EXPERIMENTAL INVESTIGATION AND MODELING OF CLOSED-LOOP RECYCLING IN PREPARATIVE CHROMATOGRAPHY

The separation of a binary mixture was investigated using a modified HPLC method. Since the separation factor was low the injected sample was recycled several times through the column to simulate an increase of the column length. For the example studied the separation could be improved considerably performing four cycles. To simulate the process a dispersion model was used to describe the concentration profiles in the column. Local equilibrium for the liquid and adsorbed phase concentrations was assumed. An apparent dispersion coefficient was applied to take into account all kinetic effects causing band broadening. In order to represent mixing effects in the pump a CSTR model was included additionally. Methods to determine the free model parameters were discussed. A good agreement between the experimental data and the model predictions was found for the system investigated.