EDTA

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Image:Ethylenediaminetetraacetic.png Image:Metal-EDTA.png Image:EDTA.JPG EDTA is the chemical compound ethylenediaminetetraacetic acid, otherwise known as edetate, versene, or diaminoethanetetraacetic acid disodium salt. EDTA is a chelating agent, forming coordination compounds with most monovalent, divalent, trivalent and tetravalent metal ions, such as silver (Ag⁺), calcium (Ca²⁺), copper (Cu²⁺), iron (Fe³⁺) or zirconium (Zr⁴⁺). EDTA contains 4 carboxylic acid and 2 tertiary amine groups that can participate in acid-base reactions. EDTA forms especially strong complexes with Ca, Cu, Fe(III), and Co(III).

EDTA has a molecular mass of 292.28 g/mol. Its CAS number is Template:CASREF and its SMILES structure is Template:SMILES.

1 Uses
2 Environmental behavior
3 Trivia
4 See also
5 External links

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Uses

The use of EDTA was about 35'000 tons in 1999 in Europe and 50'000 tons in the US. The most important uses are:

Industrial cleaning: complexation of Ca and Mg, binding of heavy metals.
Detergents: complexation of Ca and Mg (reduction of water hardness).
Photo-industry: use of Fe(III)EDTA as oxidizing agent.
Pulp and paper industry: complexation of heavy metals during chlorine-free bleaching, stabilization of hydrogen peroxide.
Textile industry: complexation of heavy metals, bleach stabilizer.
Agrochemicals: Fe, Zn and Cu fertilizer, especially in calcareous soils.
Hydroponics: iron-EDTA is used to prevent the iron from precipitating out of nutrient solutions.

Less important uses of EDTA are:

Food: added as preservative or stabilizer and for iron-fortification.
Personal care: added as preservatives to cosmetics.
Oil production: added into the borehole to inhibit mineral precipitation.
Dairy and beverage industry: cleaning of bottles from milk stains.
Flue gas cleaning: removal of NOx.
Medicine: used in chelation therapy (brand name Endrate®, marketed by Hospira, Inc.; generic product is also on the market) for acute hypercalcemia and mercury and lead poisoning.
Used in dentistry as a root canal irrigant to remove compounds of organic and inorganic debris (smearlayer).
Added to many soft drinks containing ascorbic acid and sodium benzoate to reduce the formation of benzene (a carcinogen).

In science EDTA is also used for:

Scavenging metal ions. In biochemistry and molecular biology, this is a common method to inactivate enzymes.
Complexometric titrations.
Buffer solutions.
Determination of water hardness.
Used in medical and laboratory equipment as an anticoagulant.

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Environmental behavior

Widespread use of EDTA and its slow removal under many environmental conditions has led to its standing as the anthropogenic compound at the highest concentration in many European surface waters. River concentrations in Europe are reported as 10-100 μg/L and lake concentrations are in the 1-10 μg/L range. EDTA concentrations in U.S. groundwater receiving wastewater effluent recharge was reported at 1-72 μg/L, and EDTA was found to be a conservative tracer, with higher concentrations of EDTA corresponding to a greater percentage of reclaimed water in drinking water production wells.

EDTA is not degraded nor removed during conventional wastewater treatment. However, an adjustment of pH and the sludge residence time can result in almost complete mineralization of EDTA. A variety of microorganisms has been isolated from water, soils, sediments and sludges that are able to completely mineralize EDTA as sole source of carbon, nitrogen and energy.

Recalcitrant chelating agents such as EDTA are an environmental concern predominately because of their persistence and strong metal chelation. The presence of chelating agents in high concentrations in wastewaters and surface waters has the potential to remobilize heavy metals out of river sediments and treated sludges, although low and environmentally relevant concentrations seem to have only a very minor influence on metal solubility. Elevated concentrations of chelating agents enhance the transport of metals (e.g. Zn, Cd, Ni, Cr, Cu, Pb, and Fe) in soils and enhance the undesired transport of radioactive metals away from disposal sites. Low concentrations of chelating agents may either stimulate planktic algae growth or decrease it while high concentrations inhibit activity. Chelating agents are nontoxic (measured as acute exposure) to many forms of life; long-term low-level exposure effects are unknown. EDTA at elevated concentrations is toxic to bacteria due to chelation of metals in the outer membrane. EDTA ingestion at high concentrations by mammals changes excretion of metals and can affect cell membrane permeability.

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Trivia

EDTA played a central role in O.J. Simpson trial when one of the blood samples collected from O.J. Estate was found to contain traces of the compound. This was used by the defense to indicate that the sample had been planted from one of the vials collected during the investigation. Prosecution claimed EDTA might have appeared in the sample as a result of eating McDonald's foods (either through bloodstream or, more likely, via contamination of blood flowing over the hand used in grabbing the food)
ethylenediaminetetraacetates is the longest hypothetically legal Scrabble word (hypothetical because it exceeds 15 letters, the width of a Scrabble board) in North American play
EDTA plays an important part in the 1998 vampire film "Blade", as it reacts violenty with vampire blood. This property is used to great effect by the eponymous hero.

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