Post-irradiation chemistry of selenium in neutron activation analysis

Abstract

Chemical procedures were studied for high recovery and reproducible separation of selenium in post-irradiation chemistry in neutron activation analysis. Distillation followed by solvent extraction was used for separation of selenium in this paper. Distillation of selenium from HCl-HBr solution containing 30 ml each of 12N HCl and 8.6N HBr in 110 ml, which enables selenium to be distilled off as volatile halides, was employed for elimination of materials that interfere solvent extraction and of almost all interfering radioactive nuclides except those of Hg, Sb, etc. produced by thermal neutron irradiation. Recovery of selenium in this distillation was (99.6±0.3)%. Selenium was then extracted with benzene from aqueous phase(12N HCl 15ml, 60% HClO₄ 15ml), mainly as bromide, and back extracted with dilute aqueous ammonia. Complete separation of selenium was accomplished by this procedure. Nitric acid in aqueous phase lowered the extraction efficiency, but 97% of efficiency was attained if it was below 0.3%. Gross recovery of (97.2±1.2)% was found by radioactive tracer technique. This method was applied to determination of selenium in Standard Reference Materials, Bovine Liver and W-1, and the values (1.20±1.2)ppm and 0.16ppm were obtained, respectively, while their published values were (1.1±0.1)ppm for Bovine Liver and 0.11 ppm for W-1. This method of separation can be applied to neutron activation analysis of selenium in various environmental samples.