Contribution To The Theory of Nonlinear Chromatography

A new approach to the theory of nonlinear chromatography is presented. It applies to isotherms which are not too nonlinear, in which case it is shown that the center of gravity of the peak moves at a relative velocity equal to 1/√2 of the velocity of peak maximum. Equations relating peak retention time, asymmetry, and peak shape in terms of the nonlinearity constant β, plate number N, and base capacity ratio k_o are derived. The derived equations are checked by comparing them with the exact answers obtained from the numerical solution of the differential equations of the plate model applied to the nonlinear isotherm. The deviations are found to be small. It is also demonstrated that for slightly nonlinear isotherms, the resulting peak shapes are asymmetric Poisson distributions with asymmetries which can be calculated from the above-mentioned parameters.