Radiochemistry
The radiochemistry is a branch of chemistry . While this is, in the broadest sense, the part of chemistry that generally deals with radioactive substances, radiochemistry is often only understood to mean that part of nuclear chemistry , the chemical and physico-chemical methods for the production, representation (separation) and application of radioactive substances Nuclides used, for example, for processing nuclear fuel or in tracer processes in biology and medicine.
Examples of how radiochemistry works can be found in the article Discovery of Nuclear Fission .
If the activity exceeds about 100 GBq , the jargon also speaks of “hot chemistry”.
Applications
Indicator method or tracer method
This involves replacing a certain atom in a chemical compound with a radionuclide . This makes it possible to follow a chemical reaction or a transport process.
Examples:
- Lead iodide marked with 131 I , whose activity is known, can be used to monitor the establishment of the solution equilibrium in water and thus determine the solubility product .
- Investigation of mechanisms via molecules labeled with 14 C
- Investigation of assimilation processes above 14 CO 2
Radioactive age determination
The radioactive decay law makes it possible to determine the time required for this by setting a certain proportion of the initial and decay products. A well-known method is radiocarbon dating . Furthermore, the age of geological samples can be determined using the following methods:
- Rubidium-Strontium process over 87 Rb and 87 Sr
- Uranium-lead method using the ratio of 206 Pb from 238 U and 207 Pb from 235 U
- Uranium-helium method, whereby the helium from 238 U is determined in the rock
- Potassium-argon process using the ratio of 40 K and the 40 Ar resulting from the potassium
Analytical methods
The use of radionuclides in analytical chemistry requires greater detection sensitivity. A distinction is made between:
- Analysis based on natural radioactivity e.g. B. for the determination of potassium in mineral salts
- Dilution analysis: In this case, a known amount of indicator molecules (same type of molecule with known activity) is added to a substance with an unknown amount of molecules and mixed completely. Then a certain amount of substance is removed and the activity of the mixture is determined. From this you can then calculate the unknown amount. One application is e.g. B. the radioimmunoassay (RIA) for the determination of traces of antigens , hormones and drugs in the blood serum.
- Activation analysis: It is based on the fact that the activity of a radionuclide produced by a nuclear reaction is determined and thus the amount of radionuclide present in the sample is calculated. The activation often takes place by neutrons in a nuclear reactor or with a special neutron source .
Diagnostics in medicine
This exploits the property that certain organs and tumors absorb radionuclides differently. A color scintigram of the organ is then created by determining the emitted gamma quanta . Nuclear medicine deals with the corresponding procedures .
literature
- H. Götte, G. Kloss: Nuclear Medicine and Radiochemistry, Angew. Chem. 85th 1973, No. 18, p. 793
- C. Keller: Fundamentals of Radiochemistry, Salle & Sauerländer 3rd edition 1993, ISBN 3-7935-5487-2
- C. Keller (Ed.): Experiments for Radiochemistry, Diesterweg & Salle & Sauerländer 1st edition 1980, ISBN 3-425-05453-8
- Entry on radiochemistry. In: Römpp Online . Georg Thieme Verlag, accessed on June 14, 2014.