Time-resolved measurements of low concentration aromatic hydrocarbons in diesel exhaust using a resonance enhanced multi-photon ionization method

Time-resolved measurements of the concentration of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) in exhaust from a diesel vehicle fitted with an oxidation catalyst and operated in JE05 mode are performed at a sensitivity of 10 ppb using a supersonic jet/resonance enhanced multi-photon ionization (Jet-REMPI) method. The concentrations of benzene, naphthalene, and phenol in exhaust from the test vehicle are measured before entering and after exiting from the oxidation catalyst. The total hydrocarbon (THC) is measured simultaneously using a constant volume sample (CVS) instrument fitted with a flame ionization detector (FID). Concentration changes of benzene, naphthalene and phenol are recorded at 1 s intervals and quantified using standard samples. Comparison of these signals with the real-time THC data shows that the time dependence of the individual species is almost the same as that of the THC before the oxidation catalyst but substantially different after.