A combined single photon ionization and photoelectron ionization source for orthogonal acceleration time-of-flight mass spectrometer

Abstract A novel ion source has been introduced in the present study, which combines the characteristics of single photon ionization (SPI) and photoelectron ionization (PEI). The VUV photons for SPI were generated by a commercial krypton discharge lamp (10.6 eV), and the photoelectrons for electron ionization (EI) were produced through photoemission from a stainless-steel skimmer. The energy of photoelectrons can be well controlled by adjusting the voltages applied on the skimmer. The ionization methods, SPI (SPI mode) and SPI combined photoelectron ionization (SPI–PEI mode), can be rapidly switched. Benefited from the higher working pressure in the ion source, the achieved detection limit of benzene and SO 2 were 0.1 ppmV and 20 ppmV, respectively. The experimental results show the combined ion source has the potential in chemical process and environmental monitoring.