The study of the details of mass transfer in liquid chromatography is of central interest. We apply the microscopic (or molecular dynamic) model of chromatography to study the reversed phase separation of small and large molecules. The microscopic theory of chromatography describes the evolution of a chromatographic peak as the random migration of the molecules along the column combined with adsorption–desorption processes that occur at random, too. The molecular dynamic model is rather straightforward to comprehend and it can furnish direct answers when one tries to understand the development of chromatographic peaks. We show that the microscopic model can be rather simply used to estimate the fundamental characteristics of the separation process. We can estimate the rate a molecule is adsorbed on the surface of the stationary phase while it migrates along the column. When combining the general rate model with the molecular dynamic model, one can consider and compare the kinetics of the transfer of solute molecules between the flowing and stagnant zones of mobile phase, the pore diffusion, etc. We analyze the peak shapes recorded under linear conditions, and can characterize the heterogeneity of the surface of the stationary phase. With a peak shape analysis that is based on the molecular dynamic model of chromatography, we can identify the presence of heterogeneous mass transfer or adsorption kinetics. We can, furthermore calculate the amount of retention due to the individual adsorption sites. The general rate model of chromatography, which is a macroscopic model, offers the most detailed description of the separation process. We compare the results provided by both microscopic and macroscopic analysis of the peak shapes and statistical moments. In this paper we discuss the influence of wide pore-size distributions. We present results obtained on nonporous, fully porous, and fused-core particles. Furthermore, mass transfer in supercritical fluid chromatography and reversed-phase liquid chromatography are compared.
Presenting author:
Attila Felinger
University of Pécs
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Authors:
Attila Felinger - University of Pécs
