Electrospray Fourier Transform Ion Cyclotron Research Articles

Low-temperature oxidation characteristics and reaction pathways of crude oil within tight shale during air injection

The investigation of low-temperature oxidation (LTO) of crude oil within tight shale holds significant importance due to its implications for subsequent oxidation reactions and enhanced oil recovery in the process of air injection. In this study, the tight shale sample underwent oxidation at various LTO temperatures, followed by an analysis of the resulting gas composition. Furthermore, the oxidized oil was separated from the tight shale and subjected to characterization using electron paramagnetic resonance, nuclear magnetic resonance, and negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry techniques. The primary focus was on examining the distinct LTO reaction pathways observable across different temperature ranges. The findings demonstrated a correlation between LTO temperature and the concentration of free radicals, which predominantly resided on aromatic hydrocarbons, alkanes, and oxygen atoms. Additionally, the proton count of polycyclic aromatic hydrocarbons exhibited a continuous increase from 83 to 350 °C, suggesting intensified aromatization and condensation reactions involving aliphatic and aromatic compounds. With rising LTO temperature, the molecular structure of O2 compounds underwent significant transformations, characterized by increased condensation degree and a decrease in low carbon number molecular structures, while higher equivalent double bonds and carbon number molecular structures became more prevalent. The influence of cycle path 1 diminished at temperatures ranging from 83 to 150 °C and 250 to 350 °C, whereas the significance of cycle paths 2 and 3 increased, resulting in an overall escalation of the oxidation rate with temperature elevation. It was observed that the shale oil LTO process exhibited a negative temperature coefficient within the temperature range of 150-250 °C, emphasizing the criticality of overcoming the energy barrier in this region to achieve stable combustion. This comprehensive investigation provides valuable insights into the mechanisms underlying LTO in crude oil confined within tight shale.

Direct Infusion Metabolomics of the Photosystem and Chlorophyll Related Metabolites within a Drought Tolerant Plant Introduction of Glycine max.

Drought is the most prolific form of abiotic stress that legumes and cereal plants alike can endure, and the planting of an improper cultivar at the beginning of a season can cause unexpected losses up to fifty percent under water deficient conditions. Herein, a plant introduction (PI) of an exotic cultivar of soybean (Glycine max), PI 567731, which demonstrates a slow wilting (SW) canopy phenotype in maturity group III, was profiled under drought conditions in field trials in Missouri against a drought susceptible check cultivar, Pana. Metabolomic profiling was carried out on samples of leaves from each of these cultivars at V5 and R2 growth stages both while irrigated and while under drought stress for three weeks. PI 567731 was observed to have differential phytochemical content, and enhanced levels of chlorophyll (Chl) a/b and pheophytin (Pheo) were profiled by direct infusion electrospray Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Indicating drought induced changes of the photosystem and photosynthetic capabilities alongside water preservation strategies are important within the SW phenotype drought response. Subsequent multivariate analysis was able to form predictive models, encompassing the variance of growth and drought stress of the cultivar. Moreover, the existence of unique Chl-related metabolites (CRM) (m/z > 900) were confirmed through tandem mass spectrometry. The resultant coordination of fatty acids to the core of the porphyrin ring was observed and played an unknown role in the proliferation of the photosynthesis. However, the relative ratio of the most abundant CRM is undisturbed by drought stress in PI 567731, in contrast to the drought susceptible cultivar. These results provide key insights into drought related metabolic mechanisms.

Low-temperature oxidation of heavy crude oil characterized by TG, DSC, GC-MS, and negative ion ESI FT-ICR MS

Low-temperature oxidation (LTO) is of great significance for the subsequent oxidation reactions and oil recovery during in-situ combustion. The paper brings an in-depth analysis of crude oil LTO that is still not well understood. Firstly, one Xinjiang heavy oil was subjected to LTO reactions under different temperatures conducted in an oxidation reactor. The combustion behaviors of the oxidized oils were then investigated by thermogravimetry and differential scanning calorimetry. The Friedman and Ozawa-Flynn-Wall methods were adopted to perform combustion kinetic analysis of the oxidized oils. Subsequently, both gas chromatograph-mass spectroscopy and negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry were introduced as a new route to investigate the compositional changes of crude oil caused by LTO. The condensation of aromatics as well as aromatization and condensation of other compounds was intensified from 40 to 200 °C. Chain saturated aliphatic, monocyclic, bicyclic, and tricyclic naphthenic acids were the main acidic components in the oxidized oils. The relative abundance of chain saturated aliphatic acids and O1 species was decreased from 40 to 200 °C, whereas that of tricyclic naphthenic acids and O3 species was increased. Finally, we summarized LTO reaction pathways of crude oil, which helped to understand LTO mechanisms.

Phenolic and glycidic profiling of bananas Musa sp associated with maturation stage and cancer chemoprevention activities

Banana, Musa sp, is widely consumed all over the world, being popularly known as a natural antioxidant. The glycidic profile obtained by negative-ion mode electrospray Fourier transform ion cyclotron resonance mass spectrometry of the Pacovan, Ambrosia, Japira, Prata Comum, Vitória and Tropical cultivars, in four stages of maturation, showed that the Prata-type cultivar presented higher monosaccharide content than the disaccharides. On the other hand, Gros Michel-type (Ambrosia) and Maça-type (Tropical) cultivars presented the opposite behavior. The phenolic profile showed that, in all cultivars, the most abundant phytochemical class was flavonoids, such as myricetindeoxyhexose-hexoside, followed by cinnamic acids, such as caffeic acid. All samples evaluated showed high inhibition of the nitric oxide production. Furthermore, the Pacovan-type cultivar, at maturity stage 2, showed high inhibition of NF-κB; and extracts of cultivar Japira-type, maturity stages 2, 4 and 7, and Ambrosia, stage 4, showed greater aromatase inhibition, i.e., higher than 50%.

Characterization of organosulfur compounds in asphalt cement samples by ESI(+)FT-ICR MS and 13C NMR spectroscopy

Herein, it is presented a methodology for the characterization of organosulfur compounds in asphalt cement (AC) samples employing solid-phase extraction (SPE) associated with methylation reactions and positive-ion mode electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI(+)FT-ICR MS) and carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy. Three AC samples were submitted to an SPE separation, and the fractions obtained the original AC samples, and their maltenes were methylated and analyzed using the ESI(+)FT-ICR MS. The ESI(+)FT-ICR MS ionized the sulfur fractions much better than the original samples, detecting organosulfur compounds with a broader average molecular mass distribution (Mw). Several types of sulfur compounds were detected, such as sulfides, disulfides, thiophenes, and dibenzothiophenes. Besides, the ESI(+)FT-ICR data were compared with the 13C NMR (from model molecules analyses) and ESI(+)-Orbitrap MS. The organosulfur chemical profile was correlated to the physical properties of AC samples. It was verified that the samples with higher aromatic-character were less susceptible to aging test, while the one with more saturated-character presented more significant variation in their physical properties after the aging test.

Isolation and characterization of hydrophilic dissolved organic matter in waters by ion exchange solid phase extraction followed by high resolution mass spectrometry

Dissolved organic matter (DOM) is a complex substance occurring in marine and freshwater environments. DOM has many functions that modify physical, chemical and biological processes in ecological systems. Solid-phase extraction (SPE) is widely used for the separation of DOM. However, a part of strongly hydrophilic compounds are lost using classical SPE separation. In this article, the strong hydrophilic components, which cannot be extracted by the hydrophobic reverse phase SPE, were further extracted in a natural organic matter sample by ion exchange SPE cartridges to obtain hydrophilic acid (HIA), hydrophilic neutral (HIN), and hydrophilic base (HIB) fractions. The extracts were characterized by three-dimensional excitation–emission matrix fluorescence spectroscopy and negative-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The results revealed that the hydrophilic components were significantly different from the hydrophobic components in molecular composition. Hydrophilic components were identified as tryptophan-like and tyrosine-like compounds by three-dimensional fluorescence spectra. The HIA fraction contains mainly tannic acid-like compounds with high O/C ratio; the HIB fraction contains mainly amide-like compounds; and the HIN fraction contains mainly lignin and lipids.

Geochemical characterization of lacustrine and marine oils from off-shore Brazilian sedimentary basins using negative-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR-MS)

Lacustrine and marine crude oils from different off-shore Brazilian basins were analyzed using a 7.2 Tesla LTQ FTICR-MS instrument. The samples were analyzed via electrospray ionization in the negative ion mode focusing on the polar compounds, i.e., nitrogen-, sulfur-, and oxygen-containing (NSO) compounds. We also employed a combination of other geochemical methods, such as GC-FID and GC-MS analyses, to characterize and assess the depositional environments of the different oil families. The results indicate that lacustrine oils tend to be enriched in Nx compounds, while marine oils show preference for Ox compounds. The dominant heteroatomic classes in crude oils are N1, followed by O1, O2, and N1O1 with remarkable differences in their distributions between marine and lacustrine, strongly suggesting the control by the kerogen type of the heteroatomic compounds found in these crude oils. Considerable differences in the DBE distribution of the main classes analyzed between the crude oils allowed an efficient geochemical characterization regarding their origin. The use of negative ESI FTICR-MS as a geochemistry tool can provide additional information beyond that obtained with currently employed geochemical methods, resulting in the full comprehension of crude oil composition.

Negative electrospray Fourier transform ion cyclotron resonance mass spectrometry determination of the effects on the distribution of acids and nitrogen-containing compounds in the simulated thermal evolution of a Type-I source rock

The thermal maturity level impact on polar compounds was analyzed for a suite of hydrous pyrolysis (HP) products using a 7.2 Tesla LTQ FTICR-MS instrument. The sample suite was analyzed via electrospray ionization in the negative ion mode focusing on the polar compounds, i.e., nitrogen-, sulfur-, and oxygen-containing (NSO) compounds. The HP experiments were performed under isothermal conditions for 2 h at eleven different temperatures (300, 310, 320, 325, 330, 340, 345, 350, 355, 360 and 365 °C) to simulate the full range of thermal levels starting at early bitumen generation to maximum oil generation. The maturity suite samples consist of one immature bitumen (original sample), eleven expelled oil samples and eight residual bitumen samples. In general, Ox compounds are destroyed by decarboxylation and dehydration with increasing maturity; sulfur compounds decrease; the aromaticity and degree of condensation increase; and steranoic and hopanoic acids decrease. Additionally, we investigated fluid retention properties comparing the carbon number distribution between the expelled oil and residual bitumen samples from each experiment. The maturity related changes of the acidic O2 compounds in the expelled oil samples led us to create several regressions that we propose as new maturity parameters covering the full range of oil generation.

Fractionation of asphaltenes in n-hexane and on adsorption onto CaCO3 and characterization by ESI(+)FT-ICR MS: Part I

Two methods of asphaltenes fractionation have been employed to facilitate the characterization of their respective subfractions. The methods are based on step-wise precipitation with different n-hexane/crude oil ratios, and on adsorption onto CaCO3. Three subfractions were produced for each method, being named of 3.5V, 3.5–6V, and 6–40V (for the first method); and non-adsorbed (bulk), adsorbed, and irreversibly adsorbed (for the second method). The fractions were characterized by elementary analysis, nuclear magnetic resonance of proton (1H NMR) and by positive ion-mode electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI(+)FT-ICR MS). The elemental analysis, described in previous work, revealed that the C/H ratio for whole asphaltene and its sub-fractions varied between a narrow range (0.83–0.88) which means they present similar aromaticity or unsaturation. Furthermore, the elemental analysis corroborates with the 1H NMR analysis suggesting that subfraction 6–40V presented a more aromatic profile than of remaining subfractions, while for the fractionation using CaCO3, this behavior was observed for the adsorbed subfraction. However, a more detailed molecular information was obtained from ESI(+)-FT-ICR MS data, showing that polar compounds species with lower carbon numbers were mainly found for the irreversibly adsorbed subfraction. Besides, the double bond equivalent (DBE) distribution is an important tool to associate the chemical information with solubility parameters, in which, a narrower DBE distribution was observed for irreversibly adsorbed (for fractionation onto CaCO3) and subfraction 3.5V (fractionation in n-hexane) samples, indicating that they are less soluble in hydrocarbons. Also, solubility parameters (δ) were calculated from ESI(+)FT-ICR MS data, where the results indicate that subfractions produced in n-hexane have a lower tendency to precipitate in hydrocarbons in relation to subfractions produced onto CaCO3.

Characteristics and geochemical significance of heteroatom compounds in terrestrial oils by negative-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry

Terrestrial oils and rock extracts from the Nanpu Sag (Huanghua Depression, Bohai Bay Basin, China) were characterized by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography mass spectrometry (GC-MS). Molecular composition of neutral nitrogen and acidic oxygen compounds, mainly by N1, O1, and O2 species were investigated in the samples. Increases in relative abundance and molecular condensation degree of oxygen-containing compounds and a decrease in the carbon number range of N1 species were observed with the changes of kerogen from Type I to III for both the source rock extracts and the relevant oils, which indicates the influence of source input and discrimination potential. We also observed an apparent increase in the condensation degree and a decrease in the carbon number of the N1, O1 and N1O1 species with increasing maturity. The carbon numbers and double bond equivalent (DBE) values of the N1 and N1O1 species in the extracts showed a positive relationship (an approximately linear distribution) during thermal evolution. These results indicate that thermal maturity has a crucial influence on the composition. The relative abundance ratios of N1 and O1 species with specific DBE values and carbon number ranges, C16–20/C21–50-DBE12-N1, C20–24/C25–50-DBE15-N1, C11–15/C16–27-DBE4-O1, DBE12/DBE9-N1, and DBE8–9/DBE4-O1 are proposed as thermal maturity indicators for the evaluation of mature and post-mature source materials. A strong primary migration fractionation effect on the heteroatom compounds was also observed, implying that these compounds can be used as migration auxiliary proxies.

Waxy Crude Oil Emulsion Gel: Chemical Characterization of Emulsified Phase Extract Components

Emulsions of several waxy crude oils exhibiting similar properties were prepared and characterized to better understand the nature of their polar components. Both crude oils and their corresponding emulsions were analyzed by negative-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry [ESI (−) FT-ICR MS]. The most abundant classes found in these crude oils were neutral N, acidic O, and O2 heteroatomic compounds. The N class was present in higher relative abundance in all samples, followed by the O class (phenolic-like compounds). The O2 class was minor in all crude oils, corroborating their low total acid number (TAN) values. The O/O2 class ratios were directly correlated with their rheological properties. Higher O/O2 class ratios were associated with crude oils that formed gel emulsions, indicating that O class compounds play an important role in gel emulsion stabilization. The identified phenolic compounds possess a structure that allows for (i) intermolecular hydrogen-bonding i...

Effect of secondary oil migration distance on composition of acidic NSO compounds in crude oils determined by negative-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry

The acidic and neutral NSO compounds in a series of Duvernay-sourced oils in Canada, which are believed to have migrated extensively over relatively long distances such as along the Rimbey-Meadowbrook reef trends, were characterized by negative-ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Heteroatomic compounds were characterized according to their class (number of nitrogen, oxygen and sulfur heteroatoms), degree of aromaticity [rings plus double bonds (DBE)] and carbon number distribution. The N1, N1O1, N1O2, N1S1, O1 and O2 classes were identified in Duvernay-sourced oils. With increasing migration distance, the relative abundance of O2, N1O1 and N1O2 showed a significant decrease, while the O1 class increased from <10% to nearly 30% of the total. With increasing migration along the Rimbey-Meadowbrook reef trend, pyrrolic nitrogen compounds (N1 class) shows an enrichment of alkylcarbazoles (DBE=9) relative to alkylbenzocarbazoles (DBE=12), and of higher homologous relative to the lower homologous. O1 compounds show a relative enrichment of those with low DBE values. Additionally, the N1O1 and N1S1 compounds show a relative enrichment of those with high DBE values, and of higher homologues compared to the lower homologues, indicating great potential for developing new migration indices.

Mechanisms involved in the gastroprotective activity of Celtis iguanaea (Jacq.) Sargent on gastric lesions in mice

Ethnopharmacological relevanceCeltis iguanaea (Canabaceae) is popularly known as esporão-de-galo, stands out among the medicinal plants used for treatment of gastric ulcers. In Brazil, the leaves they are used traditionally in infusion forms as an analgesic, antiasthmatic, digestive and diuretic. Aim of the studyThe present study was aimed to investigate the antiulcer mechanisms of hexane extract Celtis iguanaea leaves (HE) in several induced-gastric ulcer and characterize its chemical composition. Materials and methodsThe HE was obtained by exhaustive extraction in Soxhlet apparatus. The chemical characterization of HE was performed by Electrospray Fourier transform ion cyclotron mass spectrometry (ESI FT-ICR MS) analysis. Mice were used for the evaluation of the gastroprotective activity. HE was analyzed in the HCl/ethanol, hypothermic restraint stress ulcer and acetic acid. In the investigation of the gastroprotective mechanisms of HE, were performed the amount of adhered gastric mucus, participation of the α2-adrenoceptor, nitric oxide (NO) and prostaglandins (PGs) using the HCl/ethanol-induced gastric mucosa lesion model. ResultsESI FT-ICR MS analysis of HE suggest the presence of compounds as lipids, sterol lipids, steroids glycosides and polyphenol glycosides. The oral administration of HE at doses of 100mg/kg or 200mg/kg was able to protect the gastric mucosa against HCl/ethanol (10mL/kg p.o.), and HE at dose of 100mg/kg protected against hypothermic-restraint stress and acetic -induced gastric lesions. The pretreatment with Yoimbine (2mg/kg, s.c.), an antagonist α2-adrenergic, L-NAME (20mg/kg, s.c.), an inhibitor of nitric oxide synthesis or indomethacin (10mg/kg, s.c.), an inhibitor of prostaglandin production, reversed the gastroprotective activity of HE (100mg/kg, p.o.). ConclusionsOur results suggest that the Celtis iguanaea HE exhibits gastroprotective activity in different gastric ulcer models. The mechanism of gastroprotective effect of Celtis iguanaea HE suggests the participation of mucus as well as the involvement of α2-adrenergic receptors, NO and prostaglandins. The hydroxyl-linolenic acid, linoleic acids and conjugated oxo-linoleic acids are among the phytoconstituents that were identified in the Celtis iguanaea HE.

Thermochemical Sulfate Reduction Simulation Experiments on the Formation and Distribution of Organic Sulfur Compounds in the Tuha Crude Oil

Thermochemical sulfate reduction (TSR) was conducted in autoclave on the system of crude oil and MgSO4 at different temperatures. Gas chromatography pulsed flame photometric detector (GC-PFPD) was used to detected the composition of organic sulfur compounds in oil phase products. The results of the analysis indicate that with increased temperature, the contents of organic sulfur compounds with high molecular weight and thermal stability, such as benzothiophenes and dibenzothiophenes, gradually became dominated. In order to gain greater insight into the formation and distribution of organic sulphur compounds from TSR, positive ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used in detecting the detailed elemental composition and distribution of them. The mass spectra showed that the mass range of sulfur compounds was 200-550 Da. Four sulfur class species, S1, N1S1, O1S1 and O2S1, were assigned in the positive-ion spectrum. Among the identified sulfur compounds, the S1 class species was dominant. The most abundant S1 class species increase associated with the DBE value and carbon number increasing which also indicates the evolution of organic sulfur compounds in TSR is from the labile series to the stable one. In pure blank pyrolysis experiments with crude oil cracking without TSR, different composition and distribution of organic sulfur compounds in oil phase products were seen from mass spectra in order to evaluate their pyrolysis behaviors without MgSO4. FT-IR and XRD were used in analyzing the products of solid phases. Two distinct crystallographic phases MgO and MgSO4 are found to coexist in the products which demonstrated the transformation of inorganic sulfur compounds into organosulfur compounds exist in TSR.

Binding of α,ω-alkyldiammonium ions by cucurbit[n]urils in the gas phase

We investigated gas-phase complexes of α,ω-n-alkyldiammonium ions with cucurbit[5]uril (CB[5]), decamethylcucurbit[5]uril (mc5), penta(cyclohexyl)cucurbit[5]uril (CB*[5]), hexa(cyclohexyl)cucurbit[6]uril (CB*[6]), cucurbit[7]uril (CB[7]) and cucurbit[8]uril (CB[8]) using electrospray Fourier transform ion cyclotron resonance mass spectrometry and collision-induced dissociation techniques. The five-membered cucurbit[n]urils (CB[n]s) form singly charged 1:1 and doubly charged 2:1 diamine:CB[n] complexes. All dissociate via loss of neutral α,ω-n-alkyldiamine with only weak dependence of dissociation thresholds on chain length. For a given diamine, threshold energies are in the order CB[5] < mc5 < CB*[5]. This is consistent with guest hydrogen bonding on the portals of the CB[5]s with no threading into the host's interior. The n ≥ 6 CB[n]s form 1:1 complexes with doubly protonated α,ω-n-alkyldiamines. These collisionally dissociate via four channels: loss of singly protonated α,ω-n-alkyldiammonium; fragmentation of the CB[n] cage; loss of neutral α,ω-n-alkyldiamine and fragmentation of the α,ω-n-alkyldiamine. The dissociation threshold energies and branching ratios exhibit strong dependence on the length of the α,ω-n-alkyldiamine and the size of the CB[n]. The data suggest that the optimum α,ω-n-alkyldiamine length for binding CB*[6] is three to four methylene groups; for CB[7], four to five methylene groups and for CB[8], five to six methylene groups, indicating an increasing tendency for the guest to span the host cavity diagonally as the size of the CB[n] increases.

Assessing Biodegradation in the Llanos Orientales Crude Oils by Electrospray Ionization Ultrahigh Resolution and Accuracy Fourier Transform Mass Spectrometry and Chemometric Analysis

Focusing on the O2 class, a set of crude oils from Llanos Orientales Basin, Colombia, were classified in terms of biodegradation levels using negative ion mode electrospray Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and chemometric analysis. The O2 class, which is mainly composed of naphthenic carboxylic acids, was monitored because these polar crude oil constituents are known to be substantially affected by microbial activity. Principal component analysis (PCA) applied on the O2 profile was able to classify the crude oils into three groups: biodegraded, mixture, and non-biodegraded. From the relative abundances of the O2 class, a clear trend on acid distribution could be directly correlated with biodegradation: a rising in abundance of saturated acids with low double-bond equivalent (DBE) values (despite the lowering observed for fatty acids with DBE = 1), expressed by the A/C index. The combined use of two indexes, the A/C index and a new index also based on saturated acid a...

Distribution of acids and nitrogen-containing compounds in biodegraded oils of the Liaohe Basin by negative ion ESI FT-ICR MS

Seven reservoir core (tar sand) bitumens of identical source and similar maturity from the Liaohe Basin of northeast China possess a natural sequence of increasing severity of biodegradation. This set of samples provides us an opportunity to study the change in oil composition or compound class distributions with biodegradation severity by negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry (FT ICR-MS). The bitumen extracts from two columns (Es3 and Es1) were separated into maltene and asphaltene fractions for analysis of heteroatomic species by ESI FT-ICR MS. The maltene fractions were found to mainly contain N1, N1O1, N1O2, N1O3, O1, O2, O3 and O4 classes, while the asphaltene fractions mainly contain N1, N2O1, N1O1, N1O2, N1O3, N1O4, O2, O3, O4 and O5 classes. These species identified by FT-ICR MS in asphaltene fractions are likely to be chemisorbed/coprecipitated compounds, or the species precipitated due to high polarity during deasphaltene process. The susceptibility of compound classes and homologous series to biodegradation was studied based on the relative abundances. The results indicate that microorganisms alter the distribution of acids and nitrogen-containing compounds by selective removal and preservation of certain classes of compounds according to their susceptibility to biodegradation. For example, O2 and N1O2 classes increase significantly while N1 and N1O1 classes decrease with biodegradation. The differences in the susceptibility to microbial alteration within acyclic acids, 4–5 ring acids and 1–2 ring acids are discussed and the differences in the susceptibility of homologous series of heteroatom-containing polycyclic aromatic hydrocarbons are also discussed in this work.

Analysis of Saturated Hydrocarbons by Redox Reaction with Negative-Ion Electrospray Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

A novel technique was developed for characterization of saturated hydrocarbons. Linear alkanes were selectively oxidized to ketones by ruthenium ion catalyzed oxidation (RICO). Branched and cyclic alkanes were oxidized to alcohols and ketones. The ketones were then reduced to alcohols by lithium aluminum hydride (LiAlH(4)). The monohydric alcohols (O(1)) in the products obtained from the RICO and RICO-LiAlH(4) reduction reactions were characterized using negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for identification of iso-paraffins, acyclic paraffins and cyclic paraffins. Various model saturated compounds were used to determine the RICO reaction and ionization selectivity. The results from the FTICR MS analysis on the petroleum distillates derived saturated fraction were in agreement with those from field ionization gas chromatography time-of-flight mass spectrometry (FI GC-TOF MS) analysis. The technique was also used to characterize a petroleum vacuum residue (VR) derived saturates. The results showed that the saturated molecules in the VR contained up to 11 cyclic rings, and the maximum carbon number was up to 92.

A mini‐electrodialysis system for desalting small volume saline samples for Fourier transform ion cyclotron resonance mass spectrometry

An affordable, commercially available mini‐electrodialysis (mini‐ED) system has been evaluated for the efficient desalting of small volume samples of seawater before analysis by electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FT‐ICR MS). Mini‐ED FT‐ICR mass spectra were compared with spectra for samples that were treated by C18 solid phase extraction, a commonly used method for rapid sample preparation for this type of analysis. In this comparison, it is clear that mini‐ED provides more representative molecular information, compared with C18 isolation, and recovers the overwhelming majority of peaks from salt‐free samples, indicating that it adequately represents the DOM that can be ionized and analyzed by ESI FT‐ICR MS. The ED system produces a significant carbon blank. However, the substances contributing to this blank are not detectable by ESI FT‐ICR MS. Based on these findings mini‐ED is recommended as a promising method for the desalting of aqueous environmental samples before analysis by ESI FT‐ICR MS.

Distribution of Sulfides and Thiophenic Compounds in VGO Subfractions: Characterized by Positive-Ion Electrospray Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Detailed elemental composition and distribution of sulfides and thiophenic compounds in four subfractions of Kazakhstan vacuum gas oil (VGO) were determined by positive ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The sulfides in VGO subfractions were selectively oxidized into sulfoxides using tetrabutylammonium periodate (TBAPI). The sulfur compounds in the oxidized VGO subfractions were reacted by methylation to form methylsulfonium salts and were then characterized. Elemental composition and distribution of sulfides and thiophenic compounds in the VGO subfractions were characterized by their double bond equivalents (DBE) values and carbon numbers before and after the oxidation reactions. The results showed that the S1 class species with DBE values of 6 and greater are likely thiophenic compounds, while those with DBE values less than 6 are sulfides. As boiling point of VGO increased, the abundance of thiophenic compounds increased. DBE value and carbon number of the compounds also increased.