PREDICTION OF INORGANIC AND ORGANIC ION BEHAVIOR WITH POLYVALENT ELUENTS IN ION CHROMATOGRAPHY

A model is presented that relates the capacity factor, k', to experime ntal stationary and mobile phase elution variables (resin capacity, dr y resin mass, dead volume, concentration and pH) and to the protonatio n constants of the specimens involved. Application of the model to elu tion with different concentrations of phthalic acid using a low-capaci ty quaternary ammonium column permits the determination of the selecti vity coefficients of each ion-exchange equilibrium and the establishme nt of the theoretical k' (pH) curves at a constant eluent concentratio n, which are seen to coincide with the experimental curves. The model is able to predict solute behaviour and optimize separation by establi shing the corresponding acidity conditions. Likewise, this model is a possible tool for studying ion-exchange and non-polar interactions of ions with ion-exchange columns.