率有较大的影响,萃取FA适宜pH应小于3.67,萃取CA适宜pH应小于3.71;被萃取物浓度增大,萃取效率降低,而相体积比增大其萃取效率升高;两种离子液体对FA和CA的萃取效率[C4mim][PF6]大于[C6mim][PF6],同种离子液体对FA的萃取效率大于CA;在萃取相中的FA和CA可定量回收,且被萃取物中离子液体的残留[C6mim][PF6]小于[C4mim][PF6],离子液体可循环使用。     

Ionic liquids based simultaneous ultrasonic and microwave assisted extraction of phenolic compounds from burdock leaves

The ionic liquids based simultaneous ultrasonic and microwave assisted extraction (IL-UMAE) technique was first proposed and applied to isolate compounds. The ionic liquids comprising a range of four anions, five 1-alkyl-3-methylimidazolium derivatives were designed and prepared. The results suggested that varying the anion and cation both had apparent effects on the extraction of phenolics. The results also showed that irradiation power, time and solid–liquid ratio significantly affected the yields. The yields of caffeic acid and quercetin obtained by IL-UMAE were higher than those by regular UMAE. Compared with conventional heat-reflux extraction (HRE), the proposed approach exhibited higher efficiency (8–17% enhanced) and shorter extraction time (from 5 h to 30 s). The results indicated ILUMAE to be a fast and efficient extraction technique. Moreover, the proposed method was validated by the reproducibility and recovery experiments. The ILUMAE method provided good recoveries (from 96.1% to 105.3%) with RSD lower than 5.2%, which indicated that the proposed method was credible. Based on the designable nature of ionic liquids, and the rapid and highly efficient performance of the proposed approach, ILUMAE provided a new alternative for preparation of various useful substances from solid samples.     

Rapid analysis of Fructus forsythiae essential oil by ionic liquids-assisted microwave distillation coupled with headspace single-drop microextraction followed by gas chromatography–mass spectrometry

A rapid, green and effective miniaturized sample preparation and analytical technique, i.e. ionic liquids-assisted microwave distillation coupled with headspace single-drop microextraction (ILAMD-HS-SDME) followed by gas chromatography–mass spectrometry (GC–MS) was developed for the analysis of essential oil (EO) in Fructus forsythiae. In this work, ionic liquids (ILs) were not only used as the absorption medium of microwave irradiation but also as the destruction agent of plant cell walls. 1-Ethyl-3-methylimidazolium acetate ([C₂mim]OAc) was chosen as the optimal ILs. Moreover, n-heptadecane (2.0 μL) was selected as the appropriate suspended solvent for the extraction and concentration of EO. Extraction conditions of the proposed method were optimized using the relative peak area of EO constituents as the index, and the optimal operational parameters were obtained as follows: irradiation power (300 W), sample mass (0.7 g), mass ratio of ILs to sample (2.4), temperature (78 °C) and time (3.4 min). In comparison to previous reports, the proposed method was faster and required smaller sample amount but could equally monitor all EO constituents with no significant differences.     

Effect of anionic structure on the phase formation and hydrophobicity of amino acid ionic liquids aqueous two-phase systems

Compared with the conventional ionic liquids, amino acid ionic liquids are more biodegradable and biocompatible, and can enhance stability of biomaterials. In this work, amino acid ionic liquids 1-butyl-3-methylimidazolium L-serine ([C(4)mim][Ser]), 1-butyl-3-methylimidazolium glycine ([C(4)mim][Gly]), 1-butyl-3-methylimidazolium L-alanine ([C(4)mim][Ala]) and 1-butyl-3-methylimidazolium L-leucine ([C(4)mim][Leu]) have been synthesized. These ionic liquids are found to form aqueous two-phase systems (ATPSs) by the salted-out of K(3)PO(4) in aqueous solutions. Phase diagram of the ATPSs and the Gibbs energies of transfer of methylene group from the bottom salt-rich phase to the top ionic liquid-rich phase have been determined at 298.15K and pH 14, and the effect of anionic structure of the ionic liquids on phase formation of the ATPSs and the relative hydrophobicity between the top and the bottom phases are then examined. In order to understand the effect of relative hydrophobicity of the phases in equilibrium in the ATPSs on the extraction/separation capability of biomolecules, the partition coefficients of cytochrome-c (as a model biomolecule) in the ATPSs are measured by spectrophotometry. It is suggested that hydrophobic interactions are mainly responsible for the higher partition coefficients of cytochrome-c in aqueous two-phase systems at pH 14, and the extraction and separation capacity of biomolecules can be improved by the modulation of the relative hydrophobicity of the phases and/or the pH of the system.     

离子液体-加速溶剂萃取-高效液相色谱法测定蜜饯中的有机酸类防腐剂

以离子液体氯化1-辛基-3-甲基咪唑盐([Omim]Cl)的水溶液为萃取剂,采用加速溶剂萃取结合高效液相色谱法测定了蜜饯中苯甲酸、山梨酸、肉桂酸等有机酸类防腐剂,优化了加速溶剂萃取实验参数,最佳萃取条件为:离子液体浓度为0.1mol/L,萃取时间为5min,萃取温度为80℃。在最佳条件下,有机酸类防腐剂的检出限为0.4～27.7μg/L。将本方法用于蜜饯样品的检测,回收率为78.2%～113.9%。实验结果表明:离子液体-加速溶剂萃取法快速、高效。     

Ionic liquids based microwave-assisted extraction of lichen compounds with quantitative spectrophotodensitometry analysis

Ionic liquids based extraction method has been applied to the effective extraction of norstictic acid, a common depsidone isolated from Pertusaria pseudocorallina, a crustose lichen. Five 1-alkyl-3-methylimidazolium ionic liquids (ILs) differing in composition of alkyl chain and anion were investigated for extraction efficiency. The extraction amount of norstictic acid was determined after recovery on HPTLC with a spectrophotodensitometer. The proposed approaches (IL-MAE and IL-heat extraction (IL-HE)) have been evaluated in comparison with usual solvents such as tetrahydrofuran in heat-reflux extraction and microwave-assisted extraction (MAE). The results indicated that both the characteristics of the alkyl chain and anion influenced the extraction of polyphenolic compounds. The sulfate-based ILs [C(1)mim][MSO(4)] and [C(2)mim][ESO(4)] presented the best extraction efficiency of norstictic acid. The reduction of the extraction times between HE and MAE (2 h-5 min) and a non-negligible ratio of norstictic acid in total extract (28%) supports the suitability of the proposed method. This approach was successfully applied to obtain additional compounds from other crustose lichens (Pertusaria amara and Ochrolechia parella).     

Quantitative High Performance Liquid Chromatography Determination of Alkanolamines in Ionic Liquid Absorbents

The development of modern absorption media suitable for CO₂ scrubbing, such as ionic liquids and their mixtures, requires appropriate analytical protocols. In this paper, the application of high-performance liquid chromatography to the determination of alkanolamine at various concentrations in ionic liquid solutions was investigated. Both hydrophilic and hydrophobic commercial ionic liquids, such as 1-butyl-3-methylimidazolium acetate [bmim][OAc], 1-ethyl-3-methylimidazolium octylsulfate [emim][OcSO₄], and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [bmim][NTf₂], were studied in this paper and different sample preparation procedures were used for each class of solvent. A simple extraction step was necessary prior to HPLC analysis for hydrophobic ionic liquids. This step was performed using five times more 0.05 M KH₂PO₄ than needed for the ionic liquid sample. Hydrophilic ionic liquid solutions could be analyzed after diluting the sample with water. The general procedure involved separation at room temperature using a cation-exchange HPLC with 0.05 M KH₂PO₄ as the mobile phase and refractometric detection without derivatizing the amines. The influence of the temperature and mobile phase composition on alkanolamine retention was investigated. The relationship between the peak area and alkanolamine concentration was linear over 3 orders of magnitude (2–200 nmol). The detection limit (LOD) for monoethanolamine (MEA) and diethanolamine (DEA) was 1.5 and 2 nmol, respectively. For hydrophobic ionic liquids, which require extraction, it was possible to analyze a 0.004% MEA solution. The quantity of the sample required for analysis was 0.1 g, and the analysis time did not exceed 20 minutes.     

Combined Application of Ionic Liquid and Hybrid Poly (Ionic Liquid)-Bonded Silica: An Alternative Method for Extraction,Separation and Determination of Flavonoids from Plants

Hybrid poly (ionic liquid)-bonded silica was combined with an ionic liquid solution for the extraction, separation, and determination of flavonoids from natural plants by using a multi-phase dispersive extraction (MPDE) method. The hybrid material was synthesized using a facile method. A suitable sorbent was identified based on the adsorption behaviors of flavonoids on different poly (ionic liquid)-bonded silicas. In contrast to traditional matrix solid-phase dispersion (MSPD) method, the target analytes were first extracted by three-phase (sample-solvent-sorbent) dispersive extraction with ionic liquid (1-oxyl-3-methylimidazolium bromide) solutions as the solvent, and then cleaned up after removal from the sample matrix, called MPDE. This process combines the advantages of ionic liquids, ionic liquid-based sorbent, and MPDE. The recovery rates were achieved by MPDE of the flavonoids from Chamaecyparis obtusa: 76.4% for myricetin and 90.3% for amentoflavone. The proposed method may be used to extract and separate other flavonoids or even polyphenolic compounds from complex samples.     

Catalytic degradation of lignin model compounds in acidic imidazolium based ionic liquids: Hammett acidity and anion effects

Ionic liquids based on the 1-methylimidazolium cation with chloride, bromide, hydrogen sulfate, and tetrafluoroborate counterions along with 1-butyl-3-methylimidazolium hydrogen sulfate were employed to degrade two lignin model compounds, guaiacylglycerol-β-guaiacyl ether and veratrylglycerol-β-guaiacyl ether. The acidity of each ionic liquid was approximated using 3-nitroaniline as an indicator to measure the Hammett acidity (H₀). While all of the tested ionic liquids were strongly acidic (H₀ between 1.48 and 2.08), the relative acidity did not correlate with the ability of the ionic liquid to catalyze β-O-4 ether bond hydrolysis. The reactivity of the model compounds in the ionic liquids is dependent not only on the acidity, but also on the nature of the ions and their interaction with the model compounds.     

Application of ionic liquids based microwave-assisted extraction of three alkaloids N-nornuciferine, O-nornuciferine, and nuciferine from lotus leaf

The application of ionic liquids based microwave-assisted extraction (ILMAE) was successfully developed for extracting three alkaloids N-nornuciferine, O-nornuciferine, and nuciferine from lotus leaf. Seven kinds of 1-alkyl-3-methylimidazolium with different cations and anions were investigated in this work and 1.0 M 1-hexyl-3-methylimidazolium bromide ([C₆MIM]Br) solution was selected as solvent. In addition, the microwave parameters including irradiation power, extraction time and solid-liquid ratio were optimized. Compared with the regular MAE and conventional heat-reflux extraction (HRE), the proposed approach exhibited higher efficiency (0.9-43.7% enhanced) and shorter extraction time (from 2 h to 2 min), which indicated ILMAE was an efficient, rapid and simple sample preparation technique. Moreover, the proposed method was validated by the linearity, reproducibility, and recovery experiments. Good linearity was observed with the regression coefficients (r²) between 0.9998 and 0.9999. The recoveries of all methods were in the range of 94.6% and 105.5% with RSD lower than 6.6%, which indicated that the proposed method was credible.     

果糖在酸性离子液体中脱水制备5-羟甲基糠醛

制备了多种离子液体,并将其作为催化剂和溶剂催化果糖脱水制备5-羟甲基糠醛（HMF）。 制备的酸性离子液体包括磺酸基功能化酸性离子液体、咪唑类酸性离子液体和吡啶类酸性离子液体。 利用核磁共振仪和红外光谱仪对离子液体的结构进行表征。 利用紫外可见光分光光度计结合Hammett指示剂计算Hammett酸度函数,比较了酸强度的大小对反应的影响。 结果表明,离子液体的酸强度对反应有较大影响,在无其它催化剂和溶剂的情况下,离子液体具有较高的催化活性,通过使用1-丁基-3-甲基咪唑氯盐(BmimCl)作为催化剂,当反应温度为120 ℃,反应进行到4 h时,HMF收率可以达到74.97%。     

Fluorous ionic liquids as solvents for the liquid-liquid extraction of metal ions by macrocyclic polyethers

The predominant mode of strontium ion transfer from aqueous nitrate media into a series of 1-fluoroalkyl-3-methylimidazolium bis[(trifluoromethylsulfonyl)]imides containing dicyclohexano-18-crown-6 (DCH18C6) is shown to shift from cation exchange to strontium nitrato-crown ether complex partitioning as the length of the fluoroalkyl substituent is increased. Fluoroalkyl substituents are shown to be only slightly more effective than their non-fluorous analogs at inducing this shift. At the same time, the fluorinated ionic liquids (ILs) yield strontium distribution ratios as much as an order of magnitude lower than the corresponding 1-alkyl-3-methylimidazolium (C_nmim⁺) salts. Fluorous ILs thus appear to offer no compelling advantages over C_nmim⁺ ionic liquids as extraction solvents.     

Phase Behavior of Ionic Liquids-Cesium Carbonate-Water Aqueous Two-phase Systems and Their Extraction of L-Tryptophan

Phase behavior and extraction ability of aqueous two-phase systems(ATPs) consisting of ionic liquids(ILs), Cs₂CO₃ and water were investigated in this paper. Four kinds of ionic liquids, namely, 1-amyl-3-methylimidazolium bromide([C₅mim]Br), 1-hexyl-3-methylimidazolium bromide([C₆mim]Br), 1-heptyl-3-methylimidazolium bromide ([C₇mim]Br) and 1-octyl-3-methylimidazolium bromide([C₈mim]Br), were examined to discuss the influence of alkyl groups. Binodal curves and tie-lines at 288.15, 298.15 and 308.15 K were obtained. The partitioning behavior for L-tryptophan in such ATPs was further investigated. The effect of temperature, pH, Cs₂CO₃ concentration and the structure of ionic liquids on the partitioning were discussed in detail.     

Electrospray ionization mass spectrometry of ionic liquids and determination of their solubility in water

Electrospray ionization mass spectrometry is used to detect both the cations (C⁺) and the anions (A^–) of ionic liquids (CA). In this study, the ionic liquids are diluted with aqueous methanol before injection. In addition to the main peaks of the parent ions, fragmentation products are observed upon increasing the cone voltage, whereas aggregates of the parent ion with one or more ionic liquid molecules (e.g., C(CA)_n⁺, A(CA)_n^–) are observed upon decreasing the cone voltage. The ions of several ionic liquids in a mixture are also detected and the ratios of their concentrations estimated. A method is developed to determine quantitatively the concentration of an ionic liquid in solution by using the cation and anion of another ionic liquid as internal standards. By using this method, the solubilities in water at room temperature (22±1 °C) of three typical hydrophobic ionic liquids have been determined: 0.70±0.08 g L^–1 for methyltributylammonium bis(trifluoromethylsulfonyl)imide (MeBu₃NNTf₂), 6.0±0.5 g L^–1 for butylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BuMePyrNTf₂), and 18.6±0.7 g L^–1 for 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF₆).     

Ionic Liquid-Based Dispersive Extraction and Separation of Phenolic Acids from Salicornia Herbacea L.

This study reports the application of a dispersive extraction method for the extraction and separation of phenolic acids from Salicornia Herbacea L. using silica-confined ionic liquids as the sorbent. A suitable sorbent for phenolic acid extraction and separation was first identified based on the adsorption behavior of phenolic acids on different silica-confined ionic liquids. The sample was then mixed with the optimized sorbent and solvent to achieve dispersive extraction. After transferring the supernatant to an empty cartridge, a solid phase extraction process was used to separate the three organic acids from other interferences. Through systematical optimization, the optimal conditions were obtained with high recovery rates of protocatechuic acid (98.1%), caffeic acid (89.4%), and ferulic acid (92.2%). Overall, the proposed method expected to have wide applicability.     

Ionic liquid-based microwave-assisted extraction of rutin from Chinese medicinal plants

An ionic liquid-based microwave-assisted extraction (ILMAE) method has been developed for the effective extraction of rutin from Chinese medicinal plants including Saururus chinensis (Lour.) Bail. (S. chinensis) and Flos Sophorae. A series of 1-butyl-3-methylimidazolium ionic liquids with different anions were investigated. The results indicated that the characteristics of anions have remarkable effects on the extraction efficiency of rutin and among the investigated ionic liquids, 1-butyl-3-methylimidazolium bromide ([bmim]Br) aqueous solution was the best. In addition, the ILMAE procedures for the two kinds of medicinal herbs were also optimized by means of a series of single factor experiments and an L₉ (3⁴) orthogonal design. Compared with the optimal ionic liquid-based heating extraction (ILHE), marinated extraction (ILME), ultrasonic-assisted extraction (ILUAE), the optimized approach of ILMAE gained higher extraction efficiency which is 4.879 mg/g in S. chinensis with RSD 1.33% and 171.82 mg/g in Flos Sophorae with RSD 1.47% within the shortest extraction time. Reversed phase high performance liquid chromatography (RP-HPLC) with ultraviolet detection was employed for the analysis of rutin in Chinese medicinal plants. Under the optimum conditions, the average recoveries of rutin from S. chinensis and Flos Sophorae were 101.23% and 99.62% with RSD lower than 3%, respectively. The developed approach is linear at concentrations from 42 to 252 mg L⁻¹ of rutin solution, with the regression coefficient (r) at 0.99917. Moreover, the extraction mechanism of ILMAE and the microstructures and chemical structures of the two researched samples before and after extraction were also investigated. With the help of LC-MS, it was future demonstrated that the two researched herbs do contain active ingredient of rutin and ionic liquids would not influence the structure of rutin.     

Solid-phase extraction of room-temperature imidazolium ionic liquids from aqueous environmental samples

Owing to their favorable properties, ionic liquids have recently gained recognition as possibly environmentally benign solvents. Now among the most promising industrial chemicals, they have already been labeled green, but this appellation seems due entirely to their very low vapor pressure. This growing interest in the various applications of ionic liquids will soon result in their presence in the environment. Therefore, reliable analytical tools for the environmental analysis of ionic liquids need to be developed urgently. This paper presents a newly developed analytical procedure for the enrichment of 1-alkyl- and 1-aryl-3-methylimidazolium ionic liquids from water samples. The method is based on cation exchange solid-phase extraction followed by selective elution. Pre-concentrated samples are subjected to high-performance liquid chromatography (HPLC) with an advanced methodology for qualitative and quantitative analysis. The overall procedure was verified by using standard spiked samples of tap water, seawater, and freshwater.     

Extraction of Lithium from Salt Lake Brine with Triisobutyl Phosphate in Ionic Liquid and Kerosene

Three ionic liquids(ILs), namely, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-me- thylimidazolium bis[(trifluoromethyl)sulfonyl]imide and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sul- fonyl]imide with the triisobutyl phosphate(TIBP) and kerosene system were respectively used to extract lithium ion from salt lake brine with a high concentration ratio of magnesium and lithium experimentally. Results indicate that the highest extraction selectivity for lithium was obtained with IL 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)- sulfonyl]imide. The effects of solution pH and phase ratio R(O/A) on the extractive step and the influence of acid concentration of the stripping solution and R(O/A) on the back extraction step were also investigated systematically. The single-step extraction efficiency of lithium ion was 83.71% under the optimal extraction conditions, and the single-step back extraction efficiency was 85.61% with a 1.0 mol/L HCl in 1.0 mol/L NaCl medium as stripping agent at R(O/A)=2. The liquid-liquid extraction mechanism and the complex of the ligand with lithium were proposed.