Elemental analyses, spectral nuclear

Although ICP-MS has been used for analysis of nuclear materials, often the entire instrument must be in an enclosed hot enclosure [350]. Sample preparation equipment, inlets to sample introduction systems, vacuum pump exhaust, and instrument ventilation must be properly isolated. Many of the materials used in the nuclear industry must be of very high purity, so the low detection limits provided by ICP-MS are essential. The fission products and actinide elements have been measured by using isotope dilution ICP-MS [351]. Because isotope ratios are not predictable, isobaric and molecular oxide ion spectral overlaps cannot be corrected mathematically, so chemical separation is required. 

The review by Maenhaut (1990) (Recent advances in nuclear and atomic spectrometric techniques for trace element analysis - A new look at the position of PIXE) is an excellent review by a respected PIXE practitioner. It includes a comparison of DLs on a solid sample basis for seventeen elements for seven analytical techniques INAA, ED-XRE, PIXE, ICP-AES, ETA-AAS, LIE-ETA, ICP-MS, and also includes a good comparison of some characteristics (cost, spectral interferences, matrix effects, multielement capability) of these methods (and TXRE). 

The determination of trace and ultra trace amounts of individual Rare earth elements (REE) in complex matrices is one of the most challenging areas of analytical chemistry. Rapid studies made in analytical methodology have brought forth many powerful analytical tools for the determination of trace and ultra trace amounts of lanthanides. These are based on spectral, nuclear, X-ray, electrochemical and other chemical properties of lanthanides. Each technique provides a different and unique approach for the determination of lanthanides and offers certain advantages over others for a given analysis of complex materials. Hence it is desirable to compare the performance of various techniques available in terms of i) primary criteria like sensitivity, selectivity and precision and accuracy and ii) auxiliary criteria like speed, cost of equipment, availability etc. while choosing analytical technique. 

The energy levels in the inner electron shells are comparatively little affected by the chemical environment of the atoms. Thus, a spectral analysis of the characteristic X-ray emission is well suited for elemental analysis. The relation between the wavelength A of a particular X-ray line and the nuclear charge Z of the corresponding atom is given by Moseley s law... 

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. 

Instrumental analysis is possible if spectral inter ference can be avoided by a proper choice of the incident energy or the measuring conditions (see Interferences). If not, the radionuclide B, formed from the analyte element A, has to be separated radiochemically from interfering radionuclide(s) D, formed out of interfering element(s) C. The latter case is called radiochemical analysis, in contrast to instrumental analysis for the former. This section deals with some major differences between radiochemical separation and common chemical separation, used for non-nuclear methods of analysis. 

The narrow spectral line of a DL enables isotope selective analysis. For light and heavy elements (such as Li and U) the isotope shifts in spectral lines are often larger than the Doppler widths of the lines, in this case isotopically selective measurements are possible using simple Doppler-limited spectroseopy - DLAAS or laser induced fluorescence (LIF). For example, and ratios have been measured by Doppler-limited optogalvanic. spectroscopy in a hollow cathode discharge. DLAAS and LIF techniques have been combined with laser ablation for the selective detection of uranium isotopes in solid samples. This approach can be fruitful for development of a compact analytical instrument for rapid monitoring of nuclear wastes. 

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