Solvents in Chromatography and Electrophoresis

Solvents are able to extract and/or dissolve chemicals while carrying them without modification. They are central to separation science. This chapter describes the physicochemical properties of the solvents used in liquid chromatography and a variety of less common chemicals that can be used as solvents in different separation processes. In chromatography, solvents are rarely used pure. Mixtures with water and/or other solvents are used. The physicochemical properties of the most commonly used water–methanol and water–acetonitrile mixtures are described introducing the concept of elution strength. Ternary-phase diagrams give information of mixtures of three solvents. Their properties and use are briefly recalled. Ionizable compounds are very important in separation science. Their ionization state depends on their pKa and on acidity of the solvating phase that is rarely pure water. The effect of organic modifiers on mobile-phase acidity is tackled and illustrated with an example. A large table compiles the data for more than 100 chemicals possibly used as solvents.