マイクロプローブ分析のための標準物質
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概要
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Standards for quantitative electron-probe analysis of geochemical samples have been evaluated in the light of recent advances in hardware technology and data reduction system. Energy dispersive type electron-probe has merits that command wide variety of standards. 200 pA electron beam scanned in a small region yields stable X-ray intensities on such weak materials as potassium dichromate, calcium carbonate and gallium phosphide. These are excellent 'standards for K, Ca and P, respectively. Energy shifts measured between metal and oxide for Al, Si and Fe are less than 1 eV. This means that the use of metals does not cause analytical errors. Wavelength dispersive electron-probe likewise can employ metal standards owing to the computer-assisted peak positionning for both standards and unknowns. Pure metals and simple oxides together cannot cover whole elements of geochemical interest. Natural minerals are complementary standards, but are inevitably heterogeneous to some extent. X-ray intensities on a spot of almost pure natural minerals measured by EDS or automated WDS combined with assumed stoichiometry give rise to independent estimates of chemical compositions. This is particularly useful for albite, jadeite, pyrite, K-feldspar and wollastonite. Thus, electron-probe analysis can now be independent of other analytical methods. Error evaluation attests that even EDS analysis can be as good as the conventional chemical analysis. The use of pure metal standards demonstrates variation of characteristic X-ray intensity in a wide energy range. When no metals are available, the compound standards can yield, by ZAF correction method, intensities for simple substances. Both sets of intensity data fit each other, and show X-ray generation-detection efficiency . This knowledge leads to quantitative analysis of elements for which no standards are available, and will in future enable entirely standardless electron-probe analysis.
- 特定非営利活動法人日本火山学会の論文
- 1983-10-01
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