Extraction and high performance liquid chromatographic determination of 3-indole butyric acid in pea plants by using imidazolium-based ionic liquids as extractant

In this paper, imidazolium-based ionic liquids [C₄mim][PF₆], [C₆mim][PF₆], [C₈mim][PF₆], [C₆mim][BF₄] and [C₈mim][BF₄] were tested as extracting solvents for removal of 3-indole butyric acid (IBA) from aqueous media with subsequent determination using HPLC. Percent extraction of IBA was strongly affected by pH of aqueous phases and the chemical structures of ionic liquids (ILs). Extraction of IBA was quantitative in the pH values lower than pK_a of IBA. Considering both extraction and stripping efficiencies of IBA, [C₄mim][PF₆] was found to act more efficient than other studied ILs. Capacity of [C₄mim][PF₆] was 17.6 × 10⁻⁴ mmol IBA per 1.0 mL of IL. Ionic strength of aqueous phase and temperature had shown no serious effects on extraction efficiency of IBA. A preconcentration factor of 100 and a relative standard deviation of 1.16% were obtained. It was found that ionic liquid phase was reusable almost five times for extraction/stripping purposes. 3-Indole acetic acid showed interferential effect in the extraction step. In order to assess the applicability of the method, extraction and stripping of IBA from pea plants and some other samples were studied.     

X‐ray Photoelectron Spectroscopy of Pyridinium‐Based Ionic Liquids: Comparison to Imidazolium‐ and Pyrrolidinium‐Based Analogues

We investigate eight 1‐alkylpyridinium‐based ionic liquids of the form [C_nPy][A] by using X‐ray photoelectron spectroscopy (XPS). The electronic environment of each element of the ionic liquids is analyzed. In particular, a reliable fitting model is developed for the C 1s region that applies to each of the ionic liquids. This model allows the accurate charge correction of binding energies and the determination of reliable and reproducible binding energies for each ionic liquid. Shake‐up/off phenomena are determinedfor both C 1s and N 1s spectra. The electronic interaction between cations and anions is investigated for both simple ionic liquids and an example of an ionic‐liquid mixture; the effect of the anion on the electronic environment of the cation is also explored. Throughout the study, a detailed comparison is made between [C₈Py][A] and analogues including 1‐octyl‐1‐methylpyrrolidinium‐ ([C₈C₁Pyrr][A]), and 1‐octyl‐3‐methylimidazolium‐ ([C₈C₁Im][A]) based samples, where X is common to all ionic liquids.     

The Synthesis of Anatase TiO2 Nanoparticles by Solvothermal Method using Ionic Liquid as Additive

The solvothermal reactions of Ti(OiPr)₄ in alcohol using ionic liquid as additive were investigated. In the presence of [BMIM][Cl], [BMIM][Br], [BMIM][NTf₂], [BMIM][SO₃Me], [BMIM][SO₄Me], or [BMIM][OTf] (BMIM = 1‐Butyl‐3‐methylimidazolium), pure anatase nanoparticles were obtained. The controlled hydrolysis of Ti(OiPr)₄ in the presence of ionic liquids to form titanium oxo clusters plays a key role in the formation of anatase nanostructures, and ionic liquids can be repeatedly used to synthesise anatase nanoparticles. However, in the presence of [BMIM][PF₆], [BMIM]₂[Ti(OH)₆] was obtained by an anion exchange reaction.     

Temperature‐controlled ionic liquid dispersive liquid‐phase microextraction combined with HPLC with ultraviolet detector for the determination of fungicides

Present study described a simple, environmental benign, easy to operate, and determination method for fungicides including thiram, metalaxyl, diethofencarb, myclobutanil, and tebuconazole. The method is based on temperature‐controlled ionic liquid dispersive liquid phase microextraction coupled to HPLC with ultraviolet detector. In the enrichment procedure, ionic liquid 1‐octyl‐3‐methylimidazolium hexafluorophosphate [C₈MIM][PF₆] was used as the extraction solvent. Variable affecting parameters such as the volume of [C₈MIM][PF₆], temperature, extraction time, centrifuging time, and salting‐out effect have been optimized in detail. Under the optimal conditions, this method has been found to have good linear relationship in the concentration range of 1.0–100 μg/L and excellent detection sensitivity with LODs (S/N = 3) in the range of 0.32–0.79 μg/L. Precisions of proposed method were in the range of 3.7–5.9% for intraday and 7.8–11.0% for interday (RSDs, n = 6). The proposed method was used for the analysis of real water samples and good spiked recoveries at two different spiked levels were achieved in the range of 84.6–102%.     

Speciation of Rare‐Earth Metal Complexes in Ionic Liquids: A Multiple‐Technique Approach

The dissolution process of metal complexes in ionic liquids was investigated by a multiple‐technique approach to reveal the solvate species of the metal in solution. The task‐specific ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf₂N]) is able to dissolve stoichiometric amounts of the oxides of the rare‐earth elements. The crystal structures of the compounds [Eu₂(bet)₈(H₂O)₄][Tf₂N]₆, [Eu₂(bet)₈(H₂O)₂][Tf₂N]₆?2H₂O, and [Y₂(bet)₆(H₂O)₄][Tf₂N]₆ were found to consist of dimers. These rare‐earth complexes are well soluble in the ionic liquids [Hbet][Tf₂N] and [C₄mim][Tf₂N] (C₄mim=1‐butyl‐3‐methylimidazolium). The speciation of the metal complexes after dissolution in these ionic liquids was investigated by luminescence spectroscopy, ¹H, ¹³C, and ⁸⁹Y NMR spectroscopy, and by the synchrotron techniques EXAFS (extended X‐ray absorption fine structure) and HEXS (high‐energy X‐ray scattering). The combination of these complementary analytical techniques reveals that the cationic dimers decompose into monomers after dissolution of the complexes in the ionic liquids. Deeper insight into the solution processes of metal compounds is desirable for applications of ionic liquids in the field of electrochemistry, catalysis, and materials chemistry.     

Improved Voltammetric Response of L‐Tyrosine on Multiwalled Carbon Nanotubes‐Ionic Liquid Composite Coated Glassy Electrodes in the Presence of Cupric Ion

L ‐Tyrosine can exhibit a small anodic peak on multiwalled carbon nanotubes (MWCNTs) coated glassy carbon electrodes (GCE). At pH 5.5 its peak potential is 0.70 V (vs. SCE). When an ionic liquid (i.e., 1‐octyl‐3‐methylimidazolium hexafluorophosphate, [omim][PF₆]) is introduced on the MWCNT coat, the peak becomes bigger. Furthermore, in the presence of Cu²⁺ ion the anodic peak of L ‐tyrosine increases further due to the formation of Cu²⁺‐L ‐tyrosine complex, while the peak potential keeps unchanged. Therefore, a sensitive voltammetry based on the oxidation of Cu²⁺‐L ‐tyrosine complex on MWCNTs‐[omim][PF₆] composite coated electrode is developed for L ‐tyrosine. Under the optimized conditions, the anodic peak current is linear to L ‐tyrosine concentration in the range of 1×10^?8–5×10^?6 M, and the detection limit is 8×10^?9 M. The modified electrode shows good reproducibility and stability. In addition, the voltammetric behavior of other amino acids is explored. It is found that among them tryptophan (Trp) and histidine (His) can also produce sensitive anodic peak under same experimental conditions, and their detection limits are 4×10^?9 M and 4×10^?6 M, respectively.     

Ultrafast FRET to Study Spontaneous Micelle‐to‐Vesicle Transitions in an Aqueous Mixed Surface‐Active Ionic‐Liquid System

The spontaneous micelle‐to‐vesicle transition in an aqueous mixture of two surface‐active ionic liquids (SAILs), namely, 1‐butyl‐3‐methylimidazolium n‐octylsulfate ([C₄mim][C₈SO₄]) and 1‐dodecyl‐3‐methylimidazoium chloride ([C₁₂mim]Cl) is described. In addition to detailed structural characterization obtained by using dynamic light scattering, transmission electron microscopy (TEM), and cryogenic TEM techniques, ultrafast fluorescence resonance energy transfer (FRET) from coumarin 153 (C153) as a donor (D) to rhodamine 6G (R6G) as an acceptor (A) is also used to study micelle–vesicle transitions in the present system. Structural transitions of SAIL micelles ([C₄mim][C₈SO₄] or [C₁₂mim]Cl micelles) to mixed SAIL vesicles resulted in significantly increased D –A distances, and therefore, increased timescale of FRET. In [C₄mim][C₈SO₄] micelles, FRET between C153 and R6G occurs on an ultrafast timescale of 3.3 ps, which corresponds to a D –A distance of about 15 Å. As [C₄mim][C₈SO₄] micelles are transformed into mixed micelles upon the addition of a 0.25 molar fraction of [C₁₂mim]Cl, the timescale of FRET increases to 300 ps, which suggests an increase in the D –A distance to 31 Å. At a 0.5 molar fraction of [C₁₂mim]Cl, unilamellar vesicles are formed in which FRET occurs on multiple timescales of about 250 and 2100 ps, which correspond to D –A distances of 33 and 47 Å. Although in micelles and mixed micelles the obtained D –A distances are well correlated with their radius, in vesicles the obtained D –A distance is within the range of the bilayer thickness.     

Ionic liquids enhanced oil recovery from oily sludge-experiment and mechanism

The oily sludge would cause environment pollution, and would cause the heavy oil waste. Therefore, it was vital for us to find novel methods to obtain heavy oil from the oily sludges. In this study, the [C₁₂mim][PF₆] and [C₁₂mim][Br] ionic liquids(ILs) were used to enhance the oil recovery. The toluene could obtain the highest oil recovery, and both the two ILs could increase the oil recovery. Toluene could obtain the highest oil recovery (89.4 wt%), and n-octane could obtain the lowest oil recovery (76.8 wt%). [C₁₂mim] [PF₆] could efficiently increase the heavy oil recovery to 91.2 wt%(by toluene). The [C₁₂mim][Br] could increase the heavy oil recovery further. Both the [C₁₂mim] [PF₆] and the [C₁₂mim][Br] ionic liquids could increase the heavy ois C/H ratio, decrease heavy oil viscosity and increase the sands hydrophilicity. The [C₁₂mim][Br] ionic liquids showed better effect. In addition, the ionic liquids could increase the solvents recovery, and the ionic liquids recovery were high. Therefore, the ionic liquids enhanced oil recovery could be recycled to ten times. The two ionic liquids could effectively decrease the heavy oil interaction force, and when the ionic liquids increased to 200 ppm, the force remained stable. In the end, the ionic liquids enhancing solvent extraction mechanism was put forward.     

The influence of an electric field on the wetting of an SiO2 film by ionic liquids

The electrowetting of a dielectric SiO₂ film 100 nm thick by drops (D = 2–3 mm) of [C₄mIm][PF₆], [C₆mIm][PF₆], and [C₆mIm][BTI] ionic liquids was studied at |U| ≤ 60 V in a ～10^?8 mbar vacuum. Electrocapillary curves of the dependence of the wetting angle on electric field potential were constructed with an accuracy of ±1 deg. In conformity with the Young-Lippman equation, the wetting angle θ° decreased by the parabolic law from 51° to 43° for [C₄mIm][PF₆], from 48° to 38° for [C₆mIm][PF₆], and from 35° to 27° for [C₆mIm][BTI] as |U| increased at 298 K. The electrocapillary curve branches were situated symmetrically in the (θ°, U) coordinates with respect to the line passing through the point U = 0; that is, zero-charge potential is zero for the electrowetting of the dielectric film by the ionic liquids. The capacitance of the double electrical layer at the ionic liquid-dielectric interface was determined. This value was found to be 4.65, 2.93, and 1.73 μF/m² for the electrowetting of the SiO₂ film at 298 K by the ionic liquids specified, respectively.     

Temperature‐controlled ionic liquid‐dispersive liquid‐phase microextraction for preconcentration of chlorotoluron,diethofencarb and chlorbenzuron in water samples

This article describes a new, rapid and sensitive method for the determination of chlorotoluron, diethofencarb and chlorbenzuron from water samples with temperature‐controlled ionic liquid‐dispersive liquid‐phase microextraction. In the preconcentration procedure, ionic liquid 1‐hexyl‐3‐methylimidazolium hexafluorophosphate [C₆MIM] [PF₆] was employed as the extraction solvent. The parameters, such as volume of [C₆MIM] [PF₆], sample pH, extraction time, centrifuging time, temperature and salting‐out effect, were investigated in detail. Under the optimal extraction conditions, it has been found that three analytes had excellent LODs (S/N=3) in the range of 0.04–0.43 μg/L. The RSDs (n=6) were in the range of 1.3–4.7%. The proposed method was evaluated with lake water, tap water and melted snow water samples. The experimental results indicated that the proposed method had excellent prospect and would be widely used in the future.     

l‐Lysine‐derived ionic liquids as chiral ligands of Zn(II) complexes used in ligand‐exchange CE

Amino acid ionic liquids (AAILs) with l ‐lysine (l ‐Lys) as anion were synthesized and applied as new chiral ligands in Zn(II) complexes for chiral ligand‐exchange CE. After effective optimization, baseline enantioseparation of seven pairs of dansylated amino acids was achieved with a buffer of 100.0 mM boric acid, 5.0 mM ammonium acetate, 3.0 mM ZnSO₄, and 6.0 mM [C₆mim][l ‐Lys] at pH 8.2. To validate the unique behavior of AAILs, a comparative study between the performance of Zn(II)‐l ‐Lys and Zn(II)‐[C₆mim][l ‐Lys] systems was conducted. In Zn(II)‐[C₆mim][l ‐Lys] system, it has been found that the improved chiral resolution could be obtained and the migration times of the three test samples were markedly prolonged. Then the separation mechanism was further discussed. The role of [C₆mim][l ‐Lys] indicated clearly that the synthesized AAILs could be used as chiral ligands and would have potential utilization in separation science in future.     

Room temperature ionic liquid as a novel medium for liquid/liquid extraction of metal ions

Room temperature ionic liquids (RTILs) have been used as novel solvents to replace traditional volatile organic solvents in organic synthesis, solvent extraction, and electrochemistry. The hydrophobic character and water immiscibility of certain ionic liquids allow their use in solvent extraction of hydrophobic compounds. In this work, a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆], was used as an alternative solvent to study liquid/liquid extraction of heavy metal ions. Dithizone was employed as a metal chelator to form neutral metal-dithizone complexes with heavy metal ions to extract metal ions from aqueous solution into [C₄mim][PF₆]. This extraction is possible due to the high distribution ratios of the metal complexes between [C₄mim][PF₆] and aqueous phase. Since the distribution ratios of metal dithiozonates between [C₄mim][PF₆] and aqueous phase are strongly pH dependent, the extraction efficiencies of metal complexes can be manipulated by tailoring the pH value of the extraction system. Hence, the extraction, separation, and preconcentraction of heavy metal ions with the biphasic system of [C₄mim][PF₆] and aqueous phase can be achieved by controlling the pH value of the extraction system. Preliminary results indicate that the use of [C₄mim][PF₆] as an alternate solvent to replace traditional organic solvents in liquid/liquid extraction of heavy metal ions is very promising.     

Hydrophobic ionic liquid‐based ultrasound‐assisted extraction of magnolol and honokiol from cortex Magnoliae officinalis

The hydrophobic ionic liquid of [BMIM][PF₆] was successfully used for the ultrasound‐assisted extraction of hydrophobic magnolol and honokiol from cortex Magnoliae officinalis. To obtain the best extraction efficiencies, some ultrasonic parameters including the concentration of [BMIM][PF₆], pH, ultrasonic power and ultrasonic time were evaluated. The results obtained indicated that the [BMIM][PF₆]‐based ultrasound‐assisted extraction efficiencies of magnolol and honokiol were greater than those of the [BMIM][BF₄]‐based ultrasound‐assisted extraction (from 48.6 to 45.9%) and the traditional ethanol reflux extraction (from 16.2 to 13.3%). Furthermore, the proposed extraction method is validated by the recovery, correlation coefficient (R²) and reproducibility (RSD, n=5), which were 90.8–102.6, 0.9992–0.9998, and 1.6–5.4%, respectively.     

Preparative isolation of neomangiferin and mangiferin from Rhizoma anemarrhenae by high‐speed countercurrent chromatography using ionic liquids as a two‐phase solvent system modifier

A preparative high‐speed countercurrent chromatography method for isolation and purification of neomangiferin and mangiferin from Rhizoma anemarrhenae was successfully established by using ionic liquids as the modifier of the two‐phase solvent system. Neomangiferin and mangiferin were purified from the crude extract of R. anemarrhenae by using ethyl acetate‐water‐[C₄mim][PF₆] (5:5:0.2 v/v) as two‐phase solvent system. In total, 22.5 mg of neomangiferin and 70.6 mg of mangiferin were obtained from 150 mg of the crude extract. The purities of neomangiferin and mangiferin were 97.2 and 98.1%, respectively, as determined by HPLC. The chemical structures of the isolated compounds were identified by ¹H‐NMR and ¹³C‐NMR.     

Synthesis of 2‐Phenylthiazoles from α‐Tosyloxyketones and Thiobenzamide in [Bmim][PF6] Ionic Liquid at Ambient Temperature

The room temperature ionic liquid, 1‐n‐butyl‐3‐methylimidazolium hexafluorophosphate [bmim][PF₆] is used as a ‘green’ recyclable alternative to classical molecular solvents for the cyclocondensation of α‐tosyloxyketones with thiobenzamide to prepare 2‐phenylthiazoles in good yields.     

离子液体型表面活性剂研究

以1-甲基咪唑为原料, 制备了6个常规离子液体: 1-正丁基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[bmim][BF₄]及[bmim][PF₆])、1-正己基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[hmim][BF₄]及[hmim][PF₆])、1-正十六烷基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[C₁₆mim][BF₄]及[C₁₆mim][PF₆])和4个功能化离子液体: 1-(2-羟乙基)-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[2-hemim][BF₄]及[2-hemim][PF₆])、1-乙氧羰基甲基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[eocmmim][BF₄]及[eocmmim][PF₆]). 研究了这两类离子液体的一些物理性能, 旨在挖掘离子液体在香料香精化妆品工业中的应用价值. 分别检测了它们与一般溶剂的互溶性, 并测定了它们的表面张力和发泡性能, 实验结果表明, 仅[C₁₆mim][BF₄]和[C₁₆mim][PF₆]具有发泡性能, 发泡力分别为68和120 mm.     

Acceleration of the Baylis–Hillman Reaction in the Presence of Ionic Liquids

The Baylis–Hillman reaction is accelerated in the presence of ionic liquids. Of various 1‐butyl‐3‐methylimidazolium (bmim)‐based ionic liquids tested, [bmim][PF₆] has been found to result in the highest rate increase. In the company of Lewis acid and H‐bond‐donor additives, the reaction rates further improve, albeit only modestly. A preparatively useful Baylis–Hillman procedure prescribes the use of [bmim][PF₆] with La(OTf)₃ and 2,2′2″‐nitrilotris[ethanol], in which the net effect of the ionic liquid is to bring about a more than twofold rate increase over the otherwise same reaction in MeCN.     

Nanoscale organization of ionic liquids and their interaction with peptides probed by C NMR spectroscopy

An NMR study of 10 l-alanine- and l-valine-containing peptides was carried out in the native [C₂MIM][Cl], [C₄MIM][Cl], [C₆MIM][Cl], [C₄MIM][BF₄], [C₄MIM][PF₆], and [C₄Py][BF₄] ionic liquid media. A unique high sensitivity of the ionic liquid system to the nature of peptide and ability to tune solvent–solute interactions were observed in contrast to regular organic solvents. The l-valine peptides can be selectively dissolved in [C₄MIM][Cl] and [C₆MIM][Cl], whereas their solubility in [C₂MIM][Cl] and other ionic liquids was dramatically lower. In spite of structural similarity between the amino acids, a distinct behavior was observed for the l-alanine peptides. Solvent–solute interactions with an ionic liquid impose significant changes, and NMR spectroscopy is a useful probe for the molecular-level and nanoscale organization of the studied systems. An even/odd effect of the number of amino acids in the peptide on molecular interactions in ionic liquids was observed. Enhancement of chemical properties of peptides in ionic liquids and application of ionic liquids in the separation of peptides are the areas of practical interest in the studied systems.     

Ionic liquid-based single-drop liquid-phase microextraction combined with high-performance liquid chromatography for the determination of sulfonamides in environmental water

A simple, rapid and environment‐friendly technique of single‐drop liquid‐phase microextraction has been developed for the determination of sulfonamides in environmental water. Several important parameters including stirring rate, extraction solvent, extraction pH, salinity and extraction time were optimized to maximize the extract efficiency. Extraction solvent 1‐octyl‐3‐methylimidazolium hexafluorophosphate [C₈MIM][PF₆] ionic liquid showed better extraction efficiency than 1‐butyl‐3‐methylimidazolium hexafluorophosphate [C₄MIM][PF₆] and 1‐octanol. The optimum experimental conditions were: pH, 4.5; sodium chloride content, 36% w/v; extraction time, 20 min. This method provided low detection limits (0.5–1 ng/mL), good repeatability (the RSD ranging from 4.2 to 9.9%, n=5) and wide linear range (1–1500 ng/mL), with determination coefficients (r²) higher than 0.9989 for all the target compounds. Real sample analysis showed relative recoveries between 63.5 and 115.8% for all the target compounds.     

Salicylaldoxime‐functionalized poly(ethylene glycol)‐bridged dicationic ionic liquid ([salox‐PEG1000‐DIL][BF4]) as a novel ligand for palladium‐catalyzed Suzuki–Miyaura reaction in water

Two novel salicylaldoxime‐functionalized poly(ethylene glycol)‐bridged dicationic ionic liquids ([salox‐PEG₁₀₀₀‐DIL][BF₄] and [salox‐PEG₁₀₀₀‐DIL][PF₆]) were prepared and characterized. [salox‐PEG₁₀₀₀‐DIL][BF₄] was found to be an efficient and recyclable ligand for palladium‐catalyzed Suzuki–Miyaura reaction in water. The catalytic system could be easily recovered and reused for at least five runs only with slight decrease in its activity. Copyright © 2013 John Wiley & Sons, Ltd.