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

Abstract

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.