pyrophosphat

Pyrophosphat, or pyrophosphate, refers to the dianion P2O7^4− and the family of salts derived from it. It consists of two phosphate units linked by an anhydride bond, formed by condensation of two phosphate groups with the elimination of a water molecule. In aqueous solution the pyrophosphate ion exists in multiple protonation states depending on pH. Pyrophosphates form salts with many cations, including sodium, potassium, calcium, and magnesium; the most common laboratory and food-grade form is the sodium salt Na4P2O7, known as tetrasodium pyrophosphate.

Hydrolysis of pyrophosphate yields orthophosphate and proceeds rapidly under acidic or enzymatic conditions. In biology, pyrophosphate is produced in several biosynthetic reactions and is subsequently hydrolyzed by pyrophosphatase enzymes, which helps drive reactions such as nucleotide polymerization.

Biologically, PPi acts as a potential energy source and is involved in metabolism and mineralization processes; its hydrolysis is highly exergonic and helps push biosynthetic steps forward.

Industrial and commercial uses include as a food additive (E450) acting as a buffering, emulsifying, and sequestrant agent; in baking powders, it helps leavening; in detergents and water treatment it serves as a water-softening and stabilizing agent; in dental care, pyrophosphates help control tartar formation.

Regulatory status varies by jurisdiction; many pyrophosphate salts are widely regarded as safe at approved levels. Excessive ingestion may cause digestive discomfort in sensitive individuals; proper labeling is required for food applications.