International Journal of PIXE

Concerning the PIXE analysis of Cr(VI) in water using ion-exchange filters, the limit of detection (LOD) and the influence of matrix anions were investigated. In order to look for the experimental condition for obtaining the minimum LOD, we measured the Cr-Kα X-ray counts and background counts under the Kα X-ray peak as a function of the incident proton energy and the thickness of the Mylar absorber foil in front of the detector. To investigate the interference by coexisting anions, each of PO₄^3-, SO₄^2-, NO₃^-, Cl^-, and F^- ions and Cr(VI) ions were mixed in aqueous solutions and adsorbed on DE81-DEAE cellulose paper, a weakly basic anion exchanger with diethylaminoethyl functional groups. Then the filter samples were measured by PIXE using 2.5 MeV proton beams. We obtained a LOD of 0.16 µg or 8 ppb for 20 mL samples at a proton energy of 2.5 MeV and a Mylar film thickness of 50 or 100 µm. The experimental results on the mixed solutions indicated that NO₃^-, Cl^-, and F^- as coexisting ions didn't interfere significantly with determination of a 50 µg/L Cr(VI) concentration for 40 mL total solution volume, despite the total amount of anions was about 90% of ion exchange capacity of a filter. On the other hand, slight interferences by PO₄^3- ions were observed. However, under the same condition, we found that if the total amount of SO₄^2- ions was higher than 20% of ion exchange capacity, they induced significant interferences in determining Cr(VI).

Chemical state changes of phosphorus induced by proton irradiation were measured by a high-resolution wavelength-dispersive (WD) PIXE system. Six standard samples of phosphorus with different chemical states (Ca(H₂PO₄)₂•H₂O (P⁵⁺), CaHPO₄•2H₂O (P⁵⁺), NaH₂PO₄ (P⁵⁺), CaHPO₃•H₂O (P³⁺), Ca(H₂PO₂)₂ (P¹⁺), and NaH₂PO₂•H₂O (P¹⁺)) were prepared for the measurements. The P-Kα₁ peak energy for the sample of P³⁺ increased after the irradiation. The peak energy of the P³⁺ sample became nearly same as that of P⁵⁺ after irradiation with more than 2 ×10⁷Gy. This result indicates that P³⁺ in the sample has changed to P⁵⁺ due to proton irradiation. On the other hand, the P-Kα X-ray spectra for the samples of P⁵⁺ didn't show any interesting changes even for much higher proton dose (3.4 × 10⁸Gy). Also, P-Kα peaks which correspond to chemical states (P⁵⁺ and P^3-) other than original state were observed for the sample of P¹⁺ in the region of more than 10⁷Gy.

We established and reported two years ago the original methods for evaluating daily changes of elemental concentration in a body by means of a standard-free method for powdered beard samples daily taken with electric shaver. It was found that the method is quite useful for investigating short- and long-term changes of elemental concentration in a body. However, the method for beard analysis is applicable only to men. In order to estimate daily changes of elemental concentration in a body for women and children, a new method which allows us to quantitatively analyze hair samples cut into 1 mm pieces has been developed and applied to three long hair samples taken from three persons. It is found that the method enables us to estimate both long- and short-term changes in elemental concentration in a body as well as beard analysis. It is found that sulfur keeps almost constant over a long period, and arsenic shows very rapid changes with a few days' period, while mercury shows only long-term changes with the period of a few months. These behaviors are almost the same as those observed in beard analyses. On the other hand, bromine shows a certain seasonal changes; its concentration shows a certain trend of increasing in summer and decreasing in winter. Lead and calcium show very long-term changes, and the behavior of strontium is quite similar to that of calcium. The method is expected to give us information about history of changes in elemental concentration in a human body over a few or more years. It is expected that the behavior of arsenic showing rapid elevation within a few days can be explained as a response to intakes of arsenic-rich foods. It is expected that the method gives us a clue to the identification of the main pathways of human exposure to certain toxic elements.

Particulate matter (PM) such as chromium compound (PbCrO₄) is highly cytotoxic and carcinogenic. Several hexavalent chromium, compounds, Cr (VI), compounds are known to generate hydroxyl radical with in the cell and contribute to tissue damage. The way that theses compounds interact with human bodies at a cellular level is still unknown. To investigate the intracellular mechanism of chromium compounds, the 3D imaging techniques at the micro level are needed. In this paper, we report on the improvement of the PIXE-µ-CT system which was developed at Tohoku University and measured intracellular distribution images of PbCrO_4.particles on human lung cell.

Synchrotron radiation X-ray fluorescence (SR-XRF) using high energy incident X-rays was combined with micro-PIXE to analyze the renal distribution of Rb and essential elements in immature rats. The Rb concentrations in the kidneys of newborn (1 week old) and young (3 weeks old) rats were 4.19 ± 0.71 and 4.13 ± 0.30 µg/g, respectively, similar to those of adult rats. Rubidium as well as Zn was detected more in the cortex than the medulla, while Fe was concentrated in the outermost areas of the medulla of newborn rats. The renal structures of young rats achieved adult zonation into the cortex, the outer medulla and the inner medulla. Rubidium was high in the outer stripe of the outer medulla. Further analysis at higher resolution revealed Rb in the proximal tubules in the innermost part of the cortex. These results indicated that Rb was distributed downstream of the proximal tubules. This profile was similar to that of potassium, an Rb congener.

This study was undertaken to elucidate physiological properties of fucoidan extracted from Cladosiphon okamuranus TOKITA (C. okamuranus) and Fucus vesiculosus (F.vesilurosus). According to the data on MTT assay and TUNEL staining, F. vesiculosus possessed more anti-proliferate activity than C. okamuranus through apoptosis induction. We determined the metal contents of fucoidan to evaluate the relevance of metal elements in its biological effects. Al, Fe and Zn levels were significantly increased in F. vesiculosus than in C. okamuranus. The intracellular changes of metal elements following the administration of fucoidan was analyzed by in-air micro-PIXE in TRL1215 cells (normal rat liver cell line). At 24 h after 5-bromo-2'-deoxyuridine (BrdU) dosing, TRL1215 cells were treated with 1.0 mg/mL of each fucoidan for 9 h. The X-ray spectra showed that F. vesiculosus-treated cells markedly increased the yield of aluminum (Al) compared to those of C. okamuranus -treated cells and the control. In F. vesiculosus -treated cells, the focal accumulation of Br was spatially correlated with Al map, suggesting that Al was localized within the nucleus. These findings suggest that F. vesiculosus fucoidan increases the accumulations of Al in rat hepatocytes, which may participate in anti-proliferate activity of this fucoidan.

Beech (Fagus crenata) leaves were collected at three sites in and near the Shirakami-Sanchi World Heritage Area (a mountainous region) during the plant growing season of year 1999. The composition and concentration of the elements were determined by the method of Particle Induced X-ray Emission (PIXE). Thirty one elements were determined in total. Na, Mg, Si, P, S, Cl, K, Ca, Mn and Fe were found to be the most important elements in all sites. The concentrations of Na, Si and Cl in leaves were found to be increased with the growth of leaves, while those of P, S and K were to be decreased. The concentrations of other major elements did not change with respect to leaf phenology. Those analysis of the elements in the beech leaves suggested that 1) Na, Si and Cl are the key elements for judging the air pollution phenomenon, 2) P, S, K, Ca, Mn, Fe, Cu, Zn and Rb may play an important role for the metabolism of plants.

Wall thinning of piping made of carbon steel in nuclear and thermal power plants affects their life time and safety. Wall thinning results from dissolution of the oxide layer formed on the surface. To get a better understanding of this mechanism, characterization of oxide layer in localized area should be examined. We applied the simultaneous micro-PIXE/RBS analysis to characterization of the oxide layer in localized area. The oxide layer formed under the dynamic condition is not uniform over the 20 × 20 µm² area. In this case, it is difficult to characterize layer by conventional RBS analysis. The simultaneous micro-PIXE/RBS system could characterize the layer by region analysis. Micro-PIXE analysis was applicable for segmentation of the specific area Then, RBS spectra was extracted from the area and the layer for the corresponding area was characterized. By combining micro-PIXE and micro-RBS, characterization of oxide layer could be done so as to get a better understanding of the corrosion mechanism effectively.

This paper deals with studies on Ge K_α and K_β escape peaks in particle induced X-ray emission (PIXE) spectra recorded by a high purity germanium (HPGe) detector. A knowledge of the energies and intensities of these escape peaks is desirable for accurate qualitative as well as quantitative analysis of elements by PIXE. The spectral interferences caused by Ge K escape peaks in the determination of Fe in U by PIXE are highlighted for illustration. A simple theoretical approach based on the production of Ge K X-rays inside the Ge crystal of the detector during the process of detection of the incident characteristic X-rays and the subsequent escape of a fraction of the produced radiations from the crystal, is described to calculate the intensity ratio of the Ge escape peak to its parent characteristic X-rays. The calculated values are in agreement with the experimental values and those estimated using the formulation provided in GUPIX software for PIXE. The Ge K escape peaks are very prominent; the intensities of Ge K_α escape peaks, from bromine to silver, range from 15% to 6% of those of their respective K_α X-rays. These intensities are, in general, considerably higher compared to those of Si escape peaks in spectra recorded by Si(Li) detector. Ge K escape peaks therefore may give rise to severe interferences. The present approach provides a precise (~8%) determination of the intensity of an escape peak and thereby facilitates a reliable PIXE analysis.

Elemental concentrations in some herbal medical products, produced by different ayurvedic pharmacies in India, were determined using Energy Dispersive X-Ray Fluorescence Spectrometry (EDXRF). All the eight products, which were studied, contained mercury, and four out of the eight products contained arsenic in varied amounts. Daily mercury and arsenic intakes by the patients taking these products, determined from the doses prescribed by the manufacturers, exceeded the recommendations by WHO. The present work does not argue on the toxicity of heavy metals in drugs but gives information about the presence of heavy metals at levels more than the required recommendations by various health regulatory bodies. This level of As and Hg calls for caution as far as their safe intake is concerned.

Fluoride (F) distributions in a synthesized hydroxyl apatite (HAp) block of uniform structure and in teeth were measured using in-air micro-PIGE (particle induced gamma-ray emission) and micro-PIXE system, which was developed at the Japan Atomic Energy Agency (JAEA) in Takasaki. We used a nuclear reaction ¹⁹F(p,αγ)¹⁶O to measure F density. The characteristic important feature of this technique is that it can measure F quantitatively in a microscopic area of the specimen placed in air. A surface of the HAp, the enamel buccal surface of a human molar, and a class V cavity wall in dentin were applied a sodium fluoride solution (NaF) four times and immersed in a normal saline solution. After one month, specimens were cut longitudinally. The F distributions were measured from the surface toward the inner part of the cut surface. The F penetration into specimens following NaF application was quantitatively configured in a two-dimensional mapping form. This method is quite useful for characterizing F distribution in a microscopic area of a tooth.

The segregation and disposal of chromated copper arsenate (CCA)-treated wood waste when recycling building waste materials is a serious issue. We examined the contents of CCA preserved cedar timber by PIXE analysis. CCA preserved timber contained large amounts of these metals both on the surface and core of the wood. The ratio of chromium, copper and arsenic contained on the surface was 1:2:1, and in contrast, the ratio in the core was 1:1:2. In other words, the arsenic content was highest in the core. Moreover, the chemical form of arsenic in both parts of the wood was only inorganic arsenic; the same form of arsenic in preservative components known as carcinogenic substances. These findings mean that the complete separation of waste CCA preserved timber from construction and demolition wood is needed.