Selenium and mercury determination in biological samples using gamma-gamma coincidence and Compton suppression

Biological materials containing trace amounts of mercury and selenium were examined using neutron activation analysis. They were analyzed using Compton suppression and γ-γ coincidence counting. The 279 keV photopeak of activated mercury (203Hg) was analyzed in order to observe the mercury content in these samples. Selenium, an element found in many biological samples, interferes with the analysis of 203Hg when activated (75Se). Because the selenium interference comes from a cascading emission, Compton suppression was utilized to reduce this interference. In order to fully characterize the selenium content in the samples, γ-γ coincidence was used which reduced the background and eliminated bremsstrahlung interference produced from neutron activated phosphorous through the 31P(n, γ)32P reaction which is a pure beta emitter. As a result, we determined the mercury and selenium concentrations in three standard reference materials, which contain varying ratios of mercury to selenium concentrations. This study also showed that these types of concentrations can be determined from small (<500 mg) sample masses. Further work needs to be done on wet samples that require dehydration, as mercury can be lost through this process. (author)