Hongkun Zhao

Thermodynamic modelling of solubility and preferential solvation for ribavirin (II) in co-solvent mixtures of (methanol, n-propanol, acetonitrile or 1,4-dioxane) + water

Abstract The equilibrium solubility of ribavirin in solvent mixtures of {methanol (1)+water (2)}, {n-propanol (1)+water (2)}, {acetonitrile (1)+water (2)} and {1,4-dioxane (1)+water (2)} was determined experimentally by using isothermal dissolution equilibrium method within the temperature range from (278.15 to 318.15) K under atmospheric pressure (101.1kPa). At the same temperature and mass fraction of methanol (n-propanol, acetonitrile or 1,4-dioxane), the mole fraction solubility of ribavirin is greater in (methanol+water) than in the other three solvent mixtures. The preferential solvation parameters were derived from their thermodynamic solution properties by means of the inverse Kirkwood–Buff integrals. The preferential solvation parameters for methanol, n-propanol, acetonitrile or 1,4-dioxane (δx 1,3) were negative in the four solvent mixtures with a very wide compositions, which indicated that ribavirin was preferentially solvated by water. Temperature had little effect on the preferential solvation magnitudes. The higher solvation by water could be explained in terms of the higher acidic behaviour of water interacting with the Lewis basic groups of the ribavirin. Besides, the solubility of the drugs was mathematically represented by using the Jouyban-Acree model, van’t Hoff-Jouyban-Acree model and Apelblat-Jouyban-Acree model obtaining average relative deviations lower than 1.57% for correlative studies. It is noteworthy that the solubility data presented in this work contribute to expansion of the physicochemical information about the solubility of drugs in binary solvent mixtures and also allows the thermodynamic analysis of the respective dissolution and specific solvation process.

Solubility and Preferential Solvation of 3-Nitrobenzonitrile in Binary Solvent Mixtures of Ethyl Acetate Plus (Methanol, Ethanol, n-Propanol, and Isopropyl Alcohol)

The solubilities of 3-nitrobenzonitrile in solvent mixtures of ethyl acetate (1) + methanol (ethanol, n-propanol or isopropyl alcohol) (2) determined over the temperature range from 278.15 to 318.15 K under atmospheric pressure (101.1 kPa) with the isothermal dissolution equilibrium method were reported. They increased with a rise of temperature and mass fraction of ethyl acetate, and the largest solubility value was observed in neat ethyl acetate for all the binary mixtures investigated. The temperature and solvent composition dependence of 3-nitrobenzonitrile solubility was analyzed through the Jouyban–Acree, van’t Hoff–Jouyban–Acree, and Apelblat–Jouyban–Acree models acquiring average relative deviations lower than 1.57% and root-mean-square deviation lower than 11.52 × 10–4 for correlative investigations. In addition, the preferential solvation parameters (δx1,3) of 3-nitrobenzonitrile by ethyl acetate were determined from experimental solubility values by using the inverse Kirkwood–Buff integrals. It...

Phase Diagram for the System Ammonium Oxalate + Hydrogen Peroxide + Water at 283.15 K and 293.15 K

The solubility of the ternary system (NH4)2C2O4 + H2O2 + H2O was determined experimentally at 283.15 K and 293.15 K, and the phase diagrams for the system were constructed. In addition, the density of the saturated aqueous solution was measured. The experimental results showed that, at 283.15 K and 293.15 K, two solid phases were formed in the ternary (NH4)2C2O4 + H2O2 + H2O system which correspond to (NH4)2C2O4·H2O and (NH4)2C2O4·H2O2. The compound (NH4)2C2O4·H2O2 was further confirmed by Schreinemakers wet residue method. The hydrate (NH4)2C2O4·H2O has a bigger crystallization field than either (NH4)2C2O4·H2O2 or the mixture of (NH4)2C2O4·H2O and (NH4)2C2O4·H2O2. The solubilities of (NH4)2C2O4·H2O increased sharply with an increase in the concentration of hydrogen peroxide and increased slightly with increasing temperature.

Solubility and Phase Diagram for the Ternary Sodium Oxalate + Hydrogen Peroxide + Water System at (283.15 and 293.15) K

In this investigation, the mutual solubilities for the ternary Na2C2O4 + H2O2 + H2O system were determined at (283.15 and 293.15) K. The phase diagrams of the system were constructed based on the measured solubility. The compound Na2C2O4·H2O2 was confirmed by Schreinemakers wet residue method. In addition, the density of the system was obtained. At (283.15 and 293.15) K, two solid phases were formed in the ternary Na2C2O4 + H2O2 + H2O system, which corresponded to Na2C2O4 and Na2C2O4·H2O2. The phase diagrams of the ternary system were similar at different temperatures; the solubilities of Na2C2O4 and Na2C2O4·H2O2 in water increased slightly with increasing temperature. The crystalline region of the compound Na2C2O4·H2O2 decreased as the temperature increased, the temperature having little effect on the yield of Na2C2O4·H2O2.