Gas Chromatograms Research Articles

Chemical composition and larvicidal activity of edible plant-derived essential oils against the pyrethroid-susceptible and -resistant strains of Aedes aegypti (Diptera: Culicidae)

Chemical composition and larvicidal activity of edible plant-derived essential oils against the pyrethroid-susceptible and -resistant strains of Aedes aegypti (Diptera: Culicidae)

Sedimentation, organic maturity, and petroleum potential of the Oligocene–Miocene oil shale deposits, Yayu Basin, southwestern Ethiopia

Studies initiated in the search for domestic energy supplies for Ethiopia have confirmed the presence of oil shales in the Yayu Basin. This article presents some of the characteristics of these shales. The basin is located in the southwest of Ethiopia and consists of Precambrian basement and Cenozoic volcanic and sedimentary rocks. Three sedimentary successions reach a cumulative maximum thickness of 165 m (541 ft). Two oil shale horizons have been identified in the upper and lower sedimentary successions and reach a maximum thickness of 35 and 20 m (115 and 65 ft), respectively. Sedimentation in the basin occurred in fluvial and lacustrine depositional environments. The sandstone facies was deposited in a fluvial environment, whereas the oil-shale-bearing sediments were deposited in a lacustrine environment. Algal amorphous materials and minor amounts of woody materials characterize the studied oil shales with Botryococcus and Pediastrum, indicating a lacustrine environment. The studied oil shales are characterized by high total organic carbon values up to 61.2% and S2 (hydrocarbon-generating potential) values ranging from 10.78 to 119.07 HC g/kg, indicating excellent source rocks. Most of the oil shales are at the immature to early mature stage for hydrocarbon generation. Vitrinite reflectance measurements on the oil shale samples are less reliable because of the presence of abundant algal materials. Gas chromatogram results also indicate source rocks. The Yayu Basin is estimated to have up to 1 billion metric tons of oil shale reserves.

Toward Metabolomic Signatures of Cardiovascular Disease

Small biochemicals are the end result of all the regulatory complexity present in a cell, tissue, or organism, including transcriptional regulation, translational regulation, and posttranslational modifications. Metabolic changes are thus the most proximal reporters of the body’s response to a disease process or drug therapy. In 1971, Robinson and coworkers1 conceived the core idea that information-rich data reflecting the functional status of a complex biological system resides in the quantitative and qualitative pattern of metabolites in body fluids. In the same year, Horning and Horning2 first used the term metabolic profiling to describe the output of a gas chromatogram from a patient sample. This new approach to the quantitative metabolic profiling of large numbers of small molecules in biofluids was ultimately termed “metabonomics” by Nicholson et al3 and “metabolomics” by others. Article see p 207 Two core technologies are used to perform metabolic profiling: nuclear magnetic resonance and tandem mass spectrometry (MS/MS), as previously reviewed in Circulation: Cardiovascular Genetics. 4 Nuclear magnetic resonance requires relatively little sample preparation and is nondestructive, allowing for subsequent structural analyses. However, the method tends to have low sensitivity and can detect only highly abundant analytes. Tandem mass spectrometry (MS/MS), coupled with liquid chromatography, on the other hand, has much higher sensitivity for small molecules and is also applicable to a wide range of biological fluids (including serum, plasma, and urine). Recent advances in MS technology now enable researchers to determine analyte masses with such high precision and accuracy that metabolites can be identified unambiguously even in complex fluids. These technologies can be used to characterize biological samples either in a targeted manner or in a pattern discovery manner. In the former, the investigator targets a predefined …

The Malcom distribution analysis method: A consistent guideline for assessing reservoir compartmentalisation from GC fingerprinting

Characterisation of reservoirs, as well as studies of reservoir continuity, can be achieved using various techniques. Among these, reservoir oil fingerprinting obtained from analysis of gas chromatograms of crude oils is one of the less expensive and less time consuming methods. However, the technique has some limitations, as uncertainties relating to peak height ratios, classically used as a starting point in current methods, are not well quantified. This paper presents a new statistical method, based on a consistent quantification of the uncertainty from the peak height measurements, which provides absolute distances between fingerprints on a universal scale. It allows the creation of a database of case studies directly usable for comparison purposes in any new project: the knowledge acquired from former studies can be readily employed to set the threshold of composition variability at which barriers/baffles should be invoked. The method is able to discriminate samples even if the amplitude of the compositional differences is about the same as the error in the peak heights, and distances between samples depend neither on the number of peak ratios available, nor on the uncertainty in the peak height measurements.

An assessment of paleodepositional environment and maturity of organic matter in sediments of the Setap Shale and Belait formations in West Sabah, East Malaysia by organic geochemical methods

The black shale samples collected from two Neogene formations in the Klias Peninsula area, West Sabah, have been assessed and characterized in details by gas chromatography, gas chromatography-mass spectrometry and a variety of organic geochemical parameters. The aims of this study are to describe the characteristics of organic matter of these sediments in terms of source/type of the organic matter, assess its thermal maturity and paleoenvironment of deposition, based primarily on biomarker distributions. The results of both formations do not reveal significant differences within the rock extracts. The gas chromatograms of the saturated hydrocarbon fractions of the Setap Shale and the Belait formations displayed monomodal n-alkane distributions and nearly identical regular sterane compositions with a predominance of C27 regular steranes. These are consistent with open marine depositional environments dominated by marine biological matter. Another related feature of these rock extracts is the presence of a high relative abundance of gammacerane, indicating anoxic marine hypersaline source depositional environment. The relatively high abundance of common land plant-derived biomarkers, such as bicadinanes and oleananes, is a clear indication of a major terrigenous input to the source of the extractable organic matter. The predominance of oleanane biomarkers in both formations is indicative of angiospermis input and Tertiary source rocks. The high C29/C30 hopane ratios, moderate development of C33–C35 hopanes, high abundance of tricyclic terpanes and a slight predominance of C27 regular sterane over C28 and C29 steranes are characteristic features tending to suggest a significant marine influence on these source rocks, thereby suggesting a mixed source input. The 22S/(22S+22R)C32 hopane ratio has reached equilibrium, and this is supported by the high maturity level as indicated by the 22S/22SC31–33 extended hopane ratios and 20S/(20S+20R)C29 regular steranes ratios.

Wastewater Containing 1,2-Dihydro-2,2,4-Trimethylquinoleyn Treated by Electrolysis and Respirometric Method

The electrolytic treatment of a real industrial effluent and simulated wastewater containing the 1,2-dihydro- 2,2,4-trimethylquinoleyn compound (Naugard Q®) had been investigated in order to improve the wastewater biodegradability. The electrolysis was carried out in a batch electrolytic cell using 70TiO2/30RuO2 electrodes (DSA® anode). After electrochemical treatment, wastewaters were evaluated in terms of Naugard Q® concentration, UV-visible spectrophotometry and biodegradation. Further analyses were conducted in simulated wastewater by gas chromatography and the biodegradation process was monitored using respirometric flasks. Both real effluent and simulated wastewater presented a decrease in Naugard Q® concentration. The simulated wastewater electrolytic treatment provided concentration reduction of Naugard Q® about 52.04% after 60 min, whereas real effluent concentration was reduced by 62.60% after 40 minutes. Furthermore, UV-visible spectra and gas chromatograms presented significant alterations in molecular structure of the compound. After 30 min electrolysis, an increase in simulated wastewater biodegradation was observed. In real effluent, the biodegradation response was faster, as more CO2 was produced in assays that underwent 10 and 25 minutes of electrolytic treatment. This result is probably related to modifications in Naugard Q® molecular structure. It was concluded that the electrolytic treatment followed by bioremediation could be an alternate treatment to degrade this compound.

A Feasibility Study for Assessment of <i>In-situ</i> Bioremediation Potential of a Crude Oil Degrading <i>Pseudomonas</i> Consortium

A microcosm study evaluating inoculums addition of mixed bacterial consortium to stimulate in-situ bioremediation of crude oil contaminated soil was conducted. In feasibility study, out of five treatments the application of bacterial consortium, nutrients and environmental factors resulted in 79.16% removal of TPH in 60 days, compared to 30.24% removal of TPH carried out by indigenous microflora. Gas chromatograms of original spilled oil and bioremediated oil by the addition of developed consortium shows that Pr/Ph ratio decreased progressively from 2.358 to 1.626. The results showed that the ratio of di/tri aromatics decreased from initial 0.63 to 0.25 with progressive treatment of nutrient addition, as nutrient + tilling, nutrient + tilling + microbial seeding. Similar effect was observed in di/di + tri aromatics ratios which also decreased 0.31 to 0.20 by bioaugmentation only. Keywords: Hydrocarbons; Pseudomonas; Biodegradation; Gas Chromatogram. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i1.2601 J. Sci. Res. 2 (1), 127-137 (2010)

Nonlinear preprocessing method for detecting peaks from gas chromatograms

BackgroundThe problem of locating valid peaks from data corrupted by noise frequently arises while analyzing experimental data. In various biological and chemical data analysis tasks, peak detection thus constitutes a critical preprocessing step that greatly affects downstream analysis and eventual quality of experiments. Many existing techniques require the users to adjust parameters by trial and error, which is error-prone, time-consuming and often leads to incorrect analysis results. Worse, conventional approaches tend to report an excessive number of false alarms by finding fictitious peaks generated by mere noise.ResultsWe have designed a novel peak detection method that can significantly reduce parameter sensitivity, yet providing excellent peak detection performance and negligible false alarm rates from gas chromatographic data. The key feature of our new algorithm is the successive use of peak enhancement algorithms that are deliberately designed for a gradual improvement of peak detection quality. We tested our approach with real gas chromatograms as well as intentionally contaminated spectra that contain Gaussian or speckle-type noise.ConclusionOur results demonstrate that the proposed method can achieve near perfect peak detection performance while maintaining very small false alarm probabilities in case of gas chromatograms. Given the fact that biological signals appear in the form of peaks in various experimental data and that the propose method can easily be extended to such data, our approach will be a useful and robust tool that can help researchers highlight valid signals in their noisy measurements.

A novel polymer-grafted C 60 fullerene having both hydrophilic and hydrophobic chains

A novel polymer-grafted C 60 fullerene having both hydrophilic poly(ethylene oxide) (PEO) and hydrophobic polystyrene (polySt) chains, was successfully synthesized by postpolymerization of St initiated by PEO-grafted C 60 fullerene, bis-adduct C 60-(PEO) 2, having peroxyester (POE) groups. C 60-(PEO) 2 was prepared by the reaction of C 60 fullerene with PEO-azopolymer. The introduction of POE groups onto C 60-(PEO) 2 was achieved by trapping of POE radicals formed by the thermal decomposition of 1,1-bis( t-butyldioxy)cyclohexane (BDOC). The structure of C 60-(PEO) 2(POE) was confirmed by FT-IR, UV–vis, and DSC. The postgraft radical polymerization of St was successfully initiated by the POE groups of C 60-(PEO) 2(POE) to give polySt-grafted C 60-(PEO) 2. The structure of polySt-grafted C 60-(PEO) 2 was identified by FT-IR, SEC, and thermal decomposition gas chromatograms and mass spectra (GC–MS). The polySt-grafted C 60-(PEO) 2 was soluble in good solvents for polySt and PEO, but insoluble in n-hexane which is poor solvent for polySt and PEO, and partially soluble in water which is good solvent for PEO but poor solvent for polySt. The compatibility of polySt-grafted C 60-(PEO) 2 in polySt matrix was remarkably improved in comparison with that of C 60-(PEO) 2. In addition, thermal stability of polySt-grafted C 60-(PEO) 2 increased in comparison with that of polySt and PEO.

Samaria-doped Ceria Modified Ni/YSZ Anode for Direct Methane Fuel in Tubular Solid Oxide Fuel Cells by Impregnation Method

A porous NiO/yttria-stabilized zirconia anode substrate for tubular solid oxide fuel cells was prepared by gel casting technique. Nano-scale samaria-doped ceria (SDC) particles were formed onto the anode substrate to modify the anode microstructure by the impregnation of solution of Sm(NO3)3 and Ce(NO3)3. Electrochemical impedance spectroscopy, current-voltage and current-powder curves of the cells were measured using an electrochemical workstation. Scanning electron microcopy was used to observe the microstructure. The results indicate that the stability of the performance of the cell operated on humidified methane can be significantly improved by incorporating the nano-structured SDC particles, compared with the unmodified cell. This verifies that the coated SDC electrodes are very effective in suppressing catalytic carbon formation by blocking methane from approaching the Ni, which is catalytically active towards methane pyrolysis. In addition, it was found that a small amount of deposited carbon is beneficial to the performance of the anode. The cell showed a peak power density of 225 mW/cm2 when it was fed with H2 fuel at 700 C, but the power density increased to 400 mW/cm2 when the fuel was switched from hydrogen to methane at the same flow rate. Methane conversion achieved about 90%, measured by gas chromatogram with a 10.0 mL/min flow rate of fuel at 700 C. Although the carbon deposition was not suppressed absolutely, some deposited carbon was beneficial for performance improvement.

An accurate and non-labor intensive method for the determination of syringyl to guaiacyl ratio in lignin

The syringyl to guaiacyl (S:G) ratio of hardwood lignin has long been identified as a significant parameter in delignification processes and more recent results have shown that it is also important in determining the amount of ethanol that can be obtained from fermentation of hydrolyzed wood. Acidolysis of Klason or acid insoluble lignin in dioxane/water/HCl was being investigated when syringyl and guaiacyl nuclei with a diketone-containing sidechain were observed as the major products. The area ratio of the two gas chromatogram peaks appeared to be indicative of the S:G ratio. After optimization of the method the relative standard deviation was found to be in the range of 0.3–3.76% for Klason lignin from a wide range of Eucalyptus grandis grown in South Africa. The method was then compared to nitrobenzene oxidation (NBO) using 13 poplars in a double-blind study. The respective S:G ratios were used to calculate percentages of S units and when these values were plotted against each other a linear correlation was obtained with a slope of approximately 1.0 ( R 2 = 0.86). The largest discrepancy for any poplar was 6.9% (62% vs. 58% S units). Both methods convincingly demonstrated a significant decrease in lignin content with an increase in the S:G ratio. Discussion is presented on a series of reaction that could lead to the formation of the two diketones.

Two-dimensional wavelet analysis based classification of gas chromatogram differential mobility spectrometry signals

This study introduces two-dimensional (2-D) wavelet analysis to the classification of gas chromatogram differential mobility spectrometry (GC/DMS) data which are composed of retention time, compensation voltage, and corresponding intensities. One reported method to process such large data sets is to convert 2-D signals to 1-D signals by summing intensities either across retention time or compensation voltage, but it can lose important signal information in one data dimension. A 2-D wavelet analysis approach keeps the 2-D structure of original signals, while significantly reducing data size. We applied this feature extraction method to 2-D GC/DMS signals measured from control and disordered fruit and then employed two typical classification algorithms to testify the effects of the resultant features on chemical pattern recognition. Yielding a 93.3% accuracy of separating data from control and disordered fruit samples, 2-D wavelet analysis not only proves its feasibility to extract feature from original 2-D signals but also shows its superiority over the conventional feature extraction methods including converting 2-D to 1-D and selecting distinguishable pixels from training set. Furthermore, this process does not require coupling with specific pattern recognition methods, which may help ensure wide applications of this method to 2-D spectrometry data.

Direct Conversion of Glycerol into 1,3-Propanediol over Cu-H4SiW12O40/SiO2 in Vapor Phase

Using a SiO2 supported copper and H4SiW12O40 catalyst, it is demonstrated that glycerol can be directly converted to 1,3-Propanediol (1,3-PD) through vapor-phase process under pressure below 0.54 MPa, without employing environmentally harmful organic solvent. The formation of 1,3-PD is proved to proceed through the designed reaction pathway: (step 1) dehydration of glycerol to 3-hydroxypropanal on acid site of supported H4SiW12O40 (step 2) hydrogenation of 3-hydroxypropanal on supported copper metal. The effect of temperature, weight hourly space velocity, pressure, and initial water content was investigated to obtain the optimum conditions. The glycerol conversion and products distribution greatly depended on these factors. Both the 1,3-PD and 1,2-Propanediol selectivity improved with increasing hydrogen pressure. At 210 °C, 0.54 MPa and 83.4% conversion, the selectivity of 1,3-PD was up to 32.1%, together with a 22.2% selectivity of 1,2-Propanediol. The cyclic acetal, an important kind of byproducts, was identified by Gas Chromatogram–Mass Spectrometer (GC–MS).

Selection of biochemical characters in the breeding for pest and disease resistance: A method based on analogy analysis of chromatographic separation patterns for emitted plant substances

Chromatographic separation patterns of emitted substances are proposed to be used as fingerprints of the defence chemistry in plants. The goal is to recognize the patterns of resistance agents in the chromatograms and to use these patterns for guidance in resistance breeding. This can be done by comparing a reference set of resistant plants with a reference set of nonresistant plants. One problem is the great number of data. A capillary gas chromatogram from a wounded leaf, e.g., may contain more than a hundred component peaks. Such multidimensional comparisons can only be made by a computer. The literature has been searched for computer programs suited for this purpose. The Statistical Isolinear Multiple Component Analysis method (SIMCA) is found to be best suited. It is theoretically estimated that the processing of chromatographic data by the SIMCA-method can enable the resistance breeder to classify unknown plants as resistant or nonresistant; to discern nonrelevant peaks in the chromatograms; to grade the importance of the resistance variables; and to predict the optimal levels for the different resistance agents. The results indicate that capillary gas chromatography and high pressure liquid chromatography can be adapted to handle the great number of samples needed in a breeding program. These methods together cover the molecular range of importance for resistance.

Effect of the fuel system icing inhibitor diethylene glycol monomethyl ether on the biodegradation of jet fuel in soil

Microbial degradation of jet fuel leads to the accumulation of sludge in fuel distribution systems and storage tanks. To prevent this phenomenon, the biocidal anti-icing inhibitor diethylene glycol monomethyl ether (DiEGME) is routinely added to the fuel. The fate of DiEGME in soil and its consequent effect on the biodegradation of jet fuel by indigenous soil microflora have not been investigated. The aim of this work was to study the kinetics of biodegradation of jet fuel in dark rendzina soil, as affected by the presence of DiEGME. Our data show that the degradability in soil of jet fuel amended with DiEGME was tenfold higher than that of non-amended fuel. Consequently, there was an increase in the jet-fuel-utilizing soil microbial populations during the 100 days of incubation of soil samples amended with jet fuel containing DiEGME. Gas chromatograms of distilled fractions of jet fuel extracted from the soil demonstrated that most of the light fractions' extracts could not be detected at the end of the 100-day incubation. The relative concentration of aromatic compounds in the soil contaminated with DiEGME-amended jet fuel increased during incubation, demonstrating the lower biodegradation rate of these components compared with other fuel components. DiEGME was partially degraded by the general microbial population of the soil. Maximal DiEGME degradation was obtained with specific jet-fuel-utilizing microbial strains – Pseudomonas aeruginosa and Cladosporium resinae – that were added to a carbon-free mineral medium. The degradation rate of DiEGME by specific strains or by soil mixed populations bore an inverse relationship to the DiEGME concentration. The finding that DiEGME can be degraded by indigenous soil microorganisms may have facilitated its utilization also by jet-fuel-degrading microorganisms.

Identification of brood pheromone in Chinese honeybee [Apis cerana cerana (Hymenoptera: Apidae)

【Objective】 To analyze the brood kairmone and pheromone of different stage brood in Apis cerena cerena and compare it with Apis mellifera. 【Method】 Worker larvae (2-day old, 6-day old and 7-day old) and drone larvae (2-day old, 7-day old and 8-day old) of Apis cerena cerena were extracted with hexane by crushing, the supernatant were then fractioned by chromatography on a column of silica gel and tested by gas chromatogram. 【Result】 It is the first time to identify the components of brood kairmone and pheromone from Apis cerena cerena are methyl palmitate, methyl oleate, methyl stearate, methyl linoleate, methyl linolenate, ethyl palmitate, ethyl oleate, ethyl stearate, ethyl linoleate and ethyl linolenate. 【Conclusion】 The kairmone and 10 aliphatic esters in brood have been found in both Apis mellifera and Apis cerana cerana, while the content and distribution of the two pheromone are different at different brood stages.

Preparation of Antibacterial Polymer-Grafted Silica Nanoparticle and Surface Properties of Composites Filled with the Silica (2)

Antibacterial polymer was grafted onto silica nanoparticle and the surface properties of various composites filled with the silica were investigated. The grafting of antibacterial polymer, poly(vinylbenzyltributylphosphonium chloride) (poly(St-CH2P+(Bu) 3Cl−)), onto silica surface was achieved by two methods: one is treatment of poly(vinylbenzylchloride) (poly(St-CH2Cl))-grafted silica with tributylphosphine and the other is direct grafting of poly(St-CH2P+ (Bu)3Cl−) by radical graft polymerization of the corresponding monomer. The grafting of poly(St-CH2Cl) and poly(St-CH2P+ (Bu)3Cl−) onto silica surface were initiated by the system consisting of trichloroacetyl groups on the silica surface and Mo(CO) 6. Trichloroacetyl groups were introduced onto the silica surface by the reaction of amino groups on the silica surface with trichloroacetyl isocyanate. The percentage of poly(St-CH2Cl) grafting during the graft polymerization initiated by the system increased with progress of the polymerization reached 116%. The grafting of poly(St-CH2P+ (Bu)3Cl−) onto silica surfaces was confirmed by FT-IR spectra, thermal decomposition gas chromatograms and mass spectra (GC-MS), and 13C-CP/MAS NMR. The surfaces of silicone rubber, polystyrene film, and paints filled with the poly(St-CH2P+ (Bu)3Cl−)-grafted silica shows strong antibacterial activity. These composites retained the antibacterial activity even after the boiling in water for 24 h.

Quantitative assessment of gas washing of oils in the Tazhong area of the Tarim Basin, Northwest China

Gas washing has been known in the Tazhong area of the Tarim Basin, but its quantitative assessment has not yet been reported. Here the influence of gas washing fractionation in the area was discussed based on the gas chromatogram data of 68 oils and the results of the mixing experiments of a black oil and a condensate. The results show that the intensity of gas washing fractionation decreased generally from northern to southern part and vertically from deep reservoirs to shallow reservoirs. The gas washing fractionation was mainly controlled by fault systems in this area, with the increase of n-alkane mass depletion positively correlated to the number and scale of faults. Gas washing fractionation appears to have affected the hydrocarbon property, and as a result the diversity of the crude oils is markedly controlled by gas washing. In addition, the occurrence of waxy oil in this area may be resulted from multiple factors including gas washing, mixed filling and migration fractionation.

Accumulation of Intracellular Polyhydroxybutyrate in Alcaligenes sp. d2 Under Phenol Stress

Alcaligenes sp. d(2) isolated from soil was earlier reported as a potent phenol-degrading organism. In the Fourier transform/infrared spectroscopic analysis of the biodegraded sample, the aromatic stretching was missing and the spectrum gave evidence for the presence of polyhydroxybutyric acid along with its depolymerized products. In the gas chromatogram of the biodegraded sample, the peak of phenol at 14.997 min was absent and there were many peaks after 20 min. The organism could carry out 100% degradation of phenol in 32 h and could progressively result in early accumulation of polyhydroxybutyrate (PHB) intracellularly from 8 h onwards. The various conditions optimized for the maximum accumulation of intracellular PHB were pH 7.0, incubation time 24 h, phenol concentration 15 mg/100 ml, and ammonium sulfate concentration 25 mg/100 ml.

Laboratory methods for evaluating migrated high molecular weight hydrocarbons in marine sediments at naturally occurring oil seeps

A laboratory study has been conducted to determine the best methods for the detection of C 10–C 40 hydrocarbons at naturally occurring oil seeps in marine sediments. The results indicate that a commercially available method using n-C 6 to extract sediments and gas chromatography–flame ionization detection (GC–FID) to screen the resulting extract is effective at recognizing the presence of migrated hydrocarbons at concentrations from 50 to 5000 ppm. When non-biodegraded, the amount of oil charge is effectively tracked by the sum of n-alkanes in the gas chromatogram. However, once the charge oil becomes biodegraded, with the loss of n-alkanes and isoprenoids, the amount of oil is tracked by the quantification of the unresolved complex mixture (UCM). Gas chromatography–mass spectrometry (GC–MS) was also found to be very effective for the recognition of petroleum related hydrocarbons and results indicate that GC–MS would be a very effective tool for screening samples at concentrations below 50 ppm oil charge.