X-ray microanalysis technique

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]. 

Scanning electron x-ray microanalysis techniques reveal that metal deposits are frequently nonuniform through the catalyst pellet cross section after demetallation reactions. Metal profiles measured after HDM studies with Ni and VO-etioporphyrin (Agrawal and Wei, 1984), Ni-tetra(3-methylphenyl)porphyrin (Ware and Wei 1985a), and VO-tetraphenyl porphyrin (West, 1984) demonstrate the inhomogeneity. Examples in... 

Keszthelyi et al. (1981) applied x-ray microanalysis technique to the study of a B-Z-type reaction of (HN03/KBr03/[Fe(phe)3+]/malonic acid system). However such a technique requiring a dyring process may result in interpretations based on somewhat altered structures. 

DTA, TG, IR, and X-ray microanalysis techniques were applied to identify the materials that formed around the rim of sandstone or silt stone aggregate in a thirty-year old concrete.An alkali-substituted okenite (C5 S9H9), a precursor phase characterized by a 1.22 nm XRD spacing, was identified. 

METHODICAL TECHNIQUES FOR RESEARCH OF RARE-METAL AND RARE-EARTH MINERALS WITH X-RAY MICROANALYSIS... 

J. I. Goldstein, Dale E. Newbury, P. Echlin, D. C. Joy, C. Fiori, and E. Lif-shin. Scanning Microscopy and X-Ray Microanalysis. Plenum Press, New York, 1981. An excellent and widely ranging introductory textbook on scanning microscopy and related techniques. Some biological applications are also discussed. 

High Resolution Transmission Electron Microscopy and Associated Techniques. (P. R. Buseck, J. M. Cowley, and L. Eyring, eds.) Oxford University Press, New York, 1988. A review covering these techniques in detail (except X-ray microanalysis) including extensive material on high-resolution TEM. 

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 ... 

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,... 

Sigee DC. X-ray Microanalysis in Biology Experimental Techniques and Applications, Cambridge University Press, Cambridge, UK, 1993. 

Microanalytical techniques were first pioneered in the 1960s, and the earliest paper using X-ray microanalysis on plant materials is that of Lauchli and Schwander in 1966 (1). It was soon realized that microanalysis could provide a link between anatomical studies and plant physiology. It allowed scientists who were interested in aspects of plant mineral relations to pursue their interests at a cellular or even subcellular level. Microanalysis, in its various forms, is now a well-established technique, and one that is continuing to develop. 

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. 

Other recently developed techniques, such as immunoelectron microscopy (Chapter 18), electron systems imaging, and X-ray microanalysis (Chapter 19), should become routine practice in most EM laboratories and, thus, mainstays rather than ancillary EM methods. 

Verita, M., Basso, R., Wypyski, M.T. and Koestler, R.J. (1994). X-ray microanalysis of ancient glassy materials a comparative study of wavelength dispersive and energy dispersive techniques. Archaeometry 36 241-251. 

Electron microscopy is an efficient microscopy technique that has been extensively used for the material characterization of artistic and archaeological objects, especially in combination with x-ray microanalysis [54], The use of electrons instead of light in these instruments is the basis of the higher resolution ( 9-0.2 nm) and has greater depth of held than LM. Thus, characterization of the finest topography of the surface objects is possible, and additional analytical information can be obtained. Different electron microscopes are currently used in art and art conservation studies scanning electron microscopes (SEM), Cryo-SEM... 

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. 

Analysis schemes developed for identifying clay minerals in the TEM based on EDS spectra (e.g., Murdoch et al.100) are inappropriate for colloidal samples dispersed on polycarbonate filters due to complications associated with the various sample-beam-substrate interactions that differ dramatically from that of ideal samples or standards with smooth polished surfaces.94 96 101 102 Correction procedures that account for the influence of particle size and morphology on x-ray spectra have been widely available for some time,101102 but these techniques have not been applied to the analysis of environmental particulates. To overcome the limitation of quantitative elemental analysis, some research groups have compared the x-ray spectra for sample colloids to the spectra for various minerals of similar size and composition under the same instrumental and sample preparation conditions to calibrate instrumental response.7 24 93 Noting the resolution problems associated with SEM analysis of submicron colloids, several research groups have chosen TEM as the primary discrete particle analysis technique,21 52 103 104 or have combined TEM analysis techniques, such as electron diffraction and x-ray microanalysis, to confirm conclusions drawn from SEM surveys.7,93 105... 

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