Interpretative optimization of the isocratic ion chromatographic separation of anions
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Interpretive retention modeling was utilized to optimize the isocratic ion chromatographic (IC) separation of the nine anions (formate, fluoride, chloride, nitrite, bromide, nitrate, phosphate, sulfate and oxalate). The carbonate-bicarbonate eluent was used and separation was done on a Dionex AS14 ion-exchange column. The influence of combined effects of two mobile phase factors, the total eluent concentration (2-6 mM) and the carbonate/bicaronate ratio from 1:9 to 9:1 (which correspond to pH range 9.35-11.27), on the IC separation was studied. The multiple species analyte/eluent model that takes into account ion-exchange equilibria of the eluent and sample anions was used. In order to estimate the parameters in the model, a non-linear fitting of the retention data, obtained at two-factor three-level experimental design, was applied. To find the optimal conditions in the experimental design, the normalized resolution product as a chromatographic objective function was employed. This cr...iterion includes both the individual peak resolution and the total analysis time. A good agreement between experimental and simulated chromatograms was obtained.