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1. Approaching to a Precise Determination of the Solid-State Transformation Temperature of an Enantiotropic System: Gestodene | |||
WANG Liyu,ZHU Liang,LI Xianchao,SHA Zuoliang | |||
Chemical Engineering 16 June 2015 | |||
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Abstract:The objective of this work is to accurately measure the solid-state transformation temperature (Ttr) of two crystalline forms (form Ⅰ and form Ⅱ) of gestodene by three distinct methods. The polymorphic transformation among two polymorphs (form Ⅰ to form Ⅱ) was observed by differential scanning calorimetry (DSC) and variable temperature X-ray powder diffraction (VT-XRPD) measurements. Therefore, Ttr was evaluated as the onset transformation temperature by DSC at seven different heating rates ranging from 2 to 20 K min-1. In the solubility data method, Ttr is calculated as the temperature at which solubilities of the two forms are equal to each other. The solubility data of both polymorphs were measured gravimetrically in ethanol in the temperature range from 268.15 to 333.15 K under the atmospheric pressure of 0.10 MPa. The experimental solubility data were used to calculate the solid-solid transformation temperature based on the modified Apelblat and van't Hoff equation. In the last method, Ttr is determined directly by experimental studies of the temperature ranges of the stability of each polymorph. The mixture of both forms was agitated in a saturated solution at the programming temperature. X-ray powder diffractometer (XRPD) was used to determine the solid-state form of the residual crystals in suspension at equilibrium. The solid-solid transformation temperature of gestodene, determined with the DSC method, solubility data method and isothermal method, were found to be 313.44 K, 296.90 K (Apelblat equation), 298.11 K (van't Hoff equation) and 293.65 ± 0.5 K, respectively. As it can be observed, the mechanisms of the polymorphic transformation determined by different methods are different. Therefore, the calculated transformation temperature exhibits small difference by distinct methods. | |||
TO cite this article:WANG Liyu,ZHU Liang,LI Xianchao, et al. Approaching to a Precise Determination of the Solid-State Transformation Temperature of an Enantiotropic System: Gestodene[OL].[16 June 2015] http://en.paper.edu.cn/en_releasepaper/content/4647722 |
2. Correlation of solubility and Prediction of the Mixing Properties of Ginsenoside Compound K in various solvents | |||
LI Runyan,YAN Hao,WANG Zhao,GONG Junbo | |||
Chemical Engineering 25 July 2012 | |||
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Abstract:The solubilities of ginsenoside compound K in pure solvents and binary mixture solvents were determined at several temperatures from 278.15 K to 318.15 K by a static analytical method. The experimental solubility data in pure solvents were correlated by the van't Hoff plot, modified Apelblat equation, λh (Buchowski) equation, Wilson model and NRTL model, with the Wilson model giving the best correlation results. Based on the Wilson model and experimental data, the mixing Gibbs free energies, enthalpies and entropies of solutions and activity coefficients in pure solvents were predicted, and other thermodynamic properties (infinite-dilution activity coefficients and excess enthalpies) were calculated as well. In addition, the solubility was maximal at a certain water mole fraction in acetone + water mixture and acetonitrile + water mixture, whereas in methanol + water system, the solubility decreases with the water concentration increases monotonically. The solubilities in mixture solvents were correlated by the components of solvent using Wilson model. The partial molar Gibbs free energies with negative values were obtained, which indicates the changing of the solubility. | |||
TO cite this article:LI Runyan,YAN Hao,WANG Zhao, et al. Correlation of solubility and Prediction of the Mixing Properties of Ginsenoside Compound K in various solvents[OL].[25 July 2012] http://en.paper.edu.cn/en_releasepaper/content/4485546 |
3. Correlation of Solubility and Prediction of the Mixing Properties of Capsaicin in Different Pure Solvents | |||
YAN Hao,WANG Zhao,WANG Jingkang | |||
Chemical Engineering 25 July 2012 | |||
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Abstract:Using a static analytical model, experimental solubility data were obtained for capsaicin in n-hexane, cyclohexane, carbon disulfide, butyl ether, and isopropyl ether at temperatures ranging from 278.15 K to 323.15 K. The melting temperature and fusion enthalpy of capsaicin were measured using differential scanning calorimetry. The measured solubility data were well correlated by the van't Hoff, modified Apelblat, λh (Buchowski), Wilson, and NRTL models, with the Wilson model showing the best agreement. The activity coefficients of capsaicin and the mixing Gibbs free energies, enthalpies, and entropies of the resulting solutions were predicted based on the Wilson model parameters at measured solubility points. In addition, the infinite-dilution activity coefficients and excess enthalpies of capsaicin were estimated. Finally, the effects of solute-solvent intermolecular repulsive interactions on the solubility behavior and the values of mixing Gibbs free energy were discussed. | |||
TO cite this article:YAN Hao,WANG Zhao,WANG Jingkang. Correlation of Solubility and Prediction of the Mixing Properties of Capsaicin in Different Pure Solvents[OL].[25 July 2012] http://en.paper.edu.cn/en_releasepaper/content/4485567 |
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