文摘
We have combined resonance-enhanced multiphotonionization (REMPI) time-of-flight mass spectrometry withon-line flame sampling to determine the centerline concentrations of naphthalene, fluorene, and anthracene ina pure methane + oxygen/argon (1:5) diffusion flame.Naphthalene concentrations between 100 parts perbillionby volume (ppbV) and 6 parts per million by volume(ppmV) and fluorene concentrations below 50 ppbV aredetermined using one-color REMPI on jet-cooled samplesextracted from the flame; anthracene concentrations inthe 5-40 ppbV range are determined using two-colorREMPI. The REMPI ion signals are converted toabsoluteconcentrations in real time by performing gas-phasestandard additions to the flame sample.Isomer-selectivedetection of larger polycyclic aromatic hydrocarbons, suchas perylene and benzo[a]pyrene, is possibleusing the two-color REMPI approach.