Speciation of Hydrocarbons in Exhaust from Low-Emission, Gasoline-Fueled Vehicles by High-Speed and Standard Gas Chromatography Methods

Previous SAE papers documented the development of a high-speed, high-resolution gas chromatography (GC) instrument for speciating the individual hydrocarbon vapors in vehicle exhaust. The “fast GC” was built in response to an AIGER (American Industry / Government Emissions Research) consortium initiative. This report continues the evaluation and expands the application of the fast GC to include exhaust from low-emission gasoline-fueled vehicles [EPA standard of 0.075 g/mi (50k) NMOG]. An extensive database of 320 exhaust speciation records was generated by collecting and analyzing exhaust from two vehicles that were fueled with five different gasolines. Bag samples were collected during the 1975 FTP driving cycle and analyzed by both the high-speed and the standard GC techniques for method comparison. Statistical analysis of results for nine representative species revealed that the fast GC method generally agreed to within ±10% of the standard GC method for average measured concentrations. Repeatability for the fast GC was about ±3% of the average measured value. The report also includes a rigorous evaluation of detection limit and response linearity characteristics, which showed that the typical fast GC detection limit was about 0.005 ppmC (parts-per-million carbon).