Search

Pavement sealants are of environmental concern because of their complex petroleum-based chemistry and potential toxicity. Specifically, coal tar-derived sealants contain high concentrations of toxic/carcinogenic polycyclic aromatic hydrocarbons (PAHs) that, when weathered, can be transferred into the surrounding environment. Previous studies have demonstrated the effects of coal tar sealants on PAH concentration in nearby waterways and their harmful effects in aquatic ecosystems. Here, we investigate and compare the molecular composition of two different pavement sealants, petroleum asphalt- and coal tar-derived, and their photoproducts, by positive-ion (+) atmospheric pressure photoionization (APPI) and negative-ion (-) electrospray ionization (ESI) coupled with ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry to address species (high-boiling and/or high oxygen content) that lie outside the analytical window of other techniques due to ultra-high molecular complexity. In addition, we evaluate the toxicity of the water-soluble photoproducts by use of Microtox bioassay. The results demonstrate that the coal tar sealant contains higher amounts of PAHs and produces abundant water-soluble compounds, relative to unweathered materials, with a high abundance of PAH-like molecules of high toxicity. By comparison, the asphalt sealant produces fewer toxic water-soluble species, with molecular compositions that are consistent with natural dissolved organic matter. These results capture the mass, chemical diversity, toxicity, and source/photoproduct relationship of these compositionally complex emerging contaminants from the built environment.

International audience

International audience; Recent advances in instrumentation for high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) have enabled access to ∼70 »000 unique molecular formulas in broadband mass spectral characterization of unfractionated/whole asphaltenes. The results accumulated over a decade highlight the need for an asphaltene molecular model that acknowledges the coexistence of (1) monofunctional and polyfunctional species; (2) island and archipelago structural motifs; and (3) heteroatom-depleted/highly aromatic compounds, as well as atypical species with low aromaticity but increased heteroatom content. Collectively, results from FT-ICR MS, preparatory-scale separations (extrography/interfacial material), gel permeation chromatography, precipitation behavior in heptane:toluene, thermal decomposition, and aggregate microstructure by atomic force microscopy (among other techniques), suggest that the strong aggregation of asphaltenes results from the synergy between several intermolecular forces: π-stacking, hydrogen bonding, London forces, and acid/base interactions. This review presents general features of asphaltene molecular composition reported over the past five decades. We focus on mass spectrometry characterization and expose the reasons why early results supported the dominance of single-core motifs. Then, the discussion shifts to recent advances in instrumentation for high-field FT-ICR MS, which have enabled the detection of thousands of species in asphaltene samples, whose molecular composition and fragmentation behavior in ultrahigh vacuum agree with the coexistence of single-core and multicore structural motifs. Furthermore, evidence that highlights the limitations of commercially available/custom-built ion sources and selective ionization effects is presented. Consequently, the limitations require separations (e.g., chromatography, extrography) to gain more-comprehensive molecular-level insights into the composition of these complex organic mixtures. The final sections present evidence for the role of aggregation in selective ionization and suggest that advanced characterization by both thermal desorption/decomposition and liquid chromatography with online FT-ICR MS detection can be employed to mitigate the effects of aggregation and provide unique insights in molecular composition/structure.

High magnetic field Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry provides the highest mass resolving power and mass measurement accuracy for detailed characterization of complex chemical mixtures. Here, we report the coupling of online liquid chromatography of complex mixtures with a 21 tesla FT-ICR mass spectrometer. The high magnetic field enables large ion populations to be analyzed for each spectrum for a high dynamic range, with 3.2 million mass resolving power at m/z 400 (6.2 s transient duration) or 1.6 million (3.1 s transient duration) while maintaining high mass accuracy for molecular formula assignment (root-mean-square assignment error < 0.150 ppm). Thousands of unique elemental compositions are assigned per mass spectrum, which can be grouped by the heteroatom class, double bond equivalents (the number of rings and double bonds to carbon), and carbon number. Figures of merit are discussed, as well as characterization of an Arabian heavy vacuum gas oil in terms of the ring number, compound class, double bond equivalents, and ion type. Consideration of elemental composition and retention order provides additional structural information.

Previous work has suggested a potential structural dependence for the formation of oil- and water-soluble photoproducts from the simulated solar irradiation of petroleum. Aromatic species in petrol...

The physical properties of crude bio-oils preclude their direct use as fuel. Specifically, their high oxygen content results in undesirable acidity and poor thermal stability. Therefore, the remova...

Following the Deepwater Horizon (DWH) oil spill, the limited availability of the Macondo well oil prompted the use of a more widely available surrogate oil supplied by BP, collected from a nearby w...

International audience; Multiscale characterization of asphaltenes and their extrography fractions titrated withn-heptane was performed.Chemical characterization via FT-ICR MS and GPC ICP HR-MS, stability monitoring via QCR, and AFM images of depositsindicate that“island”-enriched samples tend to form fewer, well-organized deposit aggregates, whereas samples with abundant“archipelago”-like molecules produce larger aggregates and less well-organized deposits. The combination of QCR and AFM leads tothe conclusion that“island”-enriched samples lead to smaller deposits compared to“archipelago”-like molecules

The ability of molecular characterization to expose the chemical and structural composition of petroleum photooxidation products can aid future optimization of oil spill remediation techniques. Pre...

In petroleum science, asphaltenes are well-known as the most refractory fraction of crude oil and remain infamous for problems in production, transportation, and refining processes. Hence, they hav...

This study probes the nanoaggregation behavior of asphaltenes by gel permeation chromatography (GPC). Compounds containing sulfur, vanadium, and nickel were monitored online with elemental detectio...

The 2010 Deepwater Horizon disaster remains the largest single accidental release of oil and gas into the ocean. During the 87-day release, scientists used oceanographic tools to collect wellhead oil and gas samples, interrogate microbial community shifts and activities, and track the chemical composition of dissolved oil in the ocean’s interior. In the decade since the disaster, field and laboratory investigations studied the physics and chemistry of irrupted oil and gas at high pressure and low temperature, the role of chemical dispersants in oil composition and microbial hydrocarbon degradation, and the impact of combined oil, gas and dispersants on the flora and fauna of coastal and deep-sea environments. The multi-faceted, multidisciplinary scientific response to the released oil, gas and dispersants culminated in a better understanding of the environmental factors that influence the short-term and long-term fate and transport of oil in marine settings. In this Review, we summarize the unique aspects of the Deepwater Horizon release and highlight the advances in oil chemistry and microbiology that resulted from novel applications of emerging technologies. We end with an outlook on the applicability of these findings to possible oil releases in future deep-sea drilling locations and newly-opened high-latitude shipping lanes. The Deepwater Horizon disaster was the largest accidental discharge of oil into the environment, and was intensely studied during and after the event. In this Review, the subsequent advances made in oil chemistry, dispersant application, and microbiology are discussed.

Spilled oil is highly susceptible to sunlight-induced transformations, both as films on the surface of water and material dissolved or dispersed in the water column. We utilized ultrahigh-resolutio...

A recently developed extrography separation method fractionates petroleum asphaltenes based on their ionization efficiency, which correlates with polarity, aggregation tendency, and asphaltene stru...

The chemical composition of biomass-derived pyrolysis oils renders them undesirable for replacement of or blending with crude oils. The undesirable constituents result mainly from high oxygen content after pyrolysis, making oxygen the target for removal during subsequent upgrading. Catalytic hydrotreatment is the most common method for oxygen removal and can be performed during or after pyrolysis. The efficient removal of oxygen depends on its interaction with the catalyst, and therefore depends on the chemical composition of the oxygen-containing compounds. Knowledge of the oxygen composition before and after hydrotreatment provides insight into the removal process and possible applications for the upgraded oil. Here, we characterize an oak biocrude and its hydrotreated product by positive atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry to establish compositional changes that occur during hydrotreatment. A silica gel fractionation was also applied to enable separate analysis of the saturated and aromatic hydrocarbons from the hydrotreated pyrolysis oil.

International audience

Photodegradation is a significant weathering process that transforms spilled oil, yet, the fate, degradation rate, and molecular transformations that occur through photoinduced pathways remain relatively unknown. The molecular complexity combined with the increased polarity of photoproducts challenges conventional analytical techniques. Here, we catalogue the molecular progression of photochemical transformation products of Macondo Well Oil by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We track the molecular compositions of oil-soluble, interfacially-active, and water-soluble oil species formed at varying time intervals in photomicrocosm experiments. Short photoirradiation periods (24 h), not previously reported, are included to reveal rapid photooxidation of native oil components. Surface oil films exposed to solar irradiation were shown to increasingly contribute to the dissolved organic carbon pool as a function of increased irradiation time. FT-ICR MS analysis of acidic species of each fraction identifies tens of thousands of oil-soluble, interfacially-active, and water-soluble phototransformation products, including O

Because the rate of naphthenic acid corrosion does not correlate with the concentration of acids, it has been proposed that a subset of naphthenic acids in petroleum fractions may be more corrosive...

Asphaltene-related flow assurance problems are prevalent in oil production processes and are at the heart of issues such as the plugging of pipelines, the damage of rock formations, and the stabilization of viscous water-in-oil emulsions. A comprehensive understanding of the interfacial behavior of asphaltenes, from a physical–chemical perspective, is required for an accurate design of solutions to these challenges. In this work, we elucidate the deposition dynamics of various asphaltene subfractions in a porous media microfluidic model. Extrography fractions from the interlaboratory sample known as PetroPhase 2017 asphaltenes, reported to be a mixture of abundant island and archipelago motifs, and Wyoming deposit C7 asphaltenes, known for being island type dominated, are investigated. The deposition rate increases when the compositional ratio archipelago/island motif increases for PetroPhase 2017 derived fractions, whereas Wyoming deposit asphaltenes appear to exhibit stronger aggregation for fractions w...

Asphaltenes challenge nearly all analytical techniques because of their immense polydispersity in molecular composition and structure. This operationally defined fraction of crude oil, insoluble in n-alkanes but soluble in aromatic solvents, is known to concentrate in vacuum residues and islinked to fouling and deposition issues. However, presence and subsequent characterization of asphaltenes are seldom discussed in conventional/unconventional distillate fractions. Here, we isolate asphaltenes from conventional ( 593 °C) distillation cuts and provide molecular-level characterization by electrospray ionization and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry as a function of boiling point. Our results indicate that asphaltene molecular composition starts in the vacuum gas oil range and extends into vacuum residues. Moreover, we report that distillable asphaltene composition exists as both highly polar (heteroatom rich)...

Direct "dilute and shoot" mass spectral analysis of complex naturally-occurring mixtures has become the "standard" analysis in environmental and petrochemical science, as well as in many other areas of research. Despite recent advances in ionization methods, that approach still suffers several limitations for the comprehensive characterization of compositionally complex matrices. Foremost, the selective ionization of highly acidic (negative electrospray ionization ((-) ESI)) and/or basic (positive electrospray ionization ((+) ESI)) species limits the detection of weakly acidic/basic species, and similar issues (matrix effects) complicate atmospheric pressure photo-ionization (APPI)/atmospheric pressure chemical ionization (APCI) analyses. Furthermore, given the wide range of chemical functionalities and structural motifs in these compositionally complex mixtures, aggregation can similarly limit the observed species to a small (10-20%) mass fraction of the whole sample. Finally, irrespective of the ionization method, the mass analyzer must be capable of resolving tens-of-thousands of mass spectral peaks and provide the mass accuracy (typically 50-300 ppb mass measurement error) required for elemental composition assignment, and thus is generally limited to high-field Fourier transform ion cyclotron mass spectrometry (FT-ICR MS). Here, we describe three approaches to combat the above issues for (+) ESI, (-) ESI, and (+) APPI FT-ICR MS analysis of petroleum samples. Each approach relies on chromatographic fractionation to help reduce selective ionization discrimination and target either specific chemical functionalities (pyridinic and pyrrolic species (nitrogen) or carboxylic acids (oxygen)) or specific structural motifs (single aromatic core (island) or multi-core aromatics (archipelago)) known to be related to ionization efficiency. Each fractionation method yields a 2-10-fold increase in the compositional coverage, exposes species that are undetectable using direct "dilute and shoot" analysis, and provides coarse selectivity in chemical functionalities that can both increase the assignment confidence and optimize ionization conditions to maximize compositional coverage.

The 2010 explosion of the Deepwater Horizon (DWH) drilling rig provides a unique opportunity to advance the understanding of the evolution of lingering oil in Louisiana salt marshes for nearly a decade after the initial spill. After an oil spill, petroleum hydrocarbons undergo physical and chemical processes that transform the native oil composition to a polyfunctional oxygenated hydrocarbon matrix that contains ketones, hydroxyl, and carboxylic acid functional groups. Preliminary analysis of saltmarsh sediments impacted by the DWH spill between 2010–2014 identifies highly polar oxygenated hydrocarbons with carboxylic acid functionalities. These highly polar, high molecular weight compounds are not detectable by conventional gas chromatography (GC) based techniques. Here, we employ advanced analytical technologies such as targeted fractionation and isolation methods with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to document and catalog oil transformation compounds detected in oiled saltmarsh sediments. The toxicities of these environmental transformation products are determined by commercial Microtox bioassay. Samples have been continuously collected from 21 previously established sampling stations located in northern Barataria Bay for the past ten years post-spill. The concentration of oil contamination from heavily and moderately oiled sites exceed non-oiled reference sites for years after the spill. Combining chromatographic fractionation, conventional GC MS, and ultrahigh-resolution FT-ICR Mass Spectrometry analyses, we identified tens-of-thousands of biotic and abiotic crude oil transformation products that remain persistent and keep evolving in the environment. Heavily oxygenated transformation products, which are mostly only accessible by FT-ICR MS, span a wide range of chemical functionalities. Toxicity of the non-GC amenable fraction of oil contaminants was measured to determine the health risk of weathered oil residues left in the salt marsh environment. The current study creates a decade-long assessment record, and a comprehensive understanding of petroleum compounds evolution of oil-impacted wetlands ecosystem.

Oil is a complex mixture of alkanes, cycloalkanes, aromatics, nitrogen/sulfur/oxygen (N/S/O) heterocycles, alcohols, ketones, carboxylic acids, porphyrins, and myriad possible combinations therein. Once introduced into the environment, some weathering processes reduce this complexity through evaporative losses (loss to atmosphere) as well as water washing of low ring number aromatics, N/S/O heterocycles, alcohols, ketones, and carboxylic acids (loss to seawater). However, Gulf of Mexico Research Initiative (GoMRI) supported research has revealed that the contributions of these mechanisms to the reduction of molecular complexity are dwarfed by that of oxidative weathering processes (photo- and bio-oxidation) that increase the compositional complexity of the transformed oil. Because these oxidative processes increase the complexity of an already analytically challenging organic mixture and the boiling point of transformed species is higher than that of the precursors, conventional analytical techniques yield little insight into the identification of oil spill transformation products. Despite the challenge, recent advances in analytical science now allow molecular-level insight into these complex systems irrespective of initial (unaltered) or transformed-product boiling point; these advances were largely made possible by GoMRI supported research efforts. They expose a continuum of oxidized transformation products that span oil-soluble, oil-soluble interfacially-active, and water-soluble species. The isolation and characterization of oil-soluble, interfacially-active species confirm a long-standing theory that photo-oxidation generates oil-soluble surfactant-like species, which limit the effectiveness of dispersants. Furthermore, photo-oxidation specific microcosms are shown to generate unique species that are also found in field samples. Bio-oxidation only microcosms were found to generate very different, oil-soluble species; thus, photo-oxidation is implicated in the formation of transformation products in the field. Finally, analyses of photooxidized distillate cuts as well as asphaltene samples confirm prior reports of photo-induced polymerization and photo-cracking of native petroleum molecules. Here, we summarize the advances in the molecular-level understanding of oil over the past 8 years, in the context of oil spill science, by high resolution mass spectrometry, and we highlight potential opportunities for future research, as well as knowledge gaps that must be addressed for future spills.

International audience; Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has exposed the ultracomplexity of fossil fuels, thereby validating the compositional trends that rule petroleum distillation, known as the Boduszynski Continuum. Routine FT-ICR MS analysis of a single crude oil sample can reveal tens-of-thousands of unique molecular formulas; however, currently available ionization methods suffer from limitations for such complex mixtures that are not yet completely understood. Simply put, MS detects ions, and thus, it depends heavily on the ability of ion sources to indiscriminately volatilize and subsequently ionize samples of interest. Despite advances in soft ionization methods, the characterization of complex matrices remains a challenge due to the lack of an ion source, commercial or custom-built, that can vaporize and ionize all compounds without bias, save analyte concentration. However, atmospheric pressure photoionization (APPI) has been shown to provide the most uniform ion production for mixtures of petroleum model compounds and real samples, with little to no fragmentation. In this work, we investigated the molecular composition of PetroPhase 2017 asphaltenes and its extrography fractions, with a focus on the total vanadium content and molecular composition of vanadyl porphyrins as a function of aggregate size distribution, accessed through separate experiments: online gel permeation chromatography (GPC) inductively coupled plasma-MS (ICP-MS) and online GPC APPI FT-ICR MS (at 21 T). The results reveal that the extrography separation provides asphaltene fractions (i.e., acetone, Hep/Tol, and Tol/THF/MeOH) enriched in 51V-containing compounds with distinctive aggregate size distributions. The acetone fraction features smaller aggregate sizes, as it elutes later in the GPC chromatogram than Hep/Tol and Tol/THF/MeOH fractions, and overall, presents up to ∼14-fold higher ionization efficiency in APPI. Such behavior suggests a correlation between aggregate size and production efficiency of monomeric ions in APPI. Bulk compositional trends accessed by GPC separation and highlighted by ICP-MS detection indicate that despite multiple separation steps (i.e. extrography followed by GPC), APPI FT-ICR MS can only access ∼37% of the total V-containing compounds. Although the more stable/larger aggregates dominate the size distributions of all asphaltene samples studied, it is the weakly aggregated/monomeric species that are preferentially observed by APPI-MS. Tendencies in the molecular composition of vanadyl porphyrins and S/O-containing compounds strongly suggest that London forces might be central in the self-assembly process of asphaltene nanoaggregates to produce more massive clusters. The results demonstrate that the observed compositional trends (albeit limited) can be accessed when coupling advanced chromatographic separations with online high-field FT-ICR MS detection.

Despite extensive research, the molecular-level chemical characterization of asphaltenes, a highly aromatic solubility fraction of petroleum, remains an analytical challenge. This fraction is related to diverse problems in crude oil exploration, transportation, and refining. Two asphaltene architecture motifs are commonly discussed in literature, “island” (single core) and “archipelago” (multicore) type structures. The thermal desorption and pyrolysis behavior of island- and archipelago-enriched as-phaltenes and their extrography fractions was investigated. For this purpose, the evolved chemical pattern was investigated by thermal analysis coupled to ultrahigh resolution mass spectrometry (FT-ICR MS). Soft atmospheric pressure chemical ionization preserved the molecular information of the thermal emission profile. Time/temperature-resolved analysis allowed the chemical characterization of occluded material as well as of asphaltene building blocks during pyrolysis.Regarding the thermogravimetric information, the island-type enriched sample (Wyoming asphal-tenes) revealed a significantly higher coke residue after the pyrolysis process compared to the archi-pelago-type enriched sample (Athabasca asphaltenes). In contrast to whole asphaltenes, extrograph-ic fractions revealed occluded material evolved during the desorption phase. For the acetone frac-tion, this effect was most abundant and suggests cooperative aggregation.Pyrolysis revealed a bimodal behavior for most of the compound classes suggesting the presence of both architecture motifs in each asphaltene. DBE versus #C diagrams of the pyrolysis molecular pro-file revealed specific compositional trends: compounds with high DBE values and short alkylation likely to be originated from island-type asphaltenes, whereas species with low DBE values and high carbon numbers likely derive from archipelago-type asphaltenes.In the asphaltene structural debate, thermal analysis ultrahigh resolution mass spectrometry serves as additional technique and supplements results obtainable by other techniques, such as direct infu-sion approaches. Consistent results on the structural motifs are indicated by the molecular finger-print visualized by DBE versus #C diagrams and serve as measure for the dominance of a structural motif.

International audience; Asphaltenes are among the most challenging components in petroleum processing because they contain high amounts of heteroatoms (i.e., S, N, O, V, and Ni) thought to be responsible for strong aggregation tendencies, precipitation, and fouling problems. The role of vanadium- and nickel-containing petroleum compounds (i.e., petroporphyrins) in aggregation and fouling is not completely understood because asphaltene composition and structure is still a subject of debate in the petroleum chemistry community. Characterization of asphaltenes, namely, molecular analysis that employs no chromatographic separation, often fails to reveal their comprehensive composition. The work herein presents asphaltene fractionation by (1) solid/liquid extraction, which allows for separation of single-core (“island”) and multicore (“archipelago”) structural motifs and by (2) high-performance thin layer chromatography (HPTLC) with cellulose as the stationary phase and DCM/MeOH as the eluent, which facilitates access to petroporphyrins. Characterization is performed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI FT-ICR MS). The results demonstrate that even with multiple separation steps, a large quantity of vanadyl porphyrins remains inaccessible for molecular analysis by MALDI FT-ICR MS, which raises the question of what portion of a complex sample of asphaltene can be revealed by ultrahigh resolution mass spectrometry. Furthermore, the results show that easily accessible porphyrins migrate with the solvent front in HPTLC. Thus, HPTLC can be used to isolate and identify “free” porphyrins not locked into asphaltene aggregates; however, further development of separation methods is required to access the most difficult and problematic asphaltene fractions, which do not migrate and impose analytical challenges due to their stronger aggregation tendency.

Asphaltenes are high-boiling and recalcitrant compounds that are generally minor components of crude oil (∼0.1-15.0 wt %) but dominate the composition of heavily weathered spilled petroleum. These solid residues exhibit a high structural complexity, comprised of polycyclic aromatic hydrocarbons (PAHs) that are a mixture of single-core (island) and multicore (archipelago) structural motifs. The mass fraction of each motif is sample-dependent. Thus, knowledge of a potential structural dependence (single- versus multicore) on the production of water-soluble species from asphaltene samples is key to understanding the contribution of photochemically generated dissolved organic matter from oil spills. In this work, asphaltene samples with enriched mass fractions of either island (single-core) or archipelago (multicore) structural motifs are photo-oxidized on artificial seawater by the use of a solar simulator. Molecular characterization of oil- and water-soluble photoproducts, conducted by Fourier transform ion cyclotron resonance mass spectrometry, reveals that island motifs exhibit very limited production of water-soluble species, and their oil-soluble products reflect the molecular composition of the starting material. Conversely, archipelago motifs yield a water-soluble compositional continuum of O

Road asphalt is comprised of aggregate (rocks) mixed with a binder composed of high-boiling petroleum-derived compounds, which have been thought to be relatively inert (unreactive) and thus leach small amounts of polyaromatic hydrocarbons (PAHs) into water from the built environment. However, recent studies have demonstrated that petroleum readily undergoes photooxidation and generates water-soluble oxygen-containing hydrocarbons. Therefore, here, we investigate the effects of solar irradiation on an asphalt binder. Upon irradiation in a photooxidation microcosm, thin films of the asphalt binder produce abundant oil- and water-soluble oxygenated hydrocarbons, which we hypothesize are also leached from roads and highways through photooxidation reactions. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) enables extensive compositional characterization of the virgin asphalt binder, irradiated asphalt binder, and the water-soluble photoproducts. The results reveal the production of water-soluble species that resemble the molecular composition of petroleum-derived dissolved organic matter, including abundant hydrocarbons and S-containing species with up to 18 oxygen atoms. The results also confirm photo-induced oxidation, fragmentation, and potentially polymerization as active processes involved in the production of water-soluble organic pollutants from asphalt.

Asphaltene structure is one of the most controversial topics in petroleum chemistry. The controversy is centered on the organization of aromatic cores within asphaltene molecules (single aromatic core, island and multiple aromatic core, archipelago) and specifically the inconsistency between the island model and the composition of the products derived from asphaltene pyrolysis/thermal cracking. Such products are consistent with the coexistence of island and archipelago asphaltene structural motifs. However, the archipelago model continues to lack the widespread acceptance of the petroleum community, in part due to mass spectrometry results in support of the island model. In the first and second part of this series, we demonstrated that the disproportionally high atmospheric pressure photoionization (APPI) ionization efficiency (monomer ion yield) of island species is due to weak nanoaggregation of large aromatic cores which do not extensively aggregate in toluene, whereas more archipelago-dominant fractio...

Hydrocarbon-rich pyrolysis oils produced from landfill waste and recycled plastics are potential sources for fuels and chemicals. It is well established that feedstock composition significantly affects pyrolysis oil composition and, hence, its potential uses. For example, plastics waste pyrolysis oils contain a high concentration of hydrocarbons, whereas biomass pyrolysis oils have high oxygen content. Previous studies have shown that the addition of plastics to a biomass feedstock increases the hydrocarbon content; however, a detailed analysis of hydrocarbons and polar species from pyrolysis oils produced from “real world” mixed municipal waste materials has not yet been done. Here, the silica gel fractions from unsorted landfill waste and mixed recycled plastics pyrolysis oils are analyzed by two-dimensional gas chromatography (GC × GC), field ionization mass spectrometry (FI-MS), Fourier transform infrared spectroscopy (FT-IR), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS)...

Since the emergence of high resolving power crude oil mass spectrometry two decades ago, hundreds of publications and presentations have detailed petroleum complex mixtures by electrospray ionization (ESI) mass spectrometry (MS). None of these works have reported or detailed ion suppression (also referred to as ionization biasing or matrix effects) which is a well-known feature of ESI. Here, we show the extreme consequences of ionization biasing within a narrow, 1 order of magnitude concentration range for crude oil mixture direct infusion experiments in positive ion (+) ESI. An oil spill contaminant, a crude oil, and an equimolar model compound mixture were electrosprayed at various analyte and acid modifier concentrations for Fourier transform ion cyclotron resonance (FT-ICR) and time-of-flight (TOF) MS analysis. A 3-fold increase in the number of elemental compositions is achieved by optimization of analyte and acid concentration. At high analyte concentration, oxygen heteroatom class (i.e., CcHhOx spe...

Following the Deepwater Horizon (DWH) blowout in 2010, oil floated on the Gulf of Mexico for over 100 days. In the aftermath of the blowout, substantial accumulation of partially oxidized surface oil was reported, but the pathways that formed these oxidized residues are poorly constrained. Here we provide five quantitative lines of evidence demonstrating that oxidation by sunlight largely accounts for the partially oxidized surface oil. First, residence time on the sunlit sea surface, where photochemical reactions occur, was the strongest predictor of partial oxidation. Second, two-thirds of the partial oxidation from 2010 to 2016 occurred in less than 10 days on the sunlit sea surface, prior to coastal deposition. Third, multiple diagnostic biodegradation indices, including octadecane to phytane, suggest that partial oxidation of oil on the sunlit sea surface was largely driven by an abiotic process. Fourth, in the laboratory, the dominant photochemical oxidation pathway of DWH oil was partial oxidation to oxygenated residues rather than complete oxidation to CO

A “volcano” plot provides a visual means for identifying statistically significant differences between two populations. Here, we introduce the volcano plot as a means for simple, visual identification and statistical ranking of compositional differences between petroleum crude oils. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry yields the relative abundances of ions in each spectrum that contains up to tens of thousands of elemental compositions (CcHhNnOoSs). From that data, a volcano plot may be generated by plotting statistical significance (p-value, obtained from t test) versus log2(relative abundance ratio). The volcano plot data may be color-coded to highlight differences in heteroatom class (NnOoSs), double bond equivalents (DBE = number of rings plus double bonds to carbon), and/or carbon number. The volcano plot may be used either directly or as a “filter” for including only the most statistically significant differences for data entered into more conventional an...

We describe complex organic mixture analysis by 21 tesla (T) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Ultrahigh mass-resolving power (m/Δm50% > 2 700 000 at m/z 400) and mass accuracy (80 ppb rms) enable resolution and confident identification of tens of thousands of unique elemental compositions. We demonstrate 2.2-fold higher mass-resolving power, 2.6-fold better mass measurement accuracy, and 1.3-fold more assigned molecular formulas compared to our custom-built, state-of-the-art 9.4 T FT-ICR mass spectrometer for petroleum and dissolved organic matter (DOM) analyses. Analysis of a heavy petroleum distillate exemplifies the need for ultrahigh-performance mass spectrometry (49 040 assigned molecular formulas for 21 T versus 29 012 for 9.4 T) and extends the identification of previously unresolved Oo, SsOo, and NOo classes. Mass selective ion accumulation (20 Thompson isolation) of an asphalt volcano sample yields 462 resolved mass spectral peaks at m/z 677 and reveals pre...

Advances in high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) enable molecular-level characterization of ultracomplex asphaltene samples. Such analyses most often reveal compounds that are highly aromatic but alkyl-deficient in nature and, thus, support the classical “island” model of asphaltene architecture. However, recent works that combine chromatographic separations with mass spectrometry for the analysis of crude oils have shown that differences in ionization may greatly affect the analysis of complex mixtures (known as the matrix effect). Simply, compounds that ionize with greater efficiency are preferentially observed and mask the detection of poorly ionized compounds. Asphaltenes are not immune to this phenomenon. In the first of this series (10.1021/acs.energyfuels.7b02873), it was demonstrated that asphaltenes generated by different precipitants showed greatly varied monomer ion yields (ionization efficiencies). This work focuses on the development of an ex...

For decades, discussion of asphaltene structure focused primarily on molecular weight. Now that it is widely accepted that asphaltene monomers are between ∼250 and 1200 g/mol, disagreement has turned to asphaltene architecture. The classic island model depicts asphaltenes as single core aromatic molecules with peripheral alkyl side chains, whereas the less widely accepted archipelago model, includes multiple aromatic cores that are alkyl-bridged with multiple polar functionalities. Here, we analyze asphaltene samples by positive-ion atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry and perform infrared multiphoton dissociation to identify their aromatic core structures to shed light on the abundance of island and archipelago structural motifs. Our results indicate that island and archipelago motifs coexist in petroleum asphaltenes, and unlike readily accessible island motifs, asphaltene purification is required to detect and characterize archipelago species b...

The herein described High Performance Liquid Chromatography (HPLC) platform (termed HPLC-3) combines a complex solvent gradient with two electron acceptor columns to provide aromatic ring class (ARC) separation for heavy oils. The separation yields seven major fractions: saturates, monoaromatics (1 ring), diaromatics (2 rings), triaromatics (3 rings), tetra-aromatics (4 rings), polyaromatics and polars (5+ polars), and aliphatic sulfides. The system utilizes a photodiode array detector (PDA) for online measurements of aromaticity in series with an evaporative light scattering detector (ELSD) to provide improved quantitative mass determination across the entire solvent gradient. A new postcolumn dilution strategy was successfully utilized to compensate for solvent effects on the ELSD signal. The method allows for calibration across the entire HPLC-3 solvent gradient and simultaneously diverts ∼90% of the sample effluent for fraction collection and further characterization. In addition to the major ARC frac...

Here, we present atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance (FTICR) mass analysis of a volcanic asphalt sample by acquiring data for 20 Da wide mass segments across a 1000 Da range, stitched into a single composite mass spectrum, and compare to a broad-band mass spectrum for the same sample. The segmented spectrum contained 170 000 peaks with magnitude greater than 6σ of the root-mean-square (rms) baseline noise, for which 126 264 unique elemental compositions could be assigned. Approximately two-thirds of those compositions represent monoisotopic (i.e., chemically different) species. That complexity is higher than that for any previously reported mass spectrum and almost 3 times greater than that obtained from the corresponding broad-band spectrum (59 015). For the segmented mass spectrum, the signal-to-noise ratio (S/N) was significantly higher throughout the spectrum, but especially at the lower and upper ends of mass distribution relative to that of the near-Gaussian broad-band mass distribution. Despite this S/N improvement, mass measurement accuracy was noticeably improved only at lower masses. The increased S/N did, however, yield a higher number of peaks and higher dynamic range throughout the entire segmented spectrum relative to the conventional broad-band spectrum. The additional assigned peaks include higher heteroatom species, as well as additional radicals and isotopologues. Segmenting can require a significant investment in data acquisition and analysis time over broad-band spectroscopy (∼1775% in this case) making it best suited for targeted analysis and/or when complete compositional coverage is important. Finally, the present segmented spectrum contains, to our knowledge, more assigned peaks than any spectrum of any kind (e.g., UV-vis, infrared, microwave, magnetic resonance, etc.).

Corrosion control at refineries remains a challenge because the mechanism of naphthenic acid (NAP) corrosion is still not fully understood. The rate of NAP corrosion does not correlate with acidity (as measured by total acid number); therefore, it has been suggested that a subset of NAP in petroleum fractions may be more corrosive than others. Because the primary corrosion product (iron naphthenates) may thermally decompose to ketones at corrosion temperatures (250–400 °C), ketones in corrosion fluids could potentially be used to implicate specific problematic acids in corrosion tests. To that end, we have developed a method for isolating and characterizing ketones in corrosion test solutions. Ketones from tests on palmitic and 4-cyclohexyl pentanoic acids (C16H32O2 and C11H20O2) have been successfully isolated with a strong anion exchange solid-phase separation. Gas chromatography/mass spectrometry identifies ketones formed as a result of model acid corrosion. Fourier transform ion cyclotron resonance ma...

The acidic components of Athabasca bitumen interfacial material (IM) were isolated and subsequently fractionated based on hydrophobicity by a modified aminopropyl silica (MAPS) method to determine whether low-molecular-weight IM acids are preferentially ionized in negative-ion electrospray ionization (ESI (−)) and, thus, bias the compositional information obtained by direct infusion (dilute and shoot) mass spectral analysis. Characterization by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed that MAPS fractionation of IM acids extends the detection of high-m/z (>600-Da) IM compounds by 2-fold, yields an approximate 10-fold increase in the number of assigned formulas, and exposes a continuum of acidic species that includes the first definitive identification of doubly charged acids in interfacial material. Comparison of the heteroatom contents of singly and doubly charged Ox species, combined with the acid-targeted extraction procedure, ...

Petroleum emulsion interfacial material (species that reside in the water/oil interface) are believed to be responsible for stabilizing emulsions in petroleum; therefore, their characterization can help to develop strategies to mitigate/manipulate petroleum emulsions. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has shown that the species present at the oil/water interface are enriched in sulfur- and oxygen-containing functionalities. However, structural and isomeric information about the chemical functionalities is still uncertain. Here, we demonstrate the potential of ion mobility mass spectrometry (IM-MS) combined with post-ion mobility collision-induced dissociation (post-IM CID) to characterize functional isomers in petroleum emulsion interfacial material. Interfacial material was isolated from Athabasca bitumen and a heavy crude oil by the wet silica method. IM time-of-flight (TOF) MS analysis shows the presence of multiple isomeric O3S1 species in both samples. Post-IM CI...