Moment analysis of peak broadening in affinity capillary electrophoresis and electrokinetic chromatography.

A moment analysis method is effective for the kinetic study of intermolecular interaction and solute permeation at the interface of spherical molecular aggregates. Association and dissociation rate constants of intermolecular interactions or the rate constants of interfacial solute permeation can be determined on the basis of the moment theory from the first absolute and second central moments of elution peaks measured by affinity capillary electrophoresis (ACE) or electrokinetic chromatography (EKC). In this study, it was discussed how the experimental conditions concerning the concentration of ligand molecule or molecular aggregate should be optimized in ACE or EKC experiments in order to determine the rate constants as accurately as possible. At first, peak broadening due to axial diffusion, reaction kinetics of intermolecular interaction, and mass transfer kinetics of interfacial solute permeation was quantitatively evaluated under hypothetical ACE or EKC conditions, which were chosen on the basis of our previous studies. Second, it was confirmed that some rate constants were determined in the previous studies from ACE and EKC data measured under appropriate experimental conditions. Then, a procedure was considered for determining more accurate analytical results of the objective rate constants from ACE or EKC peaks experimentally measured.