CHROMATOGRAPHY, Vol. 32 (2011), No. 3, pp. -153

Supercritical Fluid Chromatography (SFC) offers high speed analysis due to high diffusivity of solutes in the low-viscosity supercritical mobile phase. Generally, the separation mode in SFC is regarded as normal phase with a combination of non-polar CO₂ mobile phase and polar stationary phase. Therefore, separation of water-soluble polar compounds is considered to be difficult to separate by using SFC. However, the elution and peak shapes of polar compounds can be improved by adding a small amount of acid, base, volatile salt and ion pair reagent to the modifier solvent such as alcohol.
In chiral preparative SFC, samples are often over-loaded and it is difficult to determine when to start and end fractionation from Ultra Violet (UV) chromatographic data. A Circular dichroism (CD) detector can differentiates enantiomers and generate positive/negative chromatographic peaks. In addition, CD detector can simultaneously generate CD, UV and g-factor signals. The g-factor is a signal defined as CD/ UV whose level is independent of the peak concentration but dependent only on enantiopurity. Therefore, enantiopurity of g-factor triggered fractions is very high.