Determination of single photon ionization cross sections for quantitative analysis of complex organic mixtures

Anal Bioanal Chem. 2007 Nov;389(6):1941-51. doi: 10.1007/s00216-007-1571-x. Epub 2007 Sep 14.

Abstract

Soft single photon ionization (SPI)-time-of-flight mass spectrometry (TOFMS) is well suited for fast and comprehensive analysis of complex organic gas mixtures, which has been demonstrated in various applications. This work describes a calibration scheme for SPI, which enables quantification of a large number of compounds by only calibrating one compound of choice, in this case benzene. Photoionization cross sections of 22 substances were determined and related to the yield of benzene. These substances included six alkanes (pentane, hexane, heptane, octane, nonane, decane), three alkenes (propene, butane, pentene), two alkynes (propyne, butyne), two dienes (butadiene, isoprene), five monoaromatic species (benzene, toluene, xylene, styrene, monochlorobenzene) and NO. The cross sections of organic compounds differ by about one order of magnitude but the photoionization properties of compounds belonging to one compound class are rather similar. Therefore, the scheme can also be used for an approximate quantification of compound classes. This is demonstrated by a fast characterization and pattern recognition of two gasoline samples with different origins (Germany and South Africa) and a diesel sample (Germany). The on-line capability of the technique and the scheme is demonstrated by quantitatively monitoring and comparing the cold engine start of four vehicles: a gasoline passenger car, a diesel van, a motorbike and a two-stroke scooter.

MeSH terms

  • Alkanes / analysis
  • Alkenes / analysis
  • Calibration
  • Complex Mixtures / analysis*
  • Hydrocarbons, Aromatic / analysis
  • Molecular Weight
  • Organic Chemicals / analysis*
  • Photochemistry
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / instrumentation
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods
  • Time Factors
  • Vehicle Emissions / analysis*
  • Vehicle Emissions / toxicity

Substances

  • Alkanes
  • Alkenes
  • Complex Mixtures
  • Hydrocarbons, Aromatic
  • Organic Chemicals
  • Vehicle Emissions