ESET 122 Chemistry Applications and Climate Lecture 7B Nuclear Chemistry (Uses of Isotopes) Dr. Jovan Stefanovic Uses of Isotopes Chemical Analysis Isotopes, especially radioactive isotopes that are used to trace the path of the atoms of an element in a chemical or biological process, are called tracers. 2 Uses of Isotopes Isotopes in Medicine Tracers are used for diagnosis in medicine: • Sodium-24 injected into the bloodstream can detect possible constrictions or obstructions in the circulatory system. • Iodine-131 has been used to test the activity of the thyroid gland. • Iodine-123 is used to image the brain. • Technetium – 99m 3 Uses of Isotopes Isotopes in Medicine Technetium is one of the most useful elements in nuclear medicine. All its isotopes are radioactive. In the laboratory it is prepared by the nuclear reactions “m” denotes that Tc is in its 98 99 1 42Mo + 0n → 42Mo excited nuclear state . Mo - Molybdenum 99 99m 0 When excited atomic states decay, Mo → Tc + 𝛽 −1 42 43 energy is released by fluorescence. Or emits high-energy photons called gamma rays Technetium 99m or 99mTc is injected intravenously into the arm and images of the thyroid are obtained with a scintillation camera approximately 20 minutes later. The radionuclide emits gamma rays (photons) at a predictable rate. The camera is set to detect a predetermined minimum number of photons. Also images for heart , liver and lungs. 4 98 99 1 Mo + n → 0 42 42Mo 99 99m 0 Mo → Tc + −1𝛽 42 43 Ground state is 99Tc Molybdenum - 99 decay 5 Uses of Isotopes Boron Neutron Capture Therapy (BNCT) Boron -10 compound is selectively taken up by tumor cells and then applying beam of low energy neutrons to tumor side 10B capture a neutron to produce 11B , which disintegrates: The highly energetic particles produced by this reaction destroy the tumor cells in which the 10B is concentrated 6