Ion-molecule reactions of halocarbon cations with polycyclic aromatic hydrocarbons in a quadrupole ion trap .1. Differentiation of structural isomers

Ion-molecule reactions between polycyclic aromatic hydrocarbons (PAHs) and ions (R+) generated from halogenated hydrocarbons (dichloromethane, chloroform, carbon tetrachloride, 1,1-dichloroethane, difluoromethane and 1,1-difluoroethane) in a quadrupole ion trap were used to differentiate a series of structural isomers of PAHs. This differentiation was based on the formation of [M + R](+) and [M + R - HX](+) products (X = Cl, F) between the halocarbon ions (R+) and PAH molecules (M). Halomethanes were found to give rise predominantly to the elimination products [M + R - HX](+), while the haloethanes also yielded significant amounts of the [M + R](+) adducts. Differences in the ionization energies of the PAH isomers seem to be partially responsible for this differentiation process, Collision-induced dissociation experiments also revealed structural differences in the adducts of different PAH isomers. (C) 1997 by John Wiley & Sons, Ltd.