Fast atom bombardment combined with mass spectrometry for characterization of polycyclic aromatic hydrocarbons

A new approach using fast atom bombardment combined with mass spectrometry to characterize polycyclic aromatic hydrocarbons (PAHs) in the range of 128-252 u molecular weight is described. Sulfolane was employed as a liquid matrix for these π-conjugated hydrocarbons. Bombardment of sulfolane solution of certain PAHs with an atom beam produces both radical cation (M(+.)) and protonated molecule [(M + H)(+)], with no evidence of fragmentation. Collisional activation of the fast atom bombardment-desorbed M(+.) ions, however, results in several structure-specific fragment ions. Structural differences in a few isomeric hydrocarbons can be detected using the [(M + H)(+)]/[M(+.)] abundance ratio and in the pyrene-fluoranthene pair by the B/E linked-field-collision-activated dissociation data. The [(M + H)(+)]/[M(+.)] was found to be compound-specific and correlated well with certain properties (resonance energy, proton affinity, and ionizing energy) of PAHs.