In ion chromatography, samples of very dissimilar concentration ratios of ammonium-to-sodium are difficult to quantify since these two cations have similar selectivities for stationary phases containing commonly used sulfonic acid or carboxylic acid cation-exchange functional groups. A new column with carboxylic acid and phosphonate functional groups as well as a crown ether group has been developed to address this limitation. Selectivity of the common inorganic cations is different from conventional columns in that the separation between sodium and ammonium has been greatly increased, and potassium ion elutes after magnesium and calcium. Applications involving very dissimilar concentration ratios of cations can now be done isocratically, with a single column. Other applications of this new column will also be discussed.