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For other uses, see EDTA (disambiguation).
EDTA
Ball and stick model of the EDTA molecule, in the zwitterionic form found in the solid state
IUPAC name 2-[2-(Bis(carboxymethyl)amino)ethyl-(carboxymethyl)amino]acetic acid
Other names EDTA, H4EDTA, Diaminoethanetetraacetic acid, Edetic acid, Edetate, Ethylenedinitrilotetraacetic acid, Versene, Ethylene diamine tetraacetic acid
Identifiers
CAS number 60-00-4
PubChem 6049
RTECS number AH4025000
SMILES
 
ChemSpider ID 5826
Properties
Molecular formula C10H16N2O8
Molar mass 292.24 g/mol
Density 0.86 g/cm³
Melting point

237-245 °C (dec.)
Acidity (pKa) pK1=0.0 (CO2H)
pK2=1.5 (CO2H)
pK3=2.00 (CO2H)
pK4=2.69 (CO2H)
pK5=6.13 (NH+)
pK6=10.37 (NH+)
Hazards
MSDS External MSDS
Main hazards irritant
NFPA 704
0
1
0
 
R-phrases R36
S-phrases S26
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox references

EDTA is a widely used abbreviation for the chemical compound ethylenediaminetetraacetic acid (and many other names, see table). EDTA refers to the chelating agent with the formula (HO2CCH2)2NCH2CH2N(CH2CO2H)2. This amino acid is widely used to sequester di- and trivalent metal ions (Ca2+ and Mg2+ for example). EDTA binds to metals via four carboxylate and two amine groups. EDTA forms especially strong complexes with Mn(II), Cu(II), Fe(III), Pb (II) and Co(III).1

Contents

Synthesis

EDTA is mostly synthesised from 1,2-diaminoethane (ethylenediamine), formaldehyde (methanal), water and sodium cyanide.2 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 1940s.3

Isomer

EDTA exists in different standard forms 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 EDTA4−, the conjugate base that is the ligand, and H4EDTA, the precursor to that ligand.

Synonyms

EDTA is also known as H4EDTA, 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, Dissolvine Z.

Coordination chemistry principles

Metal-EDTA chelate

In coordination chemistry, H4EDTA is a member of the aminocarboxylate family of ligands that includes imidodiacetic acid ("H2IDA") and nitrilotriacetic acid ("H3NTA"). More specialized relatives include N,N'-ethylenediaminediacetic acid ("H2EDDA") and 1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid ("H4CyDTA"). These ligands are all formally derived from the amino acid glycine.

H4EDTA forms highly stable coordination compounds that are soluble in water. In these complexes, the ligand is usually either hexa- or pentadentate, EDTA4− or HEDTA3−, respectively. Such complexes are chiral, and [Co(EDTA)]− has been resolved into enantiomers.4

Uses

In 1999, the annual consumption of EDTA was equivalent to about 35,000 tons in Europe and 50,000 tons in the US.citation needed The most important uses are:

  • Industrial cleaning
complexation of Ca2+ and Mg2+ ions, binding of heavy metals.
complexation of Ca2+ and Mg2+ (reduction of water hardness).
use of Fe(III)EDTA as oxidizing agent.
complexation of heavy metals during chlorine-free bleaching, stabilization of hydrogen peroxide.
complexation of heavy metals, bleach stabilizer.
Fe, Zn and Cu fertilizer, especially in calcareous soils.
iron-EDTA is used to solubilize iron in nutrient solutions.

More specialised uses

  • Food
added as preservative to prevent catalytic oxidation by metal ions or stabilizer and for iron fortification.5
  • Approved by the FDA as a preservative in packaged foods, vitamins, and baby food.citation needed
  • Personal care
added to cosmetics to improve product stability.6
  • Oil production
added into the borehole to inhibit mineral precipitation.citation needed
  • Dairy and beverage industry
cleaning milk stains from bottles.citation needed
removal of NOx.
recovery of lead from used lead acid batteries.

Medicine

Laboratory science

  • 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.
  • 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.6 The same study by Lanigan6 also found that both dermal exposure to EDTA in most cosmetic formulations and inhalation exposure to EDTA in aerosolized cosmetic formulations would produce systemic effects below those seen to be toxic in oral dosing studies.

Environmental behavior

EDTA coordinating a Cu2+ ion

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.citation needed 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. 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.

Other more biodegradable chelators are effective and available. For example, EDDS (S, S'-ethylenediaminedisuccinic acid) and NTA (nitrilotriacetic acid).

Methods of detection and analysis

The most sensitive method of detecting and measuring EDTA in biological samples is selected-reaction-monitoring capillary-electrophoresis mass-spectrometry (abbreviation SRM-CE/MS) which has a detection limit of 7.3 ng/mL in human plasma and a quantitation limit of 15 ng/mL.10 This method works with sample volumes as small as ~7-8 nL.10

EDTA has also been measured in non-alcoholic beverages using high performance liquid chromatography (HPLC) which has a detection limit of 0.6 μg/mL and a quantitation limit of 2.0 μg/mL.1112

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)citation needed.

See also

References

Endnotes

  1. ^ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5. 
  2. ^ Synthesis of EDTA
  3. ^ Edta - Motm
  4. ^ Kirchner, S. Barium (Ethylenediaminetetracetato) Cobalt(III) 4-Hydrate" Inorganic Syntheses, McGraw-Hill: New York, 1957; Vol. 5, pages 186-188.
  5. ^ Furia T (1964). "EDTA in Foods — A technical review". Food Technology 18 (12): 1874–1882. 
  6. ^ a b c Lanigan RS and Yamarik TA (2002). "Final report on the safety assessment of EDTA, calcium disodium EDTA, diammonium EDTA, dipotassium EDTA, disodium EDTA, TEA-EDTA, tetrasodium EDTA, tripotassium EDTA, trisodium EDTA, HEDTA, and trisodium HEDTA". Int J Toxicol. 21 Suppl 2: 95–142, http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=12396676&dopt=AbstractPlus. Retrieved on 28 January 2008. 
  7. ^ US Food and Drug Administration: Center for Food Safety and Applied Nutrition Questions and Answers on the Occurrence of Benzene in Soft Drinks and Other Beverages
  8. ^ Ruth DeBusk et al. (2002). "Ethylenediaminetetraacetic acid (EDTA)". Retrieved on 2007-07-25.
  9. ^ |http://www.clinicaltrials.gov/ct/show/NCT00044213?order=2
  10. ^ a b Robin L. Sheppard, and Jack Henion (1997). "Determining EDTA in Blood". Analytical Chemistry 69: 477A–480A, http://pubs.acs.org/hotartcl/ac/97/aug/det.html. Retrieved on 25 July 2007. 
  11. ^ S. Loyaux-Lawniczak, J. Douch, and P. Behra (1999). "Optimisation of the analytical detection of EDTA by HPLC in natural waters". Fresenius' J. Anal. Chem. 364 (8): 727–731. doi:10.1007/s002160051422. ISSN 0937-0633, http://cat.inist.fr/?aModele=afficheN&cpsidt=1898737. Retrieved on 25 July 2007. 
  12. ^ Carolina E. Cagnassoa, Laura B. López, Viviana G. Rodríguez and Mirta E. Valencia (May 2006). "Development and validation of a method for the determination of EDTA in non-alcoholic drinks by HPLC". Journal of Food Composition and Analysis 20 (3-4): 248. doi:10.1016/j.jfca.2006.05.008. 

Notations

  • A Textbook on EDTA Chelation Therapy, Linus Pauling, Hampton Roads Publishing, Charlottsville, VA

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