Energy-dispersive X-ray fluorescence techniques

Kumar S, Singh S, Garg ML, et al. 1989. Elemental analysis of environmental samples using energy dispersive x-ray fluorescence technique. Indian J Environ Health 31(1) 8-16. 

The diffusion of Cu in ZnS thin films was investigated at 80 to 400C by using the energy-dispersive X-ray fluorescence technique. The thin films were deposited, by spray pyrolysis, onto a glass substrate. The temperature dependence of the Cu diffusion coefficient could be described by ... 

Chemical analysis of the metal can serve various purposes. For the determination of the metal-alloy composition, a variety of techniques has been used. In the past, wet-chemical analysis was often employed, but the significant size of the sample needed was a primary drawback. Nondestmctive, energy-dispersive x-ray fluorescence spectrometry is often used when no high precision is needed. However, this technique only allows a surface analysis, and significant surface phenomena such as preferential enrichments and depletions, which often occur in objects having a burial history, can cause serious errors. For more precise quantitative analyses samples have to be removed from below the surface to be analyzed by means of atomic absorption (82), spectrographic techniques (78,83), etc. 

Elemental chemical analysis provides information regarding the formulation and coloring oxides of glazes and glasses. Energy-dispersive x-ray fluorescence spectrometry is very convenient. However, using this technique the analysis for elements of low atomic numbers is quite difficult, even when vacuum or helium paths are used. The electron-beam microprobe has proven to be an extremely useful tool for this purpose (106). Emission spectroscopy and activation analysis have also been appHed successfully in these studies (101). 

Asbestos fiber identification can also be achieved through transmission or scanning electron microscopy (tern, sem) techniques which are especially usefiil with very short fibers, or with extremely small samples (see Microscopy). With appropriate peripheral instmmentation, these techniques can yield the elemental composition of the fibers using energy dispersive x-ray fluorescence, or the crystal stmcture from electron diffraction, selected area electron diffraction (saed). 

Elements chosen from the limited NURE multi-element geochemical packages that may be pathfinders for porphyry-style deposits (Lefebure Ray 1995) include Ba, Co, Cu, Mn, Pb, Ti, V, and Zn. Under the NURE program, two analytical techniques were used energy dispersive x-ray fluorescence (Cu and Pb) and neutron activation (Ba, Co, Mn, Ti, V, and Zn). Single element plots and element association plots were generated. Geochemical data for pond sediments collected over the Pebble deposit in 2008... 

A numerical matrix correction technique is used to linearise fluorescent X-ray intensities from plant material in order to permit quantitation of the measurable trace elements. Percentage accuracies achieved on a standard sample were 13% for sulfur and phosphorus and better than 10% for heavier elements. The calculation employs all of the elemental X-ray intensities from the sample, relative X-ray production probabilities of the elements determined from thin film standards, elemental X-ray attenuation coefficients, and the areal density of the sample cm2. The mathematical treatment accounts for the matrix absorption effects of pure cellulose and deviations in the matrix effect caused by the measured elements. Ten elements are typically calculated simultaneously phosphorus, sulfur, chlorine, potassium, calcium, manganese, iron, copper, zinc and bromine. Detection limits obtained using a rhodium X-ray tube and an energy-dispersive X-ray fluorescence spectrometer are in the low ppm range for the elements manganese to strontium. 

All raw and treated coals were analyzed at Ames Laboratory for trace, major, and minor elements using energy-dispersive x-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and atomic absorption spectrophotometry (AA). General analytical procedures employed for each of these techniques are discussed separately below. 

Kovarsky et al have used the SIMS method to determine the mole fraction in InGaN [8], Their technique is based on a comparison of the relative signal intensities of CsM+ (M = In, Ga) and does not require reference samples. The SIMS results were independently confirmed by XRD, energy dispersive X-ray fluorescence spectroscopy, EPMA and SNMS, and the absolute value of the InN mole fraction has a relative accuracy <15%. 

The energy dispersive x-ray fluorescence spectrometer, which had been developed recently as a qualitative analysis instrument, showed promise of meeting the goals of the new laboratory (1). Its unique features, which earned it the name, The Curators Dream Instrument, are The measurements require neither sampling nor alteration of the object in any way. Systems for obtaining quantitative analysis data are now operational (I). Concentrations of up to thirty elements above chlorine (Z = 17) can now be printed out simultaneously. Techniques have been developed that minimize errors caused by sample size, shape, position, overlapping spectral peaks, matrix effects, and baseline compensation. Interpretative procedures have been established that recognize the shallow depth of penetration of the excitation radiation (2). 

Angeyo KH, Patel JP, Mangala JM, et al. 1998. Measurement of trace element levels in Kenyan cigarettes with the energy dispersive x-ray fluorescence spectroscopy technique. J Trace Microprobe Tech 16(2) 233-246. 

Zaichick VYand Zaichick SV (1999) Energy-dispersive X-ray fluorescence analysis of iodine in thyroid puncture biopsy specimens. J. Trace and microprobe Techniques, 17(2) 219-232. 

Examples of applications of X-ray spectrometric analytical techniques to elemental determinations in a variety of materials are presented in Table 2.12. Some recent applications papers may be mentioned. Total reflection XRF has been applied by Xie et al. (1998) to the multielement analysis of Chinese tea (Camellia sinensis), and by Pet-tersson and Olsson (1998) to the trace element analysis of milligram amounts of plankton and periphyton. The review by Morita etal. (1998) on the determination of mercury species in environmental and biological samples includes XRF methods. Alvarez et al. (2000) determined heavy metals in rainwaters by APDC precipitation and energy dispersive X-ray fluorescence. Other papers report on the trace element content of colostrum milk in Brazil by XRF (da Costa etal. 2002) and on the micro-heterogeneity study of trace elements in uses, MPI-DING and NIST glass reference materials by means of synchrotron micro-XRF (Kempenaers etal. 2003). 

Alvaefz am, Estevez Alvaeez JR and Padilla Alvaeez R (2000) Heavy metal analysis of rainwaters by nuclear related techniques application of APDC precipitation and energy dispersive X-ray fluorescence. J Radioanal Nud Chem 245 485-489. 

Test methods that might be used for sulfur determination applications in fuels include techniques such as lead acetate paper tape, oxidative combustion followed by gas chromatographic separation for flame photometric detection [4], and energy dispersive X-ray fluorescence with coaxial proportional counter detectors [5]. The first of these two methods was recently issued as a new standard D 7041 by ASTM. However, these and other corrunercially available analyzers, such conventional on-line/at process sulfur by combustion and UVF analyzers typically require analytical cycle times of 4—10 min. This delay in reporting the sulfur concentration levels limits the real time detection capability of changes in the sulfur concentration of fast moving or rapidly changing transport or process streams. 

Numerous techniques and instrumental methods can be used to measure sulfur in gasoline and diesel fuels [3]. It is beyond the scope of this paper to cover any of the standard techniques in detail. Unfortunately, many of the traditionally used techniques are out of consideration for analyzing fuels at low levels because of inadequate sensitivity or lack of precision at those levels. For instance, a study group comprised of 69 industry participants has recommended that Energy Dispersive X-ray Fluorescence (EDXRF) and some other older technologies be dropped fi-om consideration for analyzing fuels at the 30 ppm level [3],... 

Another area in which PIMs show considerable promise is chemical analysis. The use of PIMs in the construction of ISEs and optodes is well established, but their potential use in analytical separation is only starting to be explored. PIMs are particularly useful in solid-phase extraction (SPE) for preconcentration of analytes [17,18]. Also, Eonths et al. have used a PIM containing Aliquat 336 as the carrier for the preconcentration of Cr(VI) prior to its determination in the membrane by energy-dispersive X-ray fluorescence spectrometry [47]. Flat-sheet PIMs can also be conveniently incorporated into separation modules for use in online analytical techniques such as flow injection analysis. For example, a D2EHPA-based PIM has been used in a separation module incorporated into a flow injection analysis system for the determination of Zn(II) [35]. This new approach has interesting implications for use in automated analysis, particularly in held instruments for the continuous monitoring of pollutants. 

Overview. Microscopy Techniques Light Microscopy Sample Preparation for Light Microscopy X-Ray Microscopy. Sample Handling Comminution of Samples. Sampling Theory Practice. Sulfur. X-Ray Fluorescence and Emission Energy Dispersive X-Ray Fluorescence. 

Other analytical techniques have less frequently been used nuclear magnetic resonance spectroscopy (NMR) (e.g., tocopherols in toothpaste by hyphenated LC-NMR), energy dispersive X-ray fluorescence (ED-XRF) (e.g., heavy metals determination), surface enhanced Raman scattering (e.g., determination of 4-aminobenzoic acid or PABA, in sunscreens), neutron activation analysis (e.g., determination of iron and zinc), and thermometric analysis (e.g., fluoride in toothpaste). 

Total reflection X-ray fluorescence (TXRF) spectrometry is a trace elemental microanalysis technique based on conventional energy dispersive X-ray fluorescence. It has become increasingly popular in the last decade and is applied in almost every field of trace elemental analysis where low detection limits and multielement capabilities are required. Like all X-ray techniques, TXRF is nondestructive making it extremely useful and important in areas where samples are precious and/or need to be used for further characterization. New tabletop instruments make this technique affordable and more versatile as it can be used also for field research. In the semiconductor industry, TXRF is now routinely applied to scan wafers for impurities on the surface and in near-surface layers. The following article introduces the basic principle of TXRF and its instrumental features and discusses various applications of this technique. 

EDXRF (energy dispersive x-ray fluorescence) spectrometry works without a ciystal. An EDXRF spectrometer includes special electronics and software modules to take care that all radiation is properly analyzed in the detector. It provides a lower cost alternative for applications where less precision is required. The high-end uses the 3D EDXRF techniques featuring a 3-dimensional, polarizing optical geometry. 

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