Chapter 10 Supercritical fluid extraction

Publisher Summary This chapter discusses supercritical fluid extraction. When a substance is maintained at a temperature above its critical point, the vapor and liquid have the same density and it becomes impossible to liquefy the substance by increasing pressure. Thus, a single phase is maintained regardless of the applied pressure. This single phase is called a “supercritical fluid” and is characterized by a critical temperature ( T c ) and a critical pressure ( P c ). A supercritical fluid has the beneficial properties of both liquids and gases. It has a density approaching that of the liquid and a high solubilizing power. The diffusivity is intermediate between a liquid and a gas and the viscosity is similar to a gas. A supercritical fluid can be considered a solvent with continuously adjustable solvent power, and this can be utilized in the separation processes on the industrial and analytic scales. Supercritical fluid extraction has become a favored means of analytic sample preparation, particularly for the removal of analytes of interest from solid matrices prior to chromatography.