APPLICATION OF ORTHOGONAL COLLOCATION ON FINITE-ELEMENTS IN THE SIMULATION OF NONLINEAR CHROMATOGRAPHY

Orthogonal collocation on finite elements permits the calculation of the chromatographic elution band profiles for one or two components. The individual band profiles obtained for binary mixtures are more accurate than those derived using one of several possible finite difference methods. In most cases, the difference between these profiles is small when the column efficiency is high or the mass transfers between phases in the column are fast. When the concentration of the second eluted component is low compared to the concentration of the first one, however, the front of the second component band is much steeper than predicted by the finite difference method, in agreement with the result of the finite element calculation procedure. The advantage of the better accuracy is compensated by a considerably higher computation time.