Number Of Double Bond Equivalents Research Articles

Treatment of naphthenic acids in oil sands process-affected waters with a surface flow treatment wetland: mass removal, half-life, and toxicity-reduction

This study is the first to investigate the removal of naphthenic acids in a full-scale constructed wetland within the Alberta Oil Sands region. The average mass-removal efficiency for all O2-naphthenic acids measured in three separate deployments in the wetland ranged from 7.5% to 68.9% and appeared sensitive to physicochemical properties of the naphthenic acids, environmental conditions, and water quality. Treatment efficiency of individual naphthenic acids was found to increase with increasing carbon number and decreasing number of double bond equivalents in the molecule. Treatment efficiency was also found to increase with both higher initial turbidity in OSPW entering the wetland, and warmer average OSPW temperatures during wetland operation. Half-life times of naphthenic acids in the treatment wetland ranged between 8.9 and 39 days and were substantially lower than those in tailings ponds (i.e., 12.9–13.6 years) and laboratory studies focussed on bench-scale aerobic microbial biodegradation (i.e., 44–315 days). Using published dose-response data, biomimetic extraction measurements using solid phase microextraction fibers indicate that 14 days of wetland treatment resulted in a reduction in (4 d) deformity of Danio rerio from 50 to 16%, while exhibiting less than 1% toxic response for less sensitive toxic endpoints. The study concludes that wetland treatment is a feasible and productive treatment method for naphthenic acids in oil sands process-affected water due to a combination of sorption and biodegradation.

Evaluation of the effects of the simulated thermal evolution of a Type-I source rock on the distribution of basic nitrogen-containing compounds

Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) allows the molecular-level characterization of ultracomplex mixtures such as crude oil samples. By combining FT-ICR MS with electrospray ionization, a myriad of polar compounds can routinely be identified and assigned with unmatched mass resolution and accuracy. The profile of polar compounds containing NSO atoms can be used to track and evaluate important parameters of crude oil. Recently, using ESI FT-ICR MS in the negative mode (https://doi.org/10.1016/j.orggeochem.2017.10.004), we investigated changes in the profile of polar compounds as a function of thermal maturity. Sulfur-containing compounds are completely destroyed during maturation, and the relatively high content of O-containing compounds decreases via decarboxylation and dehydration. The number of double bond equivalents (DBE) increased, indicating the occurrence of aromatization and condensation. However, the carbon number distribution shifted to lower values as a function of thermal maturity. Six regressions based on changes in the contents of O2 compounds were proposed as maturity parameters. Here, by focusing on tracking and evaluating the impact of thermal maturity on basic polar compounds, a set of hydrous pyrolysis (HP) products was analyzed using an ESI(+) 7.2 T LTQ FT-ICR MS system. The samples at various stages of maturity consist of one immature bitumen (original sample), eleven expelled oil samples and eight residual bitumen samples. Determining the changes in the contents of N- and NO-containing compounds with maturity allows us to propose new parameters for assessing thermal maturity that cover the full window of oil generation.

Method for the Routine Determination of Accurate Masses by Triple Quadrupole Mass Spectrometry

A new method for the measurement of accurate masses using direct infusion in an electrospray-triple quadrupole mass spectrometer is presented and compared to the traditional method using high-resolution mass spectrometry. The proposed method uses internal calibrants and post-acquisition calibration of the mass spectrum signal using the MassWorks software to determine accurate masses. Then, based on parameters such as elemental composition, number of double bond equivalents, and type of ion (even- or odd-electron), etc., a list of potential molecular formula candidates are generated and ranked according to spectral accuracy, (i.e., similarity between the calibrated profile and theoretical isotopic patterns). Experiments using six diverse synthesis products showed that mass accuracy in the Quattro Premier triple quadrupole mass spectrometer (QqQMS) was ≤9.2 mDa and spectral accuracy was ≥90.6%. According to both mass accuracy tolerance (±10 mDa) and spectral accuracy, the correct molecular formula was ranked in the top seven compounds out of up to 32 potential candidates. When considering the context of the synthesis reaction, only one formula was possible. In summary, results showed that the measurement of spectral accuracy in a low-resolution instrument such as the triple quadrupole was strongly dependent on the signal intensity and the presence of interfering peaks in the profile mass range window. This study suggests that use of triple quadrupole mass spectrometry followed by post-acquisition calibration can be an economical and robust approach compared to the traditional method using high-resolution mass spectrometers for the measurement of accurate masses in routine applications using small organic molecules at microgram-per-litter concentrations in relatively clean matrices.

A reformulated aromaticity index equation under consideration for non-aromatic and non-condensed aromatic cyclic carbonyl compounds

The extent of unsaturation level in a compound, commonly measured in terms of its number of double bond equivalents (DBEs), reflects the total number of π bonds plus rings and can be calculated if the molecular formula is known. The extent of unsaturation can also be calculated via DBE/C, where C is the number of carbon atoms. For hydrocarbons, if DBE/C is >0.67, the structure corresponds unequivocally to a condensed aromatic (CA) compound, but this criterion cannot be applied directly to heteroatom containing compounds. A new parameter, the aromaticity index (AI) was recently proposed to solve this problem, and has been applied to establish a region of CA compounds in high resolution mass spectrometry (MS) van Krevelen diagrams to characterize natural organic matter (NOM), such as humic acids (HAs). In this study, we report a reformulated AI (rAI) that also considers formulae that accommodate non-aromatic (NA) and non-condensed aromatic (NCA) cyclic carbonyl compounds. We also propose a correction for AI with respect to N and P containing formulae and show an application of the rAI index for the analysis and data treatment of a certified reference material (CRM) of NOM.

Solar photocatalytic degradation of naphthenic acids in oil sands process-affected water.

Bitumen mining in the Canadian oil sands creates large volumes of oil sands process-affected water (OSPW), the toxicity of which is due in part to naphthenic acids (NAs) and other acid extractable organics (AEO). The objective of this work was to evaluate the potential of solar photocatalysis over TiO2 to remove AEO from OSPW. One day of photocatalytic treatment under natural sunlight (25 MJ/m(2) over ∼14 h daylight) eradicated AEO from raw OSPW, and acute toxicity of the OSPW toward Vibrio fischeri was eliminated. Nearly complete mineralization of organic carbon was achieved within 1-7 day equivalents of sunlight exposure, and degradation was shown to proceed through a superoxide-mediated oxidation pathway. High resolution mass spectrometry (HRMS) analysis of oxidized intermediate compounds indicated preferential degradation of the heavier and more cyclic NAs (higher number of double bond equivalents), which are the most environmentally persistent fractions. The photocatalyst was shown to be recyclable for multiple uses, and thus solar photocatalysis may be a promising "green" advanced oxidation process (AOP) for OSPW treatment.

Comprehensive Chemical Characterization of Hydrocarbons in NIST Standard Reference Material 2779 Gulf of Mexico Crude Oil.

Comprehensive chemical information is needed to understand the environmental fate and impact of hydrocarbons released during oil spills. However, chemical information remains incomplete because of the limitations of current analytical techniques and the inherent chemical complexity of crude oils. In this work, gas chromatography (GC)-amenable C9-C33 hydrocarbons were comprehensively characterized from the National Institute of Standards and Technology Standard Reference Material (NIST SRM) 2779 Gulf of Mexico crude oil by GC coupled to vacuum ultraviolet photoionization mass spectrometry (GC/VUV-MS), with a mass balance of 68 ± 22%. This technique overcomes one important limitation faced by traditional GC and even comprehensive 2D gas chromatography (GC×GC): the necessity for individual compounds to be chromatographically resolved from one another in order to be characterized. VUV photoionization minimizes fragmentation of the molecular ions, facilitating the characterization of the observed hydrocarbons as a function of molecular weight (carbon number, NC), structure (number of double bond equivalents, NDBE), and mass fraction (mg kg(-1)), which represent important metrics for understanding their fate and environmental impacts. Linear alkanes (8 ± 1%), branched alkanes (11 ± 2%), and cycloalkanes (37 ± 12%) dominated the mass with the largest contribution from cycloalkanes containing one or two rings and one or more alkyl side chains (27 ± 9%). Linearity and good agreement with previous work for a subset of >100 components and for the sum of compound classes provided confidence in our measurements and represents the first independent assessment of our analytical approach and calibration methodology. Another crude oil collected from the Marlin platform (35 km northeast of the Macondo well) was shown to be chemically identical within experimental errors to NIST SRM 2779, demonstrating that Marlin crude is an appropriate surrogate oil for researchers conducting laboratory research into impacts of the DeepWater Horizon disaster.

Compositional Changes during Hydrodeoxygenation of Biomass Pyrolysis Oil

Hydrodeoxygenation (HDO) is usually considered as a promising process for upgrading biomass pyrolysis oil (PO) to bio-fuels. However, cognition of HDO is inhibited by the complexity of the PO and upgraded products. In this study, a PO and its upgraded pyrolysis oil (UPO) samples were analyzed by nuclear magnetic resonance, gas chromatography/mass spectrometry, and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). ESI FT-ICR MS revealed the most abundant compounds in PO were O2–O18 species with double bond equivalent (DBE) values of 0–22. After HDO, oxygen numbers gradually shifted to a range of O1–O10, and DBE number also progressively decreased. The major oxygen compounds such as carbonyls, carboxylic acids, ethers, carbohydrates, and alcohols were significantly changed with respect to relative content and molecular composition. Lignin polymers were depolymerized after reduction of the carbonyl and methoxy groups. For HDO, hydrogenation of carbonyls, car...

Lubricating Oil Dominates Primary Organic Aerosol Emissions from Motor Vehicles

Motor vehicles are major sources of primary organic aerosol (POA), which is a mixture of a large number of organic compounds that have not been comprehensively characterized. In this work, we apply a recently developed gas chromatography mass spectrometry approach utilizing "soft" vacuum ultraviolet photoionization to achieve unprecedented chemical characterization of motor vehicle POA emissions in a roadway tunnel with a mass closure of >60%. The observed POA was characterized by number of carbon atoms (NC), number of double bond equivalents (NDBE) and degree of molecular branching. Vehicular POA was observed to predominantly contain cycloalkanes with one or more rings and one or more branched alkyl side chains (≥80%) with low abundances of n-alkanes and aromatics (<5%), similar to "fresh" lubricating oil. The gas chromatography retention time data indicates that the cycloalkane ring structures are most likely dominated by cyclohexane and cyclopentane rings and not larger cycloalkanes. High molecular weight combustion byproducts, that is, alkenes, oxygenates, and aromatics, were not present in significant amounts. The observed carbon number and chemical composition of motor vehicle POA was consistent with lubricating oil being the dominant source from both gasoline and diesel-powered vehicles, with an additional smaller contribution from unburned diesel fuel and a negligible contribution from unburned gasoline.

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

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

Analysis of quaternary ammonium compounds in estuarine sediments by LC-ToF-MS: very high positive mass defects of alkylamine ions as powerful diagnostic tools for identification and structural elucidation.

A sensitive and robust method of analysis for quaternary ammonium compounds (QACs) in marine sediments is presented. Methods for extraction, sample purification, and HPLC-time-of-flight MS analysis were optimized, providing solutions to problems associated with analysis of QACs, such as dialkyldimethylammonium (DADMAC) and benzalkonium (BAC) compounds experienced previously. Recognized in this study are the exceptionally high positive mass defects characteristic of alkylammonium or protonated alkylamine ions. No alternative and chemically viable elemental formulas exist within 25.2 mDa when the number of double bond equivalents is low, effectively allowing facile discrimination of this compound class in complex mixtures. Accurate mass measurements of diagnostic collision-induced dissociation fragment ions and heavy isotope peaks were obtained and also seen to be uniquely heavy compared to other elemental formulas. The ability to resolve masses of alkylamine fragment ions is much greater than for the molecular ions of BACs and many other chemicals, opening up a range of potential applications. The power of utilizing a combination of approaches is illustrated with the identification of nontargeted DADMAC C8:C8 and C8:C10, two widely used biocides previously unreported in environmental samples. Concentrations of QACs in sewage-impacted estuarine sediments (up to 74 microg/g) were higher than concentrations of other organic contaminants measured in the same or nearby samples, suggesting that further study is needed.

Simulating terrorism : By Stephen Sloan. The University of Oklahoma Press (1005 Asp Avenue, Norman, Oklahoma 73019), 1981, 158 pp., hardcover—$12.95, softcover—$5.95

The extent of unsaturation level in a compound, commonly measured in terms of its number of double bond equivalents (DBEs), reflects the total number of π bonds plus rings and can be calculated if the molecular formula is known. The extent of unsaturation can also be calculated via DBE/C, where C is the number of carbon atoms. For hydrocarbons, if DBE/C is > 0.67, the structure corresponds unequivocally to a condensed aromatic (CA) compound, but this criterion cannot be applied directly to heteroatom containing compounds. A new parameter, the aromaticity index (AI) was recently proposed to solve this problem, and has been applied to establish a region of CA compounds in high resolution mass spectrometry (MS) van Krevelen diagrams to characterize natural organic matter (NOM), such as humic acids (HAs). In this study, we report a reformulated AI (rAI) that also considers formulae that accommodate non-aromatic (NA) and non-condensed aromatic (NCA) cyclic carbonyl compounds. We also propose a correction for AI with respect to N and P containing formulae and show an application of the rAI index for the analysis and data treatment of a certified reference material (CRM) of NOM.