Solvatochromic probes in supercritical fluids

Supercritical fluids (SCFs) have in recent years become favored solvents for chemical reactions and separations. In order to be used as solvents, their solvation properties should be known, and solvatochromic probes are effectively used for this purpose. They have been applied foremost for supercritical carbon dioxide (SCCD), which is by far the most widely employed SCFs, but also for supercritical water, fluorocarbons and other substances. The probes have also found use in mixtures involving SCF and a more polar additive that have better solvation properties for polar solutes and in solvents expanded by dissolving in them SCCD. Clustering of the molecules of the SCF around the probe molecule is a common feature of the systems studied and this may reflect on the employment of the probes as stand-ins for other solutes.