**7. Labeling of chelating agents with reduce technetium**

Technetium-99m after reduction forms reactive species and attains the ability to bind with a variety of chelating agents to generate the labeled product. In order to form the additive bond, normally, chelating agent donates the lone pairs of the electrons to make coordinate covalent bond with 99mTc. Compounds containing the electron donating group such as carboxylic group (dCOOH), amines (dNH2), hydroxyl (dOH), and thiol group (dSH) are good chelates such as DTPA (diethylenetriamine pentaacetic acid) and gluceptate.
