Measurement of Aerosol Organic Compounds Using a Novel Collection/Thermal-Desorption PTR-ITMS Instrument

We report the development and characterization of a proton-transfer-reaction ion trap mass spectrometer for the speciated measurement of organic compounds in atmospheric aerosols and show results from its first field deployment. The instrument uses an aerosol collection inlet to accumulate aerosol mass followed by rapid thermal desorption to volatilize the organic compounds for in situ analysis. We have performed laboratory studies to characterize instrument performance and the instrument was deployed aboard a NOAA research vessel during the Texas Air Quality Study 2006/Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS 2006/GoMACCS) in August-September 2006. The laboratory-determined detection limit for glutaric acid in mixed glutaric acid/NH 4 HSO 4 test aerosols was 0.22 ng collected mass, which corresponds to an estimated detection limit of 12 ng m −3 for a 10 min sample based on the instrument sample flow rate of 1.8 L min −1 . During TexAQS 2006/GoMACCS, signals well above the detection limit were observed at a number of mass to charge ratios, mostly occurring during an extended period of active pollution photochemistry, but also including detection of possible primary emissions of aerosol-phase pyridine.