XRF spectrometry

XRF spectrometry typically uses a polychromatic beam of short-wavelength X-radiation to excite lines with longer wavelength characteristics from the sample... 

XRF spectrometry is based on the principle that primary X-rays (from an X-ray tube or radioactive source) are incident upon a sample and create inner shell (K, L, M) vacancies in the atoms of the surface layers. These vacancies de-excite by the production of a secondary (fluorescent) X-ray whose energy is characteristic of the elements present in the sample. Some of these characteristic X-rays escape from the sample and are counted and their energies measured. Comparison of these energies with known values for each element (e.g., Van Grieken and Markowicz 1993, Parsons 1997) allow the elements present in the sample to be identified and quantified. 

U-XRF spectrometry synchrotron-based micro-x-ray absorption near-edge stmcture spectroscopy multiple collector inductively coupled plasma mass spectrometry... 

Hernandez-Caraballo et al. [91,92] evaluated several classical chemometric methods and ANNs as screening tools for cancer research. They measured the concentrations of Zn, Cu, Fe and Se in blood serum specimens by total reflection XRF spectrometry. The classical chemometric approaches used were PCA and logistic regression. On the other hand, two neural networks were employed for the same task, viz., back-propagation and probabilistic neural networks. 

Majcen et al. [93] studied linear and nonlinear multivariate analysis in the quality control of industrial titanium dioxide white pigment using XRF spectrometry. 

The tungsten content of a reference ore sample was measured both by X-ray fluorescence (XRF) spectrometry, the standard method, and by inductively coupled plasma-atomic emission spectrometry (ICP). The results as weight percent tungsten are given in the following table. Are the results of the two methods significantly different at the 95% confidence level Is there any bias in the ICP method (Hint The standard method can be considered to have a mean = /a.)... 

The equation nA = 2d sin 9 is known as the Bragg equation. The important result of this equation is that at any particular angle of incidence 9, only X-rays of a particular wavelength fulfill the requirement of staying in phase and being reinforced, and are therefore diffracted by the crystal. Diffraction of X-rays by crystals forms the basis of XRD for crystal structure determination and is also the reason XRF spectrometry is possible, as will be seen. 

Like any other instrumental technique used to analyze solid samples, XRF spectrometry is subject to matrix effects and the problems derived from differences in grain size when samples are used in pellet form. Both shortcomings can be circumvented by dissolving the material and separating the lanthanides by using one of the above-described procedures. After separation, the diflPerent fractions containing the analytes are placed on solid supports for analysis [23]. This procedure is usually employed with some geological samples that are attacked by... 

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. 

The composition of a specimen is often determined by X-ray fluorescence (XRF) spectrometry, which performs rapid, qualitative, and semiquantitative determination of major and minor surface elements. Although both wavelength- and energy-dispersive (ED) analyzers can be used to detect the secondary X-rays, ED-XRE instruments are more common for the compositional determination of archaeological and conservation samples. Detection limits of 0.1% are expected therefore, the analysis is difficult for trace elements. A laboratory XRE system, commonly used to quantify elements in metal and ceramic samples (noninsulating materials need to be coated), is considered to be an indispensable tool. As with all these surface analytical techniques, care has to be taken that weathering products (thick patinas or corrosion crusts) do not obscure bulk analysis results. Thus, samples are normally prepared to provide a flat polished surface to produce quantitative results. 

Modern analytical such as infrared (IR) spectroscopy, liquid chromatography (LC), and gas-liquid chromatography (GLC) are in use for the identification of organic components, whilst the mineral constituents can be estimated by using X-ray fluorescence (XRF) spectrometry. X-ray diffraction (XRD), atomic absorption spectrometry (AAS), or inductively coupled plasma (ICP) atomic emission spectrometry (AES). 

X-ray diffraction and X-ray fluorescence (XRF) spectrometry have been utilized in the differentiation of man-made fibers, but the sample amounts required are large, so that some modifications for single fiber analysis are required. Total reflection XRF has many advantages in this respect. 

X-ray analysis Two techniques. X-ray fluorescence (XRF) spectrometry and electron microprobe, are... 

Onsite total analysis by energy dispersive XRF spectrometry is increasingly popular. When linked with various contour-mapping software packages, the technique can give a rapid assessment of a suspected pollution incident. 

Different techniques are in use for analysis of the filtration fraction and concentrates. Most often multielement techniques such as ICP AES/MS and X-ray fluorescence (XRF) spectrometry are applied. Use of electrochemical methods and different techniques of atomic absorption spectrometry (AAS) is also possible. 

A complementary way of considering these attenuation phenomena is to identify the limiting thickness of a sample below which absorption/enhancement effects are essentially negligible and so relevant matrix corrections may be ignored. Analysis of such thin films may then be undertaken without applying any matrix corrections. By convention, a 1% attenuation is normally taken as the limit for thin film criteria, and some representative values are also listed in Table 3. Satisfying thin film criteria is particularly important in applications such as direct analysis of dust particles collected on a filter membrane, which then serves directly as the sample substrate for XRF spectrometry. 

Table 3 Typical spectrometer operating parameters and detection limits appropriate for the analysis of silicate rocks by WD-XRF spectrometry. Comparison is made with ED-XRF detection... 

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