Aromatic Hydrocarbons In Crude Oil Research Articles

Bioremediation of polycyclic aromatic hydrocarbons in crude oil by bacterial consortium in soil amended with Eisenia fetida and rhamnolipid.

The present study investigated the concerted effort of Eisenia fetida and rhamnolipid JBR-425 in combination with a five-member bacterial consortium exhibiting elevated degradation levels of low and high molecular weight polycyclic aromatic hydrocarbons (PAH) from soil contaminated with Digboi crude oil. Application of bacterial consortium (G2) degraded 30-89% of selected PAH from the artificial soil after a 45-day post-exposure, in which chrysene showed the highest level of degradation with 89% and benzo(a)pyrene is the lowest with 30%, respectively. Moreover, an acute exposure study observed that earthworm biomass decreased, and mortality rates increased with increasing crude oil concentrations (0.25 to 2%). Earthworms with a 100% survival rate at 1% crude oil exposure suggest the tolerance potential and its mutual involvement in the bioremediation of crude oil with selected bacterial consortia. Bacterial consortium assisted with E. fetida (G3) showed 98% chrysene degradation with a slight change in benzo(a)pyrene degradation (35%) in crude oil spiked soil. Besides, the most dominant PAH in crude oil found in the current work, fluoranthene, undergoes 93% and 70% degradation in G3 and G5 groups, respectively. However, rhamnolipid JBR-425 coupled with the bacterial consortium (G5) has resulted in 97% degradation of chrysene and 33% for benzo(a)pyrene. Overall, bacterial consortium assisted with earthworm group has shown better degradation of selected PAH than bacterial consortium with biosurfactant. Catalase (CAT), glutathione reductase (GST) activity and MDA content was found to be reduced in earthworms after sub-lethal exposure, suggesting oxidative stress prevalence via reactive oxygen species (ROS). Hence, the findings of the present work suggest that the application of a bacterial consortium, along with earthworm E. fetida, has huge potential for field restoration of contaminated soil with PAH and ecosystem sustainability.

Geochemical characteristics and significance of aromatic hydrocarbons in crude oil from the East Fukang Sag, Junggar Basin, NW China

The aromatic compounds of twenty crude oil samples from different formations in the East Fukang Sag were studied by the gas chromatography–mass spectrometry technique. Through analysis of the composition of the main aromatic hydrocarbons, the studied crude oil samples were generally divided into two types: Oil type I had the relatively high content of the naphthalene series, biphenyl series and dibenzofuran series, while the samples from Oil type II contained relatively high abundance of phenanthrene series, fluorene series, triaromatic steroid series, and obvious methyltrimethyltridecylchromans. The geochemical parameters reflecting the source and sedimentary environment in naphthalene series, phenanthrene series, biphenyl series, three-fluorene series, and triaromatic steroid series were systematically analyzed. Analysis of the results showed that studied oil samples from the East Fukang Sag were of continental origin and deposited in a weakly oxidizing to weakly reducing environment with fresh-brackish water. Oil type I was characterized by considerably abundant terrestrial higher plant organic matter inputs, while Oil type II was typical with obviously lower aquatic organisms. Maturity-related parameters calculated from alkyl naphthalenes, alkyl phenanthrenes, alkyl dibenzothiophenes, and methyltrimethyltridecylchromans showed that all the studied oil samples have reached the mature stage.

Effect of methyl substituents on the biodegradation of two-ring polycyclic aromatic hydrocarbons in crude oil identified by aerobic biodegradation simulations

Existing studies determining the effects of substituted methyl groups on polycyclic aromatic hydrocarbon biodegradation were mostly limited to an individual compound or a class of compounds. The simultaneous transformation of the multiple series of methyl-substituted two-ring polycyclic aromatic hydrocarbons (61 compounds) in crude oil through laboratory simulations has been examined, including naphthalenes, fluorenes, biphenyls, and dibenzofurans. The biodegradation sequences were in the order of dimethylnaphthalenes > trimethylnaphthalenes > biphenyls > dibenzofurans, tetramethylnaphthalenes > pentamethylnaphthalenes > fluorenes. Polycyclic aromatic hydrocarbon biodegradation was depending on both the number and the position of methyl substituents. For naphthalenes, fluorenes, biphenyls, and dibenzofurans, the more methyl groups in the parent compound, the more resistant it was to biodegradation. Among the polycyclic aromatic hydrocarbons with the same number of methyl groups, the more ortho-methyl substitutes, the more challenging it was to be decomposed. In the case of dimethylnaphthalenes or trimethylnaphthalenes with the same number of methyl and ortho-methyl substituents, their biodegradability reduced as the number of α substituents increased. The number of ortho-methyl substituents had a greater impact than that of α/β substituents. The relative significance of these two factors has not been confirmed in previous studies.

Geochemical characteristics and mechanisms of densification of pre-Jurassic crude oil in the Tainan Sag, Turpan-Hami Basin, China

Large volumes of heavy oil were distributed in the pre-Jurassic strata of Tainan sag, Turpan Hami Basin, China. The geochemical characteristics and origins of heavy oil are of great significance to future exploration in the region. In this study, we classified crude oil using data on its physical properties, group composition, and biomarker compounds. Further, the distribution characteristics of different types of crude oil in horizontal and vertical directions are clarified. We also summarize the mechanism of densification of crude oil in the study area. Our results indicate that there are four categories of crude oil with different densities in the Tainan Sag, which are distributed across the areas of (from west to east) Tuyuke, Lukeqin, and Yingyeer: light oil (<0.9/cm3), heavy oil (0.9–0.93 g/cm3), extra-heavy oil (0.93–0.98 g/cm3), and ultra-heavy oil (>0.98 g/cm3). Notable differences were observed in the composition of these distinct crude oil types. As the densification degree of crude oil increases, the content of saturated hydrocarbon and aromatic hydrocarbon decreases gradually, and the content of asphaltene increases gradually. The light oil in the Tuyuke area of the Tainan Sag has undergone severe water washing and slight-to-moderate biodegradation. The extra-heavy oil in the Lukeqin area has undergone severe water washing but moderate-to-severe biodegradation. The ultra-heavy oil in the Yingyeer area has not undergone notable water washing but has been subjected to severe biodegradation. Biodegradation damages saturated hydrocarbons and aromatic hydrocarbons in crude oil to varying degrees, increasing the relative content of non-hydrocarbon constituents and asphaltenes and causing the oil to thicken gradually. This occurrence is highly common in areas of severe strata erosion. Water washing, usually occurring in the interlayers where oil and water are in contact with each other over a large area, causes densification of the oil by destroying the low-carbon aromatics in it. This study determined the geochemical characteristics, as well as the reservoir geology of crude oil under various causes of densification and, can serve as a scientific reference for research on the mechanisms of densification of crude oil in other locations.

Characteristics of Aromatic Hydrocarbons and Its Stable Carbon Isotope Compositions in Crude Oils

In this paper, relative contents, characteristic ratios and stable carbon isotope compositions of aromatic hydrocarbons in crude oils were determined from different areas. In terms of aromatic hydrocarbons relative contents, two kinds of crude oils have shown their own features. From the characteristics of the ratios of aromatic hydrocarbon in crude oil, the maturity parameters (MNR, TNR1, TNR2, MPR, MPI1, MPDF1 and MPDF2) reflected high maturity of all the crude oil. Other parameters, such as DNR1, DNR2 and TNR4, revealed the organic source and biodegradation of crude oil and other information. From the compositions of stable carbon isotope of aromatic hydrocarbons in crude oils, crude oils between the various regions have the differences. Plots of aromatic hydrocarbon ratios versus δ13 C values of dimethylnaphthalene and phenanthrene were constructed to discriminate crude oils from different areas. The results demonstrate that this method can distinguish different kinds of crude oisl more effectively.

Degradation of poly aromatic fractions of crude oil and detection of catabolic genes in hydrocarbon-degrading bacteria isolated from Agbabu bitumen sediments in Ondo State.

Pollution due to release of Poly aromatic hydrocarbons (PAHs) are a major environmental issue especially in oil producing communities. This study investigates the polyaromatic hydrocarbon degradation potentials of some bacteria: Campylobacter hominis, Bacillus cereus, Dyadobacter koreensis, Pseudomonas aeruginosa and Micrococcus luteus isolated from Agbabu bitumen sediments in Ondo State. The isolates were used singly and in consortium for the degradation of Bonny light crude oil. Concentrations of residual aromatic hydrocarbons in crude oil degraded by these isolates were determined by Gas chromatography/Mass Spectroscopy with flame ionization detector (FID). Detection of catabolic genes (nahH, CatA and AlkB) in the isolates was determined by PCR amplification of their specific primers. The GC-MS analyses showed degradation of poly aromatic hydrocarbons (PAHs) by these isolates. The consortium exhibited the highest PAH reduction (73%) while C. hominis had the least PAH reduction (56%). Dyadobacter koreensis, P. aeruginosa, Micrococcus luteus and B. cereus, displayed 66%, 60%, 59% and 58% PAH reduction respectively. The catabolic gene nahH gene was present in B. cereus, D. koreensis, P. aeruginosa and M. luteus, alkB gene was present in B. cereus, C. hominis, and D. koreensis while CatA was not detected in any of the isolates. The findings of this study affirmed the hydrocarbon-degrading abilities and presence of catabolic genes in these bacteria, these make them potential tools in oil prospecting and cleaning up of hydrocarbon contaminated sites.

Assessment of the biodegradation capacity of Azolla on polycyclic aromatic hydrocarbons in crude oil

&lt;p&gt;In this study, the potential use of Azolla filiculoides Lam. for the bioremediative solution to polycyclic aromatic hydrocarbon (PAH) pollution due to crude oil spills in freshwater was investigated. The plants were grown in nitrogen-free Hoagland nutrient solution media containing 0.05%, 0.1%, 0.2%, 0.3%, 0.4% and 0.5% crude oil by volume for 15 days under greenhouse conditions. Relative growth rates of A. filiculoides decreased in the presence of crude oil in a concentration-dependent manner. The probable influence of A. filiculoides on the biodegradation of polycyclic aromatic hydrocarbons was measured by using synchronous UV fluorescence spectroscopy. GC-MS analysis were also carried out to elucidate the behavior of the oil in experimental and control samples. Although 1-2 rings PAHs have not been encountered in control or plant samples, the measured intensity for 3-4 ring PAHs in plant samples was remarkably lower in comparison to the control. Furthermore, these results demonstrated that the predominant efficacy of the A. filiculoides was for 3-4 ring PAHs at the range 0.05 to 0.2% crude oil concentrations. It could be concluded that the bioremediative potential of A. filiculoides for the removal of polycyclic aromatic hydrocarbons strongly depends on the amount of oil in the contaminated water resource. In other words, A. filiculoides could be used more effectively after the removal of excess crude oil in the spilled freshwater areas.&lt;/p&gt;&#x0D;

Exploring the novel indigenous strains for degrading the crude oil contaminants in soil sample

Soil hydrocarbon pollution often causes the crop quality and safety issue. Therefore, a high priority is given to exploring the novel bacterial strain to sustainable green agricultural food products. Two novel crude oil-degrading bacteria were screened from the local oil-contaminated soil, which exhibited a good emulsifying capacity in their oil spreading test, showing their most clearing zone on the oil covering petri dish. Glycolipid bio-surfactant was identified by the thin-layer chromatography analysis. Gas chromatography and ultraviolet spectrophotometer (UV) methods were used to evaluate the degradation degree of alkanes and aromatic hydrocarbons in crude oil. The biodegradation ability of a single strain was inferior to mixed strains. The latter revealed that the degradation of the crude oil was 92% and 85%, respectively, when cultured at 32 °C, 150 rpm for 20 days. The hardest degraded isoprenoid alkane (pristane) could easily be degraded by these mixed strains. The effect of cadmium (Cd) on the growth of isolated strains was also studied, and the results demonstrate that crude oil-degrading bacteria isolated in the present study have shown strong endurance to Cd2+ (IC50 were 228.80 mg L−1 and 97.74 mg L−1) for Pseudomonas aeruginosa Dut-lxm0725 and Rhodococcus erythropolis Dut-lxm1018 strains, respectively. The above results suggest that present wild strains could have a good application prospect in bioremediation of crude oil-contaminated soil.

Time Course-Dependent Methanogenic Crude Oil Biodegradation: Dynamics of Fumarate Addition Metabolites, Biodegradative Genes, and Microbial Community Composition.

Biodegradation of crude oil in subsurface petroleum reservoirs has adversely impacted most of the world's oil, converting this resource to heavier forms that are of lower quality and more challenging to recover. Oil degradation in deep reservoir environments has been attributed to methanogenesis over geological time, yet our understanding of the processes and organisms mediating oil transformation in the absence of electron acceptors remains incomplete. Here, we sought to identify hydrocarbon activation mechanisms and reservoir-associated microorganisms that may have helped shape the formation of biodegraded oil by incubating oilfield produced water in the presence of light (°API = 32) or heavy crude oil (°API = 16). Over the course of 17 months, we conducted routine analytical (GC, GC-MS) and molecular (PCR/qPCR of assA and bssA genes, 16S rRNA gene sequencing) surveys to assess microbial community composition and activity changes over time. Over the incubation period, we detected the formation of transient hydrocarbon metabolites indicative of alkane and alkylbenzene addition to fumarate, corresponding with increases in methane production and fumarate addition gene abundance. Chemical and gene-based evidence of hydrocarbon biodegradation under methanogenic conditions was supported by the enrichment of hydrocarbon fermenters known to catalyze fumarate addition reactions (e.g., Desulfotomaculum, Smithella), along with syntrophic bacteria (Syntrophus), methanogenic archaea, and several candidate phyla (e.g., “Atribacteria”, “Cloacimonetes”). Our results reveal that fumarate addition is a possible mechanism for catalyzing the methanogenic biodegradation of susceptible saturates and aromatic hydrocarbons in crude oil, and we propose the roles of community members and candidate phyla in our cultures that may be involved in hydrocarbon transformation to methane in crude oil systems.

Multidimensional Gas Chromatography–Mass Spectrometry Method for Fingerprinting Polycyclic Aromatic Hydrocarbons and Their Alkyl-Homologs in Crude Oil

ABSTRACTThe composition of polycyclic aromatic hydrocarbons in crude oil is usually too complex to use standard capillary gas chromatography to separate all of the components. In this study, a multidimensional gas chromatography–mass spectrometry (GC-MS) technique was used to analyze polycyclic aromatic hydrocarbon fractions of crude oil collected from the Dongying oil field in the Bohai Sea. A DB-17MS column (30 m × 0.25 mm × 0.25 µm) was used as a prefractionating column and only selected heart-cuts were transferred to the second chromatographic dimension (HP-5MS, 15 m × 0.25 mm × 0.25 µm) by a pressure-adjusted continual flow-type switching device for quantification of the polycyclic aromatic hydrocarbons. The chromatographic elements and parameters, such as detector selection and column combinations, were optimized. Naphthalene, phenanthrene, fluorene, dibenzothiophene, chrysene, and their C1–C4 alkyl homologs were identified. The profile of the polycyclic aromatic hydrocarbons obtained using the multidimensional GC-MS method was compared with the results obtained by traditional one-dimensional GC-MS.

Composition of alkyl arenes of Phanerozoic oils

We summarize the results of our long-term research into the composition of alkyl derivatives of mono-, bi-, and tricyclic aromatic hydrocarbons of 113 crude oils from the Cenozoic (Sakhalin, Pannonian Basin (Serbia), China, and Vietnam), Cretaceous (West Siberia, Mongolia, China, and Saxony), Jurassic (West Siberia and Saxony), and Paleozoic (West Siberia, East Siberia, and Timan-Pechora and Volga-Ural petroliferous provinces) deposits localized at depths from 200 to 4500 m. To identify compositional similarities and differences of crude oils from deposits of different ages, we processed the obtained data on the individual composition of alkanes, alkyl benzenes, alkyl naphthalenes, and alkyl phenanthrenes by principal-component analysis. The analysis has revealed the regularities of changes in the content and composition of alkyl aromatic hydrocarbons in crude oils depending on the age of the enclosing deposits.

Determination of volatile organic and polycyclic aromatic hydrocarbons in crude oil with efficient gas-chromatographic methods.

Determination of volatile organic compounds (VOCs) in crude oil, such as super volatile organic compounds (super VOCs) and simple polycyclic aromatic hydrocarbons (PAHs), is vital for targeting crude oil spill spots. In this study, a static headspace gas chromatography flame ionization detection method was established for determination of super VOCs in crude oil with both external and internal standard determination, which can be used in the field when using portable gas chromatography. Identification was done by comparing the retention time with the corresponding standards and quantitation was done with a new one-drop method. Another simplified and efficient method was performed to analyze volatile PAHs in crude oil, which can also be used in field analysis. Toluene was used as the extraction solvent for PAHs in crude oil. Method validation for both analyses was satisfactory. The result showed that n-butane and n-pentane were maximum super VOCs and naphthalene, phenanthrene and fluorene were the main PAHs in the crude oil studied. The super VOCs quantity ranged from 3 to 6% and the main PAHs consisted of 0.02-0.06% of studied crude oil.

Geochemical characteristics of aromatic hydrocarbons in crude oils from the Linnan Subsag, Shandong Province, China

Abundant aromatic fractions were detected in oils from the Linnan subsag, including aphthalenes, phenanthrenes, triaromatic steroids, biphenyl, fluorenes, dibenzothiophenes, dibenzofuranes, as well as some typical higher plant-sourced compounds, such as pyrene, benzopyrene, fluoranthene, chryaene, benzofluoranthrene, perylene and cadalene. Occurrences of biomarkers indicate that oils from the Linnan subsag are typical terrestrially genetic oils. Developed in the depositional environment is a strong reduction condition typical of brackish-saline lake. Thermal evolution has entered into the mature-high mature stage.

Geochemical characterization of aromatic hydrocarbons in crude oils from the Tarim, Qaidam and Turpan Basins, NW China

Based on the systematic study of aromatic hydrocarbons in over 100 crude oil samples collected from the Tabei and Tazhong uplifts in the Tarim Basin, the western depression area in the Qaidam Basin and the Tabei depression in the Turpan Basin, the geochemical characteristics of the marine (Tarim Basin), saline lacustrine (Qaidam Basin), and swamp (Turpan Basin) oils were investigated. The marine oils from the Tarim basin are characterized by relatively low abundance of diaromatic hydrocarbons such as biphenyl and naphthalene, and relatively high abundance of triaromatic hydrocarbons including phenanthrene, dibenzothiophene and fluorene. In contrast, the swamp oils from the Turpan Basin are dominated by the highest relative abundance of diaromatic hydrocarbons and the lowest relative abundance of triaromatic hydrocarbons in all the oil samples in this study. The relative abundance of diaromatic and triaromatic hydrocarbons in the saline lacustrine oils from Qaidam Basin is between that in Tarim oils and Turpan oils. Aromatic parameters based on the isomer distributions of dimethylnaphthalenes (DMN), trimethylnaphthalenes (TMN), tetramethylnaphthalenes (TeMN) and methylphenanthrenes (MP), i.e., 1,2,5-trimethylnaphthalene(TMN)/1,3,6-TMN ratio, 1,2,7-TMN/1,3,7-TMN ratio, (2,6-+2,7-)-dimethylnaphthalenes (DMN)/1,6-DMN ratio, 1,3,7-TMN/(1,2,5- +1,3,7-)-TMN, 1,3,6,7-TeMN/(1,3,6,7- +1,2,5,6- +1,2,3,5-)-TeMN ratio and MP index, may reflect the diversity of organic source input, thermal maturity and depositional environments. In addition, the dibenzothiophenes (DBTs)/fluorenes(Fs) and dibenzofurans (DBFs)/Fs ratios were found to the very useful and effective in determining genetic types of crude oils for the marine, saline lacustrine, and swamp depositional environments, and for oil-oil correlations.

A refinery sludge deposition site: presence of nahH and alkJ genes and crude oil biodegradation ability of bacterial isolates

204 bacterial isolates from four Greek refinery sludge deposition sites were investigated for the presence of nahH and alkJ genes encoding key enzymes of both aromatic and aliphatic hydrocarbon degradation pathways by PCR and DNA hybridisation. Members of Pseudomonas, Acinetobacter, Bacillus, Rhodococcus and Arthrobacter play important role in bioremediation processes in sandy/loam soil contaminated with oil and nahH and alkJ genes were present in the 73% of the isolates. Consortia of bacterial isolates that were used for biodegradation of aliphatic and aromatic hydrocarbons in crude oil using liquid cultures exhibited rates from 35% to 48% within 10 days of incubation.

Characterization of non-polar aromatic hydrocarbons in crude oil using atmospheric pressure laser ionization and Fourier transform ion cyclotron resonance mass spectrometry (APLI FT-ICR MS)

We report on the successful application of the recently introduced atmospheric pressure laser ionization (APLI) method as a novel tool for the analysis of crude oil and its components. Using Fourier transform ion cyclotron resonance mass spectrometry, unambiguous determination of key compounds in this complex matrix with unprecedented sensitivity is presented.

Aquatic ecotoxicity due to oil pollution in the Ecuadorian Amazon

One of the major environmental impacts of oil exploration in the Ecuadorian Amazon region is the contamination of the aquatic environment. In addition to occasional major oil spills, there are several minor sources. This study investigates aquatic toxicity due to seepage from production pits and oiled road run-off. Water and sediment samples were collected and acute toxicity was determined in Daphnia magna and Hyalella azteca bioassays. Because exposure to ultra-violet radiation may enhance the toxicity of several polycyclic aromatic hydrocarbons in crude oil, toxicity was studied before and after exposure to natural sunlight in the field using a microbiotest or solar-simulating ultra-violet light in the laboratory using cultured organisms. Total petroleum hydrocarbon concentrations of analyzed sediments ranged from 4.9 to 6980 mg kg−1 dry weight (dw). Immobility and lethality ranged from 0 to 100% in Daphnia magna and from 0 to 40% in Hyalella azteca. The micro-biotest results were generally confirmed by the tests on cultured Daphnia. A river exposed to oiled road run-off and a pond used for drinking water, 100-m from a production pit, had the highest total petroleum hydrocarbon concentrations. These samples were toxic compared to reference sites. The response increased upon light exposure, suggesting polycyclic aromatic hydrocarbon availability. Minor water phototoxicity was also observed in the drinking water pond (having ten times the total petroleum hydrocarbon concentration nationally allowed in drinking water). Thus, the seepage from unlined production pits and the practice to use oil for dust control on roads in the area pose environmental and human health hazards.

Isolation and characterization of novel hydrocarbon-degrading euryhaline consortia from crude oil and mangrove sediments.

Two novel and versatile bacterial consortia were developed for the biodegradation of hydrocarbons. They were isolated from crude oil from the Cormorant Field in the North Sea (MPD-7) and from sediment associated with mangrove roots (MPD-M). The bacterial consortia were able to degrade both aliphatic and aromatic hydrocarbons in crude oils very effectively in seawater (35 g/L NaCl) and synthetic media containing 0 to 100 g/L NaCl (1.7 M). Salinities over twice that of normal seawater decreased the biodegradation rates. However, even at the highest salinity biodegradation was significant. Ratios of nC17 to pristane and nC18 to phytane were significantly lowered across the range of salinity. The lowest values were at 0 and 20 g/L (0.34 M). Phytane was degraded in preference to pristane. The degradation of these compounds was constant over the salinity range, with evidence of a slight increase for consortium MPD-M with increasing salinity. In general, the consortium isolated from mangrove root sediments was more efficient in metabolizing North Sea crude oil than the consortium isolated from Cormorant crude oil. The 5 strains that comprise MPD-M have been tentatively identified as species of the genera Marinobacter, Bacillus, and Erwinia. This is the first report of hydrocarbon-degrading consortia isolated from crude oil and mangrove sediments that are capable of treating oily wastes over such a wide range of salinity.

Characteristics of aromatic hydrocarbons in crude oils

Crude oils from different basins in China, Australia and New Zealand were analyzed to character ize aromatic hydrocarbons produced in different environments by means of GC/MS. The distributions of some common compounds such as naphthalene, phenanthrene, ehrysene, pyrene, fluoranthene, fluorene, dibenzothiophene and dibenzofuran were found to be related to sedimentary environments. Especially the relative contents of fluorenes, dibenzofurans and dibenzothiophenes can be used to divide the oils into three types: (1) saline or marine carbonate environment; (2 ) fresh-brackish water lake; (3) swamp and coal-bearing sequence. Aromatic biomarkers (e.g. retene, nor-abietene, derivatives of lupeol and β-amyrin) represent higher plant inputs with respect to the precursors of crude oils. High contents of sulphur-containing compounds like benzothiophene and dibenzothiophene series indicate a reducing sulphur-abundant diagenetic condition. The benzohopane series (C32–C35) was identified both in hypersaline and coal-bearing basins, and it is postulated to be the result of strong bacteria activity. In all the samples, a complete series of alkyl benzenes was analyzed. The similarity of its carbon-number distribution with that of n-alkanes probably suggests their genetic relationship. The distribution of the methylphenanthrene series reflects the evolution degree of crude oils, MPI holding a positive correlation with C29-sterane 20S/(20S+20R).

Direkte Analyse von Dimethylnaphthalinen in Erdölen mittels zweidimensionaler Kapillar-Gas-Chromatographie

Quantitation of dimethylnaphthalenes in crude oils by means of two-dimensional capillary gas chromatography.) Occurrence and behaviour of aromatic hydrocarbons in crude oils and bitumina are thoroughly investigated in organic geochemistry. For instance, concentration ratios derived from alkylnaphthalene and alkylphenanthrene isomer distribution are applied for the assessment of the geological and thermal history of sedimentary organic matter. The present contribution focusses on the separation and quantitation of 1,4-, 2,3- and 1,5-dimethylnaphthalenes in crude oils by two-dimensional capillary gas chromatography. Usually, the separation of these isomers cannot be achieved without difficulties on a single stationary phase. The geochemical interest arises from the application of the 2,3- to 1,4-dimethylnaphthalene concentration ratio as a“maturity parameter”. Another advantage of the method is, in addition to the speed of the analysis, the possibility to analyse original. untreated crude oil samples, i.e., with no further preseparation.