Ion transfer at nanointerfaces between water and neat organic solvents

Nanopipet voltammetry was used for the first study of ion transfer (IT) reactions between aqueous solutions and neat organic solvents. An extremely wide ( approximately 10 V) polarization window obtained with no electrolyte added to the organic phase allows one to probe charge transfer reactions, which are not normally accessible by electrochemical techniques, for example, the transfer of l-alaninamide cation from water to 1,2-dichloroethane (DCE). While anions (e.g., chloride) and relatively hydrophobic cations (e.g., tetraalkylammonium ions) can be transferred from water to less polar neat solvents such as DCE, the transfers of strongly hydrated metal cations occur only in the presence of organic supporting electrolyte.     

Heterogeneous continuous flow synthetic system using cyclohexane-based multiphase electrolyte solutions

The discovery that supporting electrolytes can be effectively confined in typical organic solvents in a c-Hex-based multiphase electrolyte solution has led to the development of a novel heterogeneous continuous flow synthetic system. PTFE fiber functions as a separation filter that can efficiently isolate the c-Hex phase from multiphase electrolyte solutions. This system has demonstrated both electrochemical solvating and carbon-carbon bond forming reactions. Hydrophobic substrates can be introduced into the reactor as c-Hex solutions, which are then electrochemically transformed into the target hydrophobic products that pass through the PTFE fiber as c-Hex solutions.     

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.     

Biphasic recognition chiral extraction — novel way of separating pantoprazole enantiomers

This paper presents a biphasic recognition chiral extraction system developed as a new chiral separation technology for the separation of pantoprazole enantiomers, combining a hydrophilic β-CD derivative in the aqueous phase and a hydrophobic tartaric acid in the organic phase which preferentially recognise the (R)-enantiomer and (S)-enantiomer, respectively. In this study, a number of factors which influence the efficiency of the extraction were investigated including types of organic solvents, β-CD and tartaric acid esters and their concentrations, pH and temperature. As a result, enantioselectivity for pantoprazole enantiomers can be improved up to 1.42 under optimised conditions; in addition, it is clear that the combined action of β-CD and tartaric acid esters leads to formation of the biphasic chiral extraction system with a stronger separation capacity than a monophasic chiral extraction system.     

Stationary and mobile phases in hydrophilic interaction chromatography: a review

Hydrophilic interaction chromatography (HILIC) is valuable alternative to reversed-phase liquid chromatography separations of polar, weakly acidic or basic samples. In principle, this separation mode can be characterized as normal-phase chromatography on polar columns in aqueous-organic mobile phases rich in organic solvents (usually acetonitrile). Highly organic HILIC mobile phases usually enhance ionization in the electrospray ion source of a mass spectrometer, in comparison to mobile phases with higher concentrations of water generally used in reversed-phase (RP) LC separations of polar or ionic compounds, which is another reason for increasing popularity of this technique. Various columns can be used in the HILIC mode for separations of peptides, proteins, oligosaccharides, drugs, metabolites and various natural compounds: bare silica gel, silica-based amino-, amido-, cyano-, carbamate-, diol-, polyol-, zwitterionic sulfobetaine, or poly(2-sulphoethyl aspartamide) and other polar stationary phases chemically bonded on silica gel support, but also ion exchangers or zwitterionic materials showing combined HILIC-ion interaction retention mechanism. Some stationary phases are designed to enhance the mixed-mode retention character. Many polar columns show some contributions of reversed phase (hydrophobic) separation mechanism, depending on the composition of the mobile phase, which can be tuned to suit specific separation problems. Because the separation selectivity in the HILIC mode is complementary to that in reversed-phase and other modes, combinations of the HILIC, RP and other systems are attractive for two-dimensional applications. This review deals with recent advances in the development of HILIC phase separation systems with special attention to the properties of stationary phases. The effects of the mobile phase, of sample structure and of temperature on separation are addressed, too.     

Light‐ and Solvent‐Controlled Self‐Assembly Behavior of Spiropyran–Polyoxometalate–Alkyl Hybrid Molecules

A molecular photochromic spiropyran–polyoxometalate–alkyl organic–inorganic hybrid has been synthesized and fully characterized. The reversible switching of the hydrophobic spiropyran fragment to the hydrophilic merocyanine one can be easily achieved under light irradiation at different wavelengths. This switch changes the amphiphilic feature of the hybrid, leading to a light‐controlled self‐assembly behavior in solution. It has been shown that the hybrid can reversibly self‐assemble into vesicles in polar solvents and irreversibly into reverse vesicles in non‐polar solvents. The sizes of the vesicles and the reverse vesicles are both tunable by the polarity of the solvent, with the hydrophobic interactions being the main driving force.     

Solvent-adaptable silver nanoparticles

A simple and efficient way of obtaining silver nanoparticles that are dispersible both in organic and in aqueous solvents using a single capping agent is described. The silver nanoparticles are initially prepared in water in the presence of aerosol OT [sodium bis(2-ethylhexyl)-sulfosuccinate, AOT]. Thereafter, transfer of the AOT-capped silver nanoparticles to an organic phase is induced by the addition of a small amount of orthophosphoric acid during shaking of the biphasic mixture. The AOT-stabilized silver nanoparticles could be separated out from the organic phase in the form of a powder. The hydrophobic nanoparticles thus prepared are stable and are readily resuspended in a variety of other polar (including water) and nonpolar solvents without further surface treatment. The amphiphatic nature of the silver surface is brought about by a small orientational change in the AOT monolayer on the silver surface in response to the polarity of the solvent.     

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.     

Applications of ethylammonium and propylammonium nitrate solvents in liquid-liquid extraction and chromatography

Ethyl- and propylammonium nitrate are novel ionic solvents, liquid at room temperature, suitable for use as selective solvents for the isolation of analytes containing proton donor functional groups (alcohols, amines, phenols, carboxylic acids, etc.) by liquid-liquid distribution. These solvents form immiscible solvent pairs with non-polar aliphatic and aromatic hydrocarbons, ethers and alkyl halide solvents (e.g., methylene chloride, chloroform). Analytes can be recovered from the ionic solvents by back-extraction into ah organic solvent after dilution with water or pH buffer or, preferably, by extractive derivatization when gas chromatography is used for the analyses, avoiding the accumulation of salt on the column that results in poor baseline stability. Alkylation, acylation and particularly silylation are suitable methods for extractive derivatization using standard reaction conditions. Applications are presented for the isolation of polar analytes from an urban dust, shale oil and urine samples and for the determination of low-molecular-weight alcohols in gasahol and glycerol in soap. Liquid-liquid chromatographic systems with the liquid organic salt as stationary phase can be used to predict distribution constants for a particular separation and for the separation of polar solutes, particularly isomeric compounds possessing a proton donor functional group.     

A liquid–liquid extraction technique for phthalate esters with water-soluble organic solvents by adding inorganic salts

In the presence of inorganic salts, the mixture solution of some water-soluble organic solvents and water can form two clearly separated phases. One is the organic solvent rich phase, the other is the water rich phase. In the phase separation process, hydrophobic solutes dissolved in the mixture solution such as phthalate esters can be extracted into the organic solvent rich phase quantitatively. Based on this phase separation phenomenon, a liquid–liquid extraction technique of phthalate esters using water-soluble organic solvents as organic phases was developed. Several important parameters affecting the extraction efficiency including the kind and the amount of water-soluble organic solvents, the kind and the amount of inorganic salts and the pH of the sample solutions were carefully studied. This new extraction technique has been applied to the HPLC analysis for water lixivium of plastic wrapping film. Under the optimized conditions, detection limits of 1.5, 2.3, 1.0, 2.6, 1.3 and 3.0 ng mL⁻¹ were obtained for diethylphthalate, di-n-propylphthalate, di-iso-butylphthalate, dicyclohexylphthalate, di-n-octylphthalate and di-n-nonylphthalate ester respectively. The strongpoints of this new liquid–liquid extraction technique are the easy phase separation, rapid partition equilibrium, less toxicity and very good compatibility with subsequent HPLC determinations.     

Safer solvents for reactive organometallic reagents

This paper describes the use of poly(α -olefin)s (PAOs) as safer alternatives to cyclohexane, hexanes, and heptane as solvents for alkyllithium reagents. While PAOs like any alkane are flammable, PAOs do not readily catch on fire because they contain 20 or more carbon atoms, a low volatility, and have a high flash point vis-à-vis alkanes like hexane. Also unlike conventional alkanes, PAOs can be quantitatively separated from polar organic solvents and polar organic products either by a simple gravity separation or by an extraction after a reaction. Any leaching of the PAO solvent into a polar phase during such a separation can be minimized by addition of small amounts of water to the polar phase. However, while these PAO solvents have some physical differences from conventional low molecular weight volatile alkanes, they otherwise behave like alkanes and alkyllithium reagents in these PAO solvents can used in their conventional reactions in these PAO solvents.     

The influence of temperature on the phase behavior of ionic liquid aqueous two-phase systems

In this article, the equilibrium behavior of solutions of 1-ethyl-3-methylimidazolium dimethyl phosphate ([Emim]DMP) and ethyl acetate or acetone in aqueous two-phase system (ATPS) was discussed to understand the liquid–liquid equilibrium (LLE) behavior of these organic solvents. Thus, we determined phase diagrams and LLE data at 303.15, 308.15, 313.15, and 323.15 K for the investigated biphasic systems. Four empirical equations were used to study the tie lines. The results showed that for the [Emim]DMP?+?acetone?+?water biphasic systems within the investigated temperature range, temperature influences the phase behavior, but for the [Emim]DMP?+?ethyl acetate?+?water biphasic systems within the investigated temperature range, there are no notable changes on the phase behavior with rising temperature. The results may have important applications for the separation of antibiotics and for the recovery of ionic liquids (ILs).     

Fibrous Networks with Incorporated Macrocycles: A Chiral Stimuli‐Responsive Supramolecular Supergelator and Its Application to Biocatalysis in Organic Media

A new and versatile, crown ether appended, chiral supergelator has been designed and synthesized based on the bis‐urea motif. The introduction of a stereogenic center improved its gelation ability significantly relative to its achiral analogue. This low‐molecular‐weight gelator forms supramolecular gels in a variety of organic solvents. It is sensitive to multiple chemical stimuli and the sol–gel phase transitions can be reversibly triggered by host–guest interactions. The gel can be used to trap enzymes and release them on demand by chemical stimuli. It stabilizes the microparticles in Pickering emulsions so that enzyme‐catalyzed organic reactions can take place in the polar phase inside the microparticles, the organic reactants diffusing through the biphasic interface from the surrounding organic phase. Because of the higher interface area between the organic and polar phases, enzyme activity is enhanced in comparison with simple biphasic systems.     

硅胶色谱柱的亲水作用保留机理及其影响因素

亲水作用色谱（HILIC）是替代反相色谱（RPLC）分离强极性及亲水性化合物的另一色谱模式,其分离机理与RPLC有很大不同,具有和RPLC互补的选择性。在HILIC模式中,采用正相色谱（NPLC）中的极性固定相及含高浓度有机溶剂（通常为乙腈）的水溶液为流动相。硅胶是开发最早、研究最为深入及应用最为广泛的HILIC固定相,本文介绍了硅胶色谱柱的HILIC保留机理,详细概述了操作条件如硅胶柱类型、流动相组成及柱温对HILIC分离的影响,并对硅胶填料色谱柱的HILIC模式的发展方向与应用前景进行了展望。     

Main‐chain viologen polymers with triflimide counterion exhibiting lyotropic liquid‐crystalline properties in polar organic solvents

The solution‐phase behavior of three main‐chain viologen polymers, which are composed of isomeric xylyl units and triflimide as a counterion, was studied in methanol, dimethylformamide, acetonitrile, and dimethyl sulfoxide as solvents microscopically under crossed polarizers. Each of them exhibited a lyotropic lamellar phase in both polar protic and aprotic solvents. Their C^* for the formation of biphasic solutions (1–5 wt %) and concentrations (20–30 wt %) for the lyotropic solutions in methanol was much lower than those in polar aprotic solvents (20–71 and 60–81 wt %, respectively). Their high solubility, high C^* for the formation of biphasic solutions, and high concentrations for the formation of lyotropic solutions in polar aprotic solvents were related to the significant reduction of strong ionic interactions between triflimide and 4,4′‐bipyridinium ions in each of these viologen polymers. They were the first examples of viologen polymers that exhibited a lyotropic phase in polar aprotic solvents. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2015–2024, 2002     

Phase transfer of platinum nanoparticles from aqueous to organic solutions using fatty amine molecules

In this report we demonstrate a simple process based on amine chemistry for the phase transfer of platinum nanoparticles from an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum nanoparticles synthesised in an aqueous medium and octadecylamine (ODA) in hexane. During shaking of the biphasic mixture, the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that is readily redispersible in weakly polar and non-polar organic solvents. The ODA-capped platinum nanoparticles show high catalytic activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR)     

Non-aqueous capillary electrophoresis using non-dissociating solvents. Application to the separation of highly hydrophobic oligomers

The application of non-aqueous capillary electrophoresis for the separation of very hydrophobic oligomers has been studied. N-Phenylaniline oligomers having degrees of polymerisation (n) of 2, 4, 6, and 8 were taken as model compounds. Capillary electrophoresis could be performed using a mixture of non-aqueous solvents with a high percentage of solvents with a low dielectric constant. These solvents, such as tetrahydrofuran (THF), chloroform or dichloromethane, are needed to solubilise the hydrophobic solutes in the electrolyte. The composition of the solvent mixture and the nature of the acid added to the electrolyte, which is needed to obtain electrophoretic motion of the N-phenylaniline oligomers, are discussed in detail. Next, other parameters such as ionic strength, injection time, electric field, and temperature were investigated too and their influence on the separation is discussed as well. The existence of a reversed (anodic) electroosmotic flow in a fused-silica capillary containing a THF-methanol mixture under acidic conditions is reported.     

Ionic Liquids-New "Solutions" for Transition Metal Catalysis

Ionic liquids are salts that are liquid at low temperature (<100 degrees C) which represent a new class of solvents with nonmolecular, ionic character. Even though the first representative has been known since 1914, ionic liquids have only been investigated as solvents for transition metal catalysis in the past ten years. Publications to date show that replacing an organic solvent by an ionic liquid can lead to remarkable improvements in well-known processes. Ionic liquids form biphasic systems with many organic product mixtures. This gives rise to the possibility of a multiphase reaction procedure with easy isolation and recovery of homogeneous catalysts. In addition, ionic liquids have practically no vapor pressure which facilitates product separation by distillation. There are also indications that switching from a normal organic solvent to an ionic liquid can lead to novel and unusual chemical reactivity. This opens up a wide field for future investigations into this new class of solvents in catalytic applications.     

Membraneless energy conversion and storage using immiscible electrolyte solutions

Breakthrough alternative technologies are urgently required to alleviate the critical need to decarbonise our energy supply. We showcase non-conventional approaches to battery and solar energy conversion and storage (ECS) system designs that harness key attributes of immiscible electrolyte solutions, especially the membraneless separation of redox active species and ability to electrify certain liquid–liquid interfaces. We critically evaluate the recent development of membraneless redox flow batteries based on biphasic systems, where one redox couple is confined to an immiscible ionic liquid or organic solvent phase, and the other couple to an aqueous phase. Common to all solar ECS devices are the abilities to harvest light, leading to photo-induced charge carrier separation, and separate the products of the photo-reaction, minimising recombination. We summarise recent progress towards achieving this accepted solar ECS design using immiscible electrolyte solutions in photo-ionic cells, to generate redox fuels, and biphasic “batch” water splitting, to generate solar fuels.     

Screening approach for chiral separation of pharmaceuticals IV. Polar organic solvent chromatography

The aim of this work is to determine generic screening conditions and an initial simple separation strategy allowing the rapid separation of drug enantiomers in polar organic solvent chromatography (POSC). Four cellulose/amylose-based stationary phases were investigated in detail using two mobile phase basis solvents commonly applied in this mode, i.e. acetonitrile and methanol. Polar mode is interesting for use in purification of enantiomers. In a first step, the parameters potentially influencing the separation, such as addition of an alcohol to the polar organic solvent or the type of mobile phase additive(s), were examined by means of experimental designs. Afterwards, the factors found most important are investigated in more detail. Results showed that the cellulose- and amylose-based stationary phases have very broad and complementary enantiorecognition abilities in the POSC mode. The type of organic solvent for the mobile phase appeared to have a dramatic influence on the quality of the separation. Based on the results, a screening strategy was proposed. Enantioseparation was observed in more than 85% of the tested compounds and analysis times of last eluted peak were usually below 10 min.