title: Validation of atmospheric VOC measurements by proton-transfer-reaction mass spectrometry using a gas-chromatographic preseparation method.
abstract: Proton-transfer-reaction mass spectrometry (PTR-MS) has emerged as a useful tool to study volatile organic compounds (VOCs) in the atmosphere. In PTR-MS, proton-transfer reactions with H30+ ions are used to ionize and measure VOCs in air with a high sensitivity and fast time response. Only the masses of the ionized VOCs and their fragments, if any, are determined, and these product ions are not unique indicators of VOC identities. Here, a combination of gas chromatography and PTR-MS (GC-PTR-MS) is used to validate the measurements by PTR-MS of a number of common atmospheric VOCs. We have analyzed 75 VOCs contained in standard mixtures by GC-PTR-MS, which allowed detected masses to be unambiguously related to a specific compound. The calibration factors for PTR-MS and GC-PTR-MS were compared and showed that the loss of VOCs in the sample acquisition and GC system is small. GC-PTR-MS analyses of 56 air samples from an urban site were used to address the specificity of PTR-MS in complex air masses. It is demonstrated that the ions associated with methanol, acetonitrile, acetaldehyde, acetone, benzene, toluene, and higher aromatic VOCs are free from significant interference. A quantitative intercomparison between PTR-MS and GC-PTR-MS measurements of the aforementioned VOCs was performed and shows that they are accurately measured by PTR-MS.
authors.affiliation: National Oceanic and Atmospheric Administration, Aeronomy Laboratory, 325 Broadway, Boulder, Colorado 80305, USA. cwarneke@al.noaa.gov
authors.forename: Carsten
authors.initials: C
authors.lastname: Warneke
authors.forename: Joost A
authors.initials: JA
authors.lastname: De Gouw
authors.forename: William C
authors.initials: WC
authors.lastname: Kuster
authors.forename: Paul D
authors.initials: PD
authors.lastname: Goldan
authors.forename: Ray
authors.initials: R
authors.lastname: Fall
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D009930:Organic Chemicals / Q000032:analysis; D011522:Protons; D014835:Volatilization
chemical_list: D000393:Air Pollutants; D009930:Organic Chemicals; D011522:Protons