Cosolventit

Cosolventit are substances added to a primary solvent to influence the solvation environment and improve the solubility of solutes. In chemistry and pharmaceutical science, cosolvents are used to modify solvent properties such as polarity, dielectric constant, hydrogen-bonding ability, and viscosity, enabling the dissolution of compounds that are poorly soluble in a single solvent.

Cosolvent effects arise from changes in the solvent mixture's physical properties and interactions with solute molecules. The solubility of a given solute can be enhanced or, in some cases, reduced depending on the composition of the solvent system. Ternary phase behavior, miscibility, and potential instabilities are important considerations when using cosolvents.

Common cosolvents include small polar organic solvents such as methanol, ethanol, isopropanol, acetone, acetonitrile, as well as aprotic solvents like dimethyl sulfoxide (DMSO) and dimethylformamide (DMF). Other examples are glycerol, ethylene glycol, and polyethylene glycols. The choice depends on the solubility of the solute, regulatory constraints, toxicity, volatility, and the desired processing conditions.

Applications of cosolvents span several fields. In pharmaceutical development, cosolvents are used to solubilize poorly water-soluble drugs for formulation and testing. In biochemistry, they can aid in protein solubility and stabilization. They also play roles in analytical chemistry, extraction, chromatography, and polymer processing, where solvent systems are tuned for better dissolution or processing behavior.

Selection and handling of cosolvents require evaluating solubility data across solvent compositions, compatibility with active ingredients, and safety considerations. Regulatory limits, environmental impact, boiling points, and toxicity inform practical choices and waste management. See also co-solvent, solvent system, and ternary phase diagram.