Speciation of Organic Gas Emissions from E85 Vehicles Using Mass Spectrometry and Photoacoustic Detection

In this study, a speciation of organic gas emissions from E85-fuelled light duty vehicles was performed through mass spectrometric (MS) analysis of exhaust bag samples from a constant volume sampling (CVS) system. The objective was to identify and measure all organic species that gave a significant contribution to the Flame Ionization Detector (FID) response. It was concluded that the speciated concentration data that was obtained through the MS and a photoacoustic sensor was sufficient to predict the FID response for the CVS bag samples with a high degree of accuracy. Further on, it could be concluded that: methane, ethanol, ethene, acetylene (ethyne) and acetaldehyde all gave significant contributions to the FID response. Methane was the dominating contributor to the FID response in tests with relatively lower emissions and ethanol dominated in tests with relatively higher organic gas emissions.

In addition, the performance of the MS in relation to officially approved methods for emission measurements of ethanol and acetaldehyde was evaluated. If proven sufficiently accurate, the use of MS for E85 engine development testing could potentially simplify the measurement setup and shorten result reporting times. The relative correlation between the MS ethanol results and the CARB approved photoacoustic sensor was strong. However, the MS consistently reported somewhat lower absolute values. For acetaldehyde, the MS results were compared to results from an approved DNPH-cartridge sampling method and HPLC analysis, resulting in a relatively poor correlation.