Pertechnetate

Pertechnetate refers to the anion TcO4−, in which technetium is in the +7 oxidation state. It forms water-soluble salts such as sodium pertechnetate (NaTcO4), potassium pertechnetate (KTcO4), and ammonium pertechnetate (NH4TcO4). In solution, TcO4− is tetrahedral and acts as a relatively weakly coordinating, oxidizing species that is stable under mildly oxidizing conditions but can be reduced to lower oxidation states (for example TcO2 or TcO3) by reducing agents.

Production and occurrence: In medicine, pertechnetate is prepared from the technetium-99m generator as the eluted TcO4− solution, typically in saline. It serves as a convenient starting form for many radiopharmaceutical procedures after reduction and complexation. Outside medicine, pertechnetate is a common environmental form of technetium released from nuclear fission and reprocessing; TcO4− is highly soluble and mobile in groundwater, and long-lived 99Tc is a concern for long-term radiological contamination.

Medical uses: In nuclear medicine, 99mTcO4− is used for thyroid imaging, salivary gland imaging, and Meckel diverticulum scanning, among other applications. As a well-characterized starting species, it is often reduced and complexed to form a variety of Tc-labeled compounds used in diagnostic imaging. Its uptake in thyroid tissue is related to transport mechanisms that recognize iodide.

Safety and environmental aspects: Pertechnetate can be radioactive when derived from 99mTc or 99Tc. 99mTc provides diagnostic value with a short half-life, while 99Tc is long-lived, posing environmental considerations. As an anion, TcO4− is highly soluble and mobile in soil and groundwater, necessitating monitoring near nuclear facilities.