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List of Abstracts 141on the identification of higher molecular weight carboxylic acids (e.g. succinic, glutaric, adipic, pimelic,suberic, azelaic, maleic, fumaric, cis-pinonic, o-phthalic, etc.) in urban aerosols (PM 2.5 , PM 10 ) using a novelHydrophilic Interaction Chromatography – Negative Electrospray Ionization Tandem Mass Spectrometry(HILIC-(-)ESI-MS/MS) method. The separation of the acids was achieved on XBridge Amide BEH column(Waters) using gradient elution with mobile phase composed of 90/10 (v/v) acetonitrile/water mixturecontaining 10mM ammonium acetate (pH = 5) and 10 mM aqueous ammonium acetate (pH = 5). Using aMultiple Reaction Monitoring (MRM) and Neutral Loss (NL44, loss of CO 2 ) scanning MS/MS, severalcarboxylic acids were identified in the urban PM 2.5 and PM 10 aerosols. Among them the most intense peakswere found for succinic, o-phthalic, maleic, azelaic and glutaric acid. Other detected carboxylic acids werepimelic, adipic, suberic and cis-pinonic acid. Using NL44 other peaks were also identified. Some of thedetected acids also gave the same MRM transitions with their studied analogues, but had different retentiontimes. For example, the isomers of o-phthalic acid (like m- or p-phthalic acids) gave the same MRMtransition (m/z 165.0 → m/z 121.1).P-Transformation.35 ID:4252 10:30Slow aging in secondary organic aerosol observed by liquid chromatography coupled with highresolutionmass spectrometryDavid Bones 1 , Adam Bateman 1 , Tran Nguyen 1 , Julia Laskin 2 , Alexander Laskin 3 , Sergey Nizkorodov 11 University of California, Irvine2 Chemical and Materials Sciences Division, Pacific Northwest National Laboratory3 Environmental Molecular Sciences Laboratory, Pacific Northwest National LaboratoryContact: bonesd@uci.eduModel biogenic secondary organic aerosol (SOA) prepared via ozonolysis of limonene has been observed toturn brown when exposed to small amounts of gaseous or aqueous NH 3 . Our hypothesis is that thechromophoric compounds responsible for this color change are conjugated imines. These compounds areonly present in relatively small amounts, hence standard mass spectrometry is insufficient to unambiguouslydetect these compounds. However, a combination of HPLC, UV-Vis detection and high resolutionelectrospray ionization mass spectrometry (HR-ESI-MS) allows assignments of chemical formulae tohundreds of components in aged SOA, including likely chromophores. Peaks corresponding to nitrogencontainingcompounds elute simultaneously with compounds exhibiting peaks in the visible spectrum. LC-MS analyses, in combination with MS/MS analyses, provide extra dimensions of information that canresolve ambiguities in ESI-MS spectra.P-Transformation.36 ID:4565 10:30Secondary organic aerosol using the volatility basis set approach: Comparisons of 3-D model resultswith observations over the U.S during the summer of 2006Stuart McKeen 1 , Ravan Ahmadov 1 , Allen Robinson 2 , Michael Trainer 1 , Si-Wan Kim 1 , Ann Middlebrook 1 ,Roya Bahreini 11 NOAA/ESRL/CSD2 Carnegie Mellon UniverstiyContact: stuart.a.mckeen@noaa.govRegional scale air quality forecast models generally under-predict the organic aerosol (OA) component ofPM2.5 aerosol observed in urban and rural areas of North America using traditional, single-productapproaches to organic vapor/aerosol phase partitioning from the oxidation of a given non-methane organiccarbon (NMHC) compound. More recent parameterizations of secondary OA (SOA) combine laboratorymeasurements of SOA formation with a multi-product representation of NMHC oxidation and semi-idealiCACGP-IGAC 2010 14 July, 2010