EDXRF

ELEMENT PROFILE OF TABACO PLANTS AFTER THE TREATMENT WITH HETEROPOLY COMPOUNDS WITH ANTIVIRAL ACTIVITY INVESTIGATED BY EDXRF SPECTROMETRY... 

EDXRF vs. WDXRF, sequential vs. simultaneous XRF), geometry (TXRF, SEXAFS, glancing angle), theoretical interpretations (EXAFS, XANES), microanalysis ( xXRF, EPMA), hyphenation or on-line analysis. There is sufficient scope for polymer/additive analysis by means of XRS tools. 

The basic function of the spectrometer is to separate the polychromatic beam of radiation coming from the specimen in order that the intensities of each individual characteristic line can be measured. In principle, the wide variety of instruments (WDXRF and EDXRF types) differ only in the type of source used for excitation, the number of elements which they are able to measure at one time and the speed of data collection. Detectors commonly employed in X-ray spectrometers are usually either a gas-flow proportional counter for heavier elements/soft X-rays (useful range E < 6keV 1.5-50 A), a scintillation counter for lighter elements/hard X-rays (E > 6keV 0.2-2 A) or a solid-state detector (0.5-8 A). 

Table 8.39 shows the main features of EDXRF. EDXRF is not able to detect the fine structure of the K, L, M, etc. lines. EDXRF is used for applications which require measurement of a limited number of elements, and where the resolution and ultralow detection limits of wavelength-dispersive systems are not necessary. For example, EDXRF has been used as a rapid screening technique for the determination of Br and Sb in plastic recyclate at a LOD of 5 ppm [230] the method was validated by means of NAA [231]. Conventional EDXRF systems and benchtop units have a limited detection capability for low-Z-elements and cannot directly measure fluorine in processing aids. 

In EDXRF, trends are for miniaturisation, development and optimisation of high-resolution room-temperature detectors and extension of the application range towards the determination of light elements. 

Table 8.39 Main features of energy-dispersive X-ray fluorescence spectrometry (EDXRF)...

Table 8.40 compares the main characteristics of WDXRF and EDXRF. Multidispersive XRF combines the benefits of the WDXRF technique for routine elemental analysis with the complete flexibility offered by EDXRF for nonroutine analysis. Clearly, modem XRF instrumentation is rather varied, ranging from simple benchtop EDXRF equipped with a low-power X-ray tube and high-resolution proportional counter for some key elements, to 4 kW simultaneous multichannel spectrometers with 28 fixed element channels for... 

Both WDXRF and EDXRF lend themselves admirably to quantitative analysis, since there is a relationship between the wavelength or energy of a characteristic X-ray photon and the atomic number of the element from which the characteristic emission line occurs. The fluorescence intensity of a given element is proportional to the weight fraction. Emitted fluorescence radiation is partly absorbed by the matrix, depending on the total mass absorption coefficient ... 

International or in-house standards in combination with fundamental parameters software, lead to the same accuracy as conventional analysis using regression analysis of standards. Provided that accurate standards are available, the main factors that determine the accuracy of XRF are the matrix absorption correction and (in the case of EDXRF) the spectrum evaluation programme, i.e. correction for spectral overlap and background. 

The literature on XRF is abundant. Recent general reviews are refs [235,237] for sample preparation see ref. [247]. EDXRF was specifically dealt with in ref. [248] and an excellent X-ray detector overview is available [225]. Several recent XRF monographs have appeared [233,249,249a], also covering TXRF [250] and quantitative XRF [232,251]. 

Due to the different working principles of WDXRF and EDXRF, the applications differ strongly (Table 8.43). Simultaneous WDXRF with ten channels (elements) and increased sensitivity for the low atomic number elements (e.g. a few ppm of phosphorous in a low atomic number matrix) has been used for QC of polymer granules [252], To detect elements at trace levels (ppm-ppt), generally the special XRF modes, mainly EDXRF techniques, are applied like TXRF, SR-XRF or pXRF. Detection limits with SR-XRF are now at the attogram level. 

EDXRF has been used for comparison of the elemental composition of some 100 carpet fibres (both automotive and residential) for forensic source classification [260]. SEM-EDS is too insensitive for this... 

Table 8.47 shows the available options for the analysis of polymer processing aids, namely combustion and instrumental methods. The best method is dependent on PPA type, the level to be measured, and the available equipment (see also Section 8.2.1.2). Fluoropolymer processing aid concentrations can be determined by WDXRF configured to measure either fluorine or a tracer, and by EDXRF to analyse a tracer [29]. Calibration curves are required. At present, EDXRF or benchtop XRF units cannot directly measure fluorine. For resin or masterbatch producers who prefer to make on-line XRF measurements of processing aid concentrations (to letdown levels of 50-100 ppm), processing aids that contain a tracer (usually BaS04) are available. The analysis time is less than two minutes. 

PIXE has been compared to other focusing X-ray beam techniques [292]. Although the measurement part of PIXE and EDXRF is exactly the same, the spectra... 

Lee et al. [451] have described procedures to overcome several practical problems in the analysis of plastics by NAA more than 30 elements were analysed in eight PE and six PP materials in the range of sub-ppb to per cent. Table 8.73 shows the close correspondence of the results for quantitative determination of Mg in PP by means of NAA and LA-ICP-MS [465]. Also, a comparison of NAA and EDXRF for the determination of Ba, Cr, Fe and Ti in polycarbonate was reported [465a]. 

DPP Differential pulse polarography EDXRF Energy-dispersive... 

F. Clarke, A. Whitley, S. Mamedov, F. Adar, N. Lewis and E. Lee, A comparison of Raman and EDXRF chemical imaging for use in formulation process development and quality control, Newsletters, Raman Update (Horiba Jobin Yvon), Spring, 2005. 

Fluorescence, 3 256 22 716. See also EDXRF instruments Micro X-ray fluorescence (MXRF) analysis Total reflection X-ray fluorescence spectrometry micro X-ray, 26 437-439 Raman scattering and, 21 324, 325 sensors using, 22 271... 

Portable EDXRF instruments, 26 442 Portable scales, 26 244 Porter equation, 15 724 Portimicin, 20 137 Portland cement, 4 583... 

In an EDXRF system, the two tasks of energy measurement and detection are carried out simultaneously. In a WDXRF system, on the other hand, the... 

---