Calorimetric studies of diclofenac sodium in aqueous solution of cyclodextrin and water-ethanol mixtures

The technique of solution calorimetry has been employed to study the interaction between diclofenac sodium and β‐cyclodextrin by determining the enthalpies of solution of the drug in water and in aqueous β‐cyclodextrin solution. Thermodynamic parameters characterizing the binding process such as enthalpy ΔH0, equilibrium constant k, free energy ΔG0 and entropy ΔS0 have been calculated to be −12.00 kJ mol−1, 1670 dm3 mol−1, −19.03 kJ mol−1 and 22.98 J k−1 mol−1, respectively. Enthalpies of solution of diclofenac sodium have also been determined in water‐ethanol mixtures.