Negative ion processes for the unambiguous identification of polycyclic aromatic compounds

Electron capture negative ion processes have been applied to the determination of polycyclic aromatic hydrocarbons in complex mixtures using both chemical ionization mass spectrometry and a newly developed gas chromatographic detector. The negative ion chemical ionization mass spectrometric technique allows isomeric PAH compounds to be differentiated on the basis of relative electron affinities. Compounds which have electron affinities > 0.5 eV form molecular anions while compounds with lower electron affinities are not ionized. The new gas Chromatographic detector also enables isomeric PAH to be differentiated as a function of relative electron affinities. This detector exhibits continuous tunability, allowing the gas phase reactions to be controlled to a greater degree than in the NICI experiment. This flexibility allows a wider variety of compounds to be differentiated using the g.c. detector. Additionally, the g.c. detector may be operated either as a conventional electron capture detector or as an argon ionization detector, which has virtually universal response to organics.