"Interpretation of volatile organic compound measurements byproton-transfer-reaction mass spectrometry over the deepwaterhorizon oil spill",
International Journal of Mass Spectrometry
, vol. (in press), 2013.
<p>tA proton-transfer-reaction mass spectrometer (PTR-MS) was used onboard the NOAA WP-3D aircraftfor atmospheric measurements over the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico in2010. A mass spectrum obtained by PTR-MS downwind from the accident site revealed the presenceof a complex mixture of volatile organic compounds (VOCs). Here, we interpret this mass spectrum bycomparing it with mass spectra of crude oil, gasoline and diesel samples measured in the laboratory.Aromatics were less abundant over the spill than from crude oil samples, due to the dissolution of thesespecies in the seawater. The mass spectra obtained from aircraft measurements and crude oil samplesboth show strong signals at masses with mass-to-charge ratio (m/z) of 14 × n ± 1, including 43, 57, 69,71, 83, 85, 97 and 111Yamu. PTR-MS coupled with a gas chromatograph was used to identify majormass signals from crude oil samples. Cycloalkanes are important contributors to the signals of mass m/z14 × n ± 1, especially for masses 69, 83, 97 and 111 amu. Aromatics could be interpreted from their specificmasses without significant interference for crude oil vapors, but the interferences to benzene from higheraromatics can be significant as crude oil evaporates. The interpretation of DWH mass spectrum is notonly helpful in understanding the atmospheric emissions associated with the DWH oil spill, but also forthe interpretation of PTR-MS measurements in urban air, near natural oil seeps and oil as well as naturalgas extraction activities.</p>