Sodium triphosphate (STP), alsosodium tripolyphosphate (STPP), ortripolyphosphate (TPP),[1]) is aninorganic compound with formula Na5P3O10. It is thesodium salt of thepolyphosphate penta-anion, which is theconjugate base oftriphosphoric acid. It is produced on a large scale as a component of many domestic and industrial products, especially detergents. Environmental problems associated witheutrophication are attributed to its widespread use.[2]
Sodium tripolyphosphate is produced by heating a stoichiometric mixture ofdisodium phosphate, Na2HPO4, andmonosodium phosphate, NaH2PO4, under carefully controlled conditions.[2]
2 Na2HPO4 + NaH2PO4 → Na5P3O10 + 2 H2O
In this way, approximately 2 million tons are produced annually.[3]
STPP is a colourless salt, which exists both inanhydrous form and as the hexahydrate. The anion can be described as the pentanionic chain [O3POP(O)2OPO3]5−.[4][5] Many related di-, tri-, and polyphosphates are known including the cyclic triphosphate (e.g.sodium trimetaphosphate). It binds strongly to metal cations as both abidentate andtridentatechelating agent.
The majority of STPP is consumed as a component of commercialdetergents. It serves as a "builder", industrial jargon for a water softener. In hard water (water that contains high concentrations of Mg2+ and Ca2+), detergents are deactivated. Being a highly chargedchelating agent, TPP5− binds todications tightly and prevents them from interfering with the sulfonate detergent.[3]
High serum phosphate concentration has been identified as a predictor of cardiovascular events and mortality. Whilst phosphate is present in the body and food in organic forms, inorganic forms of phosphate such as sodium triphosphate are readily adsorbed and can result in elevated phosphate levels in serum.[15] Salts of polyphosphate anions are moderately irritating to skin and mucous membranes because they are mildly alkaline.[1]
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^Mallatt, Mark; Mankodi, Suru; Bauroth, Karen; Bsoul, Samer A.; Bartizek, Robert D.; He, Tao (September 2007). "A controlled 6-month clinical trial to study the effects of a stannous fluoride dentifrice on gingivitis".Journal of Clinical Periodontology.34 (9):762–767.doi:10.1111/j.1600-051X.2007.01109.x.PMID17645550.
