Vapour pressure osmometry determination of water activity of binary and ternary aqueous (polymer + polymer) solutions

Precise water activity measurements at T = 308.15 K were carried out on several binary (water + polymer) and ternary {water + polymer (1) + polymer (2)} systems using the vapour pressure osmometry (VPO) technique. Polymers were polyethylene glycol 400 (PEG400), polyethylene glycol 6000 (PEG6000), polypropylene glycol 400 (PPG400), polyvinylpyrrolidone (PVP) and dextran (DEX). The water activity results obtained were used to calculate the vapour pressure of solutions as a function of concentration and the segment-based local composition models, NRTL and Wilson, were used to correlate the experimental water activity values. It was found that, for the polymer concentration range studied here, the values of the water activity obtained for the binary (water + polymer) solutions decrease in the order DEX > PVP > PEG6000 > PPG400 > PEG400. Furthermore, water activities of solutions of each polymer in the aqueous solutions of (5, 10, 15 and 20)% (w/w) other polymers investigated were also measured at T = 308.15 K. The ability of polymer (1) in decreasing the water activity of binary {water + polymer (2)} solutions was discussed on the basis of the (polymer + water) and {polymer (1) + polymer (2)} interactions.     

Photo-induced degradation of some flavins in aqueous solution

The blue-light induced photo-degradation of FMN, FAD, riboflavin, lumiflavin, and lumichrome in aqueous solution at pH 8 is studied by measurement of absorption coefficient spectral changes due to continuous excitation at 428 nm. The quantum yields of photo-degradation determined are ϕ_D(riboflavin, pH 8) ≈ 7.8 × 10⁻³, ϕ_D(FMN, pH 5.6) ≈ 7.3 × 10⁻³, ϕ_D(FMN, pH 8) ≈ 4.6 × 10⁻³, ϕ_D(FAD, pH 8) ≈ 3.7 × 10⁻⁴, ϕ_D(lumichrome, pH 8) ≈ 1.8 × 10⁻⁴, and ϕ_D(lumiflavin, pH 8) ⩽ 1.1 × 10⁻⁵. In a mass-spectroscopic analysis, the photo-products of FMN dissolved in water (solution pH is 5.6) were identified to be lumichrome and the lumiflavin derivatives dihydroxymethyllumiflavin, formyllumiflavin, and lumiflavin-hydroxy-acetaldehyde. An absorption and emission spectroscopic characterisation of the primary photoproducts of FMN at pH 8 is carried out.     

Determining mineral elements in four kinds of grains from Beijing market by ICP-MS simultaneously

Mineral elements are essential components for human health from food, but their contents in wheat, millet, corn and soybean have not been compared. Contents of mineral elements in wheat, millet, corn and soybean from Beijing market of China were detected by ICP-MS. The RSDs (relative standard deviation) range from 0.85% to 3.52% and the detecting limits range from 0.13 to 0.85 μg/L, which showed that this method is accurate and precise to detect mineral elements in grains simultaneously. The data showed that (1) ICP-MS is a simple and precise method to determine many mineral elements in grains simultaneously. (2) Elements followed by descending order in four grains are usually K > Mg > Ca > Fe > Zn > Mn > Cu > Mo > Li, and grains arranged in order from high to low levels of mineral elements are usually soybean > millet > wheat ≈ corn. So we should take in more minor grains, such as soybean and millet on daily diet.     

Effect of reaction conditions on hydrothermal degradation of cornstalk lignin

Cornstalk lignin was hydrothermally depolymerized at mild conditions in ethanol–water for producing value-added phenolics. The effects of residence time (from 30 min to 180 min), reaction temperature (from 498 K to 573 K) and concentration of ethanol (from 0% to 95% vol.) on yields of liquid products and phenolic compounds were studied in detail. The optimal conditions of 523 K, 90 min and 65% vol. ethanol–water resulted in the highest yield of liquid products (∼70 wt.%). The liquid products were analyzed by gas chromatography–mass spectrometry (GC–MS) to confirm the presence of primarily heterocycle (2,3-dihydrobenzofuran) and phenolics (such as ethylphenol, guaiacol, ethylguaiacol and syringol). Reaction conditions had significant effects on yield and composition of liquid products.     

Free radical scavenging and COX-2 inhibition by simple colon metabolites of polyphenols: A theoretical approach

Free radical scavenging and inhibitory potency against cyclooxygenase-2 (COX-2) by two abundant colon metabolites of polyphenols, i.e., 3-hydroxyphenylacetic acid (3-HPAA) and 4-hydroxyphenylpropionic acid (4-HPPA) were theoretically studied. Different free radical scavenging mechanisms are investigated in water and pentyl ethanoate as a solvent. By considering electronic properties of scavenged free radicals, hydrogen atom transfer (HAT) and sequential proton loss electron transfer (SPLET) mechanisms are found to be thermodynamically probable and competitive processes in both media. The Gibbs free energy change for reaction of inactivation of free radicals indicates 3-HPAA and 4-HPPA as potent scavengers. Their reactivity toward free radicals was predicted to decrease as follows: hydroxyl >> alkoxyls > phenoxyl ≈ peroxyls >> superoxide. Shown free radical scavenging potency of 3-HPAA and 4-HPPA along with their high μM concentration produced by microbial colon degradation of polyphenols could enable at least in situ inactivation of free radicals. Docking analysis with structural forms of 3-HPAA and 4-HPPA indicates dianionic ligands as potent inhibitors of COX-2, an inducible enzyme involved in colon carcinogenesis. Obtained results suggest that suppressing levels of free radicals and COX-2 could be achieved by 3-HPAA and 4-HPPA indicating that these compounds may contribute to reduced risk of colon cancer development.     

Reactivity of sugar cane bagasse as a natural solid phase extractor for selective removal of Fe(III) and heavy-metal ions from natural water samples

This work introduces the feasibility of using sugar cane bagasse (SCB) – a sugar cane industry waste – as a selective solid phase extractor for Fe(III). The order of metal uptake capacities in μmol g^?1 for the extraction of six tested metal ions from aqueous solution using static technique is Fe(III) > Cu(II) > Pb(II) > Zn(II) > Cd(II) > Co(II). Since SCB exhibits remarkable binding characteristics for Fe(III), special interest was devoted for optimizing its uptake and studying its selectivity properties under static and dynamic conditions. In this respect, batch experiments were carried out at the pH range 1.0–4.0, initial concentration of metal ion (10–100 μmol), weight of phase (25, 50, 75, 100, 125 and 150 mg) and shaking time (10, 30, 45, 60, 90, 120 and 150 min). FT-IR spectra of SCB before and after uptake of Fe(III) were recorded to explore the nature of the functional groups responsible for binding of Fe(III) onto the studied natural biosorbent. The equilibrium data were better fitted with Langmuir model (r² = 0.985) than Freundlich model (r² = 0.934). Moreover, Fe(III) sorption was fast and completed within 60 min. The adsorption kinetics data were best fitted with the pseudo-second-order type. As a view to find a suitable application of SCB based on its unique property as a benign sorbent, it was found that, Fe(III) spiked natural water samples such as doubly distilled water (DDW), drinking tap water (DTW), natural drinking water (NDW), ground water (GW) and Nile River water (NRW) was quantitatively recovered (>95.0%) using batch and column experiments, with no matrix interferences.     

Evaluation of Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole as photostabilizer for poly(methyl methacrylate)

The photostabilization of poly(methyl methacrylate) (PMMA) films by Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole compounds was investigated. The PMMA films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform solvent. The photostabilization activities of these compounds were determined by monitoring the hydroxyl index with irradiation time. The changes in viscosity average molecular weight of PMMA with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φ_cs) of these complexes in PMMA films was evaluated and found to range between 4.19 × 10^?5 and 8.75 × 10^?5. Results obtained showed that the rate of photostabilization of PMMA in the presence of the additive followed the trend:[1] > [2] > [3] > [4] > [5].According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among them, UV absorption, peroxide decomposer, and radical scavenger for photostabilizer mechanisms were suggested.     

Use of hydrophobins in formulation of water insoluble drugs for oral administration

The poor water solubility of many drugs requires a specific formulation to achieve a sufficient bioavailability after oral administration. Suspensions of small drug particles can be used to improve the bioavailability. We here show that the fungal hydrophobin SC3 can be used to make suspensions of water insoluble drugs. Bioavailability of two of these drugs, nifedipine and cyclosporine A (CyA), was tested when administered as a SC3-based suspension. SC3 (in a 1:2 (w/w) drug:SC3 ratio) or 100% PEG400 increased the bioavailability of nifedipine to a similar degree (6 ± 2- and 4 ± 3-fold, respectively) compared to nifedipine powder without additives. Moreover, SC3 (in a 7:1 (w/w) drug:hydrophobin ratio) was as effective as a 20-fold diluted Neoral^® formulation by increasing bioavailability of CyA 2.3 ± 0.3-fold compared to CyA in water. Interestingly, using SC3 in the CyA formulation resulted in a slower uptake (p < 0.001 in T_max) of the drug, with a lower peak concentration (C_max 1.8 mg ml^?1) at a later time point (T_max 9 ± 2 h) compared to Neoral^® (C_max 2.2 mg ml^?1; T_max 3.2 ± 0.2). Consequently, SC3 will result in a more constant, longer lasting drug level in the body. Taken together, hydrophobins are attractive candidates to formulate hydrophobic drugs.     

Dynamic viscosity versus probe-reported microviscosity of aqueous mixtures of poly(ethylene glycol)

Correlation between the dynamic viscosity (η) and the microviscosity of a hybrid green medium constituted of water and poly(ethylene glycol) (PEG) of average molar mass (200, 400, and 600) g · mol^?1, respectively, is explored over the temperatures range (10 to 90) °C across the complete composition regime. The microviscosity is obtained using a fluorescence probe 1,3-bis-(1-pyrenyl)propane (BPP), which is manifested through the ratio of the monomer-to-intramolecular excimer intensities (I_M/I_E). Aqueous PEG mixtures are observed to behave similar to Newtonian fluids as the temperature dependence of dynamic viscosity follows Arrhenius-type behavior. Surprisingly, a simple and convenient linear dependence of ln η with wt% PEG of the mixture is established. The BPP I_M/I_E is observed, in general, to increase with the bulk dynamic viscosity of the mixture having >10 wt% PEG suggesting a good correlation between the bulk dynamic viscosity and BPP-reported microviscosity when the viscosity of the aqueous PEG mixture is relatively high.     

Kinetics of thermal and photolytic degradation of decabromodiphenyl ether (BDE 209) in backcoated textile samples

Kinetics of the thermal and photolytic degradation of decabromodiphenyl ether (DBE 209) was studied using HPLC. Samples lost an amount of ∼8.4% (w/w), 24% (w/w), 39.4% (w/w) and 28.5% of the amount of DBE 209 originally present in the samples due to ageing at 25, 60, 90 °C and UV exposure, respectively. The thermal and photolytic release was found to follow the first order kinetics with rate constants estimated to be 3.6 × 10⁻³, 1.03 × 10⁻², 3.6 × 10⁻² and 3.94 × 10⁻² day⁻¹, respectively. Ageing of the textile samples enhanced the release of the DBE 209 from the backcoated textile. Photodegradation of BDE 209 into lower congeners of brominated flame retardants was also observed for the UV-aged samples.Migration of DBE 209 from the backcoated textile into biological fluids was studied using Head-over-Heels and contact-Blotting test for unaged, thermally and UV aged samples. The presence of biological fluids (sweat, saliva and juice) was found to enhance the migration of DBE 209 compared to water. Migration of BDE 209 into artificial biological fluids is significantly increased for samples previously exposed to UV radiation or thermally aged. An increase from 0.6% (w/w) to a maximum of 2% (w/w) of the amount of BDE 209 migrated into artificial biological fluids due to ageing conditions in the presence of biological fluid was recorded.     

A green route to enantioenriched (S)-arylalkyl carbinols by deracemization via combined lipase alkaline-hydrolysis/Mitsunobu esterification

Herein we report results of the chemoenzymatic deracemization of a range of secondary benzylic acetates 1a–9a via a sequence of hydrolysis with CAL-B lipase in non-conventional media, combined with esterification of the recovered alcohol according to the Mitsunobu protocol following an enzymatic kinetic resolution (KR). The KR of racemic acetates 1a–9a via an enzymatic hydrolysis, with CAL-B lipase and Na₂CO₃, in non-aqueous media was optimized and gave high selectivities (E ? 200) at good conversions (C >49%) for all of the substrates studied. This method competes well with the traditional one performed in a phosphate buffer solution. The deracemization using Mitsunobu inversion gave the (S)-acetates in moderate to excellent enantiomeric excess 75% < ee < 99%, in acceptable isolated yields 70% < yield < 89%, and with some variations according to the acetate structure.     

The determination of cysteine at Bi-powder carbon paste electrodes by cathodic stripping voltammetry

The determination of cysteine by means of square wave cathodic stripping voltammetry (SWCSV) is reported here for the first time at Bi-modified carbon paste electrodes (CPEs). The modified electrodes are 17% w/w metallic Bi powder mixed with CP (Bi-CPEs) and the technique is based on the enhancement of Bi surface oxidation in the presence of cysteine at a carefully chosen accumulation potential and the subsequent reduction-stripping of the product (proposed to be bismuth(III) cysteinate) by potential scanning to more negative values. The wide concentration range of 1 × 10⁻⁶–5 × 10⁻⁵ M for cysteine can be assessed by SWCSV using Bi-CPEs and, by appropriate choice of accumulation times, two linear response concentration regimes could be identified: 1 × 10⁻⁶–1 × 10⁻⁵ M (accumulation for 600 s) and 1 × 10⁻⁵–5 × 10⁻⁵ M (accumulation for 100 s), with estimated detection limits of 3 × 10⁻⁷ and 2 × 10⁻⁶ M, respectively.     

Densities and volume properties of (water + tert-butanol) over the temperature range of (274.15 to 348.15) K at pressure of 0.1 MPa

The densities of {water (1) + tert-butanol (2)} binary mixture were measured over the temperature range (274.15 to 348.15) K at atmospheric pressure using “Anton Paar” digital vibrating-tube densimeter. Density measurements were carried out over the whole concentration range at (308.15 to 348.15) K. The following volume parameters were calculated: excess molar volumes and thermal isobaric expansivities of the mixture, partial molar volumes and partial molar thermal isobaric expansivities of the components. Concentration dependences of excess molar volumes were fitted with Redlich–Kister equation. The results of partial molar volume calculations using four equations were compared. It was established that for low alcohol concentrations at T ? 208 K the inflection points at x₂ ≈ 0.02 were observed at concentration dependences of specific volume. The concentration dependences of partial molar volumes of both water and tert-butanol had extremes at low alcohol content. The temperature dependence of partial molar volumes of water had some inversion at х₂ ≈ 0.65. The temperature dependence of partial molar volumes of tert-butanol at infinite dilution had minimum at ≈288 K. It was discovered that concentration dependences of thermal isobaric expansivities of the mixture at small alcohol content and low temperatures passed through minimum.     

Electrochemical determination of rosiglitazone by square-wave adsorptive stripping voltammetry method

Square-wave adsorptive stripping voltammetry technique was used to determine rosiglitazone (ROS) on the hanging mercury dropping electrode (HMDE) surface, in Britton Robinson buffer, pH = 5. The voltammetric cathodic peak was observed at ?1520 mV vs. Ag/AgCl reference electrode. The voltammetric peak response was characterized with respect to pH, supporting electrolyte, accumulation potential, preconcentration time, scan rate, frequency, pulse amplitude, surface area of the working electrode and the convection rate. Under optimal conditions, the voltammetric current is proportional to the concentration of ROS over the concentration range of 5 × 10^?8–8 × 10^?7 mol l^?1 (r = 0.9899) with a detection limit of 3.2 × 10^?11 mol l^?1 using 120 s accumulation time. The developed SW-AdSV procedure showed a good reproducibility, the relative standard deviation RSD% (n = 10) at a concentration level of 5 × 10^?7 mol l^?1 was 0.33%, whereas the accuracy was 101% ± 1.0. The proposed method was successfully applied to assay the drug in the human urine and plasma samples with mean recoveries of 90 ± 0.71% and 86 ± 1.0%, respectively.     

Volumetric and viscometric behaviour of the binary systems of N-methyldiethanolamine and diethanolamine with 1-butyl-3-methylimidazolium acetate at various temperatures

In the present work, density and viscosity of two binary mixtures of N-methyldiethanolamine (MDEA) and diethanolamine (DEA) with 1-butyl-3-methylimidazolium acetate ([bmim][acetate]) are measured. The experiments were carried out at atmospheric pressure and at T = (293.15 to 343.15) K for density and from 293.15 K to 353.15 K for viscosity over the whole range of mole fraction. Using the density and viscosity results, several physical and thermodynamic properties such as excess molar volumes (V^E), coefficients of thermal expansions (α), viscosity deviation (Δη),molar activation entropy (ΔS), molar activation enthalpy (ΔH) and molar activation Gibbs free energy (ΔG) for these binary mixtures are calculated.The experimental results of the density and viscosity for the pure systems as well as the binary systems show a decrease with increasing temperature as expected. The results of density measurements show that over all ranges of temperatures investigated the density of the pure components show the following trend: DEA > [bmim][acetate] > MDEA. Therefore, in the binary mixtures of the (MDEA + [bmim][acetate]), the density of the mixture reduces with decreasing concentration of the ionic liquid and for the (DEA + [bmim][acetate]) mixture the density of the blend enhances to reduce the concentration of the ionic liquid. Moreover, the calculated excess molar volumes show a positive deviation from ideality for the two binary mixtures. The behaviour of change of viscosity against concentration for the (MDEA + [bmim][acetate]) system is different from the (DEA + [bmim][acetate]) mixture so that for the first system the value of the viscosity rises with increasing [bmim][acetate] mole fraction, but in the second system there is a minimum viscosity point in the DEA-rich region.     

New insights into the mechanism of flow-electrode capacitive deionization

We report on Faradaic reactions producing H⁺ (anode) and OH^– (cathode) in flow-electrode capacitive deionization (FCDI) operated at 1.2 V. These reactions underline an additional electrodialytical desalination mechanism within capacitive deionization, which proceeds in parallel to the known electrosorption mechanism. Examination of flow-electrodes (100 ml each, 5% (wt) activated carbon) during FCDI (121 cm² effective membrane area) of 150 ml, 4 g/l NaCl solution revealed that significant amounts of Na⁺ and Cl⁻ ions (up to 50% and 30% of Cl⁻ and Na⁺, respectively) were not adsorbed in the activated carbon particles but were rather dissolved in the aqueous phase of the flow-electrodes. Production of acid (resulting in pH ≈ 1.5) and base (pH ≈ 12.5) in the flow-anode and -cathode solutions was observed during the operation. Reverse pH behaviors were obtained during the regeneration of the flow-electrodes by potential reversal. pH neutralization of the flow-electrode solutions resulted in a sharp increase in both the desalination rate and the electric current of the FCDI cell. Reacting NaOH and HCl in a short-circuited FCDI cell resulted in NaCl production in the water compartment and pH neutralization of both flow-electrodes.Apparently reversible Faradaic reactions that occur on the flow electrodes in the FCDI can be dependent on the properties of the carbon material, electrolyte composition and applied operational parameters (e.g. cell potential) and need to be studied in further detailed investigations.     

Chemical composition and antioxidant, α-glucosidase inhibitory and antibacterial activities of three Echeveria DC. species from Mexico

Three Echeveria species from Sinaloa, Mexico (Echeveria craigiana, Echeveria kimnachii and Echeveria subrigida) were analyzed for their content of antioxidant compounds (β-carotene, ascorbic acid, α-tocopherol, total phenolics and flavonoids) and the in vitro antioxidant (DPPH, ABTS, ORAC and β-carotene bleaching [β-CBM]), α-glucosidase inhibitory and antibacterial activities. The studied Echeveria species showed high α-tocopherol content (2.9–9.0 mg/100 g f.w.) and total phenolics as Gallic Acid Equivalents (GAE) (152.2–400.5 mg GAE/100 g f.w.). Antioxidant activities of the three Echeveria methanol extracts (ME) were higher than those of other well-known plants with this property; the activities of E. craigiana (ABTS, 65.91 μmol ET/g f.w.) and E. subrigida (β-CBM, 79.3%) were remarkable. The Echeveria ME showed stronger α-glucosidase inhibition (IC₅₀ 25.21–50.57 μg/mL) than acarbose (IC₅₀ 3.59 mg/mL) as well as high antibacterial activity (Minimal Inhibitory Concentrations, MICs ⩽ 1 mg/mL), mainly against Gram positive bacteria. The results showed the three Echeveria species had components/biological activities with high potential for food/pharmacological uses and could be exploited by sustainable management schemes.     

Improvement of the mechanical and barrier properties of methylcellulose-based films by treatment with HEMA and silane monomers under gamma radiation

Methylcellulose (MC)-based films were prepared by casting from its 1% aqueous solution containing 0.5% vegetable oil, 0.25% glycerol and 0.025% Tween^®-80. Puncture strength (PS), puncture deformation (PD) and water vapor permeability (WVP) of the films were found to be 147 N/mm, 3.46 mm, and 6.34 g mm/m² day kPa, respectively. The monomer, 2-hydroxyethyl methacrylate (HEMA) (0.1–1%, w/w) was incorporated into the MC-based solution and films were prepared by casting. Films were then exposed to gamma radiation (5–25 kGy) and it revealed that 1% HEMA containing films showed the highest PS values (282 N/mm at 10 kGy). Silane monomer (3-aminopropyl tri-ethoxy silane) (0.1–1%, w/w) was also added into the MC-based films and were found to improve the strength of the films significantly. In comparison between HEMA and silane treatment onto MC-based films, it was observed that silane performed better strength and barrier properties. Surface morphology of the monomer treated films was examined by scanning electron microscopy and suggested better appearance than MC-based film.     

Enantioselective rhodium-catalyzed hydroacylation to access the four stereoisomers of anti-rodent difenacoum

An efficient asymmetric synthesis of the four stereoisomers of difenacoum, an anticoagulant currently used as a rodenticide in racemic form, is performed using a key step of rhodium catalyzed enantioselective intramolecular hydroacylation. Optimization of the last step, condensation of 4-hydroxycoumarin with chiral 3-([1,1′-biphenyl]-4-yl)-1,2,3,4-tetrahydronaphthalen-1-ol, is also discussed. After chromatographic separation of the cis and trans diastereoisomers, the four stereoisomers were all obtained with excellent enantioselective and diastereoselective excess (ee ≈ 96% and de >96%).     

Effective synthesis of (S)-3,5-bistrifluoromethylphenyl ethanol by asymmetric enzymatic reduction

The synthesis of (S)-3,5-bistrifluoromethylphenyl ethanol, a pharmaceutically important alcohol intermediate for the synthesis of NK-1 receptor antagonists, was demonstrated from a ketone via asymmetric enzymatic reduction. The isolated enzyme alcohol dehydrogenase from Rhodococcus erythropolis reduced the poorly water soluble substrate with excellent ee (>99.9%) and good conversion (>98%). The optimized process was demonstrated up to pilot scale using high substrate concentration (390 mM) using a straightforward isolation process achieving excellent isolation yields (>90%) and effective space time yield (100–110 g/L d). Process improvements, demonstrated at preparative scale, increased the substrate concentration to 580 mM achieving a space time yield of 260 g/L d.