EGTA (chemical)

EGTA is the chemical compound ethylene glycol tetraacetic acid, a chelating agent that is related to the better known EDTA, but with a much higher affinity for calcium than for magnesium ions. It is useful for making buffer solutions that resemble the environment inside living cells, where calcium ions are usually at least a thousandfold less concentrated than magnesium.

The pKa for binding of calcium ions by tetrabasic EGTA is 11.00, but the protonated forms do not significantly contribute to binding, so at pH 7, the apparent pKa becomes 6.91.

EGTA has also been used experimentally for the treatment of animals with cerium poisoning and for the separation of thorium from monazite. EGTA is used as a compound in elution buffer in the protein purification technique known as Tandem Affinity Purification (TAP), in which recombinant fusion proteins are bound to Calmodulin beads & eluted out by adding EGTA.