Understanding Column Bed Heterogeneity In the Quest for Improved Separation Performance

It is now well understood that chromatographic columns are heterogeneously packed.  Optical on-column visualization has shown that the migration of sample bands near the wall of a column differ from the migration rates within the central core of the column. Band profiles are thus parabolic, generally presenting as faster and more efficient migration in the centre of the column, and slower and less efficient near the wall. Largely, the heterogeneity is related to the frictional forces encountered in the packing process – particle to particle and particle to wall, but there is also a geometrical factor that relates to the particle size distribution and the inability to obtain a close packed configuration between rigid particles and a rigid wall. While improvements in particle size distributions continue to improve aspects associated with packing order, it is difficult to overcome the friction related aspects that lead to less than ideal packing geometry. The work described herein presents a new approach to overcoming the limitations of flow heterogeneity within chromatography columns, providing improvements in theoretical plates of more than 50% greater than conventional columns