Advantages and limitations of laser desorption/ionization mass spectrometric techniques in the chemical characterization of complex carbonaceous materials

Advanced mass spectrometric systems have been tested for the analysis of heavy fractions of fuel oils and combustion-formed particulate in terms of mass range detection and resolution. The analysis of these complex aromatic samples is not amenable to conventional chromatographic- mass spectrometric techniques due to their low volatility and degradability. In this paper, the advantages and the shortcomings of different ionization methods (electron impact, photoionization, laser ionization) and different mass analyzers (quadrupole, ion trap, time of flight) have been carefully investigated. The optimization of operative parameters has shown to be crucial for the extension of mass detection range. The Atmospheric Pressure Photoionization-Mass Spectrometry techniques showed the best performances in terms of low fragmentation of the parent ion and sensitivity for the analysis of asphaltenes. Laser Desorption Ionization-Mass Spectrometry showed to be more suitable for the analysis of aromatic tarry combustion-formed species.