CHARACTERIZATION OF FLAME-GENERATED C-10 TO C-160 POLYCYCLIC AROMATIC-HYDROCARBONS BY ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION MASS-SPECTROMETRY WITH LIQUID INTRODUCTION VIA HEATED NEBULIZER INTERFACE

Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) generated from fuel-rich combustion of ethylene-naphthalene mixtures in a jet-st irred-plug-flow reactor were chemically characterized by combined mass spectrometric techniques to yield product composition data that cover the molecular mass region from simple PAHs (naphthalene, 128 u) to la rge molecules comparable in molecular size (1792 u) to nanoparticles o f soot. Two techniques based on atmospheric-pressure chemical ionizati on mass spectrometry (APCI-MS) were investigated: (1) APCI-MS combined with high-performance Liquid chromatography through a heated nebulize r interface was found suitable for PAHs up to C-36 (448 u). (2) For th e characterization of larger PAHs beyond C-36, direct liquid introduct ion (DLI) of sample into an atmospheric-pressure chemical ionization m ass spectrometer through a heated nebulizer gave protonated molecular ions for PAHs over the m/z 400-2000 range. Although unequivocal elemen tal composition information is unattainable from the unit-resolution D LI/APCI-MS data, by starting with structural data from identified C-16 to C-32 PAHs, and applying PAH molecular growth principles, it was po ssible to generate PAH molecular maps from the DLI/APCI-MS data from w hich values for the elemental composition could be derived for all maj or peaks.