title: Comparison of FTIR and particle mass spectrometry for the measurement of particulate organic nitrates.
abstract: While multifunctional organic nitrates are formed during the atmospheric oxidation of volatile organic compounds, relatively little is known about their signatures in particle mass spectrometers. High resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) and FTIR spectroscopy on particles impacted on ZnSe windows were applied to NH(4)NO(3), NaNO(3), and isosorbide 5-mononitrate (IMN) particles, and to secondary organic aerosol (SOA) from NO(3) radical reactions at 22 degrees C and 1 atm in air with alpha- and beta-pinene, 3-carene, limonene, and isoprene. For comparison, single particle laser ablation mass spectra (SPLAT II) were also obtained for IMN and SOA from the alpha-pinene reaction. The mass spectra of all particles exhibit significant intensity at m/z 30, and for the SOA, weak peaks corresponding to various organic fragments containing nitrogen [C(x)H(y)N(z)O(a)](+) were identified using HR-ToF-AMS. The NO(+)/NO(2)(+) ratios from HR-ToF-AMS were 10-15 for IMN and the SOA from the alpha- and beta-pinene, 3-carene, and limonene reactions, approximately 5 for the isoprene reaction, 2.4 for NH(4)NO(3) and 80 for NaNO(3). The N/H ratios from HR-ToF-AMS for the SOA were smaller by a factor of 2 to 4 than the -ONO(2)/C-H ratios measured using FTIR. FTIR has the advantage that it provides identification and quantification of functional groups. The NO(+)/NO(2)(+) ratio from HR-ToF-AMS can indicate organic nitrates if they are present at more than 15-60% of the inorganic nitrate, depending on whether the latter is NH(4)NO(3) or NaNO(3). However, unique identification of specific organic nitrates is not possible with either method.
authors.affiliation: Department of Chemistry, University of California-Irvine, Irvine, CA 92697-2025, USA.
authors.forename: Emily A
authors.initials: EA
authors.lastname: Bruns
authors.forename: Véronique
authors.initials: V
authors.lastname: Perraud
authors.forename: Alla
authors.initials: A
authors.lastname: Zelenyuk
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ezell
authors.forename: Stanley N
authors.initials: SN
authors.lastname: Johnson
authors.forename: Yong
authors.initials: Y
authors.lastname: Yu
authors.forename: Dan
authors.initials: D
authors.lastname: Imre
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Finlayson-Pitts
authors.forename: M Lizabeth
authors.initials: ML
authors.lastname: Alexander
mesh_terms: D004784:Environmental Monitoring / Q000379:methods; D013058:Mass Spectrometry; D009566:Nitrates / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D052638:Particulate Matter / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D009566:Nitrates; D052638:Particulate Matter; D009584:Nitrogen