Everything about Edta totally explained
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EDTA is a widely-used abbreviation for the
chemical compound ethylene diamine tetraacetic acid (and many other names, see table). EDTA refers to the
chelating agent with the
formula (HO
2CCH
2)
2NCH
2CH
2N(CH
2CO
2H)
2. This
amino acid is widely used to sequester di- and trivalent
metal ions. EDTA binds to metals via four
carboxylate and two
amine groups. EDTA forms especially strong complexes with Mn(II), Cu(II), Fe(III), and Co(III).
Synthesis
EDTA is mostly synthesised from 1,2-diaminoethane (
ethylenediamine), formaldehyde (methanal), water and sodium cyanide. This yields the tetra sodium salt, which can be converted into the acidic forms by acidification.
Pioneering work on the development of EDTA was undertaken by
Gerold Schwarzenbach in the 1940's.
Isomer
EDTA exists in different standard form under different conditions. At very low pH or very acidic condition (fully protonated)
H6Y+2 forms exist while at very high pH or very basic condition (fully deprotonated) Y-4 forms are prevalent .
Nomenclature
Popular vs. chemical nomenclature
To describe EDTA and its various
protonated forms, chemists use a more cumbersome but more precise acronym that distinguishes between EDTA
4−, the conjugate base that's the
ligand, and H
4EDTA, the precursor to that ligand.
Synonyms
EDTA is also known as H
4EDTA, diaminoethanetetraacetic acid, edetic acid, edetate, ethylenedinitrilotetraacetic acid, celon A, gluma cleanser, versene acid, nervanaid B acid, nullapon B acid, ethylene diamine tetracetic acid, tetrine acid, trilon BS, vinkeil 100, warkeelate acid, N,N'-1,2-ethanediylbis(N-(carboxymethyl)glycine)edetic acid, YD-30.
Coordination chemistry principles
In
coordination chemistry, H
4EDTA is a member of the aminocarboxylate family of ligands that includes
imidodiacetic acid ("H
2IDA") and nitrilotriacetic acid ("H
3NTA"). More specialized relatives include N,N'-ethylenediaminediacetic acid ("H
2EDDA") and 1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid ("H
4CyDTA"). These ligands are all formally derived from the
amino acid glycine.
H
4EDTA forms highly stable
coordination compounds that are soluble in water. In these complexes, the ligand is usually either hexa- or pentadentate, EDTA
4− or HEDTA
3−, respectively. Such complexes are
chiral, and [Co(EDTA)]
− has been resolved into
enantiomers.
Uses
In 1999, the annual consumption of EDTA was equivalent to about 35,000 tons in Europe and 50,000 tons in the US. The most important uses are:
- Industrial cleaning: complexation of Ca2+ and Mg2+ ions, binding of heavy metals.
- Detergents: complexation of Ca2+ and Mg2+ (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 solubilize iron in nutrient solutions.
More specialised uses of EDTA are:
Food: added as preservative to prevent catalytic oxidation by metal ions or stabilizer and for iron fortification.
Approved by the FDA as a preservative in packaged foods, vitamins, and baby food.
Personal care: added to cosmetics to improve product stability..
Combined with chromium, EDTA is used to evaluate kidney function. It is administered intravenously and its filtration into the urine is monitored. This method is considered the gold standard for evaluating glomerular filtration rate, Cr-EDTA's sole way out of the body is via glomerular filtration as it isn't secreted or metabolised in any other way.
Used as anticoagulant for blood samples
In veterinary ophthalmology EDTA may be used as an anticollagenase to prevent the worsening of corneal ulcers in animals.
Some laboratory studies also suggest that EDTA chelation may prevent collection of platelets ([orplaque] which can otherwise lead to formation of blood clots and prevent blood flow) on the walls of blood vessels [suchas arteries]. These ideas are theoretical, however a major clinical study of the effects of EDTA on coronary arteries is currently (2008) proceeding [3]
Dentistry as a root canal irrigant to remove inorganic debris (smear layer) and prepare root canals for obturation.
In laboratory science, EDTA is also used for:
Scavenging metal ions: in biochemistry and molecular biology, ion depletion is commonly used to inactivate metal-dependent enzymes which could damage DNA or proteins
Complexometric titrations.
Buffer solutions.
Determination of water hardness.
EDTA may be used as a masking agent to remove a metal ion which would interfere with the analysis of a second metal ion present
An anticoagulant in medical and laboratory equipment.
A preservative (usually to enhance the action of another preservative such as benzalkonium chloride or thiomersal) in ocular preparations and eyedrops. See "les conservateurs en opthalmologie" Doctors Patrice Vo Tan & Yves lachkar, Librarie Médicale Théa.
A titrant used to determine nickel concentration in an electroless nickel plating bath.
In metallography to remove staining due to etchants. Metal oxides are removed by gently swabbing with EDTA and rinsing in water.
In cell cultures EDTA is used as a chelating agent which binds to calcium and prevents joining of cadherins between cells, preventing cell clumping. (often used in cell culture control).
Toxicity
EDTA has been found to be both cytotoxic and weakly genotoxic in laboratory animals. Oral exposures have been noted to cause reproductive and developmental effects. The same study by Lanigan This method works with sample volumes as small as ~7-8 nL.
Forensics
EDTA played a role in the O.J. Simpson trial when one of the blood samples collected from Simpson's 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).Further Information
Get more info on 'Edta'.
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