Ionic liquid-based dispersive liquid–liquid microextraction for the separation and preconcentration of lead in water samples prior to FAAS determination without chelating agent

In the present study, an environment-friendly sample preparation method termed ionic liquid-based dispersive liquid–liquid microextraction combined with flame atomic absorption spectrometry has been developed for the determination of Pb(II) ion in water samples prior to flame atomic absorption spectrometry determination. In this method, ionic liquid was used as an extraction solvent instead of the organic solvent used in the conventional dispersive liquid–liquid microextraction (DLLME) assay, and there is no need for a chelating agent. Several variables that may affect extraction efficiencies, including pH, the volume of ionic liquid, the type and volume of disperser solvent, salt addition, and the time for centrifugation and extraction were studied and optimised. Under the optimised conditions, the calibration curve exhibited linearity over the range of 20.0–1000.0 μg L^?1. The enrichment factor and the limit of detection based on 3S_b/m were 35.0 and 5.9 μg L^?1, respectively. Seven replicate determination of a solution containing of 100.0 μg L^?1 Pb(II) ions gave a relative standard deviation of ±2.1%. Finally, the feasibility of the proposed method for Pb(II) determination was assessed by the analysis of certi?ed reference material and various water samples and the satisfactory results were obtained.     

Determination of Copper in Water by Ionic Liquid Based Microextraction and Chemiluminescence Detection

A versatile, sensitive, and green method based ultrasound-assisted, temperature-controlled, dispersive liquid–liquid microextraction with an ionic liquid and chemiluminescence detection was used for the determination of copper(II) at the ultra-trace level. After complexation by dithizone, copper(II) was extracted into the ionic liquid. Using high temperature and ultrasonic agitation, the copper complex easily migrated into the ionic liquid phase because of the larger contact area. After back extraction, the determination was performed by chemiluminescence based on the catalyzing effect of copper(II) on the decomposition of hydrogen peroxide with rhodamine B. Important parameters that affected the extraction efficiency and chemiluminescence intensity were optimized. Under the optimum conditions, a limit of detection for copper of 0.8 ng L^?1 was obtained with a linear calibration relationship. The method was applied to analyze environmental water samples for copper(II) with satisfactory results.     

Polyimidazolyl acetate ionic liquid grafted on cellulose filter paper as thin-film extraction phase for extraction of non-steroidal anti-inflammatory drugs from water

Recently, pharmaceuticals and personal care products in the water environment exhibited potential risks to both human and aquatic organisms. In order to improve the sensitivity and accuracy of pharmaceutical detection, the polyimidazolyl acetate ionic liquid was synthesized by Radziszewski reaction and coated on cellulose filter papers as a thin-film extraction phase for extraction of non-steroidal anti-inflammatory drugs from water. The attenuated total reflection-infrared spectrometry, thermogravimetric analysis, and scanning electron microscope analyses demonstrated that the polyimidazolyl acetate ionic liquid was successfully prepared and attached to the surface of the cellulose filter paper through chemical bonding. The adsorption capacity of the homemade thin-film extraction material for the four non-steroidal anti-inflammatory drugs was greater than 8898 ng/cm² under the optimum conditions, and the desorption rate was over 90%. Then, a paper-based thin-film extraction phase-high-performance liquid chromatography-tandem mass spectrometry method was established for the extraction of non-steroidal anti-inflammatory drugs in water. This method provided limits of detection and limits of quantification were in the range of 0.02–0.15 and 0.17–0.50 μg/L, respectively. Hence, the obtained thin-film extraction phase showed excellent recovery and reproducibility for the target non-steroidal anti-inflammatory drugs with carboxyl groups from water.     

Semidilute solution structure of cellulose in an ionic liquid and its mixture with a polar organic co‐solvent studied by small‐angle X‐ray scattering

Structural and thermodynamic properties of cellulose solutions in the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate (EMIMAc) and its binary mixtures with N,N‐dimethyl formamide (DMF) are studied by small‐angle X‐ray scattering (SAXS). These measurements indicate molecular dissolution of the cellulose chains without any significant aggregation. The power–law relationships of the evaluated correlation length and osmotic modulus to concentration exhibit exponents of ?0.76 and 2.06 for EMIMAc and ?0.80 and 2.14 for DMF/EMIMAc solvent mixture, respectively. Thus, these solvents can be considered to be good solvents for cellulose. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 888–894     

Application of ionic liquid-based ultrasonic-assisted microextraction coupled with HPLC for determination of citalopram and nortriptyline in human plasma

In this paper, an effective and environmentally friendly method of ultrasound-assisted ionic liquid-based dispersive liquid–liquid microextraction (UA-IL-DLLME) combined with high-performance liquid chromatography (HPLC)–photodiode array detector was applied for extraction and determination of two antidepressant drugs citalopram hydrobromide and nortriptyline hydrochloride from human plasma samples. Several important parameters affect the steps and efficiency of extraction, some of which are sample solution’s pH, type and volume of ionic liquid, ultrasonic time, centrifuging time and rate, and the ionic strength of solution. Optimum conditions were obtained at pH?=?11, 1-octyl-3-methyl imidazolium hexafluorophosphate for ionic liquid, 55?µL for ionic liquid volume, 4?min for ultrasonic time, 5?min and 3,500?rpm for centrifuging time and rotation’s speed, due to ionic strength by the addition of NaCl 1%. Under optimized conditions, the linearity was obtained in the range of 0.02–2,000?µg/L, with correlation coefficients higher than 0.995. The limits of detection were 10?µg/L for citalopram and 6?µg/L for nortriptyline. Preconcentration factors were 920 for citalopram and 800 for nortriptyline. The present method of UA-IL-DLLME combined with HPLC was successfully used for the determination of citalopram and nortriptyline drugs in real samples of human plasma.     

Room-Temperature Ionic Liquid and Multi-Walled Carbon Nanotube Composite Modified Carbon-Ceramic Electrode as a Sensitive Voltammetric Sensor for Indomethacin

The electrochemical behavior of indomethacin on the surface of a carbon-ceramic electrode modified with multi-walled carbon nanotubes and an ionic liquid composite film is reported. The results show that the nano-structured film exhibited excellent enhancement effects on the electrochemical oxidation of indomethacin. The developed sensor presented a linear response to indomethacin over the concentration range from 1 to 50 µM with a detection limit of 0.26 µM. The proposed modified electrode was employed for the determination of indomethacin in biological and pharmaceutical samples using differential pulse voltammetry.     

Electro‐optical cells using a cellulose derivative and cholesteric liquid crystals

A cellulose derivative/liquid crystal composite‐type electro‐optical cell using a commercial cholesteric liquid crystal (CLC) was investigated. The electro‐optical properties of the system were examined, i.e. the dependence on applied voltage of the reflected wavelength and the minimum and maximum transmissions. A thin film of the CLC was dispersed with a cross‐linked cellulose film of 25 µm thickness. In the voltage dependence of the reflected wavelength it was verified that there is a hysteresis in the reflected wavelength. The variation of the reflected wavelength with temperature was also determined. The results are analysed in the framework of similar systems described in the literature for CLC dispersed in a polymer matrix.     

Simultaneous Nonchiral Determination of Artemisinin and Arteannuin B in Artemisia annua Using Circular Dichroism Detection

A new method was performed using on-line coupling of nonchiral reversed-phase liquid chromatography (RP-LC) to circular dichroism (CD) spectroscopy for simultaneous determination of artemisinin and arteannuin B in crude plant extracts of Artemisia annua. Analysis was carried out on an LC–CD system equipped with an Agilent TC-C₁₈ column (4.6 mm I.D. × 200 mm L, 5 μm) using gradient of acetonitrile. The method was validated to be practicable and reliable at alterable wavelength in the ranges of 220–420 nm as desired. LOD and LOQ of artemisinin and arteannuin B were 0.08, 0.26 and 0.31, 1.02 μg mL⁻¹, respectively. It was more sensitive than conventional LC–UV and comparatively cheaper than LC–MS in analysis of TCM.

     

离子液体作高效液相色谱流动相添加剂测定水杨酸

建立了以离子液体作反相高效液相色谱流动相添加剂测定水杨酸的方法.实验以ZORBAX ODS反相色谱柱为分离柱,采用紫外检测方法,研究了检测波长、离子液体烷基链长度、离子液体溶液的浓度以及pH值等对分离和测定的影响.优化的色谱条件为:以体积比60:40的甲醇-3.0 mmol/L1-丁基-3-甲基咪唑四氟硼酸盐溶液(乙酸...     

Determination of Antimony(III) by Differential Pulse Voltammetry Using a Gold Nanoparticle–Ionic Liquid–Graphene-Modified Selenium-Doped Carbon Paste Electrode

A simple and sensitive differential pulse stripping voltammetric method was developed for the determination of antimony(III) using a selenium-doped carbon paste electrode modified with an ionic liquid, graphene, and gold nanoparticles. The conditions, including the mass of graphene, concentration of hydrochloric acid, deposition potential, and deposition time were optimized by single-factor experiments. Under the optimal conditions, a linear equation of I_Sb(III) (µA)?=??16.9882???11.0929 c (µmol/L) (R?=?0.9965) and a detection limit of 2.7?×?10^?8?mol/L were obtained for 8.0?×?10^?8 to 4.8?×?10^?6?mol/L antimony(III). The response shows that the sensor enhances the sensitivity of antimony due to the high conductivity and large surface areas of the ionic liquid, graphene, and gold nanoparticles. This electrode may provide a new sensing platform for the determination of antimony.     

Determination of Cadmium in Human Serum and Blood Samples after Dispersive Liquid–Liquid Microextraction Using a Task-Specific Ionic Liquid

Task-specific ionic liquid dispersive liquid–liquid microextraction (TSIL-DLLME) is a simple and rapid preconcentration approach for the measurement of cadmium in serum and blood samples of human subjects. In this method a novel task-specific ionic liquid, trioctylmethyl ammonium thiosalicylate (TOMATS), which has dual characteristics as a chelating agent and extractive solvent, was investigated. TOMATS complexes with Cd due to the chelating effect of the ortho-positioned carboxylate relative to the thiol functionality. The assessment of the optimum values of variables including the pH, amount of reagents (TOMATS, diluents, Triton X114, and back extracting acid solution), temperature, and incubation time, which affect the recoveries of analyte by TSIL-DLLME method were studied. After enrichment experiments, acidic solution was used to back extract the metal ions from the ionic liquid rich phase and with determination by electrothermal atomic absorption spectrometry. Using the optimal experimental conditions, the limit of detection (3?s), precision (relative standard deviation), preconcentration, and enhancement factors of developed method for Cd were found to be 0.05?µg/L, greater than 5%, 62.5, and 52.8, respectively. To check the accuracy of the developed method, certified reference material of serum and blood were analyzed by the developed method, and the measured values of Cd were in good agreement with the certified values. The developed method was applied successfully to determine Cd in blood and serum samples of lymphatic cancer patients relative to healthy controls.     

The Effect of Ionic Liquid Covalent Bonding to Sol‐Gel Processed Film on Ion Accumulation and Transfer

Accumulation of electroactive anions into a silicate film with covalently bonded room temperature ionic liquid film deposited on an indium tin oxide electrode was studied and compared with an electrode modified with an unconfined room temperature ionic liquid. A thin film containing imidazolium cationic groups was obtained by sol‐gel processing of the ionic liquid precursor 1‐methyl‐3‐(3‐trimethoxysilylpropyl)imidazolium bis(trifluoromethylsulfonyl)imide together with tetramethylorthosilicate on the electrode surface. Profilometry shows that the obtained film is not smooth and its approximate thickness is above 1 μm. It is to some extent permeable for a neutral redox probe – 1,1′‐ferrocene dimethanol. However, it acts as a sponge for electroactive ions like Fe(CN)₆^3?, Fe(CN)₆^4? and IrCl₆^3?. This effect can be traced by cyclic voltammetry down to a concentration equal to 10^?7 mol dm^?3. Some accumulation of the redox active ions also occurs at the electrode modified with the ionic liquid precursor, but the voltammetric signal is significantly smaller compare with the bare electrode. The electrochemical oxidation of the redox liquid t‐butyloferrocene deposited on silicate confined ionic liquid film is followed by the expulsion of the electrogenerated cation into an aqueous solution. On the other hand, the voltammetry obtained with the electrode modified with t‐butyloferrocene solution in the ionic liquid precursor exhibits anion sensitive voltammetry. This is explained by anion insertion into the unconfined ionic liquid deposit following t‐butylferricinium cation formation.     

Ligandless,Task-Specific Ionic Liquid-Based Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction for the Determination of Cobalt Ions by Electrothermal Atomic Absorption Spectrometry

Ligandless, task-specific ionic liquid based ultrasound-assisted dispersive liquid–liquid microextraction (TSIL-USA-DLLME) was used for preconcentration of cobalt ions in food and water samples and in vitamin supplements before analysis by electrothermal atomic absorption spectrometry. The reported method is free of toxic volatile organic solvents and does not require the use of a back-extraction step. The dispersion of extractant was achieved with the use of ultrasound. A TSIL, trioctylmethylammonium thiosalicylate (TOMATS), was served as both the extraction and complexing agent. After microextraction, the TOMATS phase was separated by centrifugation and dissolved in ethanol before analysis. Selected parameters affecting the microextraction including the pH of the sample, the volume of the ionic liquid, the ultrasonication time, centrifugation parameters, and the influence of ionic strength were optimized. The limit of detection was 0.011?ng?mL^?1 for cobalt ions. The achieved preconcentration factor was 24. The relative standard deviations for the determination of analyte in the real samples were 3–24%. The accuracy of this method was evaluated by the extraction and determination of the analyte in several certified reference materials including INCT-SBF-4 (soya bean flour), INCT-TL-1 (tea leaves), ERM-CAO11b (hard drinking water), INCT-MPH-2 (mixed Polish herbs), TMDA-54.5 (Lake Ontario Water), and NIST 1643e. The measured cobalt contents were in satisfactory agreement with the certified concentrations based on Student’s t-test at the 95% confidence level. The presented method has been successfully applied for the determination of analyte in real samples that include tea, lake water, and vitamin supplements.     

Determination of Cysteine at Bismuth Nanostructure – Carbon Ionic Liquid Electrode by Square Wave Voltammetry

Bismuth nanostructure‐carbon ionic liquid electrode has been employed for sensitive determination of cysteine (Cys). Bismuth nanostructure was incorporated into the carbon ionic liquid electrode (CILE) and applied for determination of cysteine. An interaction was taking place between bismuth nanostructure and the thiol group of cysteine. The bismuth cysteinate complex oxidation potential occurred at more negative potential compared to the cysteine oxidation peak obtained at bare carbon ionic liquid electrode (CILE). Square wave voltammetry (SWV) was used for the determination of the cysteine and satisfactory results were obtained. The calibration curve was linear in the concentration range of 1 to 500 µM and 0.5–2 mM of Cys. A low detection limit of 0.5 µM was achieved for Cys. The electrode showed a good selectivity for determination of cysteine in the presence of other amino acids. The proposed electrode was satisfactory applied for the determination of cysteine in human serum plasma sample.     

Three-way Resolution of the Overlapping Ultrahigh-performance Liquid Spectrochromatograms for the Analysis of a Quaternary Mixture Using Parallel Factor Analysis

This paper presents a new application of three-way parallel factor analysis (3W-PARAFAC) model to the coeluting spectrochromatograms for the quantitative resolution of a quaternary mixture system consisting of paracetamol, propyphenazone, and caffeine with aspirin as an internal standard. Spectrochromatograms of calibration standards, validation sets, and unknown samples were recorded as a function of retention time and wavelength in the range of 0.0–2.5?min and 200–400?nm, respectively, using ultra-performance liquid chromatography with photodiode array detection (UPLC-PDA). Three-way UPLC-PDA data array X (retention time?×?wavelength?×?sample) was obtained from the data matrices of the spectrochromatograms. 3W-PARAFAC decomposition of three-way UPLC-PDA data array provided three loading matrices corresponding to chromatographic mode, spectral mode, and relative concentration mode. Quantitative estimation of paracetamol, propyphenazone, and caffeine in analyzed samples was accomplished using the relative concentration mode obtained by the deconvolution of the UPLC-PDA data set. The validity and ability of 3W-PARAFAC model were checked by analyzing independent test samples. It was observed from analyses that 3W-PARAFAC method has potential to uniquely resolve strongly overlapping peaks of analyzed compounds in a spectrochromatogram, which was obtained under experimental conditions consisting of the lower flow rate, short run time, and simple mobile phase composition. The proposed three-way chemometric approach was successfully applied to the simultaneous quantification of paracetamol, propyphenazone, and caffeine in tablets. Experiments showed that the determination results were in good agreement with label amount in commercial pharmaceutical preparation.     

Determination of Polycyclic Aromatic Hydrocarbons in Tobacco Smoke by Ionic Liquid Enrichment and Gas Chromatography – Mass Spectrometry

A rapid, efficient and environmentally friendly method based on the ionic liquid (IL) 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) was developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in mainstream tobacco smoke. This technique combined ionic liquid (IL) enrichment with solvent reverse extraction for the replacement of solid phase extraction and rotary evaporation in the traditional method and enriched PAHs in the organic solvent. Several parameters, including the type of ionic liquid, volume of ionic liquid and water, extraction time, vortex time and reverse extraction time, were optimized. After pretreatment, the analytes were analyzed by gas chromatography-mass spectrometry (GC-MS) using selective ion monitoring (SIM). Satisfactory results were achieved when this method was applied to determine PAHs in mainstream tobacco smoke. The calibration curves were linear with correlation coefficients ranging from 0.9955 to 0.9999 at concentration levels of 10–800?µg?L^?1, and the relative standard deviations of the optimized method were between 0.7% and 5.3%. The limits of detection were 0.01–0.6?ng cig^?1, and the recoveries of the compounds were 80.2–118%. A comparison of this protocol with literature methods demonstrated that the proposed procedure provides accurate and reliable sample-treatment for the determination of PAHs in tobacco samples.     

Application of dispersive liquid–liquid microextraction for the determination of donepezil in urine by HPLC using a core–shell column

A rapid and novel method combining dispersive liquid–liquid microextraction and high-performance liquid chromatography coupled with fluorescence detection was developed for the determination of donepezil in human urine. Parameters affecting extraction efficiency and chromatographic determination, such as the type and volume of the extraction and disperser solvent, pH of sample for dispersive liquid–liquid microextraction, mobile-phase composition, pH, column oven temperature, and flow rate for chromatographic determination, were evaluated and optimized. Using a C₁₈ core–shell column (7.5 × 4.6?mm, 2.7?μm), the determination of donepezil was accomplished within 5?min. Under optimum conditions, developed method was linear in the range of 0.5–25?ng?mL^?1 with the correlation coefficient >0.99. Limit of detection was 0.15?ng?mL^?1. The relative standard deviation at three concentration levels (2, 12.5, and 20?ng?mL^?1) was less than 11% with accuracy in the range of 96.9–102.8%. The results of this study demonstrate that the use of dispersive liquid–liquid microextraction and core–shell column can be considered as a powerful tool for the analysis of donepezil in human urine.     

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.     

Partial cellulose acetylation in 1-ethyl-3-methylimidazolium acetate induced by dichloromethane

Cellulose acetate (CA) is one on the most important cellulose derivatives. The use of ionic liquids in cellulose processing was recently discovered to not exclusively act as a solvent but also as a reagent. Recent studies showed that bulky chlorides as well as acetyl chloride mixed with ionic liquids can facilitate cellulose acetylation. This work focused on a simple chloro-organic cosolvent, dichloromethane (DCM), and showed the ability of this relatively small molecule, mixed with the ionic liquid, to facilitate homogenous acetylation by displacement of the acetate ion of the ionic liquid with a chloride ion. Maximal acetylation achieved by this method was a degree of substitution (DS) of 1.9, were only a small fraction of DCM was utilized for acetylation, well below even that expected for equimolar reaction. The degree of substitution was controlled by the dichloromethane content, thus controlling its solubility in water. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2458–2462     

芦丁在离子液体双水相中分配性能

建立了室温离子液体四氟硼酸1-丁基-3-甲基咪唑([Bmim]BF4)和NaH2PO4组成的双水相萃取体系并用于对芦丁的萃取分离研究。考察了离子液体用量、芦丁的浓度、盐的加入量、溶液酸度和加入其它物质对芦丁在两相中分配的影响。结果表明,离子液在1.0~2.5 mL,磷酸二氢钠加入量在1.0~2.0 g,加入卢丁溶液0.5~2.5 mL,酸度在pH值为2~7范围,卢丁在离子液体双水相体系中有较高的萃取率(E%>90)。除阳离子表面活性剂外,其余大部分物质不影响相比和卢丁的测定。离子液相中卢丁的最大吸收波长为358 nm,与乙醇水溶液中比较,最大吸收波长发生紫移,表明离子液与卢丁发生了作用。利用离子液体双水相体系,测定了银杏叶中卢丁的含量。