Double Bond Equivalent Values Research Articles

Molecular characterization on the fractionation of organic phosphorus induced by iron oxide adsorption using ESI-FT-ICR MS

The interaction between organic phosphorus (OP) and iron oxide significantly influences the phosphorus cycle in the natural environment. In shallow lakes, intense oxidation-reduction fluctuations constantly alter the existing form of iron oxides, but little is known about their impact on the adsorption and fractionation of OP molecules. In this study, electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS) was used to investigate the fractionation of OP from alkali-extracted sediment induced by crystalline goethite and amorphous ferrihydrite adsorption at a molecular scale. The results showed that ferrihydrite and goethite both exhibited high OP adsorption, and the adsorption amount decreased as the pH increased. The adsorption kinetics matched the pseudo-second-order equation. The ESI-FT-ICR MS analysis showed that 91 P-containing formulas were detected in the alkaline-extracted sediment solution. Ferrihydrite and goethite adsorbed 51 and 24 P-containing formulas, respectively, with adsorption rates of 56.0 % and 26.4 %. Ferrihydrite could adsorb more OP compounds than goethite, but no obvious molecular species selectivity was observed during the adsorption. The P-containing compounds, including unsaturated hydrocarbons-, lignin/carboxyl-rich alicyclic molecule (CRAM)-, tannin-, and carbohydrate-like molecular compounds, were more suitable for iron oxide adsorption. The double bond equivalence (DBE) is a valuable parameter that indicates OP fractionation during adsorption, and P-containing compounds with lower DBE values such as lipid- and protein-like molecular were prone to remain in the solution after adsorption. These research results provide insights into the biogeochemical cycling process of P in the natural environment.

Analysis of the microstructure of high viscosity components in Tahe ultra heavy oil based on the combination of ESI (±) FT-ICR/MS

In addressing the challenge of high viscosity in Xinjiang Tahe heavy oil, crucial for optimizing extraction processes, this study focuses on identifying and analyzing the microstructure of key components influencing oil viscosity. The aim is to uncover the underlying reasons for its high viscosity and guide research towards effective viscosity reduction techniques. Electrospray ionization (ESI) combined with fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS) characterizes the molecular-level constituents contributing to oil viscosity. The investigation covers the composition and distribution of oxygen-containing, nitrogen-containing, and organometallic compounds, developing a molecular structure model for these critical viscosity-inducing components. Findings reveal Xinjiang Tahe extra heavy oil as a solid mass at room temperature, with significant viscosity reduction observed post-deasphalting, highlighting asphaltenes' pivotal role in viscosity. Analysis indicates a higher content of metal elements (such as V and Ni) in asphaltenes compared to the crude oil itself, with an abundance of porphyrin structures in asphaltenes markedly influencing oil viscosity. Cyclic, aromatic, and unsaturated compound structures are predominantly found in the asphaltenes of heavy oil. Through combined ESI (±) FT-ICR/MS analysis, the crude oil is determined to mainly comprise acidic compounds, non-basic nitrogen compounds, and basic nitrogen compounds, offering significant insight into heavy oil's complex chemical composition. Specifically, non-basic nitrogen compounds in Tahe crude oil, including alkylcarbazoles, alkylbenzocarbazoles, and alkylpolybenzocarbazoles, are identified as key components, with molecular carbon numbers ranging from C12 to C56 and a predominance near C27. Additionally, asphaltenes in Tahe heavy oil exhibit a higher double bond equivalence (DBE) than the crude oil, indicating a greater degree of condensation with an increased number of double bonds and heterocyclic structures. The significant difference in DBE values between asphaltenes and crude oil underscores their impact on viscosity. A detailed molecular structure model of the asphaltenes in Tahe extra heavy oil has been constructed based on FT-ICR/MS analysis, providing a foundational understanding for developing viscosity reduction strategies.

Characterization of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particles (PM2.5) in the North China Plain using positive-ion atmospheric pressure photoionization (APPI) coupled with fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS)

Many aromatic compounds, including 16 types of U.S. EPA priority PAHs, exist in substituted or unsubstituted forms and have high toxicities. Aromatic compounds in aerosols collected in the North China Plain (NCP) were characterized by GC-MS and atmospheric pressure photoionization (APPI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). The concentrations of the 16 types of PAHs in the collected samples ranged from 277.0 to 876.8 ng/m3, which were higher than those collected in other regions and countries. Previous studies reported that only 27 wt% of aromatic compounds could be eluted using the GC system and demonstrated that APPI FT-ICR MS is a useful method for identifying large-molecular aromatics. In this study, two samples collected from the NCP were successfully characterized by APPI FT-ICR MS. In the APPI + mode, 231 and 228 CH formulas (containing only C and H and having a double bond equivalent (DBE) of 4 or greater) were identified, accounting for 10% of the numerical fraction and more than 40% of the intensity fraction. The FT-ICR data revealed that condensed PAHs with 6–8 aromatic rings had relatively high abundances and that a series of PAH homologs (alkylated PAHs) with identical DBE values ranging from 4 to 30 were present. Furthermore, heteroatom groups were also identified as significant components of the aromatic fractions. The O1, O2, N1, NO2, and S1 class species with DBE values of 3–34 and carbon numbers of 11–42 were identified by APPI FT-ICR MS. The heteroatom PAHs had DBE values and carbon number distributions similar to regular PAHs. The aromatic fractions determined in this work provide useful data for future quantitative analyses of aromatic compounds with high toxicities and our findings will help improve the current understanding of PAH compositions in the northern China. However, further research is needed to determine the abundances and toxicities of various apparent or substituted PAHs outside of the 16 types identified by the U.S. EPA as priority PAH compounds, which have been extensively researched.

Oxidation treatment of shale gas produced water: Molecular changes in dissolved organic matter composition and toxicity evaluation

Produced water (PW) is the largest waste stream generated by hydraulic fracturing in an unconventional shale gas reservoir. Oxidation processes (OPs) are frequently used as advanced treatment method in highly complicated water matrix treatments. However, the degradation efficiency is the main focus of research, organic compounds and their toxicity have not been properly explored. Here, we obtained the characterization and transformation of dissolved organic matters of PW samples from the first shale gas field of China by two selected OPs using FT-ICR MS. CHO, CHON, CHOS, and CHONS heterocyclic compounds associated with lignins/CRAM-like, aliphatic/proteins, and carbohydrates compounds were the major organic compounds identified. Electrochemical Fe2+/HClO oxidation preferentially removed aromatic structures, unsaturated hydrocarbons, and tannin compounds with a double-bond equivalence (DBE) value below 7 to more saturated compounds. Nevertheless, Fe (VI) degradation manifested in CHOS compounds with low DBE values, especially single bond compounds. Oxygen- and Sulfur-containing substances, primarily O4–11, S1O3-S1O12, N1S1O4, and N2S1O10 classes, were the main recalcitrant components in OPs. The toxicity assessment showed that the free-radical-formed Fe2+/HClO oxidation could cause significant DNA damage. Therefore, the toxicity response byproducts need spcial attention when conducting OPs. Our results led to discussions on designing appropriate treatment strategies and the development of PW discharge or reuse standards.

Qualitative characterization of nitrogen-containing compounds in jet and diesel fuel extracts by using (+) electrospray ionization coupled to a linear quadrupole ion trap/orbitrap mass spectrometer

The development of analytical methods for the characterization of nitrogen-containing compounds (NCCs) in liquid transportation fuels are critical, as these compounds adversely affect fuel storage and thermal stability. In this work, (+) electrospray ionization coupled to a linear quadrupole ion trap/orbitrap mass spectrometer provided detailed chemical analysis of the NCCs in jet and diesel fuels. Upon methanol extractions of the individual fuels (three jet fuels and one diesel), the methanol layer was diluted and injected into the ESI source where protonation was the dominant ionization reaction for the NCCs, which exhibited little to no fragmentation. Kendrick mass defect plots were constructed to facilitate chemical characterization. Many chemical classes of NCCs (i.e., alkylamines, pyridines, indoles, quinolines, carbazoles) were identified in the jet and diesel fuel extracts. Compositional differences were observed when the jet fuel extracts were compared to each other and when compared to the diesel extract. For example, the most abundant NCCs in Jet fuel 1 had empirical formulas of CnH(2n)N (decahydroquinolines/decahydroisoquinolines) and CnH(2n-6)N (indolines/tetrahydroquinolines/tetrahydroisoquinolines). Conversely, the most abundant NCCs in Jet fuel 2 had empirical formulas of CnH(2n-6)N and CnH(2n-10)N (quinolines/isoquinolines/naphthylamines) while the most abundant NCCs in Jet fuel 3 had empirical formulas of CnH(2n+4)N (alkylamines). The ionized NCCs derived from the jet fuels had wider carbon number ranges than compared to those reported in previous studies. The average molecular weights, ring and double bond equivalent values and total carbon numbers for the ionized NCCs in the four extracts ranged from 192.8–215.3 Da, 1.7–5.0 and 13.5–14.8, respectively. Further, the average carbon number for each homologue ion series (ions with the same empirical formula but differ by 14 Da) were determined. Collision-activated dissociation was also investigated to evaluate its efficacy at providing structural elucidation and isomeric differentiation for ionized NCCs. Overall, the high-resolution mass spectrometry measurements provided thorough chemical characterization that may aid in linking NCC compositions to storage and thermal stability failures and advance the current understanding of issues concerning fuel incompatibility upon the mixing of different fuels.

Composition of sulfur species in deasphalted oils and their molecular-level transformation during the hydrotreating process

• DAOs are separated into subfractions combining methylation and solvent extraction. • HDS chemistry of DAOs is unraveled by combining conversion and composition analysis. • Sulfides and thiophenes have similar reactivity but different evolution chemistry. • Polar fractions are refractory due to the unreactivity and inhibitors existing in them. The sulfur removal chemistry is critical to the efficient conversion of heavy oils. The compositions and HDS reactivities of sulfur-containing compounds in two deasphalted oils were systematically investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) combined with a self-established separation method. The deasphalted oils are separated into three subfractions by a combination of methylation/demethylation and solvent extraction. The S1 class sulfur compounds with low and high DBE (double bond equivalent) values dominated the sulfidic and thiophenic subfractions, respectively, while polyheteroatomic compounds are the major components in the polar subfractions. Three sulfur subfractions exhibited different reactivities under the same hydrotreating conditions. The sulfidic and thiophenic subfractions have similar HDS reactivities, and the sulfur species with low and high DBE values are preferentially removed from the above subfractions, respectively. Sulfur compounds in the polar subfractions are the least reactive species, resulting from the existed unreactive sulfur components and the inhibition of polyaromatics and nitrogen-containing compounds. This study represents an advance in unraveling the complex desulfurization chemistry in heavy oils, and facilitates the development of superior hydrodesulfurization catalysts.

Biodegradation levels of oils from the Chepaizi Uplift, Junggar Basin (NW China) evaluated by a full-range biodegradation index as constrained by adamantane, diamantane homologs and carboxylic acids

Biodegradation usually masks or even radically alters the original characteristics of molecular biomarkers, restricting the oil sources identification and the exploration of ultra-heavy oils (also known as oil sands, tar sands, asphalt or bitumen). The oils from the Lower Neogene Shawan Formation (N1s), Lower Cretaceous Tugulu Group (K1tg), and Upper Carboniferous Xibeikulasi Formation (C2x) in the Chepaizi Uplift, Junggar Basin (NW China) were biodegraded to different extent, consequently, many commonly used biomarker parameters became less powerful for the evaluation of the extent of biodegradation. To address this problem, the resistance of many adamantane and diamantane homologs and carboxylic acids to biodegradation was analyzed, and those with high bioresistance were selected to yield a more precise and extensive characterization of biodegradation from light to extreme. In contrast, oils from the eastern Chepaizi Uplift were generated from Permian sources, and have been subjected to heavy to extreme levels of biodegradation. In this study, fifteen oil samples obtained from the Chepaizi Uplift were analyzed by a set of mass spectrometric techniques. The results were applied to investigate the variations of commonly used biomarkers in the saturates and aromatics, to qualitatively rank oil biodegradation levels based on the PM scale and to provide a detailed assessment of the variation in carboxylic acids and adamantane and diamantane homologs in heavy oils from varying degrees of biodegradation. The results demonstrate that adamantane and diamantane homologs with various methyl groups, and carboxylic acids with various double bond equivalents (DBEs), exhibit an intact homolog series distribution and certain hypermethylation trend as biodegradation levels progress from light to extreme, which confirmed their reliability in refining the evaluation scale and characterizing the extent of biodegradation. In addition, the full-range biodegradation index (FRBI) presented here consists of the ratios of adamantane/diamantane homologs with different numbers of methyl substituents and the ratios of carboxylic acids with different DBE values, instead of the five Manco scores of 0–4 used previously, which can effectively improve the ranking precision of biodegradation of oils between subtle alteration changes, and universally unraveling to the full range of biodegradation, beginning from light to extreme.

Molecular insight into the release of phosphate from dissolved organic phosphorus photo-mineralization in shallow lakes based on FT-ICR MS analysis

Dissolved organic phosphorus (DOP) is a key factor in the water eutrophication process because of its high potential bioavailability and inorganic phosphate (Pi) compensation ability through bio- and photo-mineralization. However, the research on the characterization and transformation of DOP is insufficient owing to their complex composition. This study investigates the release of dissolved Pi from DOP photo-mineralization in Lake Dong based on Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. The results showed that the photo-release of dissolved Pi is spatially heterogeneous in Lake Dong and is consistent with the distribution of DOP concentration. The FT-ICR MS results showed that the simulated irradiation decreased the relative abundance (RA) of the DOP molecular formulae with higher molecular weight (MW) and higher double bond equivalence values (DBE), while the RA of DOP molecular formulae with lower MW and lower DBE value increased or remained. Besides, the total RA of lipid-like formulae increased from 49.09% to 55.90%, while the oxy-aromatic-like formulae decreased from 50.91% to 44.10%, suggesting that simulated irradiation would influence the potential bioavailability of DOP. As the main photolysis medium during DOP photo-mineralization, the hydroxyl radicals (∙OH) are mainly derived from dissolved organic matter (DOM) compared to the nitrate (NO3−) and iron ion (Fe3+) in Lake Dong. These results are important in understanding the ability and mechanism of DOP photo-mineralization and provide suggestions for cycling phosphorus in eutrophic shallow lakes.

Molecular Characterization of Polar Compounds in Crude Oil Affecting Sandstone Wettability Revealed by Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry

Summary Knowing the composition, molecular size, and structure of polar compounds in crude oil that affect sandstone wettability is a prerequisite for a better understanding of oil/rock/brine interactions and for better application of enhanced oil recovery (EOR) techniques to increase recovery factors and improve the economic efficiency of field development. The nitrogen-, sulfur-, and oxygen-containing polar compounds in crude oil are key factors for sandstone wettability changes. In this study, an outcrop sandstone core selected from Jurassic formation in Sichuan Basin, China, was aged by crude oil to restore the wettability after being cleaned by hot Soxhlet extraction with an azeotropic solvent mixture of methanol and dichloromethane (MDC, vol/vol = 7:93). Then, Amott-Harvey experiments that were conducted by combining spontaneous imbibition and forced displacement steps of coreflooding were performed to characterize sandstone wettability after it was cut into four core blocks. The wettability index (IA-H) of four core blocks from the inlet to outlet of oil flooding were −0.523, 0.214, −0.087, and −0.861, respectively, which illustrated different degrees of sandstone wettability. The extracts of three sequential hot Soxhlet extraction steps of four core blocks were analyzed by gas chromatography-mass spectrometry (GC-MS) and high-resolution Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) combined with electrospray ionization (ESI) in negative ion mode. Almost no polar compounds were detected in the n-hexane extracts, and a total of seven classes of different polar molecular compounds—namely, N1, N1O1, N1S1, O1, O2, O3, and O4—were detected in dichloromethane (DCM) and MDC extracts. The relative abundances of the N1S1 and O1 classes in the extracts of DCM and MDC were too low to be ignored. Compared to those of polar compounds in DCM extracts, the relative abundance of neutral nitrogen compounds (N1 and N1O1 classes) in the MDC extracts decreased significantly. In contrast, the acidic compounds (O2, O3, and O4 classes) all showed an obvious increase in the MDC extracts compared to the DCM extracts. It was notable that most of the polar compounds in MDC extracts were O2 and O3 compounds with double bond equivalent (DBE) values = 1 from the perspective of DBE distribution. The proportion of these two compound classes was much higher than that of all other polar compounds. Therefore, we believe that these two compound classes are the decisive factors for changing sandstone wettability combined with previous studies. In addition, based on the number of oxygen atoms and DBE values, we inferred that the O2 (DBE = 1) class was the long-chain saturated fatty acids and that the O3 (DBE = 1) class was the hydroxyl acids containing both one carboxyl and one hydroxyl group. Furthermore, the final determination of the wettability degree of the sandstone surface was the amount of all polar compounds, not only the relative abundance of these two types of acids. These two types of acids in crude oil were equivalent to anchor molecules on the surface of sandstone, and other polar compounds were adsorbed onto their surface to make the sandstone preferentially oil-wet.

Molecular Characterization of NSO Compounds and Paleoenvironment Implication for Saline Lacustrine Oil Sands by Positive-Ion Mass Spectrometry Coupled with Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry.

NSO compounds mainly exist in geological bodies in the form of nonhydrocarbons and asphaltenes with abundant geological and geochemical information. Combined with the gas chromatography mass spectrometry (GC–MS) technology, positive-ion electrospray ionization Fourier-transform ion cyclotron resonance MS (FT-ICR MS) was used to understand the composition and distribution characteristics of NSO compounds in the oil sands of the Dongpu Depression and to explore their paleoenvironmental significance. The results show that n-alkanes are characterized by an even carbon number and phytane dominance, suggesting a saline lacustrine environment. Certain abundance of nC37 and β-carotane, high gammacerane content, and low diasterane content are detected in the analyzed samples, reflecting the saline-reducing paleoenvironment for the organic matter. Nine types of heteroatom compounds are detected: N1, N1O1, N1S1, O1, O1S1, O2, O2S1, S1, and S2. The main compounds are S1 and N1 compounds, followed by O1S1 compounds. The double-bond equivalent (DBE) value of S1 compounds is mainly distributed between 3 and 12, and the carbon number is mainly distributed between 18 and 35. The DBE value of N1 compounds is mainly distributed between 4 and 14, and the carbon number is mainly distributed in the range 15–35. Among the S1 compounds, DBE3 compounds (thiophenes) have relatively more sulfur-containing carotenoids (C40). The abundance of C40 S1 and the ratio of pyridine and its homologue DBE4–8/DBE9–12 N1 compounds show a good contrast with the paleoenvironment indicators of gammacerane/C30 hopane and diasterane/regular sterane. They can be used as a reference for the paleoenvironment index. Maturity is another factor affecting the distribution of NSO heteroatoms in the oil sands. NSO compounds are enriched in the DBE area with higher condensation, and the main peak carbon shifts forward. As the maturity increases, the relative abundance of N1 compounds increases, the aromatization intensifies, and carbon is broken into short chains. The research results shed light on the potential application of NSO compounds in petroleum exploration based on FT-ICR MS.

Tandem Mass-Remainder Analysis of Industrially Important Polyether Polyols.

The characteristics of the polyalkylene oxide polyether polyols highly influence the properties of final polyurethane products. As a novel approach, in order to gain structural information, the recently invented data mining procedures, namely the Mass-remainder analysis (MARA) and the Multistep Mass-remainder analysis (M-MARA) are successfully applied for the processing of tandem mass spectrometry (MS/MS) data of various industrially important polyether polyols. M-MARA yields an ultra-simplified graphical representation of the MS/MS spectra and sorts the product ions based on their double bond equivalent (DBE) values. The maximum DBE values unambiguously differentiate among the various polyether polyols. Accordingly, the characteristic DBE values were 0, 1 for the linear diol polyethers, 0, 1, 2 for the three-arm, and 0, 1 2, 3, 4 for the six-arm polyether polyols. In addition, it was also found that the characteristic collision energy necessary for the optimum fragmentation yield depended linearly on the molecular weight of the polyols. This relationship offers an easy way for instrument tuning to gain structural information.

Distribution of nitrogen and oxygen compounds in shale oil distillates and their catalytic cracking performance

The positive- and negative-ion electrospray ionization (ESI) coupled with Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) was employed to identify the chemical composition of heteroatomic compounds in four distillates of Fushun shale oil, and their catalytic cracking performance was investigated. There are nine classes of basic nitrogen compounds (BNCs) and eleven classes of non-basic heteroatomic compounds (NBHCs) in the different distillates. The dominant BNCs are mainly basic N1 class species. The dominant NBHCs are mainly acidic O2 and O1 class species in the 300–350 °C, 350–400 °C, and 400–450 °C distillates, while the neutral N1, N1O1 and N2 compounds become relatively abundant in the > 450 °C fraction. The basic N1 compounds and acidic O1 and O2 compounds are separated into different distillates by the degree of alkylation (different carbon number) but not by aromaticity (different double-bond equivalent values). The basic N1O1 and N2 class species and neutral N1 and N2 class species are separated into different distillates by the degrees of both alkylation and aromaticity. After the catalytic cracking of Fushun shale oil, the classes of BNCs in the liquid products remain unchanged, while the classes and relative abundances of NBHCs vary significantly.

Pyrolysis Temperature Effect on Compositions of Neutral Nitrogen and Acidic Species in Shale Oil Using Negative-Ion ESI FT-ICR MS.

Negative-ion electrospray ionization (ESI) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to study the effect of the pyrolysis temperature (400, 430, 460, 490, and 520 °C) on acidic and neutral nitrogen species in Huadian shale oil. To more accurately analyze the influence, shale oils produced during the heat-up stage were abandoned. The results show that because of the influence of polymerization and cracking reactions, the increase in temperature increases the content of pyrrole, thiophene, furan, phenol, and aromatic ring cores and decreases the content of carboxylic acid, respectively. Among all the heteroatom compounds identified from negative-ion ESI FT-ICR MS, the relative abundance of N1O1, N1O2, N1O3, N2, N2O1, O1, O3, O1S1, and N1S1 species increases, whereas that of O2 and O4 species decreases as the pyrolysis temperature increases. The decrease in the O2 species can be attributed to carboxylic acid with a double-bond equivalence (DBE) value of 1, whereas the increase in the O2 species with DBE values of 7 and 9 can be attributed to the formation of furan, phenol, and aromatic ring by the polymerization reaction at higher pyrolysis temperatures. Although the effect of the reaction temperature on the molecular composition of acidic and neutral nitrogen species is complex, still characteristic rules are found in this study.

Insights into the structural characteristics of four thermal dissolution extracts of a subbituminous coal by using higher-energy collisional dissociation

In coal chemistry, thermal dissolution (TD) is an effective processing technique to obtain soluble components from coal by using organic solvents under a certain pressure and temperature. Exploring molecular structures of the TD extracts of low-rank coal is of great importance for eco-friendly and value-added utilization in chemical industry. To well elucidate the structural information of components in coal, higher-energy collisional dissociation (HCD) specific to Orbitrap mass spectrometry was applied to analyze four TD extracts of a subbituminous coal. Alkyl chains of aromatic compounds can be removed from aromatic cores during a HCD process, allowing determination of the distribution of heteroatoms in either aromatic cores or alkyl chains. Both double bond equivalent value and carbon number of precursor ions (whole molecules) and the corresponding fragment ions (aromatic cores) obtained via a HCD process were used to evaluate the relationship between aromatic cores and alkyl chains for compounds in coal. With the increase of molecular weight, compounds in coal exhibited different distributions for aromatic cores and alkyl chains. From 200 Da to 300 Da, the increase of carbon number mainly contributed to the formation of condensed aromatic cores. However, from 300 Da to 400 Da, it was attributed to the formation of both aromatic cores and alkyl chains. In addition, heteroatom distribution index indicated that a higher TD yield of heteroatom-containing compounds would be obtained via solvents with a smaller molecular size and nitrogen-containing aromatics would be enriched by using TD solvents containing aromatic ring.

Estimating the intermediate precision in petroleum analysis by (±)electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) is an important analytical technique used for the elucidation of crude oil polar compounds at the molecular level, providing thousands of heteroatom compounds in a single analysis. Due to the high resolution, the complexity of data produced, and steps involved in spectra acquisition and processing, it is necessary to estimate its intermediate precision. Intermediate precision was estimated for positive- and negative-ion ionization modes (ESI(±)) using Composer® software for two Brazilian crude oil samples. The analytical parameters evaluated were the class distribution histogram, the double bond equivalent (DBE) distribution, and the DBE versus carbon number. The statistical parameters used to study the intermediate precision were calculated from the average, standard deviation, confidence interval (significance level at 5%), coefficient of variation (CV), intermediate precision limit (ISO 5725), and principal component analysis (PCA). Two crude oil samples (A and B) were analyzed, in triplicate, for seven consecutive days by ESI(±) FT-ICR MS. The assigned class limit by ESI(+) for crude oil A was 0.42% (O2 S[H] class) and for crude oil B was 0.04% (N2 O2 S[H] class). The assigned DBE intensity limits for the two crude oils were 0.04% for ESI(+) and 0.013% for ESI(-). The PCA for ESI(-) and ESI(+) modes presented better precision for crude oils B and A, respectively. The most abundant classes and DBE of the majority class (i.e., with the highest intensity) are the parameters produced from the Composer® software that had the highest precision and can be used to estimate crude oil properties. The DBE values presented lower intermediate precision limit values (0.04%) than the assigned class values (0.4%). According to CV and PCA, ESI(+) was more precise for crude oil A (83% precision) and ESI(-) for crude oil B (84% precision).

Occurrence forms and molecular structural characteristics of the organic nitrogen in lignite

The occurrence forms of organic nitrogen in Xianfeng lignite (XL), Xiaolongtan lignite (XLT) and Shengli lignite (SL) as well as their extraction residues were characterized by X-ray photoelectron spectroscopy (XPS). The results show that the content distributions of organic nitrogen in the three extraction residues are different, but all are mainly dominated by pyrrolic nitrogen. The NaOH-catalyzed supercritical methanolysis of lignite extraction residues at 300°C was then investigated, which indicates that the yields of petroleum ether soluble portions from supercritical methanolysis of extraction residues derived from XL, XLT and SL are 46.0%, 43.8%, and 47.6%, respectively. The characterization of nitrogen-containing compounds (NCCs) in petroleum ether soluble portions by Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS) indicates that NCCs are mainly composed of N1, N1O1-N1O5, N2, N2O1-N2O4, N3O2 and N5O2-N5O4 class species. The molecular structural characteristics of NCCs were speculated according to the distributions of double bond equivalent values and carbon numbers, which shows that most of NCCs contain oxygen-functional groups like hydroxyl and carboxyl groups, and the nitrogen atoms are mainly present in aromatic structures (mainly 1–3 aromatic rings) in the forms of pyrrolic, pyridinic and amino groups. The cleavage of C-O bridged bonds in lignite is an important pathway for producing NCCs.

The acid and neutral nitrogen compounds characterized by negative ESI Orbitrap MS in a heavy oil before and after oxidation

One heavy crude oil from Liaohe Basin, NE China and its oxidized counterparts at 200 and 400 °C have been characterized geochemically by negative-ion electrospray ionization Orbitrap mass spectrometry to investigate the variation of acid and neutral nitrogen compounds during in-situ combustion. The heteroatom compounds of acid and neutral nitrogen detected in the samples are mainly N1, N1O1, N1O2, O1, O2, O3 and O4 classes, dominated by N1, O1 and O2. The N1 class predominated by carbazole and benzocarbazole with double bond equivalents (DBE) 9 and 12, is relatively stable and resistant to oxidation, while the N1O1 and N1O2 classes vary without a clear trend during oxidation. The O1 class is generally low in raw sample and the 200 °C oxidized oil but increases sharply in the 400 °C oxidized oil. The O2 class is peaked in the 200 °C oxidized oil but its relative concentration declines drastically in the 400 °C oxidized oil. The O1 and O2 class compounds show a similar DBE and carbon number (CN) distribution trend with increasing temperatures. Lower DBE and CN compounds are enriched in the 400 °C oxidized oil after alkyl side chain cleavage, where small proportion of high DBE compounds derived from aromatization and condensation has also been observed. The relative abundance of O1 and O2 species with specific DBE values and carbon number ranges are sensitive to in-situ thermal upgrading and ratios of DBE1/DBE4-O1 and DBE1/DBE3-O2 endure the potential as geochemical proxies to monitor the degree of oil upgrading.

Insight into structural features of soluble portions from cellulose, cellobiose and monosaccharide methanolysis by GC/MS and ESI FTICRMS

Methanolysis of biomass has attracted increasing attention due to it has some advantages, such as low critical points and strong hydrogen donation ability. In this paper, methanolysis of cellulose, cellobiose (sucrose), and monosaccharide (glucose) were performed to obtain methanol-soluble portions (MSPs). The relatively volatile or less polar species in the MSPs were analyzed with a gas chromatograph/mass spectrometer (GC/MS), and the polar species were identified with a negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (FTICRMS). According to analysis with GC/MS, the MSPs include ethers, esters, ketones, acids, sugars, phenols, and furans. The analysis with FTICRMS shows that the polar compounds in the MSPs are O1–O15 class species with 1–14 double bond equivalent (DBE) and 5–35 carbon atom number (CAN). The most abundant class species in MSPs from cellulose, sucrose, and glucose methanolysis are O5, O7, and O7, respectively. The species in MSPs from sucrose and glucose methanolysis center at higher DBE value and more CAN than those in MSP from cellulose methanolysis. Meanwhile, the oxygen atom number of O4–O10 class species in the MSPs were negatively correlated with the average DBE value. The results indicate that condensation intensively proceeded with the specific regularity during sucrose and glucose methanolysis.

Molecular level determination of water accommodated fraction with embryonic developmental toxicity generated by photooxidation of spilled oil

In this study, developmental toxicity was increased as the oil was further degraded under natural sunlight. Detailed chemical composition of the degraded oils was examined by use of gas chromatography (GC) and (−) electrospray ionization ultrahigh resolution mass spectrometry (UHR-MS). Baseline toxicities were estimated based on chemical activities of polycyclic aromatic hydrocarbons, and it was obvious that the predicted chemical activities can not explain increased toxicity alone. However, the ultrahigh resolution mass spectral abundance of polar compounds including O3 and O4 class compounds was significantly increased as the photodegradation proceeded. Further examination of double bond equivalence values of the compounds showed that polar compounds with both non-aromatic and aromatic polar structures were increased. Statistical analysis indicates that the increased toxicity can be well explained by the increased polar compounds. Therefore, the oxygenated compounds identified in this study can play an important role in toxicity of degraded oils.

Characterization of nitrogen-containing aromatics in Baiyinhua lignite and its soluble portions from thermal dissolution

Abstract Soluble portions (SPs) 1–4 (SP1–SP4) were afforded from sequentially dissolution and alkanolyses of Baiyinhua lignite (BL) in cyclohexane, CH3OH, CH3CH2OH, and (CH3)2CHOH at 300 °C. They were analyzed with a gas chromatograph/mass spectrometer and quadrupole exactive orbitrap mass spectrometer (QEOTMS) with an atmosphere pressure chemical ionization source in positive-ion mode, while BL was characterized with an X-ray photoelectron spectrometer (XRPES). The results show that the yields of SP2 and SP3 are much higher than those of SP1 and SP4, and the total SP yield is ca. 39.0%. According to the analysis with XRPES, pyrrolic nitrogen atoms are the most abundant nitrogen existing forms in BL. Thousands of nitrogen-containing aromatics (NCAs) were resolved with QEOTMS and their molecular masses are mainly in the range of 200–450 u. The main NCAs are N1O1 and N1O2 class species with double bond equivalent values of 4–18 and carbon numbers of 7–30. The nitrogen atoms appear in pyridines, quinolines, benzoquinolines or acridine, and dibenzoquinolines or naphthoquinolines, while the oxygen atoms exist in methoxy and furan rings.