Compositional analysis of materials is possible using an SEM coupled with Energy-Dispersive X-ray Spectroscopy (EDX) detectors. By employing the SEM's EDX detector, variations in compositions of materials can be mapped over the scale of millimeters to micrometers (microns). This is done by bombarding a sample surface with electrons and measuring the energies and intensities of the emitted x-rays. The x-ray energies are characteristic of the specimen's elemental composition, and the intensity of the x-rays are directly associated with weight fraction of each of those chemical elements.

Qualitative elemental analysis can be acquired from a specific location, or in the form of an elemental profile relative to a line or an area of interest (i.e., as elemental linescans or elemental maps). The technique lends itself easily to qualitative analysis when the researcher only needs to know relative elemental distributions. However, quantitative analysis is also possible when properly calibrated with standards, and has detection limits near 1000ppm.

The FEI Quanta 400 is equipped with a Bruker 4th generation XFlash SDD X-ray detector, while the FEI MLA 650FEG is equipped with dual Bruker 5th generation XFlash SDD X-ray detectors.