Supercritical/subcritical HPLC separation

An area of study related to this topic is the use of subcritical, but superheated water as a mobile phase for chromatographic separations [78], These separations use water heated to 100-220°C and pressures up to 50 bar, avoiding problems due to hydrolysis and oxidation, which is common when supercritical water is used. Although this is a new area of investigation, several reports on the hyphenation of HPLC using... 

The first chiral separation using pSFC was published by Caude and co-workers in 1985 [3]. pSFC resembles HPLC. Selectivity in a chromatographic system stems from different interactions of the components of a mixture with the mobile phase and the stationary phase. Characteristics and choice of the stationary phase are described in the method development section. In pSFC, the composition of the mobile phase, especially for chiral separations, is almost always more important than its density for controlling retention and selectivity. Chiral separations are often carried out at T < T-using liquid-modified carbon dioxide. However, a high linear velocity and a low pressure drop typically associated with supercritical fluids are retained with near-critical liquids. Adjusting pressure and temperature can control the density of the subcritical/supercritical mobile phase. Binary or ternary mobile phases are commonly used. Modifiers, such as alcohols, and additives, such as adds and bases, extend the polarity range available to the practitioner. 

---