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Pentetic acid or diethylenetriaminepentaacetic acid ( DTPA) is an aminopolycarboxylic acid consisting of a diethylenetriamine backbone with five carboxymethyl groups. The molecule can be viewed as an expanded version of EDTA and is used similarly. It is a white solid with limited solubility in water.
The distinction between H5DTPA, "DTPA", and DTPA5− is often not explicit.
DTPA has been considered for treatment of radioactive materials such as plutonium, americium, and other . In theory, these complexes are more apt to be eliminated in urine. It is normally administered as the calcium or zinc salt (Ca or Zn-DTPA), since these ions are readily displaced by more highly charged cations and mainly to avoid to depleting them in the organism. DTPA forms complexes with thorium(IV), uranium(IV), neptunium(IV), and cerium(III/IV).(2) Brown, M. A.; Paulenova, A.; Gelis, A. V. "Aqueous Complexation of Thorium(IV), Uranium(IV), Neptunium(IV), Plutonium(III/IV), and Cerium(III/IV) with DTPA" Inorganic Chemistry 2012, volume 51, 7741-7748.
In August, 2004 the U.S. US Food and Drug Administration (USFDA) determined zinc-DTPA and calcium-DTPA to be safe and effective for treatment of those who have breathed in or otherwise been contaminated internally by plutonium, americium, or curium. The recommended treatment is for an initial dose of calcium-DTPA, as this salt of DTPA has been shown to be more effective in the first 24 hours after internal contamination by plutonium, americium, or curium. After that time has elapsed both calcium-DTPA and zinc-DTPA are similarly effective in reducing internal contamination with plutonium, americium or curium, and zinc-DTPA is less likely to deplete the body's normal levels of zinc and other metals essential to health. Each drug can be administered by nebulizer for those who have breathed in contamination, and by intravenous injection for those contaminated by other routes.
Gadolinium (Gd3+)-DTPA compounds are MRI Contrast agent.Caravan, Peter; Ellison, Jeffrey J.; McMurry, Thomas J. ; Lauffer, Randall B. "Gadolinium(III) Chelates as MRI Contrast Agents: Structure, Dynamics, and Applications" Chem. Revs. 1999, volume 99, pp. 2293–2342.
DTPA under the form of iron(II) chelate (Fe-DTPA, 10 – 11 wt. %) is also used as Aquascaping fertilizer. The more soluble form of iron, Fe(II), is a micronutrient needed by . By binding to Fe2+ ions DTPA prevents their precipitation as Fe(OH)3, or Fe2O3 · n H2O poorly soluble oxy-hydroxides after their Redox by dissolved oxygen. It increases the solubility of Fe2+ and Fe3+ ions in water, and therefore the bioavailability of iron for aquatic plants. It contributes so to maintain iron under a dissolved form (probably a mix of Fe(II) and Fe(III) DTPA complexes) in the water column. It is unclear to what extent does DTPA really contribute to protect dissolved Fe2+ against air oxidation and if the Fe(III)-DTPA complex cannot also be directly assimilated by aquatic plants simply because of its enhanced solubility. Under natural conditions, i.e., in the absence of complexing DTPA, Fe2+ is more easily assimilated by most organisms, because of its 100-fold higher solubility than that of Fe3+.
In pulp mill DTPA is also used to remove dissolved ferrous and ferric ions (and other redox-active metal ions, such as manganese or copper) that otherwise would accelerate the Catalysis decomposition of hydrogen peroxide (H2O2 reduction by Fe2+ ions according to the Fenton reaction mechanism). This helps preserving the Redox capacity of the hydrogen peroxide stock which is used as oxidizing agent to bleach pulp in the chlorine-free process of paper making.Colodette, J. L. (1987). Factors affecting hydrogen peroxide stability in the brightening of mechanical and chemi-mechanical pulps (Doctoral dissertation, State University of New York College of Environmental Science and Forestry). Several thousands tons of DTPA are produced annually for this purpose in order to limit the non-negligible losses of H2O2 by this mechanism.
DTPA chelating properties are also useful in deactivating calcium and magnesium ions in hair products. DTPA is used in over 150 cosmetic products.Burnett, L. C. "Final Report on the Safety Assessment of Pentasodium Pentetate and Pentetic Acid as Used in Cosmetics" International Journal of Toxicology 2008, 27, 71-92.
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