Hard modeling of ion chromatography separations on hydroxide-selective stationary phase

In the present paper the development and testing of the computer software for the simulation of the on-column ion chromatography separation processes are presented. The computer algorithm based exclusively on the selectivity coefficients of the tested analytes has been upgraded to cope with the 2:1 and 1:1 ratios of the analyte-to-eluent ion charge. The analytical solution of the cubic equation, which is needed for calculation of chromatograms for doubly charged analytes in the presence of singly charged eluent, is presented. The developed modeling approach was tested on the data sets produced by the system composed of hydroxide-selective stationary phase in combination with on-line electrolytically generated OH−-based eluents. Retention behavior of the selected anions on the AS15 (DIONEX, USA) stationary phase was investigated. The study of the dependence of the peak widths on the number of theoretical column segments considered in the calculated chromatograms enabled us to choose the optimal number of column segments. The average error in the retention time of the calculated chromatograms for the data set used in the study, i.e. seven different ions at eight different eluent concentrations was found to be 1.4%. A good match with the experimental chromatograms allows us to use the information of the intermediate states of calculations to get a detailed insight into the time-dependent on-column analyte distribution.