The Impact of Rare Adsorption Site Clustering on Peak Broadening in Chromatography

Peak broadening is one of the most important phenomena in chromatography, leading to a decrease in the separation efficiency. It is well-known that the presence of rare sites on the adsorption surface, which have different kinetic characteristics compared to the majority sites, may result in peak broadening and tailing. Here, we extended a Monte Carlo model of chromatography, based on stochastic theory, and included an intermediate layer between the stationary and mobile phases to delve deeper into the study of this phenomenon. We discover that not only the fraction of rare sites and their individual characteristics are important, but also their distribution on the adsorption surface. Our results demonstrate that the spatial distribution of adsorption sites impacts peak broadening; specifically, the clustering of slow, rare adsorption sites broadens the peak, and this effect remains evident even considering longitudinal and eddy diffusion in the simulation of advective-diffusive transport.