The Moment Equations of Chromatography for Monolithic Stationary Phases

Abstract

The solution in the Laplace domain of the system of equations of the general kinetic model of chromatography provides equations relating the first absolute moment and the second central moment of elution bands to the characteristics of the retention equilibrium and the mass transfer kinetics, respectively. For continuous porous rod (i.e., monolithic) columns, these moment equations have the same form as those for conventional columns packed with spherical particles of a suitable packing material. However, some of the coefficients in the equation of the second central moment are different for conventional and monolithic columns. The results of the calculations made with the moment equations derived here for monolithic columns agree well with some typical characteristics of the experimental behavior observed for monolithic columns, showing the validity of these new moment equations. They should be useful for a detailed analysis of the retention equilibrium and of the mass transfer kinetics in monolithic-type columns. These moment equations are also applicable to the study of the adsorption characteristics of cylindrical adsorbents, such as activated carbon fibers.