Sodium sulfadiazine (SD-Na) is a drug extensively used for the treatment of certain infections caused by several kinds of microorganisms. Although SD-Na is widely used nowadays in therapeutics, the physicochemical information about their aqueous solutions is not complete at present. In this context, by using the van’t Hoff and Gibbs equations the thermodynamic functions Gibbs energy, enthalpy, and entropy of solution for SD-Na in ethanol + water cosolvent mixtures, are evaluated from solubility data determined at temperatures from 278.15 to 308.15 K. The drug solubility is greatest in neat water and lowest in neat ethanol at all the temperatures studied. This behavior shows the negative cosolvent effect for this electrolyte drug in this solvent system. By means of enthalpy-entropy compensation analysis, non-linear vs. plot with positive slope from neat ethanol up to 0.60 in mass fraction of water and negative from this composition to neat water is obtained; accordingly to this result, it follows that the dissolution process of this drug in ethanol-rich is entropy-driven, whereas, in water-rich mixtures the process is enthalpy-driven. Nevertheless, the molecular and ionic events involved in the dissolution of this drug in this cosolvent system are unclear.
Although the cosolvent system 1,4-dioxane+ water is poisonous, it is widely used in the pharmaceutical sciences as a versatile model for studying drug solubility and some other relevant physicochemical properties in the design of homogeneous dosage forms. For this reason, the excess molar volumes and partial molar volumes of components are investigated from density measurements of the entire range of mass fractions for the 1,4-dioxane + water system at 293.15 K; 298.15 K; 303.15 K; 308.15 K and 313.15 K. The results of excess molar volumes are fitted by Redlich-Kister equation using third degree polynomials and compared with those of literature for other systems. The system exhibits large negative excess volumes (up to – 0.71 cm3 mol–1) probably due to increased interactions like hydrogen bonding between unlike molecules or very large differences in the molar volumes of pure components. The effect of temperature on the different volumetric properties studied is also analyzed. Besides, the volume thermal expansion coefficients are also calculated founding values varying from 2.50 x 10–4 K–1 for pure water up to 1.06 x 10–3 K–1 for pure 1,4-dioxane at 298.15 K.
This work reports the experimental volumetric properties and also the saturated solubility of indomethacin and ethylhexyl triazine in ethyl acetate + ethanol mixtures at 293.15 to 313.15 K and evaluates the validity of the Jouyban-Acree (J & A) model to correlate the solubility of these compounds in ethyl acetate + ethanol solvent mixtures. The solubility correlation is studied as a function of temperature and cosolvent composition. The J & A model requires only the experimental solubility values in the pure solvents at all the temperatures under study. The calculated values by using both compounds deviate as mean in 30% from experimental solubility values.
Ketoprofen (KTP) is a widely used anti-inflammatory drug. In this paper the validity of a trained version of the Jouyban-Acree (J & A) model is evaluated to predict the solubility of KTP in ethanol + water cosolvent mixtures. The usefulness of the solubility log-linear equation proposed by Yalkowsky and Roseman (Y & R) is also evaluated for the same drug in this cosolvent system. The solubility estimation is studied as a function of temperature and cosolvent composition. The J & A and Y & R models require only the experimental solubility values in the pure solvents at all the temperatures evaluated. The calculated values by using both models deviate notoriously from experimental values in several cases.
Tinidazole is an anti-parasitic drug widely used nowadays in therapeutics. Nevertheless, it has not been well characterized from a physicochemical point of view. In this context, by means of optical experimental methods and dielectric spectroscopy applied to diluted solutions of Tinidazole in Acetone, molar polarizations of the solute, 0P2, and the solvent, 0P1, and the average dipolar moment of tinidazole associated to acetone, were estimated, resulting in 9.18 D. Since this value is higher than the theoretical m of the two main conformers of isolated tinidazole, that is, 3.22 and 4.29 D, respectively, the formation of interactions between the solute and the solvent is assumed. An effect of intermolecular association by van der Waals and hydrogen bond interactions conducting to a modification of the partial molar volume of the solute is thus expected. From the experimental and analysis by using the Halverstadt-Kumler’s method, it can be seen that the partial molar volume had a 24% reduction as compared with the theoretical value, which would confirm the presence of such interactions.
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