Unique elution behavior of bromide and nitrate in anion-exchange chromatography using aqueous potassium chloride eluent containing cadmium or zinc ion

In anion-exchange chromatography using a high-concentration eluent and high-capacity ion-exchange resin, the effect of the countercation contained in the eluent was investigated. Cadmium(II) and zinc(II) ions were examined as additives in an aqueous potassium chloride eluent. The addition of these cations resulted in a reversed elution order of bromide and nitrate, as compared with conventional anion-exchange chromatography. The separation factor for these two anions increased as the cadmium concentration in the eluent was increased. Zinc(II) ion was also effective, but a relatively high concentration was necessary.