The separation of the X-rays with energies less than 3 keV becomes so small that the peaks are not resolved with an EDS system. The unresolved low-energy K_α and K_β peaks are nearly in Gaussian distribution, while the L and M peaks are asymmetric due to the presence of several unresolved peaks with significant weights near the main peaks.

For the elemental quantification based on low-energy x-rays, e.g. K-peaks from light elements, the k-factors depend on x-ray absorption in the detector window and within the specimen itself. Because of the inaccuracy of the absorption correction, the elemental quantification of light elements is normally worse than that for heavier elements.

The quantification of light elements and low energy X-ray lines is very challenging, especially for standardless quantification, because of:
         i) Large variations in absorption effects in the low energy range.
         ii) Variations in background calculation due to high absorption edges and high statistical error.