Thermodynamic study of salicylic acid dissolution in the mixed solvents of water, propylene glycol and choline chloride at different temperatures

Abstract

Solubility data are used for preparation of pharmaceutical formulations, nebulization and purification, development of pharmaceutical analyses. Aim: The solubility of salicylic acid in the mixture of choline chloride/propylene glycol and water in the temperature range of 293.2 to 313.2 K has been investigated, and the thermodynamic parameters for the dissolution process of salicylic acid as well as the correlation between the measured data and the models Different has been investigated for solubility.Method:In the shake flask method, an excess amount of drug is added to the mixture of solvents with predetermined weight percentages. In this way, each component of the system has already been poured into the lined flasks and after adding the desired drug, it is placed on the shaker inside the incubator at different temperatures, and they are shaken until reaching the equilibrium time and forming a saturated solution. After reaching equilibrium, the solutions are centrifuged/filtered and the clear supernatant solution is diluted with a suitable solvent and the absorbance of the diluted samples is measured by a spectrophotometer. Next, taking into account the dilution of drug solubility and based on the drawn calibration curve, the solubility can be determined in terms of moles per liter.Results:According to the data, the solubility increases with the increase in the mass fraction of the choline chloride/propylene glycol co-solvent and the temperature, so that the maximum solubility is related to the 1.00 mass fraction of the corresponding co-solvent at a temperature of 313.2 K. The obtained data were correlated with different models and the constants of each model were calculated.Conclusion: Solubility data show an upward trend with increasing temperature and cosolvent. The low error percentage of the data calculated from the models show the high ability of the models to predict the solubility.