Determination of Solubility and Thermodynamic Parameters of Triamterene in Pure and Ethanol-Modified Subcritical Water at Various Temperatures

In this study, the solubility of Triamterene (TRM), a diuretic drug, in pure and ethanol-modified subcritical water (SCW) was investigated by a static method. Experiments were performed at high temperatures (363.15–433.15 K) with co-solvent (0–10% w/w ethanol) at a pressure of 20 bar. Increasing the temperature and weight percentage of ethanol significantly increased the mole fraction solubility of TRM. The mole fraction solubility of TRM in pure water (0% wt ethanol), 5%wt ethanol, and 10%wt ethanol was obtained in the range of 0.73 × 10^–4–1.56 × 10^–4, 0.73 × 10^–4–1.82 × 10^–4, and 0.78 × 10^–4–2.16 × 10^–4, respectively. For the correlation of experimental solubility data, linear and modified Apelblat models were selected. The values of ARD and RMSD were calculated as indicators of the accuracy and validity of the models. The modified Apelblat model showed the best performance in correlating the experimental solubility data. Finally, the dissolution thermodynamic functions (\({\Delta }_{dis}{G}^{^\circ }\), \({\Delta }_{dis}{H}^{^\circ }\) and \({\Delta }_{dis}{S}^{^\circ }\)) were calculated for the solubility of TRM in pure and ethanol-modified SCW.