Traditional PFAS analysis by mass spectrometry (MS) is time-consuming, as laborious sample preparation (e.g., extraction and desalting) is necessary. This invention reports fast detection of PFAS by paper spray (PS)-based MS techniques, which employs a triangular-shaped filter paper for sample loading and ionization (≤ 3 min per sample). PS-MS can be used for direct PFAS analysis of drinking water, tap water, and wastewater. Interestingly, food package paper materials (also other samples such as vegetables/fruits) can be directly cut into triangular shaped pieces and examined with PS-MS for possible PFAS contamination. For samples containing salt matrices which would suppress PFAS ion signal, desalting paper spray mass spectrometry (DPS-MS), was shown to be capable of rapidly desalting, ionizing and detecting PFAS species such as per-flurooctanoic acid (PFOA) and per-flurosulphonic acid (PFOS). The retention of PFAS on paper substrate while salts being washed away by water is likely due to hydrophilic interaction between the PFAS polar head (e.g., carboxylic acid, sulfonic acid) with the polar filter paper cellulose surface. The DPS-MS method is highly sensitive (limits of detection:1.2-4.5 ppt) and can be applicable for directly analyzing soil extract and soil samples. These results suggest the high potential of PS-MS and the related DPS-MS technique in real-world environmental analysis of PFAS.