Diethylene Triamine Pentaacetic Acid (DTPA)

2015-1-13 6:18:01Chelated Products

Molecular Formula:C14H23N3O10

Molecular Weight:M=393.35

CAS NO.: 67-43-6

 

Pentetic acid or diethylene triamine pentaacetic 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, water-soluble solid.

 

Typical Physical and Chemical Properties:

Properties

Standards

Appearance

White Crystalline Powder

Purity

99.0% min

Chloride(Cl)

0.01% max

Sulfate(SO4)

0.05% max

Metal chelate(Pb)

0.001% max

Iron(Fe

 0.001% max

Loss on drying

 0.2% max

Chelate value(PH=11)mgCaCO3/g

252 min

PH(1% solution)

2.1-2.5

Sodium carbonate dissolved test

Qualified

 

Package:

-          1kg, 5kg aluminum bag with carton

-          25kg, 50lbs bag

-          Or according to the customer’s demand.

 

Coordination properties

The conjugate base of DTPA has a high affinity for metal cations. Thus, the penta-anion DTPA5− is potentially an octadentate ligand assuming that each nitrogen centre and each COO-group counts as a centre for coordination. The formation constants for its complexes are about 100 greater than those for EDTA.As a chelating agent, DTPA wraps around a metal ion by forming up to eight bonds. Transition metals, however, usually form less than eight coordination bonds. So, after forming a complex with a metal, DTPA still has the ability to bind to other reagents, as is shown by its derivative pendetide. For example, in its complex with copper(II), DTPA binds in a hexadentate manner utilizing the three amine centres and three of the five carboxylates.

Applications

Like the more common EDTA, DTPA is mainly used for sequestering metal ions that otherwise decompose hydrogen peroxide, which is used to bleach pulp in paper making. Several million kilograms are produced for this purpose annually.

Its chelating properties are useful in deactivating calcium and magnesium ions in hair products. DTPA is used in over 150 cosmetic products.Additionally, DTPA is used in MRI contrasting agents. DTPA improves MRI images by forming a complex with a gadolinium ion, which alters the properties of nearby water molecules.

DTPA has been considered for treatment of radioactive materials such as plutonium, americium, and other actinides. In theory, these complexes are more apt to be eliminated in urine. It is normally administered as the calcium or zinc salt, since these ions are readily displaced by more highly charged cations. DTPA forms complexes with thorium(IV), uranium(IV), neptunium(IV), and cerium(III/IV).

DTPA is also used as a chelate for aquarium plant fertilizer, specifically iron, an essential micronutrient typically needed in substantial quantities by all plants. Chelates are dissolved organic substances that bind to metals and prevent them from forming larger molecules through oxidation. FeDTPA is often sold under the name iron chelate 10% or 11% when used for the purpose of aquarium plant fertilization. Iron typically found in the aquarium water column has been converted into the ferric state (Fe+3) since it's in the presence of dissolved oxygen. However plants require iron in the ferrous state (Fe+2), therefore additional energy must be expended in order to extract the ferric iron from the water column and convert it to the ferrous form. When used to chelate iron fertilizer DTPA ensures that the iron is kept in the ferrous state (Fe+2) over time so it can be utilized by aquatic plants without expending valuable energy.

Related compounds

Compounds that are structurally related to DTPA are used in medicine, taking advantage of the high affinity of the triaminopentacarboxylate scaffold for metal ions.

In ibritumomab tiuxetan, the chelator tiuxetan is a modified version of DTPA whose carbon backbone contains an isothiocyanatobenzyl and a methyl group.

In capromab pendetide and satumomab pendetide, the chelator pendetide (GYK-DTPA) is a modified DTPA containing a peptide linker used to connect the chelate to anantibody.

Pentetreotide is a modified DTPA attached to a peptide segment.

DTPA and derivatives are used to chelate gadolinium to form a MRI contrast agent, such as Magnevist.

Technetium is chelated with DTPA for ventilation perfusion scan (V/Q scan) and renal scan.