Computational method for modeling of gradient separation in ion-exchange chromatography

A model for the simulation of the gradient separation in ion-exchange chromatography is presented. It is based on discontinuous plate model and simulates the distribution of analytes in the ion-exchange column during the separation process. It enables calculations of chromatograms for the analytes with integer and non-integer effective charges under complex gradient profiles. Equilibrium concentrations of all analytes are calculated using the same mathematical equations and expressions regardless of the effective charge on the analyte. The main parameters required for the simulations have to be determined under isocratic elution. The suitability of the model was tested with different types of gradients. A comparison of retention times and chromatograms shows that reliable predictions for all tested gradients are achieved. The observed average of the absolute values of the relative errors of the retention times obtained for any analyte in the present study from the calculated chromatograms is below 4%, while the average error considering all analytes in the study is below 2%.