While XRF measurements of PM collected on non-filtrating substrates, such as reflectors, typically require no sample preparation, various sample preparation methods are applied to PM filters. The choice depends on many constrains, including whether the entire substrate, cut portions, or only the removed PM should be used. The main sample preparation methods used for EDXRF and TXRF analysis are summarized in Fig. . In EDXRF, a cut portion or the whole filter can be placed on an XRF sample cup and secured with a binding agent to be measured. Instead, TXRF is designed to analyse dried residues resulting from liquid deposition on a smooth, reflective substrate or thin films. Thus, the dedicated sample preparation strategies are tailored to achieve these specific conditions. For instance, filter solubilization or extraction can be utilized to obtain a liquid solution or suspension, which is then deposited on the reflector and dried for TXRF measurements. Alternatively, a representative portion of the filter can be cut and affixed to a reflective substrate. An innovative preservation method has been recently proposed, involving the plasticization of the entire filter for long-term storage and direct XRF measurement. More details about each procedure are following reported.