Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) of perfluorooctane sulfonate (PFOS)

Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) was introduced as a matrix-free LDI-TOF-MS, which succeeded at almost eliminating the background ion interference and offered a new technology for high-speed analysis of low mass compounds. In this study, we first demonstrated that the DIOS-MS is very useful for environmental analysis of perfluorooctane sulfonate (PFOS). In particular, DIOS can detect PFOS with the high sensitivity and the detection limit was 1 ppt without the extraction operation. At the very low concentration of 1 ppt, the PFOS was not detectable with the use of the traditional MS methods such as MALDI-MS and ESI-MS. The quantitative analysis of PFOS in the tap water was also performed from the calibration curve in the low concentration range from 2.5 to 10 ppb. In contrast, it was found that DIOS-MS has a low sensitivity for PFOA. This suggests that the DIOS plate has a high sensitivity for perfluorochemicals of sulfonic acid than that of carboxylic acid as the ionized group.