期刊
INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
卷 345, 期 -, 页码 80-88出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.ijms.2012.08.030
关键词
Ambient ionization mass spectrometry; Petroleum constituents; Charge exchange; Ion-molecule reactions; Polynuclear aromatics; Fuels
资金
- National Science Foundation [CHE NSF 0848650]
- King Abdullah University Of Science and Technology (KAUST) Thuwal Saudi Arabia
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [0848650] Funding Source: National Science Foundation
Characterization of the various petroleum constituents (hydronaphthalenes, thiophenes, alkyl substituted benzenes, pyridines, fluorenes, and polycyclic aromatic hydrocarbons) was achieved under ambient conditions without sample preparation by desorption atmospheric pressure chemical ionization (DAPCI). Conditions were chosen for the DAPCI experiments to control whether ionization was by proton or electron transfer. The protonated molecule [M+H](+) and the hydride abstracted [MH](+) form were observed when using an inert gas, typically nitrogen, to direct a lightly ionized plasma generated by corona discharge onto the sample surface in air. The abundant water cluster ions generated in this experiment react with condensed-phase functionalized hydrocarbon model compounds and their mixtures at or near the sample surface. On the other hand, when naphthalene was doped into the DAPCI gas stream, its radical cation served as a charge exchange reagent, yielding molecular radical cations (M+center dot) of the hydrocarbons. This mode of sample ionization provided mass spectra with better signal/noise ratios and without unwanted side-products. It also extended the applicability of DAPCI to petroleum constituents which could not be analyzed through proton transfer (e.g., higher molecular PAHs such as chrysene). The thermochemistry governing the individual ionization processes is discussed and a desorption/ionization mechanism is inferred. (c) 2012 Elsevier B.V. All rights reserved.
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