XRF relies on the excitation of atoms in the sample by high or low-energy X-ray photons. When the incident X-rays with sufficient energies interact with the atoms, inner-shell electrons are ionized or promoted to higher energy levels. This excitation destabilizes the atoms, and as they return to their ground state, they emit characteristic X-rays that are characteristic of the specific elements present in the sample . Various experimental configurations are used in XRF instruments, each tailored for specific applications and sample types. The most common setup used for PM analysis is Energy Dispersive XRF (EDXRF) which uses a detector to measure the energy of X-ray fluorescence emitted by a sample. Two additional XRF based techniques are used: Wavelength-Dispersive XRF (WDXRF) and Micro XRF (µ-XRF).