International Journal of PIXE

Soybean is one of the major crops in the world as a source of protein. Spatial distribution of elements in bean sprout, soybean seedling, was determined by Particle Induced X-ray Emission (PIXE) analysis to investigate their transfer in the growth. Soybeans were germinated in a dark box at 25~26ºC using pure water without any mineral supplement. After 20hr, 40hr, 65hr and 137hr, the seedlings were harvested and each sprout was separated into cotyledons, hypocotyls, leaves and root. Each part of bean sprout was freeze-dried and applied to PIXE analysis. It was observed that K, Mn, Fe, Cu and Zn moved from the cotyledons and the primary root to the hypocotyls and the 1st leaf, while Ca in the seed hardly moved to other part.

Trace elements in five kinds of flour which were made in Japan. America and Canada, have been measured by means of in-air PIXE. Twelve kinds of trace elements were detected, such as Cl, K, Ca, Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn and Br. The concentration of these elements varied depending on the place where they were made. In order to check the target preparation procedure, two types of sample preparation have been used, such as wet ashing by nitric acid in a microwave oven and making a paste by an internal standard solution. Comparisons of the results of both samples ensures that bromine was not lost during micro-wave oven heating. Analytic fitting of PIXE spectra by a personal computer and a commercial apllication software was successfully used.

The quantitative changes of elements in blood plasma were observed with the passage of time after X-ray whole body irradiation with 12 Gy on C57BL/6J mice by PIXE method. From 4 days after irradiation, dead mouse was found and all mice died by 8 days. Hematocrit (Ht) values indicated a decrease from the 1st day, but on days 3 and 4 there was a small rise. Finally the values became 64 % of that of non-irradiated control on day 7, it was just before death. By analysis with PIXE method, 15 elements were observable in blood plasma of control mice. The elements such as P, S, Cl, K, Ca and Cr were abundant and Fe and Br followed. As trace elements, the peaks of Zn, Cu and Ni were clearly observed. After irradiation, K and Ca decreased on day 1st, afterwards increased gradually. On the contrary, the elements, S, Cl, were rather stable. While Fe decreased from 1st day, Cu increased from the day 2. Zn and Ni showed intensely down and rise in amount, and decreased on day 7. The results of possible measurement of the changes in amount of these elements of blood plasma suggest PIXE method is an easy and useful way for diagnosis.

We have examined tin-polymetallic ore, a complex mixture of cassiterite (SnO₂) and sulfides, by micro-PIXE. Tin-polymetallic ore is one of the major sources of technologically important “rare metals”, especially of indium and bismuth, usually as trace elements. In addition to such rare metals, silver is another important trace component in the ore. But the trace elemental distribution of tin-polymetallic deposit has not well been described due to the small size of constituent minerals, complex ore texture, and lack of analytical method to detect trace elements in a small area. PIXE with a proton microbeam could be an effective tool to solve this problem by delineating the distribution of these trace elements among carrier minerals with the required sensitivity. Thus we have applied PIXE with the CSIRO’s proton microprobe to a tin-polymetallic ore from Canada. The result showed that micro-PIXE is an essential tool to study trace element distribution in such a complex ore.

A paste spreading method for target preparation of biological materials for PIXE analysis by proton beams from a small cyclotron is developed. Quantitative results obtained for NIST Bovine Liver (SRM 1577b) are consistent with values certified by NIST for almost all elements heavier than Mg except for Ca and Rb. Concentrations of Cl and Br, which are volatile under acidic condition, can also be reasonably determined. Effect of wet ashing on determination of Se is examined, then recovery of Se, which means a ratio of determined value divided by that of Se added to NIST Bovine Liver, falls to less than 50% because of vaporization during drying, and especially decreases to 22% when the targets were dried by lyophilization. On the other hand, the recovery for targets prepared by the paste spreading method reaches about 100%. As an example of target preparation for a real sample material by the paste spreading method, elemental concentrations in the liver of Long-Evans Cinnamon (LEC) rats, where Cu spontaneously accumulates, and of Sprague-Dawley (SD) rats as a control are determined. Among 12 elements determined, the concentrations of hepatic S, Fe, Cu, Zn, and Se of LEC rats are significantly higher than those of SD rats (P<0.01).

The micro-analytical technique has made remarkable progress during the last two to three decades. A Particle Induced X-ray Emission(PIXE) is one of the most powerful analytical method. The analysis of atmospheric aerosol is one of the most preferable fields of the PIXE analysis. Applying the PIXE analysis, we have investigated the characteristics of atmospheric aerosols under the various environmental and meteorological conditions. The atmospheric aerosols were continuously sampled every 12 hours for one year from October 1992 to October 1993. The concentrations of gravimetric mass and 15 elements were determined by a microbalance method and the PXIE analysis.respectively.

The seasonal change of mass concentration of atmospheric aerosols has commonly two peaks in spring and early winter. The peak in spring is mainly caused by the Kosa dust. The most dominant element was Si and S the coarse and fine particles,respectively. Daily change of elemental concentrations differed according to the origin of each element and the scavenging effect of atmospheric aerosols by rain drops was clearly observed in the time variation of aerosol concentration.

Four ancient Chinese ink sticks were analyzed by PIXE. One sample is estimated to belong to the Ming Dynasty period(1368–1644). Three others including a red one belong to the Ching Dynasty period(1646–1912). Trace elements such as Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, Br, Sr, Pb were detected from black Chinese ink sticks. From red one, Si, S, Cl, Ca. Cr, Fe, Cu, Sr, Mo, Ba, Hg, Pb were detected. These trace elements show the materials or making processes of those sticks and every specimen has its own characteristics. At the same time, some pieces of Japanese paper and those stained with Chinese ink had been analyzed. These results show that the characteristics of ink upon paper can be determined by PIXE.

The material composition and surface structure of dental and orthopaedic implants have important effects on integration of the implants with the surrounding bone, and at the same time, the release of the constituent elements of the implants into the surrounding tissues. It is the aim of this paper to study the degree of release of Ti in relation to the surface roughness of the implants. For this purpose, screw shaped implants were prepared with two different surface topographies; one group was left as-machined, i.e. as machine-turned surface, and the second group was blasted with 25 µm Al₂O₃ particles. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using height and spatial descriptive parameters. The as-machined surfaces had an average surface roughness (S_a) of 0.96 µm and the blasted surfaces had an S_a value of 1.16 µm. The implants were inserted into rabbit bone for 1 year. Six samples (three of each type) were prepared for PIXE analysis. The PIXE analysis was done using proton beams from a tandem type accelerator. with an energy of 2 MeV. The results show that at distances of about 2 mm from implant surface, titanium release into hard tissues was found at similar amounts for the as-machined and the blasted implants inserted in the tibia.

Fish otoliths are continuously dsposited from fish birth to its death along with encoding environmental information. In order to decode the information, PIXE was adopted as trace elemental analysis of the otoliths. Strontium to calcium concentration ratios of red sea bream otoliths varied among rearing stations. The Sr/Ca ratios of Lake Biwa catfishes also varied between male and female and among fishing grounds. The PIXE analysis was applied to the fish stock discrimination.

Micro trace elements in the squid statolith, a calcareous stone which acts as a balancer and hearing, was analyzed with Particle Induced X-ray Emission (PIXE) for the Japanese common squid for the first time. Calcium is the main component of the squid statoliths, which means that squid statolith is the pure calcified structure similar to the fish otolith. Beside Ca, Sr was detected with strong dosage, and some other elements as Mn, Fe, Cu, Zn and As were also detected. Possible assumption of intake of microelemts to the statoliths and the suitability of PIXE for statoliths analysis are discussed.

Newly installed vertical-beam in-air PIXE system at CYRIC (Cyclotron and Radioisotope Center, Tohoku University) and some results of experiments performed for a year were described. Three different types of samples: thick metal plate samples, living root-tips of a plant and solutions have been measured successfully in the system.

A semi-empirical approach of elemental response functions for linear associated neural network analysis is proposed. The proposed method is a combined one of both the pure experimental and model based ones: spectra of standard single elemental samples of selected elements are measured, and model parameters related to the analyzing system are deduced: elemental responses are calculated by a suitable peak shape model and corrected with respect to the efficiency: channel-wise response data are generated using the Monte-Carlo simulation: finally, the response data are adjusted to the corresponding experimental data for some multi-elemental standard samples. This method is tested except for the last adjustment process.

X-ray absorbers specialized for some samples, which contain vast amounts of certain elements, have been designed and tried. By means of these absorbers, x-ray spectra in which some distinguished x-ray peaks exist become fairly gentle-sloping over a wide x-ray energy range, and consequently, both sensitivity and efficiency of measurements are fairly improved. Furthermore, these absorbers enable us to analyze all elements simultaneously, to save measuring time and also to improve accuracy of analysis. Transmission curves of these absorbers are determined using techniques developed by us, and the accuracy has been confirmed by analyzing a few standard samples.

Quantitative analysis of powder sample, soil, ash and so on, which consists of rich heavy metal elements that are not decomposed easily with acid or alkali was attempted. Usually, powder sample was ground with an agate mortar, mixed with binding material cellulose and pelletized for quantitative PIXE analysis. However, the resulting pellet target is thick. Accordingly, when heavy elements are included in sample, it gives effect on PIXE spectrum. Namely, matrix effect arises on it. So firstly, a fixed quantity of molybdenum was added into sample and mixed as standard material in order to determine the concentration of the most typical element, iron included in sample. Then the mixed powder were pelletized and analyzed to determine the concentration of iron. Next, original powder sample was pushed on a backing film to make thin target, and the thin target was analyzed as internal standard of determined iron by ordinary PIXE analysis method. In the result, concentrations of major elements of powder sample were determined quantitatively.

High resolution L x-ray emission spectra of Fe and Cu have been measured by 0.75 MeV/u H and He, and 0.73 MeV/u He, Si and Ar ion impacts with a crystal spectrometer. The x-ray transition energies in the Fe and Cu targets for Lι, Lη, Lα_1,2, Lβ₁ and Lβ_3,4 diagram lines induced by light ion impacts are determined, which are in good agreement with those given in the reference. The difference in L x-ray emission spectra produced by H, He, Si and Ar ions is considered and the emission spectra for the Cu target are compared with the calculated ones based on the multiconfiguration Dirac-Fock method. The origin of the broadening of the Lα_1,2 line to the lower energy for Si and Ar ion impacts is attributed to one 2p plus one 3d electron vacancy production.