Hello, I did an x-ray dispersive (EDS) analysis for my samples. I have noticed an error higher than 25% . moreover, the error indicates is close to the element concentration analyzed.
From here, can I come to a conclusion that this analyses not accurate results for my sample? Thank you!
Dear Dr. Ketroussi Khadidja ,
X-ray intensities are measured by counting photons and the precision obtainable is limited by statistical error. In general, for major elements it is usually not difficult to obtain an analytical accuracy is commonly between ± 2% - ± 5%, owing to other factors such as uncertainties in the compositions of the standards and errors in the various corrections which need to be applied to the raw data.
Semi-quantitative results are readily available without standards by using mathematical corrections based on the analysis parameters and the sample composition.The accuracy of standardless analysis depends on the sample composition. Greater accuracy is obtained using known standards with similar structure and composition to that of the unknown sample.
For details please see the following interesting notes/paper:
- Introduction to Energy Dispersive X-ray Spectrometry (EDS), available at: https://cfamm.ucr.edu/documents/eds-intro.pdf
- Energy Dispersive X-Ray Spectroscopy (EDS), available at: https://www.mee-inc.com/hamm/energy-dispersive-x-ray-spectroscopyeds/
- Is Scanning Electron Microscopy/Energy Dispersive X‐ray Spectrometry (SEM/EDS) Quantitative? (...... the answer was yes but under certain conditions related to the experimental measurement set up and analyzed sample characteristics ...).
Dale E. Newbury, Nicholas W. M. Ritchie
SCANNING, Vol. 35, 141–168 (2013).
Best regards, Pierluigi Traverso
Accuracy of results of quantitative EDS analysis depends mostly on operator. Unskilled operator can get very high errors, especially when working with light elements, such as O or C.
Adding to mentioned above, EDS analyses depend greatly on sample's surface, homogenity, density etc. One can't say whether your results are believeable not knowing following: sample composition, sample size, surface conditions/sample preparation methidics, operating conditions, spectra aquiring conditions.
That's actually what "methods" section in articles stands for.
Pierluigi Traverso
Dear Pierluigi Traverso
thank you for your help and for the link that I found very interesting and very helpful
Vladimir Dusevich
Dear Vladimir Dusevich
thank you for this information, this is exactly my case,
the material analyzed composed of light elements (oxygen, boron, Azote). please, can i ask you another question?
Regarding the results, do I take the concentration obtained into account (with an error of 25%)?
Vladimir V. Shilovskikh
Dear Vladimir V. Shilovskikh
Thank you for your help
Why are you sure an error is 25%? Is your specimen stoichiometric?
I would discard results of quantification and use only qualitative results. If you need a comparison of two (or more) specimens of similar composition, you can use peak intensities.
EDS can be just as good as WDS. What is your instrument specification? How did you prepare your samples? What type of samples are they? Did you use relevant standards? If you get all this right you should not get a 25% error
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