Comparison of three different dispersive liquid–liquid microextraction modes performed on their most usual configurations for the extraction of phenolic,neutral aromatic,and amino compounds from waters

In this work we seek clues to select the appropriate dispersive liquid–liquid microextraction mode for extracting three categories of compounds. For this purpose, three common dispersive liquid–liquid microextraction modes were compared under optimized conditions. Traditional dispersive liquid–liquid microextraction, in situ ionic liquid dispersive liquid–liquid microextraction, and conventional ionic liquid dispersive liquid–liquid microextraction using chloroform, 1‐butyl‐3‐methylimidazolium tetrafluoroborate, and 1‐hexyl‐3‐methylimidazolium hexafluorophosphate as the extraction solvent, respectively, were considered in this work. Phenolic, neutral aromatic, and amino compounds (each category included six members) were studied as analytes. The analytes in the extracts were determined by high‐performance liquid chromatography with UV detection. For the analytes with polar functionalities, the in situ ionic liquid dispersive liquid–liquid microextraction mode mostly led to better results. In contrast, for neutral hydrocarbons without polar functionalities, traditional dispersive liquid–liquid microextraction using chloroform produced better results. In this case, where dispersion forces were the dominant interactions in the extraction, the refractive index of solvent and analyte predicted the extraction performance better than the octanol/water partition coefficient. It was also revealed that none of the methods were successful in extracting hydrophilic analytes (compounds with the log octanol/water partition coefficient <2). The results of this study could be helpful in selecting a dispersive liquid–liquid microextraction mode for the extraction of various groups of compounds.     

离子液体支撑液膜分离CO2

支撑液膜是一种在湿法冶金、生物技术以及气体分离等多个领域都有应用的重要膜分离技术。本文回顾了支撑液膜技术分离CO2的研究进展,按照液膜相的不同,分类介绍了常规载体支撑液膜和离子液体支撑液膜,指出了常规载体支撑液膜分离CO2的局限性,重点介绍了离子液体支撑液膜分离CO2的发展,分析了气体在离子液体支撑液膜中的传质机理以及常规离子液体结构、含量和支撑膜材料等对分离效果的影响;讨论了离子液体的功能化方法以及功能化离子液体支撑液膜分离CO2的渗透率、选择性和液膜稳定性;介绍了两种新的离子液体支撑液膜改进方法:聚离子液体膜与凝胶化离子液体支撑液膜。最后指出了今后用于CO2分离的离子液体支撑液膜的发展方向。     

液晶二聚体

液晶二聚体作为半柔性主链型液晶聚合物的简化模型, 通过对其液晶性质的研究, 有助于理解更复杂聚合物体系的液晶行为. 另外, 液晶二聚体作为一类特殊的液晶也有其自身的相结构和相行为. 以分子结构与液晶态的相互关系为主线, 系统介绍了目前文献报道的对称及非对称棒状液晶二聚体(线形、H形、U形、T形)、盘状液晶二聚体(对称的盘-盘状液晶二聚体和非对称的盘-棒状液晶二聚体)和香蕉形液晶二聚体(对称的香蕉-香蕉形液晶二聚体和非对称的香蕉-棒状液晶二聚体)等各种不同类型的液晶二聚体的研究进展, 以期为新型液晶二聚体的分子设计提供一些借鉴.     

液/液两相催化新进展--温控非水液/液两相催化

温控非水液/液两相催化,是指一类由两种或多种液态有机物组成的催化反应体系,其特点是体系的相态变化可通过温度来调控,即体系在高温时相互混溶呈均相,低温不溶分成两相,催化剂和产物分别处于两相,从而为解决均相催化剂分离难的问题开拓了一个新方向,是液/液两相催化研究领域最引人注目的进展之一.首次以"温控"为主线将氟两相催化作为温控液/液两相催化的一个特定类型纳入"温控非水液/液两相催化"范畴,并与其它通过温度来调控的有机液/液两相和作者提出的温控相分离催化串在一起作一较为详细的评述.     

几类非常规液晶材料的研究进展

本文综述了液晶二聚体、多爪型液晶及香蕉形液晶等几类非常规液晶材料的研究进展。结合笔者近几年的研究积累,着重介绍:(1)液晶二聚体的分子结构与液晶态结构及液晶二聚体所特有的奇偶效应与近晶多形性;(2)多爪型液晶的分子结构与液晶态结构的特点及由于兼有棒状分子与盘状分子的结构特点而具备的特殊的相变性质;(3)香蕉形液晶的分子结构与液晶态结构及香蕉形液晶所特有的手性与极化序。在介绍各类液晶材料的特点及研究热点的同时,围绕分子结构与液晶态结构的关系这一主题,深入讨论了各种液晶材料形成特殊分子排列及表现出特殊物理性质的机理。     

Polymer-Metal Nanoparticle Complexes for Improving the Performance of Liquid Crystal Displays

Summary: Here we applied metal nanoparticles as a dopant of liquid crystals. Since liquid crystal molecules are self-assembled, it is not so easy to disperse metal nanoparticles in liquid crystal media. We first prepared metal nanoparticles protected by liquid crystal molecules by reduction of metal ions in the presence of liquid crystal molecules. This liquid crystal molecule-protected metal nanoparticles can be easily dispersed in liquid crystal media to fabricate liquid crystal sol containing metal nanoparticles. A simple liquid crystal molecule, 4′-pentylbiphenyl-4-carbonitrile (abbreviated as 5CB) was used in the present experiments at first. 5CB sol containing metal nanoparticles could construct novel twisted nematic liquid crystal devices (TN-LCDs), which revealed the electrooptic properties depending on the kind of metal of nanoparticles. During the experiments we discovered that 5CB-protected metal nanoparticles could move in liquid crystal media by applying the voltage. This phenomenon is inconvenient for liquid crystal displays, especially those driven by a matrix of thin-film transistors (TFTs). In order to avoid this phenomenon, we prepared polymer-protected metal nanoparticles and applied them to liquid crystal devices, which provided good performance as the devices, i.e., low driving voltage, rapid response at low temperature, and so on.     

羊睾丸,梅花鹿胎盘提取液中铅的测定

利用火焰原子吸收法直接测定羊睾丸，梅花鹿胎盘提取液中铅的含量，实验结果表明，两种提以液中均含有铅，梅花鹿胎盘提取液铅含量低于羊睾丸，透析液组高于超滤液组，这一结果为合理开发利用羊睾丸，梅花鹿胎盘提取液提供一定的数据。     

An experimental study of three- and four-phase equilibria for isopropanol—water—carbon dioxide mixtures at elevated pressures

Compositions and molar volumes of the three phases in liquid—liquid—gas equilibrium are reported for ternary mixtures of isopropanol, water and CO₂ at elevated pressures and at temperatures of 50 and 60°C. Phase compositions and molar volumes were also obtained for three-phase, liquid—liquid—liquid equilibrium and four-phase, liquid—liquid—liquid—gas equilibrium at 40°C. Gas—liquid and liquid—liquid critical endpoints, which represent pressure bounds on the liquid—liquid—gas region at 60°C, were determined from observations of critical opalescence.The phase behavior exhibited by the isopropanol—water—CO₂ system is quite complex, particularly at conditions near the critical point of CO₂. These conditions are well within the range of operating conditions proposed for supercritical-fluid extraction of organic compounds from water using CO₂. Therefore, the existence of multiple coexisting phases can be an important factor in designing and operating such extraction processes.     

Electrochemistry at micro- and nanoscopic liquid/liquid interfaces

In this tutorial review, we will briefly introduce the history and basic concepts of micro- and nanoscopic liquid/liquid interfaces (size from nm to μm) in electrochemical studies of charge (electron and ion) transfer reactions at soft molecular interfaces. Their advantages and problems are usually compared with those of conventional liquid/liquid interfaces (size from mm to cm); and with solid/electrolyte interfaces. Three methods of fabrication of micro-liquid/liquid interfaces and one approach to support a nano-liquid/liquid interface are surveyed. The experimental and theoretical aspects are discussed along with possible approaches to characterize these micro- and nanoscopic liquid/liquid interfaces, and the methods to modify them with new functionality. Unique examples of applications of electrochemistry at micro- and nanoscopic liquid/liquid interfaces are provided. Some novel and potential research interests in the future in this field are discussed.     

含氟液晶研究进展

本文简述了含氟液晶的研究进展。根据小分子含氟液晶中氟原子或含氟基团的位置不同,将其分为3类：末端是氟原子或含氟基团的液晶、苯环上氢原子被氟原子取代的液晶、中心桥键上的氢原子被氟原子取代的液晶。根据小分子含氟液晶特点,归纳了氟原子或含氟基团对液晶分子物理性质的影响。同时对高分子含氟液晶的研究进展也做了介绍。     

Copolymerizable initiator for improved polymer dispersed liquid crystal films

The problems of photoinitiator contamination are addressed for the liquid crystal phase in polymer dispersed liquid crystal films formed by photopolymerization induced phase separation of liquid crystal from monomer solutions. Initiator contamination lowers the clearing point of the liquid crystal phase, and decreases the photostability and resistivity of the polymer dispersed liquid crystal. These problems are minimized by replacing the conventional photoinitiators with copolymerizable initiators which become incorporated in the polymer phase as it separates. Copolymerizable photoinitiators are studied and used to form polymer dispersed liquid crystals with higher clearing point liquid crystal phases, higher resistivity, and better photostability than polymer dispersed liquid crystals formed with conventional photoinitiators. These improvements provide very significant advantages for many polymer dispersed liquid crystal applications.     

Liquid crystal effects on bacterial viability

The primary objective of this research was to test the hypothesis that lyotropic chromonic liquid crystals (neutral grey, red 14, blue 27, cromolyn) are not toxic to bacteria as compared with surfactant-based lyotropic (CPCl and CsPFO) or thermotropic (5CB and E7) liquid crystals. Biocompatibility of most liquid crystals is currently unknown and is required for the development of systems interfacing liquid crystals and biological systems. Potential liquid crystal toxicity was evaluated by two methods. The first examined bacterial survival measured by bacterial growth over 24 hours, after exposure to various liquid crystals. The second toxicity method evaluated liquid crystal effects on bacterial membrane permeability using two fluorescent dyes. Three different types of bacteria were evaluated to assess bacterial structure differences with respect to liquid crystal toxicity. The results of this study indicate that lyotropic chromonic liquid crystals are not toxic to bacteria, whereas thermotropic and surfactant-based lyotropic liquid crystals are toxic to one or more forms of bacteria. We conclude that lyotropic chromonic liquid crystals may be the preferred material in designing liquid crystal-based systems that interact with biological systems, especially in the use of liquid crystal-based biosensors.     

Recent analytical methodologies on equilibrium, kinetics, and dynamics at liquid/liquid interface

The form of liquid/liquid interface is flexible and it cannot be fixed at a spatial position. Also the interface is prevented from any physical contact by the organic phase and aqueous phase. In addition, analytical methods operated in vacuo cannot be applied. These restrictions depressed the development of liquid/liquid interfacial chemistry. However, the modification of liquid/liquid interfacial form and original analytical methods have been invented interdependently. The present review classifies the forms of liquid/liquid interface first, and it arrays the related analytical methods with brief explanations. It dominantly deals with recent reports of analytical methodologies, which were published in 2001-2004, on equilibrium, kinetics, and dynamics of substances at liquid/liquid interface, but it also includes historically important studies.     

Copolymerizable initiator for improved polymer dispersed liquid crystal films

Abstract

The problems of photoinitiator contamination are addressed for the liquid crystal phase in polymer dispersed liquid crystal films formed by photopolymerization induced phase separation of liquid crystal from monomer solutions. Initiator contamination lowers the clearing point of the liquid crystal phase, and decreases the photostability and resistivity of the polymer dispersed liquid crystal. These problems are minimized by replacing the conventional photoinitiators with copolymerizable initiators which become incorporated in the polymer phase as it separates. Copolymerizable photoinitiators are studied and used to form polymer dispersed liquid crystals with higher clearing point liquid crystal phases, higher resistivity, and better photostability than polymer dispersed liquid crystals formed with conventional photoinitiators. These improvements provide very significant advantages for many polymer dispersed liquid crystal applications.     

Study of mass transfer enhancement on liquid/liquid interface by flow instabilities using gallium liquid electrode

Abstrac  Using liquid gallium electrodes it was proved that electrodiffusion method is a convenient tool for measuring the mass transfer at liquid/liquid interface. It was shown that mass transfer coefficient at the liquid/liquid interface at high Reynolds numbers is much more important in comparison to that measured at the solid/liquid interface at identical geometrical and hydrodynamic conditions. In experiments with the flow induced by the rotation of the upper disc (working ring electrode is placed on the bottom of the immobile disc), the Sherwood number increases in turbulent regime as Sh ∼ Re^1.8 at the liquid/liquid interface, contrary to the traditional law Sh ∼ Re^0.9 at the solid/liquid interface. In laminar regime the Sherwood number at the liquid/liquid and at the solid/liquid interfaces follows the traditional dependence Sh ∼ Re^0.5. It was shown that sharp increasing of the mass transfer coefficient at the liquid/liquid interface is closely related with the appearance of the surface waves, the phenomenon is identified as a Kelvin-Helmholtz type instability. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 4, pp. 482–490. The text was submitted by the authors in English.     

Liquid crystal effects on bacterial viability

The primary objective of this research was to test the hypothesis that lyotropic chromonic liquid crystals (neutral grey, red 14, blue 27, cromolyn) are not toxic to bacteria as compared with surfactant‐based lyotropic (CPCl and CsPFO) or thermotropic (5CB and E7) liquid crystals. Biocompatibility of most liquid crystals is currently unknown and is required for the development of systems interfacing liquid crystals and biological systems. Potential liquid crystal toxicity was evaluated by two methods. The first examined bacterial survival measured by bacterial growth over 24 hours, after exposure to various liquid crystals. The second toxicity method evaluated liquid crystal effects on bacterial membrane permeability using two fluorescent dyes. Three different types of bacteria were evaluated to assess bacterial structure differences with respect to liquid crystal toxicity. The results of this study indicate that lyotropic chromonic liquid crystals are not toxic to bacteria, whereas thermotropic and surfactant‐based lyotropic liquid crystals are toxic to one or more forms of bacteria. We conclude that lyotropic chromonic liquid crystals may be the preferred material in designing liquid crystal‐based systems that interact with biological systems, especially in the use of liquid crystal‐based biosensors.     

Fast quantitative determination of platinum in liquid samples by laser-induced breakdown spectroscopy

The potential of laser-induced breakdown spectroscopy (LIBS) for the rapid determination of platinum in liquid silicone oils has been evaluated in the framework of on-line process control. A comparison of LIBS sensitivity between three setups designed for liquid analysis (static, liquid jet and flowing liquid) was performed using a 266 nm Nd/YAG laser irradiation. Best results were obtained using the flowing liquid setup and a similar limit of detection was obtained using the liquid jet. The effect of different buffer gases (Ar, He, N(2), etc.) on the signal sensitivity was studied in liquid jet analysis and best values were obtained with a nitrogen sheath gas. Detection limits were in the 100 mg/kg range for both setups. Quantitative determination of platinum in real liquid samples was also investigated using both liquid jet and flowing liquid setups. Calibration curves were plotted for Pt with the liquid jet and the flowing liquid setups under optimised temporal acquisition parameters (delay time and gate width). A normalisation using a silicon line was applied and recovery ranged from 3 to 15% for Pt in catalyst samples with both setups showing that LIBS is a sensitive and accurate method for on-line applications.     

Phase behavior of polylactides in solvent–nonsolvent mixtures

Isothermal phase diagrams for the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA) in combination with several solvent–nonsolvent combinations (dioxane/water, dioxane/methanol, chloroform/methanol, and NMP/water) have been determined. The locations of the liquid–liquid miscibility gap, the solid–liquid miscibility gap and the vitrification boundary in the isothermal phase diagrams at 25°C were identified. The liquid–liquid miscibility gap for the systems with PLLA was located in the same composition range as the corresponding systems with PDLLA. For the systems containing PLLA solid–liquid demixing was thermodynamically preferred over liquid–liquid demixing. Attempts were made to correlate the experimental findings with predictions on the basis of the Flory-Huggins theory for ternary solutions using interaction parameters derived from independent experiments. Qualitative agreement was found between the theoretical predictions and the experimentally obtained liquid–liquid miscibility gap. No good agreement was found for the solid–liquid miscibility gap. © 1996 John Wiley & Sons, Inc.     

Liquid—liquid equilibrium data: Their retrieval,correlation and prediction Part II: Correlation

The correlation of liquid—liquid equilibrium data using models for the liquid phase activity coefficients — for example NRTL and UNIQUAC — is reviewed. Different numerical procedures used in the computation of liquid—liquid equilibrium compositions on the basis of these models are evaluated. Methods for obtaining parameters from liquid—liquid equilibrium data are described, and a method leading to improved representation of tie lines using relatively few parameters is recommended. The NRTL and UNIQUAC equations are compared with respect to their ability of representing binary and ternary liquid—liquid equilibrium data. The UNIQUAC equation appears to be more convenient to use and to correlate the data slightly better than does NRTL with the same number of parameters.     

Microtubule particle dispersion in liquid crystal hosts

Microtubule particles and metal-coated microtubules were dispersed in various host liquid crystal mixtures. Dispersion effects were evaluated as a function of liquid crystal type, viscosity, dielectric anisotropy and surface interaction. Experimental results indicated that all the types of liquid crystals studied were aligned perpendicular to the microtubule surfaces, regardless of liquid crystal composition or various surface coatings used on the metal-coated microtubules. Low concentrations of the metal-coated microtubules in nematic liquid crystal hosts were aligned by flow or cell surface alignment conditions, and could be modulated by electric or magnetic fields. We observed better microtubules dispersion uniformity in high viscosity liquid crystal host mixtures and in liquid crystal-monomers than in isotropic fluids. Microtubules particles dispersed in ROTN-404 liquid crystal mixture had a much higher birefringence in the microwave region than dispersion in a paraffin oil.