Modeling of Gradient Elution in Multicomponent Nonlinear Chromatography

-Gradient elution in nonlinear chromatography is a very powerful tool for the separation of components having a wide range of retentivity. It is not only used for chemical analysis, but also used in preparativeand large-scale chromatography for the separation of many macromolecules, such as proteins. In this work, a general rate model has been presented for the study of gradient elution in nonlinear chromatography. The model considers axial dispersion, external film mass transfer, intraparticle diffusion and kinetic effects. The modulator-eluite relationship used in the model accounts for both electrostatic and hydrophobic interactions. Examples of simulations have been given to demonstrate the efficiency and robustness of a computer code based on a numerical procedure for the general rate model, which uses the finite-element, the orthogonal-collocation and Gear's stiff methods. The examples also show the advantage of gradient elution over isocratic elution in multicomponent elutions, and the comparisons among linear, nonlinear and stepwise linear gradients.