Approximation of a weak gradient in the theory of gradient ion chromatography

Abstract

The study presents the basic relationships between the kinetic and equilibrium characteristics of gra-dient ion chromatography. The relationship between these characteristics with the parameters of components on the dynamic map of the chromatographic system was found. Equations were obtained for the trajectory displaying the course of a chromatographic experiment on the map. The principles and the simplest algo-rithms for the procedure of optimization of the gradient ion chromatography were formulated. It was shown that, despite the extreme complexity, the theoretical description of the gradient modes of ion chromatography was possible with acceptable accuracy. The developed approach to the description of complex modes of ion chromatography allowed new finely tuned conditions to be revealed (for example, sign-alternating gradient modes of the «lens» type) that increase the productivity of chromatography. The advantage of the "lens" mode proposed in the study is the equality of the eluent composition at the beginning and at the end of the process, which eliminates the regeneration of the column for re-analysis. The difficulties of such modes in-clude the need for a very accurate calculation and implementation of the mixing function, which sets the de-pendence of the strength of the eluent over time. Simulation modelling is used for the solution of such prob-lems. A computer program IONCHROM, which allows predicting the behaviour of the system under the ob-tained conditions, was produced as a result of the simulation. An example of a real system was developed. For this system, the «lens» mode, which is a specially organized sign-alternating gradient mode, was predict-ed.