Explain the Estimation of Inorganic Phosphorus?

Most methods estimating inorganic phosphorus use the reaction between the phosphate and an acid molybdate. The hexavalent molybdenum of the phosphomolybdic acid formed absorbs light at 340nm and can be reduced to give molybdenum blue whereas the reducing agent has negligible effect on the uncomplexed molybdic acid.

A variety of reducing agents have been used in the past and recent years by different methods and some of them are 1,2,4 amino napthol sulphonic acid (ANSA) in a mixture of sodium bisulphate and sodium sulphite (Fiske and Subbarow Method) or β methyl amino sulphate (Gomorri Method), etc. These methods can also be used to assess phosphorus status in the body by measuring phosphorus excretion or fecal phosphorus. The phosphorus excretion method uses a suitable dilution, usually 1 to 10 and any of the above methods for estimation. Fecal phosphorus includes both organic and inorganic phosphorus and thus usually estimated as total phosphorus in metabolic studies.