‘Eddy’ Diffusion in Chromatography (Reply)

Abstract

VARIANCES add¹, for certain independent processes which, by virtue of an elementary random event, contribute directly to the variance. Lateral diffusion is not such a process. The variance is caused by non-equilibrium established by the difference in downstream velocity from point to point. Lateral diffusion acts to reduce this variance as can be seen by the inverse relationship between variance or plate height and diffusion coefficient. The random change in velocity which occurs along a given stream path, as found in packed columns but not in capillary columns, also reduces the variance. Both factors act independently to exchange molecules between fast- and slow-moving regions.