Thermodynamic study of naproxen dissolution in the mixed solvents of propylene glycol and isopropanol at different temperatures

Abstract

Introduction:Solubility is one of the most important physicochemical properties of medicinal substances, which is very important in the process of drug discovery and development. Solubility data provide important and useful information for the preparation of pharmaceutical formulations, development of pharmaceutical analyses, recrystallization in the purification process, and extraction.Aim:In this research, the solubility and density of the naproxen in the solvent mixture of isopropanol + propylene glycol in the temperature range of 293.2 to 313.2 K will be studied. Also, the correlation between the obtained data and different solubility models will be investigated. Method:In this study, the solubility was measured using the shake-flask method. For this purpose, different mixtures of isopropanol and propylene glycol were prepared with mass intervals of 10% and excess amounts of drug were dispensed into it, and after centrifugation of the solution and appropriate dilution, the absorption of the solutions was measured at 262 nm using a UV spectrophotometer and the concentrations were calculated using a plotted calibration curve. This process was repeated for 5 temperatures and all data were used to find an equation to predict solubility. Results:The obtained results indicate that the solubility of naproxen increases with the increase of the mass fraction of isopropanol, until it reaches its maximum value at w1 = 0.7. Then, by adding more amounts of isopropanol, the solubility decreases. In addition, the solubility of naproxen increases with temperature increase in each mass fractions. The obtained data were fitted to different models and the constants of each model were calculated.Conclusion:The results showed that the solubility of naproxen depends on the temperature and composition of the studied solvent, and the used models were able to predict the solubility data well with an acceptable error.