Estimation of adsorption parameters in a detailed affinity chromatography model based on shallow bed experiments

A method for estimation of unknown adsorption parameters in a detailed chromatography model including the Langmuir adsorption expression is proposed. The model describes the concentration of the solute in the mobile phase and considers external/internal mass transfer resistance and adsorption dynamics. The external volume and its mixing effect are also considered. The unknown model parameters estimated are the bed void, the axial dispersion coefficient, the liquid film mass transfer coefficient, the effective diffusion coefficient, the apparent bead porosity, the adsorption/desorption rate coefficients and the Langmuir isotherm. All the parameters in the model were subsequently determined in four classes of experiments, the external mixing behaviour, the mobile phase behaviour, the stationary phase behaviour and the adsorption behaviour. The estimates are based on the sum of the least squares of the residuals between the experimental breakthrough curves and the model response. The methodology is exemplified by frontal experiments with bovine serum albumin in a shallow packed bed. The results show that it is possible to estimate the adsorption parameters using the proposed methodology, and to replace the Langmuir adsorption dynamic expression with the corresponding isotherm when high inlet concentrations are used. It was also investigated at what inlet concentration this model simplification resulted in satisfactory results. It was possible to estimate adsorption parameters using several experimental breakthrough curves simultaneously, i.e. multiple data responses, to obtain single parameters that are valid within the interval of inlet concentrations used.