Effect of density on kinetic performance in supercritical fluid chromatography with methanol modified carbon dioxide

The pump and back pressure regulator (BPR) pressures are not necessarily good indicators of pressures or densities in the column. At high flow rates the extra-column pressure drop (ΔP) can be much larger than the column ΔP and can be unevenly distributed in front of and behind the column. In one extreme the ΔP after the column was 3 times higher (105 bar) than the actual column ΔP (32 bar).