Pentasodium Triphosphate

Pentasodium triphosphate (also called STPP — sodium tripolyphosphate) is an inorganic phosphate salt widely used as a builder in cleaning formulations. It chelates divalent cations (Ca²⁺, Mg²⁺), preventing hard water interference with surfactants. At typical cleaning concentrations (0.5–3%), it provides mild alkaline buffering without the corrosive hazard of sodium hydroxide. Environmental concern centers on eutrophication: phosphate discharged to waterways promotes algal blooms. Many regions have restricted phosphates in household cleaners for this reason, though automotive cleaning products remain largely unregulated. Hydrolyzes in water to orthophosphate, which is assimilable by organisms (biodegradable). Not classified as aquatically toxic under GHS criteria.