Methodologies for the rapid determination of the diffusion interaction parameter using Taylor dispersion analysis

Abstract

Taylor Dispersion Analysis (TDA) is a fast and simple method for determining diffusion coefficients of molecules in solution. This is achieved by measuring the dispersion of a small quantity of solute after its injection into a mobile phase. Due to repulsive or attractive molecular interactions, such as self-association in the latter case, the diffusion coefficient of a solute may vary with concentration. Typically, the analysis of such concentration dependent behavior requires a concentration titration experiment. In this paper, we present a method for extracting concentration-dependent diffusion coefficients and, hence, the diffusion interaction parameter, k_D, in a single measurement. In TDA, this is achieved by injecting a slug of the solute into the mobile phase and measuring its dispersion as a function of concentration along the resulting front. Three ways of applying the method are presented and applied to aqueous caffeine (negative interaction parameter) and Bovine Serum Albumin prepared in two different buffers (positive interaction parameters). The results were found to be in good agreement with literature values and Dynamic Light Scattering (DLS) measurements.