EDTA

EDTA is the chemical compound ethylenediaminetetraacetic acid. EDTA or its disodium salt is a chelating agent, forming coordination compounds with most divalent (or trivalent) metal ions, such as calcium (Ca²⁺) and magnesium (Mg²⁺) or copper (Cu²⁺).

Uses

• Scavenging metal ions. In biochemistry and molecular biology, this is a common method to inactivate enzymes.
• Complexometric titrations
• Buffer solutions
• Determination of water hardness
• Use as a water softener.
• Used in medicine as a treatment for acute hypercalcemia and lead poisoning.
• Used in medical and laboratory equipment as an anticoagulant.
• Added to some processed foods and especially cosmetics as a preservative.
• A somewhat controversial therapy, called chelation therapy has evolved around metal scavengers such as EDTA.
• Used in dentistry as a root canal irrigant to remove compounds of organic and inorganic debris (smearlayer)
• Used in photography as a component of bleach-fix used to disolve elemental silver produced during development.
• Used as a soil conditioner to allow cacifuge plants to grow in base rich soils

Use as an anticoagulant

EDTA works as an anticoagulant by chelating all the calcium contained in blood. Calcium is needed for coagulation to occur; without calcium blood will not clot. The calcium levels below which clotting ceases are low enough to be lethal, so EDTA is only used as an anticoagulant outside the body; for instance in tubes of blood, and medical machinery.

EDTA is contained in purple, lavender and pink Vacutainer (tubes that blood is taken in), and can be in the form of a powder, or a small amount of liquid, already in the tube.

The sodium or potassium salts of EDTA (K₂EDTA, K₃EDTA, Na₂EDTA) are used in Vacutainer tubes. This means levels of these ions are increased, and detectable levels of calcium and magnesium are decreased. For this reason many clinical chemistry tests are not done using plasma from EDTA tubes.

External links

• pH-Spectrum of EDTA complexes
• EDTA: Molecule of the Month