Evidence of a Wall Friction Effect in the Consolidation of Beds of Packing Materials in Chromatographic Columns

Experimental observations demonstrate the intensity of the friction between the bed of a packed chromatographic column and its wall. The wall supports the bed but, in the process, causes the strong radial heterogeneity of the bed which has been previously reported and is now well documented. Friction against the wall is not entirely harmful, however. Without wall friction, the bed would contract with increasing head pressure. the bed in a typical analytical column would be a few mm longer in the absence of mobile phase flow than under standard operation conditions. Experiments demonstrate the existence of bed friction against the column wall in an axial compression column. They show that the friction coefficient depends on the nature of the solvent, the axial compression stress applied to the bed, and the bed length.