EDXRF Spectrometers

The elemental composition of unknown materials such as engine deposits can be determined qualitatively and the information used to develop dissolution methods prior to analysis by inductively coupled plasma atomic emission spectroscopy (ICPAES). Alternatively, a semi-quantitative analysis can be provided by XRF alone, especially important when only a limited quantity of sample is available and needed for subsequent tests. The deposit does not even have to be removed from the piston since large objects can be placed directly inside an EDXRF spectrometer. 

Figure 12.10 EDXRF. Spectrometer containing a low power X-ray tube, as an example of numerous models of this type (model EX-3 lOS reproduced courtesy of Jordan Valley). A typical spectrum obtained with such an instrument (reproduced courtesy of Amptek Inc. USA).

With proper correction for matrix effects. X-ray fluorescence spectrometry is one of the most powerful tools available for the rapid quantitative determination of all but the lightest elements in complex samples. For example. Rose, Bornhorst. and Sivonon have demonstrated that twenty-two elements can bo determined in powdered rock samples with a commercial EDXRF spectrometer in about 2 hours (1 hour instrument time), including grinding and pellet preparation. Relative standard deviations for the method are better than 1% for major elements and better than y/o for trace elements. Accuracy and detection limits as determined by comparison to results from international standard rock samples were comparable or better than other published procedures. For an e.xcellent overview of XRF analysis of geological materials, see the paper by Anzelmo and Lindsay. ... 

FIG. 2—Calibration graphs for suljur obtained on two Afferent spectrometers. The upper curve (squares) is achieved on a high-power WDXRF instrument, while the lower curve is achieved on a benchtop EDXRF spectrometer. 

Besides EDXRF spectrometers that are intended for use in the laboratory, a number of portable EDXRF instruments are also available. These devices are used in various fields for on-site analysis of works of art, environmental samples, forensic medicine, industrial products and waste materials etc. In their simplest form, the instraments consist of one or more radioisotope sources combined with a scintillation or gas proportional counter. However, combinations of radio-sources with ther-moelectronically cooled soHd-state detectors are also available in compact and lightweight packages (below 1 kg). In Fig. 11.21, schematics of various types of radiosource based EDXRF spectrometers are shown. In Fig. 11.21a, the X-ray source is present in the form of a ring radiation from the ring irradiates the sample from below while the fluorescent radiation is efficiently detected by a solid-state detector positioned at the central axis. Shielding prevents radiation from the source from entering the detector. In Fig. 11.21b and c, the X-ray source has another... 

Figure 20.3 shows results obtained with a Spectro X-Lab EDXRF spectrometer utilising this approach for samples with light element concentrations (loss on ignition) up 57 % m/m. Accuracy for the major elements is generally similar to that... 

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. 

Some manufacturers of EDXRF spectrometers (e.g., Horiba, Jorden Valley, Rigaku, Shimadzu Scientific Instruments, Oxford Instruments, etc.) have developed X-ray analytical microscopes for imaging which include CCD camera, focused X-Ray system, and a vacuum Fluorescent X-Ray probe. These spectrometers allow measurements on spot sizes as small as 10 microns on samples as small as 512 microns square or up to 100 mm square. These spectrometers are being used in fields as diverse as electronics, medicine, food, cosmetics, life science, plastics and alloy analysis, provide elemental mapping of a number of elements simultaneously in a wide variety of sample types. 

Fig. 1.23. Background contribution in the EDXRF spectrometer with monochromatic excitation at 17.4 keV...

Wolska [59] reviewed recent advances in the application of XRF spectroscopy to the determination of antimony, bromine, copper, iron, phosphorus, titanium, and zinc, in various plastics. The ED2000 high-performance EDXRF spectrometer mannfactured by Oxford Instruments can determine up to 80 elements qualitatively and up to 50 elements quantitatively between sodium and uranium in various materials, including polymers [60]. X-ray fluorescence methods are available for the determination of tin stabilisers in PVC [61, 62]. 

This EDXRF system SPECTRO XEPOS ntilises proprietary polarisation technology to improve the limits of detection for individnal elements by a factor of 4-7 compared to conventional EDXRF spectrometers. With XEPOS the average detection limit achieved for cadminm, for example, for measnrements on ground polymer samples is 8 ppm, comfortably below the 100 ppm limit set by the ELV directive. 

Figure 9. On-site determination of waste enclosure in u Hood plain area in neighbourhood of a landfill site by using transportable EDXRF spectrometer (sampling by digging in the depth, waste contamination in profile I)...

As shown in Figure I2-I.5a, an EDXRF spectrometer consists of a polychromatic source—which may be either an X-ray lube or a radioactive material — a sample holder, a semiconductor detector, and the various electronic components required for energy discrimination."... 

Wolska [60] has reviewed recent advances in the application of XRF spectroscopy to the determination of antimony, bromine, copper, iron, phosphorus, titanium, and zinc, in various plastics. The new ED2000 high-performance EDXRF spectrometer... 

Figure 2 Spectrum of lichen sample. Pressed pellet, measured with a standard EDXRF spectrometer, Rh tube 30 kV, 0.2 mA, 500 s, Pd filter, Si(Li) detector concentration values of respective elements given in rg g"h...

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