High-Pressure Gas Chromatography and Chromatography with Supercritical Fluids. II. Permeability and Efficiency of Packed Columns with High-Pressure Gases as Mobile Fluids under Conditions of Incipient Turbulence

Abstract

The behavior of packed gas-liquid chromatographic columns using-carbon dioxide as a carrier gas has been studied at various pressures. Measurements of pressure drop as a function of flow rate indicated that at velocities normally used in gas chromatography the flow through the column becomes progressively more turbulent with increasing pressures above a few atmospheres. At conditions near the critical pressure the Reynolds number may be about three orders higher than in normal gas chromatography with hydrogen or helium as a carrier gas. Measurements of column efficiency at various gas pressures and velocities disclosed that the most important contributions to plate height (at pressures higher than usual in gas chromatography) are associated with large-scale unevenness of flow and intraparticle gaseous diffusion, respectively. From a comparison of high-pressure gas chromatography with conventional gas chromatography and liquid chromatography, it appears that as regards potential speed and efficiency the two first-mentioned techniques are comparable and much better than the last one.