Analysis of gas-phase polycyclic aromatic hydrocarbon mixtures by laser-induced fluorescence

Laser-induced fluorescence (LIF) is a viable technique for qualitative and quantitative analysis of polycyclic aromatic hydrocarbons (PAH). An analytical tool for a nearly continuous analysis of gas-phase PAH based on LIF was designed and built. The author's intention is to further analyse complex mixtures containing PAH such as tar from gasification processes. This paper deals with measurements of individual PAH-components and mixtures thereof. Comparison of results and calibration of selected PAH-species was performed with on-line gas chromatography/mass spectrometry (GC/MS). A multiple linear regression approach is applied to LIF-spectra of mixtures from selected components at known concentrations in various combinations. It can be demonstrated that this approach opens the possibility to determine the concentration of PAH species in the gas phase at elevated temperatures within×20% accuracy. This is true if LIF-spectra of the individual species for specified concentrations in the PAH mixture are known beforehand. It will be further discussed how results change if substances being present in the mixture remain unconsidered in the calculations.