Cosolvency

Cosolvency refers to the ability of a solvent system, composed of two or more components, to dissolve a solute that is poorly soluble in any single component alone. This phenomenon occurs when the components of the solvent system interact synergistically to enhance the solubility of the solute. The effectiveness of cosolvency is often attributed to changes in the polarity, surface tension, or hydrogen bonding capacity of the solvent mixture compared to its individual constituents.

In many applications, cosolvency is crucial for formulating solutions of poorly soluble substances. This is particularly relevant in the pharmaceutical industry, where many active pharmaceutical ingredients exhibit low aqueous solubility, hindering their bioavailability. By using cosolvent mixtures, such as ethanol-water or propylene glycol-water, formulators can increase the concentration of the drug in a liquid dosage form. Other fields that utilize cosolvency include the chemical industry for reactions and separations, and in the development of inks and coatings. The selection of appropriate cosolvents and their ratios is critical and depends on the specific solute and desired application.