Consolidation of the packing material in chromatographic columns under dynamic axial compression .4. Mechanical properties of some packing materials

Dynamic axial compression columns were packed with three C-18 silica materials used as stationary phases in preparative chromatography, one made of irregular and two of spherical particles, Measurements of column length vs. time and axial compression pressure, obtained for several columns, have been previously reported. These results are discussed here in terms of packing density, internal porosity, and external porosity, as allowed by the use of independent measurements of the density of the silica skeleton and the pore volume. The compressibilities and Young moduli of the columns are calculated and compared to results obtained in soils mechanics for various soil types. The results indicate that the preparative columns packed with silica particles exhibit a behavior intermediate between that of uniform fine and medium-sized sands. The angular silica material exhibits higher compressibility than both spherical silica materials on first compression. Upon recompression, one of the spherical silicas studied exhibits high compressibility and thus elasticity, suggesting a looser packing structure than the other spherical material; this is supported by calculation of the external porosities of the two materials, Results with respect to the kinetic theory of consolidation in soils mechanics are also presented.