XRF spectroscopy

Electron Microprobe A.na.Iysis, Electron microprobe analysis (ema) is a technique based on x-ray fluorescence from atoms in the near-surface region of a material stimulated by a focused beam of high energy electrons (7—9,30). Essentially, this method is based on electron-induced x-ray emission as opposed to x-ray-induced x-ray emission, which forms the basis of conventional x-ray fluorescence (xrf) spectroscopy (31). The microprobe form of this x-ray fluorescence spectroscopy was first developed by Castaing in 1951 (32), and today is a mature technique. Primary beam electrons with energies of 10—30 keV are used and sample the material to a depth on the order of 1 pm. X-rays from all elements with the exception of H, He, and Li can be detected. 

Barium can also be deterruined by x-ray fluorescence (XRF) spectroscopy, atomic absorption spectroscopy, and flame emission spectroscopy. Prior separation is not necessary. XRF can be appHed directly to samples of ore or products to yield analysis for barium and contaminants. AH crystalline barium compounds can be analy2ed by x-ray diffraction. 

Thomsen, V. and Schatzlein, D. (2002). Advances in field-portable XRF. Spectroscopy 17-7 14-21. 

One of the problems faced in XRF spectroscopy is the fact that the absolute sensitivity of an element decreases with atomic number, and this decrease is mostly considerable for light elements. For quite some... 

The introduction of EU directives on Waste Electrical and Electronic Equipment and Reduction of Hazardous Substances has highlighted the need for precise and repeatable elemental analysis of heavy metals in the plastics production process. X-ray fluorescence (XRF) spectroscopy has emerged as the most economical and effective analytical tool for achieving this. A set of certified standards, known as TOXEL, is now available to facilitate XRF analyses in PE. Calibration with TOXEL standards is simplified by the fact that XRF is a multi-element technique. Therefore a single set of the new standards can be used to calibrate several heavy elements, covering concentrations from trace level to several hundred ppm. This case study is the analysis of heavy metals in PE using an Epsilon 5 XRF spectrometer. 

Bos et al. [94] compared the performance of ANNs for modelling the Cr-Ni-Fe system in quantitative XRF spectroscopy with the classical Rasberry-Heinrich model and a previously published method applying the linear learning machine in combination with singular value decomposition. They studied whether ANNs were able to model nonlinear relationships, and also their ability to handle non-ideal and noisy data. They used more than 100 steel samples with large variations in composition to calibrate the model. ANNs were found to be robust and to perform better than the other methods. 

The typical thickness of metallized Al layers ranging from few nm to several hundred nm corresponds to an area weight of approximately 100 mg m-2. Such film thicknesses cannot be reliably measured by mechanical meters or by weighing. Other laboratory measurement techniques are used, for example X-ray fluorescence (XRF) spectroscopy, ellipsometry, or ion scattering (RBS). All these techniques are unsuitable for in-line control during metallization, because they require... 

Ti(acac)2 was rapidly and quantitatively analyzed by X-ray fluorescence (XRF) spectroscopy. Fe(acac)2 was similarly determined by XRF with correction for Compton scattering. An instrumental geometrical factor and an equivalent wavelength were obtained experimentally, while all the other factors were calculated with the mass absorption coefficients of Fe ". K and XRF spectra of Cr(acac)3 and other Cr compounds were measured with a Bragg spectrometer. The relative intensities of the 3, K 2, K / and K lines with respect to the K line confirm the chemical effect on the intensity... 

Our knowledge of the geochemistry and mineralogy of Venus surface primarily comes from six types of information (i) elemental analyses of several major elements by X-ray fluorescence (XRF) spectroscopy (ii) analyses of potassium, uranium, and thorium by y-ray spectroscopy ... 

In geochemistry, rare earth element (REE) patterns constitute a useful tool for interpreting geological processes. LI-MS produces reasonably good REE patterns, as shown in Fig. 9.24, which is a plot of Cl normalized REE concentrations alongside the results obtained with INAA, HPLC, LA-ICP-MS, synchrotron X-ray fluorescence (SY-XRF) spectroscopy and secondary ion mass spectrometry (Tl-MS). INAA and TI-MS surpass... 

Thomsen, E., and D. Schatzlein. 2002. Advances in field-portable XRF. Spectroscopy VKJf- 14-21. Tieszen, Larry L., and Thomas Eagre 1993. Effect of diet quality on the isotopic composition of... 

The tests utilized to measure these contaminants and degradation by-products include infrared (IR) spectroscopy, electronic particle counting (PC), Karl Fischer titration (KFT), atomic emission spectroscopy (AES) and X-ray fluorescence (XRF) spectroscopy. These methods are available in the form of off-line or at-line benchtop instruments and online/in-line sensors. Most off-line instruments are automated to provide several hundred analyses per day by a single technician. At-line instruments and sensors permit immediate results and diagnostic capabilities. Online sensors can be integrated into machinery control systems to provide real-time monitoring capability. 

Analysis for metals in solids can be carried out by two different approaches, namely direct analysis of the solid, or after decomposition of the matrix to liberate the metal. Samples can be analysed directly for metals by using, for example, X-ray fluorescence (XRF) spectroscopy (see Chapter 11). This present chapter principally focuses on methods of decomposition of the matrix to liberate its metal content. In addition, selective methods of metal extraction are considered, together with appropriate methods of analysis. 

It can be seen that for both soil samples the XRF results obtained produce similar concentration values to those obtained after acid digestion using the US EPA Method 3050B, followed by FAAS. The use of XRF spectroscopy, which analyses the soil directly, provides faster analysis than that achieved when using the acid digestion/FAAS procedure. 

Classical methods for analysis of manganese have been the periodate method in air, and the permanganate method in water (Saric 1986). Nowadays, among the solid-state analytical methods available, neutron activation analysis (NAA) is the most reliable to determine manganese in biological and environmental materials. This method of choice combines both high specificity, sensitivity and reproducibility for very low concentrations of manganese, whereas X-ray fluorescence (XRF) spectroscopy showed standardization problems and arc/ spark emission spectroscopy suffered from electrode contamination (Chiswell and Johnson 1994). 

Table 4. Chemical composition (mol%) measured by XRF spectroscopy and calculated glassy matrix composition (in parenthesis) of Ultropaline Super Transparent (UST) dental porcelain (containing 12 vol% leucite particles)...

It is possible for atoms to absorb higher energy radiation, in the X-ray region such absorption may result in the inner shell (core) electrons being promoted to an excited state, with the subsequent emission of X-ray radiation. This process forms the basis for qualitative and quantitative elemental analysis by XRF spectroscopy, as well as other X-ray techniques, discussed in Chapter 8. 

Figure 36. Lead levels in bone can be measured in vivo using XRF spectroscopy, (a) y-rays or X-rays are used (source) to eject either L-shell electrons (L-XRF) or K-shell electrons (K-XRF) from lead in bone when outer-shell electrons fill this vacancy, photons are released (fluorescence) and are monitored by the detector (10, 523). A typical X-ray fluorescence spectrum [(b), e.g., of a 112 pg Pbg phantom ) provides the number of counts observed as a function of photon energy. Emissions characteristic of lead occur at 72.8 keV (PbKa2), 75.0 keV (PbKoti), and 84.9 keV (Pb Kpi) (436, 523). Measurements on actual samples are correlated with those obtained from standard phantoms made of plaster-of-paris and doped with a known amount of lead to obtain bone lead concentrations in micrograms of Pb per gram (pg Pbg bone). The bone lead levels obtained by this method correlate extremely well with independent measurements of BLL (c). [Parts (a) and (c) adapted from (524). Part ( ) adapted from (436).]...

Lead levels in bone can be measured in situ accurately and quantitatively using XRF spectroscopy (Fig. 36) (10, 436, 523). X-ray fluorescence spectrometers [Fig. 36(a)] use y-rays or X-rays to eject either L-shell electrons... 

Simple tests can only indicate which polymer type the plastic contains. To identify materials more precisely, it is necessary to use instrumental analytical methods. Each technique provides specific information either about which polymers or which additives are present, so it is usually necessary to use several in combination. For example, gas chromatography-mass spectrometry (GC-MS) is a destructive technique which allows identification of the polymer, plasticizer and other organic components. X-Ray Fluorescence (XRF) spectroscopy is an effective, non-destructive surface technique for identifying inorganic fillers, pigments and metal components, but carmot be used to identify polymers. 

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