Solubility of sodium diclofenac in different solvents

The solubility of sodium diclofenac in several solvents such as acetone, ethyl acetate and dimethyl sulfoxide was studied, in the temperature range from 293.15 up to 313.15 K. The solubility of sodium diclofenac is of the same order of magnitude for acetone and ethyl acetate. The solubility of the drug in dimethyl sulfoxide is two orders of magnitude higher and it is of the same magnitude as in N,N-dimethylformamide, a solvent of the same class as dimethyl sulfoxide, concerning the solubility parameter. The experimental SLE data was modeled using the NRTL and a modified UNIQUAC model and both models were proven to give a good representation of the experimental data. The use of activity coefficients at infinite dilution for the description of the solid–liquid equilibrium was also considered. COSMO-RS predictions of the relative solubility of sodium diclofenac in the three solvents are shown to be in qualitative agreement with the experimental data.