Photoionization Mass Spectroscopy

Atmospheric pressure photoionization mass spectrometry.

Atmospheric pressure photoionization (APPI) is the last arrival in the family of atmospheric pressure ionization (API) methods to couple mass spectrometry (MS) to liquid-phase separation techniques. The basic idea was to further extend the fields of application of liquid chromatography (LC)-MS to those molecules that are not, or are poorly amenable, to electrospray (ESI) or APCI. The present re...

Methyl Radicals in Oxidative Coupling of Methane Directly Confirmed by Synchrotron VUV Photoionization Mass Spectroscopy

Gas-phase methyl radicals have been long proposed as the key intermediate in catalytic oxidative coupling of methane, but the direct experimental evidence still lacks. Here, employing synchrotron VUV photoionization mass spectroscopy, we have directly observed the formation of gas-phase methyl radicals during oxidative coupling of methane catalyzed by Li/MgO catalysts. The concentration of gas-...

Atomic photoionization experiment by harmonic-generation spectroscopy

Breath Analysis Using Photoionization Mass Spectrometry

REMPI (Resonantly Enhanced Multi Photon Ionization) is an ultra-sensitive analytical technique based on the unique combination of laser spectroscopy and mass spectrometry that can rapidly identify and quantify vapor-phase constituents present at part per trillion levels. We have used this method to examine human breath samples for biomarkers of infection. Based on the observed results, we estim...

Vibrational and photoionization spectroscopy of biomolecules: aliphatic amino acid structures.

The aliphatic amino acids glycine, valine, leucine, and isoleucine are thermally placed into the gas phase and expanded into a vacuum system for access by time of flight mass spectroscopy and infrared (IR) spectroscopy in the energy range of 2500-4000 cm(-1) (CH, NH, OH, and stretching vibrations). The isolated neutral amino acids are ionized by a single photon of 10.5 eV energy (118 nm), which...