Elements techniques compared

The control technique of fuel distribution in uranium - graphite fiael elements seems to be most perform. The technique allows to determine weight of uranium or its connections in a chosen zone of fuel elements. There were used the sources of radiation on a basis radionuclide Am. The weight of uranium in fuel element or its parts is determined by combine processing of a tomograms, set received on several parallel layers of fuel element. The comparative results of tomographic researches and chemical analysis of weight of uranium in quarters of spherical fuel elements are resulted in the table. 

Lieser et al. [628] studied the application of neutron activation analysis to the determination of trace elements in seawater, with particular reference to the limits of detection and reproducibility obtained for different elements when comparing various preliminary concentration techniques such as adsorption on charcoal, cellulose, and quartz, and complexing agents such as dithizone and sodium diethyldithiocarbamate. 

The fluorescence technique combines the advantages of the large dynamic range of emission techniques with the simplicity and high selectivity of absorption techniques. Flame sources have been extensively used, however, for elements with refractory oxides, the ICP source has been found to be more satisfactory for AFS. A system for hollow cathode lamp excited ICP-AFS, as proposed by Demers and Allemand (1981), is commercially available as a modular simultaneous multielement ICP system. Although fluorescence techniques often offer two orders of magnitude sensitivity improvement over absorption, the multielement approach for AFS has not yet been commercially successful. Also promising for the future is the laser-excited furnace AFS where the detection limits for most elements are comparable to those of ICP-AES and for some elements, for eg, As, Cd, Pb, Tl, Lu, even lower (Omenetto and Human, 1984). The future for AFS techniques has been discussed by Stockwell and Corns (1992). 

Kohiyama et al. (1992) reported mean levels of nickel, iron and copper of 0.03, 0.30 and 0.04 mg/kg, respectively, in 10 samples of cocoa butter. Baxter et al. (2001) found comparable results from the determination of 23 elements in 42 cocoa butters and 22 CBA fats, mostly of known geographical origin and processing history, by the sensitive multi-element technique of inductively coupled MS. No distinction could be made between the cocoa butters based on geographical origin or deodorization, and the very low levels of most elements in the CBA fats meant that their presence in mixtures with cocoa butter could not be detected. 

The technique may be subject to a number of positive and/or negative systematic errors, depending on the element to be determined, the instrumental technique used, the matrix composition, and still other factors. However, as shown in Table 2.2, there is a tendency towards the use of the standard additions method and CRMs to minimize some possible matrix effects and to ensure validity of results. Nevertheless, it appears from the survey of the literature that the solubilization sampling introduction technique compares favorably with other atomic spectrometric methods for the determination of trace elements in a variety of matrices. 

ICP-MS is a multi-element technique suitable for the analysis of liquid samples, which provides higher selectivity and detection power and LoDs lower than other multi-element techniques, such as ICP-AES. These characteristics make ICP-MS an excellent tool for the detailed characterization of the elemental composition of beverages. In this context, ICP-MS was the technique selected for the determination of 31 trace elements in wine at concentrations ranging from 0.1 to 0.5 ng ml-1 [82]. Samples were diluted 1 + 1 and it was investigated whether a matrix effect derived from the presence of ethanol could be overcome by using a microconcentric nebulizer with membrane desolvation. The authors compared their results with those obtained using a conventional Meinhard nebulizer and concluded that the matrix effect observed could only be minimized by using an internal standard with the Meinhard nebulizer, but not with the other one. 

The following elements have better detectability in simple solutions by flame emission techniques compared with atomic absorption techniques Ca, Ba, Y, La, W, Re, Ir, In, Al, Sn, most rare earths, all alkali metals. 

Overall methods using either different or no sample preparation procedures and various detection techniques have also been compared. Thus, fine ambient aerosol was analysed for 11 elements by using US-assisted slurry formation for 15 min prior to AAS, as well as by X-ray fluorescence spectroscopy and laser ablation ICP-MS. Sample treatments were found to provide similar results. However, the detection techniques compared the number of target analyte elements to be determined, detection limits and purchase costs [10],... 

In order to demonstrate the analytical capabilities of LI-MS, the results it provided for glass samples were compared with those obtained using other multi-element and microanalytical techniques to determine 30 trace elements [195]. This comparison revealed the number of elements that can be determined by LI-MS to be similar to that of other multi-element techniques such as instrumental neutron activation analysis (INAA) or LA-ICP-MS. However, INAA was unable to determine some geochemically interesting trace elements such as Nb and Y, and LA-ICP-MS analyses were occasionally disturbed by the formation of argon clusters. In contrast to LA-ICP-MS, LI-MS can also measure single-isotope elements such as Nb, Y, Pr and Ho also, it requires no wet chemistry. 

A partial order ranking is easily developed by the Hasse diagram technique comparing each pair of elements and storing this information in the Hasse matrix which is a (n x n) antisymmetric matrix for each pair of elements s and t the entry hst of this matrix is ... 

In this work PIXE and INAA nuclear techniques were applied to a 1993 lichen survey held in Portugal. The two techniques determined 46 elements with 16 common elements. The common elements were compared and conclusions were attempted to select the best values, based on the concentration patterns obtained. It was concluded that ... 

An alternative method, termed DNP (Dynamic Nuclear Polarisation), relies on the transfer of polarisation from unpaired electrons onto nuclear spins in the solid state but has been further developed to significantly enhance the sensitivity of solution-state NMR, as described briefly below. The technique has been applied to boost the polarisation levels for low-7 heteronuclear spins in particular and shows most promise to date for and N observation the initial report on the technique described a gain in signal-to-noise in excess of 10,000-fold for both these elements when compared to data collected at thermal equilibrium [115]. The hyperpolarisation of P and Si has also been demonstrated. 

Methods for elemental analyses For the determination of elements (e.g., lead, cadmium, etc.) the method of ICP-MS (EN Standard, 2004) should be preferred over AAS methods, whenever possible. The ICP-MS determination of iron could be subject to polyatomic interferences so the ICP-OES EN Standard, 1997b method should be applied. For mercury and selenium AAS hydride techniques (EN Standard, 1997c ISO, 2003b) should be applied due to the higher sensitivity of these techniques compared with the ICP-MS technique (EN Standard, 2004). All of the cited standards (see Table 1.5) can be used for the control of the parametric value. 

Fassel and Kniseley reported experimentally determined detection limits for 61 elements that compare favorably with detection limits obtained by atomic absorption, atomic fluorescence, and flame emission methods. Interelement interferences are lower than by other methods and interferences due to PO4" and apparently are negligible. The technique seems well adapted to simultaneous multielement analyses through use of direct reading spectrometers. 

Precise wavelength measurements are not required for qualitative spectrochemical analysis. Usually measurements to 0.05 to 0.10 A will suffice, since the spectroscopist usually relies on the identification of three or four spectral lines to prove the presence of an element in the analytical sample. Use also is made of unknown spectra of elements to compare with the unknown sample. This technique does not require measurements of wavelengths of spectral lines. 

An optical multichannel analyzer was used to obtain both peak height and peak area and was corrected for background. Results indicate either peak height or peak area can be used analytically except under electronic overload conditions. The method was used with a U. S. Geological Survey rock sample to determine Al, Fe, Ca, and Ti. The multielement technique compared favorably with concentrations of the four elements as reported by the U. S. Geological Survey. 

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