Elemental Analysis

SEM-EDS

In the scanning electron microscope, electrons interacting with samples cause x-rays to be generated from the atoms present.  These x-rays have varying energy depending on the element it came from.  Once these x-rays are seen on a silicon detector, amplified, and passed through a multichemical analyzer, the elements can be identified and semiquantified.  The elements are essentially identified based on the energies of the x-rays which are emitted from the sample.  This is a powerful analytical tool as it can detect most of the elements in the periodic table above an atomic number of 4.  Detection limits are in the low percentage range.  The method is a surface analytical procedure but particles imbedded in a plastic matrix can be exposed by micro surgical techniques and cross-sectioning.

Zaf Corrections:

Specific factors related to specimen (sample) composition (called matrix effects) can affect the X-Ray spectrum developed in an electron microprobe analysis and may have to be corrected for if a precise analysis needs to be performed.  These matrix corrections are known as Zaf corrections, referring to the three parts of matrix effects - the atomic number (Z), absorption (A), and fluorescence (F).