Trace determination of nickel (and cobalt) in biological reference materials by radiochemical neutron activation analysis

Abstract

Very few biological reference materials are certified for nickel below 1 mg · kg−1. Neutron activation analysis was only rarely considered as a possible approach; reported sensitivities were usually not very good, unless preconcentration was applied. In the present work, the relatively high fast neutron flux of our TRIGA reactor was used to induce the 58Ni(n, p)58Co reaction, and 58Co (E γ=811 keV) was radiochemically separated from other radionuclides by classical anion-exchange chromatography in hydrochloric acid. 57Co was added to the irradiated sample before decomposition as a radioisotopic yield monitor. By concentrating the final sample fraction and measurement in a well-type HP Ge detector, Ni concentrations down to the 10-μg · kg−1 level could be determined for samples irradiated for 1 day. 60Co, produced by neutron capture on 59Co, is also coseparated and quantified from the gamma spectrum, so that both elements Ni and Co are determined. Results are reported for a series of NBS and other biological reference materials in the concentration range 10 μg-10 mg · kg−1. Possibilities for further increases in sensitivity are discussed.