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.

     

The Enhancement of the Formation of Wells–Dawson-Type Polyoxometalates by the Addition of High Concentrations of LiCl

Wells–Dawson-type polyoxometalates are formed by heating an acidic Mo(VI) or W(VI) solution containing significantly higher concentrations of hetero ions, P(V) or As(V), than the ideal molar ratio [M]/[X] = 1/9 (M = Mo, W; X = P, As). Most of the phosphate and arsenate remains unreacted in the reaction mixture. These reaction conditions are unusual, even though more reagents than the stoichiometric amounts are frequently needed to obtain complete reactions. In the present study, the replacement of a large amount of unreacted hetero ions containing salts by normal ions (salts) was investigated. The formation of Wells–Dawson-type polyoxometalates, [X₂M₁₈O₆₂]^6? (X = P, As; M = Mo, W), in the presence of LiCl and NaCl was investigated by Raman spectroscopy and ³¹P NMR in aqueous solution. The addition of LiCl enhanced the formation of Wells–Dawson-type polyoxometalates, which formed under solution conditions close to the ideal molar ratio [M]/[X] = 1/9.     

Enhancement of the Activity and Enantioselectivity of Lipase by Sol–Gel Encapsulation Immobilization onto β-cyclodextrin-Based Polymer

Candida rugosa lipase was encapsulated within a chemically inert sol–gel support prepared by polycondensation with tetraethoxysilane and octyltriethoxysilane in the presence of β-cyclodextrin-based polymer. The catalytic activity of the encapsulated lipases was evaluated both in the hydrolysis of p-nitrophenylpalmitate and the enantioselective hydrolysis of racemic Naproxen methyl ester. It has been observed that the percent activity yield of the encapsulated lipase was 65 U/g, which is 7.5 times higher than that of the covalently immobilized lipase. The β-cyclodextrin-based encapsulated lipases had higher conversion and enantioselectivity compared with covalently immobilized lipase. The study confirms an excellent enantioselectivity (E >300) for the encapsulated lipase with an enantiomeric excess value of 98% for S-naproxen.     

Sensitive Determination of Prulifloxacin by Its Fluorescence Enhancement on Terbium(III)–Sodium Dodecylbenzene Sulfonate System

Abstract

A terbium-sensitized fluorescence spectrophotometry method using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was developed for the determination of prulifloxacin (PUFX). It was found that SDBS significantly enhanced the fluorescence intensity of the PUFX–Tb³⁺ complex (about 13-fold). The optimal experimental conditions were determined as follows: excitation and emission wavelengths of 290 nm and 545 nm, pH 8.0, 4.0 × 10^?5 mol L^?1 terbium(III), and 4.0 × 10^?4 mol L^?1 SDBS. The enhanced fluorescence intensity of the system (ΔF) showed a good linear relationship with the concentration of PUFX over the range 6.0 × 10^?8 to 2.0 × 10^?6mol L^?1 with a correlation coefficient of 0.9991. The detection limit (S/N = 3) was determined as 8.5 × 10^?9 mol L^?1. This method has been successfully applied for the determination of PUFX in pharmaceuticals and human urine/serum samples. Compared with most other methods reported, the rapid and simple procedure proposed here offered higher sensitivity, wider linear range, and good stability. The luminescence mechanism of the system was also discussed in detail. In the fluorescence system of PUFX–Tb³⁺–SDBS, SDBS acted not only as the surfactant but also as the energy donor.     

Sensitive Analysis of 5-(4,6-Dichloro-s-triazin-2-ylamino)fluorescein-Labeled Catecholamines by Mixed MEKC–LIF

Mixed micellar electrokinetic chromatography with laser-induced fluorescence detection has been used for analysis of the catecholamines norepinephrine, epinephrine, and dopamine. The fluorescent reagent 5-(4,6-dichloro-s-triazin-2-ylamino)fluorescein was used to label the three compounds. The reaction rate increased with increasing alcohol concentration in the derivatization buffer. Under the optimum conditions the derivatization reaction was complete within 10 min. The separation was performed with 40 mM sodium cholate, 30 mM sodium dodecyl sulfate, 30 mM sodium borate (pH 9.6), and acetonitrile 8.0% (v/v) as running buffer. The applied potential was 25 kV and the capillary temperature was 25 °C. The detection limits for norepinephrine, epinephrine, and dopamine were 3.3, 0.25, and 1.26 nM. The method was successfully applied to monitoring of these catecholamines in human urine. Recovery of the three analytes ranged from 93.2 to 105.8%.     

Pd–NHC Catalyzed Biaryl Coupling by Direct C–H Activation—A Novel Strategy for the Synthesis of Dibenzocyclooctane Lignans

Cross-coupling reactions, such as Buchwald-Hartwig arylamination and direct intramolecular biaryl coupling by C–H activation, were carried out using various Palladium-N-heterocyclic carbenes (Pd–NHC) as catalysts. The yields were good to excellent. The latter strategy was adopted to transform two dibenzylbutane lignans, isolated from the leaves of Ocotea macrophylla (Lauraceae), into the corresponding dibenzocyclooctane lignans in good overall yields.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Activity Enhancement of Pt/Ba/Al2O3 Mixed with Mn/Ba/Al2O3 for NOx Storage-reduction by Hydrogen

The storage and reduction of nitrogen oxides has attracted much attention as an efficient way to reduce NOx emission of lean-burn gasoline and diesel engines1-5. At present, NOx storage and reduction (NSR) catalysts based on Pt and Ba have been extensivel…     

Enhancement of the performances of a single concentric glucose/O2 biofuel cell by combination of bilirubin oxidase/Nafion cathode and Au–Pt anode

This work deals with a novel preparation method of bilirubin oxidase/2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid electrode. The enzyme and its mediator were adsorbed on carbon Vulcan XC-72R before their immobilization into a Nafion^® matrix. Promising results were obtained when this biocathode was associated with Au₇₀Pt₃₀ nanoparticles as anode in a single concentric glucose/O₂ biofuel cell (BFC). The latter BFC delivered at 37 °C a power density of 90 μW cm^?2 for a cell voltage of 0.4 V in phosphate buffer (pH 7.4) containing 0.01 M glucose. Moreover, the electrical performances were increased with the concentration of glucose by generating up to 190 μW cm^?2 for a cell voltage of 0.52 V when the concentration of the renewable fuel reached 0.7 M.     

Synthesis of (Tetrahydrofuranyl)methyl-1,2,3-triazoles Through Alkyne–Azide Cycloaddition Catalyzed by a Dithioic Acid Copper(I) Complex

(Tetrahydrofuranyl)methyl-1,2,3-triazoles were synthesized from tetrahydrofurfuryl tosylate and several alkynes in the presence of catalytic amounts of a 3-hydroxy-3-phenyl-2-propenendithioate-bis(triphenylphosphine) copper(I) complex. The reaction process is carried in out under mild conditions, and bases or reducing agents were not used. The reaction afforded the 1,4-regioisomers in excellent yields.      

Enhancement of critical current density in superconducting YBa2Cu3O7−x films by nanostructure development of substrate surface using sol–gel method

In this paper, a simple sol–gel route has been adopted in developing substrate surface for the first time. Only by adjusting the concentration of precursor solution, LaAlO₃ (LAO) nanodot arrays were directly obtained on LAO single crystal substrate, without incorporating additional processing steps. Subsequently, YBa₂Cu₃O_7?x (YBCO) superconducting films were prepared on the nanodot arrays using a low-fluorine solution process. In contrast, J _c of YBCO films grown on the substrate developed with nanodot arrays is almost three times as large as that of YBCO films grown on undeveloped substrate in an applied magnetic field with the strength of 3 Tesla. The pinning force density (F _p ) of YBCO film on the nanodot arrays developed substrate is 2.7 GN/m³ which exceeds that (1.8 GN/m³) of YBCO films on undeveloped substrate. The results of cross-section transmission electron microscope (TEM) images show that the extended defects along the a–b planes of YBCO, induced by the developed substrate with nanodot arrays, should be the origin of the J _c enhancement.     

Asymmetric Inverse-Electron-Demand Hetero-Diels–Alder Reaction for the Construction of Bicyclic Skeletons with Multiple Stereocenters by Using a Bifunctional Organocatalytic Strategy: An Efficient Approach to Chiral Macrolides

We have performed the first bifunctional organocatalytic highly enantioselective inverse-electron-demand hetero-Diels–Alder reaction of cyclic ketones with enones to afford densely functionalized bicyclic skeletons that contain three stereocenters (up 82 % yield, 10:1 d.r., and 97 % ee). Unlike the previous IEDDAR catalytic strategy, this method features a double HOMO_dienophile/ LUMO_diene-activated pathway. Moreover, this process provides a promising method for the construction of enantioenriched macrolides.     

Study of Solvent Composition Effects on the Protonation Equilibria of Various Anilines by Multiple Linear Regression and Factor Analysis Applied to the Correlation Between Protonation Constants and Solvatochromic Parameters in Ethanol–Water Mixed Solvents

The stoichiometric protonation constants (log) of aniline derivatives were determined potentiometrically over a wide range of solvent composition (0–0.74 mole fraction of ethanol). To explain the variation of the log values obtained over the whole composition range studied, the quasi-lattice quasi-chemical theory of preferential solvation was applied. The results were discussed in terms of macroscopic properties of the mixed solvent and different microscopic parameters, such as the Kamlet–Taft solvatochromic parameters to identify the solvent characteristics affecting the log values. Kamlet and Taft's general equation was reduced to two terms by using both multiple-linear regression analysis and combined factor analysis and target factor analysis in these mixtures: the independent term and the hydrogen-bond donating ability (HBD), which is a solvatochromic parameter. Hammett's reaction constant for the protonation of anilines has been obtained for all the solvent mixtures and correlates well with (HBD) of the solvent.     

Determination of Ultra-Trace Platinum,Palladium, Ruthenium,Rhodium, and Iridium in Rocks and Minerals by Inductively Coupled–Plasma Mass Spectrometry Following Nickel Sulfide Fire Assay Preconcentration and Open Mixed Acid Digestion

Platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), iridium (Ir), and osmiun (Os) are platinum-group elements with similar physic-chemical properties, and have important applications in geochemistry and environmental chemistry. However, due to their low abundance and inhomogeneous distribution in natural ores as well as the nugget effect, the accurate determination of the platinum-group elements has been a challenge for geological analysis. In this work, self-prepared and purified sodium carbonate (NiCO₃) instead of commercial nickel oxide (NiO) was used as the fire assay collector in order to greatly reduce the reagent blank and method detection limits. In addition, the fuming time of HClO₄ was strictly controlled at 10?min and a high sensitive method was developed for the simultaneous determination of ultra-trace Pt, Pd, Ru, Rh, and Ir in minerals by inductively coupled plasma-mass spectrometry (ICP-MS) following preconcentration with the nickel sulfide fire assay. Under the optimized conditions, the linear ranges of Pt, Pd, Ru, Rh, and Ir were between 0 and 100?ng mL^?1, with correlation coefficients exceeding 0.9997. The detection limits were 0.015, 0.056, 0.014, 0.004, 0.012?ng mL^?1 (for 10?g sample) for Pt, Pd, Ru, Rh and Ir, respectively. The developed method was successfully applied to analyze Chinese Certified Reference Materials (CRMs) GBW07288, GBW07289, GBW07290, GBW07291, GBW07292, GBW07293, GBW07294, GBW07101, GBW07102 and GBW07201 and the determined values were in good agreement with the certified values. The relative standard deviations (n?=?5) of Pt, Pd, Ru, Rh and Ir were between 3.42% and 6.87% for the determination of GBW07291.     

Reactions of the Dirhenium(II) Complexes Re2X4(μ-dppm)2 (X=Cl, Br; dppm=Ph2PCH2PPh2) with Isocyanides. XXII. A Comparison of Mixed Carbonyl–Isocyanide Complexes with Those Formed by Re2Cl4(μ-dcpm)2 (dcpm=Cy2PCH2PCy2)

The reactions of the electron-rich triply bonded dirhenium(II) complex Re₂Cl₄(-dcpm)₂ (dcpm=Cy₂PCH₂PCy₂) with the isocyanide ligands XylNC (Xyl=2,6-dimethylphenyl) and t-BuNC afford the complexes Re₂Cl₄(-dcpm)₂(CNXyl) and Re₂Cl₄(-dcpm)₂(CN-t-Bu)₂ which in turn react with CO to give salts of the [Re₂Cl₃(-dcpm)₂(CO)₂(CNXyl)]⁺ and [Re₂Cl₃(-dcpm)₂(CN-t-Bu)₂(CO)]⁺ cations which exist in different isomeric forms. This chemistry is compared with that developed previously for the analogous complexes derived from Re₂Cl₄(-dppm)₂.