EDTA

Encyclopedia : E : ED : EDT : EDTA

''''''
Chemical name
Other names	EDTA Edetic acid Edetate Diaminoethanetetraacetic acid Versene
Chemical formula
Molecular mass
CAS number
Density	3
Melting point
SMILES
Hazards
MSDS	[External MSDS]
Main hazards	?
NFPA 704
Flash point	?
R/S statement	R: ?. S: ?.
RTECS number	?
[Chemical infoboxDisclaimer and references]

EDTA is the chemical compound ethylenediaminetetraacetic acid. EDTA is a chelating agent, forming coordination compounds with most monovalent, divalent, trivalent and tetravalent metal ions, such as silver (Ag⁺), calcium (Ca²⁺), manganese (Mn²⁺), copper (Cu²⁺), iron (Fe³⁺) and 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 Mn, Cu, Fe(III), and Co(III).

Uses

Metal-EDTA chelate

Annual consumption of EDTA is 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 ions, binding of heavy metals.
• Detergents: complexation of Ca and Mg (reduction of water hardness).
• Photography: 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.

• Food: added as preservative or stabilizer and for iron fortification.
• Personal care: added to cosmetics to work in synergy with preservatives and to improve product stability.
• 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; generic product is also on the market) for acute hypercalcemia and mercury and has been used for 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).
• Can be used in the recovery of used lead acid batteries.

• Scavenging metal ions: in biochemistry and molecular biology, ion depletion is commonly used to inactivate enzymes which could damage DNA.
• Complexometric titrations.
• Buffer solutions.
• Determination of water hardness.
• Used in medical and laboratory equipment as an anticoagulant.

Environmental behavior

This is a computer generated image of EDTA's 3-dimensional structure. Red atoms are hydrogen, blue atoms are oxygen, green atoms are nitrogen, and grey atoms are carbon.

Widespread use of EDTA and its slow removal under many environmental conditions has led to its status as the most abundant anthropogenic compound 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 discharge have been reported at 1-72 μg/L, and EDTA was found to be an effective tracer for effluent, with higher concentrations of EDTA corresponding to a greater percentage of reclaimed water in drinking water production wells.

EDTA is not degraded or removed during conventional wastewater treatment. However, an adjustment of pH and sludge residence time can result in almost complete mineralization of EDTA. A variety of microorganisms have been isolated from water, soils, sediments and sludges that are able to completely mineralize EDTA as a sole source of carbon, nitrogen and energy.

Recalcitrant chelating agents such as EDTA are an environmental concern predominantly because of their persistence and strong metal chelating properties. The presence of chelating agents in high concentrations in wastewaters and surface waters has the potential to remobilize heavy metals from 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 or decrease plankton or algae growth, while high concentrations always inhibit activity. Chelating agents are nontoxic to many forms of life on acute exposure; the effects of longer-term low-level exposure 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.

Trivia

• EDTA played a central role in the 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

See also

• EGTA
• BAPTA
• NTA
• Phosphonate

External links

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

• For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.