Evaluating Standardless EDS Analysis Accuracy in APEX Software

A crucial job in analysis that uses energy-dispersive X-ray spectroscopy (EDS) is quantitatively determining a sample's elemental composition. To recognize how important this task is, ample care is taken in developing robust analytical models that precisely and accurately determine a sample’s composition. This article offers a summary of the evaluation of the quantitative performance of EDS standardless analysis in the EDAX APEX^™ 3.0 EDS Standard and Advanced software programs.

Results and Discussion

An EDS spectrum is analyzed quantitatively to discover elements' weight or atomic fraction within a sample.

Several articles have been published by Gatan that explain the detailed process of this, but as an overview, in standardless analysis, the X-rays characteristic of elements present in the sample are divided from each other and the Bremsstrahlung background.^1,2,3

An iterative algorithm is then applied to correct for excitation efficiency (also a function of the primary electron energy), possible enhancements of an X-ray line’s intensity by secondary X-ray fluorescence, self-absorption of X-rays generated in the sample, and detector efficiencies to convert net X-ray intensities to elemental composition.

The model utilized in the iterative algorithm (normalized standardless eZAF corrected analysis) has been developed continuously as there is a more extensive comprehension of the physical processes of X-ray generation, detection, and emission.⁴

Before the release of a new EDAX APEX software version, the analytical performance of APEX EDS Standard and Advanced are validated by evaluating spectra collected from over sixty certified standards, inclusive of metal alloys, minerals, and binary compounds. The total absolute error is determined through summation of the absolute difference between the known and measured composition for each element, i, contained in the sample:

Equation 1

Figure 1 shows the notable improvements in compositional analysis accuracy by standardless eZAF correction in APEX software versions, emphasizing the step change in accuracy that is available with APEX EDS software version 3.0.

Further, APEX EDS Advanced software provides greater accuracy by using a computed physical model of Bremsstrahlung background instead of the mathematical filtering approach (SNIP) used in APEX EDS Standard software and other commercially available analysis software. Figure 2 illustrates the improvement for a choice of standards that were analyzed

Figure 1. Improvement of the accuracy of compositional analysis of APEX EDS software evaluated by analysis of mineral, metal, and compound standards. Image Credit: Gatan, Inc.

Figure 2. Error in the analysis of selected standards. Image Credit: Gatan, Inc.

Conclusion

As illustrated in the figures, standardless analysis that uses eZAF correction has recently shown dramatic improvement in APEX EDS Software. However, only the user can determine whether the accuracy levels are enough for the analysis challenges. If not, APEX EDS Advanced software provides the opportunity for further improvements using standards customized coefficients (SCC) for eZAF standardless analysis—an empirical database that optimizes the iterative model for the installation—or full standards quantification (FSQ).

References and Further Reading

1. EDAX (2020). Better EDS Quant Results: Efficiency and eZAF SCC Database. (online) Available at: https://www.edax.com/resources/application-notes/ways-to-improve-the-eds-quantitative-results-accuracy-efficiency-and-ezaf-scc-database (Accessed 19 Feb. 2025).
2. EDAX (2021). eZAF MACC Database and Correction Avoidance | EDAX. (online) Available at: https://www.edax.com/resources/application-notes/ways-to-improve-the-eds-quantitative-results-accuracy-ezaf-macc-database-and-correction-avoidance (Accessed 19 Feb. 2025).
3. EDAX (2021). Better EDS Quant Results: FSQ and SmartStandards | EDAX. (online) Available at: https://www.edax.com/resources/application-notes/ways-to-improve-eds-quantitative-results-accuracy-fsq-and-smartstandards (Accessed 19 Feb. 2025).
4. Eggert, F. (2021). M&M platform presentation ‘Abilities Towards Improved Accuracy in EPMA’. (online) https://doi.org/10.13140/RG.2.2.15067.08487.

This information has been sourced, reviewed and adapted from materials provided by Gatan, Inc.

For more information on this source, please visit Gatan, Inc.