 | |
 | |
| Names | |
|---|---|
| IUPAC name Sodium technetate(VII) | |
| Other names sodium tetraoxotechnetate (VII) | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.033.870 |
| EC Number |
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| UNII | |
| |
| |
| Properties | |
| NaTcO4 | |
| Molar mass | 169.89 g/mol |
| Appearance | White or pale pink solid |
| Melting point | < 1,063 K (790 °C; 1,454 °F)[1] |
| Soluble | |
| Structure[1] | |
| Scheelite | |
| I41/a | |
a = 5.3325(1) Å,c = 11.8503(3) Å | |
Formula units (Z) | 4 |
| Related compounds | |
Otheranions | Sodium permanganate;sodium perrhenate |
Othercations | Ammonium pertechnetate |
Related compounds | Technetium heptoxide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Sodium pertechnetate is theinorganic compound with the formula NaTcO4. This colourless salt contains thepertechnetate anion,TcO−
4 that has slightly distorted tetrahedron symmetry both at 296 K and at 100 K[2] while the coordination polyhedron of thesodium cation is different from typical forscheelite structure. The radioactive99m
TcO−
4 anion is an importantradiopharmaceutical fordiagnostic use. The advantages to99m
Tc include its shorthalf-life of 6 hours and the low radiation exposure to the patient, which allow a patient to be injected with activities of more than 30 millicuries (1,100 MBq).[3]Na[99m
TcO
4] is a precursor to a variety of derivatives that are used to image different parts of the body.
TcO−
4 is the starting material for most of the chemistry of technetium. Pertechnetate salts are usually colorless.[4]TcO−
4 is produced by oxidizing technetium with nitric acid or with hydrogen peroxide. The pertechnetate anion is similar to thepermanganate anion but is a weakeroxidizing agent. It is tetrahedral and diamagnetic. The standard electrode potential forTcO−
4/TcO
2 is only +0.738 V in acidic solution, as compared to +1.695 V forMnO−
4/MnO
2.[3] Because of its diminished oxidizing power,TcO−
4 is stable in alkaline solution.TcO−
4 is more similar toReO−
4. Depending on the reducing agent,TcO−
4 can be converted to derivatives containing Tc(VI), Tc(V), and Tc(IV).[5] In the absence of strong complexing ligands,TcO−
4 is reduced to a +4 oxidation state via the formation ofTcO
2 hydrate.[3]
The half-life of99m
Tc is long enough that labelling synthesis of theradiopharmaceutical and scintigraphic measurements can be performed without significant loss of radioactivity.[3] The energy emitted from99m
Tc is 140 keV, which allows for the study of deep body organs. Radiopharmaceuticals have no intended pharmacologic effect and are used in very low concentrations. Radiopharmaceuticals containing99m
Tc are currently being applied in the determining morphology of organs, testing of organ function, and scintigraphic and emission tomographic imaging. The gamma radiation emitted by the radionuclide allows organs to be imagedin vivo tomographically. Currently, over 80% of radiopharmaceuticals used clinically are labelled with99m
Tc. A majority of radiopharmaceuticals labelled with99m
Tc are synthesized by the reduction of the pertechnetate ion in the presence of ligands chosen to confer organ specificity of the drug. The resulting99m
Tc compound is then injected into the body and a "gamma camera" is focused on sections or planes in order to image the spatial distribution of the99m
Tc.
99m
Tc is used primarily in the study of the thyroid gland - its morphology, vascularity, and function.TcO−
4 andiodide, due to their comparable charge/radius ratio, are similarly incorporated into the thyroid gland. The pertechnetate ion is not incorporated into thethyroglobulin. It is also used in the study of blood perfusion, regional accumulation, and cerebral lesions in the brain, as it accumulates primarily in thechoroid plexus.
Sodium pertechnetate cannot pass through theblood–brain barrier. In addition to the salivary and thyroid glands,99m
TcO−
4 localizes in the stomach.99m
TcO−
4 is renally eliminated for the first three days after being injected. After a scanning is performed, it is recommended that a patient drink large amounts of water in order to expedite elimination of the radionuclide.[6] Other methods of99m
TcO−
4 administration include intraperitoneal, intramuscular, subcutaneous, as well as orally. The behavior of the99m
TcO−
4 ion is essentially the same, with small differences due to the difference in rate of absorption, regardless of the method of administration.[7]
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