Electron-probe X-ray microanalysis

Electron Probe X-Ray Microanalysis (EPMA) is a spatially resolved, quantitative elemental analysis technique based on the generation of characteristic X rays by a focused beam of energetic electrons. EPMA is used to measure the concentrations of elements (beryllium to the actinides) at levels as low as 100 parts per million (ppm) and to determine lateral distributions by mapping. The modern EPMA instrument consists of several key components ... 

I. Bondarenko, H. Van Malderen, B. Treiger, P. Van Espen and R. Van Grieken, Hierarchical cluster analysis with stopping rules built on Akaike s information criterion for aerosol particle classification based on electron probe X-ray microanalysis. Chemom. Intell. Lab. Syst., 22 (1994) 87-95. 

W. Van Borm, Source Apportionment of Atmospheric Particles by Electron Probe X-ray Microanalysis and Receptor Models. Doctoral Thesis, University of Antwerp, 1989. 

Diffuse reflectance infrared Fourier transform spectroscopy deuterium triglycine sulphate energy compensated atom probe energy dispersive analysis energy-loss near edge structure electron probe X-ray microanalysis elastic recoil detection analysis (see also FreS) electron spectroscopy for chemical analysis extended energy-loss fine structure field emission gun focused ion beam field ion microscope... 

The primary methods of analyzing for lead in environmental samples are AAS, GFAAS, ASV, ICP/AES, and XRFS (Lima et al. 1995). Less commonly employed techniques include ICP/MS, gas chromato-graphy/photoionization detector (GC/PID), IDMS, DPASV, electron probe X-ray microanalysis (EPXMA), and laser microprobe mass analysis (LAMMA). The use of ICP/MS will become more routine in the future because of the sensitivity and specificity of the technique. ICP/MS is generally 3 orders of magnitude more sensitive than ICP/AES (Al-Rashdan et al. 1991). Chromatography (GC,... 

With some exceptions (2-4), there have been relatively few recent reviews of microanalysis that have considered applications to plant science. In a previous review of this topic (5), I concentrated almost entirely on methods of specimen preparation for electron probe X-ray microanalysis. Here I highlight further developments in this area, and also broaden the scope of the review to include other microanalytical techniques. This chapter introduces the main types of hardware that are now available for microanalysis, reviews the main techniques used to prepare plant material prior to analysis, and provides protocols for the two major techniques. 

There is little doubt that cryotechniques, and particularly cryo-SEM, are now the dominant methods of specimen preparation for electron probe X-ray microanalysis when localization of soluble ions is required. In a previous review (5) these techniques were covered in considerable detail and this material is not reiterated here. Instead, protocols for the two major methods are provided and some recent developments and publications in this area are highlighted. 

Nishihara, T. Kondo, M. Nonaka, T. Higashi, Y. Location of calcium and phosphorus in ashed spores of Bacillus megaterium determined electron probe X-ray microanalysis. Microbiol. Immunol. 1982, 26, 167-172. 

X-ray microanalysis techniques— in particular, electron probe x-ray microanalysis (EPXMA or EPMA) and SEM coupled with energy dispersive spectrometers (EDS, EDX) are, by far, one of the surface analysis techniques most extensively used in the field of art and art conservation, and they have actually become routine methods of analyzing art and archaeological objects and monitoring conservation treatments [34, 61, 63]. 

High-resolution compositional measurements are possible through use of a variety of microanalytical methods. Ideally, these should be non-destructive, can be targeted on small areas of sample, and have low minimum detection limits. Electron-probe X-ray microanalysis (EPXMA) and proton-induced X-ray emission (PIXE) techniques have both been used successfully on archaeological sediment thin sections (19, 20). Both techniques yield elemental composition data for a range of elements. EPXMA has the advantage of being nondestructive, whereas PIXE when used on thin-section samples is typically destructive conversely the detection limit for PIXE is lower than EPXMA. 

Freudenrich CC, Hockett D, Ingram P, LeFurgey A. In situ cryofixation of kidney for electron probe X-ray microanalysis. J. Struct. Biol. 1994 112 173-182. 

The particles were deposited on the slides by in5>actation, sedimentation and diffusion. Subsequently, the samples were analyzed by scanning electron microscopy (SEM). Information on morphology and size distribution was obtained from image analysis, while the elemental composition of particles was determined by electron probe X-ray microanalysis (EPXMA). 

In general, the stores are loaded with Ca + buffered with millimolar concentrations of EGTA (Endo et al., 1977 Saida and Nonomura, 1978 Itoh et al., 1982a,b Saida, 1982). The stores are fully loaded within 3 to 5 min at 1 (jlM Ca2+ (Saida, 1982), whereby the Ca2+ uptake depends on the Ca + concentration (Saida, 1982 Yamamoto and van Breemen, 1986). At Ca + concentrations greater than 1 jlM, a Ca +-induced Ca release was observed (Itoh et al., 1981 Saida, 1982). The deposition of Ca2+ in the SR of saponin-permeabilized smooth muscle was demonstrated by electron probe X-ray microanalysis (Kowasaki et al.,... 

Microprobe techniques, and their detection limits (given in mgkg ), that have been applied to Al localization include energy dispersive (electron probe) X-ray microanalysis (20), wavelength-dispersive X-ray microanalysis, electron energy loss spectrometry (500), proton probe nuclear microscopy (10), resonance ionization mass spectrometry (3), secondary ion mass spectrometry (1), laser microprobe mass spectrometry (1) and micropartide-induced X-ray emission (Yokel 2000). 

X-ray fluorescence is associated with the K-shell electrons of metals. A thin film of the sample containing metals is placed on a small mylar sheet and dried. The sample is then bombarded with an electron beam and when an incident electron interacts with a K-shell electron in the metal, the K-shell electron Is elevated to an unstable orbital state. As the K-shell electron returns to its stable orbital, it emits energy in the form of X-rays which are characteristic of the metal involved. These X-rays can be counted by an appropriate detector and the energies of the X-rays correspond to different metals. Even though this method Is very specific and capable of measuring aluminium, it does not appear to be sensitive enough in its present state to detect the trace leveis of aluminium in serum (Sorenson et al., 1974). However, one form of X-ray emission spectrography, that of electron probe X-ray microanalysis, has been used effectively to localize aluminium in both bone and brain tissues (Smith and McClure, 1982). Localization of aluminium in tissues will be discussed briefly In a later section. 

Ro C-U, Oh K-Y, Kim H, Chun Y-S, Osan J, de Hoog J, Van Grieken R (2001) Chemical speciation of individual atmospheric particles using low-Z electron probe X-ray microanalysis characterizing Asian Dust deposited with rainwater in Seoul. Kraea Atmos Environ 35 4995-5005... 

Ro C-U, Kim H, Van Grieken R (2004) An expert system for chemical speciation of individual particles using low-Z particle electron probe X-ray microanalysis data. Anal Chem 76 1322-... 

Ro C-U, Hwang HJ, Kim HK, Chun YS, Van Grieken R (2005) Single-paiticle characterization of four asian dust samples collected in korea, using low-Z particle electron probe X-ray microanalysis. Environ Sci Technol 39 1409-1419 Salma I, Weidinger T, Maenhaut W (2007) Time-resolved mass concentration, composition and sources of aerosol particles in a metropolitan underground railway station. Atmos Environ 41 8391-8405... 

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