100 Years of Photoionization Mass Spectrometry: History, Principles and Current Applications

Theoretical and physical descriptions of light and matter in the late 19th and early 20th centuries were rapidly followed by the growth of mass spectrometry (MS) as an analytical technology. As an outgrowth of studies of the photoelectric effect in the 1920s, F. L. Mohler developed a photoionization (PI) source for mass spectrometry – most particularly with three publications in 1926 (e.g., Mohler, Phys Rev, 1926). Photoionization therefore actually preceded electron impact (Bleakney, Phys Rev, 1929), the filament-based ionization method that would dominate MS analysis of organic molecules for the next sixty years. Photoionization at atmospheric pressure (AP) was published for the first time in the USSR in 1986 (Revel’skii et. al., Proc USSR Acad Sci, 1986), demonstrating the direct analysis of multiple classes of organic compound but also presaging the integration of the technique with liquid chromatography. 2026 marks 100 years of photoionization in MS, 40 years of APPI, and 25 years since first commercially-available APPI source. The anniversary session has four lectures from researchers active in various areas of photoionization MS, each describing historical background and new research:
G. Asher Newsome, Smithsonian Museum Conservation Institute, USA: “100 Years of Photoionization; Desorption Photoionization for Minimally-invasive Cultural Heritage Analysis”
Ralf Zimmermann, University of Rostock, Germany: “100 Years of Photoionization; Resonance Enhanced Multiphoton Ionization (REMPI) and Single Photon Ionization (SPI) Mass Spectrometry for On-line Process and Product Analysis”
Alla Zelenyuk-Imre, Pacific Northwest National Laboratory, USA: “100 Years of Photoionization; Unraveling Aerosol Complexity One Particle at a Time: Multidimensional Single Particle Characterization”
Fei Qi, Shanghai Jiao Tong University, China: “100 Years of Photoionization; Synchrotron-based Photoionization Mass Spectrometry and Its Applications in Energy Conversion Research”