Differential elution of sodium or potassium dihydrogen- and hydrogenphosphate ions from a Sephadex G-15 column with sodium or potassium chloride solution

When a mixed solution of sodium or potassium dihydrogenphosphate and disodium or dipotassium hydrogenphosphate was eluted from a Sephadex G-15 column with either a sodium or potassium chloride solution, the elution profiles of ions showed that the hydrogenphosphate ion was eluted more rapidly than the dihydrogenphosphate ion. When the sample solutions containing potassium dihydrogenphosphate and/or dipotassium hydrogenphosphate, all of which were supplemented with phosphorus-32-labelled potassium dihydrogenphosphate, were eluted with sodium chloride solution, the elution profiles of radioactivity showed that the dihydrogenphosphate ion changed to hydrogenphosphate ion and vice versa, depending on the pH values of the sample solution and the availability of the cation of the eluent during elution for the phosphate ion to pair with.