Structural Comparison of Asphaltenes of Different Origins Using Multi-stage Tandem Mass Spectrometry
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Type
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Journal
Article
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Author
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Weijuan
Tang
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Author
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Matthew
R. Hurt
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URL
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Publication
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Energy
& Fuels
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Date
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February
3, 2015
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Journal
Abbr
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Energy
Fuels
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Abstract
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Reports
a study of six petroleum asphaltene samples of different geographical origins
using atmospheric pressure chemical ionization (APCI) in positive-ion mode in
a linear quadrupole ion trap mass spectrometer (LQIT). Researchers used APCI
doped with carbon disulfide reagent as the ionization method, because it has
been previously demonstrated to generate stable molecular ions with no
fragmentation for asphaltene molecules. The mass spectra measured using this
approach revealed the apparent molecular weights (MWs) of the molecules in
the asphaltene samples.
Results revealed that petroleum asphaltenes from the American continent, Europe, and China have similar apparent molecular weight distributions, ranging from 200 to 1450 Da, with slightly different apparent average MWs ranging from 570 to 700 Da. In addition, molecular ions with eight randomly selected mass-to-charge ratios (m/z) ranging from m/z 500 to 808 were isolated for each asphaltene sample and subjected to collisionally activated dissociation (CAD) at the same collision energy to examine their structures. CAD mass spectra provided information on the maximum total number of carbons in the alkyl chains and the smallest possible size of the aromatic cores in the ionized molecules. Researchers conducted MS3 experiments to examine the fragmentation patterns of the fragment ions generated in the MS2 experiments. Results support the island structural model for these asphaltenes. |
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