Etylenediaminetetraacetat

Etylenediaminetetraacetat, commonly known as ethylenediaminetetraacetate or EDTA, is a versatile chelating ligand used in chemistry, biology and medicine. In its fully protonated form, H4Y, the molecule consists of an ethylenediamine backbone bearing four acetate groups, with the formula C10H16N2O8. In aqueous solution it loses protons to form the tetraanionic Y4−, and it can bind metal ions through all six donor atoms (two amine nitrogens and four carboxylate oxygens), often yielding stable octahedral or related geometries.

Synthesis and forms: EDTA is prepared by stepwise alkylation of ethylenediamine with chloroacetate derivatives under basic conditions to yield the tetraacetate ligand. The metal salts of EDTA are common, including disodium EDTA and calcium disodium EDTA, among others. The speciation of the metal–EDTA complex depends on pH, giving several protonation and complexation states (H4Y, H3Y−, HY2−, Y4−).

Applications: As a strong chelating agent, EDTA forms stable complexes with a wide range of metal ions, such as Ca2+, Mg2+, Fe3+, Cu2+ and Pb2+, with binding strength and geometry influenced by pH. It is used in analytical chemistry to suppress interference from trace metals, in molecular biology and biochemistry in buffers (for example TE buffers) to protect enzymes and nucleic acids, in food and cosmetics as a preservative and stabilizer, and in medicine for chelation therapy to treat metal poisoning or to stabilize formulations. Its broad metal-binding properties and water solubility underpin its widespread use, though environmental and biological considerations regarding metal availability are important.