Solubilization of Trans-Resveratrol in Some Mono-Solvents and Various Propylene Glycol + Water Mixtures

This research deals with the determination of solubility, Hansen solubility parameters, dissolution properties, enthalpy–entropy compensation, and computational modeling of a naturally-derived bioactive compound trans-resveratrol (TRV) in water, methanol, ethanol, n-propanol, n-butanol, propylene glycol (PG), and various PG + water mixtures. The solubility of TRV in six different mono-solvents and various PG + water mixtures was determined at 298.2–318.2 K and 0.1 MPa. The measured experimental solubility values of TRV were regressed using six different computational/theoretical models, including van’t Hoff, Apelblat, Buchowski–Ksiazczak λh, Yalkowsly–Roseman, Jouyban–Acree, and van’t Hoff–Jouyban–Acree models, with average uncertainties of less than 3.0%. The maxima of TRV solubility in mole fraction was obtained in neat PG (2.62 × 10⁻²) at 318.2 K. However, the minima of TRV solubility in the mole fraction was recorded in neat water (3.12 × 10⁻⁶) at 298.2 K. Thermodynamic calculation of TRV dissolution properties suggested an endothermic and entropy-driven dissolution of TRV in all studied mono-solvents and various PG + water mixtures. Solvation behavior evaluation indicated an enthalpy-driven mechanism as the main mechanism for TRV solvation. Based on these data and observations, PG has been chosen as the best mono-solvent for TRV solubilization.     

Solubility of Cinnarizine in (Transcutol + Water) Mixtures: Determination,Hansen Solubility Parameters,Correlation, and Thermodynamics

Between 293.2 and 313.2 K and at 0.1 MPa, the solubility of the weak base, cinnarizine (CNZ) (3), in various {Transcutol-P (TP) (1) + water (2)} combinations is reported. The Hansen solubility parameters (HSP) of CNZ and various {(TP) (1) + water (2)} mixtures free of CNZ were also predicted using HSPiP software. Five distinct cosolvency-based mathematical models were used to link the experimentally determined solubility data of CNZ. The solubility of CNZ in mole fraction was increased with elevated temperature and TP mass fraction in {(TP) (1) + water (2)} combinations. The maximum solubility of CNZ in mole fraction was achieved in neat TP (5.83 × 10⁻² at 313.2 K) followed by the minimum in neat water (3.91 × 10⁻⁸ at 293.2 K). The values of mean percent deviation (MPD) were estimated as 2.27%, 5.15%, 27.76%, 1.24% and 1.52% for the “Apelblat, van’t Hoff, Yalkowsky–Roseman, Jouyban–Acree, and Jouyban–Acree–van’t Hoff models”, respectively, indicating good correlations. The HSP value of CNZ was closed with that of neat TP, suggesting the maximum solubilization of CNZ in TP compared with neat water and other aqueous mixtures of TP and water. The outcomes of the apparent thermodynamic analysis revealed that CNZ dissolution was endothermic and entropy-driven in all of the {(TP) (1) + water (2)} systems investigated. For {(TP) (1) + water (2)} mixtures, the enthalpy-driven mechanism was determined to be the driven mechanism for CNZ solvation. TP has great potential for solubilizing the weak base, CNZ, in water, as demonstrated by these results.     

Solubility Determination of c-Met Inhibitor in Solvent Mixtures and Mathematical Modeling to Develop Nanosuspension Formulation

The solubility and dissolution thermodynamics of new c-Met inhibitor, ABN401, were determined in eleven solvents and Transcutol^® HP–water mixture (TWM) from 298.15 to 318.15 K. The experimental solubilities were validated using five mathematical models, namely modified Apelblat, van’t Hoff, Buchowski–Ksiazaczak λh, Yalkowsky, and Jouyban–Acree van’t Hoff models. The experimental results were correlated and utilized further to investigate the feasibility of nanosuspension formation using liquid anti-solvent precipitation. Thermodynamic solubility of ABN401 increased significantly with the increase in temperature and maximum solubility was obtained with Transcutol^® HP while low solubility in was obtained water. An activity coefficient study indicated that high molecular interaction was observed in ABN401–Transcutol^® HP (THP). The solubility increased proportionately as the mole fraction of Transcutol^® HP increased in TWM, which was also supported by a solvent effect study. The result suggested endothermic and entropy-driven dissolution. Based on the solubility, nanosuspension was designed with Transcutol^® HP as solvent, and water as anti-solvent. The mean particle size of nanosuspension decreased to 43.05 nm when the mole fraction of ABN401 in THP, and mole fraction of ABN401 in TWM mixture were decreased to 0.04 and 0.1. The ultrasonicated nanosuspension appeared to give comparatively higher dissolution than micronized nanosuspension and provide a candidate formulation for in vivo purposes.     

Interactions between AuCl<Subscript>4</Subscript><Superscript>−</Superscript> and CTA<Superscript>+</Superscript> ions in water

The solubility of hexadecyltrimethylammonium tetrachloroaurate (CTA·AuCl₄) in water was measured at different temperatures of 288.2, 293.2, 298.2, 303.2, and 308.2 K. The enthalpy change associated with the formation of the CTA·AuCl₄ precipitate was estimated on the basis of the van’t Hoff equation and was found to be −42.5 ± 2.8 kJ mol⁻¹ at 298.2 K. The calorimetric enthalpy change for the CTA·AuCl₄ precipitate formation was directly determined by isothermal titration calorimetry performed at 298.2 K and was found to agree well with that estimated from the van’t Hoff equation.     

Solubility and Raman Spectroscopic Study of As(III) Speciation in Organic Compound-Water Solutions. A Hydration Approach for Aqueous Arsenic in Complex Solutions

Solubilities of arsenolite (As₂O₃, cub.) were measured from 22 to 90°C in water–acetone, water–acetic acid, and water—formic acid solutions of compositions ranging from the pure organic compound to pure water. Raman spectra were obtained at ambient temperature on As-containing water–acetic acid and water–acetone solutions. Results show that arsenic solvation by these organic compounds is negligible and hydroxide species dominate As speciation over a wide range of water activity (a_{H 2 O}> 0.01). The solubility data were analyzed using an approach based on stoichiometric hydration reactions. Results show that As₂O₃ solubility can be described as a function of water activity, independently of the nature of the organic compound, by involving two neutral As hydroxide complexes: As(OH)₃ and As(OH)₃·4H₂O. Stability constants derived for these species indicate that hydration weakens with increasing temperature. Calculations using these constants show that at low temperatures the tetrahydrate As(OH)₃·4H₂O is dominant in water-rich solutions; by contrast, in high-temperature crustal fluids, As(OH)₃ becomes the major As species. The proposed hydration model can be used to analyze solubility of arsenic-bearing minerals and arsenic transport in complex H₂O–CO₂—electrolyte solutions encountered in natural and industrial environments.     

Solubility and preferential solvation of indomethacin in 1,4-dioxane + water solvent mixtures

The solubilities of indomethacin (IMC) in 1,4-dioxane + water cosolvent mixtures were determined at several temperatures, 293.15–313.15 K. The thermodynamic functions: Gibbs energy, enthalpy, and entropy of solution and of mixing were obtained from these data by using the van’t Hoff and Gibbs equations. The solubility was maximal in 0.95 mass fraction of 1,4-dioxane and very low in pure water at all the temperatures. A non-linear plot of ΔH_soln ° vs. ΔG_soln ° with negative slope from pure water up to 0.60 mass fraction of 1,4-dioxane and positive beyond this up to 0.95 mass fraction of 1,4-dioxane was obtained. Accordingly, the driving mechanism for IMC solubility in water-rich mixtures is the entropy, probably due to water-structure loss around the drug non-polar moieties by 1,4-dioxane, whereas, above 0.60 mass fraction of 1,4-dioxane the driving mechanism is the enthalpy, probably due to IMC solvation increase by the co-solvent molecules. The preferential solvation of IMC by the components of the solvent was estimated by means of the quasi-lattice quasi-chemical method, whereas the inverse Kirkwood-Buff integral method could not be applied because of divergence of the integrals in intermediate compositions.     

Solubility and transport of water vapor in some 6FDA-based polyimides

Permeability, diffusion, and solubility coefficients for H₂O vapor in four different 6FDA-based polyimides were determined at temperatures between 25 and 45°C and over a wide range of relative humidities. The solubility of H₂O vapor in some of the polyimides studied can be described by the “dual-mode sorption” model whereas in other polyimides it is represented by the Flory-Huggins equation, which suggests that the latter polymers are plasticized by H₂O. The solubility of H₂O vapor in the polyimides decreases as the temperature is raised and increases with increasing polarity of the polymer. The diffusion coefficients for H₂O in the polyimides studied either increase or pass through a weak maximum with increasing H₂O activity, or concentration in the polymers. The latter behavior is probably due to a clustering of H₂O molecules in the polyimides at higher H₂O activities or concentrations. The diffusion coefficients for H₂O decrease as the chain-packing density of the polyimides increases. The permeability coefficients for H₂O vapor in 6FDA-based polyimide membranes either increase slightly or are constant as the H₂O activity is increased. The experimental values of the permeability coefficients are consistent with the values determined from diffusion and solubility coefficients. The permeability of the polyimides to H₂O vapor appears to be controlled by the solubility of H₂O in the polymers. The polyimides studied exhibit a very high selectivity for H₂O vapor relative to CH_4, and therefore are potentially useful membrane materials for the dehydration of natural gas. ©1995 John Wiley & Sons, Inc.     

(Liquid + liquid) equilibria of the (water + acetic acid + dibasic esters mixture) system

(Liquid + liquid) equilibrium (LLE) data for the {water + acetic acid + dibasic esters mixture (dimethyl adipate + dimethyl glutarate + dimethyl succinate)} system have been determined experimentally at T = (298.2, 308.2, and 318.2) K. Complete phase diagrams were obtained by determining solubility curve and tie-line data. The reliability of the experimental tie-line data was confirmed by using the Othmer-Tobias correlation. The UNIFAC model was used to predict the phase equilibrium in the system using the interaction parameters determined from experimental data between CH₂, CH₃COO, CH₃, COOH, and H₂O functional groups. Distribution coefficients and separation factors were compared with previous studies.     

Hydrophobic interaction chromatography of proteins: Thermodynamic analysis of conformational changes

For BSA and β-lactoglobulin adsorption to hydrophobic interaction chromatography (HIC) stationary phases leads to conformational changes. In order to study the enthalpy (ΔH_ads), entropy (ΔS_ads), free energy (ΔG_ads) and heat capacity (Δc_p,ads) changes associated with adsorption we evaluated chromatographic data by the non-linear van’t Hoff model. Additionally, we performed isothermal titration calorimetry (ITC) experiments. van’t Hoff analysis revealed that a temperature raise from 278 to 308 K increasingly favoured adsorption seen by a decrease of ΔG_ads from −12.9 to −20.5 kJ/mol for BSA and from −6.6 to −13.2 kJ/mol for β-lactoglobulin. Δc_p,ads values were positive at 1.2 m (NH₄)₂SO₄ and negative at 0.7 m (NH₄)₂SO₄. Positive Δc_p,ads values imply hydration of apolar groups and protein unfolding. These results further corroborate conformational changes upon adsorption and their dependence on mobile phase (NH₄)₂SO₄ concentration. ITC measurements showed that ΔH_ads is dependent on surface coverage already at very low loadings. Discrepancies between ΔH_ads determined by van’t Hoff analysis and ITC were observed. We explain this with protein conformational changes upon adsorption which are not accounted for by van’t Hoff analysis.     

Solubility and Solution Thermodynamic Properties of 4-(4-Hydroxyphenyl)-2-butanone (Raspberry Ketone) in Different Pure Solvents

The solubility of 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone) in six pure solvents was experimentally determined at temperatures ranging from 283.15 to 313.15 K under the pressure 0.10 MPa by employing a gravimetrical method. The experimental results indicate that the solubility of raspberry ketone in all studied solvents is temperature dependent, a rise in temperature brings about an increase in solubility. The experimental solubility data of raspberry ketone in six pure solvents (acetone, ethanol, ethyl acetate, n-propyl alcohol, n-butyl alcohol, and distilled water) was correlated by using several commonly used thermodynamic models, including the Apelblat, van’t Hoff and λh equations. The results of the error analysis indicate that the van’t Hoff equation was able to give more accurate and reliable predictions of solubility with root-mean-square deviation less than 0.56%. Furthermore, the changes of dissolution enthalpies (Δ_diss H°), dissolution entropies (Δ_diss S°) and dissolution Gibbs energies (Δ_diss G°) of raspberry ketone in the solvents studied were estimated by the van’t Hoff equation. The positive value of Δ_diss H°, Δ_diss S°, and Δ_diss G° indicated that these dissolution processes of raspberry ketone in the solvents studied were all endothermic and enthalpy-driven.     

Solubility of Crystalline Calcium Isosaccharinate

The solubility of calcium isosaccharinate Ca(ISA)₂(c) was determined at 23°C as a function of pH (1–14) and calcium ion molality (0.03–0.52). The similarity of solubility from the over- and undersaturation directions for different equilibration periods indicated that equilibrium in these solutions was reached rapidly (< 7 days) and that these data can be used to develop thermodynamic equilibrium constants. The solubility data were interpreted using the Pitzer ion–interaction model. The logarithms of the thermodynamic equilibrium constants determined from these data were 1.30 for the dominant reaction at pH < 4.5 [Ca(ISA)₂(c) + 2H⁺ Ca²⁺ + 2HISA(aq)], and –2.22 for the dominant reaction at 4.5 [Ca(ISA)₂(c)+ Ca(ISA)₂(aq)]. In addition, the logarithm of the dissociation constant of HISA [HISA(aq) ISA- + H⁺] was calculated to be –4.46.     

Identification of Saturating Solid Phases in the System Ce2(SO4)3-H2O from the Solubility Data

Saturating solid phases, Ce₂(SO₄)₃·hH₂O, with hydrate numbers h equal to 12, 9, 8, 5, 4 and 2, have been identified by critical evaluation of the solubility data in the system Ce₂(SO₄)₃—H₂O over the temperature range 273–373 K. The results are compared with the respective TG—DTA—DSC and X-ray data. The solubility smoothing equations, transition points and solution enthalpy estimators of the identified hydrates are given. The stable equilibrium solid phases are concluded to be only Ce₂(SO₄)₃·9H₂O at 273–310 K, Ce₂(SO₄)₃·4H₂O at 310–367 K and Ce₂(SO₄)₃·2H₂O at 367–373 K. Divergencies of up to 185% in the reported solubility data are mainly due to a variety of metastable equilibria involved in the close crystallization fields, and incorrect assignments of the saturating solid phases. Since a similar variety of the hydrate numbers exists for the analogous La(III) system, it most probably also occurs for the corresponding Pu(III), Np(III) and U(III) systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Solubility of carbon dioxide,methane, and propane in silicone polymers. Effect of polymer backbone chains

The solubility of carbon dioxide, methane, and propane in poly(dimethyl silmethylene) [(CH₃)₂SiCH₂]_x and poly(tetramethyl silhexylene siloxane) [(CH₃)₂Si (CH₂)₆Si (CH₃)₂O]_x was measured in the temperature range from 10.0 to 55.0°C and at elevated pressures. The present results are compared with similar measurements made with other silicone polymers. At a given temperature and pressure, the solubility of the above three gases is highest in poly(dimethyl siloxane) (Me₂SiO)_x. The gas solubility is decreased by either backbone-chain or side-chain substitutions of functional groups in (Me₂SiO)_x which increase the stiffness of the polymer chains and decrease the specific or fractional free volume of the polymers. It is conjectured that a decrease in the free volume of silicone polymers has a greater effect in decreasing the gas solubility than differences in gas/polymer interactions [with the exception of specific interactions (e.g., between CO₂ and polar groups in the polymer)]. © 1993 John Wiley & Sons, Inc.     

Solubility of bosentan in {propylene glycol + water} mixtures at various temperatures: experimental data and mathematical modelling

Solubility measurements were performed for bosentan (BST) in binary mixtures of propylene glycol (PG) and water at atmospheric pressure within the temperature range, T = 293.2 – 313.2 K by employing a shake-flask method. Generated solubility data were correlated with Jouyban-Acree-van’t Hoff model and the accuracies of the predicted solubilities and model performance were illustrated by mean relative deviations (MRD). Furthermore, the apparent thermodynamic properties of BST dissolving in all the mixed solvents were calculated, and the obtained results show that the dissolution process is endothermic. By using the inverse Kirkwood–Buff integrals, it was observed that BST is preferentially solvated by water in water-rich solvent mixtures and preferentially solvated by PG (as a cosolvent) in the composition range of 0.20 < x₁ < 1.00 at 298.2 K.     

Solubility of carboxylic acids in a matrix of uncross-linked polystyrene

Solubility diagrams of a series of carboxylic acids in a matrix of linear polystyrene have been measured using a gravimetric method on samples immersed in solvent, as reported earlier [Bernardo G, Vesely D. Eur Polym J 2007;43:938-48]. The results show that the amount of solvent, swelling the polymer, reaches an equilibrium saturation which has a unique and reproducible value for each system and temperature. An analysis based on Flory-Huggins theory shows that all data presented here can be well interpreted with an interaction parameter in a simple form: χ = a + (b/T). An excellent fit can also be obtained using the van’t Hoff equation. An analysis based on total and partial (Hansen) solubility parameters has also been investigated.     

Applcation of the Pitzer equations to the solubility of ternary aqueous nitrate solutions at 25°C

The solubilities of the ternary systems Cu(NO₃)₂–Ca(NO₃)₂–H₂O and Cu(NO₃)₂–Mg(NO₃)₂–H₂O at 25°C were calculated from the solubility data for the binary systems by using the Pitzer equations. The calculated solubility isotherms were confirmed experimentally. The activity coefficients of the components, the osmotic coefficient, and the activity of water were calculated from the experimental isotherms.     

Solubility of gallium(III) oxyhydroxide in aqueous NaCl solutions at 100°C

The hydrolysis-precipitation equilibrium reaction of aqueous gallium(III) solution was investigated in 0–3 mol-kg^-1 NaCl media at low pH at 100°C using a pressure-tight glass vessel. All precipitates were identified as GaOOH. The results were analyzed with a nonlinear least-squares computer program to obtain the solubility product K_so for gallium(III) oxyhydroxide using a single-parameter type of Debye-Hückel equation. The value of log K_so for GaOOH(s) + 3H⁺ ⇆ Ga³⁺ + 2H₂O was -0.60 at 100°C. The solubility product calculated from thermodynamic data was compared with the experimental result.     

Hydrogen determinations in a zirconium based alloy with a DSC

In the present work a method to measure hydrogen concentrations in zirconium-based alloys was developed measuring simultaneously both, the temperature of terminal solid solubility, T_TSSd, and the hydride dissolution heat, Q_δ→α, using a differential scanning calorimeter (DSC). The hydrogen concentration measured with that technique, [H]_Q, and the values obtained with a standard hydrogen gas meter, [H]_HGM, shows a linear relation: [H]_Q = (1.00 ± 0.03)[H]_HGM| + (9.2 ± 8.0) with a correlation factor of 0.99 in the entire solubility interval in the αZr phase, from 15 to 650 wt. ppm-H. The mean enthalpy value determined with two different criteria for T_TSSd and Q_δ→α measurements is  kJ/mol H. The present method is specially appropriate for alloys where a partition of the overall hydrogen concentration in two phases exists. It is applicable to all hydride forming metals which ideally follows the van’t Hoff law.     

Ion-Interaction Approach: Pressure Effect on the Solubility of Some Minerals in Submarine Brines and Seawater

The pressure dependence of salt solubility in multiple electrolyte solutions was estimated to 1000 atm. The activity coefficients, thermodynamic solubility products, degrees of saturation, and mineral solubility were calculated with high precision only up to 300 atm because of the absence of compressibility data for mixed electrolyte solutions. The ion-interaction approach developed during the last 2 decades allows the prediction of various thermodynamic properties, including volumetric ones for multiple-solute natural solutions. This approach was applied to the estimation of the depth dependence of solubility for certain evaporite minerals in natural brines. The influence of pressure on solubility products, mean activity coefficients, and degrees of saturation of minerals, such as, halite (NaCl), anhydrite (CaSO₄), gypsum (CaSO₄·2 H₂O), celestite (SrSO₄), and barite (BaSO₄) were calculated for in situ depths in the Orca Basin (Gulf of Mexico), the Tyro and Bannock II depressions (the Mediterranean Sea), and for average seawater.     

Solubility of Lithium Monoborate in High-Temperature Water

The solubility in water of anhydrous lithium monoborate has been determinedat 300 to 360°C. Equilibrium constants for the isocoulombic solubilityreactionLiBO₂ (s) + H⁺ (aq) + H₂O (1) = Li⁺ (aq) + H₃BO₃ (aq)have been calculated from measured concentrations of total B and total Li insolution. These high-temperature constants can be fitted by a three-term equationthat is consistent with thermodynamic data at 25°C. The heat capacity changefor the isocoulombic reaction is small and independent of temperature. Solubilityresults agree with unpublished measurements from early work on developmentof nuclear power. Solubilities reported by Bouaziz appear to be much too highand may apply to a hydrated phase.