In practical analytical measurements, Fe EELS signal is normally obtained from Fe L₃ edge (710 eV), which is in general a better choice than Fe EDS signal.

Figure 1282a (a) shows Fe L_2,3 (710 eV) energy loss edge of nano-crystalline mineral ferrihydrite (FHY) obtained at an acquisition time of 0.05 s per pixel which provided the maximum electron dose without internal atomic rearrangement in the material. In this spectrum, the noise level is too high. Therefore, a spectrum, as shown in Figure 1282a (b), with good SNR had to be obtained by summing such noisy spectra of many pixels taken from identical materials.

Figure 1282b shows the EELS of Fe₂O₃ material. One can see that the signal-to-noise ratio (SNR) of Fe L_2,3 EELS signal is the highest at t/λ ≈ 0.3, namely t ≈34 nm.

[1] G. Vaughan, A.P. Brown, R. Brydson, K. Sader, A low electron fluence EELS study of Fe-coordination within ferrihydrite and phosphorous doped ferrihydrite nanoparticles, EMC 2008 14th European Microscopy Congress Volume 1 Instrumentation Methods Luysberg.
[2] G. Kothleitner, PhD Thesis, Graz University of Technology (1997), Graz, Austria.