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REAL TIME, ON-LINE CHARACTERIZATION OF DIESEL GENERATOR AIR TOXIC EMISSIONS BY RESONANCE ENHANCED MULTI-PHOTON IONIZATION TIME OF FLIGHT MASS SPECTROMETRY
Citation:
Oudejans, L, A. Touati, AND B K. Gullett*. REAL TIME, ON-LINE CHARACTERIZATION OF DIESEL GENERATOR AIR TOXIC EMISSIONS BY RESONANCE ENHANCED MULTI-PHOTON IONIZATION TIME OF FLIGHT MASS SPECTROMETRY. Analytical Chemistry. American Chemical Society, Washington, DC, 76(9):2517-2524, (2004).
Description:
The laser based resonance, enhanced multi-photon ionization time-of-flight mass spectrometry (REMPI-TOFMS) technique has been applied to the exhaust gas stream of a diesel generator to measure, in real time, concentration levels of aromatic air toxics. Volatile organic compounds (VOCs), as well as several polycyclic aromatic hydrocarbons (PAHs), were detected in the concentration range of 10-200 ppb in the steady state diesel generator exhaust. The results were verified and compared with conventional extractive sampling and analytical techniques using gas chromatography mass spectrometry (GCMS). The high isomer selectivity of the REMPI-TOFMS instrument provided data for individual xylene isomers that are otherwise (partially) co-eluting in standard GCMS analyses. Good agreement was observed between results for volatile and semivolatile organic compounds obtained with REMPI-TOFMS and conventional extractive sampling. Transient events, like cold start-ups of the diesel generator, resulted in sharp (less than 15 s) peak emissions that were, for benzene, up to a factor of 90 higher than the predominately constant concentrations observed during continual operation; warm re-starts resulted in a factor 2.5 lower than the peak concentration. These fast transient emissions are only visible using a real time approach (1 s resolution) as demonstrated here using REMPI-TOFMS.