Comparison of broadening patterns in regular and radially compressed large-diameter columns

Abstract

Summary The differential broadening pattern of an inert solute injected centrally into a regular (A) and a radially compressed (B) column has been studied. The two columns exhibit identical properties when operated in the infinite diameter mode. A marked difference, to the advantage of column B, develops as the solute becomes appreciably exposed to the wall region. At its fullest extent, the wall effect accounts for a nearly 2.5-fold increase in plate height for column A compared with a 1.5-fold increase for column B. This behavious is rationalized in terms of a semi-theoretical model that takes the radial diffusivity, the radial dependence of the lateral plate height and the peak local velocity into account. It is further shown that the solute radial concentration profile departs significantly from a truncated gaussian shape. The actual profile can be expressed as a Bessel function series.