Hoff Equation Research Articles

Dissolution thermodynamics and preferential solvation of genistein in some (ethanol + water) mixtures at different temperatures

The solubility of genistein was measured in the binary system of ethanol and water at temperatures ranging from 288.2 to 328.2 K. The obtained data were correlated with the modified Apelblat model, Yalkowsky model, λh model, CNIBS/R-K model, Jouyban-Acree-van’t Hoff model, and modified Wilson model and their prediction accuracy was evaluated by calculating the mean relative deviation. The thermodynamic functions, Gibbs energy, enthalpy, and entropy of solution were determined using van’t Hoff equation. Moreover, the preferential solvation was analyzed by using the solubility data at 298.2 K. The solubility of genistein in the system increased with an increase in temperature and mole fraction of ethanol in the solvent mixtures. The values for solubility of genistein are ranging from 0.47 obtained in neat water at T = 288.2 K to 5.02 obtained in absolute ethanol at T = 328.2 K. The values of Δ solnG, 0 Δ solnH0 and Δ solnH0 for the dissolution of genistein in mixtures are positive, whereas the values of Δ solnH0 in neat water and absolute ethanol are negative. The thermodynamic properties of dissolution suggest that the dissolution process is non-spontaneous and endergonic. The modified Apelblat model can provide more accurate predictive solubility of genistein in the water and ethanol mixtures, whereas Yalkowsky model calculates solubility of genistein with large deviations. Genistein is preferentially solvated by water in water-rich mixtures (0 < x 2 < 0.24) but preferential solvation by ethanol in the region of 0.24 < x 2 < 1. Overall, this work could be applied for designing and optimizing the extraction, purification, and crystallization process of genistein.

Membrane behavior of clay considering the effect of fixed charges

Membrane efficiency coefficient of clay is evaluated with considering the effect of fixed charges adsorbed on clay mineral surfaces. By virtue of the concept of chemical potential, the ionic concentration of pore water is calculated. An equation is first proposed to calculate the Donnan osmotic pressure based on the activity of water (H2O), and then a new method is developed to determine the membrane efficiency coefficient, based on the theoretical chemo-osmotic pressure difference. The proposed method is used to calculate the membrane efficiency coefficients of geosynthetic clay liners (GCLs) with different bentonite contents and porosities under different KCl concentrations. The calculated results are compared to those of van't Hoff equation, showing that if skeletal deformation is excluded, the proposed model and van't Hoff equation with average ion concentration difference yield practically the same results; if the deformation is considered, however, van't Hoff equation yields smaller membrane coefficients.

Blowing-up solutions for time-fractional equations on a bounded domain

This paper proposes initial-boundary value problems for time-fractional analogs of Kuramoto-Sivashinsky, Korpusov-Pletner-Sveshnikov, Cahn-Allen, and Hoff equations due to a bounded domain. Adequate conditions for the blowing-up of solutions in limited time of previously mentioned conditions are displayed. The Pohozhaev nonlinear capacity strategy is considered. Illustrative examples are given for each of the investigated equations. (2010) Mathematics Subject Classifications: 34A08; 34B25; 34B15.

Solubility measurement, correlation, thermodynamic analysis and molecular simulation of 1-nitronaphthalene in twelve pure solvents

The solid–liquid equilibrium data of 1-nitronaphthalene in twelve pure solvents (methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, acetone, acetonitrile, dichloromethane, methyl acetate, ethyl acetate and cyclohexane) were systematically determined by isothermal saturation method in the temperatures ranging from 273.15 K to 308.15 K under atmospheric pressure (0.1 MPa). Molecular electrostatic potential surface and Hirshfeld surface analysis were applied to obtain the visual analysis of crystal structure and the overall charge distribution. The effect of solvent multiple physicochemical factors including polarity, hydrogen bond donor, hydrogen bond acceptor and cohesive energy density of solvent was explored to the solubility behavior. Then the experimental solubility data were correlated by the modified Apelblat equation, λh equation, Van't Hoff equation and Wilson model, the ARD% was used to check the accuracy of the four equations and the modified Apelblat showed the best fitting. Furthermore, the mixing thermodynamic properties were calculated based on Wilson model, which indicates the dissolution of 1-nitronaphthalene is a spontaneous, endothermic and entropy-driving process. Finally, molecular dynamic simulations were employed to further analyze the dissolution behavior from solute-solvent interaction perspective.

Solubility analysis of 18 active pharmaceutical ingredients and intermediates in the non-polar solvents dioxane, toluene and cyclopentyl methyl ether

The temperature dependent solubility of 18 organic compounds, of which some are active pharmaceutical ingredients, was measured in 1,4-dioxane, toluene and cyclopentyl methyl ether over a temperature range between 0 and 70 °C using a turbidity method. The solubility of the studied compounds in the three solvents increases with temperature in all binary solute-solvent systems, and all compounds exhibit a higher solubility in 1,4-dioxane than in toluene and cyclopentyl methyl ether. The non-ideal behaviour of the binary systems was evaluated in terms of the activity coefficient. All the compounds in toluene presented a positive deviation from ideal solution, while both positive and negative deviations were observed for the model compounds in the other two apolar solvents. From the solubility and the activity coefficient, a number of thermodynamic models including van’t Hoff, Apelblat, λh, Margules, van Laar, Wilson, and the Non-Randomness Two Liquids (NRTL) were used for the correlation of the experimental data. The NRTL and the van’t Hoff equations present closer overall correlations, while the Margules and the λh models show deviations >5 % for several compounds in the three solvent systems. The mixing thermodynamic properties of the several solute-solvent systems were further analyzed by the van ‘t Hoff and Wilson equations for a better understanding of the solution behaviour. The analysis revealed systems with apparent ideal behaviour where counteracting non-ideality effects cancel each other’s.

Investigation of solid–liquid equilibrium and thermodynamic models of D-Tagatose in mono-solvents and binary solvents

As a rare sugar, D-Tagatose is regarded as an excellent low-energy food sweetener. It is especially beneficial for physical health, such as inhibiting hyperglycemia, improving intestinal flora, and avoiding caries. It is broadly employed in food, medicine, cosmetics, and other fields. Acquiring D-Tagatose solubility is vital to develop D-Tagatose crystallization process to obtain high-quality D-Tagatose production. In this study, the solubility of D-Tagatose in seven pure solvents (methanol, ethanol, n-propanol, water, N, N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone), three binary solvents (ethanol-water mixtures, ethanol-methanol mixtures, and n-propanol-water mixtures) was determined by HPLC method at temperatures from 293.15 K to 323.15 K. Then, the Van't Hoff equation, Apelblat equation, λh equation, NRTL equation, CNIBS/Redlich-Kister model and modified Jouyban-Acree-van't Hoff model were used to correlate the solubility. The correlated solubility accounted for suitable compatibility with the experimental results (ARD <10%). Furthermore, we investigated the intermolecular interactions in the crystal structure through Hirshfeld surface analysis and estimated the overall charge distribution of molecules by molecular electrostatic potential surface (MEPs). Then, we analyzed the solvent effects and solvation free energy to explain the solubility behaviors. The results indicated that hydrogen bonds play a decisive role in determining the solubility of D-Tagatose.

Octadecylamine and serine-derived carbon dots-modified silica gel for reversed phase/hydrophilic interaction liquid chromatography

In order to meet the demand for the separation of complex samples, the development of mixed-mode chromatographic stationary phases has become one of the research priorities in chromatographic separation. In this work, carbon dots, Ser-OCDs, with amino, hydroxyl, carboxyl and alkyl chains were synthesized for the first time and modified on silica gel for RPLC/HILIC mixed-mode chromatography. The stationary phase, Sil-Ser-OCDs, enables the effective separation of hydrophobic and hydrophilic compounds such as alkylbenzenes, polycyclic aromatic hydrocarbons, nucleosides, bases and sulfonamides with better separation selectivity and higher column efficiency compared to classical C18 column. Polycyclic aromatic hydrocarbons, nucleosides, bases and sulfonamides can all be separated in less than 10 min, Moreover, the column efficiency (theoretical plates, N) of butylbenzene was even as high as 124,024 plates m−1. By investigating the effects of column temperature and concentration of buffer salt solution on retention and constructing the van't Hoff equation, hydrogen bonding, π-π conjugation, electrostatic repulsion, partitioning and hydrophobic interactions were found to be the main retention interactions. Sil-Ser-OCDs column was eluted for a long time at pH 3 and 8, and the relative retention remained basically unchanged, which proved that the stability of the column was excellent. This work broadens the variety of chromatographic stationary phase materials, at the same time, indicates that carbon dots have promising applications in mixed-mode chromatography.

Interaction of Curcumin with Poly Lactic-Co-Glycolic Acid and Poly Diallyldimethylammonium Chloride By Fluorescence Spectroscopy.

Poly Lactic-Co-Glycolic Acid (PLGA) and Poly Diallyldimethylammonium Chloride (PDDA) are widely being used for drug delivery and curcumin is being studied as potential drug molecule for its anti-oxidant, anti-inflammatory and anti-cancer activities. The interaction between PLGA, PDDA and curcumin was investigated by fluorescence spectroscopy. The modified Stern-Volmer equation was used to estimate the value of the binding constant Ka and the van't Hoff equation was used to estimate the corresponding thermodynamic parameters (ΔHo, ΔSo, and ΔGo). The obtained results showed that the binding constant between PLGA and Curcumin is due to the formation of hydrogen bonds and van der Waals forces. However, PDDA interacts with curcumin through hydrophobic interactions. Moreover, zeta potential measurements were obtained for these polymers and the surface charge was compared in presence and absence of the negatively chargedcurcumin molecules. It was found that the results obtained by zeta potential measurements are in agreement with those obtained by fluorescence spectroscopy. It is also found that binding of curcumin with PDDA is further encouraged in the presence of PLGA.

Study on the difference in adsorption performance of graphene oxide and carboxylated graphene oxide for Cu(II), Pb(II) respectively and mechanism analysis

Graphene oxide has been widely studied as a new type of adsorbent due to its strong affinity for heavy metal ions. However, limited by the number of oxygen-containing functional groups on its surface, there are still some defects in the field of heavy metal ion adsorption. In this paper, graphene oxide (GO) was prepared by modified Hummers method, and carboxylated graphene oxide (GO-COOH) was further synthesized by the derivatization reaction of bromoacetic acid with hydroxyl group under strong alkali conditions. The physical and chemical properties of the material were characterized by XRD, SEM, TEM, XPS and FT-IR. Taking copper and lead ion solutions as pollution models, the adsorption behaviors of the two heavy metal ions solutions on GO were investigated through batch adsorption experiments, adsorption kinetic model, adsorption isotherm model and Van't Hoff equation. The experimental results showed that the maximum adsorption capacity of GO for Cu(II) after carboxyl group treatment increased from 55.47 mg/g to 62.02 mg/g, and the maximum adsorption capacity of GO-COOH for Pb(II) increased from 85.17 mg/g to 96.21 mg/g. In this paper, the reasons for the difference in the adsorption capacity of GO for Cu(II) and Pb(II) and the significant enhancement of the adsorption performance of GO-COOH were discussed, and the possible adsorption mechanism was proposed. The research in this paper provides a new way to realize the efficient utilization of graphene oxide materials in the purification process of water environment and the development of modern materials science.

Study on the solid-liquid equilibrium of triphenylphosphine in four mono-solvents and two mixed solvents

The gravimetric method was used to determine the solubility of triphenylphosphine in four mono-solvents (acetonitrile, tetrahydrofuran, cyclohexane, ethyl acetate) and two binary mixed solvents (acetonitrile + tetrahydrofuran, ethyl acetate + tetrahydrofuran) at normal pressure and temperature range (288.15 K-328.15 K). The results show that the solubility of triphenylphosphine in the selected solvent increased with the increase of temperature within the temperature range studied. In the binary mixed solvent (ethyl acetate + tetrahydrofuran, acetonitrile + tetrahydrofuran), the solubility of triphenylphosphine increased with the increase of the mass fraction of tetrahydrofuran. In addition, the Hansen solubility parameter (HSP) was used to explain the dissolution behavior of triphenylphosphine. The solubility data were fitted by the modified Apelblat equation, van't Hoff equation, λh equation, Apelblat-Sun equation and NRTL model. The results show that the modified Apelblat equation and van't Hoff equation have a better fitting effect on the solubility data of triphenylphosphine in the mono-solvents used in the experiment, and the modified Apelblat equation has a better fitting effect on the solubility data of triphenylphosphine in the binary mixed solvent used in the experiment. The fitting results can provide some basic data for the optimization of the crystallization process of triphenylphosphine. The thermodynamic properties of the dissolution process of triphenylphosphine in the selected solvent were calculated and discussed by van't Hoff equation, and the thermodynamic properties of the solution (ΔdisH, ΔdisS and ΔdisG) were all positive values, which increased that the mixing and dissolution of triphenylphosphine in the selected solvent are endothermic and entropy-driven. This study can provide basic thermodynamic data for the crystallization and industrial separation of triphenylphosphine.

Analysis of solid-liquid equilibrium behavior of highly water-soluble beet herbicide metamitron in thirteen pure solvents using experiments and molecular simulations

Metamitron (MET), a highly water-soluble herbicide for sugar beets, has posed a significant threat to aquatic species due to its high solubility in water; therefore, understanding its solid–liquid phase equilibrium data in different solvents is essential for the future development of more environmentally friendly forms. In this study, the solubility data of MET in 12 pure solvents were determined gravimetrically and analyzed using theoretical methods (primarily Molecular electrostatic potential surface analysis, Hirshfeld surface analysis, Reduced Density Gradient analysis, radial distribution function, and solute–solvent interaction energy) to further investigate the solid–liquid equilibrium behavior. Although MET's high solubility in water contributes to environmental contamination, its value is low in comparison to that of other organic solvents. Four models, including the Apelblat equation, the λh equation, the van't Hoff equation, and the NRTL, were used to examine all solid–liquid equilibrium data, and an ARD% below 5 confirmed its good correlation. The MET solubility data is anticipated to provide solid guidance for the future development of more effective and environmentally acceptable green formulations.

Multi-temperature experiments to ease analysis of heterogeneous binder solutions by surface plasmon resonance biosensing

Surface Plasmon Resonance (SPR) biosensing is a well-established tool for the investigation of binding kinetics between a soluble species and an immobilized (bio)molecule. While robust and accurate data analysis techniques are readily available for single species, methods to exploit data collected with a solution containing multiple interactants are scarce. In a previous study, our group proposed two data analysis algorithms for (1) the precise and reliable identification of the kinetic parameters of N interactants present at different ratios in N mixtures and (2) the estimation of the composition of a given mixture, assuming that the kinetic parameters and the total concentration of all interactants are known. Here, we extend the first algorithm by reducing the number of necessary mixtures. This is achieved by conducting experiments at different temperatures. Through the Van’t Hoff and Eyring equations, identifying the kinetic and thermodynamic parameters of N binders becomes possible with M mixtures with M comprised between 2 and N and at least N/M temperatures. The second algorithm is improved by adding the total analyte concentration as a supplementary variable to be identified in an optimization routine. We validated our analysis framework experimentally with a system consisting of mixtures of low molecular weight drugs, each competing to bind to an immobilized protein. We believe that the analysis of mixtures and composition estimation could pave the way for SPR biosensing to become a bioprocess monitoring tool, on top of expanding its already substantial role in drug discovery and development.

2-aminopyrimidine-oxalic acid liquid–liquid charge-transfer interactions: Synthesis, spectroscopic characterizations, and the effect of temperature

The intermolecular charge-transfer (CT) interaction of 2-aminopyrimidine (2AP) (as an electron donor) with oxalic acid (OA) (as a typical σ-electron acceptor) has been studied at multiple temperatures in methanol solvent. The stoichiometry of the generated CT complex (2AP-OA) was determined using the Benesi-Hildebrand method (BHM). The molecular interaction of 2AP donor with OA acceptor has been discussed as a function of temperature. The crystal structure and space group of the 1:1 adduct has been determined using the single-crystal X-ray crystallographic technique. The 1H NMR spectrum of 2AP-OA indicates the formation of N+H∙∙∙O− intermolecular hydrogen bonding. The FTIR spectrum of 2AP-OA also well resolved the complex absorption bands in the region where 2AP and OA bands have been observed. The thermal stability and composition of 2AP-OA were analyzed to compare with 2AP donor and OA acceptor using thermogravimetric (TGA) and differential thermal analysis (DTA). The Van’t Hoff equation was employed to calculate various important thermodynamic parameters (i.e., entropy; ΔS, enthalpy; ΔH, and Gibbs free energy; ΔG). The reaction between 2AP and OA was spontaneous and exothermic in nature, as indicated by the negative values of ΔG and ΔH.

Solubility Measurement, Thermodynamic Correlation, and Comprehensive Analysis of 3,5-Dinitrobenzoic Acid in 13 Pure Solvents

The solubility of 3,5-dinitrobenzoic acid in 13 solvents (methanol, ethanol, n-propanol, i-propanol, n-butanol, 2-butanol, i-butanol, n-pentanol, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, and acetonitrile) was tested by gravimetry from 283.15 to 323.15 K under atmospheric pressure. The results showed that the solubility of 3,5-dinitrobenzoic acid increased with the increasing temperature in all pure solvents. Besides, the experimental solubility results of 3,5-dinitrobenzoic acid was fitted with thermodynamic equations like modified Apelblat equation, van’t Hoff equation, λh equation and the nonrandom two liquid equation. The results of average relative deviation, root-mean-square deviation, and coefficient of determination showed that the modified Apelblat equation correlates best of all models. Moreover, solvent effects and density functional theory (DFT) were introduced to demonstrate the dissolution properties of 3,5-dinitrobenzoic acid in the above solvents. At last, the dissolution process of 3,5-dinitrobenzoic acid in selected solvents was spontaneous according to the results of the mixing Gibbs free energy change (ΔmixG).

Interaction of Heparin with Proteins: Hydration Effects.

We present a thermodynamic investigation of the interaction of heparin with lysozyme in the presence of potassium glutamate (KGlu). The binding constant Kb is measured by isothermal titration calorimetry (ITC) in a temperature range from 288 to 310 K for concentrations of KGlu between 25 and 175 mM. The free energy of binding ΔGb derived from Kb is strongly decreasing with increasing concentration of KGlu, whereas the dependence of ΔGb on temperature T is found to be small. The decrease of ΔGb can be explained in terms of counterion release: Binding of lysozyme to the strong polyelectrolyte heparin liberates approximately three of the condensed counterions of heparin, thus increasing the entropy of the system. The dependence of ΔGb on T, on the other hand, is traced back to a change of hydration of the protein and the polyelectrolyte upon complex formation. This dependence is quantitatively described by the parameter Δw that depends on T and vanishes at a characteristic temperature T0. A comparison of the complex formation in the presence of KGlu with the one in the presence of NaCl demonstrates that the parameters related to hydration are changed considerably. The characteristic temperature T0 in the presence of KGlu solutions is considerably smaller than that in the presence of NaCl solutions. The change of specific heat Δcp is found to become more negative with increasing salt concentration: This finding agrees with the model-free analysis by the generalized van't Hoff equation. The entire analysis reveals a small but important change of the free energy of binding by hydration. It shows that these ion-specific Hofmeister effects can be modeled quantitatively in terms of a characteristic temperature T0 and a parameter describing the dependence of Δcp on salt concentration.

Increasing the Equilibrium Solubility of Meloxicam in Aqueous Media by Using Dimethyl Sulfoxide as a Cosolvent: Correlation, Dissolution Thermodynamics and Preferential Solvation

Meloxicam is widely prescribed as an analgesic and anti-inflammatory drug in human therapeutics. Owing the very low aqueous solubility of meloxicam, this property has been studied in dimethyl sulfoxide (DMSO)-aqueous solvent systems at several temperatures from 273.15 to 313.15 K to expand the solubility database about analgesic drugs in mixed solvents. The flask shake method followed by ultraviolet-visible (UV-vis) spectrophotometry analysis were used for meloxicam solubility determinations. A number of cosolvency models, including the Jouyban–Acree model, were challenged for solubility correlation/prediction of this drug in these mixtures. The van’t Hoff and Gibbs equations were employed to calculate the apparent standard thermodynamic quantities relative to dissolution and mixing processes. The inverse Kirkwood–Buff integral method was employed for calculating the preferential solvation parameters of meloxicam by DMSO in the mixtures. Meloxicam solubility increases with increasing temperature and maximum solubilities are observed in neat DMSO at all temperatures studied. Dissolution processes were endothermic in all cases and entropy-driven in the composition interval of 0.40 ≤ x1 ≤ 1.00. A nonlinear enthalpy–entropy relationship was observed in the plot of enthalpy vs. Gibbs energy for drug transfer processes. Meloxicam is preferentially solvated by water in water-rich mixtures but preferentially solvated by DMSO in the composition interval of 0.21 &lt; x1 &lt; 1.00.

Effects of intermolecular interactions and solvent properties on the solid-liquid phase equilibrium of isosorbide 5-mononitrate

Isosorbide 5-mononitrate (5-SIMN) is an organic nitrate pharmaceutical for the treatment of angina pectoris. In this work, first, the solubility of 5-ISMN in ten organic solvents was determined by the laser dynamic method at temperatures ranging from 278.15 K to 318.15 K. The results showed that the equilibrium solubility of 5-ISMN was temperature-dependent and increased monotonically with temperature. In addition, the effect of solvent properties on the dissolution behavior of 5-ISMN was also investigated, in which the “like dissolves like” principle played a critical role in the equilibrium solubility of 5-ISMN in different solvents. Next, four models (Apelblat equation, Van't Hoff equation, λh equation, and NRTL equation) were used to verify and correlate the experimental solubility data. The Apelblat equation fits the data well, and the maximum ARD% was less than 3%. Furthermore, molecular dynamics simulations were explored to reveal the effect of solute-solvent interactions on the dissolution behavior. Finally, the mixing thermodynamic properties of 5-ISMN were derived, and the results demonstrated that the mixing process was entropy-driven and spontaneous.

Thermodynamic Studies on the Hydrolysis of Trivalent Plutonium and Solubility of Pu(OH)3(am).

The temperature-dependent reaction properties of actinide elements are of particular interest in the safety assessment of high-level radioactive waste (HLRW) disposal systems. In this study, the hydrolysis of Pu(III) and the solubility of Pu(OH)3(am) were investigated at various temperatures (10-40 °C) in 0.1 M NaClO4. A strong reducing condition for maintaining the oxidation state of Pu(III) while slowly increasing the pH of the solution was realized by electrolysis. The formation constants of the first hydrolysis species, log *β1', and the solubility products of Pu(OH)3(am), log *Ks,0', at 10, 17, and 40 °C were experimentally determined using spectrophotometry, laser-induced breakdown detection, and radiometry. The enthalpy and entropy changes for these reactions were estimated using the van't Hoff equation. The first hydrolysis of Pu(III) is endothermic (ΔrHm° = 34.10 ± 4.48 kJ mol-1), and the dissolution of Pu(OH)3(am) is exothermic (ΔrHm° = -294.29 ± 23.05 kJ mol-1) with negative entropy changes. These thermodynamic data will contribute to improving the reliability of the safety assessment of HLRW disposal facilities and understanding the geochemical behavior of Pu under reducing or anoxic aqueous conditions at elevated temperatures.

Solubility, Hansen solubility parameter, molecular simulation and thermodynamic analysis of N-methyl-3,4,5-trinitropyrazole at various temperatures

• The solubility data of MTNP was measured by a laser monitoring method. • The experimental values were correlated and calculated by four equations. • Solubility order was analysed by using the Hansen solubility parameter. • The E inter was calculated by molecular simulation based on DFT for explaining the solubility order. • The thermodynamic parameters were calculated by the van’t Hoff and Gibbs equations. The solubility of N-methyl-3,4,5-trinitropyrazole (MTNP) in (isopropanol + ethanol) mixtures at T = 283.15 K-323.15 K was tested by a laser monitoring method. The solubility of MTNP increases with the increasing temperature in (isopropanol + ethanol) mixtures. The solubility of MTNP decreases with the increasing isopropanol mass fraction ranging from 0.10 to 0.90. Besides, supersolubility (the metastable zone width) of MTNP was determined by a laser monitoring method. The experimental results showed that the solubility of MTNP in (isopropanol + ethanol) solvent mixtures increases with increasing temperature and the metastable zone width decreases with increasing temperature. Additionally, the values were correlated by the modified Apelblat equation, van’t Hoff equation, CNIBS/R-K model and Ma model. In addition, Hansen solubility parameters were used to explain the solubility order. Solubility order of MTNP in (isopropanol + ethanol) solvent mixtures was interpreted by comparing the interaction energy ( E inter ) between MTNP and binary solvent. The apparent thermodynamic properties of Gibbs energy, enthalpy and entropy were calculated by the van’t Hoff and Gibbs equations. The enthalpy-entropy relationship for MTNP was discussed. Finally, solid-liquid surface tension and surface entropy factor were obtained by the solubility data.

Enhancement of clozapine solubility in three aqueous choline chloride-based deep eutectic solvents: Experimental and COSMO-RS prediction

• Solubility behaviors of clozapine in aqueous DESs solutions were revealed by COSMO-RS. • Solubility of clozapine in aqueous DESs solutions was measured. • Solubility of clozapine was enhanced by increasing weight fraction of DES and temperature. • Dissolution thermodynamics of clozapine was calculated via van't Hoff equation. The clozapine (CLZ) solubility (molar fraction) in three aqueous choline chloride (ChCl) based deep eutectic solvents (DESs) with urea (U), glycerol (G) and ethylene glycol (EG) was determined at T = (293.15 to 313.15) K under an atmospheric pressure. As neoteric green co-solvents, DESs can apparently enhance the CLZ solubility more than 550-fold than that in pure water at T = 293.15 K, especially in ChCl/G. At the same DESs proportion (weight fraction) and same temperature, the CLZ solubility in aqueous DESs solutions is ranked as ChCl/G > ChCl/EG > ChCl/U. Furthermore, the experimental solubility of CLZ in aqueous DES solutions has been correlated by NRTL, three-Suffix Margules, UNIQUAC and Wilson models, suggesting NRTL model to be the best correlation. In addition, the SLE CLZ solubility data was also predicted by reference solubility method using COSMO-RS model, and the predicted results are consistent with the experiment data. The basic mechanism of the solubility behavior of CLZ and solvent molecules was analyzed by studying σ profiles of DESs as well as the molecular interaction energies, implying that the CLZ dissolution is a complex process affected by the synergy of molecular interactions. Based on van’t Hoff equation, the solution thermodynamic properties (Δ G dis o , Δ H dis o and Δ S dis o ) have been estimated, indicating the dissolution process of CLZ in aqueous DES solutions is endothermic and entropy-driven. The improved solubility of CLZ in aqueous DES solutions provides reference for its application in novel crystallization development for the CLZ manufacture.