Calculation of adsorption isotherms from chromatographic peak shapes

Abstract

Abstract Jonsson, J.A. and Lovkvist, P., 1989. Calculation of adsorption isotherms from chromatographic peak shapes. Chemometrics and Intelligent Laboratory Systems , 5: 303–310. A numeric method is presented for the calculation of a nonlinear sorption isotherm from the shape of a chromatographic peak in the presence of significant dispersion effects (nonideal, nonlinear chromatography). The algorithm involves an initial guess for a reasonable isotherm function, and a reasonable value for D , the diffusion coefficient. This permits the calculation (by numerical solution of the pertinent nonlinear partial differential equation) of a new peak. Using the properties of the original peak and of the calculated peak, new estimates for the isotherm function and for D can be calculated. These calculations are repeated until the discrepancy between consecutive iterations is judged to be insignificant. The procedure was tested with computer-generated peaks and shown to converge to the expected isotherm curve after few iterations even if the initial guesses of isotherm shape and D are relatively coarse. A preliminary application to an experimentally measured chromatographic peak is also presented.