Author Topic: Quantifying elements from EDS with PFE  (Read 2363 times)

SteveSeddio

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Quantifying elements from EDS with PFE
« on: December 16, 2016, 12:24:30 pm »
There seems to be some confusion regarding how PFE quantifies elements using EDS.
I've searched through the forum and not found a direct answer.
It is my understanding that PFE takes the net counts from "unknown" spectra and standard spectra from Pathfinder/NSS. That is to say that PFE takes the counts for the X-ray lines of the element of interest after Pathfinder/NSS accounts for sum peaks and escape peaks,  removes the background, and deconvolves any interference. Is this understanding correct?

Furthermore, does PFE rely on the factory peak shapes in Pathfinder/NSS for deconvolution of the spectrum for extracting net counts, or does PFE load standard reference shapes into Pathfinder/NSS so that user-acquired standard spectra are used for deconvolution?

Thanks!
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stephen.seddio@thermofisher.com

John Donovan

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Re: Quantifying elements from EDS with PFE
« Reply #1 on: December 17, 2016, 12:03:47 pm »
There seems to be some confusion regarding how PFE quantifies elements using EDS.
I've searched through the forum and not found a direct answer.
It is my understanding that PFE takes the net counts from "unknown" spectra and standard spectra from Pathfinder/NSS. That is to say that PFE takes the counts for the X-ray lines of the element of interest after Pathfinder/NSS accounts for sum peaks and escape peaks,  removes the background, and deconvolves any interference. Is this understanding correct?

Furthermore, does PFE rely on the factory peak shapes in Pathfinder/NSS for deconvolution of the spectrum for extracting net counts, or does PFE load standard reference shapes into Pathfinder/NSS so that user-acquired standard spectra are used for deconvolution?

Thanks!

Hi Steve,
No that is not correct.  PFE performs EDS quant just as WDS quant is performed. Specifically using a full k-ratio. That is, both EDS spectra on unknowns *and* standards are acquired, and PFE then sends the spectrum for the unknown *and* standard to Thermo (or Bruker) to obtain the net intensities on both, then constructs the k-ratio and then runs those EDS k-ratios through the quant (what ever it might be), along with the WDS k-ratios.

Because of this one obtains the most accurate quantification because each EDS element has a reference standard. In addition, we can also apply spectral interference corrections to both EDS and WDS elements (WDS by WDS, WDS by EDS, EDS by EDS and EDS by WDS!).

As for peak shape profiles, those can be defined in an NSS project and specified when PFE makes a connection to the EDS interface.  With Bruker one can specify a peak profile separately for each sample, while Thermo applies the peak profile on a per project basis.

So the bottom line is that PFE only utilizes the peak stripping routines in Thermo or Bruker EDS to obtain the net intensities.  The option to specify a Bruker "quant method" for dealing with peak shape fitting is shown here:

http://probesoftware.com/smf/index.php?topic=578.msg3305#msg3305

For Thermo, when one connects to the Thermo Portal Server, PFE asks:



See here for details:

http://probesoftware.com/smf/index.php?topic=482.msg2826#msg2826

and also here:

http://probesoftware.com/smf/index.php?topic=79.msg3005#msg3005

I've also attached our EDS-WDS PPT filpe that I presented in May at the Madison TC below (login to see attachments).
john
« Last Edit: December 17, 2016, 12:34:23 pm by John Donovan »
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SteveSeddio

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Re: Quantifying elements from EDS with PFE
« Reply #2 on: January 03, 2017, 11:14:28 am »
Thanks, John.

So, if a user wants net intensities to be calculated using reference shapes acquired on their system (opposed to the factory-defined shapes), they must specify User Defined Standardless References in NSS/Pathfinder and click the "Yes" button on the ThermoEDSSpectraInit window when they connect to the Thermo Portal Server. Otherwise, the net intensities will be calculated using the factory-defined reference spectra.
-Steve
Your friendly, neighborhood, EPMA-minded EDS guy.
stephen.seddio@thermofisher.com

John Donovan

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Re: Quantifying elements from EDS with PFE
« Reply #3 on: January 03, 2017, 12:23:17 pm »
Thanks, John.

So, if a user wants net intensities to be calculated using reference shapes acquired on their system (opposed to the factory-defined shapes), they must specify User Defined Standardless References in NSS/Pathfinder and click the "Yes" button on the ThermoEDSSpectraInit window when they connect to the Thermo Portal Server. Otherwise, the net intensities will be calculated using the factory-defined reference spectra.
-Steve

Hi Steve,
You tell me!

I only know that if you specify an NSS project in the PFE EDS initialization, I assume NSS will use whatever profiles are defined in the selected NSS project.   I'm not sure what specific parameters the NSS project contains...
john
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John Donovan

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Re: Quantifying elements from EDS with PFE
« Reply #4 on: January 03, 2017, 10:42:56 pm »
Thanks, John.

So, if a user wants net intensities to be calculated using reference shapes acquired on their system (opposed to the factory-defined shapes), they must specify User Defined Standardless References in NSS/Pathfinder and click the "Yes" button on the ThermoEDSSpectraInit window when they connect to the Thermo Portal Server. Otherwise, the net intensities will be calculated using the factory-defined reference spectra.
-Steve

Hi Steve,
Because PFE constructs a normal k-ratio using the net intensity from the unknown divided by the net intensity from the standard, it is iterated exactly like the WDS k-ratios when quantified.

The only use of EDS reference spectra (factory or otherwise) would be to perform a more accurate deconvolution in NSS when extracting the net intensities.  I think...   :-\

Is that what you are asking?
john
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SteveSeddio

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Re: Quantifying elements from EDS with PFE
« Reply #5 on: January 05, 2017, 02:21:00 pm »
Yes, I think we're on the same page now!
Your friendly, neighborhood, EPMA-minded EDS guy.
stephen.seddio@thermofisher.com