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KMID : 0378019740170040508
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New Medical Journal
1974 Volume.17 No. 4 p.508 ~ p.514
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Determination of Selenium and Copper in Feedstuffs By Radioactivation Analysis
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Lee Bou-Woung
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Abstract
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Author investigated neutron activation analysis for the determination of selenium and copper in feedstuffs. In the studies of traces elements, repeated quantitative analysis of the elements in feedstuffs is always necessary. Since selenium and copper were known to be essential for animal as trace elements the methods of a rapid and relatively cheap determination also is needed for these elements. Apart from the atomic absorption spectrometry, the neutron activation analysis now seems to be suitable method of analysing selenium and copper as this method requires little effort and time-consuming and yet it has but sensitivity and sufficient accuracy.
With activation analysis of selenium can be determined by using different isotopes. The most widely used nuclides is the 121-d Se-75. The calculated sensitivity of Se-75 is 6X104 microgram and put it requires a long activation and cooling time.
Se-81 isotopes with a standard sensitivity of 9X 104 microgram is also frequently used. As a pure emitter Se-81 needs a chemical separation. For all these radiochemical techniques, apart from the necessary time-consuming, a loss of some volatile selenium compounds during the dissolution must be taken into account.
There, author prefers the 17.5 sec, Se-77 isomer, which is activated by the reaction of Se-76, Se-77 with a cross-section of 22 barn, Se-77 emits easily measured gamma-ray of 0.161 MeV. Although the sensitivity is similar or even better, thisnuclide rarely has been used for activation analysis because of its rather short half-life. It provides, however, some remarkable advantages namely; 1) the short half-life and large cross-section make a high sensitivity possible, even at a very short irradation period, the matrix (mainly Na-24) mimimized, 3) the short irradiation and measuring time without complicated preparation of sample and chemical separation procedures, all of which render this method an extremly rapid method of analysis.
Multi-channel analyser (Gamma Scope 2 Model 101, 100 channel analyser, T. M. C. ) was used for non-destructive determination of Se-77.
In determination of copper, it can not be
as good as the nondestructive method of Se77; it should be preceded by chemical separation. Activating the Cu present in feedstuffs with neutron has the avantage of requiring only small sample for quantitative determination. Coppers present in a sample and in standard are activated with neutron to from Cu-64, which has a half-life of 12.8 hours and which emits beta and gamma radiation of 0. 57 and 1. 34 MeV, respectevely. Simultaneously Cu-66 with a half-life of 5.1 min is formed.
After sample digestion, Cu carrier is added and mixed with the acfive Cu.
Copper is then separated by chemical method and activities are counted by multi-channel analyser.
The chemical step takes about 2 hours for eight samples.
The chemical yield is about 75%.
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