Liquid–Liquid Equilibrium of Water + 1-Butanol + Inorganic Salt Systems at 303.15, 313.15 and 323.15 K: Experiments and Correlation

Liquid–liquid equilibria (LLE) and tie-line data of systems containing 1-butanol, water and NaCl, Na₂SO₄, NH₄Cl or (NH₄)₂SO₄ were investigated at 303.15, 313.15 and 323.15 K and atmospheric pressure. The salt decreases mutual solubilities of these two solvents leading to a higher degree of phase separation at equilibrium. The effect is more pronounced at high salt concentration. Temperature in the studied range had a minor effect on LLE behavior of these mixtures. Experimental data were correlated using a modified extended UNIQUAC model. Satisfactory agreement between the calculated and measured mass fractions of the components was achieved.     

Liquid–Liquid Equilibria of the Methanol + Ethylbenzene + Methylcyclohexane Ternary System at 278.15, 283.15, and 293.15 K

Liquid–liquid equilibria of the methanol + ethylbenzene + methylcyclohexane ternary system are reported at 278.15, 283.15, and 293.15 K. The effect of the temperature on the liquid–liquid equilibrium is discussed. All chemical concentrations were quantified by gas chromatography using a thermal conductivity detector. Experimental data for the ternary system are compared with values calculated by the NRTL and UNIQUAC equations. It was found that both equations gave comparable quality representations of the experimental data for this ternary system. Distribution curves were also analyzed. Data for the ternary system is available from the literature at 303.15 K.     

Solid–Liquid Equilibrium for the Ternary System 2-Methyl-4-Nitroaniline + 2-Methyl-6-Nitroaniline + Ethyl Acetate: Determination and Modelling

The solid–liquid phase equilibria for the ternary system 2-methyl-4-nitroaniline + 2-methyl-6-nitroaniline + ethyl acetate was determined experimentally by the method of isothermal solution saturation at temperatures of (293.15, 303.15 and 313.15) K under the pressure of 101.2 kPa. Based on the obtained solubility data, the isothermal phase diagrams of the system were constructed. At each temperature, there are two pure solid phases formed, which correspond to pure 2-methyl-4-nitroaniline and pure 2-methyl-6-nitroaniline, which was confirmed by Schreinemakers’ wet residue method and X-ray powder diffraction. The crystallization regions of pure 2-methyl-4-nitroaniline and pure 2-methyl-6-nitroaniline increased with decreasing temperature. The crystalline region of 2-methyl-4-nitroaniline was larger than that of 2-methyl-6-nitroaniline at a fixed temperature. The solubility data were correlated with the NRTL and Wilson models. The values of the root-mean-square deviations are 5.01 × 10^?3 for the NRTL model, and 6.43 × 10^?3 for the Wilson model. The solid–liquid equilibria, phase diagrams and the thermodynamic models for the ternary system can provide the foundation for separating 2-methyl-6-nitroaniline or 2-methyl-4-nitroaniline from its mixtures.     

Quinary Mutual Diffusion Coefficients of Aqueous Mannitol + Glycine + Urea + KCl and Aqueous Tetrabutylammonium Chloride + LiCl + KCl + HCl Solutions Measured by Taylor Dispersion

Taylor dispersion is widely used to measure binary mutual diffusion. Studies of three- and four-component solutions show that the dispersion method is also well suited for multicomponent diffusion measurements, including cross-coefficients for coupled diffusion. Numerical procedures are reported here to calculate mutual diffusion coefficients from dispersion profiles measured for solutions of any number of components. The proposed analysis is used to measure the sixteen quinary mutual diffusion coefficients of five-component aqueous mannitol + glycine + urea + KCl solutions and aqueous NBu₄Cl + LiCl + KCl + HCl solutions. Mannitol, glycine, urea and KCl interact weakly at the low solute concentrations used (0.010 mol·dm^?3). The diffusion coefficients of this system are compared with pseudo-binary predictions. Strong coupling of the NBu₄Cl, LiCl, KCl and HCl fluxes is interpreted by using ionic conductivities and Nernst equations to calculate limiting quinary diffusion coefficients for mixed electrolytes that interact by the electric field generated by ion concentration gradients.     

Liquid–Liquid Equilibrium of Ternary Systems of Methyl Isobutyl Ketone + <Emphasis Type="Italic">o</Emphasis>-Cresol + Water at 298.2, 313.2 and 323.2 K

Liquid–liquid equilibrium (LLE) data for the methyl isobutyl ketone + o-cresol + water ternary system have been experimentally measured from 298.2 to 323.2 K below 101 kPa. The measured LLE data were verified to be highly consistent through the Othmer–Tobias and Hand equations. The extraction efficiency of methyl isobutyl ketone for o-cresol was assessed by the distribution coefficient and separation factor. The experimental results correlated well with two excess Gibbs energy models: non-random two-liquid and universal quasi chemical, which also yielded binary interaction parameter.     

Determination of Aristocularine Enantiomers by Dispersive Liquid–Liquid Microextraction and Chiral High-performance Liquid Chromatography

Here is reported a novel analytical approach for the extractive separation and determination of enantiomeric ratios of aristocularine in bovine serum albumin. The results demonstrate suitable analytical performances. The separation was performed by chiral high-performance liquid chromatography with a 5-µm column using a mobile phase of 1:1 n-hexane:ethanol at a flow rate of 0.7?mL?min^?1 with ultraviolet–visible absorption, circular dichroism, and polarimetric detection. The enantiomers were eluted at 13.2 and 15.6?min for (+) and (?)-aristocularine, with a resolution of 1.58 and a separation factor of 1.27. The analytical parameters for the dispersive liquid–liquid microextraction were optimized; under these conditions, the extraction recoveries were from 88.6% to 93.9% for a two-step extraction. The precision, reported as the percent relative standard deviation, had values from 2.9% to 3.2% for 0.5?µg?mL^?1 of analyte for five replicate measurements using ultraviolet–visible absorption and circular dichroism detection. The limits of detection were between 0.05 and 0.08?µg?mL^?1 with enrichment ratios up to a value of 12.     

Mechanistic and dual-level direct dynamics studies on the reaction Cl + CH2FCl

Theoretical investigations are carried out on the reaction Cl + CH₂FCl by means of direct dynamics method. The minimum energy path (MEP) is obtained at the MP2/6-311G(d, p) level. The energetic information is further improved by single-point energy calculations using QCISD(T)/6-311++G(d, p) method. The kinetics of this reaction are calculated by canonical variational transition state theory incorporating with the small-curvature tunneling correction over a wide temperature range of 220–3,000 K, and rate constant expression are found to be k(T) = 1.48 × 10^?17 T ^2.04exp(?913.91/T). For the title reaction, H-abstraction reaction channel is the major channel at the lower temperatures. At higher temperatures, the contribution of Cl-abstraction reaction channel should be taken into account.     

Excess molar volumes and viscosity deviations of the ternary system of 1-butanol + 2-butanol + 1,3-butanediol at 303.15 K

Abstract  The viscosity and density of ternary mixtures of 1-butanol + 2-butanol + 1,3-butanediol and the binary systems 1-butanol + 2-butanol, 1-butanol + 1,3-butanediol, and 2-butanol + 1,3-butanediol were measured at 303.15 K and atmospheric pressure over the entire range of compositions. Excess molar volumes V ^E and viscosity deviations Δη were obtained from the experimental results for the binary and ternary systems and fitted to Redlich–Kister’s and Cibulka’s equations in terms of mole fractions. The results obtained for the viscosity of liquid mixtures were used to test the semi-empirical relations of Grunberg–Nissan, Hind, and the two-parameter McAllister, Kendall, and Frenkel equations. The experimental data for the ternary system and the constituting binaries are analyzed to discuss the nature and strength of intermolecular interactions in these mixtures. Graphical abstract        

Dynamic and Rheological Properties of Span 80 at Liquid–Liquid Interfaces

The adsorption characteristics of Span 80 at liquid/liquid interfaces were investigated. The equilibrium interfacial tension values were successfully fitted with a Langmuir isotherm resulting in the determination of a mean molecular area from 25 to 35 Å²/mol. The measured interfacial tension values and deduced adsorption parameters depend on the experimental technique used to obtain them, either Du Noüy ring or profile analysis tensiometry. Two possible explanations to such phenomenon are provided. Adsorption kinetics of Span 80 at liquid/liquid interfaces were studied, and it was concluded that the diffusion of Span 80 molecules from the bulk is the rate determining step of the adsorption. Finally the interfacial rheology properties were investigated and compared to the Lucassen–van den Tempel model. A good match was obtained when the isotherm parameters determined by profile analysis tensiometry were used.      

A Dissipative Reaction Network Drives Transient Solid–Liquid and Liquid–Liquid Phase Cycling of Nanoparticles

Transient states maintained by energy dissipation are an essential feature of dynamic systems where structures and functions are regulated by fluxes of energy and matter through chemical reaction networks. Perfected in biology, chemically fueled dissipative networks incorporating nanoscale components allow the unique properties of nanomaterials to be bestowed with spatiotemporal adaptability and chemical responsiveness. We report the transient dispersion of gold nanoparticles in water, powered by dissipation of a chemical fuel. A dispersed state that is generated under non-equilibrium conditions permits fully reversible solid–liquid or liquid–liquid phase transfer. The molecular basis of the out-of-equilibrium process is reversible covalent modification of nanoparticle-bound ligands by a simple inorganic activator. Activator consumption by a coupled dissipative reaction network leads to autonomous cycling between phases. The out-of-equilibrium lifetime is tunable by adjusting the pH value, and reversible phase cycling is reproducible over several cycles.     

Ionic Liquid–Liquid Extraction and Supported Liquid Membrane Analysis of Lipophilic Wood Extractives from Dissolving-Grade Pulp

In this study, the extraction of lipophilic wood extractives from dissolving pulp samples using ionic liquid–liquid extraction and a two phase hollow fibre supported liquid membrane was investigated. Ionic liquids are capable of dissolving a range of organic and polymeric compounds and are biodegradable, with a negligible vapour pressure. Pulp samples were dissolved in a suitable amount of molten 1-butyl-3-methylimidazolium chloride to give 5 % cellulose solution. Pure cellulose was regenerated by adding water and filtered off. The ionic liquid-aqueous filtrate was first extracted for lipophilic extractives using liquid–liquid extraction. Then, a two phase hollow fibre supported liquid membrane extraction of lipophilic extractives was performed to extract the derivatized compounds prior to analysis by gas chromatography mass spectrometry. The operational parameters of this sample preparation approach were optimised using sterols and fatty acid methyl esters. The variation of enrichment factors and extraction efficiency with respect to liquid membrane, extraction time, stirring speed and sample pH were observed and used to get the optimal parameters. The approach was used in the analysis of oxygen bleached dissolving pulp samples in which main compounds identified were fatty acids, sterols, fatty alcohols, steroid hydrocarbons and ketones. These compounds were similar to those obtained using molecular solvent extraction method, which indicated the absence of chemical reaction between extractives and ionic liquid used.

     

Determination of Aflatoxins in Plant-based Milk and Dairy Products by Dispersive Liquid–Liquid Microextraction and High-performance Liquid Chromatography with Fluorescence Detection

The consumption of plant-based milk has increased due to their nutritional attributes. However, these products may contain aflatoxins if contaminated raw materials were used, although little concern is present in international regulation regarding this topic. In this work, dispersive liquid–liquid microextraction (DLLME) was used for the determination of the most important aflatoxins (B₁, B₂, G₁, and G₂) in oat, rice, coconut, almond, and birdseed plant-based milk and milk-based products enriched with oats, almonds, and walnuts using high-performance liquid chromatography (HPLC) with photochemical derivatization and fluorescence detection. Calibrations in matrix were performed for all of the samples, obtaining satisfactory linearity, with correlation coefficients exceeding 0.994 for all of the aflatoxins. The precision in terms of repeatability and intermediate precision, expressed as the relative standard deviation, was lower than 9.7%, and recoveries ranged between 82 and 104%, fulfilling current legislation for the determination of aflatoxins. In addition, the limits of quantification were 0.5?µg?L^?1 for the aflatoxins, allowing the determination of these compounds below the maximum levels established by European Commission in these commodities. Finally, 23 commercial products were analyzed to characterize the presence of these toxins.     

Magnetic Solid-Phase Extraction and Ionic Liquid Dispersive Liquid–Liquid Microextraction Coupled with High-Performance Liquid Chromatography for the Determination of Hexachlorophene in Cosmetics

An efficient, simple, and fast method based on ionic liquid dispersive liquid–liquid microextraction (IL-DLLME) followed by magnetic solid-phase extraction (MSPE) was developed as a new technique for extracting and purifying hexachlorophene (HCP) in cosmetics prior to high-performance liquid chromatography (HPLC) determination. In this method based on IL-DLLME and MSPE, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) is used as the extraction solvent and Fe₃O₄ nanoparticles are used to remove hydrophobic additives in the cosmetics by physical adsorption. The main parameters affecting the efficiency of the IL-DLLME and MSPE of HCP were investigated and optimized. Under the optimum conditions, the method was linear in the range 0.5–40 µg mL^?1 with a correlation coefficient (R ²) of 0.9976 and had a detection limit of 0.14 µg mL^?1 at a signal-to-noise ratio (S/N) of 3. The recoveries of HCP in three cosmetic samples using the proposed method were in the range 74.5–97.7%, and the relative standard deviations (RSD, n = 5) were in the range 3.8–6.7%. The developed method was successfully applied to the determination of HCP in cosmetics.     

Influence of Plasma Treatments on the Hemocompatibility of PET and PET + TiO2 Films

A dielectric barrier discharge (DBD) in helium was used to ameliorate the interface between the blood and the surface of polymeric implants: polyethylene terephthalate (PET) and PET with titanium oxide (PET + TiO₂). A higher crystallinity degree was found for the DBD treated samples. The wettability of polymers was improved after the treatment. The chemical composition, analyzed by infrared spectroscopy was preserved during the DBD treatment. The surface modifications have been correlated with polymers hemocompatibility. Concerning the polymer surface–blood interaction, the treatment induced a decrease of the interfacial tension between the blood components and the treated surfaces. The in vitro tests of hemocompatibility showed no perturbation in the blood composition when the polymer samples are present in the blood volume. An interesting result is related to the whole blood clotting time that shows a dramatic increase on the treated surfaces. Moreover, the coagulation kinetics on the treated surfaces is modified.     

High-Performance Liquid Chromatography of 2′-5′Oligoadenylates and Related Oligonucleotides

Abstract

HPLC has been used for the analysis and separation of the components of p_x (A2′p)_n A (x = 1 to 3, n = 1 to ≥4). Weak anion exchange columns give excellent resolution, but their instability in phosphate buffers makes them impractical for routine use. Reverse phase chromatography using C18 columns provides a satisfactory alternative method. For preliminary analysis of crude material, ammonium phosphate pH7.0 with a linear 1:1 methanol/H₂O gradient gives a good basic separation of the individual oligomers. Resolution of the 5′ mono-, di-and triphosphorylated oligomers or of the nonphosphorylated components can be obtained using ammonium phosphate pH6.0 and potassium phosphate pH6.5 buffers respectively. The C18 columns are very stable and any one column will give retention times reproducible within 0.2%.