Band dispersion in chromatography -: a new view of A-term dispersion

Flow dispersion in chromatography arises from several independent kinetic processes. We show that in liquid chromatography by far the most important contribution to dispersion under practical operating conditions comes from the flowing part of the mobile phase. Contrary to widely held belief, slow mass transfer within the porous particles normally used in HPLC is unimportant. This is demonstrated by data from both gas and liquid chromatography. The consequences of this change of emphasis are important. Better packing of HPLC columns can certainly produce much more efficient columns. Previous interpretations of the rates of mass transfer of partially excluded polymers in size-exclusion chromatography should be reassessed. Further work should be carried out with monodisperse particles in both HPLC and CEC. New structures made by microfabrication methods hold the promise of much higher efficiencies. Turbulent flow chromatography may yet provide good efficiency by using pellicular particles. (C) 1999 Elsevier Science B.V. All rights reserved.