BAPTA tetrasodium is a selective chelator for calcium . BAPTA tetrasodium, as calcium indicator, has high selectivity against magnesium and calcium. BAPTA tetrasodium is widely used as an intracellular buffer for investigating the effects of Ca 2+ release from intracellular stores or influx via Ca 2+ -permeable channels in the plasma membrane. BAPTA tetrasodium can also inhibit phospholipase C activity independently of their role as Ca 2+ chelators.