Prediction of solubility of etodolac in binary solvents using extended hildebrand solubility approach

Abstract

The solubility of etodolac in binary solvent system i.e. methanol water system was analyzed in term of solute solvent interaction using extended Hildebrand solubility approach (EHSA).The solubility equation employs the term interaction energy (W) to replace the geometric mean (δ1δ2), where δ1 and δ2 are the cohesive energy densities for the solvent and solute, respectively. The new equation provides an accurate prediction of solubility once the interaction energy 'W' is obtained. In this case, the energy term is regressed against a polynomial in δ1 of the binary mixture. TisconSonicator A-72 & UV-Visibile spectrophotometer shimadzu UV-1700 were used in prediction & evaluation of solubility of Etodolac. Ideal Solubility of Etodolac was calculated by heat of fusion and absolute melting point obtained from DSC data reported in literature. Molar volume and solubility parameter of Etodolac were calculated from Fedor fragmental constant using floatation & experimentally solubility method. Results showed the solubility of Etodolac in the binary solvent, methanol-water shows a bell-shaped profile with a solubility maximum well below the ideal solubility of the drug. This is an attribute to solvation of the drug with the methanol-water mixture, and indicates that the solute-solvent interaction energy is larger than the geometric mean (δ1δ2) of regular solution. It was observed that in binary Methanol water system maximum solubility occurs at 17.