[Neutron activation analysis of selenium using a coincidence counting method (author's transl)].

Neutron activation analysis of selenium using 75Se has been investigated by means of a coincidence counting of gamma-rays in the cascade decay series by a NaI(TI) detector and a Ge(Li) detector. Using this method, the background around the photopeak of 75Se-265 keV could be reduced to one twentieth, and thus the detection limit of selenium could be improved four times higher than the usual method. For examining the accuracy of this measuring method, selenium contained in Bovine Liver (NBS) was determined and the content of selenium was found to be 1.02 micrograms/g (the certified value is 1.1 +/- 0.01 micrograms/g). Selenium content in Orchard Leaves (NBS) was determined to be 0.081 +/- 0.006 micrograms/g (the certified value is 0.08 +/- 0.01 micrograms/g), though its non-destructive determination was difficult because of its very low content. The results obtained here indicate that the accuracy, the precision and the reproducibility for selenium determination are thought to be adequate. As an example of a sample containing many interference nuclides, selenium in a soot was determined on the basis of these results.