The pertechnetate ion is an oxoanion with the chemical formula TcO−
4. It is often used as a convenient water-soluble source of isotopes of the radioactive element technetium (Tc). In particular it is used to carry the 99mTc isotope (half-life 6 hours) which is commonly used in nuclear medicine in several nuclear scanning procedures.
A technetate(VII) salt is a compound containing this ion. Pertechnetate compounds are salts of technetic(VII) acid. Pertechnetate is analogous to permanganate but it has little oxidizing power. Pertechnetate has higher oxidation power than perrhenate.
|Formula||name||crystal structure||cell dimensions (Å)||unit cell volume (Å3)||remarks||references|
|LiTcO4·2H2O||lithium pertechnetate monohydrate|||
|LiTcO4·3H2O||lithium pertechnetate trihydrate||Pt3/mc|||
|NaTcO4||sodium pertechnetate||tetragonal||a = 5.342, c = 1.874||338.91||absorbs water from atmosphere|||
|NaTcO4·H2O||sodium pertechnetate monohydrate|||
|NaTcO4·2H2O||sodium pertechnetate dihydrate|||
|NaTcO4·4H2O||sodium pertechnetate tetrahydrate|||
|KTcO4||potassium pertechnetate||tetragonal||a = 5.647, c = 12.91||411.73||used to prepare radiopharmaceuticals|||
|RbTcO4||rubidium pertechnetate||tetragonal||a = 5.762, c =13.543||449.65|||
|α-CsTcO4||α-caesium pertechnetate||tetragonal||a = 5.898, c = 14.38||high temperature >470K; volatile at high temperatures|||
|β-CsTcO4||β-caesium pertechnetate||orthorhombic||a = 5.737, b = 5.92, c = 14.341||486.38|||
|TlTcO4||thallium pertechnetate||tetragonal||at high temperatures|||
|NH4TcO4||ammonium pertechnetate||tetragonal||technetium may be supplied in this form|||
- Radiolysis of TcO4− in nitrate solutions proceeds through the reduction to TcO42− which induces complex disproportionation processes:
- Pertechnetate can be reduced by H2S to give Tc2S7.
- Pertechnetate is also reduced to Tc(IV/V) compounds in alkaline solutions in nuclear waste tanks without adding catalytic metals, reducing agents, or external radiation. Reactions of mono- and disaccharides with 99mTcO4− yield Tc(IV) compounds that are water-soluble.
As a 99mTc carrier
A technetium-99m generator provides the pertechnetate containing the short-lived isotope 99mTc for medical uses. This compound is generated directly from molybdate held on alumina within the generator (see this topic for detail).
In nuclear medicine
Pertechnetate has a wide variety of uses in diagnostic nuclear medicine. Since technetate(VII) can substitute for iodine in the Na/I symporter (NIS) channel in follicular cells of the thyroid gland, inhibiting uptake of iodine into the follicular cells, 99mTc-pertechnetate can be used as an alternative to 123I in imaging of the thyroid, although it specifically measures uptake and not organification. It has also been used historically to evaluate for testicular torsion, although ultrasound is more commonly used in current practice, as it does not deliver a radiation dose to the testes. It is also used in labeling of autologus red blood cells for MUGA scans to evaluate left ventricular cardiac function, localization of gastrointestinal bleeding prior to embolization or surgical management, and in damaged red blood cells to detect ectopic splenic tissue.
It is actively accumulated and secreted by the mucoid cells of the gastric mucosa, and therefore, technetate(VII) radiolabeled with technetium-99m is injected into the body when looking for ectopic gastric tissue as is found in a Meckel's diverticulum with Meckel's scans.
All technetium salts are mildly radioactive, but some of them have explored use of the element for its chemical properties. In these uses, its radioactivity is incidental, and generally the least radioactive (longest-lived) isotopes of Tc are used. In particular, 99Tc (half-life 211,000 years) is used in corrosion research, because it is the decay product of the easily obtained commercial 99mTc isotope, which is its nuclear isomer. In theory, the longest-lived technetium isotope, 98Tc (half-life 4.2 million years), would be the optimal isotope for this use.
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