Study on the accuracy of the elution by characteristic point method for the determination of single component isotherms

The accuracy of the method of elution by characteristic point (ECP) used to determine single component isotherms was studied numerically. Overloaded elution peaks were calculated using the equilibrium-dispersive model of nonlinear chromatography while varying the four parameters, i.e., the number of theoretical plates, the dimensionless Langmuir equilibrium constant, the retention and the loading factor, involved in the fundamental equations of the problem. Single component isotherms were estimated by analyzing the diffuse profile of the elution peaks by the ECP method. Similar results were obtained with the transport-dispersive model. The comparison of these calculated isotherms with the initial Langmuir isotherms provided detailed information on the influence of the mass transfer resistances on the accuracy of the isotherms afforded by the ECP method. The systematic error made on the isotherms depends on the experimental conditions, described by the four parameters. It is expected that this error could be eliminated by correcting the influence of nonequilibrium in the column on the basis of results of the nondimensional calculations. The concentration range of the objective isotherm which can be determined by the ECP method can also be predicted by numerical calculations. The usefulness of the correction strategy and the prediction of the concentration range were experimentally demonstrated. (C) 2000 Elsevier Science B.V. All rights reserved.