Authors:Tassiane Matsubara, Mitiko Saiki, and Guilherme Zahn
In recent years, environmental concerns regarding antimony have grown considerably due to anthropogenic processes that have
resulted in increasing concentration of Sb in the environment, and also because of its impacts and possible adverse effects
to living organisms. Several techniques have been used, to obtain reliable results for Sb, since Sb is present at low level
concentration, requiring analytical instrumentation with low detection limits. The neutron activation analysis (NAA) technique
has a high metrological level for the determination of several elements in different matrices. However, Sb determination in
environmental and biological samples presents some analytical difficulties due to its low concentrations and gamma ray spectrum
interferences. The objective of this research was to study on Sb determination in environmental reference materials by NAA.
Ten environmental reference materials were selected and analyzed using long period irradiation at IEA-R1 research nuclear
reactor. The induced gamma activities of 122Sb and 124Sb were measured. Relative errors of the results demonstrated that the accuracy depends mainly on Sb radioisotope measured,
the decay time for counting and the sample composition.
Authors:Tassiane Matsubara, Márcio Bacchi, and Elisabete De Nadai Fernandes
Phosphorus is an essential element for plants and animals, playing a fundamental role in the production of biochemical energy.
Despite its relevance, phosphorus is not commonly determined by instrumental neutron activation analysis (INAA), because 32P does not emit gamma-rays in its decay. There are alternative methods for the determination of phosphorus by INAA, such as
the use of beta counting or the measurement of bremsstrahlung originated from the high energy beta particle from 32P. Here the determination of phosphorus in plant materials by measuring the bremsstrahlung production was further investigated, to optimize an analytical protocol for minimizing interferences and overcoming the poor
specificity. Eight certified reference materials of plant matrices with phosphorus ranging between 171 and 5,180 mg kg−1 were irradiated at a thermal neutron flux of 9.5 × 1012 cm−2 s−1 and measured with a HPGe detector at decay times varying from 7 to 60 days. Phosphorus solutions added to a certified reference
material at three levels were used for calibration. Counts accumulated in the baseline at four different regions of the gamma-ray
spectra were tested for the determination of phosphorus, with better results for the 100 keV region. The Compton scattering
contribution in the selected range was discounted using an experimental peak-to-Compton factor and the net areas of all peaks
in the spectra with energies higher than 218 keV, i.e. Compton edge above 100 keV. Amongst the interferences investigated,
the production of 32P from sulfur, and the contribution of Compton scattering should be considered for producing good results.