Tetrasodium EDTA

Chelator that binds heavy-metal ions (calcium, iron, copper). In cosmetics it prevents oxidation of actives, rancidification of oils, and emulsion discolouration, and enhances preservative efficacy. Works at low concentrations – typically 0.05-0.2%. Raises ecological concerns (poor biodegradability), but alternatives such as Tetrasodium Glutamate Diacetate have emerged relatively recently.