Alternative method to study the radial dispersion in liquid chromatography columns. Part I: Theory

We report on an alternative experimental method to determine the transversal or radial dispersion coefficient (D_rad) in packed bed columns for liquid chromatography. The method uses a recently developed type of column end-fitting with an impermeable segmentation ring that splits the incoming flow in a central and peripheral part. Using this device and continuously sending a tracer-laden flow through the central inlet and a tracer-less flow through the peripheral inlet, a steady-state radial dispersion pattern is established which can be used to determine the degree of radial dispersion. The present part of the study lays the theoretical foundation for the method and shows the parameter sensitivity of the different possible data analysis variants. In addition, computational fluid dynamics simulations have been used to validate the established procedure (agreement between true and determined D_rad-value better than 0.4%) as well as to study the effect of the most important error sources: the presence of the annular flow segmentation ring and the almost inevitable occurrence of mismatches between the central and the peripheral in- and outlet flows. In the latter case, a combined read-out method can be proposed that nearly perfectly compensates for the flow mismatch error (remaining error on the D_rad-value smaller than 3%).