Differentiation of methyl substituted fluorenes, anthracenes and benz[a]anthracenes using surface‐catalyzed oxidation reactions and negative ion chemical ionization mass spectrometry

Methyl‐substituted polycyclic aromatic hydrocarbons (PAH) are shown to undergo surface‐catalyzed reactions with oxygen. These reactions generate oxidized products, which include aldehydes, quinones, and anhydrides. The products dominate the O₂/N₂ negative ion chemical ionization (NICI) mass spectra of methyl‐PAH when the ion source temperature is elevated to 300°C. The NICI mass spectra of methyl‐PAH measured under these conditions show ions that can be used to distinguish the position of methyl groups substituted on fluorene, anthracene, and benz[a]anthracene isomers.