Influence of adsorption on the measurement of diffusion coefficients by Taylor dispersion

Abstract

The effect of adsorption on the measurement of diffusion coefficients by the Taylor dispersion technique is investigated by modifying the governing equation to account for reversible, nonequilibrium adsorption. The resulting two-dimensional equations are solved by an explicit finite-difference technique. Experimental data for the acridine-carbon dioxide system indicated that acridine adsorbs on the walls on the tubing and these data were investigated with this model. The influence of various parameters including the number of sites and the rates of adsorption/desorption was investigated by conducting a parametric sensitivity analysis on the model. It was found that adsorption of the solute on the wall of the tubing could produce an error as high as 35% on the measured diffusion coefficient compared to the actual diffusion coefficient. Examination of the influence of each of the parameters will enable future investigators to reduce the effect of adsorption in the measurement of diffusion coefficients by Taylor dispersion.

Nanoparticle Taylor Dispersion Near Charged Surfaces with an Open Boundary

“…1(a), and thus the open boundary acts as an ideal particle sink. This sink progressively modifies the structure of the particle distribution in the observation zone [4,41], as shown next.…”

“…Several experimental works noted that such interactions or absorption [40] bias diffusion coefficient evaluations using the Taylor dispersion method [31]. In typically millimetric capillary tubes, the induced error was noted as a few tens of percent [41]. Such errors may become more significant in smaller systems, for instance, in applications for peptide diffusion and the determination of aggregate sizes [38,42], among others [43].…”