Preparative Chromatography - Radial Flow Chromatography > Page 63
Figure 33. Packing Radial Columns
In practice, the gradient is made to 'lift' the solutes from the packing by the progressive increase in either the dispersive solvent component of the mobile phase, the polar component, salt concentration or the pH depending on the type of phase system selected. This means it is generally restricted to the separation of substances that have relatively large separation ratios and differ significantly in the strength of their interaction with the stationary phase. Due to the cross-sectional area decreasing as the solute progresses through the bed, the linear velocity of the mobile phase also changes and so the optimum velocity can only be a compromise for the total bed length.