Ortofosfat

Ortofosfat, or orthophosphate, denotes the phosphate ion PO4^3− and its protonated forms H2PO4− and HPO4^2− that result from the stepwise dissociation of phosphoric acid (H3PO4) in water. Phosphate speciation is strongly pH-dependent, with pKa values around 2.15, 7.20, and 12.35 at 25°C. Orthophosphate represents the most readily available inorganic form of phosphorus for organisms and is a central component of key biomolecules such as ATP, nucleic acids, and phospholipids.

Chemically and geologically, orthophosphate occurs in minerals such as apatite and is released to soils and waters by weathering. In living systems, phosphorus cycles between organic and inorganic pools, and orthophosphate serves as the primary inorganic reservoir that organisms assimilate for growth, energy transfer, and signaling. The mobility and bioavailability of orthophosphate depend on pH, temperature, and competing ions, notably calcium and iron.

Industrial use centers on supplying phosphorus for agriculture and food production. Fertilizers such as monoammonium phosphate (MAP), diammonium phosphate (DAP), and triple superphosphate deliver orthophosphate to crops. It is also used as a food additive (acidity regulator and buffering agent), in detergents and cleaners, and in water treatment as a corrosion inhibitor and scale control agent.

Environmental concerns arise from phosphorus loadings that promote eutrophication in lakes and rivers. Orthophosphate is readily taken up by algae and aquatic plants, driving blooms, hypoxia, and biodiversity loss when discharged in effluent or runoff. Wastewater treatment and agricultural management aim to reduce orthophosphate releases through precipitation, adsorption, or biological phosphorus removal. Analytical methods include colorimetric molybdate-based assays and ion chromatography to distinguish orthophosphate from other phosphorus forms such as polyphosphates.