Shock layer theory and concentration dependence of the axial dispersion and the mass-transfer rate coefficients

Independent determinations of the coefficients of axial dispersion and of the mass-transfer kinetics have been found to be concentration dependent in protein chromatography. The consequences of this observation are studied on a theoretical basis. Numerical calculations of breakthrough curves were carried out, assuming a linear dependence of these coefficients on the solute concentration. The results obtained illustrate the influence of the concentration dependence on chromatographic band profiles. The classical shock layer theory, which assumes constant coefficients, was extended to the case in which they depend linearly on the concentration. The analytical solution of the shock layer profile agrees with all the results of the numerical calculations. Consideration of the shock layer thickness provides an easy access to the kinetic information contained in the breakthrough profiles.