Devising a suitable combination of oxidation-reduction and separation methods became the key to the separation of the first transuranium elements. A radionuclide having multiple oxidation states can be purified by precipitating in one oxidation state followed by scavenging precipitations to remove impurities while the nuclide of interest is in the other oxidation state. The plutonium in solution is then reoxidized, more carrier is added, and the cycle is repeated. After a number of cycles, ultra-pure plutonium is obtained. The use of precipitation as a means of separation can be replaced with solvent extraction, adsorption, or ion exchange.
Radioactive purity can also be important.
In many cases, the radioactivity of the desired product nuclide constitutes only a small fraction of the emissions from the activated target material. Therefore, the nuclide of interest must be completely free from the radioactivity from other products in order to be identified. Ordinary separation techniques, such as precipitation, filtration, or centrifugation, may not be adequate to isolate such minute quantities. The following determination of radioactive ruthenium provides an example of activity analysis. A solution of mixed fission product activity was observed to have a total beta activity of 453,000 counts per minute per milliliter of solution.