The compound was first described in 1935 by Ferdinand Munz, who prepared the compound from ethylenediamine and chloroacetic acid.[2] Today, EDTA is mainly synthesised from ethylenediamine (1,2-diaminoethane), formaldehyde, and sodium cyanide.[3] This route yields the sodium salt, which can be converted in a subsequent step into the acid forms:
H2NCH2CH2NH2 + 4 CH2O + 4 NaCN + 4 H2O → (NaO2CCH2)2NCH2CH2N(CH2CO2Na)2 + 4 NH3
(NaO2CCH2)2NCH2CH2N(CH2CO2Na)2 + 4 HCl → (HO2CCH2)2NCH2CH2N(CH2CO2H)2 + 4 NaCl
In this way, about 80M kilograms are produced each year. Impurities cogenerated by this route include glycine and nitrilotriacetic acid; they arise from reactions of the ammonia coproduct.[4]
Nomenclature
To describe EDTA and its various protonated forms, chemists distinguish between EDTA4−, the conjugate base that is the ligand, and H4EDTA, the precursor to that ligand. At very low pH (very acidic conditions) the fully protonated H6EDTA2+ form predominates, whereas at very high pH or very basic condition, the fully deprotonated Y4− form is prevalent. In this article, the term EDTA is used to mean H4-xEDTAx-, whereas in its complexes edta4- stands for the tetra-deprotonated ligand.
EDTA is used to bind metal ions in the practice of chelation therapy, e.g., for treating mercury and lead poisoning.[11] It is used in a similar manner to remove excess iron from the body. This therapy is used to treat the complication of repeated blood transfusions, as would be applied to treat thalassaemia. Alternative medical practitioners believe EDTA acts as a powerful antioxidant to prevent free radicals from injuring blood vessel walls, therefore reducing atherosclerosis.[12] The U.S. FDA approved the use of EDTA for lead poisoning[13] on July 16, 1953, under the brand name of Versenate[14], which was licensed to the pharmaceutical company Riker. It has not approved it for the treatment of atherosclerosis.[15]
Dentists/endodontists use EDTA solutions to remove inorganic debris (smear layer) and lubricate the canals in endodontics. This procedure helps prepare root canals for obturation. Furthermore, EDTA solutions with the addition of a surfactant loosen up calcifications inside a root canal and allow instrumentation (canals shaping) and facilitate apical advancement of a file in a tight/calcified root canal towards the apex. It serves as a preservative (usually to enhance the action of another preservative such as benzalkonium chloride or thiomersal) in ocular preparations and eyedrops.[16] In evaluating kidney function, the complex [Cr(edta)]- is administered intravenously and its filtration into the urine is monitored. This method is useful for evaluating glomerular filtration rate.[17]
EDTA is used extensively in the analysis of blood. It is an anticoagulant for blood samples for CBC/FBEs.
Laboratory studies also suggest that EDTA chelation may prevent collection of platelets on the lining of the vessel [such as arteries] (which can otherwise lead to formation of blood clots, which itself is associated with atheromatous plaque formation or rupture, and thereby ultimately disrupts blood flow). These ideas have so far been proven ineffective;[18] however, a major clinical study of the effects of EDTA on coronary arteries is currently (2008) proceeding.[19] EDTA played a role in the O.J. Simpson trial when the defense alleged that one of the blood samples collected from Simpson’s estate was found to contain traces of the compound.[20]
EDTA is a slime dispersant, and has been found to be highly effective in reducing bacterial growth during implantation of intraocular lenses (IOLs).[21]
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