DYSPROSIUM, CERIUM AND CHROMIUM MARKER DETERMINATION BY INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS

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Abstract
An instrumental neutron activation analysis (INAA) procedure has been developed for the measurement of dysprosium (Dy), cerium (Ce) and chromium (Cr) using the Canadian SLOWPOKE nuclear reactor. These elements were included in animal feed at 25 ppm, 61 ppm and 0.34%, respectively. Concentrations in feed and digesta samples were determined by measuring, with a Ge(Li) detector coupled to a 4096 multichannel analyzer, the radioactivity induced by neutron irradiation. Quantitative analysis procedures based on 165mDy (half-life:T1/2 = 1.26 min), 51Cr (T1/2 = 27.8 days) and 141Ce (T1/2 = 32.6 days) were developed after a study of the major contributions to induced background activity in both feed and fecal materials. For short irradiations, 28Al is the dominant induced background activity; for longer irradiations (> 2 h), 38Cl, 56Mn and 24Na dominate. Inert markers with radioisotopes of half-lives less than several minutes (165mDy) or longer than several days (51Cr and 141Ce) are most amenable to instrumental analysis. The application of the methods developed to routine analysis is discussed from the viewpoint of sample throughput and analysis time.
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