Measurement and prediction of solubilities of active pharmaceutical ingredients.

Solubilities of 2-acetoxy benzoic acid (aspirin), N-acetyl-p-aminophenol (paracetamol) and 2-(p-isobutylphenyl)propionic acid (ibuprofen) have been measured in various solvents and compared with published and predicted data. For the prediction besides the two group contribution models UNIFAC and modified UNIFAC (Dortmund) the quantum chemical approach COSMO-RS (Ol) was used. Additionally melting temperatures and heats of fusion for 2-acetoxy benzoic acid, N-acetyl-p-aminophenol and 2-(p-isobutylphenyl)propionic acid required for the calculations have been determined by differential scanning calorimetry.