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Trace Elements

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Trace Elements
  Electron probe microanalysisEPMA Trace Element Analysis Mod 1/10/2016  What ’ s the point? What ’ s the minimum detection limit for a  particular element  –  or said otherwise, at what  point can be be sure that a small inflection above the surrounding background really is a peak? What kind of confidence level should be place on such a number?  Definitions “ Generally, WDS can achieve limits of detection of 100 ppm in favorable cases, with 10 ppm in ideal situations where there are no peak interferences and negligible matrix absorption. ” (Goldstein et al., p. 341) Major>10 wt%Minor 1-10 wt%Trace <1 wt%   No   Zn ... but at what level of confidence?  Trace elements .... and trace elements In the real world, the definition of “ trace element analysis ” is sometimes broader than the strict quantitative analysis of ppm level elements in one microvolume (~micron interaction volume). Many individuals desire to use EPMA to tell them about the “ distribution of trace elements ” in their materials, e.g. where the 30 ppm of Pb is in a cast iron. There are two possibilities: the 30 ppm is spread uniformly throughout the material, or in fact most of the material has probably <1 ppm of Pb, but a small fraction of the volume has phases that have Pb at major element levels.The question is then, are they at least the size of the interaction volume and if so, where are they. Our discussion here will deal with all these aspects.
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