Radionuclide X-ray fluorescence analysi

Energy Dispersive X-Ray Fluorescence Anal3rsis Preconcentration of Trace Elements Radionuclide X-Ray Fluorescence Analysis Voltammetry... 

Harangozo M, Dejmkova E, Havranek E. 1985. The determination of trace elements in water by radionuclide x-ray fluorescence analysis. Acta facultatis Pharmaceuticae 39 113-140. 

Tolgyessy J, Havranek E and Dejmkova E (1990) Radionuclide X-ray fluorescence analysis, with environmental applications. In Svehla G, ed. Wilson and Wilson s Comprehensive analytical chemistry Vol 26, pp. 1—254. Elsevier, Amsterdam. 

Nuclear analytical methods, particularly activation analysis and radionuclide X-ray fluorescence analysis are frequently used in the analysis of atmospheric aerosols. 

Among other methods for determining trace and toxic elements in the soil, there are also electro-chemical analytical methods, mainly polarogra-phy and in the case of nuclear analytical methods, activation analysis and radionuclide X-ray fluorescence analysis are employed. Mass spectrometry, laser emission spectral microanalysis and other instrumental methods can also be used. 

Tolgyessy, J., Havranek, E. and Dejmkova, E. Radionuclide X-ray Fluorescence Analysis of Environmental Samples. Elsevier, Amsterdam 1990. 

The same equipment as for X-ray spectrometry is used for X-ray fluorescence analysis (XFA). In this method, emission of characteristic X rays is induced by excitation with X-ray sources (X-ray tubes or X-ray emitting radionuclides) or with charged particles (PIXE, i.e. particle-induced X-ray emission). 

The application of radionuclides as radiation sources in X-ray fluorescence analysis is illustrated in Fig.17.5. The X rays or y rays emitted by a radionuclide are absorbed in the sample and the X rays emitted by the sample are measured by means of a semiconductor in combination with a multichannel analyser. Quantitative evaluation of the spectra is possible by use of suitable standards. In comparison with excitation by means of X-ray tubes, the main advantages of radionuclides are... 

Figure 17.5. Set-up for X-ray fluorescence analysis with radionuclide excitation.

Table 17.6. Radionuclides suitable as excitation sources for X-ray fluorescence analysis.

Chemical analysis provides much more precise data about the sample, particularly the determination of metallic elements, mainly lead, cadmium, iron, calcium, sodium as well a.s anions, chlorides, fluorides, nitrates, carbonates and sulphates. The analyses are performed most frequently by spectrophotometry, atomic absorption spectrometry, or polarography in recent years radionuclide X-ray fluorescence and activation analysis have been used. 

Keywords Trace elements Radionuclides Environment Water Soil Aerosol Plant Neutron activation analysis Atomic absorption spectrometry Inductively coupled plasma-atomic emission spectroscopy Inductively coupled plasma-mass spectrometry X-ray fluorescence Electrochemical methods Speciation... 

Sodium silicate is somev at more difficult to analyze than many other materials because of the formation of the relatively long lived radionuclide Na whose emissions interfere with the detection of other elements. Nevertheless we were able to determine, in a sample of sodium silicate, that many heavy elements of toxicological concern were undetectable down to the ppm to ppb level in the undiluted silicate (13), An XRF spectrometer can be configured to perform sequential multi-elemental analyses. It is less sensitive to the elements of lower atomic number. Also, since the X-rays penetrate only to a depth of about 10 urn, the sample must be homogeneous. Solid samples must be presented to the X-ray beam with a flat surface. However, the relative ease of sample preparation and the ability to run glasses and solutions with only minor dilution make X-ray fluorescence a useful technique where analysis for a wide range of impurities is required,... 

There are also other techniques that are used frequently to characterize particulate matter collected from workplace air, for example. X-ray fluorescence (XRF) analysis - both lab-based wavelength-dispersive and hand-held energy-dispersive XRF spectrometry - are used for identification and quantitation of either bulk samples or air filters for numerous chemical elements. The latter is now available with both tube-excitation and radionuclide-excitation sources. 

It is also possible to make measurements in situ, for example portable gamma detection equipment can be used if the target radionuclides can be characterised by key-line gamma energy levels. Considerations of the specimen size leads to an important difference between in situ investigations of chemically contaminated land and radioactively contaminated land. It is possible to make field measurements in situ of the chemical concentration of metals in soil by using Portable X-Ray Fluorescence (PXRF) equipment. In PXRF, the specimen size is of the order of a few cubic millimetres. It is therefore much smaller than a typical specimen that would be extracted for laboratory analysis. ... 

Basically, the I content in the purified iodine fraction can be measured by different techniques. Due to the low specific activity of this long-lived radionuclide, direct 3 , y and X-ray measurement techniques show only a moderate detection capability better detection limits can be obtained by determination of the I mass present in the sample. Here, laser-induced fluorescence spectrometry offers in principle favorable results however, when this technique is applied, the difficulties associated with the preparation of the h chemical species at very low iodine concentrations have to be taken into consideration. The most sensitive I determination technique is neutron activation analysis, which leads to the formation of the... 

---