QUANTITATIVE DIESEL PARTICULATE ANALYSIS USING GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

Detailed analysis of the composition of diesel particulate solvent organic fraction (SOF) is difficult for low-level polycyclic aromatic hydrocarbons (PAH) and generally requires pre-separation of aromatic and aliphatic compounds. This is usually done using either on-line or off-line high performance liquid chromatography (HPLC) which complicates the SOF analysis. Without pre-separation of the samples the gas chromatography (GC) cannot resolve the low-level PAH in the presence of higher levels of n-alkanes and other compounds, which may co-elute. A Finnegan Mat ion trap mass spectrometry (MS) detector was used with a Carlo Erba Mega GC to analyse diesel fuel, diesel particulate SOF and oil without pre-separation. It was shown that the mass number of PAH could easily be extracted from the total ion chromatogram and low-level PAH quantified without pre-separation. A standard calibration mix of PAH covering the mass range of interest was used and the computer software developed to search for and quantify them automatically. This calibration mixture could also be used for the quantification of any other PAH. Pre-separation of the SOF was only necessary for very low-level PAH in the ppb range.