Crude oils containing large quantities of waxes, and in situations where sudden temperature drops occur, a crystalline network can be formed, generating flow difficulties in production, transfer and offloading lines. Despite the scientific and economic importance of this phenomenon, correlations between the behavior of petroleum in relation to its pour point are scarce in the literature. In this work, nine crude oil samples were characterized regarding density, water content, wax fraction (one- and two-dimensional chromatography), pour point, yield stress and wax appearance temperature. The results showed that the storage conditions and oil characteristics had a strong influence on the pour point. Yield stress was influenced by initial temperature of the sample, cooling rate and shear rate during cooling. Finally, the content of aromatic compounds in oil with low concentration of n-alkanes can contribute to increase the pour point.

Este trabalho apresenta um estudo comparativo de diferentes processos de oxidação fotoquímica e uma detalhada caracterização dos subprodutos da degradação de óleo diesel utilizando cromatografia gasosa bidimensional abrangente acoplada à espectrometria de massas por tempo de voo (GC×GC-TOFMS). A degradação de óleo diesel foi realizada em um reator fotolítico usando UV, H2O2, UV/H2O2, O3 ou O3/UV. As melhores condições para cada processo foram otimizadas por análise multivariada e os resultados experimentais indicaram que o processo O3/UV foi o mais viável para o tratamento de efluentes contendo óleo diesel, com uma porcentagem de degradação maior que 90%. A degradação quase completa dos compostos aromáticos foi alcançada. Compostos fenólicos foram identificados como subprodutos das amostras de óleo diesel tratadas com os processos UV, H2O2, O3 e O3/UV. Além desses compostos, outros subprodutos identificados incluem ácidos carboxílicos e éteres no tratamento com UV/peróxido, éteres no tratamento com radiação UV e cetonas no tratamento com ozônio.

This paper provides a comparative study of different photochemical oxidation processes and a detailed characterization of the by-products of diesel oil degradation performed using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Diesel degradation was conducted in a photolytic reactor using UV, H2O2, UV/H2O2, O3 or O3/UV. The best conditions for each process were obtained applying multivariate analysis and the experimental results indicated that the O3/UV process was the most feasible for the treatment of wastewater containing diesel fuel, with a degradation percentage of > 90%. Almost complete degradation of the aromatics was achieved. Phenolic compounds were identified as by-products of the diesel samples treated with the UV, H2O2, O3 and O3/UV processes. Besides the phenolic compounds, other by-products identified included carboxylic acids and ethers in the UV/peroxide treatment, ethers in the UV irradiation treatment and ketones in the ozone treatment.

A complete analysis of oils and their fractions allows correlations to be defined between their composition and derivatives or related geological materials. This work focused on optimization and implementation of a method for separation and quantification of n-alkanes in Brazilian oil samples by urea adduction and GC-FID techniques. Ten samples with different ºAPI were analyzed in triplicate to quantify individual n-alkanes and cyclic/branched alkane fraction. For individual quantification of n-alkanes, internal standardization with deuterated n-tetracosane was used. The use of urea adduction for the separation and quantification of n-alkanes was highly effective, with recovery values of above 80%.

Cromatografia gasosa bidimensional abrangente acoplada à espectrometria de massas por tempo de voo (GC×GC-TOFMS) é uma técnica apropriada para a elucidação da composição molecular de amostras petroquímicas, como óleos biodegradados. Biomarcadores foram separados, identificados e razões de biomarcadores convencionais foram determinados usando cromatografia gasosa acoplada à espectrometria de massas (GC-MS) e GC×GC-TOFMS. No cromatograma de íons extraídos m/z 123 + 177 + 191, coeluições entre terpanos tricíclicos, hopanos e 25-nor-hopanos com secohopanos foram resolvidas usando GC×GC-TOFMS. GC×GC-TOFMS permitiu a identificação da série completa dos 25-nor-hopanos, nor-gamacerano, C29 28-nor-espergulano e oleanano, que não foram identificados por GC-MS. A avaliação dos parâmetros geoquímicos dos óleos estudados indicou uma origem marinha e um ambiente deposicional sob condições anóxicas. A alta resolução cromatográfica e sensibilidade alcançada usando GC×GC-TOFMS permitiram sugerir três novos parâmetros geoquímicos para a caracterização de óleos altamente biodegradados. Estes resultados demonstram a superioridade da técnica GC×GC-TOFMS na separação e identificação de compostos individuais e não-alvos em óleos severamente biodegradados

Comprehensive two-dimensional gas chromatography with time of flight mass spectrometry (GC×GC-TOFMS) is an appropriate technique for the elucidation of molecular composition of petrochemical samples, such as biodegraded oils. Biomarkers were separated and identified, and conventional biomarker ratios were determined via gas chromatography-mass spectrometry (GC-MS) and GC×GC-TOFMS. In the extracted ion chromatogram m/z 123 + 177 + 191, coelutions between tricyclic terpanes, hopanes and 25-nor-hopanes with secohopanes were resolved by GC×GC-TOFMS. GC×GC-TOFMS allowed the identification of complete series of 25-nor-hopanes, nor-gammacerane, C29 28-nor-spergulanes and oleanane not identified by using GC-MS. The biomarker ratios from the studied oils indicated that they derived from marine source rock deposited under anoxic conditions. The higher chromatographic resolution and sensitivity achieved by using GC×GC-TOFMS allowed for three new parameters to characterize biodegraded oils. These results indicated the superiority of GC×GC-TOFMS for separation and identification of individual and non-target compounds in severely biodegraded oils.

A cromatografia gasosa bidimensional abrangente acoplada à espectrometria de massas por tempo de vôo (CG×CG-EMTDV) foi aplicada para avaliar o efeito do CO2 sobre a distribuição dos n-alcanos, alcanos ramificados, alquenos e compostos oxigenados em produtos da reação de Fischer-Tropsch. Coeluições de material não resolvido observadas em CG convencional foram resolvidas por CG×CG-EMTDV.

Comprehensive two-dimensional gas chromatography coupled to time of flight mass spectrometry (GC × GC-TOFMS) was applied to evaluate the CO2 effect on distribution of n-alkanes, branched alkanes, alkenes and oxygen-containing compounds in Fischer-Tropsch products. GC × GC-TOFMS was able to resolve the unresolved compounds observed in conventional GC.

A composição química de amostras de âmbar provenientes da Bacia do Recôncavo (Salvador, Bahia), datadas do Cretáceo Inferior, foi determinada por meio de CG-EM para caracterização das suas possíveis fontes botânicas. Os principais compostos identificados foram diterpenoides, tais como abietano, deidroabietano, tetraidroreteno, deidroabietol, ácido deidroabiético, ferruginol e sugiol. Outras classes de diterpenoides ou triterpenos não foram detectados. A composição dos extratos e os dados quimiotaxonômicos permitiram relacionar as amostras com coníferas das famílias Podocarpaceae ou Cheirolepidiaceae devido à detecção do ferruginol, um biomarcador específico para estas famílias. Desta forma, os dados concernentes aos âmbares da Bacia do Recôncavo forneceram informações quanto à presença de uma flora resinífera na Formação Maracangalha, quando da deposição de seus sedimentos durante o Cretáceo Inferior.

The chemical composition of Lower Cretaceous amber samples from Recôncavo Basin (Salvador, Bahia) was performed by GC-MS to characterize possible botanical sources. The compounds identified were hydrocarbonic and polar diterpenoids, such as abietane, dehydroabietane, tetrahydroretene, dehydroabietol, dehydroabietic acid, ferruginol and sugiol. Other diterpenoid classes were not detected as well as triterpenoids. The composition of the extracts and chemosystematic data allows relating the samples to conifers of Podocarpaceae or Cheirolepidiaceae families due to detection of ferruginol, a specific biomarker to these families. The data concerning Cretaceous amber in the Recôncavo Basin provided information concerning the presence of a resinous flora in the Maracangalha Formation sediments during the Lower Cretaceous.

Espectros de ressonância magnética nuclear de 13C com polarização cruzada e rotação no ângulo mágico (RMN-CPMAS de 13C) foram obtidos pela primeira vez para três amostras de âmbar provenientes do Mesozóico da América do Sul. As amostras foram datadas como pertencentes ao Cretáceo Inferior e coletadas em sedimentos das bacias do Amazonas, Araripe e Recôncavo, Brasil. Todas as amostras apresentaram espectros muito similares, o que é consistente com uma fonte paleobotânica em comum. Algumas características dos espectros, tais como sinais mais intensos entre 38-39 ppm, sugerem relação entre os âmbares brasileiros e a família Araucariaceae. Todas as amostras são formadas de estruturas polilabdânicas que permitem associação com resinas de Classe Ib, estruturalmente constituídas por polímeros de diterpenos labdânicos. Informações quanto às mudanças estruturais ocorridas durante a maturação, tais como isomerização de insaturações Δ8(17) e Δ12(13), também foram obtidas pelas análises por RMN-CPMAS de 13C. Os resultados quanto à origem botânica das amostras são concordantes com aqueles alcançados por análises mediante cromatografia gasosa acoplada à espectrometria de massas (GC-MS).

13C cross polarization with magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectra have been obtained for the first time to three Cretaceous amber samples from South America. The samples were dated to Lower Cretaceous and collected in sediments from the Amazonas, Araripe and Recôncavo basins, Brazil. All samples have very similar spectra, consistent with a common palaeobotanical source. Some aspects of the spectra suggest a relationship between Brazilian ambers and Araucariaceae family, such as intense resonances at 38-39 ppm. All samples are constituted by polylabdane structure associated to Class Ib resins, constituted by polymers of labdanoid diterpenes. Finally, information concerning some structural changes during maturation, such as isomerization of Δ8(17) and Δ12(13) unsaturations, were obtained by 13C NMR analyses. The results concerning botanical affinities are in accordance with previous results obtained by gas chromatography-mass spectrometry (GC-MS).

Aromatic compounds are still poorly evaluated in geochemical studies of Brazilian oil samples. For this reason, the objective of this work was to analyze and evaluate 26 oil samples from four Brazilian sedimentary basins. Aromatic hydrocarbon fractions have been analyzed by gas chromatography coupled to mass spectrometry. The results were also compared with previously evaluated saturated hydrocarbon data. Maturation parameters obtained using the 4- and 1-methyl-dibenzothiophenes and trimethyl-dibenzothiophenes led to the best results because a better grouping was observed. For this correlation, the samples were grouped by maturity degree enabling the routine use of these parameters to evaluate oil maturity levels.

Este estudo concentra-se nos sistemas estuarinos tropicais de Mundaú-Manguaba (MMELS) e do Rio Paraíba do Sul (PSR), ambos no Brasil e afetados por práticas da monocultura da cana-de-açúcar e por urbanização. Os níveis de 17 hidrocarbonetos policíclicos aromáticos (HPAs), 16 dos quais são classificados como poluentes prioritários para estudos ambientais pela US-EPA e o perileno (HPA biogênico) foram avaliados nos sedimentos superficiais para identificar fontes da poluição e determinar níveis base como estratégias para gerenciamentos futuros. O Σ16HPAs variou de 2,90 a 231,30 μg kg-1 em MMELS e de 87,10 a 9344,29 μg kg-1 no PSR. As relações entre HPAs isômeros sugeriram principalmente fontes de origem pirogênica.

This study focuses on the tropical estuarine systems of Mundaú-Manguaba (MMELS) and Paraíba do Sul River (PSR), Brazil, affected by sugarcane monoculture practices and also urbanization. The levels of 17 polycyclic aromatic hydrocarbons (PAHs), 16 of which are classified as priority pollutants by the US-EPA and perylene (a biogenic PAH) were measured in surface sediments to identify pollution sources and determine baseline data looking for future management strategies. The Σ16PAH ranged from 2.90 to 231.30 μg kg-1 in MMELS and from 87.10 to 9344.29 μg kg-1 in the PSR. PAH isomeric ratios suggested mainly pyrogenic input.

Triazinas foram analisadas no sistema tropical estuarino lagunar de Mundaú-Manguaba (MMELS), Estado de Alagoas, NE-Brasil, impactado pela monocultura de cana-de açúcar na sua bacia de drenagem. Amostras de água e sedimento foram coletadas em agosto/2006 (estação chuvosa) e fevereiro/2008 (estação seca da colheita) para determinação das triazinas: atrazina, simazina, desetilatrazina, desisopropilatrazina e desetil-desisopropilatrazina na fase dissolvida, no material particulado em suspensão e no sedimento de superfície. Amostras de água foram filtradas e após procedimento analítico, os extratos obtidos foram analisados por cromatografia gasosa acoplada a espectrometria de massas (CG-EM). O método de análise para as triazinas em material particulado foi avaliado, obtendo recuperações entre 72-123 %, desvios padrão relativo de 4,2-22 % e limites de detecção de 0,2-0,3 ng L-1. Sedimentos fortificados a 10, 20 e 50 ng g-1 foram extraídos em sistema de extração acelerada por solvente (ASE) e as recuperações foram de 68-133%, desvio padrão relativo de 2-34 % e o limite de detecção de 0,6-1,2 ng g-1. Somente a atrazina foi detectada e em amostras de material particulado em suspensão durante a estação chuvosa em quatro pontos. As concentrações determinadas foram 3,1, 2,7, 1,6 e 0,7 ng L-1. Estes resultados sugerem que as triazinas são amplamente retidas e transformadas e/ou estejam sendo diluídas nas águas e degradadas devido ao metabolismo intenso no MMELS.

This study addresses triazines in the tropical and eutrophic Mundaú-Manguaba estuarine-lagoon system (MMELS) located in the State of Alagoas, NE-Brazil, affected by sugar-cane monoculture in its lower drainage basin. Water and sediment samples from MMELS were collected during the wet post-harvest season (August/2006) and the dry harvest season (February/2008). Trace analysis of the triazines atrazine, simazine, deethylatrazine, deisopropylatrazine and deethyldeisopropylatrazine were performed in surface sediments, suspended particulate matter and in the dissolved fraction in water. Water samples were filtered and after the analytical procedures, the resulting extracts were analyzed by gas chromatography-mass spectrometry. Additionally, the analytical method for suspended particulate matter was evaluated, the recovery being between 72-123 % with relative standard deviations of 4.2-22 % and limits of detection around 0.2-0.3 ng L-1. Sediments fortified at 10, 20 and 50 ng g-1 were extracted with the ASE system and recovery experiments lied between 68-133 % with relative standard deviations of 2-34 %. The limits of detection were of 0.6-1.2 ng g-1. Atrazine was the sole triazine detected and only in suspended particulate matter during the wet season at four sites, with low concentrations of 3.1, 2.7, 1.6 and 0.7 ng L-1. This suggests that triazines are either largely retained and transformed within the sugar-cane fields and/or are readily diluted in the waters and degraded due to the intense metabolism of MMELS.

The terpenoid composition of seven amber samples from Araripe Basin (Santana Formation, Crato Member) has been analyzed by gas chromatography-mass spectrometry to determine their botanical origin. The diterpenoids, which have been identified in the fossil resin extracts are derived primarily from the abietane class, e.g., dehydroabietane, 4-epidehydroabietol, 16,17,18-trisnorabieta-8,11,13-triene, 7-oxo-16,17,19-trisnorabieta-8,11,13-trieno, dehydroabietic acid, ferruginol, hinokiol and hinokione. Their composition is certainly typical for conifers, and angiosperms can be excluded as the botanical source, as no triterpene was identified. The terpenoid characteristics strongly support a relationship to the Araucariaceae or Podocarpaceae families. In addition, the fossil record of the embedding sediments (pollen and fossil leaves) also supports the proposal of these paleobotanical origins for the ambers.

Asphaltenes from two Brazilian crude oils were submitted to mild oxidation to disrupt their structure, releasing the occluded oil. The released hydrocarbons were compared with those from the original crude oil, and used to evaluate the alteration of the oils, especially as a result of biodegradation, but also thermal maturity. The crude oils used are depleted in n-alkanes, which are usually related to biodegradation. However, the released products from the corresponding asphaltenes have n-alkane distributions from nC10 to nC40, suggesting a protection effect from biodegradation. The m/z 191 mass chromatograms showed higher relative intensities for tricyclic terpanes than the hopanes in the crude in comparison with the released ones.

Traditional biomarker parameters and aromatic compounds were applied to characterize and classify ten Cuban asphaltites (asphaltene-rich petroleum occurring as seeps or filling veins, joints, cavities and fissures). Genetic molecular parameters were compared in order to establish oil-oil correlations between samples. Thermal evolution was investigated using saturated biomarker and aromatic maturity parameters. All samples seem to represent petroleum in the early catagenetic stage. Statistical procedures used as auxiliary techniques show that they represent oils of Family II (marine anoxic carbonate sourced oils), except for 2 samples interpreted as belonging to Family III oils (normal marine siliciclastic suboxic sourced oils).

Hidrocarbonetos policíclicos aromáticos (HPAs) foram identificados e quantificados em amostras de água e sedimento em 12 pontos da Baía de Guanabara. As amostras foram analisadas por CG-EM para verificar o grau de contaminação através do monitoramento do ecossistema afetado após o derramamento de óleo que ocorreu em 18 de janeiro de 2000. As concentrações totais de HPAs encontradas nas amostras de sedimento apresentaram valores na faixa de 77 a 7751 µg kg-1 em peso seco e de não detectado a 1592 ng L-1 em amostras de água. A maioria das amostras de sedimento foi classificada como altamente contaminada (HPA > 500 µg kg-1) enquanto a concentração nas amostras de água não apresentou valores suficientemente alto para causar alguma toxidez aos organismos aquáticos. A concentração de HPAs na Baía de Guanabara, quando comparada com outras regiões costeiras, está relativamente alta. Foi utilizada a razão entre HPAs de baixa massa molar/alta massa molar (BMM/AMM), fenantreno/antraceno e benzo[a]antraceno/criseno como indicadores da origem dos HPAs, os quais demonstraram que a grande parte da contaminação da Baía de Guanabara é derivada da queima de combustíveis.

Polycyclic aromatic hydrocarbons (PAHs) were identified and quantified in sediment and water samples from 12 sites in the north-northeast region of the Guanabara Bay. The samples were analyzed by GC-MS to assess the degree of contamination by monitoring the affected ecosystem after an oil spill that occurred in January 18, 2000. Total PAH concentrations ranged from 77 to 7,751 µg kg-1 dry weight in surficial sediment samples and from not detected to 1592 ng L-1 in water samples. The majority of sediment samples were classified as highly contaminated (total PAH > 500 µg kg-1) while for water samples the concentration of PAHs was not sufficiently high to induce acute toxicity to aquatic organisms. In comparison with other coastal areas, PAH concentrations in Guanabara Bay are relatively high. The ratios of low molecular weight/high molecular weight (LMW/HMW) PAHs, phenanthrene/anthracene and benzo[a]anthracene/chrysene, are sensitive indicators of the origin of PAH pollution, which have shown to be mostly from fuel combustion in the Guanabara Bay.