Microanalysis
WDS X-Ray Mapping Overview
The output between ED and WD mapping is the same. WD permits X-ray line separation and better sensitivity to low concentrations.
We use two different programs to acquire WD and ED maps. dPict32 is used for WD mapping and, near the end of the procedure, looks very much like image acquisition. In the initial steps of WD mapping, you are required to perform a short subset of the WDS Quantitative Analysis Procedure under JEOL JSM-6400 SEM. Briefly, in these steps you will position the spectrometers to the peak (highest intensity) of the element. At that point dPict32 will couple that X-ray signal with the scanning hardware.
When to Map using WDS
WD mapping is needed only if:
- There are low concentration elements in your sample, or
- There are peak overlaps. For the case of peak overlaps occurring in ED, both overlapped elements will be depicted as the same in the map.
PbS Spectrum in EDS |
Pb Peak in WDS |
S Peak in WDS |
As always, perform an EDS analysis first if you do not know all the element constituents. EDS also indicates the presence of peak overlaps.
Standards
If you know what elements are present and that all elements are in a concentration above 10% wt, you can peak the WD spectrometers using only your sample. In that case, ignore any instructions in WDS X-Ray Mapping Procedure under JEOL JSM-6400 SEM that involve the use of a standard.
If you know what elements are present but one of the elements is in a low concentration, then use a standard for that element. The WD spectrometers must be peaked for that element using a standard first, otherwise that element will not be counted accurately. Follow any instructions in the mapping procedure that involve the use of a standard.
