Vacuum Ultraviolet Single-Photon Ionization Time-of-Flight Mass Spectrometer

A home-made vacuum ultraviolet single-photon ionization time-of-flight mass spectrometer (VUV-SPI-TOFMS) including vacuum system, sampling inlet system, vacuum ultraviolet ionization source, reflection time-of-flight mass analyzer and data acquisition system was introduced. Single-photon ionization with vacuum ultraviolet light is a particularly soft ionization technique. Volatile organic compounds (VOCs) with ionization energy less than the photon energy (10.6 eV) can be ionized into molecular ions. It is nearly fragmentation free compared with electron ionization, and very suitable for qualitative analysis. The mass resolution of the instrument is higher than 800 (Full width at half maximum, FWHM) and the mass accuracy is better than 100 ppm. The initial experiments detected more than 60 components in the mainstream smoke from cigarette, and the limits of detection for acetone, cyclohexane, ethyl acetate and toluene were 0.33, 0.27, 0.42 and 0.11 ppm, respectively. This instrument can be used for real-time and online analysis of VOCs in various environmental media (gas, solid, liquid), and if combined with a membrane inlet system, heating device or purge and trap system, a higher sensitivity could be achieved.