A selective amplification-titration procedure for the determination of microgram amounts of phosphate

Abstract

Phosphate is converted into phosphomolybdic acid, which is separated from excess of molybdate by extraction. The phosphomolybdate is back-extracted into aqueous solution, and the twelve molybdate ions accompanying each phosphate ion are reduced on a silver reductor column and titrated with 10^–3M cerium(IV) by use of a 50-ml burette. Other heteropoly acid-forming elements, e.g., arsenic, antimony, germanium and silicon do not interfere, and there is no interference from a wide range of other ions. The method is both precise and rapid, and has been applied to the submicro determination of phosphorus in a standard organic compound.