Micro-XRF instruments are equipped with micro-focused X-ray sources, typically microfocus X-ray tubes or synchrotron radiation sources. These sources generate highly focused X-ray beams, enabling spatially resolved analysis. These instruments employ polycapillary optics to focus and collimate the X-ray beam onto the sample. One of the key features of µ-XRF is spatial resolution which can span from micrometres to submicrometres depending on the instrument, enabling to analyse small portions of interest within a sample. In someµ-XRF instruments elemental mapping is possible, by scanning the sample in a controlled manner beneath the focused X-ray beam. The obtained spatial resolved data provide invaluable insights into the distribution of elements on the sample surface at the µm or even sub-µm scale. In the case of PM samples this feature is fundamental for understanding elemental variations among PM particles and identifying specific particles of interest for source apportionment studies and identification of exposure hotspots . Nevertheless, µ-XRF does have some limitations, including sample size requirements, potential time intensiveness, particularly when performing high-resolution mapping, and a limited ability for depth profiling. These instruments primarily provide information about the surface or near-surface composition of samples and mainly on a qualitative basis.