If a pure substance reaches a certain temperature and pressure point, the phenomenon that the liquid and gas interface disappears will occur. This point is called the critical point. Near the critical point, there is a phenomenon in which the physical properties of all fluids such as density, viscosity, solubility, heat capacity, and dielectric constant change abruptly. A fluid with a temperature and pressure above the critical point is called a supercritical fluid. Supercritical fluids have lower viscosity and better diffusivity than liquids. Supercritical fluid chromatographs primarily use carbon dioxide (CO2) as the mobile phase.

The separation time shortens the
viscosity of the supercritical fluid and has good diffusibility, so that the separation of the chiral column can achieve a good separation effect under the condition of high flow rate.

Supercritical fluid liquid Viscosity [Pa·s] 10-4 10-3 Diffusion coefficient [m2/s] 10 -7~10-8

Conducive to the separation of acidic compounds
Since the mobile phase is CO2, good separation results can be achieved without the use of additives when separating acidic compounds.

Rapid sample recovery
The CO2 in the mobile phase is directly vaporized when the atmospheric pressure is restored after the separation is completed, which greatly shortens the post-treatment time and reduces the heat load during the rotary steaming.

The amount of organic solvent is reduced.
Since the main component of the mobile phase is CO2, the amount of organic solvent can be greatly reduced, and CO2 can also be recycled.