There have been a few technical issues that have limited adoption of SFC technology in the past. First of all, is the need to keep a high gas pressure in the operating conditions.  High-pressure vessels are expensive and bulky, and special materials are often needed to avoid dissolving gaskets and O-rings in the supercritical fluid.  A second drawback is difficulty in maintaining pressure constant (by back-pressure regulation).  Whereas liquids are nearly incompressible, so their densities are constant regardless of pressure, supercritical fluids are highly compressible and their physical properties change with pressure – such as the pressure drop across a packed-bed column.  Currently, automated backpressure regulators can maintain a constant pressure in the column even if flow rate varies, mitigating this problem.  A third drawback is difficulty in gas/liquid separation during collection of product.  Upon depressurization, the CO rapidly turns into gas and aerosolizes any dissolved analyte in the process.  Cyclone separators have lessened difficulties in gas/liquid separations.