Standardized EDS Analysis
as of 11/4/2013
by Dave Hirsch, based on work by Aiden Brehan, 2010-2013
Initial Settings:
Standardized EDAX analysis of minerals requires that in the same session you are able to
analyze both a mineral standard and the unknown in question. An apparatus has been fabricated for
Western’s SEM to hold both the “standard block” and whatever unknown sample you are trying to
analyze. Before inserting both into the SEM, make sure that both are clean and properly coated for
20 seconds with Au-Pd. Next, make sure that the stage has been calibrated and insert the holder
apparatus into the center slot. Align the long edge of the standard block perpendicular to the edge
of the SEM chamber door. Doing this ensures that all standards will be within the scanning range
(40mm x 40 mm square) of the SEM instrument. Tighten the small allen screw at the post of the
apparatus. Pump down the instrument according to procedure.
Once the instrument has been pumped down, select a grain to use as a standard (it should be as
similar to the unknown as possible, while containing all the elements needed to be analyzed), and
manually adjust the focus of the beam using a WD (Working Distance) from 22-23mm. When the
image is best in focus, double click to create a red selection box and select a section of standard
grain you wish to use. A good section of a grain will show a uniform hue in the BSE image. This hue
should be somewhat consistent throughout the grain; it is an analog for the composition of the
grain.
Observe the readings in the lower left-hand corner of the EDAX Genesis window labeled CPS and
DT%. The ultimate goal for standardized analysis is to gain a CPS between 1000 and 2000 and a
DT% of 20-35. Depending on the behavior of the tungsten filament that creates the electron beam,
different settings will create these readings. Attaining this target reading can normally be done
within this range of settings:
Vega TC settings:




WD (Working Distance) of 22-24mm
PC (Probe Current) of 6 to 8 depending on the scope’s mood at that particular moment.
20 or 15 kV
Slight adjustment of “Heating” (maximum 3-5%) in some cases for fine-tuning.
EDAX Genesis settings:

Select various Amp Times (top right corner, usually 102.4µs)
Once you have attained these readings, allow a couple minutes for the readings to become
consistent. Consistent readings should show fluctuations for CPS of about 100 and 2-5 % for DT%.
Both should remain in this same range for the duration of the reading.
Select “MEMORY” then “A” in the Stage Control window to commit this section of this standard
grain to memory for further use.
Analysis of Standard:
Once optimal settings and stable CPS and DT% readings have been attained, select a 500 second
count time from the top right corner of the EDAX menu. Hit collect and allow the 500 second count
time to run. Once the count has elapsed, identify all elements prominent in the standard.
To enter standard data, maximize the QUANT menu on the right hand side of the EDAX genesis
window. Select ZAF list, then select all elements you have standard data for in the window that
appears. If a warning appears, select ok. Next select the STD button. In the window that appears,
select the bubbles labeled “Compound” and “element” then select the button SETUP. In the sub
window below this button you will see all of the elements you labeled in your spectrum. Select each
one and enter the wt.% of each element in your standard (see appendix below). Once you have
entered all this data, select the button labeled RZAF, check the box for “use as compound” and hit
ok. Make sure the values you entered are correct and select OK. You should be back to normal view
now and your spectrum will have a blue outline.
Analysis of Unknown:
Once you have attained a spectrum of the standard, find the unknown that you wish to analyze.
Using the same criteria as before with the analysis of the standard, obtain a selection box of a
satisfactory section of the unknown. As opposed to the analysis of the standard, use a small box for
a specific section of the unknown. Make sure that the settings remain the same as for the Standard.
Scanning in a different section of the analysis window may also generate different CPS and DT%
values. It is most important that these values remain similar for both the standard analysis and
unknown analysis. Once you have attained reasonably stable agreement between the standard and
unknown CPS and DT% readings, hit “COLLECT” for the same count time used for the standard
(most likely 500 sec). Allow this time to elapse. Once it has, you are ready to quantify your results.
Be sure your analysis Type is set to “Oxy By Diff” (right-click on the text next to the QUANT
button), then hit QUANT on the right hand side of the EDAX Genesis window and you should see a
new window with quantified values for the composition of the unknown based on the known
composition of the analyzed standard. Save the spectrum and values to a PDF file by choosing to
Print both, then choosing the PDF printer out of the list.
Accuracy and Precision:
[Under construction, but Aiden found uncertainties in the range of 5% relative]
Appendix I: Standard Locations
A-1
B-1
C-1
A-2
B-2
C-2
A-3
B-3
C-3
A-4
B-4
C-4
A-5
B-5
C-5
A-6
B-6
C-6
A-7
B-7
C-7
A-8
B-8
C-8
A-9
B-9
C-9
A-10
B-10
C-10
Standard
Anorthite
Anorthoclase
Apatite
Augite
Augite (Cr)
Diopside
Dolomite
Gahnite
Garnet
Hornblende
Olivine
Siderite
Strontianite
Zircon
Glass A-99
Glass A
Glass B
Glass C
Glass D
Glass, IR-V
Glass, IR-W
Glass, IR-X
Glass, Rhyolitic
Reference #
NMNH 137041
NMNH 133868
NMNH 104021
NMNH 122142
NMNH 164905
NMNH 117733
NMNH 10057
NMNH 145883
NMNH 87375
NMNH 143965
NMNH 111312/444
NMNH R4260
NMNH R10065
NMNH 117288-3
NMNH 113498-1
USNM 117218-4
NMNH 117248-1
NMNH 117218-2
USNM 117218-3
USNM 117083
NMNH 117084
NMNH 117085
USNM 72854,VG568
Comments
Very fine
Table 1: Location, name and reference number of each mineral with comments pertinent to
successful application of each standard. Standard block is catalogued as columns A, B and C from
left to right. From the bottom (end with no empty holes) rows are numbered 1, 2, 3, 4, etc.