A WDS ‘wavelength scan’ from a grain of anorthoclase feldspar ((Na,K,Sr,Ba)AlSi3O8) centered about the Si peak position is shown to the left.  Six peaks from 3 different elements can be resolved:  Si, Sr, and K. The horizontal arrowed line illustrates the width of the Si peak from an EDS spectrum. None of the minor peaks shown on the WDS scan are resolvable via EDS.  Importantly, it is not possible to determine the concentration of the geologically important element Sr in a silicate mineral using EDS because of the much poorer spectral resolution of EDS.  Additionally, the minimum detection limit in WDS is much lower (10’s of ppms depending on the element and analytical conditions) compared to >2000ppm via EDS. 

 

WDS is the method of choice for most all of the quantitative analyses we do.