What is a Supercritical Fluid (SF)?
A supercritical fluid (SF) is substance that is above its Critical Temperature (Tc) and Critical Pressure (Pc) such that it exists as a single phase. A substance in the supercritical region exhibits properties of both a gas and a liquid. According to the National Institute for Standards and Technology, the Critical Temperature and Critical Pressure for carbondioxide (CO2) are 304.1 K (31.1°C) and Pc is 73.8 bar respectively. The phase diagram for carbon dioxide is shown in figure 1. The use of carbon dioxide as eluent offers several advantages. Carbon dioxide has a low viscosity, is relatively chemically inert, and can be easily removed post-separation as gas at room temperature.
