Measurement and correlation of solubility of diosmin in four pure solvents and β-cyclodextrin solution at 298.15 K to 333.15 K

The aim of present study was to measure and correlate the solubility of poorly water-soluble flavonoid diosmin in water, ethanol, isopropyl alcohol (IPA), polyethylene glycol-400 (PEG-400) andβ-cyclodextrin (β-CD) aqueous solution (0.02 mol·L-1). The solubility of diosmin was measured using the shake flask method from (298.15 to 333.15) K at atmospheric pressure. The experimental solubilities of diosmin were regressed by the modified Apelblat model with a relative deviation in the range of 0.048%to 5.940%. The correlation coefficients were observed in the range of 0.9957 to 0.9995. The solubility of diosmin was found to be increased with temperature in all sample matrices investigated. The mole fraction solubility of diosmin was found to be higher inβ-CD aqueous solution and PEG-400 as compared to water, ethanol and IPA. Based on solubility data of present study, diosmin was considered as practical y insoluble in water, insoluble in ethanol&IPA and soluble in PEG-400 andβ-CD aqueous solution.     

Determination and correlation solubility of 4-nitroimidazole in twelve pure solvents from 278.15 K to 323.15 K

In this paper, the solubility of 4-nitroimidazole in twelve pure solvents (toluene, benzene, 1,4-dioxane, acetonitrile, ethyl acetate, acetone, GBL, ethanol, methanol, n-butanol, DMF and NMP) were determined by using the laser monitoring system from 278.15 K to 323.15 K under 101.1 kPa, which are 0.00018–0.00070, 0.00021–0.00073, 0.00034–0.00092, 0.00038–0.00142, 0.00047–0.00120, 0.00126–0.00303, 0.00225–0.00517, 0.00310–0.00724, 0.00467–0.00982, 0.00453–0.01940, 0.01947–0.04652, and 0.04670–0.07452, respectively. At constant temperature, the mole fraction solubility of 4-nitroimidazole were increased as the following order: toluene < benzene < 1,4-dioxane < (ethyl acetate or acetonitrile) < acetone < GBL < ethanol < (methanol or n-butanol) < DMF < NMP, and the solubility of 4-nitroimidazole in (ethyl acetate, acetonitrile) and (methanol, n-butanol) had an intersection point at 297.55 K and 281.85 K, respectively. The solubility of 4-nitroimidazole could be increased with increasing temperature in twelve pure solvents. The ideal model, modified Apelblat equation, polynomial empirical equation, and λh equation were used to correlate the experimental values. The experimental solubility values were employed to calculate the standard dissolution enthalpy, standard dissolution entropy and Gibbs energy. The dissolution of 4-nitroimidazole could be an endothermic process in twelve pure solvents. The determination and fitting solubility of 4-nitroimidazole have important guiding significance for the purification and crystallization of its preparation process.     

Hydrothermal liquefaction of wheat straw in hot compressed water and subcritical water–alcohol mixtures

Hydrothermal liquefaction of lignocellulosic biomass (wheat straw) into bio-oil has been investigated under subcritical conditions (temperature up to 350 °C, pressure up to 200 bar) in water and water–alcohol mixtures using ethanol and isopropanol in a continuously operated tubular reactor. The effect of different reaction parameters such as temperature, pressure and water–alcohol ratio on the biomass conversion, cracking products yield and the higher heating value (HHV) of the received bio-oil was studied. The water–ethanol mixture was found to be a very reactive medium showing a complete biomass conversion and >30 wt% yield of high caloric oil (HCO). A maximum HHV of 28 MJ/kg for HCO was achieved. In addition, Ru (5 wt%) on H-Beta support was used as catalyst in a run with hydrogen in the feed showing deeper deoxygenation of reaction intermediates and highest HHV of the product oil (30 MJ/kg). This work demonstrated the usability of water–ethanol mixtures for an effective depolymerization of lignocellulosic biomass to bio-oils under subcritical reaction conditions with more than doubled HHV compared to the feedstock, in particular using a catalyst and the presence of hydrogen for further deoxygenation.     

Provitamin a activity and stability of β-carotene in margarine

Summary Samples of synthetic β-carotene have been assayed for vitamin A activity by the rat-curative, growth method against vitamin A acetate and compared with natural carotene. The U.S.P. XIV diet was modified by the addition of vitamin B₁₂ and α-tocopherol, which have been reported to enhance carotene utilization. Doses of vitamin A and carotene were given in cottonseed oil and in margarine; but, contrary to the report of Deuelet al. (13), no significant increase was observed in the utilization of carotene fed in margarine. The samples tested include crystalline all-trans β-carotene, micropulverized all-trans β-carotene in an oil suspension, and a series of 10 commercial margarines fortified with vitamin A. and carotene in a ratio of about 2 I.U. of vitamin A to 1 I.U. of carotene. In terms of vitamin A activity in the rat bioassay, the average potency of β-carotene in three separate bioassays of crystalline carotene was found to be 1,730,000 I.U. per gram with a standard error of ±3.5%. Thus in these assays 1 I.U. of vitamin A activity was found to be equivalent to 0.58 mcg. of all-trans β-carotene, a value in essential agreement with 0.6 mcg., the presently accepted International Standard. For margarine samples containing vitamin A and β-carotene, the average vitamin A activity in 2 bioassays was found to be very close to that calculated from the colorimetric assays, using the factor for β-carotene, 0.6 mcg.=1 I.U. The fact that other workers have reported higher provitamin A activity for β-carotene in the rat bioassay indicates the dependence of the results on the particular conditions of the bioassay. The stability of vitamin A and β-carotene in commercially prepared margarines stored at 40°F. and 75°F. was studied by accepted colorimetric procedures. Average retention values of 94% or better were obtained in margarines stored two months when the vitamin activity was supplied either from β-carotene or from vitamin A.     

Commentary on the “Measurement and correlation of solubility of meropenem trihydrate in binary (water + acetone/tetrahydrofuran) solvent mixtures”

Problem was discussed on the reported equation parameters by Zhou and co-workers[Chinese Journal of Chemical Engineering 25 (10) (2017) 1461-1466] for expressing the meropenem trihydrate solubility in binary (water + acetone and water + tetrahydrofuran) mixtures with the modified Apelblat equation. The reported model parameters do not back-calculate correctly the evaluated solubility as shown in their published work. The reported parameters of the modified Apelblat equation tabulated in Tables 3 and 4 by Zhou and coworkers are in mistake.     

Precipitation and encapsulation of β-carotene in PHBV using carbon dioxide as anti-solvent

The main objective of this work was to investigate the application of supercritical carbon dioxide as anti-solvent for the encapsulation of β-carotene in poly(hydroxybutirate-co-hydroxyvalerate) (PHBV) with dichloromethane as organic solvent using the Solution Enhanced Dispersion by Supercritical fluids (SEDS) technique. For the precipitation experiments with pure compounds the parameters investigated were the concentration of β-carotene (4 and 8 mg mL⁻¹) and PHBV (30 mg mL⁻¹) in the organic solution, pressure (from 80 to 200 bar), solution flow rate fixed at 1 mL min⁻¹, anti-solvent flow rate at 40 mL min⁻¹ and constant temperature of 313 K. Pure β-carotene precipitation indicates that an increase in pressure led in most cases to particles with larger sizes, while the opposite trend was verified for pure PHBV precipitation. The morphology of precipitated PHBV particles was spherical and was not influenced by increasing pressure. The morphology of β-carotene microparticles changed from plate-like to leaf-like particles when raising operational pressure, but was not influenced by its concentration in the organic solution as verified by micrographs of scanning electronic microscopy (SEM). For the co-precipitation experiments it was evaluated the effect of β-carotene concentration (2-30 mg mL⁻¹) in the organic solution, at fixed parameters: PHBV concentration (30 mg mL⁻¹) in organic solution, temperature at 313 K, pressure at 80 bar, solution flow rate at 1 mL min⁻¹ and anti-solvent flow rate at 40 mL min⁻¹. The encapsulation data showed that increasing the concentration of β-carotene, keeping fixed the PHBV content, results in higher percentage of solute encapsulated, increasing the encapsulation efficiency.     

Proximal effects of ultraviolet light absorbers and polymer matrix in the photostability of β-carotene

β-Carotene was used as a probe to investigate the protection offered by 2-ethylhexyl 4-methoxycinnamate, a photostabilizer, upon ultraviolet-A photodegradation. β-Carotene and 2-ethylhexyl 4-methoxycinnamate were arranged in two distinct macroscopic configurations (core/shell and homogenous) in solution with tandem and single cuvettes. 2-Ethylhexyl 4-methoxycinnamate was also combined with poly(methyl methacrylate) in solution to investigate the protective synergy between the photostabilizer and the polymer matrix. The choice of configuration played a more dominant role than the concentration of 2-ethylhexyl 4-methoxycinnamate in the degradation of β-carotene, with β-carotene remaining more stable in the homogeneous configuration. Changing configurations yielded different proximities of 2-ethylhexyl 4-methoxycinnamate to β-carotene; closing the proximity increased the potential close interactions (<1 nm) where transfer of excited state energy from β-carotene to 2-ethylhexyl 4-methoxycinnamate could occur resulting in increased photostability. The addition of poly(methyl methacrylate) had a negligible impact on the decay of β-carotene in both configurations.     

Kinetic model for autoxidation of β-carotene in organic solutions

Autoxidation of β-carotene was studied experimentally using n-decane as a solvent under various reaction conditions of temperature and dissolved oxygen concentration A novel kinetic model was proposed on the basis of an autocatalytic free-radical chain reaction mechanism. A secondary initiation reaction by decomposition of hydroperoxide and reactions concerned with a β-carotene-derived C-centered radical in propagation and termination processes were taken into consideration in the model. There were four unknown kinetic constants, and the constants were estimated by fitting the model with the experimental data. The fitted results are in good agreement with the experimental data in all stages of the kinetics of autoxidation and over a wide range of oxygen concentrations. The model described not only the appearance of the induction stage but also the effect of the oxygen concentration on the autoxidation rate. In addition, the model predicted the behavior of autoxidation in another solvent at low temperature that had been reported by other researchers.     

The measurement of the solubility of electrolytes in water—miscible organic solvent mixture by using the “solventing out” process

Twenty water—MOS-electrolyte systems were studied. An analytical expression which describes the relative solubility S/S^w as a function of the MOS amount, v, was found. Expressions for predicting the solubility constants λ and v₀/1 + v₀ from precipitation constants were found. These constants are applicable to the entire range, in most cases, and applicable for most of the range in other cases.     

Tribological behaviors of B4C–SiC composites self-mated pairs in seawater and pure water

In this paper, the tribological behaviors of B₄C–SiC composites self-mated pairs in seawater and pure water were investigated, respectively. The results showed that the B₄C–SiC composite with the content of 20%SiC has good mechanical properties. For the B₄C–20%SiC self-mated pair in seawater, the abrasive wear is greatly weakened, and the tribo-chemical reactions between the composite surface and water molecules occurred. The tribo-chemical polishing causes very smooth wear surfaces, and the sliding pairs enter to the status of liquid lubrication. An extremely low friction coefficient (0.038) and wear rate (both below the order of magnitude 10⁻⁵ mm³/N m) were obtained in this study. Due to the lower viscosity of pure water, the load carrying capacity of the liquid film reduces. So, in pure water, the sliding pair shows slightly higher friction coefficient and wear rate than that in seawater.     

Experimental and numerical study of stratified viscous oil–water flow

Stratified two-phase flows of oil and water are important to the energy industry, and models capable of predicting this type of flow are primordial. Many studies focus on fluids with low viscosity, but a high viscosity oil in the mixture significantly changes its behavior. We gathered experimental data of pressure drop, volumetric fractions, and flow-pattern data of a stratified liquid–liquid flow with high viscosity ratio. In addition, a wire-mesh sensor provided tomographic views of the flow. The data were compared with computational fluid dynamics (CFD) models using OpenFOAM and a one-dimensional model. CFD simulations used an interface capturing method, and turbulence damping was introduced to avoid high eddy viscosity at the interface region. Reynolds Average Navier–Stokes and large eddy simulations were used to account for turbulence, and they showed significant differences. The comparisons showed good overall results for pressure drop, volumetric fractions, and phase distributions between CFD and experiments.     

Quantitative determination of 13C-labeled and endogenous β-carotene, lutein, and vitamin A in human plasma

Quantitative procedures employing liquid-chromatography/particle beam mass spectrometry (LC/PB-MS) and gas chromatography-mass spectrometry (GC-MS) were applied to the determination of the endogenous and ¹³C-labeled β-carotene, lutein, and retinol in plasma of a subject who consumed kale (Brassica oleracea) that had been grown in a ¹³CO₂-enriched atmosphere. All compounds were analyzed in the negative chemical ionization (NCI) mode using methane as the moderating reagent gas. β-Carotene and lutein were analyzed using LC/PB-MS applying reversed-phase high-performance liquid chromatography (HPLC) separation procedures to resolve the analytes. The concentrations of the β-carotene isotopomers in the plasma over a several-week period were determined using ²H₈-β-carotene as an internal standard. The total plasma concentrations of all trans-lutein were quantified by HPLC analysis with a photodiode array detector using β-apo-8′-carotenal as an internal standard, and the ratio of the ¹³C∶¹²C isotopomers of lutein was determined by PB-MS. The retinol isotopomers were collected from individual HPLC fractions of the plasma extract and then analyzed as the trimethylsilyl ethers by GC-MS in the NCI mode. The ¹³C-and ¹²C-retinol isotopomers were quantified using ²H₄-retinol as an internal standard. These methods demonstrate the application of highly sensitive procedures empolying NCI MS for the quantitative determination of carotenoids and vitamin A for the purpose of conducting metabolism studies of phytonutrients.     

Solubility measurement and thermodynamic modeling of carbamazepine(form Ⅲ) in five pure solvents at various temperatures

In this work, the solubilities of carbamazepine(CBZ)(form Ⅲ) in ethyl acetate, methyl acetate, ethylene glycol, chloroform and cyclohexylamine were determined by laser monitoring techniques at pressure above sea level, and the solubility data of CBZ(form Ⅲ) in different pure solvents were fitted by the Modified Apelblat model and λh model. The result shows that the solubility of CBZ(form Ⅲ) in five solvents increases as temperature rises, and the solubility in chloroform was the largest. The experimental solubility values of CBZ(form Ⅲ) in ethyl acetate, methyl acetate, chloroform and cyclohexylamine were in better agreement with the simulated fitting values of the λh model. For ethylene glycol, the r value was much larger than the other four solvents, and it can be seen from the λh model that ethylene glycol was closer to the ideal solution system than the other four solvents.     

Inhibitory effect of 1,3-diglycerides during adsorption of β-carotene onto attapulgite and sepiolite

The adsorption isotherms of β-carotene on attapulgite and sepiolite were measured in the presence of 1,3-diglyceride in n-hexane to elucidate the relative inhibitory power of the diglycerides, hydroxyl group, carbon number, and double bond for adsorption bleaching. The adsorption mode of β-carotene was the Langmuir type. The inhibition of β-carotene adsorption may be caused by the polarity of diglycerides and the formation of diglyceride micelles. The relative inhibitory power of 1,3-diolein, 1,3-distearin, and 1,3-dipalmitin toward β-carotene adsorption was 1.49, 1.40, and 0.99, respectively. Therefore, the relative inhibitory power due to the hydroxyl group and increase in the carbon atom of the fatty acid in glyceride was 0.41–0.49.     

Crystallization of β-carotene by a GAS process in batch Effect of operating conditions

β-carotene has been successfully recrystallized from ethyl acetate and dichloromethane solutions using carbon dioxide as antisolvent in a batch bench plant for GAS process. The aim of this work is to study the influence of operating variables (concentration, temperature, stirring rate and type of solvent) and the efficiency of the GAS process on final size of the crystals. Crystals smaller than 1 μm are obtained at temperature of 298 K, pressure of 5.8 MPa, from 1 g/l solutions and with a stirring rate of 25 Hz. GAS process yields trans isomer with high efficiency separation. Solubility of β-carotene in CO₂ plus ethyl acetate at different temperatures (298, 313 and 333 K) from 4.3 to 9.8 MPa were measured, values ranged between 0.45 (P=7.2 MPa, T=333 K) and 0.010 g/l (P=8.1 MPa, T=313 K). In addition, distribution and size of the crystals from raw and recrystallized β-carotene for the CO₂–ethyl acetate system are studied.     

Measurement and correlation for solubility of diosgenin in some mixed solvents简

The solubility data of diosgenin in mixed systems of ethanol ＋ 1-propanol （1 ： 1）, ethanol ＋ 1-butanol （1 ： 1）, ethanol ＋ isobutyl alcohol （1 ： 1）, methanol ＋ isobutyl alcohol （1 ： 1）, methanol ＋ isobutyl alcohol （1 ： 4）, ethanol ＋ 1-pentanol （1 ： 1） and carbon tetrachloride were measured over the temperature range from 289.15 K to 334.15 K by a laser monitoring observation technique at atmospheric pressure, with all mixtures mixed by volume ratio. The Apelblat equation, the ideal solution model, and the 2h equation are used to correlate the solubility data. The results show that the three models agree well with the experimental data, providing essential support for industrial design and further theoretical study.     

Oxidation behavior of sintered tubular silicon carbide in pure steam ΙΙ: Weight-loss correlation developments

Correlations for weight loss rate of pressureless sintered SiC with steam flow velocity, and temperature in pure steam at atmospheric pressure in laminar flow with a velocity range of 0.8–10 m/s and a temperature range of 1140–1500 °C have been developed. While preserving physical significance of non-dimensional numbers dictating boundary layer mass transfer phenomena, the correlations capture boundary layer diffusion effects on the SiO₂ volatilization rate, which is affected by flow characteristics at the oxidizing surface. A correlation representing the additive resistances of the mass diffusion in the boundary layer and the volatilization reaction is found to best fit the experimental data. The developed correlations should help understand the SiO₂ volatilization mechanism in steam, as well as predicting the lifetime of pressureless sintered SiC in oxidizing environments.     

Oxidative degradation kinetics of lycopene, lutein, and 9-cis and all-trans β-carotene

The thermal and oxidative degradation of carotenoids was studied in an oil model system to determine their relative stabilities and the major β-carotene isomers formed during the reaction. All-trans β-carotene, 9-cis β-carotene, lycopene, and lutein were heated in safflower seed oil at 75, 85, and 95°C for 24, 12, and 5 h, respectively. The major isomers formed during heating of β-carotene were 13-cis, 9-cis, and an unidentified cis isomer. The degradation kinetics for the carotenoids followed a first-order kinetic model. The rates of degradation were as follows: lycopene>all-trans β-carotene≈9-cis β-carotene>lutein. The values for the thermodynamic parameters indicate that a kinetic compensation effect exists between all of the carotenoids. These data suggest that lycopene was most susceptible to degradation and lutein had the greatest stability in the model system of the carotenoids tested. Furthermore, there was no significant difference in the rates of degradation for 9-cis and all-trans β-carotene under the experimental conditions.