Photoionization Fourier Transform Ion Cyclotron Research Articles

Molecular Evidence of Heavy-Oil Weathering Following the M/V Cosco Busan Spill: Insights from Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Recent studies have highlighted a critical need to investigate oil weathering beyond the analytical window afforded by conventional gas chromatography (GC). In particular, techniques capable of detecting polar and higher molecular weight (HMW; > 400 Da) components abundant in crude and heavy fuel oils (HFOs) as well as transformation products. Here, we used atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS) to identify molecular transformations in oil-residue samples from the 2007 M/V Cosco Busan HFO spill (San Francisco, CA). Over 617 days, the abundance and diversity of oxygen-containing compounds increased relative to the parent HFO, likely from bio- and photodegradation. HMW, highly aromatic, alkylated compounds decreased in relative abundance concurrent with increased relative abundance of less alkylated stable aromatic structures. Combining these results with GC-based data yielded a more comprehensive understanding of oil spill weathering. For example, dealkylation trends and the overall loss of HMW species observed by FT-ICR MS has not previously been documented and is counterintuitive given losses of lower molecular weight species observed by GC. These results suggest a region of relative stability at the interface of these techniques, which provides new indicators for studying long-term weathering and identifying sources.

Throwing Light on Petroleum: Simulated Exposure of Crude Oil to Sunlight and Characterization Using Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

The change in profile of crude oil following a release into the environment is a topic of significant interest, and there is a need to develop analytical methodologies for understanding natural processes which affect related complex mixture profiles. One such process is the exposure to sunlight. In the following investigation, three oil samples were studied: one served as a control, a second was subjected to irradiation by an ultraviolet lamp, and a third sample was irradiated by a SoLux light source which closely models the solar emission profile. The usage of the SoLux light source represents a new method which enables a controlled experiment to mimic the effects of sunlight upon the sample. Atmospheric pressure photoionization was selected as the primary ionization method due to the ability to ionize a broad range of compounds, including low polarity components which could not be observed using electrospray ionization. During a test of sample preparation methods, the addition of a protic cosolvent to the sample solutions was shown to broaden the range of heteroatom-containing components observed. Following characterization, it was found that the polyaromatic hydrocarbons did not change in profile, while compounds containing a heteroatom exhibited a tendency to oxidize following photoirradiation. Sulfur-containing compounds with a low number of double bond equivalents were among the most reactive components of the complex mixture. The photooxidation of compounds in petroleum, following exposure to sunlight, is expected to have significance with regards to solubility and potential toxicity.

Enrichment, Resolution, and Identification of Nickel Porphyrins in Petroleum Asphaltene by Cyclograph Separation and Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

We report here the first high resolution mass spectrometric evidence of nickel porphyrins in petroleum. A petroleum asphaltene sample is fractionated by a silica-gel cyclograph. Nickel content is enriched by approximately 3 fold in one of the cyclograph fractions. The fraction is subsequently analyzed by atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an average mass resolving power of over 500 K (M/DeltaM(fwhm)). Similar to vanadyl porphyrins, monocylcoalkano-type (presumed to be deocophylerythro-etioporphyrin DPEP) Ni porphyrins are found to be the most abundant family followed by etio, bicycloalkano-type, and rhodo-monocylcoalkano-type Ni porphyrins. A Z number ranging from -28 to -44 and a carbon number ranging from 26 to 41 were observed. A significant amount of nickel and vanadyl geoporphyrins are in more condensed tetrapyrrolic cores than just chlorophyll-derived DPEP- and etioporphyrins. Ni has a higher etio/DPEP ratio and rhodo-etio/rhodo-DPEP ratio than does VO.

Stepwise Structural Characterization of Asphaltenes during Deep Hydroconversion Processes Determined by Atmospheric Pressure Photoionization (APPI) Fourier Transform Ion Cyclotron Resonance (FT-ICR) Mass Spectrometry

The compositional analysis (speciation) of heavy oil products is a key step to improve our understanding of hydrotreatment processes and reaction mechanisms. Thus, detailed characterization of polar fractions, such as asphaltenes, should be considered. Here, we employ atmospheric pressure photoionization Fourier transform ion cyclotron mass spectrometry to monitor the evolution of the asphaltene hydrocarbon and sulfur families in deep hydrotreatment processes (fixed and ebullated beds). The results suggest that the complexity of the asphaltenic fractions (in terms of chemical polydispersity) is drastically lowered with increased process severity. In either fixed or ebullated beds, the evolution of the sulfur species is quite similar in class composition, aromaticity (DBE/carbon number ratio), and polycondensation (DBE). The compositional changes are marked by a drastic increase in aromaticity to highly polycondensed dealkylated aromatic structures. Asphaltene disaggregation followed by a dealkylation of t...

Identification of Vanadyl Porphyrins in a Heavy Crude Oil and Raw Asphaltene by Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance (FT-ICR) Mass Spectrometry

Vanadyl porphyrins are detected and characterized by their double-bond equivalents (DBE = number of rings plus double bonds) and carbon number in an unfractionated (raw) asphaltene and unaltered South American crude oil. Atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) provides the high mass-resolving power (450 000−650 000 at m/z 500) and accurate mass (<300 ppb) to unambiguously assign elemental compositions to each of more than 10 000 peaks in each mass spectrum. Kendrick mass sorting revealed unusually high mass errors for peaks assigned to high DBE O2 species as well as a suspicious bimodal distribution in plots of DBE versus carbon number for all O2 species. Inclusion of vanadium in the chemical formula assignment resolved the bimodal distribution into lower DBE O2 species and vanadyl porphyrins, with a subsequent decrease in mass assignment errors to the same level as those for the thousands of other identified species. Vanadyl porp...

Reaction of Hydrogen Gas with C60 at Elevated Pressure and Temperature: Hydrogenation and Cage Fragmentation

Products of the reaction of C(60) with H(2) gas have been monitored by high-resolution atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS), X-ray diffraction, and IR spectroscopy as a function of hydrogenation period. Samples were synthesized at 673 K and 120 bar hydrogen pressure for hydrogenation periods between 300 and 5000 min, resulting in the formation of hydrofullerene mixtures with hydrogen content ranging from 1.6 to 5.3 wt %. Highly reduced C(60)H(x) (x > 36-40) and products of their fragmentation were identified in these samples by APPI FT-ICR MS. A sharp change in structure was observed for samples with at least 5.0 wt % of hydrogen. Low-mass (300-500 Da) hydrogenation products not observed by prior field desorption (FD) FT-ICR MS were detected by APPI FT-ICR MS and their elemental compositions obtained for the first time. Synthetic and analytical fragmentation pathways are discussed.

Hydrogenation of C 60 at 2 GPa pressure and high temperature

Hydrogenation of C 60 at 2 GPa and 723–823 K was performed with thermal decomposition of LiAlH 4 as a hydrogen source. Analysis of hydrogenation products showed that the method can produce not only C 60H 36, but also hydrofullerides C 60H x with 44 < x < 52. Unlike other hydrogenation methods in which pristine C 60 reacts with hydrogen, the high pressure/high temperature conditions result first in C 60 polymerization into a tetragonal phase which later reacts with hydrogen. It is suggested that hydrogen first attacks intermolecular carbon–carbon bonds, resulting in complete depolymerization of C 60 at a later stage of the hydrogenation process. This model suggests the possibility to select starting points for hydrogenation by choosing specific polymeric structures of C 60. Hydrogenated polymeric C 60 was identified as an intermediate reaction product. Characterization of highly reduced material was performed by Raman and IR spectroscopy, X-ray diffraction, and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry.