X-ray fluorescence spectrometers

A widely used procedure for determining trace amounts of selenium involves separating selenium from solution by reduction to elemental selenium using tellurium (as a carrier) and hypophosphorous acid as reductant. The precipitated selenium, together with the carrier, are collected by filtration and the filtered soflds examined directly in the wavelength-dispersive x-ray fluorescence spectrometer (70). Numerous spectrophotometric and other methods have been pubHshed for the deterruination of trace amounts of selenium (71—88). 

Desnica, V. and Schreiner, M. (2006). A LabVIEW-controlled portable X-ray fluorescence spectrometer for the analysis of art objects. X-Ray Spectrometry 35 280-286. 

An X-ray fluorescence spectrometer needs to resolve the different peaks, identify them and measure their area to quantify the data. There are two forms of X-ray spectrometers (Fig. 5.5), which differ in the way in which they characterize the secondary radiation - wavelength dispersive (WD), which measures the wavelength, and energy dispersive (ED), which measures the energy of the fluorescent X-ray (an illustration of the particle-wave duality nature of electromagnetic radiation, described in Section 12.2). 

Ti content in the polymer films was measured with a Princeton Gamma Tech System 4 x-ray Fluorescence Spectrometer. The conditions employed were Cr target, 50 keV source operating at 3 mA, 0.75 mm aperture, 4.8 mm beam stop, helium atmosphere and 100 sec. counting time. A calibration curve was constructed by plotting the fluorescence counts versus the amount of Ti in HB-HPR 206 films determined by Rutherford Backscattering Spectroscopic (RBS) analysis. 

A wide variety of X-ray fluorescence spectrometers may be used, depending on the nature and complexity of the sample, and on the number of samples to be analysed. To prove this and to indicate the substantial influence which the sample has on the choice of measuring instrument, let us consider some of the main characteristics of some X-ray fluorescence instruments used today [38]. These are shown in Table 14.11. 

Application of field-portable x-ray fluorescence spectrometers in mineral exploration, with examples from the Abitibi Greenstone Belt... 

Dzubay, T.G. Stevens, R.K. "Ambient Air Analysis with Dichotomous Sampler and X-ray Fluorescence Spectrometer" Environ. Sci. Technol., 1975, 9, 663. 

Elemental Analysis. A Phillips PW 1410/70 X-ray fluorescence spectrometer with Cr radiation was used to measure the relative quantities of Br in the molded polymer samples. Extractable bromide and chloride ions were detected with specific ion electrodes after a 48-hour, 120 C steam bomb extraction. 

Solar X-rays impinge on an asteroid s surface, generating fluorescent spectra that can be measured using an X-ray fluorescence spectrometer. During times when the Sun is... 

The highest performance X-ray fluorescence spectrometers contain goniometers. Their resolution, expressed in eV, can reach a few tens of electron volts. These instruments can be classified as ... 

The instrument used in this project was a Phillips manual vacuum x-ray fluorescence spectrometer. All analyses were made in the Analytical Chemistry Laboratories of the Illinois State Geological Survey. 

X-ray fluorescence analyses were performed on a Philips PV1400 x-ray fluorescence spectrometer using fused sample/polyvinylalcohol disks. FTIR spectra were collected using a Mattison Instruments Galaxy 2030 Series FTIR spectrometer (Mattison Instruments, Madison, USA). UV/VJS spectra were obtained from a Zeiss Spectralphotometer DM 4 (Zeiss, Oberkochen, Germany). 

A Spectrace QuanX energy dispersive X-ray fluorescence spectrometer was used, with a rhodium target X-ray tube, running on fundamental parameters... 

A Spectrace QuanX energy dispersive X-ray fluorescence spectrometer was used, which employed a rhodium target X-ray tube, fundamental parameters software, and pure element standards. Sample excitation conditions were 30kV, 0.10mA, 100 sec count, KaP for Fe, Co, Ni, Cu, Zn, As, Pt, Au, Bi, and Pb, followed by 50 kV, 0.72 mA, 60 sec count, for Pd, Ag, Sn, and Sb. Certified brass samples were run each day prior to sample runs to ensure instrument accuracy and precision. 

Speakman, R. J. Popelka, R. S. Glascock, M. D. Robertson, J. D. Report. Analysis of Obsidian Artifacts from Southern Peru Using a Field-Portable X-Ray Fluorescence Spectrometer, University of Missouri Research Reactor Center Columbia, MO, 2005. 

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. 

The metal concentrations in certain samples were determined using a XRF (Canberra) X-ray fluorescence spectrometer with radioactive sources of 109Cd, 55Fe and 241Am. 

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). 

Figure 8.35. Schematic layout of a dispersive X-ray fluorescence spectrometer...

In our experiment, the compression strength of supports was tested by an intellect strength tester (Model ZQJ, China). Specific areas, pore volume and average pore diameters were measured by a static physical absorber (Model ASAP-2000, America). The surface of catalyst was observed under an electron microscope (Model JEM-1200EX). The crystal structure was detected by an X-ray fluorescence spectrometer (Model 3015, Japan). The content of Ru was detected by a plasma spectrum instrument (Model ICPS-IOOOII). 

Knoth, J. and Schwenke, H., An x-ray fluorescence spectrometer with totally reflecting sample support for trace analysis at the ppb level. Fres. Z. Anal. Chem., 291 (1978) 200-204. 

Two x-ray fluorescence spectrometers were used for the analyses a General Electric XRD-6 for iron, copper, tin, and antimony, and a General Electric XRD-5 for nickel, silver, and lead (the latter machine has updated electronics and gave superior results for these three elements). Four certified standards from the National Bureau of Standards were used for each element to obtain a straight line calibration curve using linear regression (10). The experimental conditions used for the determination of each element were given by Carter et al. (10). 

Seven previously analyzed Claudian quadrantes (9) are fairly close in composition to the ones reported in this chapter. However, improved analytical techniques and use of a better x-ray fluorescence spectrometer for nickel, silver, and lead analyses have produced results that are probably more accurate than the previous ones. 

I am grateful to the Kelsey-Hayes Research and Development Laboratory in Ann Arbor, Mich., and to the Lewis Research Center of NASA in Cleveland for the use of their x-ray fluorescence spectrometers. Appreciation is also given to Simon Bendall and to A.H. Baldwin Sons Ltd. in London for supplying the coins for analysis. 

The 30-mm sediment slices of the segmented cylindrical cores obtained from box coring at the seven stations were dried, pulverized, and thoroughly mixed to yield a uniform sample for analysis. Sediment from each of these slices was analyzed by two independent methods. The first method used a Perkin-Elmer model 5000 atomic absorption spectrophotometer (AA) for the elements Fe, Mn, Ti, Pb, Zn, Cu, Cr, Ni, Co, Hg, and Cd (9). The second method utilized a Philips PW 1410 X-ray fluorescence spectrometer for the analysis of elements Fe, Mn, Ti, Ca, K, P, Si, Al, Mg, Na, Pb, Zn, Cu, Cr, V, and Ba (10). The AA analysis was chosen because of the known accuracy and sensitivity to a wide spectrum of elements. The XRF analysis was chosen for its accuracy and similar nondestructive mode of analysis equivalent to the shipboard XRF analysis. Good agreement between the AA and the XRF values was felt to be imperative because the Philips XRF equipment was to be used in the land-based multielement analysis of the CS -collected sediment samples. 

Fig. 15-1 X-ray fluorescence spectrometers. In this example, elements 1 and 2 in the sample emit characteristic wavelengths and k2- These wavelengths are separately measured by crystal diffraction in (a) or by pulse-height analysis in (b), where MCA = multichannel analyzer.

The second part of this paper is devoted to the procedure used for a quick setup of ten element analysis of gypsum and gypsum products on the Philips PW-1400 X-ray fluorescence spectrometer, utilizing alpha coefficients. Calibration data obtained with chemically analyzed specimens and their mixtures are compared with those based on synthetic standards prepared by blending pure chemicals with anhydrite. 

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