Separation of Various Forms of Nitrogen in Fertilizers

A method is proposed in which both a cation and an anion resin are used to separate the various forms of nitrogen in fertilizers. By this method troublesome phosphate ion is removed from the urea-containing solution, thereby making it possible to determine urea directly without the double-precipitation procedure required in AOAC method 2.055. The proposed cation-anion exchange column procedure makes it possible to determine the water-soluble amnionic, nitric, and amidic forms of nitrogen rapidly, accurately, and directly.