Masafumi Ishikawa

X-ray microanalysis with energy tunable synchrotron X-rays

Abstract Focused intense monochromatic synchrotron radiation was realized with a combination of a Pt coated ellipsoidal mirror, a double crystal monochromator and a pinhole. Energy tunable X-ray microanalysis using a focused X-ray beam was compared to particle induced X-ray emission analysis. A section of Japanese cedar showed severe damage after proton irradiation, while another section of the tree showed no damage after the measurement of its trace element distribution by synchrotron radiation. Less damage, high sensitivity and energy tunability were demonstrated by utilizing synchrotron radiation.

Application of PIXE analysis to environmental samples stable element distribution in sea algae by scanning microprobe analysis

The resolution of a 33±3 μm microprobe focussed with quadrupole doublet installed at the 3 MV Van de Graaff of the National Institute of Radiological Sciences was used for this analysis. Brown algae, Hijiki,Hizikia fusiforme was the sample target bombarded with a 2 MeV proton beam collimated mechanically into a rectangular image of 100 μm × 700 μm. Scanning across the sample target prepared into a longitudinal section from the caulis of the algae provided the following observations. More than 12 elements such as Al, Si, P, Cl, Ca, Mn, Fe, Cu, Zn, As, Br and Sr were determined simultaneously, together with their distributional information across the diameter. In the medullary layer, Mn and Zn were specific in their accumulation, while the deposition of Fe, Cu, As and Br were observed to be high in the epithelial layer, especially Fe and Cu which were found on the surface, where they contact ambient sea water, but no significant change in pattern was indicated for such elements as Al, P and Cl. The PIXE microprobe analysis was, therefore, effective in its detectability for elements below a few ppm level, resultantly provides further possibilities for collecting information from bio-medical and environmental samples on trace characterization of elements.

A proton microprobe scanning across the vertebra of a flat fish,Paralichthys olivaceus.

Elemental distributions across the vertebra of a flat fish were determined by a 100×300 μm proton scanning microprobe. By normalizing with proton currents, 22 elements demonstrated characteristic patterns in locality; Si, Ca, Cr, Ga, Sr, and I were homogeneous across the vertebral centrum, whereas concentrations of P, Ti, V, Co, Ni, Cu, Hg, Se, and Br were increasingly higher toward the inside of the centrum. Opposite results were obtained for S and Cl, and especially Fe, which showed gradually lower concentrations toward the center. The K, Mn, and Zn were higher in concentration at both edges, showing a minimum value at the middle of the vertebra centrum, where Pb was at a maximum in its distribution. The fact that such a thin intervertebrale membrane contains relatively large amounts of Cl, K, Ca, Fe, Zn, Pb, Br, and I is interesting.

Elemental Distribution on the Growth Front of Oyster Shell Measured by Synchrotron Monochromatized X-rays

Elemental analyses on the growth front of the paper shell obtained from a chambered oyster, Crassostrea gigas, were carried out using the newly developed synchrotron radiation X-ray fluorescence analysis. This paper discusses the possibility of using the synchrotron monochromatized X-ray scanning microbeam to analyze mineralized samples. The newly formed paper shells were analyzed two dimensionally with an x-z scanner. The number of scanning spots was approximately 3000 to 4000. The distribution maps of Ca, Fe, Zn and Sr were obtained. Ca distribution corresponded well with that of membrane-like shell materials and its pattern was similar to that for Sr. Fe and Zn did not represent any characteristic elemental locality in the sample without jelly-like materials except for a rather high accumulation at some small areas. Particular interest is given to Zn, which was similar to the distribution patterns of Ca and Sr in the sample with jelly-like materials. This analytical system is very promising in the field of biomineralization.

Application of proton induced X-ray emission to the qualitative and quantitative analysis of iodine in biological samples

Particle-induced X-ray emission (PIXE) was applied to evaluate the loss of volatile elements such as iodine in biological samples. The analytical quality of the method is comparable or better than spectrophotometry, which is currently believed to be the most reliable for iodine determination. The temperature dependence of volatility loss of trace iodine was characteristic, and the feature was divided into three temperature regions. The first one, ranging from room temperature to 200 °C, showed only a slight loss below 20% on drying; the second stage, between 200 °C and 350 °C, where carbonizing processes became prominent, showed a remarkable loss up to 50%; the last one, beyond 350 °C, was accompanied by a considerable loss of iodine (more than 80%) with ashing. Even in the analysis using low temperature ashing with oxygen plasma, the loss of iodine observed was considerable (nearly 80%). The significance of these findings by PIXE in trace analysis is noted to improve analytical quality of volatile elements, such as iodine in biological, medical and also environmental fields.

PIXE as a tool for environmental and bio-medical analysis

Abstract The advantages of PIXE are discussed in elucidating certain problems which remain unsolved in environmental and bio-medical fields. The focus of this study centers on PIXEs characteristic ability to detect elements even in extreme compositions in a matrix. A Ca-rich shell containing more than 10 elements was successfully analyzed. No specific affinity could be substantiated for the elements with hard protein Conchiolin. Despite considerable Na, micro-constituents in salt were also adequately determined. Many elements were found in the salt processed through evaporation in the salt work; the Fe content in sea water was determined. Values of 86 and 81 ppb were obtained for natural and filtered sea water, respectively. The reliability was examined by comparison with results from AAS. The information obtained suggests the effectiveness of PIXE over the methods currently available.

Annual variation of stable iodine in brown sea algae (hijiki, Hizikia fusiforme)

Abstract The amount of radioecologically significant iodine in sea algae was determined during the period from June 1982 to May 1983, applying the PIXE method. Parallel analyses were carried out on aliquot samples by two PIXE systems one at Tohoku University and one at NIRS. The results of the two systems for the corresponding samples were reasonably analogous. The annual mean value was 190 ppm in dry matter. The pattern suggested that the content of stable iodine changed periodically, showing three maxima: in September, March and May. The highest value was found in March (430 ppm in dry matter), whereas the lowest was found in December (95 ppm), the variation factor being nearly 4.5 in magnitude. This variation was not caused by the change of tide and currents in the environment nor by the physiological activities of the algae under natural conditions, but rather by the effect of harvestings for commercial foods. This detailed information on stable iodine can possibly provide the amount of its radioisotopes. which, as is currently expected in the field of radioecology, is necessary for a more precise evaluation of radiation doses.

Pixe scanning analysis across the scale of a sea-bass, la teolabrax japonicus

Abstract Trace characterization in the scale of a sea-bass, Lateolabrax japonicus was performed. A rectangular proton beam of 600 × 2000 μm 2 (height × width), accelerated to 2.5 MeV, was applied to the scanning analysis, using the 3.0 MV Van de Graaff of the National Institute of Radiological Sciences. The total scanning distance was 3800 μm, covered by ten steps from the edge towards the focus of the scale. This distance covered three annuluses. The elements P, S, Ca, Mn, Fe, Cu, Zn, Sr and Mo were observed in the spectrum. Elemental concentrations were increasingly higher towards the focus. Mn was observed only at a single position. This position also represented specific accumulations for all other elements, except Fe and Zn. The observed ratio of Sr/Ca was calculated to be 4.6, which was considerably higher than the reported value of 0.2. No specific accumulation was found on the three annuluses, although elemental depositions were expected on these positions.