13.7 Chromatography
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widely used for the separation of lanthanides and actinide elements, whose chemical properties are very similar. For example, Choppin and his co-workers separated
the transuranic elements from sameracium, by the ion-exchange method. They used
Dowerex-50 cation-exchanger at an elevated temperature (80
◦ C). A constant temperature was maintained by enclosing the ion-exchange column in the vapors of
trichloroethylene (B.P. 80
◦ C). Ammonium lactate complexing solution was used
to elute the ion-exchanger and each drop of the elute was collected separately, a
source was prepared from each and counted. A histogram of activity present in each
drop eluted from the column versus the number of drops removed from the column
showed that the elements had been separated and came from the column in reverse
order of their atomic number.
13.7.4 Nuclear Recoil-Method
It is sometimes possible to separate the products of the nuclear reaction by making use
of the nuclear recoil phenomenon. The nuclei of the recoiling fragments may travel
rather a long way in the target material and may leave it altogether if the target material
is less than the range of the energetic fragments. For example, Wolfgang separated
fission products from Neptunium-239 and Uranium-239, using U 3 O 8 (particle size
one micron) as target material. The fine particles of U 3 O 8 were prepared in gelatinous
suspension and were irradiated in a neutron source (nuclear reactor). The gelatin was
then liquefied and the mixture was centrifuged. The supernatant liquid contained
the fission products, whereas Neptunium-239 remained in the uranium oxide. The
separation gave a carrier-free Neptunium-239, free from fission products, after the
decay of Uranium-239 (T 0.5 23.5 min.).
13.8 Activation Analysis
In chemical analysis, the degree of accuracy depends upon the method of analysis.
In cases where chemical method of separation is not available; usually activation
analysis is tried. One of the important applications of nuclear reactions in analytical
chemistry is also the activation analysis. This method is based on the principle
that radioactive nuclides are formed by the interaction of a nuclear particle with
an element which has an appreciable ability for the reaction to occur. This ability is
measured in terms of cross-section for the nuclear reaction. The induced activity due
to nuclear reaction is then detected and measured to determine the amount of element
present in the sample material to be analyzed. This type of analysis is basically useful
because of the following factors:
1. Each radioactive isotope emits a characteristic radiation and its energy can be
taken as evidence to identify the nuclide.
211
widely used for the separation of lanthanides and actinide elements, whose chemical properties are very similar. For example, Choppin and his co-workers separated
the transuranic elements from sameracium, by the ion-exchange method. They used
Dowerex-50 cation-exchanger at an elevated temperature (80
◦ C). A constant temperature was maintained by enclosing the ion-exchange column in the vapors of
trichloroethylene (B.P. 80
◦ C). Ammonium lactate complexing solution was used
to elute the ion-exchanger and each drop of the elute was collected separately, a
source was prepared from each and counted. A histogram of activity present in each
drop eluted from the column versus the number of drops removed from the column
showed that the elements had been separated and came from the column in reverse
order of their atomic number.
13.7.4 Nuclear Recoil-Method
It is sometimes possible to separate the products of the nuclear reaction by making use
of the nuclear recoil phenomenon. The nuclei of the recoiling fragments may travel
rather a long way in the target material and may leave it altogether if the target material
is less than the range of the energetic fragments. For example, Wolfgang separated
fission products from Neptunium-239 and Uranium-239, using U 3 O 8 (particle size
one micron) as target material. The fine particles of U 3 O 8 were prepared in gelatinous
suspension and were irradiated in a neutron source (nuclear reactor). The gelatin was
then liquefied and the mixture was centrifuged. The supernatant liquid contained
the fission products, whereas Neptunium-239 remained in the uranium oxide. The
separation gave a carrier-free Neptunium-239, free from fission products, after the
decay of Uranium-239 (T 0.5 23.5 min.).
13.8 Activation Analysis
In chemical analysis, the degree of accuracy depends upon the method of analysis.
In cases where chemical method of separation is not available; usually activation
analysis is tried. One of the important applications of nuclear reactions in analytical
chemistry is also the activation analysis. This method is based on the principle
that radioactive nuclides are formed by the interaction of a nuclear particle with
an element which has an appreciable ability for the reaction to occur. This ability is
measured in terms of cross-section for the nuclear reaction. The induced activity due
to nuclear reaction is then detected and measured to determine the amount of element
present in the sample material to be analyzed. This type of analysis is basically useful
because of the following factors:
1. Each radioactive isotope emits a characteristic radiation and its energy can be
taken as evidence to identify the nuclide.