Radiochemistry

Radiochemistry is the branch of chemistry that studies radioactive substances, their production, chemical forms, and behavior, as well as the labeling and use of radionuclides as tracers or therapeutics. It sits at the interface of chemistry and nuclear physics and underpins the preparation of radiopharmaceuticals for research, diagnostics, and treatment.

Radioactivity was discovered in 1896 by Henri Becquerel, and work by Marie and Pierre Curie laid the foundations of radiochemical methods. Early researchers developed techniques to separate radionuclides and measure their decay, leading to precipitation, solvent extraction, and ion-exchange methods that could handle radioactive materials.

Radionuclides are produced in reactors, accelerators, and via generators. Common examples include 99mTc from a molybdenum-99 generator and PET isotopes such as 18F, 11C, and 13N produced in cyclotrons. Radiochemistry emphasizes the chemical form of the radionuclide to enable attachment to ligands, forming radiopharmaceuticals.

Key techniques include precipitation, solvent extraction and ion-exchange chromatography, as well as modern chromatographic methods to purify and quantify radiochemical species. Labels are typically verified for radiochemical purity and specific activity using radio-TLC and HPLC.

Applications include medical imaging and therapy, environmental tracing, and industrial use. Radiopharmaceuticals enable PET and SPECT scans and targeted radionuclide therapy. Safety and regulation require shielding, containment, waste handling, and adherence to ALARA principles.