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A newly developed, mobile laser mass spectrometer (resonance-enhanced multiphoton ionization - time-of-flight mass spectrometer, REMPI-TOFMS) was applied to on-line measurements at a waste incineration pilot plant. REMPI-TOFMS combines the optical selectivity of resonance-enhanced multiphoton ionization with a time-of-flight mass analysis to give a two-dimensional analytical method. Special care was taken to build up a sampling and inlet system suitable for on-line measurements of large, semivolatile polycyclic aromatic hydrocarbons (PAHs). An effusive molecular beam inlet in combination with a fixed frequency UV laser (Nd:YAG at 266 nm or KrF excimer at 248 nm) was used. Under these conditions, many different PAHs can be ionized selectively from the complex flue gas matrix. For example, the achieved detection limit for naphthalene is in the 10 parts-per-trillion by volume (pptv) concentration range. Calibration was performed by using external concentration standards supplied in low ppbv concentrations. The instrumentation is sufficiently robust to be operated under industrial conditions at incineration plants, for instance. The REMPI mass spectra can be acquired at 5-50 Hz. Time profiles of the concentrations of different PAHs in the flue gas were monitored with a time resolution of 200 ms. Significant variations in the concentration profile of several PAHs up to mass 276 amu (e.g., benzo[ghi]perylene) and methylated PAHs have been observed while combustion parameters were changing. In summary, it was demonstrated that laser mass spectrometry (REMPI-TOFMS) enables a real-time on-line trace analysis of combustion flue gases or industrial process gases.

The combination of laser induced Resonance-Enhanced Multi-Photon Ionization and Time-Of-Flight Mass Spectrometry (REMPI-TOFMS) represents a highly selective and sensitive analytical technique ideal for real-time determination of organic trace components. For example, aromatic hydrocarbons can be continuously monitored in industrial off gases. We introduce a new mobile REMPI-TOFMS instrument, which is robust and easy to operate, even under industrial conditions. Instead of an on-line sampling system also a gas chromatograph can be coupled for ultratrace analytical work. The instrument can be equipped with different inlet techniques (effusive inlet, free and skimmed supersonic jet), different TOF mass spectrometric options (linear mode and reflectron mode for higher mass resolution) or different laser systems (robust fixed wavelength lasers or tunable lasers for more sophisticated applications). This flexibility allows the instrument to be readily adapted to a given analytical problem. New time-resolved dat...

Laser mass spectrometry is applied for on-line analysis of PAHs from a complex flue gas matrix in the combustion chamber of an incineration plant. Process monitoring of industrial processes can be performed. New insights into the formation of toxic combustion byproducts are possible.

Laser induced Resonance-Enhanced Multi-Photon Ionization Time-Of-Flight Mass Spectrometry (REMPI TOFMS) is a highly selective as well as sensitive analytical technique, well suited for species selective, on-line monitoring of trace-substances. In this contribution some analytical applications of a mobile REMPI-TOFMS are presented. This includes REMPI-TOMS on-line analysis of coffee roasting gas and waste incineration flue gas as well as headspace measurements of pulp processing lye or rapid analysis of polycyclic aromatic hydrocarbons from soil samples via thermal desorption.

Resonance-enhanced multiphoton ionization (REMPI) allows different degrees of optical ionization selectivity. The selectivity achievable with the REMPI-method is compared with that of other ionization methods for on-line mass spectrometry. “Semiselective” REMPI with effusive molecular beam inlet allows group selective ionization of mono- and polycyclic aromatic compounds and their methylated derivatives (REMPI at 266 nm). The patterns of the above mentioned aromatic compounds in flue gases can be used for characterization of industrial combustion processes. In this work, a novel approach of “semi-selective” REMPI for measure ment of the patterns of mono- and polycyclic aromatic compounds, with additional simultaneous target compound monitoring, is presented. By using REMPI at 269.8 nm monochloro benzene, which is an important indicator for the toxicity of the flue gas, can be monitored, together with the other aromatics. On-line recorded REMPI mass spectra from the flue gas of an industrial hazardous waste incineration plant are presented. The applications of REMPI on-line monitoring at incineration plants are discussed.