Solubility and Extractability in the Pharmaceutical Sciences: A Demonstration to Address These Essential Concepts

Understanding the solubility and extractability of organic compounds plays a crucial role in the pharmaceutical and biomedical fields. It is essential to learn these concepts early in the course curriculum. The aim of this demonstration is to help students understand the basic principles of solubility and extractability in a practical, interactive, and interesting way. This is accomplished with the help of a series of simple experiments in which common reagents and molecules will be used. The demonstration covers three main topics. The first part is designed to explain the intrinsic solubility in water. This solubility will depend on a number of properties, including their ratio of polar/nonpolar groups and their ability to form hydrogen bonds. The second part investigates potential ionization in water using results obtained from conductimetry experiments. The third part is related to the concept of extractability by presenting the results obtained for pH-dependent extractions of representative compounds from an aqueous medium with an organic medium. A quantification of the extracted compound at each pH is performed after the evaporation of the organic solvent. Extractability curves are then drawn, using the weights obtained after evaporation and discussed.