Gas-Expanded Liquids Extraction

Abstract

Gas Expanded Liquids (GXL) are mixtures of liquid solvents (organic, water) and gases or supercritical fluids with diverse physicochemical properties halfway between pure liquids and supercritical fluids. The possibility of changing their properties by introducing small changes in pressure, temperature, and/or solvent/gas ratio, makes these solvents a very interesting and appropriate option for developing green extraction protocols for food analysis. In general, GXLs have similar densities as the solvent used in their composition, while having improved mass transfer through reduced viscosity, increased solute diffusivity, and decreased interfacial tension. Some other advantages are related to the wide range of polarities that can be obtained, depending on the liquid selected. Moreover, the substitution of a liquid fraction for a gas reduces the final use of organic solvent, thus improving the green character of GXLs. In the present chapter, the physicochemical properties of GXL are addressed along together with the description of applications in the food science and technology area.