GC Chromatograms Research Articles

Chemical Composition of the Unconventional Oil Extracted from <em>Zizyphus lotus</em> Almonds

The present study aims to evaluate the chemical composition of fatty acids, sterols, and tocopherols of unconventional vegetable oil extracted by maceration with hexane from the <em>Zizyphus lotus</em> almonds. The fruit of the <em>Zizyphus lotus</em> was collected during the month of September 2016 in the Khouribga region of Morocco. The extraction yield is of the order of 24%. Analysis of GC chromatograms shows that the oil consists of more than 80.5% unsaturated fatty acids or oleic acid (C18: 1, 66.28%) represent the major fatty acid, followed by the acid linoleic (C18: 2, 13.94%). GC analysis of the unsaponifiable fraction reveals the presence of β-sitosterol with a significant percentage of approximately 71.05% and the HPLC chromatogram analysis of tocopherols shows the presence of γ-tocopherol and ?-tocopherol respectively with a rate of 93.93 and 6.07% for a total tocopherol content of 97.3 mg/kg.

Synthesis and Application of Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/SiO&lt;sub&gt;2&lt;/sub&gt;/TiO&lt;sub&gt;2&lt;/sub&gt; Nanocomposite as Photocatalyst in CO&lt;sub&gt;2&lt;/sub&gt; Indirect Reduction to Produce Methanol

This study focuses on the synthesis and application of a Fe3O4/SiO2/TiO2 nanocomposite as a photocatalyst in CO2 indirect reduction. The synthesis was started by preparation of magnetite (Fe3O4) followed by silica (SiO2) coating and titania (TiO2) deposition. Magnetite was prepared by the sono-coprecipitation method, then the coating of SiO2 and deposition of TiO2 were performed by the sol-gel method under ultrasonic irradiation. All the material products were characterized by an X-ray diffractometer (XRD), Fourier-transform infrared spectrophotometer (FTIR), and transmission electron microscope (TEM). The final material product was also analyzed by a specular reflectance UV-Visible spectrometer (SR-UV-Vis) and the turbidimetry method. The product of the indirect reduction was analyzed by a gas chromatography-mass spectrometer (GC-MS). The XRD diffractograms and FTIR spectra confirmed the presence of Fe3O4, SiO2, and the anatase phase of TiO2. The TEM images revealed the presence of a core-shell nanocomposite with an average diameter of 19.22 ± 1.25 nm. The SR-UV-Vis spectrum was used to determine the band gap energy of the photocatalyst, with the result being 3.22 eV. Turbidimetry aimed to measure the magnetic recoverability of the final material, and the result was that it had better recoverability compared to a non-magnetic photocatalyst composite. The GC chromatogram of the indirect reduction product indicated four majorfractions; the MS spectra showed these to be methanol, formaldehyde, formic acid, and CO2. The GC-MS results revealed that CO2 indirect reduction achieved 73.91% conversion of CO2 and 55.01% selective to methanol.

Petroleum extracts of Cynanchum cutum L. and structure elucidation of isolated compounds

In present study, petroleum ether extracts of Cynanchum cutum L. isolated unknown active constituents and their structure elucidated by analytical technique. The extracts were analyzed by the GC/MS technique. The GC chromatogram showed nine peaks corresponding to four compounds. These four compounds were identified on the basis of a high percentage of matching with authentic spectrum using NIST library.

Column selection approach to achieve a high peak capacity in comprehensive three-dimensional gas chromatography

The separation power of comprehensive three-dimensional gas chromatography (GC3) is substantially enhanced through proper selection of the phase volume ratio, β, of each column relative to each other on successive dimensions. Consideration and application of the ratio of phase volume ratios, βr, or β ratio, between successive dimensions has been a relatively un-studied approach to maximize separating power in comprehensive multidimensional GC instrument design. Herein, proper selection of βr in multidimensional GC is shown to control the elution temperature, Te, of analytes throughout a 40 min primary (1D) column separation, and thus better control width-at-base, W, on all three dimensions. Specifically, between the 1D and secondary (2D) columns, a βr of 0.45 was applied, and between the 2D and tertiary (3D) columns a βr of 1.0 was applied. A total ideal peak capacity of 30,600, or a peak capacity production of ~770 peaks/min, was accomplished with the GC3 instrument with the reconfigured parameters. Additionally, due to the complex nature of this three-dimensional data, a novel approach to “slicing” the chromatographic run into user-defined time intervals is shown. This novel way to view the data still elicits a traditional GC×GC chromatograms, but with the focus on 2D × 3D separations. Moreover, due to proper βr selection, every 2 s window (i.e. every 1D modulation period) is shown to have a peak capacity of ~50–100 for each 2D × 3D separation. This high overall peak capacity (30,600) and peak capacity per 1D modulation (~50–100), courtesy of proper column selection, is demonstrated to hold great promise to physically separate truly complex mixtures.

Comparative Analysis of Volatile Constituents of Pachira aquatica Aubl. and Pachira glabra Pasq., their Anti-Mycobacterial and Anti-Helicobacter pylori Activities and their Metabolic Discrimination using Chemometrics

The leaves and stems of the two Pachira species cultivated in Egypt, namely Pachira aquatica, and Pachira glabra were qualitatively and quantitatively examined for their volatile constituents employing GC/FID and GC/MS. Sixty compounds have been identified from P. aquatica leaves and stem representing 87.26 and 90.14%, respectively of their total oil content. However, fifty seven compounds were determined from P. glabra leaves and stems representing 89.67 and 94.69%, respectively. Trans-phytol represented the major component of P. glabra leaf oil with a content of 28.72% of the oil, however β-cadinene (15.46%), was the predominating compound in P. glabra stem oil. Palmitic acid methyl ester (21.08%) and 9,12-octadecadienoic acid ethyl ester (26.20%) were the prevailing constituents in Pachira aquatica leaves and stems oil, respectively. Hierarchical cluster analysis (HCA) and principle component analysis (PCA) as unsupervised chemometric technique were successfully employed to differentiate the two morphologically close related species based upon their GC chromatograms. Only P. aquatica leaf oil showed effectiveness against both Mycobacterium tuberculosis and Helicobacter pylori infection showing MIC values of 50 and 20 μg/mL against them, respectively emphasizing its potent inhibitory activity against both hazardous infections. Thus, volatile constituents from the P. aquatica leaves offer a natural, cheap and relatively safe candidate for pharmaceutical industries to combat these life-threatening bacterial infections.

Monitoring of Biochemical Compounds and Fatty Acid in Marine Microalgae from the East Coast of Thailand

Determinations of fatty acid profiles of five microalgae; Amphora sp., Chaetoceros sp., Melosira sp., Bellerochae sp., and Lithodesmium sp., from the east coast of Thailand were evaluated by conventional Gas Chromatography-Flame Ionization Detector (GC-FID). The results exhibited that the fatty acids suitable for biodiesel production were the most frequent entities encountered in all microalgae profiles. The GC chromatogram of fatty acid profiles in microalgae showed that both Amphora sp. and Chaetoceros sp. comprised essential omega-3 fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Additionally, this study assessed whether Fourier Transform infrared (FT-IR) microspectroscopy could be used to evaluate and monitor the biochemical compositions of microalgae, including lipid, carbohydrate, and protein profiles, by using colorimetric methods. Results showed that FT-IR spectra combined with biochemical values of lipid, carbohydrate, and protein contents were used as predictive models generated by partial least square (PLS) regression. Cross-validation of the lipid, protein, and carbohydrate models showed high degrees of statistical accuracy with RMSECV values of approximately 0.5 - 3.22 %, and a coefficient of regression between the actual and predicted values of lipids, carbohydrates, and proteins were 92.66, 95.73, and 96.43 %, respectively. The RPD values were all high (&gt; 3), indicating good predictive accuracy. This study suggested that FT-IR could be a tool for the simultaneous measurement of microalgae composition of biochemical contents in microalgae cells.

Hydrodechlorination of chlorophenols over Pd catalysts supported on zeolite Y, MCM-41 and graphene

Hydrodechlorination (HDC) reaction of chlorophenols was carried out using Pd catalysts supported over zeolite Y, MCM-41 or graphene. Pd-MCM-41 and Pd-Y zeolite were prepared by impregnation and ion-exchange method, respectively. Pd-graphene (Pd-G) was prepared by hydrazine hydrate reduction of palladium ion dispersed on graphene oxide. The catalysts were characterized by several analytical tools such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). These catalysts were subjected to HDC reaction of chlorophenols, such as 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,6-dichlorophenol (2,6-DCP) and 3,4-dichlorophenol (3,4-DCP). The reaction rate of HDC of chlorophenols catalyzed by Pd catalysts with various solid bases, such as KF/Al2O3 (alumina), sodium acetate (NaOAc) and K2CO3 was compared. First, Pd-MCM-41 and Pd-Y catalysts were compared. 2,4- and 3,4-DCPs were completely decomposed within 6 h, in the case of Pd-MCM-41 with NaOAc. Using Pd-Y instead of Pd-MCM-41 with NaOAc, much faster decomposition was observed. Faster decomposition of 4-CP and DCPs was observed with NaOAc base than K2CO3 or KF/Al2O3 under the same condition. In the case of Pd-Y with KF/Al2O3, slower decomposition of 4-CP and DCPs was observed. These base effects were interpreted using the solubility of NaCl and KCl in alcohol and the basic sites of KF/Al2O3. Because the solubility of NaCl is known to be larger than KCl solubility in alcohol, byproduct NaCl could be easily dissolved and ionized in solvents. For Pd-Y with KF/Al2O3, the small pore size of Y zeolite can interfere with the diffusion of HCl to KF/Al2O3 basic site. Second, three catalysts, including Pd-graphene, were compared. 2,4-DCP was decomposed within 2 h using Pd-G with either K2CO3, NaOAc or KF/Al2O3. Pd-G catalyst showed the highest catalytic activity among Pd-G, Pd-MCM-41 and Pd-Y catalysts. The high activity and stability of the Pd-G could be attributed to the strong metal–support interaction with an electron-deficient site and a critical Pd particle size (ca. 3.5 nm) of Pd-G nanocatalyst with a stronger resistance to the deactivation and good affinity toward aromatic organic molecules, especially phenols. The progress of HDC reaction was monitored by gas chromatography with flame ionization detection (GC/FID), and a feasible degradation process could be explained by analyzing the degradation products such as phenol, cyclohexanone and cyclohexanol from resulting GC chromatograms. The effect of reaction temperature on HDC in Pd-G catalyst was also discussed. In conclusion, Pd-G is an efficient catalyst for decomposition of chlorophenols and can be applied to remediation of chlorophenol-contaminated water under mild conditions.

Characterization of catalytic fast pyrolysis oils: The importance of solvent selection for analytical method development

Two catalytic fast pyrolysis (CFP) oils (bottom/heavy fraction) were analyzed in various solvents that are used in common analytical methods (nuclear magnetic resonance – NMR, gas chromatography – GC, gel permeation chromatography – GPC, thermogravimetric analysis – TGA) for oil characterization and speciation. A more accurate analysis of the CFP oils can be obtained by identification and exploitation of solvent miscibility characteristics. Acetone and tetrahydrofuran can be used to completely solubilize CFP oils for analysis by GC and tetrahydrofuran can be used for traditional organic GPC analysis of the oils. DMSO-d6 can be used to solubilize CFP oils for analysis by 13C NMR. The fractionation of oils into solvents that did not completely solubilize the whole oils showed that miscibility can be related to the oil properties. This allows for solvent selection based on physico-chemical properties of the oils. However, based on semi-quantitative comparisons of the GC chromatograms, the organic solvent fractionation schemes did not speciate the oils based on specific analyte type. On the other hand, chlorinated solvents did fractionate the oils based on analyte size to a certain degree. Unfortunately, like raw pyrolysis oil, the matrix of the CFP oils is complicated and is not amenable to simple liquid–liquid extraction (LLE) or solvent fractionation to separate the oils based on the chemical and/or physical properties of individual components. For reliable analyses, for each analytical method used, it is critical that the bio-oil sample is both completely soluble and also not likely to react with the chosen solvent. The adoption of the standardized solvent selection protocols presented here will allow for greater reproducibility of analysis across different users and facilities.

GC/MS Analysis of Long-Chain Aldehydes from Recent Coral

The main objective of this study is to present the chromatograms and mass spectra of aldehydes so that geochemists could easily identify these compounds in sediment samples. Aldehydes are rare compounds found in the surface environment, particularly in sediments. To date, aldehydes have not been used as environmental proxies. In this study, long-chain aldehydes detected from coral collected from the east coast of Kenya are analyzed by gas chromatography mass spectrometry (GC/MS) using the typical procedure for biomarker analysis. The retention time of the long-chain aldehydes and fatty acid methyl esters slightly overlapped. Hence, the peak corresponding to the aldehyde in the GC chromatogram is buried with that corresponding to the ester, possibly overlooking the aldehyde. After assessing the difference in the retention time between the aldehydes and fatty acids methyl ester, the aldehydes were easily detected using the standard analytical procedure for biomarkers analysis. A molecular ion (M+) with greater than 23 carbon atoms was detected from long-chain aldehydes. The base peak was observed at m/z 82 in the mass spectra of the aldehyde, where characteristic 68 + 14n ions corresponding to even-numbered ions were observed. The M-18 ion, which was formed by the loss of H2O, as well as M-46 or M-84 ions, was characteristic ions observed for long-chain aldehydes of the number of all carbon. The results obtained from this work, in which aldehydes were identified from coral samples, represent a good example of what could be achieved by geochemists when working with sediment samples and using aldehydes as environmental proxies.

Electrokinetic treatment of high saline petrochemical wastewater: Evaluation and scale-up

High total dissolved solids (TDS) wastewater containing high amounts of organics with toxic and recalcitrant characteristics is a major concern in some petrochemical industries. This study was designed to evaluate a novel electrokinetic process for chemical oxygen demand (COD) removal. The removal of COD was carried out in some batch experiments in lab scale and effect of experimental factors such as the pH, current intensity, time, electrodes distances and TDS on the COD removal was evaluated. Also scale-up of the process was done in order to evaluate energy consumption. The obtained findings indicated that best conditions for COD removal were achieved in pH 5, current intensity of 0.5 A and electrodes distance of 2 cm. Pseudo-first-order kinetic model with rate constant of 0.0093 min−1 and significant coefficient of correlation (R2) 0.948 was the best fitted with experimental results. Energy consumption was 32 KWh.m−3 while 80 fold scaling up the reactor resulted in lower energy consumption of 2.1 KWh.m−3.Biodegradability improvement confirmed by BOD5/COD, average oxidation state (AOS) and carbon oxidation state (COS) indicators, Also GC chromatogram of the raw and treated wastewater showed removal and/or degradation of recalcitrant organics to more degradable and simpler compounds.

Comprehensive two-dimensional gas chromatography using partial modulation via a pulsed flow valve with a short modulation period

Partial modulation via a pulsed flow valve for comprehensive two-dimensional (2D) gas chromatography (GC × GC) is demonstrated, producing narrow peak widths, 2Wb, on the secondary separation dimension, 2D, coupled with short modulation periods, PM, thus producing a high peak capacity on the 2D dimension, 2nc. The GC × GC modulator is a pulse flow valve that injects a pulse of carrier gas at the specified PM, at the connection between the primary, 1D, column and the 2D column. Using a commercially available pulse flow valve, this injection technique performs a combination of vacancy chromatography and frontal analysis, whereby each pulse disturbance in the analyte concentration profile as it exits the 1D column results in data that is readily converted into a 2D separation. A three-step process converts the raw data into a format analogous to a GC × GC separation, incorporating signal differentiation, baseline correction and conversion to a GC × GC chromatogram representation. A 115-component test mixture with a wide range of boiling points (36–372°C) of nine compound classes is demonstrated using modulation periods of PM = 50, 100, 250, and 500ms, respectively. For the test mixture with a PM of 250ms, peak shapes on 2D are symmetric with apparent 2Wb ranging from 12 to 45ms producing a 2nc of ~ 10. Based on the average peak width of 0.93s on the 1D separation for a time window of 400s, the 1D peak capacity is 1nc ∼ 430. Thus, the ideal 2D peak capacity nc,2D is 4300 or a peak capacity production of 650 peaks/min using the PM of 250ms. Additionally, for a PM of 50, 100 and 500ms, the 2nc are 4, 7, and 12, respectively. Retention times on 2D, 2tR, are reproducible having standard deviations less than 1ms. Finally, the processed data is shown to be quantitative, with an average RSD of 4.7% for test analytes.

Carboxymethyl Cellulose Photocracking by Magnetic Recoverable Photocatalyst to Produce Biofuel in Ambient Condition

Synthesis of Fe3O4/SiO2/TiO2 nanocomposite and its application as photocatalyst in Carboxymethyl Cellulose (CMC) photocracking had been conducted. Magnetite preparation was carried out by sono-coprecipitation method. The deposition of SiO2 and TiO2 were performed by sol-gel method under ultrasonic irradiation. All material products were characterized by X-ray diffraction (XRD), Fourier transform infra-red spectrophotometry (FT-IR), and transmission electron microscopy (TEM). The final material product was also analysed by specular reflectance UV-Visible (SR-UV-Vis). The product of photocracking was analysed by gas chromatography – mass spectrometry (GC-MS).The XRD diffractogram and FT-IR spectra confirmed the presence of Fe3O4, SiO2, and anatase phase of TiO2. The TEM image revealed the presence of nanocomposite with core-shell structure. The SR-UV-Vis spectrum was used to determine band gap energy of the photocatalyst and it gave a result of 3.22 eV. The GC chromatogram of photocracking product indicated some major fractions. The MS spectra showed that some major fractions were smaller molecules including methanol, the component of biofuel.

Titania nanoparticles embedded in functionalized carbon for the aqueous phase oxidation of 5-hydroxymethylfurfural

Titania nanoparticles have huge potential due to their low cost, easy preparation, separation and high catalytic application. As-synthesized titania nanoparticles embedded at the functionalized acidic carbon act as effective heterogeneous catalyst for the selective oxidation of 5-hydroxylmethylfurfural (HMF) to 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA) in water. It was found that the doping of Ti (IV) with sulfonated carbon improve the catalytic effectiveness of resulting materials. The oxidation reaction and selectivity of the oxidation products, DFF, FDCA and FFCA were monitored by use of oxygen through manometric apparatus and a GC chromatogram. Titania nanoparticles embedded at the functionalized carbon gave higher selectivity for DFF (88% yield) under 1 atmospheric pressure of O2 at 70°C. The catalyst was characterized by the XPS, XRD, FESEM, HRTEM, FTIR and Raman spectroscopic techniques. The characterization data reveal the presence of the acid sites and titania in +4 oxidation state.

Evaluation of membrane filtration for cleanup in multi-residue pesticide analysis of spinach

This study reports a new membrane filtration-based cleanup method for the analysis of pesticides. Recovery and cleanup by membrane filtration using 11 different membranes, classified by their molecular weight cut-off, pore size, and material, were examined. Three different eluent mixtures were also examined. The results indicated that membranes with a 0.1-μm pore size were the most effective among those tested. In particular, hydrophobic polyvinylidene difluoride and hydrophobic polytetrafluoroethylene gave better recoveries and cleanup than other membranes. Results from GC chromatograms and matrix effects showed that membrane filtration afforded better cleanup than the modified QuEChERS method. Furthermore, over 90% of the 89 pesticides tested had acceptable recoveries using these two membranes, according to an acceptable recovery range of 70–120%. Therefore, this technique has potential as an effective cleanup method.

Predicting Partitioning and Diffusion Properties of Nonpolar Chemicals in Biotic Media and Passive Sampler Phases by GC × GC.

The chemical parameters needed to explain and predict bioavailability, biodynamics, and baseline toxicity are not readily available for most nonpolar chemicals detected in the environment. Here, we demonstrate that comprehensive two-dimensional gas chromatography (GC × GC) retention times can be used to predict 26 relevant properties for nonpolar chemicals, specifically: partition coefficients for diverse biotic media and passive sampler phases; aquatic baseline toxicity; and relevant diffusion coefficients. The considered biotic and passive sampler phases include membrane and storage lipids, serum and muscle proteins, carbohydrates, algae, mussels, polydimethylsiloxane, polyethylene, polyoxymethylene, polyacrylate, polyurethane, and semipermeable membrane devices. GC × GC-based chemical property predictions are validated with a compilation of 1038 experimental property data collected from the literature. As an example application, we overlay a map of baseline toxicity to fathead minnows onto the separated analyte signal of a polychlorinated alkanes (chlorinated paraffins) technical mixture that contains 7820 congeners. In a second application, GC × GC-estimated properties are used to parametrize multiphase partitioning models for mammalian tissues and organs. In a third example, we estimate chemical depuration kinetics for mussels. Finally, we illustrate an approach to screen the GC × GC chromatogram for nonpolar chemicals of potentially high concern, defined based on their GC × GC-estimated biopartitioning properties, diffusion properties, and baseline toxicity.

The quantification of short-chain chlorinated paraffins in sediment samples using comprehensive two-dimensional gas chromatography with μECD detection.

The analysis of persistent organic pollutants in environmental samples is a challenge due to the very large number of compounds with varying chemical and physical properties. Chlorinated paraffins (CPs) are complex mixtures of chlorinated n-alkanes with varying chain lengths (C10 to C30) and degree of chlorination (30 to 70% by weight). Their physical-chemical properties make these compounds persistent in the environment and able to bioaccumulate in living organisms. Comprehensive two-dimensional gas chromatography (GC × GC) coupled with micro-electron capture detection (μECD) was used to separate and quantify short-chain chlorinated paraffins (SCCP) in sediment samples. Distinct ordered bands were observed in the GC × GC chromatograms pointing to group separation. Using the Classification function of the ChromaTOF software, summary tables were generated to determine total area counts to set up multilevel-calibration curves for different technical mixes. Fortified sediment samples were analyzed by GC × GC-μECD with minimal extraction and cleanup. Recoveries ranged from 120 to 130%. To further validate the proposed method for the analysis of SCCPs, the laboratory participated in interlaboratory studies for the analysis of standards and sediment samples. The results showed recoveries between 75 and 95% and z-score values <2, demonstrating that the method is suitable for the analysis of SCCPs in soil/sediment samples. Graphical abstract Quantification of SCCPs by 2D-GC-μECD.

Toxicity of Two Fixed Plant Oils by Using a New Fumigant Method Against Trogoderma granarium Everts and Stegopium paniceum (L.)

The present research was achieved to study the toxicity of fixed oils of clove buds (Syzygium aromaticum) and spearmint leaves( Mentha spicata) against larvae and adults of Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae) and the adults of the drugstore beetle, Stegobium paniceum (L.) byusing a new fumigant technique. Germination test was conducted in order to assess the effect of tested oils at the highest concentration on wheat seeds after 24 hrs. A GC/MS analysis was performed to record the main chemical constituents in tested oils. Analysis of the toxicity data showed that, clove fixed oil exhibited the strongest fumigant toxicity against all tested insects. T.granarium larvae showed a very high resistance against both oils comparing with adults. Germination test showed no adverse effect of the tested oils on wheat seeds germination comparing with control. The GC chromatogram of clove buds fixed oil showed that, the main constituents were eugenol (37.43%) eugenol acetate (11.47%), caryophellene (10.44 %), linoleic acid (9.42%) and caryophellene oxide (8.58%). The GC-MS chromatogram of spearmint fixed oil showed that, the main constituents were carvone (33.9%) and limonene (2.7%).

Two-dimensional gas chromatography-online hydrogenation for improved characterization of petrochemical samples

The Fischer-Tropsch (FT) process produces a variety of hydrocarbons over a wide carbon number range and during subsequent product workup a large variety of synthetic fuels and chemicals are produced. The complexity of the product slate obtained from this process is well documented and the high temperature FT (HT-FT) process products are spread over gas, oil and water phases. The characterization of these phases is very challenging even when using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS). Despite the increase in separation power, peak co-elution still occurs when samples containing isomeric compounds are analysed by comprehensive two dimensional GC. The separation of isomeric compounds with the same double bond equivalents is especially difficult since these compounds elute in a similar position on the GC×GC chromatogram and have identical molecular masses and similar fragmentation patterns in their electron ionization (EI) mass spectra. On-line hydrogenation after GC×GC separation is a possible way to distinguish between these isomeric compounds since the number of rings and alkene double bonds can be determined from the mass spectra of the compounds before and after hydrogenation. This paper describes development of a GC×GC method with post column hydrogenation for the determination of the backbone of cyclic/olefinic structures enabling us to differentiate between classes like dienes and cyclic olefins in complex petrochemical streams.

A Vacuum Ultraviolet Absorption Array Spectrometer as a Selective Detector for Comprehensive Two-Dimensional Gas Chromatography: Concept and First Results.

Fast and selective detectors are very interesting for comprehensive two-dimensional gas chromatography (GC × GC). This is particularly true if the detector system can provide additional spectroscopic information on the compound structure and/or functionality. Other than mass spectrometry (MS), only optical spectroscopic detectors are able to provide selective spectral information. However, until present the application of optical spectroscopy technologies as universal detectors for GC × GC has been restricted mainly due to physical limitations such as insufficient acquisition speed or high detection limits. A recently developed simultaneous-detection spectrometer working in the vacuum ultraviolet (VUV) region of 125-240 nm overcomes these limitations and meets all the criteria of a universal detector for GC × GC. Peak shape and chromatographic resolution is preserved and unique spectral information, complementary to mass spectrometry data, is gained. The power of this detector is quickly recognized as it has the ability to discriminate between isomeric compounds or difficult to separate structurally related isobaric species; thus, it provides additional selectivity. A further promising feature of this detector is the data analysis concept of spectral filtering, which is accomplished by targeting special electronic transitions that allows for a fast screening of GC × GC chromatograms for designated compound classes.

Microspora Floccosa: A Potential Biofuel Producer

The current study is focused on biofuel production from local specie of algae. Initially samples were observed to identify the algal specie. Afterward oil was extracted from algae by Soxhlet extraction method, retention time was optimized to improve the yield of oil at different intervals. The recovered oil from algae was subjected to qualitative analysis by Gas Chromatography. Four major peaks were appeared on GC chromatogram which correspond to methyl esters of dodecanoic acid, tetradecanoic acid, 8,11,14-Eicosadienoic acid and 9,10-dihydroxy octadecanoic. The results reflect that Microspora floccosa algae considered to be favorable for biofuel production.