Narrow Results

By building up a cryo-preparation laboratory a method was developed which allows us to prepare cryo sections of fully differentiated plant-root material, according to the requirements of the proton microprobe. Since cryo-preparation is the only possible method delivering reliable elemental distributions, this step was a fundamental for all our further investigations in plant root physiology. As an example, PIXE-investigations of a root section of a heavy metal hyper-accumulating plant Brassica juncea L. will be presented.

Elemental distributions in a post oak leaf was measured using the Particle-Induced X-ray Emission (PIXE) technique and a proton microbeam at energy of 3 MeV with spatial resolution of 10 μm. The elements detected in this sample were Mg, Al, Si, P, S, Cl, K, Ca, Cr, Mn, Fe, Cu, Zn, Br, Rb, and Sr. Among them, spatial differences in the distribution of nine elements were observed between the vascular and mesophyll tissue. Si, Cl, K, and Ca were mostly accumulated in vascular tissue, while Mg, P, S, Cr, and Mn were for the most part accumulated in the mesophyll. The distribution of Ca appeared to follow cell wall contours. The distribution of some of these elements is compared to the function of the elements in living tissue and future possibilities for this type of investigation are discussed.

Micro-PIXE has been used to measure the trace element distribution in otoliths from several species of ocean fish, in order to investigate its possible use in stock discrimination. Trace elements detected include Sr, Fe, Mn, Ni, Zn, Cu, Se, Cd, Br, Hg and Pb. Trace elements Na, K, Cl, S and Cl were detected with the electron microprobe. The high sensitivity of PIXE demands a meticulous sample preparation procedure to avoid contamination problems. Practical problems associated with the application of the technique were investigated in detail. Preliminary results indicate that most trace elements except Sr, are present at close to the limits of detection at few ppm, but biologically significant data can be obtained for stock discrimination applications.

A method of quantitative analysis of bone samples by simultaneous measurements of proton induced X-ray emission (PIXE) and Rutherford backscattered (RBS) spectra is described. The method is used for the evaluation of the data collected during proton microprobe irradiation. The RBS spectra are used for the determination of the sample thickness. The sample matrix is regarded as a mixture of collagen and hydroxyapatite. The unknown proportion of both compounds at each irradiated point is adjusted until the Ca concentration determined by PIXE is in accordance with the value calculated on the basis of the assumed matrix composition. For quantitative analysis, the calculation of the absolute yield using the thick target PIXE formula was applied. The sources and ranges of systematic errors are discussed.

Concentrations of chemical elements in different organs of healthy, of tumor (rhabdomyosarcoma R1H) bearing and of cis-diamminodichloroplatinum (cisDDP) treated rats were analyzed with a 2 MeV proton microprobe. Characteristic concentrations were found in spleen, liver, kidney, muscle and tumor. Bromine concentrations were elevated after three weeks of tumor growth. As a result of cisDDP application, they dropped considerably. These alterations were found not only in tumor tissue but also in organs not directly involved in tumor growth (e.g. liver and spleen). Platinum as a marker for the drug could be detected in all tissues except muscle. The highest concentrations were found in the kidney. With the scanning microprobe, elemental maps in several tissues were investigated. These could be correlated to histological details (e.g. in spleen and tumor).

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.