A supercritical fluid has physical properties (high density and solubility, low viscosity, and high diffusivity) making its use interesting in chromatography. Among the different avaible fluids , CO2 emerges as the fluid of choice for SPC for the following reasons :

• Critical point easily reachable (Tc=31°C ; Pc=74 bars).
• Fast sepapration time (typically less than5 min): the low viscosity of supercritical CO2 allows high elution flow rates.
• High plates' number and more resolution power thanks to to the transport properties of supercritical CO2.
• Easy recovery of purified highly concentrated samples.
• Supercritical CO2 exhibits a good solvent power. It is cheap, non-flammable and non-toxic..
• CO2 is transparent in UV and IR.

Witch applications in chromatography with supercritical CO2 ?

• Enantio-separation on chiral stationary phases.
• Purification on achiral phases of molecules such as steroides, fatty acids, tocopherols, benzodiazepines, alkaloids, etc...

Depending on compound polarity, addition of polar co-solvaent (typically alcohol up to25 %) to CO2 is needed.