PRELIMINARY TESTS TO SELECT OPERATING-CONDITIONS FOR THE ACCURATE DETERMINATION OF STABILITY-CONSTANTS BY CATION-EXCHANGE CHROMATOGRAPHY - THE CD2-CL- AND CD2+-NO3- SYSTEMS()

Ion chromatography (IC) has been demonstrated to be a powerful tool fo r equilibrium constant determination, related to various cation-ligand systems. Nevertheless, no systematic research has been carried out to develop preliminary checks in order to verify whether the variation i n ligand concentration in the eluent at constant ionic strength affect s the exchange mechanism for the system of interest in the selected ch romatographic column. In this paper, tests are proposed which allow on e to determine beforehand the experimental conditions to be used in ca tion-exchange chromatography, whereby parallel mechanisms of elution ( mainly in the reversed-phase mode) are avoided. In this way IC becomes an independent rather than an auxiliary means to obtain accurate beta (i) values. Cd(II)-Cl- and Cd(II)-NO3- systems were considered and are discussed.