Supercritical Fluids as Mobile Phases in Chromatography

Abstract

Compressed fluids at temperatures in the critical range can be used as mobile phases in chromatography, especially for the separation of substances of low migration rate and/or low thermal stability. By variation of the pressure at supercritical temperatures the density of the mobile phase can be varied continuously from gas‐like to liquid‐like values, and the solvent power of the mobile phase and consequently the migration rate of the substances under test in the column can be increased by orders of magnitude (so‐called “Fluid Chromatography”). An experimental equipment for operating pressures up to 2000 atm is described. Results for a series of test substances (aliphatic and cyclic hydrocarbons) are presented. They illustrate the dependence of migration and resolution from the stationary phase and from the pressure and temperature of the mobile phase.