Identification and classification of components in flash pyrolysis oil and hydrodeoxygenated oils by two-dimensional gas chromatography and time-of-flight mass spectrometry

Hydrodeoxygenated pyrolysis oils (HDO) are considered promising renewable liquid energy carriers. To gain insights in the various reaction pathways taking place during the hydrodeoxygenation reaction of pyrolysis oil, two-dimensional gas chromatography with time-of-flight mass spectrometric analyses (2D-GC-TOF-MS) was applied on the feedstock and product oil. Chromatographic parameters like injection temperature and column choice of the 1D-(2)D ensemble are discussed. Fractionation of the oils by hexane extraction was applied to show the distribution of analytes over the phases. Some 1000 and 2000 components in the pyrolysis and HDO oil, respectively could be identified and classified. The TOF-MS detection considerably improved the understanding of the molecular distribution over the 1D-(2)D retention time fields in the contour plot, in order to classify the analytes in functional groups. By group-type classification of the main components (>0.3% relative area), it was possible to characterize the oils by 250 and 350 analytes, respectively pyrolysis oil and HDO oil, describing 75% of the chromatographable fraction. The 2D-GC-TOF-MS method showed to be a useful and fast technique to determine the composition of (upgraded) pyrolysis oil and is potentially a very useful tool for exploratory catalyst research and kinetic studies. The 2D-GC-TOF-MS technique is not only useful for the chemical study as such, but also provides the basic knowledge for method transfer to a 2D-GC-FID (flame ionization detector) application.     

Possibilities and pitfalls in analyzing (upgraded) pyrolysis oil by size exclusion chromatography (SEC)

The applicability of size exclusion chromatography (SEC) to analyze (upgraded) pyrolysis oil samples has been studied using model compounds, pyrolysis oils and hydrodeoxygenated pyrolysis oils. The assumptions needed for the conversion of the chromatogram to the M_w-distribution were validated. It was shown that the conversion of elution volume to molecular weight (based on polystyrene calibration curves) can introduce substantial errors in the prediction of the molecular weight. The conversion of RID response to W(log M) (as plotted on the y-axis of the M_w-distribution) is based on the assumption of a compound independent RID response factor and linear response to concentration. While the latter was shown to be true within the concentration range studied, the former was not true: the RID response factor depends on the type of (upgraded) pyrolysis oil. It was shown that within a single pyrolysis oil sample, the RID response for the low molecular weight fraction was a factor 3 lower than the high molecular weight fraction. Furthermore long term column fouling can influence SEC results that cannot be corrected with regular polystyrene recalibrations.Based on the results we recommend SEC not to be used as a quantitative method for characterization (upgraded) pyrolysis oil samples, but as a tool to compare (upgraded) pyrolysis oil samples, preferably prepared using incremental operating conditions and expected to have similar molecular composition. This work has further shown that (i) the ∫UVDdv/∫RIDdv ratio can be used as an indication of the sum of the relative aromaticity and conjugated double bond content for (upgraded) pyrolysis oil, and (ii) the negative peak area appearing in the low molecular weight part of the chromatogram can be used to estimate the water content of (upgraded) oil samples.     

Chemical composition and antimicrobial activity of some oleogum resin essential oils from Boswellia spp. (Burseraceae)

The chemical composition of Boswellia carteri (Somalia), B. papyrifera (Ethiopia), B. serrata (India) and B. rivae (Ethiopia) oleogum resin essential oils was investigated using GC-MS to identify chemotaxonomy marker components. Total ion current peak areas gave good approximations to relative concentrations based on GC-MS peak areas. B. carteri and B. serrata oleogum resin oils showed similar chemical profiles, with isoincensole and isoincensole acetate as the main diterpenic components. Both n-octanol and n-octyl acetate, along with the diterpenic components incensole and incensole acetate, were the characteristic compounds of B. papyrifera oleogum resin oil. Hydrocarbon and oxygenated monoterpenes were the most abundant classes of compounds identified in the B. rivae oleogum resin oil. The antimicrobial activities of the essential oils were individually evaluated against different microorganisms including fungi, Gram-positive and Gram-negative bacteria strains. The essential oils with the best activity against fungal strains were those obtained from B. carteri and B. papyrifera with MIC values as low as 6.20 microg/ml. The essential oil of B. rivae resin showed the best activity against C. albicans with a MIC value of 2.65 microg/ml.     

MCM-41/SBA-15中孔分子筛对生物质热解油的催化裂解研究

以中孔MCM 41/SBA 15分子筛作催化剂，对不同条件下快速热解得到的木屑热解蒸气进行催化裂解，采用元素分析、凝胶色谱(s.e.c.)和气质联用（GC MS）等手段表征。结果表明,同未加催化剂比较，分子筛MCM 41/SBA 15的存在可使热解液体中氧的质量分数降低，长链化合物所占比例明显减小，其中SBA 15作催化剂比MCM 41作催化剂对热解蒸气裂解更容易得到接近柴油和汽油分子量的热解油，但芳香类化合物的质量分数明显增加。热解油中Pentadecane、Hexadecane、Dimethyjbenzene、Naphthalene等质量分数增加，而含氧类物质Methyl Phenol、2 Methoxy 4 Methyl Phenol、2 Methoxy 4 Propyl Phenol 等质量分数减少。     

Evaluation of gas chromatography-mass spectrometry in conjunction with chemometric resolution for identification of nitrogen compounds in crude oil

A chemometric resolution method is described for the identification of nitrogen compounds in crude oil. Prefractionation of crude oil into discrete chemical classes was performed by adsorption column chromatography using small quantities of neutral aluminum oxide and silicic acid. Subsequent high-resolution separation of individual components was achieved by using capillary column gas chromatography, and compound types were detected by mass spectrometer. In conjunction with a combined chemometric method, each principal chemical class was further resolved and separated, which made it possible to identify some nitrogen compounds in the investigated oils. To a certain extent, this method could relieve classical analysis of difficulty in identifying those species with poorly low contents or partially chromatographic overlaps, particularly in the cases where authentic standards were not available for addition into the unknown analytical systems to reveal what indeed existed in them.     

GC-MS分析大蒜中的挥发油和大蒜精油

采用气相色谱—质谱法,分析比较大蒜中的挥发油以及大蒜精油的化学成分,通过非负矩阵因子分解(NMF)方法解析色谱重叠峰,并用峰面积百分比法计算各化学成分的峰面积相对百分含量。确定了大蒜中37种化学成分,其中含硫化合物34种,大蒜精油中的32种化学成分,含硫化合物28种。     

Classification of weathered petroleum oils by multi-way analysis of gas chromatography-mass spectrometry data using PARAFAC2 parallel factor analysis

The application of multi-way parallel factor analysis (PARAFAC2) is described for the classification of different kinds of petroleum oils using GC-MS. Oils were subjected to controlled weathering for 2, 7 and 15 days and PARAFAC2 was applied to the three-way GC-MS data set (MSxGCxsample). The classification patterns visualized in scores plots and it was shown that fitting multi-way PARAFAC2 model to the natural three-way structure of GC-MS data can lead to the successful classification of weathered oils. The shift of chromatographic peaks was tackled using the specific structure of the PARAFAC2 model. A new preprocessing of spectra followed by a novel use of analysis of variance (ANOVA)-least significant difference (LSD) variable selection method were proposed as a supervised pattern recognition tool to improve classification among the highly similar diesel oils. This lead to the identification of diagnostic compounds in the studied diesel oil samples.     

Pyrolysis of asphaltenes and biomarkers for the fingerprinting of the Amoco-Cadiz oil spill after 23 years

The geochemical technique of asphaltenes pyrolysis was successfully applied to the long-term monitoring of the Amoco-Cadiz oil spill 23 years after the wreck in the salt marshes of Île Grande, Northern Brittany, France. This method allows the reconstitution of the saturated fraction of the original oil from the asphaltenes fraction of severely degraded oil residues. The results showed that the oil reached a degradation rate of 60% relatively to the initial oil. The asphaltenes pyrolysis generated a gas chromatographic profile very similar to the original Amoco-Cadiz oil. In the biomarkers fraction, gas chromatographic/mass spectrometric (GC-MS) analyses demonstrated that terpanes were conserved whereas steranes were partly degraded. We also showed that the class of seco-hopanes biomarkers are conserved and can be used in the long-term monitoring of oil pollutions.     

Characterization of slow pyrolysis oil obtained from linseed (Linum usitatissimum L.)

This study presents the characterization of pyrolysis oil obtained from linseed (Linum usitatissimum L.) produced by slow pyrolysis in the maximum yield. The pyrolysis oil was analyzed to determine its elemental composition and calorific value. The chemical composition of the pyrolysis oil and fractions were investigated using chromatographic and spectroscopic techniques (¹H NMR, IR, and GC). The chemical class composition of the oil was determined by liquid column chromatographic fractionation. The oil was separated into pentane soluble and insoluble fractions by using pentane. The column was eluted successively with n-pentane, toluene and methanol to yield aliphatic, aromatic and polar fractions, respectively. The results of the adsorption chromatography of the oil showed that the pyrolysis oil consists of 88 wt% n-pentane soluble. The aliphatic, aromatic and polar fractions of oils obtained in slow pyrolysis are 30, 34, 36 wt%, respectively. The aliphatic and aromatic subtraction make up ∼64 wt% in slow pyrolysis oil. This seems to be more appropriate for the production of hydrocarbons and chemicals.     

Investigation of sulphur compounds in coal tar using monodimensional and comprehensive two-dimensional gas chromatography

Coal is a non renewable fossil fuel, used mainly as a source of electrical energy and in the production of coke. It is subjected to thermal treatment, pyrolysis, which produces coke as a main product, in addition to a condensed liquid by-product, called tar. Tar is a complex mixture of organic compounds which contains different chemical classes, presenting aromatic and sulphur heterocyclic compounds. In general, identification of these compounds requires steps of isolation and fractionation, mainly due to co-elution of these compounds with polyaromatic hydrocarbons (PAH). The objective of this work is to characterize the sulphur compounds present in the coal tar obtained via pyrolysis, using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detector (GC×GC/TOFMS). Coal samples from the State of Paraná, Brazil were subjected to laboratorial scale pyrolysis. Several experimental conditions were tested, such as sample weight (5, 10 and 15g), heating ramp (10, 25 and 100°C/min) and final temperature (500, 700 and 900°C). Samples were analyzed by one dimensional gas chromatography (1D-GC) coupled to a quadrupole mass spectrometry detector (GC/qMS) and two-dimensional gas chromatography with time-of-flight mass spectrometry detector (GC×GC/TOFMS). The higher amount of sulphur compounds was obtained at a final temperature of 700°C and a heating ramp of 100°C/min. The main classes observed in the color plot were thiophenes, benzothiophenes and alkylated dibenzothiophenes. GC×GC/TOFMS allowed the identification of the greater number of compounds and the separation of several sulphur compounds from one another. Moreover, separation of sulphur compounds from polyaromatic hydrocarbons and phenols was achieved, which was not possible by 1D-GC. Comparing GC×GC/TOFMS and 1D-GC (SIM mode) also showed that 1D-GC, one of the most employed quantification tools for sulphur compounds, can be misleading for detection, identification and quantification, as the number of isomers of sulphur compounds found was greater than theoretically possible.     

Pyrolysis of waste tire on ZSM-5 zeolite with enhanced catalytic activities

Catalytic copyrolysis of waste tires over ZSM-5 zeolite with lubricant base oil (LBO) was undertaken at 430 °C under nitrogen atmosphere in a batch mode, and the pyrolysis oils were characterized using gas chromatography/mass spectroscopy (GC-MS). By combining with LBO, the ZSM-5 catalyzed pyrolysis system of tires has a sharply enhanced degradation rate. Compared to the pyrolysis without LBO, the liquid yield is increased from 33.6% to 48.0%, while the gas and the residue yields are decreased. In the pyrolysis oils, the content of heavy components is decreased and the content of light oils (n-C ≤ 12) is increased from 77.8%(without LBO) to 83.1%(with LBO); especially, the content of C₁₀ components has a sharp increase. Moreover, the liquid compositions are changed. Particularly, the percentage of limonene increased dramatically from 7.54% for thermal degradation to 13.58%. These results suggest that the enhanced catalytic effects on pyrolysis of tires in the catalytic systems are due to the improved interactions between tires and catalysts with the help of LBO. Therefore, it is possible to improve the process economics of scrap tires by catalytic copyrolysis with LBO, which can not only increase the pyrolysis rate remarkably but also produce high-value oil products.     

Temperature-programmed retention indices for gas chromatography-mass spectroscopy analysis of plant essential oils

A total of 95 volatile compounds from the essential oil in buds of Syringa oblata Lindl (lilac) were identified by gas chromatography-mass spectrometry (GC-MS) combined with heuristic evolving latent projections (HELP) and moving subwindow searching (MSS). The identified compounds are mainly aliphatic, terpenes and aromatic compounds. Their temperature-programmed retention indices (PTRIs) on HP-5MS and DB-35MS at three heating rates of 2, 4 and 6 degrees C/min from 80 to 290 degrees C were obtained, which showed that aliphatic compounds give nearly constant PTRIs and PTRIs of terpenoids do not vary much at different heating rates. But PTRIs of aromatic compounds exhibit relatively large temperature dependence. PTRIs vary much more on DB-35MS than those on HP-5MS according to the compound types. In general, differences of PTRIs between the two columns increase from aliphatic compounds to terpenoids to polycyclic aromatic compounds. The PTRIs in different heating rates were used as cross-references in the identification of components in the essential oil. When they were used in analysis of essential oil from flowers of lilac, good results were obtained. These PTRIs would be a part of our PTRI database being constructed on components from plant essential oils. The results also showed that efficiency and reliability were improved greatly when chemometric method and PTRIs were used as assistants of GC-MS in identification of chemical components in plant essential oils.     

In Vitro Anti-Inflammatory Activity of Cotula anthemoides Essential Oil and In Silico Molecular Docking of Its Bioactives

The genus Cotula (Asteraceae) comprises about 80 species, amongst them Cotula anthemoides L. It is a wild plant growing in Egypt that possesses many traditional uses as a headache, colic, and chest cold remedy. In our study, the chemical composition of C. anthemoides essential oils was analyzed using GC-MS spectroscopy. Sixteen components of leave and stem oils and thirteen components of flower oils were characterized. The main components in both essential oil parts were camphor (88.79% and 86.45%) and trans-thujone (5.14% and 10.40%) in the leaves and stems and the flowers, respectively. The anti-inflammatory activity of the oils in lipopolysaccharide-stimulated RAW 264.7 macrophage cells was evaluated. The flower oil showed its predominant effect in the amelioration of proinflammatory cytokines and tumor necrosis factor-α, as well as cyclooxygenase-2. The bornyl acetate showed the highest affinity for the cyclooxygenase-2 receptor, while compound cis-p-menth-2-ene-1-ol had the best affinity for the tumor necrosis factor receptor, according to the results of molecular docking. In addition, the molecule cis-β-farnesene showed promising dual affinity for both studied receptors. Our findings show that essential oils from C. anthemoides have anti-inflammatory properties through their control over the generation of inflammatory mediators. These findings suggest that C. anthemoides essential oils could lead to the discovery of novel sources of anti-inflammatory treatments.     

Comparing the weathering patterns of six oils using 3-way generalized Procrustes rotation and matrix-augmentation principal components

A case study is presented in which advanced chemical fingerprinting and data interpretation techniques are used to characterize and compare the weathering processes of six oil spillages made under controlled conditions (including the heavy oil released after the Prestige tanker sunk off the Galician coast-NW Spain on 2002). A tiered analytical approach using gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS) was applied along with two different approaches for 3-way analyses; namely, generalized Procrustes rotation, and matrix-augmented principal components analysis. Results showed that the two 3-way chemometric techniques leaded to essentially the same conclusions when analyzing three sets of compounds fingerprinting the spilled hydrocarbons (aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs) and a set of diagnostic ratios). A steady evolution on the weathering of the oils was observed with both techniques, but for the diagnostic ratios. The variables involved on the weathering were the lightest aliphatic hydrocarbons and a general combination of the PAHs, which differentiated mostly among the light and the heavy products (fuel oils).     

SPME/GC-MS鉴别地沟油新方法(Ⅲ)

该文通过气相色谱-质谱法研究调味品的化学成分,进而对地沟油进行鉴别,发现乙酸来源于醋、3-丁烯腈来源于腌菜酱汁、异硫氰酸烯丙酯来源于芥末、糠醛来源于酱油、茴香脑来源于八角茴香、姜烯来源于生姜和老姜。通过检测油脂样品中是否含有这些调味品的特征成分,即可鉴别是否餐厨废弃油。该文采用顶空固相微萃取(SPME)富集微量外源杂质成分,并研制专用的气相色谱柱,用气相色谱-质谱联用法(GC-MS)测定乙酸、3-丁烯腈、糠醛、异硫氰酸烯丙酯、茴香脑、姜烯6种成分,样品中若含有这些微量成分中的一种或多种,则判定为餐厨废弃油。     

Analysis of gin essential oil mixtures by multidimensional and one-dimensional gas chromatography/mass spectrometry with spectral deconvolution

The composition of essential oils and their mixtures used to formulate gin is usually too complex to separate all sample components by standard capillary gas chromatography (GC). In particular, minor constituents that possess important organoleptic properties can be masked by co-elution with major sample components. A solution is provided that combines gas chromatography/mass spectrometry (GC/MS) with "interactive" spectral deconvolution software. Sequential two-dimensional (2D) GC/MS is used to produce a target compound library, with orthogonal GC-GC providing the separation power required to obtain peak retention times and the corresponding mass spectra needed for the deconvolution database. The combination of these two techniques, mass spectral deconvolution and automated sequential 2D-GC/MS, offers a very effective synergy for both identifying key constituents that determine the perception of flavor and aroma and the quality control needed to analyze mixtures of complex essential oils.     

Fast gas chromatography characterisation of purified semiochemicals from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae)

The chemical composition of Matricaria chamomilla L. and Nepeta cataria L. essential oils was determined by GC-MS on an apolar stationary phase by comparison of the characteristic fragmentation patterns with those of the Wiley 275L database. The GC-MS chromatograms were compared with those obtained by fast GC equipped with a direct resistively heated column (Ultra Fast Module 5% phenyl, 5 mx 0.1 mm, 0.1 microm film thickness). Analytical conditions were optimised to reach a good peak resolution (split ratio=1:100), with analysis time lower than 5 min versus 35-45 min required by conventional GC-MS. The fast chromatographic method was completely validated for the analysis of mono- and sesquiterpene compounds. Essential oils were then fractionated by column chromatography packed with silica gel. Three main fractions with high degree of purity in E-beta-farnesene were isolated from the oil of M. chamomilla. One fraction enriched in (Z,E)-nepetalactone and one enriched in beta-caryophyllene were obtained from the oil of N. cataria. These semiochemical compounds could act as attractants of aphid's predators and parasitoids.     

Qualitative and quantitative analysis of pyrolysis oil by gas chromatography with flame ionization detection and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry

Pyrolysis oils have attracted a lot of interest, as they are liquid energy carriers and general sources of chemicals. In this work, gas chromatography with flame ionization detector (GC-FID) and two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) techniques were used to provide both qualitative and quantitative results of the analysis of three different pyrolysis oils. The chromatographic methods and parameters were optimized and solvent choice and separation restrictions are discussed. Pyrolysis oil samples were diluted in suitable organic solvent and were analyzed by GC×GC-TOFMS. An average of 300 compounds were detected and identified in all three samples using the ChromaToF (Leco) software. The deconvoluted spectra were compared with the NIST software library for correct matching. Group type classification was performed by use of the ChromaToF software. The quantification of 11 selected compounds was performed by means of a multiple-point external calibration curve. Afterwards, the pyrolysis oils were extracted with water, and the aqueous phase was analyzed both by GC-FID and, after proper change of solvent, by GC×GC-TOFMS. As previously, the selected compounds were quantified by both techniques, by means of multiple point external calibration curves. The parameters of the calibration curves were calculated by weighted linear regression analysis. The limit of detection, limit of quantitation and linearity range for each standard compound with each method are presented. The potency of GC×GC-TOFMS for an efficient mapping of the pyrolysis oil is undisputable, and the possibility of using it for quantification as well has been demonstrated. On the other hand, the GC-FID analysis provides reliable results that allow for a rapid screening of the pyrolysis oil. To the best of our knowledge, very few papers have been reported with quantification attempts on pyrolysis oil samples using GC×GC-TOFMS most of which make use of the internal standard method. This work provides the ground for further analysis of pyrolysis oils of diverse sources for a rational design of both their production and utilization process.     

柽柳实中挥发油和脂肪酸分析

首次研究了维药细穗柽柳(Tamarix leptostachys Bunge)实中挥发油和脂肪酸的化学成分。 分别采用药典中的挥发油提取法和索式取提法提取柽柳实中的挥发油和脂肪酸,使用气质联用技术获取总离子流图,各色谱峰相应的质谱图经过NIST2011标准谱库检索定性,并采用峰面积归一化法进行定量分析,计算各成分的相对百分含量。 两种方法分别鉴定出48种挥发油和19种脂肪酸。 挥发油主要成分为芳香类化合物(43.71%)、芳香性醛酮类(20.58%)、脂肪酸类(13.03%)、酯类(17.36%)和醇类(4.19%)等。 脂肪酸主要成分为棕榈酸(35.61%)、亚油酸(27.26%)和油酸(11.33%)等,其中不饱和脂肪酸含量占总脂肪酸含量的38.65%。 维药细穗柽柳实中富含丰富的挥发油和不饱和脂肪酸,具有很好的开发利用价值。     

Composition and antimicrobial activity of the leaf and twig oils of Litsea acutivena from Taiwan

The chemical composition, and antimicrobial and anti-wood-decay fungal activities of the essential oils isolated from the leaves and twigs of Litsea acutivena of Taiwan were investigated. The essential oils from the fresh leaves and twigs were isolated using hydrodistillation in a Clevenger-type apparatus, and characterized by GC-FID and GC-MS. Ninety-five and fifty-two compounds were identified in the leaf and twig oils, respectively. The main components of the leaf oil were gamma-patchoulene (11.0%), delta-cadinene (6.3%), trans-muurola-3,5-diene (5.9%), and beta-selinene (5.3%), whereas the main components of the twig oil were tau-cadinol (13.1%), beta-selinene (9.6%), trans-beta-ocimene (6.2%) and alpha-cadinol (7.7%). Bioactivity studies demonstrated that twig oil had excellent antimicrobial and anti-wood-decay fungal activities, superior to those of the leaf oil. For the antimicrobial and anti-wood-decay fungal activities of the twig oil, the active compounds were determined to be tau-cadinol and alpha-cadinol.