Electron probe microanalyze microanalysis

A beam of electrons striking a target results in the emission of characteristic X-rays. This is the basis of the X-ray tube, as was discussed earlier in the chapter. A beam of electrons striking a sample will also generate characteristic X-rays from the sample. The use of a small diameter electron beam, on the order of 0.1 -1.0 p,m, to excite a sample is the basis of electron probe microanalysis. An electron probe microanalyzer is an X-ray emission spectrometer. The small diameter electron beam excites an area of the surface of the sample that is about 1 pm in diameter. Elemental composition and variation of composition on a microscopic scale can be obtained. 

The earliest commercially available X-ray spectrometer appeared on the market in 1938. Ten years later, Friedman and Birks built the prototype of the first commercial X-ray secondary emission instrument. Somewhat later, Castaing and Guinier built the first electron probe microanalyzer using a focused electron beam to induce X-ray emission of the elements present in microscopic samples using electron probe X-ray microanalysis (EPXMA). The use of protons in PIXE for chemical analysis was first demonstrated by Sterk in 1964. From the 1960s until the present day, the use of large-particle accelerators (synchrotron rings) has resulted in a dramatic... 

Cooke, C. J. and Duncumb, P. 1969. Performance analysis of a combined electrmi microscope and electron probe microanalyzer, EMMA. hiFifth International Congress onX-Ray Optics and Microanalysis (Mollenstedt, G. andGaukler, K. H., eds.). Springer-Verlag, Berlin. Pp. 

The limitations in sensitivity and in depth resolution of the electron-probe microanalyzer prompted the development of ion-probe microanalysis. This technique is based on mass spectro-graphic analysis of the secondary ions emitted from a sample under the impact of a focused and accelerated primary ion beam. This type of analysis also offers, in comparison with the electron probe, the possibilities of isotopic analysis and the investigation of elements of low atomic number, including hydrogen, at trace concentrations. 

EPMA Electron probe microanalysis, electron probe microanalyzer... 

The microanalyzer has been applied to biological materials (Cl, D18), including the analysis of cell fractions (A6), measurement of titanium and zinc (10 -10 atoms/eejl) in leukocjrtes (C8), fluorine in teeth (W7), and calcium, phosphorus, and magnesium in small urinary calculi (CIO). If electron probe microanalysis becomes a routine tool, it is unlikely to be located in clinical chemistry. 

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