Polydispersity in size-exclusion chromatography: A stochastic approach

• Polydispersity was integrated into the molecular (stochastic) model of chromatography.
• Even a small dispersion in the molecular weight can contribute substantially to band broadening
• Pore size distribution and polydispersity have identical effect on the band profile.

We investigate the impact of polydispersity of the sample molecules on the separation process and on the efficiency of size-exclusion chromatography. Polydispersity was integrated into the molecular (stochastic) model of chromatography; the characteristic function, the band profile and the most important moments of the elution profiles were calculated for several kind of pore structures. We investigated the parameters affected by polydispersity on the separation for a number of pore shapes. Our results demonstrate that even a small distribution in the molecular size (i.e. polydispersity) can contribute substantially to the total width of the chromatographic peak. The pure effect of polydispersity can only be investigated via mathematical modeling, because its contribution to an experimental chromatogram cannot be separated from other band-broadening effects.