Extension of Linear to Nonlinear Chromatography Models

Second, when they become nonlinear, isotherms also become competitive.They should be written as qi — f C, Ca.). There is competition between the different components of the mixture for access to the stationary phase. As a result, and unlike the case of linear chromatography, the elution profiles of the different components are not independent, but they are affected by the presence of the other components, particularly the profiles of those peaks that are closely eluted. 

For all these reasons, the mathematical aspects of the theory become much more complex. The mathematics of nonlinear chromatography are so complex that even for a single solute, there is no analytical, closed-form solution available, except with two simplified models, the ideal model and the Thomas model [120]. The ideal model is based upon the assumption of an infinite column efficiency. Its solutions are discussed in detail in Chapters 7 to 9. The Thomas model is based upon the assumptions that there is a slow Langmuir adsorption-desorption kinetics and that there are no other nvass transfer resistances, nor any axial dispersion. The system of equations of this model has been solved by Goldstein [121], and this general solution has been simplified for pulse injection by Wade et al. [122]. In aU other cases, the problem must be solved numerically. The Thomas model is discussed with other kinetic models in Chapter 14 and 16. 

Guiochon, in M. Lederer (Ed.), Chromatographic Reviews, Elsevier, Amsterdam, 1966, p. 1. 

Guiochon, C. Guillemin, Quantitative Gas Chromatography, Elsevier, Amsterdam, 1988. 

Miyabe, A. Cavazzini, F. Gritti, M. Kele, G. Guiochon, Anal. Chem. 75 (2003) 6975. 

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