Application of ionic liquid in liquid phase microextraction technology

Ionic liquids (ILs) are novel nonmolecular solvents. Their unique properties, such as high thermal stability, tunable viscosity, negligible vapor pressure, nonflammability, and good solubility for inorganic and organic compounds, make them excellent candidates as extraction media for a range of microextraction techniques. Many physical properties of ILs can be varied, and the structural design can be tuned to impart the desired functionality and enhance the analyte extraction selectivity, efficiency, and sensitivity. This paper provides an overview of the applications of ILs in liquid phase microextraction technology, such as single‐drop microextraction, hollow fiber based liquid phase microextraction, and dispersive liquid–liquid microextraction. The sensitivity, linear calibration range, and detection limits for a range of target analytes in the methods were analyzed to determine the advantages of ILs in liquid phase microextraction.     

Ionic liquids as a tool for determination of metals and organic compounds in food analysis

Ionic liquids (ILs) are non-molecular solvents, which are mainly characterized as possessing low melting points, low-to-negligible vapor pressures, and high thermal stability. Their unique solvation properties, coupled to the fact that they can be structurally tailored for specific applications, have increased study of ILs in many areas of fundamental and applied chemistry. Thus, ILs have successfully been utilized as novel solvents in different extraction and microextraction schemes in recent years, but mainly with environmental samples.Food samples are quite complicated matrices from an analytical point of view. They contain a large range of chemical substances, and sometimes they also have a high fat content. Even with the most advanced analytical techniques, food sampling and food-sample preparation prior to the analytical determination are labor-intensive and time-consuming, and normally require relatively large amounts of organic solvents.In this review, we summarize the most recent analytical developments aimed at employing ILs as a tool in food analysis. We discuss practical applications to determine metals and organic compounds in food samples of quite different natures, with special emphasis to the extraction step at which the IL is introduced, and the advantages of the IL-based methods developed over conventional extraction methods.     

Ionic liquids in sample preparation

Due to their unique properties, their good extractabilities for various target analytes, and the fact that many compounds are highly soluble in them, room-temperature ionic liquids (ILs) are used as promising alternatives to the traditional organic solvents employed in sample preparation. ILs have been used as extraction solvents for a wide range of analytes, from environmental contaminates to biomacromolecules and nanomaterials, and as dissolution solvents for various detection techniques. In this paper, the main applications of ILs in sample preparation are reviewed, and the problems and challenges in this area are described.     

Bioanalytical separation and preconcentration using ionic liquids

Ionic liquids (ILs) are novel solvents that display a number of unique properties, such as negligible vapor pressure, thermal stability (even at high temperatures), favorable viscosity, and miscibility with water and organic solvents. These properties make them attractive alternatives to environmentally unfriendly solvents that produce volatile organic compounds. In this article, a critical review of state-of-the-art developments in the use of ILs for the separation and preconcentration of bioanalytes in biological samples is presented. Special attention is paid to the determination of various organic and inorganic analytes—including contaminants (e.g., pesticides, nicotine, opioids, gold, arsenic, lead, etc.) and functional biomolecules (e.g., testosterone, vitamin B₁₂, hemoglobin)—in urine, blood, saliva, hair, and nail samples. A brief introduction to modern microextraction techniques based on ILs, such as dispersive liquid–liquid microextraction (DLLME) and single-drop microextraction (SDME), is provided. A comparison of IL-based methods in terms of their limits of detection and environmental compatibilities is also made. Finally, critical issues and challenges that have arisen from the use of ILs in separation and preconcentration techniques are also discussed.

Ionic liquids: solvents and sorbents in sample preparation

The applications of ionic liquids (ILs) and IL‐derived sorbents are rapidly expanding. By careful selection of the cation and anion components, the physicochemical properties of ILs can be altered to meet the requirements of specific applications. Reports of IL solvents possessing high selectivity for specific analytes are numerous and continue to motivate the development of new IL‐based sample preparation methods that are faster, more selective, and environmentally benign compared to conventional organic solvents. The advantages of ILs have also been exploited in solid/polymer formats in which ordinarily nonspecific sorbents are functionalized with IL moieties in order to impart selectivity for an analyte or analyte class. Furthermore, new ILs that incorporate a paramagnetic component into the IL structure, known as magnetic ionic liquids (MILs), have emerged as useful solvents for bioanalytical applications. In this rapidly changing field, this Review focuses on the applications of ILs and IL‐based sorbents in sample preparation with a special emphasis on liquid phase extraction techniques using ILs and MILs, IL‐based solid‐phase extraction, ILs in mass spectrometry, and biological applications.     

Determination of ethanol in ionic liquids using headspace solid-phase microextraction–gas chromatography

The application of ionic liquids (ILs) as nonderivatizing solvents for the pretreatment and regeneration of cellulose is a growing area of research. Here we report the development of a rapid and simple method for the determination of residual ethanol content in two hydrophilic ILs, 1-butyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium acetate. The method utilizes headspace solid-phase microextraction coupled with gas chromatography at elevated extraction temperatures, resulting in rapid equilibration times. The effect of IL water content on the ethanol extraction efficiency is presented. Recovery experiments carried out in real samples gave recoveries ranging from 96.8 to 98.2%.     

Liquid phase microextraction of pesticides: a review on current methods

Liquid phase microextraction (LPME) enables analytes to be extracted with a few microliters of an organic solvent. LPME is a technique for sample preparation that is extremely simple, affordable and virtually a solvent-free. It can provide a high degree of selectivity and enrichment by eliminating carry-over between single runs. A variety of solvents are known for the extraction of the various analytes. These features have led to the development of techniques such as single drop microextraction, hollow fiber LPME, dispersive liquid-liquid microextraction, and others. LPME techniques have been applied to the analysis of pharmaceuticals, food, beverages, and pesticides. This review covers the history of LPME methods, and then gives a comprehensive collection of their application to the preconcentration and determination of pesticides in various matrices. Specific sections cover (a) sample treatment techniques in general, (b) single-drop microextraction, (c) extraction based on the use of ionic liquids, (d) solidified floating organic drop microextraction, and various other techniques. Contains 149 references.

Modified-cold induced aggregation microextraction based on ionic liquid and fibre optic-linear array detection spectrophotometric determination of palladium in saline solutions

In this research, a novel microextraction technique based on ionic liquids (ILs) termed in modified-cold induced aggregation microextraction (M-CIAME) was used for determination of palladium in saline solution. 1-(2-pyridylazo)-2-naphtol (PAN) was chosen as the complexing agent. Analysis was carried out using fibre optic-linear array detection spectrophotometric method which is suitable for analyte determination after microextraction. M-CIAME is based on phase separation phenomenon of ionic liquids in aqueous solutions. This method is simple and rapid for extraction and preconcentration of metal ions from water samples. It can be applied for the sample solutions containing much higher concentrations of salt, in comparison with CIAME (cold induced aggregation microextraction). Furthermore, this technique is much safer in comparison with other microextraction techniques in which organic solvent is used as the extraction solvent. Some effective parameters on extraction and complex formation such as amount of IL, salt effect, pH, concentration of the chelating agent and the other parameters were optimised. Under the optimum conditions, the limit of detection (LOD) and repeatability, expressed as relative standard deviation (n?=?5) for 20?ng?mL^?1 of palladium were 0.4?ng?mL^?1 and 2.23%, respectively. The extraction percentage was 86%.     

Amide-Based Ionic Liquid Electrolytes for Alkali-Metal-Ion Rechargeable Batteries

Ionic liquids (ILs) have a wide variety of applications in energy storage and material production. ILs are composed of only cations and anions, without any molecular solvents, and are generally known as “designer liquids (solvents)” because their physicochemical properties can be tuned by the combination of ionic species. In recent several decades, research and development activities of rechargeable batteries have garnered considerable attention because certain groups of ILs exhibit high electrochemical stability and moderate ionic conductivity, rendering them suitable for application in high-voltage batteries. ILs with amide anions are representative electrolytes and are extensively researched by many research groups, including our group. This paper focuses on amide-based ILs as electrolytes for alkali-metal-ion rechargeable batteries, introducing their history, characteristics, and existing challenges to be addressed.     

Screening the extractability of some typical environmental pollutants by ionic liquids in liquid-phase microextraction

The extractability of some typical environmental pollutants in ionic liquids (ILs) was screened by using a simple one-step liquid phase microextraction procedure. It was demonstrated that 1-alkyl-3-methylimidazolium hexafluorophosphate ([CnMIM][PF6], n = 4, 8), two typical ILs, could effectively extract a set of 45 typical environmental pollutants including BTEX (benzene, toluene, ethylbenzene, and xylene), polycyclic aromatic hydrocarbons, phthalates, phenols, aromatic amines, herbicides, organotin, and organomecury. Analytes in 10 mL sample solution held in a 15 mL vial were extracted by a 5 microL drop of ILs suspended on the needle of a high-performance liquid chromatography (HPLC) microsyringe; this was followed by HPLC, atomic absorption spectrometry, or cold-vapor atomic fluorescence spectrometry determination. The enrichment factors determined were in the range of 5-168 for 15 min extraction by [C4MIM][PF6] and 4-178 for 30 min extraction by [C8MIM][PF6], respectively, which indicates that ILs might be considered as potential environmentally benign alternative recyclable solvents for the enrichment of environmental pollutants.     

基于低共熔溶剂的萃取分离技术及其应用研究进展

随着绿色化学的发展,开发和应用符合绿色化学要求的溶剂和方法备受关注。作为离子液体类似物,低共熔溶剂(deep eutectic solvent, DES)是通过氢键受体(hydrogen bond acceptor, HBA)和氢键供体(hydrogen bond donator, HBD)的氢键作用而形成的一种混合物,具有环境友好、制备简单、成本低、可生物降解等优点,在很多领域均有越来越广泛的应用。DES可以从不同样品中萃取和分离不同的目标化合物,其作为萃取溶剂具有独特的优势,可以获得较高的萃取效率且样品基质对分析过程的影响较小。在分散液液微萃取(dispersive liquid-liquid micro-extraction, DLLME)程序中,DES可以萃取复杂基质中的残留药物、金属离子和生物活性成分;与传统的萃取方法相比,该方法具有对有机试剂需求少,萃取效率更高等明显优势。而且,在DLLME中加入DES作为分散剂,能够加速萃取剂在样品溶液中的扩散,具有小型化、成本低等优点。相比于传统分散剂甲醇、乙腈的高挥发性、易燃性,DES的高稳定性、低毒性使其在绿色化学领域中更具有优势,应用更广。因此,DES与DLLME的结合近年来发展迅速。不仅如此,DES与固相萃取联合应用也具有广泛的应用前景,在与固相萃取小柱和搅拌棒联合应用时,DES可以作为洗脱剂,氢键供体及氢键给体的用量之比是洗脱效率的重要考察因素之一。在与磁性材料联用时,DES能与磁性多壁碳纳米管、磁性氧化石墨烯等纳米复合材料结合,通过氢键、π-π作用力和静电作用力等特异性吸附目标分析物。并且能够参与磁性凝胶和分子印迹聚合物的合成,推动磁性材料向绿色化学的方向发展,进一步拓展DES的应用。作为一类新兴的绿色溶剂,DES在化合物的萃取分离技术方面受到广泛关注,在不同的萃取技术中扮演了不同的角色,并表现出良好的性能,因此逐渐成为绿色化学领域的研究重点。该文整合了DES在萃取分离技术中的研究进展,介绍了DES的制备、性质和分类,对DES在DLLME和固相萃取中的应用进行了总结和归类,并展望了DES在萃取分离技术中的应用前景,为DES未来的应用提供参考。     

冠醚-离子液体体系对水相中锶离子的萃取研究

本文研究了以一系列离子液体作为介质时,萃取剂二环己基18冠6（DCH18C6）对水相中Sr^2＋的萃取行为．研究结果表明,DCH18C6／离子液体体系对Sr^2＋的萃取性能优于相应的DCH18C6／JE辛醇萃取体系,一定条件下其萃取Sr^2＋的分配比可达10^3量级．同时,体系对Sr^2＋的萃取性能随着离子液体的结构不同而有所差别．在离子液体萃取体系中,随着水相初始硝酸浓度的增加,对Sr^2＋的萃取性能下降．水相中Na^＋、K^＋等离子的存在也会对体系萃取Sr^2＋产生直接影响．本文还验证了离子液体体系萃取Sr^2＋的机理,即以阳离子交换机理为主实现对Sr^2＋的萃取．     

Extraction of organic compounds with room temperature ionic liquids

Room temperature ionic liquids are novel solvents with a rather specific blend of physical and solution properties that makes them of interest for applications in separation science. They are good solvents for a wide range of compounds in which they behave as polar solvents. Their physical properties of note that distinguish them from conventional organic solvents are a negligible vapor pressure, high thermal stability, and relatively high viscosity. They can form biphasic systems with water or low polarity organic solvents and gases suitable for use in liquid–liquid and gas–liquid partition systems. An analysis of partition coefficients for varied compounds in these systems allows characterization of solvent selectivity using the solvation parameter model, which together with spectroscopic studies of solvent effects on probe substances, results in a detailed picture of solvent behavior. These studies indicate that the solution properties of ionic liquids are similar to those of polar organic solvents. Practical applications of ionic liquids in sample preparation include extractive distillation, aqueous biphasic systems, liquid–liquid extraction, liquid-phase microextraction, supported liquid membrane extraction, matrix solvents for headspace analysis, and micellar extraction. The specific advantages and limitations of ionic liquids in these studies is discussed with a view to defining future uses and the need not to neglect the identification of new room temperature ionic liquids with physical and solution properties tailored to the needs of specific sample preparation techniques. The defining feature of the special nature of ionic liquids is not their solution or physical properties viewed separately but their unique combinations when taken together compared with traditional organic solvents.     

离子液体吸收分离SO2

离子液体具有极低的挥发性、良好的热稳定性和化学稳定性以及结构性质可调等特点,被认为是一种环境友好的溶剂。由于其结构性质可调,可以设计合成出对SO₂有较高溶解能力和选择性的离子液体,在SO₂的吸收和分离领域得到了研究者的青睐。本文综述了各种用于分离捕集烟气和混合气体中SO₂的离子液体,介绍了它们的结构特点、吸收特性和强化方法,探讨了离子液体脱硫的相关机理,最后对离子液体吸收分离SO₂中存在的问题、发展方向和应用前景进行了论述。     

Analytical developments and applications of ionic liquids for environmental studies

Ionic liquids (ILs) are considered advanced solvents with interesting properties that have led to remarkable improvements in the performance of analytical methods and their practical application. Analytical chemistry has profited from the evolution of ILs in diverse contexts, ranging from their applications in microextractions to uses as matrices for mass spectrometric determinations. Their use in sample preparation has meant significant improvements in terms of miniaturization and analytical performance, and given place to new techniques based on liquid-liquid and solid-phase extractions; the latter greatly driven forward by the combination of ILs with nanomaterials. Furthermore, electrodes have been prepared by combining ILs with different modern materials, significantly improving the sensitivity and selectivity of electroanalytical methods. Moreover, the implementation of ILs as additives to mobile and stationary phases in separation techniques has been proved to improve liquid and gas chromatography, as well as capillary electrophoresis, in terms of the number of analytes that can be efficiently separated and of the useful life of columns, representing also a promising alternative to environmentally dangerous organic solvents. Additionally, their application as matrix modifiers and as ion-pairing additives has introduced their use in mass spectrometry. In this review, the design and implementation of innovative and highly efficient analytical methods based on ILs for the sensitive and selective determination of diverse analytes in environmental matrices is described. Critical issues that have arisen from their application and future challenges in electrochemical, separation and preconcentration techniques based on these solvents are also presented.     

核磁共振波谱技术在室温离子液体研究中的应用*

室温离子液体作为一种绿色溶剂和功能材料,越来越引起人们的重视,其研究手段也越来越多。本文着重概述了核磁共振方法在测定离子液体的结构、纯度及性质,研究离子液体阴阳离子间的相互作用、离子液体与其他化合物的相互作用、离子液体及其在混合体系中的动力学特征、离子液体在溶液中的聚集行为,以及测定离子液体的热力学参数中的应用。     

Natural deep eutectic solvents as new potential media for green technology

Developing new green solvents is one of the key subjects in Green Chemistry. Ionic liquids (ILs) and deep eutectic solvents, thus, have been paid great attention to replace current harsh organic solvents and have been applied to many chemical processing such as extraction and synthesis. However, current ionic liquids and deep eutectic solvents have still limitations to be applied to a real chemical industry due to toxicity against human and environment and high cost of ILs and solid state of most deep eutectic solvents at room temperature. Recently we discovered that many plant abundant primary metabolites changed their state from solid to liquid when they were mixed in proper ratio. This finding made us hypothesize that natural deep eutectic solvents (NADES) play a role as alternative media to water in living organisms and tested a wide range of natural products, which resulted in discovery of over 100 NADES from nature. In order to prove deep eutectic feature the interaction between the molecules was investigated by nuclear magnetic resonance spectroscopy. All the tested NADES show clear hydrogen bonding between components. As next step physical properties of NADES such as water activity, density, viscosity, polarity and thermal properties were measured as well as the effect of water on the physical properties. In the last stage the novel NADES were applied to the solubilization of wide range of biomolecules such as non-water soluble bioactive natural products, gluten, starch, and DNA. In most cases the solubility of the biomolecules evaluated in this study was greatly higher than water. Based on the results the novel NADES may be expected as potential green solvents at room temperature in diverse fields of chemistry.     

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

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

离子液体表/界面性质与结构

离子液体与气体、溶剂等物质组成的多相体系为吸收、萃取、两相催化等技术的发展提供了新的平台。离子液体的表/界面性质与结构是含离子液体多相体系的重要科学问题,可在介观尺度下显著影响多相体系反应和分离过程的效率。近年来,离子液体表/界面性质和结构的研究得到了广泛的关注。本文综述了离子液体及其与水、有机溶剂组成的混合物的表/界面张力及结构研究进展,介绍了现有的研究方法、研究对象与研究成果,归纳了离子液体及其混合物表/界面张力及结构的变化规律,分析了表/界面结构与表/界面张力之间的关系,探讨了离子液体表/界面研究存在的问题和未来的发展方向。     

A Review of Ionic Liquids in Chromatographic and Electromigration Techniques

Although there have been numerous studies on the use of ionic liquids (IL) as solvents for synthesis and catalysis, there are many potential new fields for their application. The number of studies dealing with the use of ILs as additives to the mobile phase in LC and CZE and as a stationary phases in GC is constantly increasing. The main goal of the present paper is to gather together studies concerning the use of ILs in chromatographic techniques. The application of these substances as stationary phases, mobile phase additives and electroosmotic flow modifiers is discussed. Conversely, the application of separation methods in the analysis of ILs is also the subject of this review.