Nonequilibrium Kinetics and Chromatography

Abstract

An effort is made here to deal with the complex kinetic processes which determine the structure of component zones in chromatography. The problem is approached by assuming that the various steps are proceding near equilibrium. In order to facilitate the analysis an approximation is made in which each derivative of a concentration is replaced by the derivative of the equilibrium concentration. The latter derivatives are evaluated in terms of the concentration profile. This yields a set of linear algebraic equations from which an equilibrium departure term, ε, can be found for each species. The diffusion of the zone is then obtained as a function of the various ε's. The simplicity introduced by this method allows one to obtain the zone diffusion term for complex kinetics in contrast to the rigorous theories where only the simplest kinetic schemes have been treated. The results for a simple kinetic example are the same, however, as obtained in the limit of large times by the rigorous methods. The validity of the assumptions made is established independently of this comparison. Various applications of the method are discussed which extend beyond the range of chromatographic analysis.