18 research outputs found
Chromatographic Enrichment and Subsequent Separation of Nickel and Vanadyl Porphyrins from Natural Seeps and Molecular Characterization by Positive Electrospray Ionization FT-ICR Mass Spectrometry
We report a novel chromatographic
method to enrich and separate
nickel and vanadyl porphyrins from a natural seep sample and combine
molecular level characterization by positive-ion electrospray ionization
Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR
MS). Vanadyl and nickel porphyrin model compound elution from primary
secondary amine (PSA) stationary phase combined with UV-vis spectroscopy
confirms enrichment and subsequent fractionation of nickel and vanadyl
porphyrins into polarity-based subfractions. A more than 100-fold
increase in signal-to-noise ratio for nickel porphyrins enables unequivocal
elemental composition assignment confirmed by isotopic fine structure
for all isotopes >1% relative abundance, and the first mass spectral
identification of <sup>61</sup>Ni porphyrin isotopologues derived
from natural seeps. Oxygen-containing vanadyl porphyrins and sulfur-containing
vanadyl porphyrins are isolated in the same fraction simultaneously
from the same sample. We provide the first chromatographic evidence
of carboxylic acid functionalities peripheral to the porphyrin core,
in agreement with previous studies
Chromatographic Enrichment and Subsequent Separation of Nickel and Vanadyl Porphyrins from Natural Seeps and Molecular Characterization by Positive Electrospray Ionization FT-ICR Mass Spectrometry
We report a novel chromatographic
method to enrich and separate
nickel and vanadyl porphyrins from a natural seep sample and combine
molecular level characterization by positive-ion electrospray ionization
Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR
MS). Vanadyl and nickel porphyrin model compound elution from primary
secondary amine (PSA) stationary phase combined with UV-vis spectroscopy
confirms enrichment and subsequent fractionation of nickel and vanadyl
porphyrins into polarity-based subfractions. A more than 100-fold
increase in signal-to-noise ratio for nickel porphyrins enables unequivocal
elemental composition assignment confirmed by isotopic fine structure
for all isotopes >1% relative abundance, and the first mass spectral
identification of <sup>61</sup>Ni porphyrin isotopologues derived
from natural seeps. Oxygen-containing vanadyl porphyrins and sulfur-containing
vanadyl porphyrins are isolated in the same fraction simultaneously
from the same sample. We provide the first chromatographic evidence
of carboxylic acid functionalities peripheral to the porphyrin core,
in agreement with previous studies
Molecular Evidence of Heavy-Oil Weathering Following the M/V <i>Cosco Busan</i> 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 <i>Cosco Busan</i> 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
Tetramethylammonium Hydroxide as a Reagent for Complex Mixture Analysis by Negative Ion Electrospray Ionization Mass Spectrometry
Ultrahigh-resolution Fourier transform
ion cyclotron resonance
mass spectrometry (FTICR MS) enables the direct characterization of
complex mixtures without prior fractionation. High mass resolution
can distinguish peaks separated by as little as 1.1 mDa), and high
mass accuracy enables assignment of elemental compositions in mixtures
that contain tens of thousands of individual components (crude oil).
Negative electrospray ionization (ESI) is particularly useful for
the speciation of the most acidic petroleum components that are implicated
in oil production and processing problems. Here, we replace conventional
ammonium hydroxide by tetramethylammonium hydroxide (TMAH, a much
stronger base, with higher solubility in toluene) to more uniformly
deprotonate acidic components of complex mixtures by negative ESI
FTICR MS. The detailed compositional analysis of four crude oils (light
to heavy, from different geographical locations) reveals that TMAH
reagent accesses 1.5â6 times as many elemental compositions,
spanning a much wider range of chemical classes than does NH<sub>4</sub>OH. For example, TMAH reagent produces abundant negative electrosprayed
ions from less acidic and neutral species that are in low abundance
or absent with NH<sub>4</sub>OH reagent. More importantly, the increased
compositional coverage of TMAH-modified solvent systems maintains,
or even surpasses, the compositional information for the most acidic
species. The method is not limited to petroleum-derived materials
and could be applied to the analysis of dissolved organic matter,
coal, lipids, and other naturally occurring compositionally complex
organic mixtures
Compositional Analysis of Oil Residues by Ultrahigh-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
Ultrahigh-resolution Fourier transform
ion cyclotron resonance
mass spectrometry was used for compositional analysis of polar and
asphaltene fractions of complex oil residues. The samples were collected
before and after the processing of oil in a residue hydrocracking
unit, in which the feed oil was the vacuum distillation residue of
the crude oil, and the product sample was the residue collected after
the processing. From the asphaltene fraction, as many as âŒ26â000
peaks were detected by atmospheric pressure photoionization and more
than âŒ33â000 peaks by positive-ion electrospray ionization
(ESI), with up to 18 distinct heteroatom classes identified. Negative-ion
ESI provided complementary information through selective ionization
of acidic compounds. The detected species were sorted based on heteroatom
class, carbon number and aromaticity (double bond equivalence, i.e.
number of rings + double bonds to carbon). The N<sub>1</sub> class
compounds were predominant in both fractions of the feed and product
oils. The sulfur-containing compounds were mainly degraded or removed
during the processing as expected. Vanadyl porphyrins (heteroatom
class N<sub>4</sub>O<sub>1</sub>V<sub>1</sub>), detected in the asphaltene
fraction of the feed oil, were not observed in the product oil fractions
that is consistent with their efficient removal. Increase in the aromaticity
for the most heteroatom classes was generally noticed in both polar
and asphaltene fractions
Characterization of Pine Pellet and Peanut Hull Pyrolysis Bio-oils by Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
Pyrolysis of solid biomass, in this case pine pellets
and peanut hulls, generates a hydrocarbon-rich liquid product (bio-oil)
consisting of oily and aqueous phases. Here, each phase is characterized
by negative-ion electrospray ionization Fourier transform ion cyclotron
resonance mass spectrometry (ESI FT-ICR MS) to yield unique elemental
compositions for thousands of compounds. Bio-oils are dominated by
O<sub><i>x</i></sub> species: few oxygens per molecule for
the oily phase and many more oxygens per molecules for the aqueous
phase. Thus, the increased oxygen content per molecule accounts for
its water solubility. Peanut hull bio-oil is much more compositionally
complex and contains more nitrogen-containing compounds than pine
pellet bio-oil. Bulk C, H, N, O, and S measurements confirm the increased
levels of nitrogen-containing species identified in the peanut hull
pyrolysis oil by FT-ICR MS. The ability of FT-ICR MS to identify and
assign unique elemental compositions to compositionally complex bio-oils
based on ultrahigh mass resolution and mass accuracy is demonstrated
Characterization of Pine Pellet and Peanut Hull Pyrolysis Bio-oils by Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
Pyrolysis of solid biomass, in this case pine pellets
and peanut hulls, generates a hydrocarbon-rich liquid product (bio-oil)
consisting of oily and aqueous phases. Here, each phase is characterized
by negative-ion electrospray ionization Fourier transform ion cyclotron
resonance mass spectrometry (ESI FT-ICR MS) to yield unique elemental
compositions for thousands of compounds. Bio-oils are dominated by
O<sub><i>x</i></sub> species: few oxygens per molecule for
the oily phase and many more oxygens per molecules for the aqueous
phase. Thus, the increased oxygen content per molecule accounts for
its water solubility. Peanut hull bio-oil is much more compositionally
complex and contains more nitrogen-containing compounds than pine
pellet bio-oil. Bulk C, H, N, O, and S measurements confirm the increased
levels of nitrogen-containing species identified in the peanut hull
pyrolysis oil by FT-ICR MS. The ability of FT-ICR MS to identify and
assign unique elemental compositions to compositionally complex bio-oils
based on ultrahigh mass resolution and mass accuracy is demonstrated
High Field Electron Paramagnetic Resonance Characterization of Electronic and Structural Environments for Paramagnetic Metal Ions and Organic Free Radicals in Deepwater Horizon Oil Spill Tar Balls
In the first use of high-field electron
paramagnetic resonance
(EPR) spectroscopy to characterize paramagnetic metalâorganic
and free radical species from tar balls and weathered crude oil samples
from the Gulf of Mexico (collected after the Deepwater Horizon oil
spill) and an asphalt volcano sample collected off the coast of Santa
Barbara, CA, we are able to identify for the first time the various
paramagnetic species present in the native state of these samples
and understand their molecular structures and bonding. The two tar
ball and one asphalt volcano samples contain three distinct paramagnetic
species: (i) an organic free radical, (ii) a [VO]<sup>2+</sup> containing
porphyrin, and (iii) a Mn<sup>2+</sup> containing complex. The organic
free radical was found to have a disc-shaped or flat structure, based
on its axially symmetric spectrum. The characteristic spectral features
of the vanadyl species closely resemble those of pure vanadyl porphyrin;
hence, its nuclear framework around the vanadyl ion must be similar
to that of vanadyl octaethyl porphyrin (VOOEP). The Mn<sup>2+</sup> ion, essentially undetected by low-field EPR, yields a high-field
EPR spectrum with well-resolved hyperfine features devoid of zero-field
splitting, characteristic of tetrahedral or octahedral MnâO
bonding. Although the lower-field EPR signals from the organic free
radicals in fossil fuel samples have been investigated over the last
5 decades, the observed signal was featureless. In contrast, high-field
EPR (up to 240 GHz) reveals that the species is a disc-shaped hydrocarbon
molecule in which the unpaired electron is extensively delocalized.
We envisage that the measured <i>g</i>-value components
will serve as a sensitive basis for electronic structure calculations.
High-field electron nuclear double resonance experiments should provide
an accurate picture of the spin density distribution for both the
vanadyl-porphyrin and Mn<sup>2+</sup> complexes, as well as the organic
free radical, and will be the focus of follow-up studies
Comprehensive Analysis of Changes in Crude Oil Chemical Composition during Biosouring and Treatments
Biosouring
in crude oil reservoirs by sulfate-reducing microbial
communities (SRCs) results in hydrogen sulfide production, precipitation
of metal sulfide complexes, increased industrial costs of petroleum
production, and exposure issues for personnel. Potential treatment
strategies include nitrate or perchlorate injections into reservoirs.
Gas chromatography with vacuum ultraviolet ionization and high-resolution
time-of-flight mass spectrometry (GC-VUV-HTOF) and Fourier transform
ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with
electrospray ionization were applied in this study to identify hydrocarbon
degradation patterns and product formations in crude oil samples from
biosoured, nitrate-treated, and perchlorate-treated bioreactor column
experiments. Crude oil hydrocarbons were selectively transformed based
on molecular weight and compound class in the biosouring control environment.
Both the nitrate and the perchlorate treatments significantly reduced
sulfide production; however, the nitrate treatment enhanced crude
oil biotransformation, while the perchlorate treatment inhibited crude
oil biotransformation. Nitrogen- and oxygen-containing biodegradation
products, particularly with chemical formulas consistent with monocarboxylic
and dicarboxylic acids containing 10â60 carbon atoms, were
observed in the oil samples from both the souring control and the
nitrate-treated columns but were not observed in the oil samples from
the perchlorate-treated column. These results demonstrate that hydrocarbon
degradation and product formation of crude oil can span hydrocarbon
isomers and molecular weights up to C<sub>60</sub> and double-bond
equivalent classes ranging from straight-chain alkanes to polycyclic
aromatic hydrocarbons. Our results also strongly suggest that perchlorate
injections may provide a preferred strategy to treat biosouring through
inhibition of biotransformation
Detailed Compositional Characterization of the 2014 Bangladesh Furnace Oil Released into the Worldâs Largest Mangrove Forest
On
December 9, 2014, âŒ94âŻ000 gallons of furnace oil
spilled into the Shela River in Bangladesh, a designated World Heritage
Site by the United Nations Educational, Scientific and Cultural Organization.
It was the largest recorded oil spill in the Sundarbans region. Visually,
furnace oil appears similar to heavy fuel oil, but little is known
about its composition even though it is heavily utilized worldwide.
A shift in global oil production to heavier, less well-known feeds
(i.e., heavy oil and bitumen) requires molecular-level knowledge for
efficient response, damage assessment, and restoration in the event
of any oil spill. However, little is known about the chemical composition
of furnace oil in chronic and acute releases. For the first time,
we catalog the molecular-level composition of a relatively unknown
furnace oil collected immediately after the 2014 Bangladesh spill
and compare it to a well-characterized intermediate fuel oil (IFO)
spilled in Texas City, Texas (U.S.A.) in March 2014. Through a combined
technique approach, we apply comprehensive two-dimensional gas chromatography
(GCĂGC) analysis and Fourier transform ion cyclotron resonance
mass spectrometry (FT-ICR MS) to contrast the unknown furnace oil
to IFO. Combined, these techniques capture the continuum of oil components
and access the less volatile, highly complex non-GC amenable compounds.
GCĂGC analysis provides biomarker signatures that suggest the
furnace oil likely originated in the Middle East and is a refined
product. We further compared the furnace oil with the Arabian light
crude from Middle East origin (WP681) and revealed remarkable similarities
between the two oils. Simulated distillation for the furnace oil showed
that 42% of the oil mass is not volatile below 478 °C (equivalent
to C<sub>40</sub>; the upper limit for GC-based techniques), whereas
the IFO contained 38% of the total mass >C<sub>40</sub>. Furthermore,
FT-ICR MS extends the carbon number range and unlocks the molecular
composition of non-GC amenable compounds. Atmospheric pressure photoionization
(APPI) and electrospray ionization (ESI) FT-ICR MS resolve and identify
tens of thousands of molecular formulas in each oil and report furnace
oil composition similar to whole heavy crudes. To the best of our
knowledge, this is the first report of the detailed compositional
characterization of any furnace oil