ABSTRACT
Phosphorus occurs in natural waters, wastewater, sediments, and sludge. The main sources of phosphorus that are released into the environment include fertilizers, many detergents and cleaning preparations, and boiler waters to which phosphates are added for treatment. From an analytical standpoint, phosphorus is classified into three main categories: Orthophosphate; condensed phosphate including meta-, pyro-, and polyphosphates; and organically bound phosphorus. Orthophosphate and condensed phosphate are a measure of inorganic phosphorus. The latter is also termed as "acid-hydrolyzable phosphate". The principle of the colorimetric test is based on the reaction of orthophosphate with ammonium molybdate under acidic conditions to form a heteropoly acid, molybdophosphoric acid, which, in the presence of vanadium, forms yellow vanadomolybdophosphoric acid. The intensity of the color is proportional to the concentration of phosphate. Orthophosphate in an untreated or treated sample may be determined by ion chromatography.
