Real-time analysis of individual diesel engine exhaust particles was demonstrated using an ion trap mass spectrometer. Measurements were made on the nebulized engine oil and diesel fuel for comparison with the exhaust particle analysis. Studieswere performed on individual exhaust particles to determine composition as a function of aerodynamic size. MS/MS analysis positively identified low-mass PAHs as well as indicated the presence of high mass hydrogenated PAHs (HPAHs). The degree of PAHhydrogenation was found to be mass dependent. The origin of the HPAHs seems to be the diesel fuel. However, the HPAHs underwent some degree of oxidation during the combustion process on average. Indicators were found that might be used to determinecombustion efficiency. The capability of the technique for on-line measurement of combustion processes was demonstrated.
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