Narrow Results

Micro-PIXE and inductively coupled plasma mass spectrometry (ICP-MS) were applied to elemental distribution analyses in plant root apex which is composed of various types of tissues and cells in different developmental stages. ICP-MS was so sensitive that a large number of elements including Na, Mg, P, S, K, Ca, Mn, Fe, Cu, Zn, Se, Rb, Sr and Cs could be determined quantitatively. These fourteen elements included almost all the essential elements for plant growth. Only a rough estimation, however, could be obtained by ICP-MS for the elemental distribution at the tissue level, by analyzing sections from the root apex. On the other hand, micro-PIXE was effective for detailed mappings of elemental distributions. The images of elemental distributions were obtained for Na, Mg, P, S, K, Ca, Mn, Fe and Zn, corresponding to the microscopic images of the root structures. The localizations of P, K and Zn in some tissues were observed by the mappings. These results indicated that micro-PIXE and ICP-MS have different, but complementary abilities for the investigation of elemental distributions in plant tissues.

In order to evaluate the quantitative values of atmospheric aerosol samples collected on filters, we investigated the effects of filter collection conditions (non-uniformity of collected particles) on analytical values and compared the quantitative values by means of PIXE and ICP-MS, using as the analytical sample PM_2.5 collected on filters in a monitoring survey of atmospheric fine aerosol over the Kanto area of Japan in summer 2013. The results were as follows: (i) With respect to the uniformity of filter collection, differences in concentrations were seen for S and Cl as well as elements thought to originate in soil (Al, Si, Ti and Fe) depending on the analysis point, suggesting that collection of sulfate particles, chloride particles, and soil particles on filters was not uniform. (ii) According to a comparison of quantitative values yielded by PIXE and ICP-MS, ICP-MS values were lower than PIXE values for Mg, Al, Si, Ti and Fe, with Mg and Si being markedly lower. On the other hand, ICP-MS values were higher than PIXE values for Na, K, Ca and Zn. (iii) According to the results of measurement of NIST reference material and PM_2.5 samples by means of PIXE and ICP-MS, Mg, Al, Si, Ca, Ti, Fe and Zn showed the same tendency. However, Na and K were opposite.

Rare events search experiments, like those dedicated to the direct evidence of dark matter or neutrinoless double beta decay, are among the most exciting challenges of modern physics. The sensitivity of such experiments is driven by the background, which depends substantially on the radiopurity of the materials used for the experimental apparatus. Cutting edge measurement techniques are needed for a fast, sensitive and efficient screening of these materials and the certification of their production. Trace element measurements of high sensitivity and quick execution are mandatory also in other fields like tracing the geographical origin of food, temporal and geographical assignment of cultural heritage or monitoring environmental radioactivity. This work is an overview of the inorganic mass spectrometry facility available at Gran Sasso National Laboratory (LNGS) for radiopure material screening and is especially focused on its ICP-MS instrumentation. Analytical methods developed to achieve lowest detection limits in different types of matrix, like metals, polymers, crystals and composite materials, are also indicated. Detection limits of $10^{-18}{\mathrm{\text{gg}}}^{-1}$ for ${}^{226}\mathrm{\text{Ra}}$, $10^{-14}{\mathrm{\text{gg}}}^{-1}$ for U and Th and $10^{-12}{\mathrm{\text{gg}}}^{-1}$ for K are attained through dedicated operation conditions of the instrumentation. Details are given on the results obtained for different experiments ongoing or under construction at LNGS.

A sol-enhanced gold (Au) — nickel (Ni) — titanium dioxide (TiO₂) composite coating technique has been developed at the University of Auckland. The aim of the present study is to achieve quality control and thickness homogeneity of the coatings in order to scale up this process to the workshop level. Multi-coating samples were prepared in the same electroplating unit with same processing parameters. The thickness variation and influence of titanium dioxide (TiO₂) sol content on the thickness have been studied. The consumption of Au and Ti ions in the electrolytes during the electroplating process was measured by inductively coupled plasma-mass spectrometry (ICP–MS) method. The cross-section microstructures of coatings were studied by field emission scanning electron microscope (FESEM) with an energy dispersive spectroscopy (EDS) system. An optimized processing method has been put forward for the industry process to produce coatings with uniform thickness and good quality.

The toxicological effect of TiO₂ nanoparticles with different crystal structure (80 nm for rutile and 155 nm for anatase) on female mice was investigated through intranasal instillation. After exposure for 30 days at the dose of 50 mg/kg body weight, no abnormal activity and mortality were observed with the normally increasing body weight of mice. The coefficients of tissues to body weight also show no obvious difference from the control except the increased coefficient of kidneys in mice exposed to 80 nm TiO₂ nanoparticles. Titanium contents and histopathology examination indicate the no pathological response in the lung was induced by the increased TiO₂ deposition, and the liver, heart, and spleen were not influenced. The severe pathology changes in kidneys suggest that TiO₂ nanoparticles may be excreted out by kidneys via system circulation. However, the serum biochemical parameters were not changed compared with the control, which means no obvious functional impairment induced by the nasal exposure for 30 days. In addition, the higher titanium contents in the brain tissues imply that the translocation and deposition of nanoparticles through intranasal instilling pathway is different from the other routes such as intratracheal inhalation or intratracheal instillation. The influence of deposited nanoparticles on central nervous system needs further investigation and is underway.