XRF spectrometers

DETERMINATION OF COATINGS THICKNESS BY MEANS OF DESK-TOP XRF SPECTROMETERS... 

The first XRF spectrometers employed the wavelength dispersive methodology, which is schematically illustrated in the upper half of Fig. 7.17. The x-rays emanating from the source are passed through a suitable filter or filters to remove any undesired wavelengths, and collimated into a beam that is used to irradiate the sample. For instance, one typically uses a thin layer of elemental nickel to isolate the Ka lines of a copper x-ray source from contamination by the Kp lines, since the K-edge absorption of nickel will serve to pass the Kq, radiation but not the Kp radiation. 

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. 

J. Zieba-Palus, R. Borusiewicz and M. Kunicki, PRAXIS - combined /i-Raman and p-XRF spectrometers in the examination of forensic samples. Forensic Sci. Int., 175, 1-10 (2008). 

Techniques of microscopic XRF ( j,-XRF) developed in the last 20 years provide 2D images and elemental maps of each element present in the target material. Portable/in situ p-XRF, j,-XRF spectrometers synchrotron-based ( -SRXRF) and micro-x-ray absorption spectroscopy/micro-x-ray absorption near-edge structure spectroscopy (XAS/ J,-XANES) have improved the mineralogical characterization, as well as the elemental and chemical imaging of samples at the submicrometer scale [61]. 

ANNs were compared with univariate linear regression in order to calibrate an XRF spectrometer to quantify Ti, V, Fe, Ni and Cu in polymetallic ores by Kierzek et al. [85]. 

In 2006, a table-top energy-dispersive XRF (ED-XRF) spectrometer was acquired by the Archaeometry Lab to facilitate non-destructive analysis of obsidian and other types of artifacts. One of the first projects performed on the new XRF spectrometer was the re-analysis of the geological samples from sources in Peru. As a result, it is now possible for the Archaeometry Lab to use either XRF or NAA to successfully determine the provenance of obsidian artifacts from Peru. Due to its light weight, the spectrometer also has the potential to be transported from the laboratory to museums and to archaeological sites for in situ analysis. 

The light-weight Elva-X energy dispersive XRF spectrometer employed for this study has an air-cooled rhodium target anode X-ray tube with 140 micron Be window and a thermoelectrically cooled Si-PIN diode detector. The detector... 

Since MURR acquired the Elva-X ED-XRF spectrometer, investigations of its capability with respect to Andean obsidian have been ongoing. Although the measurement precision for XRF is less than NAA, when a rapid, non-destructive analysis is required XRF can be used quite successfully. As shown in Figures 5 and 6, the elements Rb, Sr, and Fe indicate no overlap at the 95% confidence level. Thus, these elements are then the most powerful discriminating elements available by XRF for the sources in this region. 

The analyses were performed at The Henry Francis du Pont Winterthur Museum on a Kevex 4525P energy dispersive XRF spectrometer low-level radioactive isotopes were used for the incident radiation (4). The pigment area analyzed was successively irradiated by an iron-55 source, an americium-241 source, and a cadmium-109 source. A qualitative pigment analysis takes only 6 min. Neither the coloring matter nor the silk fabric is altered in any way by the measurement. Figure 8 shows our XRF system setup for the analysis of pigments on painted and printed silks. 

The determination of the compositions was carried out using a Philips PW 1480 wavelength dispersive X-ray fluorescence (XRF) spectrometer. All the chemical elements were analysed using a side window Sc-Mo target X-ray tube and under a vacuum path. 

These analyses were made on a Phillips PW 2400 XRF spectrometer, and showed that the 0.71 mm fraction contained the maximum content of several metals, notably iragnesium. Again this is based on results with only one randomly chosen sample and the observations need to be verified with some more analysis. 

The BET surface areas of the zeolite samples were determined by N2 adsorption-desorption at -196 C in a Micromeritics ASAP 2010 equipment. The adsorption data were treated with the full BET equation. The t-plot method was applied in order to obtain an estimation of the micropore volume. The determination of the compositions was carried out using a Philips PW 1480 wavelength dispersive X-ray fluorescence (XRF) spectrometer. The crystallinity and the unit cell size were established by a Philips PW 1710 X-ray diffractometer (XRD) with CuKa radiation (A.=1.5406A) and Ni filter. 

The XRF spectrometer utilizes an X-ray source to irradiate a small quantity of the sample. The X-ray source raises the energy level of the atoms in the sample, resulting in a corresponding release of X-ray energy by the excited atoms. Depending... 

Houwen et al. (180) have recently demonstrated the application of a rig site X-ray fluorescence (XRF) spectrometer to determine the concentration of barite in both water- and oil-based drilling fluids. The XRF measurement enables the total solids content of the drilling fluid to be broken down into the so-called high gravity solids (barite) and low-gravity solids (bentonite and drilled solids). Houwen et al. (180) have shown that the current routine technique of estimating the barite con-... 

TABLE 1—Typical LLDs in lubricating oils for different type of XRF spectrometers. All... 

The ceramics industry routinely measures 6-12 elements quantitatively in both pressed pellet and fusion bead form for quality control. The elements (reported as oxides) vary in concentration from 0.01 to 70 wt%. Using a modern XRF spectrometer, aluminum... 

Sodium silicate is somev at more difficult to analyze than many other materials because of the formation of the relatively long lived radionuclide Na whose emissions interfere with the detection of other elements. Nevertheless we were able to determine, in a sample of sodium silicate, that many heavy elements of toxicological concern were undetectable down to the ppm to ppb level in the undiluted silicate (13), An XRF spectrometer can be configured to perform sequential multi-elemental analyses. It is less sensitive to the elements of lower atomic number. Also, since the X-rays penetrate only to a depth of about 10 urn, the sample must be homogeneous. Solid samples must be presented to the X-ray beam with a flat surface. However, the relative ease of sample preparation and the ability to run glasses and solutions with only minor dilution make X-ray fluorescence a useful technique where analysis for a wide range of impurities is required,... 

The proportionality constants Sj for the various elements are called the sensitivity coefficients of the XRF spectrometer for determination of these elements (expressed in counts s (g/cm ) ) and are important figures-of-merit of the instrument. In Fig. 11.9, the variation with atomic number of the sensitivity of a... 

In typical X-ray tubes employed in XRF spectrometers, accelerating voltages of 25—50 kV are used, while electron currents in the range 20-50 mA are employed. 

Fig. 11.17 Schematic drawing of a waveiength-dispersive XRF spectrometer (adapted from [12]).

Qualitative analysis is, in principle, very simple with XRF and is based on the accurate measurement of the energy, or wavelength, of the fluorescent lines observed. Since many WD-XRF spectrometers operate sequentially, a 20 scan needs to be performed. The identification of trace constituents in a sample can sometimes be complicated by the presence of higher order reflections or satellite lines from major elements. With energy-dispersive XRF, the entire X-ray spectrum is acquired simultaneously. The identification of the peaks, however, is rendered difficult by the comparatively low resolution of the ED detector. In qualitative analysis programs, the process is simplified by overplotting so called KLM markers onto... 

Energy Dispersive (ED) or Wavelength Dispersive (WD) XRF spectrometer 15,000-150,000 Very common... 

All three types can be found in use in cement works control laboratories, but the preferred system is the multichannel type fitted with channels for the simultaneous determination of the eight elements Fe, Ca, K, S, Si, Al, Mg, and Na. Depending on the local geology, a chaimel for the determination of fluorine may be fitted if the limestone deposit is close to a source of fluorspar (CaF2). (The determination of fluorine is beyond the scope of an energy-dispersive XRF spectrometer.) At some works a channel is added to monitor the chlorine content of the clinker, which can be introduced from the fuel used to fire the kiln. 

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