Measurement and correlation of solubility data for atorvastatin calcium in pure and binary solvent systems from 293.15 K to 328.15 K

Abstract The solubility of Atorvastatin calcium (ATV) in 11 kinds of mono-solvents and binary solvent mixture (acetone + water) of different ratio was measured by typical static method combined with ultraviolet (UV) spectrophotometry within the temperature range from 293.15 K to 328.15 K under standard atmospheric pressure. The solubility data was correlated by the modified Apelblat equation, van't Hoff equation, CNIBS/R-K equation, Sun model and NRTL model. The mole fraction solubility of ATV increased with rising temperature and the mole fraction composition of acetone in binary solvent mixture of acetone + water. In the case studied, the experimental data and calculated data of the five models have good correlation. Furthermore, the overall root mean square deviation (ORMSD) of the modified Apelblat equation is lowest in mono-solvents, and the NRTL model has the lowest value in a binary solvent system, which suggests that the two models have the most suitable fitting efficiency for the experimental solubility data of ATV.. Additionally, the van't Hoff equation was used to calculate and evaluate the thermodynamic properties of the ATV dissolution process, including enthalpy (∆Hsol0), entropy (∆Ssol0) and Gibbs free energy (∆Gsol0). The solubility data and corresponding thermodynamic models provided in this work have certain reference value for the crystallization, purification and pharmaceutical formulation design of ATV.