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