Analysis of Combustion products by Time of Flight Mass Spectrometry

In this work we present a new Time of Flight Mass Spectrometer (TOFMS) for on-line detection of combustion products. The products of a premixed laminar ethylene/oxygen flame at atmospheric pressure were sampled, diluted with inert gas and carried to the ion source as a molecular beam under minimal perturbation. Photoionization has been achieved with laser radiation from a Nd:YAG nanosecond laser at two different wavelengths in the UV range (266nm, 355nm). Also Electron impact ionization (EI) has been employed. The mass spectra obtained using laser wavelength of 355 nm present a mass series of peaks regularly spaced 18 Th up to two thousands of mass unit. This series allowed a precise calibration of the apparatus for high molecular weights. The mass spectra obtained using El and wavelength of 266 nm allow to detect complex polycyclic aromatic hydrocarbons (PAH) sequences. Information on the ionization efficiency of analyzed species has been obtained by comparing mass spectra produced with different ionization methods.