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Sample records for 2d gas chromatography

  1. Gas Chromatography.

    ERIC Educational Resources Information Center

    Karasek, Francis W.; And Others

    1984-01-01

    This review covers fundamental developments in gas chromatography during 1982 and 1983. Literature is considered under these headings: columns; liguid phases; solid supports; sorption processes and solvents; open tubular column gas chromatography; instrumentation; high-resolution columns and applications; other techniques; qualitative and…

  2. Gas Chromatography.

    ERIC Educational Resources Information Center

    Cram, Stuart P.; And Others

    1980-01-01

    Selects fundamental developments in theory, methodology, and instrumentation in gas chromatography (GC). A special section reviews GC in the People's Republic of China. Over 1,000 references are cited. (CS)

  3. Gas chromatography.

    PubMed

    Eiceman, G A; Hill, H H; Gardea-Torresdey, J

    1998-06-15

    This review of the fundamental developments in gas chromatography (GC) includes articles published from 1996 and 1997 and an occasional citation prior to 1996. The literature was reviewed principally using CA Selects for Gas Chromatography from Chemical Abstracts Service, and some significant articles from late 1997 may be missing from the review. In addition, the online SciSearch Database (Institute for Scientific Information) capability was used to abstract review articles or books. As with the prior recent reviews, emphasis has been given to the identification and discussion of selected developments, rather than a presentation of a comprehensive literature search, now available widely through computer-based resources. During the last two years, several themes emerged from a review of the literature. Multidimensional gas chromatography has undergone transformation encompassing a broad range of activity, including attempts to establish methods using chromatographic principles rather than a totally empirical approach. Another trend noted was a comparatively large effort in chromatographic theory through modeling efforts; these presumably became resurgent with inexpensive and powerful computing tools. Finally, an impressive level of activity was noted through the themes highlighted in this review, and this was particularly true with detectors and field instruments.

  4. Gas Chromatography

    NASA Astrophysics Data System (ADS)

    Qian, Michael C.

    Gas chromatography (GC) has many applications in the analysis of food products. GC has been used for the determination of fatty acids, triglycerides, cholesterol, gases, water, alcohols, pesticides, flavor compounds, and many more. While GC has been used for other food components such as sugars, oligosaccharides, amino acids, peptides, and vitamins, these substances are more suited to analysis by high performance liquid chromatography. GC is ideally suited to the analysis of volatile substances that are thermally stable. Substances such as pesticides and flavor compounds that meet these criteria can be isolated from a food and directly injected into the GC. For compounds that are thermally unstable, too low in volatility, or yield poor chromatographic separation due to polarity, a derivatization step must be done before GC analysis. The two parts of the experiment described here include the analysis of alcohols that requires no derivatization step, and the analysis of fatty acids which requires derivatization. The experiments specify the use of capillary columns, but the first experiment includes conditions for a packed column.

  5. Qualitative Characterization of the Aqueous Fraction from Hydrothermal Liquefaction of Algae Using 2D Gas Chromatography with Time-of-flight Mass Spectrometry.

    PubMed

    Maddi, Balakrishna; Panisko, Ellen; Albrecht, Karl; Howe, Daniel

    2016-03-06

    Two-dimensional gas chromatography coupled with time-of-flight mass spectrometry is a powerful tool for identifying and quantifying chemical components in complex mixtures. It is often used to analyze gasoline, jet fuel, diesel, bio-diesel and the organic fraction of bio-crude/bio-oil. In most of those analyses, the first dimension of separation is non-polar, followed by a polar separation. The aqueous fractions of bio-crude and other aqueous samples from biofuels production have been examined with similar column combinations. However, sample preparation techniques such as derivatization, solvent extraction, and solid-phase extraction were necessary prior to analysis. In this study, aqueous fractions obtained from the hydrothermal liquefaction of algae were characterized by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry without prior sample preparation techniques using a polar separation in the first dimension followed by a non-polar separation in the second. Two-dimensional plots from this analysis were compared with those obtained from the more traditional column configuration. Results from qualitative characterization of the aqueous fractions of algal bio-crude are discussed in detail. The advantages of using a polar separation followed by a non-polar separation for characterization of organics in aqueous samples by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry are highlighted.

  6. Qualitative Characterization of the Aqueous Fraction from Hydrothermal Liquefaction of Algae Using 2D Gas Chromatography with Time-of-flight Mass Spectrometry

    SciTech Connect

    Maddi, Balakrishna; Panisko, Ellen; Albrecht, Karl; Howe, Daniel

    2016-01-01

    Two-dimensional gas chromatography coupled with time of flight mass spectrometry is a powerful tool for identifying and quantifying components in complex mixtures. It has been used to analyze gasoline, jet fuel, diesel, bio-diesel and organic fraction of bio-crude/bio-oil. In these experiments, the first dimension of separation was non-polar, followed by a polar separation. Aqueous fractions of bio-crude and other aqueous samples have been examined with similar column combinations. However, sample preparation techniques such as derivatization, solvent extraction, and solid-phase extraction were necessary prior to analysis. In this study, aqueous fraction obtained from hydrothermal liquefaction of algae was characterized by two-dimensional gas chromatography coupled with time of flight mass spectrometry without prior sample preparation techniques using a polar separation in the first dimension followed by a non-polar separation. Two-dimensional plots from this analysis were compared with those obtained from the more traditional column combination. Results from qualitative characterization aqueous fractions of algal bio-crude are discussed in detail. The advantages of using a polar separation followed by a non-polar separation for characterization of organics in aqueous samples by two-dimensional gas chromatography coupled with time of flight mass spectrometry are highlighted.

  7. Evaluation of Comprehensive 2-D Gas Chromatography-Time-Of-Flight Mass Spectrometry for 209 Chlorinated Biphenyl Congeners in Two Chromatographic Runs

    EPA Science Inventory

    This research evaluates a recently developed comprehensive 2-D GC coupled with a time-of-flight (TOF) mass spectrometer for the potential separation of 209 PCB congeners, using a sequence of 1-D and 2-D chromatographic modes. In two consecutive chromatographic runs, using a 40 m,...

  8. Gas chromatography in space

    NASA Technical Reports Server (NTRS)

    Akapo, S. O.; Dimandja, J. M.; Kojiro, D. R.; Valentin, J. R.; Carle, G. C.

    1999-01-01

    Gas chromatography has proven to be a very useful analytical technique for in situ analysis of extraterrestrial environments as demonstrated by its successful operation on spacecraft missions to Mars and Venus. The technique is also one of the six scientific instruments aboard the Huygens probe to explore Titan's atmosphere and surface. A review of gas chromatography in previous space missions and some recent developments in the current environment of fiscal constraints and payload size limitations are presented.

  9. Determination of phosphine and other fumigants in air samples by thermal desorption and 2D heart-cutting gas chromatography with synchronous SIM/Scan mass spectrometry and flame photometric detection.

    PubMed

    Fahrenholtz, Svea; Hühnerfuss, Heinrich; Baur, Xaver; Budnik, Lygia Therese

    2010-12-24

    Fumigants and volatile industrial chemicals are particularly hazardous to health when a freight container is fumigated or the contaminated material is introduced into its enclosed environment. Phosphine is now increasingly used as a fumigant, after bromomethane--the former fumigant of choice--has been banned by the Montreal Protocol. We have enhanced our previously established thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) method by integrating a second gas chromatographic dimension and a flame photometric detector to allow the simultaneous detection of phosphine and volatile organic compounds (VOCs), providing a novel application. A thermal desorption system is coupled to a two dimensional gas chromatograph using both mass spectrometric and flame photometric detection (TD-2D-GC-MS/FPD). Additionally, the collection of mass spectrometric SIM and Scan data has been synchronised, so only a single analysis is now sufficient for qualitative scanning of the whole sample and for sensitive quantification. Though detection limits for the herewith described method are slightly higher than in the previous method, they are in the low μL m(-3) range, which is not only below the respective occupational exposure and intervention limits but also allows the detection of residual contamination after ventilation. The method was developed for the separation and identification of 44 volatile substances. For 12 of these compounds (bromomethane, iodomethane, dichloromethane, 1,2-dichlorethane, benzene, tetrachloromethane, 1,2-dichloropropane, toluene, trichloronitromethane, ethyl benzene, phosphine, carbon disulfide) the method was validated as we chose the target compounds due to their relevance in freight container handling.

  10. Energy level transitions of gas in a 2D nanopore

    SciTech Connect

    Grinyaev, Yurii V.; Chertova, Nadezhda V.; Psakhie, Sergei G.

    2015-10-27

    An analytical study of gas behavior in a 2D nanopore was performed. It is shown that the temperature dependence of gas energy can be stepwise due to transitions from one size-quantized subband to another. Taking into account quantum size effects results in energy level transitions governed by the nanopore size, temperature and gas density. This effect leads to an abrupt change of gas heat capacity in the nanopore at the above varying system parameters.

  11. Multiplex gas chromatography

    NASA Technical Reports Server (NTRS)

    Valentin, Jose R.

    1990-01-01

    The principles of the multiplex gas chromatography (GC) technique, which is a possible candidate for chemical analysis of planetary atmospheres, are discussed. Particular attention is given to the chemical modulators developed by present investigators for multiplex GC, namely, the thermal-desorption, thermal-decomposition, and catalytic modulators, as well as to mechanical modulators. The basic technique of multiplex GC using chemical modulators and a mechanical modulator is demonstrated. It is shown that, with the chemical modulators, only one gas stream consisting of the carrier in combination with the components is being analyzed, resulting in a simplified instrument that requires relatively few consumables. The mechanical modulator demonstrated a direct application of multiplex GC for the analysis of gases in atmosphere of Titan at very low pressures.

  12. Quantum Oscillations in an Interfacial 2D Electron Gas.

    SciTech Connect

    Zhang, Bingop; Lu, Ping; Liu, Henan; Lin, Jiao; Ye, Zhenyu; Jaime, Marcelo; Balakirev, Fedor F.; Yuan, Huiqiu; Wu, Huizhen; Pan, Wei; Zhang, Yong

    2016-01-01

    Recently, it has been predicted that topological crystalline insulators (TCIs) may exist in SnTe and Pb1-xSnxTe thin films [1]. To date, most studies on TCIs were carried out either in bulk crystals or thin films, and no research activity has been explored in heterostructures. We present here the results on electronic transport properties of the 2D electron gas (2DEG) realized at the interfaces of PbTe/ CdTe (111) heterostructures. Evidence of topological state in this interfacial 2DEG was observed.

  13. Thermal modulation for gas chromatography

    NASA Technical Reports Server (NTRS)

    Hasselbrink, Ernest F. (Inventor); Libardoni, Mark (Inventor); Stewart, Kristine (Inventor); Waite, J. Hunter (Inventor); Block, Bruce P. (Inventor); Sacks, Richard D. (Inventor)

    2007-01-01

    A thermal modulator device for gas chromatography and associated methods. The thermal modulator device includes a cooling member, an electrically conductive capillary in direct thermal contact with the cooling member, and a power supply electrically coupled to the capillary and operable for controlled resistive heating of the capillary.

  14. Thermal modulation for gas chromatography

    NASA Technical Reports Server (NTRS)

    Hasselbrink, Ernest F. (Inventor); Libardoni, Mark (Inventor); Stewart, Kristine (Inventor); Waite, J. Hunter (Inventor); Block, Bruce P. (Inventor); Sacks, Richard D. (Inventor)

    2007-01-01

    A thermal modulator device for gas chromatography and associated methods. The thermal modulator device includes a recirculating fluid cooling member, an electrically conductive capillary in direct thermal contact with the cooling member, and a power supply electrically coupled to the capillary and operable for controlled resistive heating of the capillary. The capillary can include more than one separate thermally modulated sections.

  15. Automated gas chromatography

    DOEpatents

    Mowry, Curtis D.; Blair, Dianna S.; Rodacy, Philip J.; Reber, Stephen D.

    1999-01-01

    An apparatus and process for the continuous, near real-time monitoring of low-level concentrations of organic compounds in a liquid, and, more particularly, a water stream. A small liquid volume of flow from a liquid process stream containing organic compounds is diverted by an automated process to a heated vaporization capillary where the liquid volume is vaporized to a gas that flows to an automated gas chromatograph separation column to chromatographically separate the organic compounds. Organic compounds are detected and the information transmitted to a control system for use in process control. Concentrations of organic compounds less than one part per million are detected in less than one minute.

  16. Automated gas chromatography

    DOEpatents

    Mowry, C.D.; Blair, D.S.; Rodacy, P.J.; Reber, S.D.

    1999-07-13

    An apparatus and process for the continuous, near real-time monitoring of low-level concentrations of organic compounds in a liquid, and, more particularly, a water stream. A small liquid volume of flow from a liquid process stream containing organic compounds is diverted by an automated process to a heated vaporization capillary where the liquid volume is vaporized to a gas that flows to an automated gas chromatograph separation column to chromatographically separate the organic compounds. Organic compounds are detected and the information transmitted to a control system for use in process control. Concentrations of organic compounds less than one part per million are detected in less than one minute. 7 figs.

  17. Discovery of regulatory molecular events and biomarkers using 2D capillary chromatography and mass spectrometry.

    PubMed

    Powell, David W; Merchant, Michael L; Link, Andrew J

    2006-02-01

    An important component of proteomic research is the high-throughput discovery of novel proteins and protein-protein interactions that control molecular events that contribute to critical cellular functions and human disease. The interactions of proteins are essential for cellular functions. Identifying perturbation of normal cellular protein interactions is vital for understanding the disease process and intervening to control the disease. A second area of proteomics research is the discovery of proteins that will serve as biomarkers for the early detection, diagnosis and drug treatment response for specific diseases. These studies have been referred to as clinical proteomics. To discover biomarkers, proteomics research employs the quantitative comparison of peptide and protein expression in body fluids and tissues from diseased individuals (case) versus normal individuals (control). Methods that couple 2D capillary liquid chromatography (LC) and tandem mass spectrometry (MS/MS) analysis have greatly facilitated this discovery science. Coupling 2D-LC/MS/MS analysis with automated genome-assisted spectra interpretation allows a direct, high-throughput and high-sensitivity identification of thousands of individual proteins from complex biological samples. The systematic comparison of experimental conditions and controls allows protein function or disease states to be modeled. This review discusses the different purification and quantification strategies that have been developed and used in combination with 2D-LC/MS/MS and computational analysis to examine regulatory protein networks and clinical samples.

  18. Multielement detector for gas chromatography

    SciTech Connect

    Sklarew, D.S.; Evans, J.C.; Olsen, K.B.

    1988-11-01

    This report describes the results of a study to improve the capabilities of a gas chromatography-microwave-induced plasma (GC- MIP) detector system, determine the feasibility of empirical formula determination for simple mixtures containing elements of interest to fossil fuel analysis and, subsequently, explore applications for analysis of the complex mixtures associated with fossil fuels. The results of this study indicate that the GC-MIP system is useful as a specific-element detector that provides excellent elemental specificity for a number of elements of interest to the analysis of fossil fuels. It has reasonably good sensitivity for carbon, hydrogen, sulfur, and nickel, and better sensitivity for chlorine and fluorine. Sensitivity is poor for nitrogen and oxygen, however, probably because of undetected leaks or erosion of the plasma tube. The GC-MIP can also provide stoichiometric information about components of simple mixtures. If this powerful technique is to be available for complex mixtures, it will be necessary to greatly simplify the chromatograms by chemical fractionation. 38 refs., 46 figs., 16 tabs.

  19. The 2-D Ion Chromatography Development and Application: Determination of Sulfate in Formation Water at Pre-Salt Region

    NASA Astrophysics Data System (ADS)

    Tonietto, G. B.; Godoy, J. M.; Almeida, A. C.; Mendes, D.; Soluri, D.; Leite, R. S.; Chalom, M. Y.

    2015-12-01

    Formation water is the naturally-occurring water which is contained within the geological formation itself. The quantity and quality of the formation water can both be problematic. Over time, the water volume should decrease as the gas volumes increase. Formation water has been found to contain high levels of Cl, As, Fe, Ba, Mn, PAHs and may even contain naturally occurring radioactive materials. Chlorides in some cases have been found to be in excess of four-five times the level of concentrations found in the ocean. Within the management of well operation, there is sulfate between the analytes of greatest importance due to the potential for hydrogen sulphide formation and consequent corrosion of pipelines. As the concentration of sulfate in these waters can be less than n times that of chloride, a quantitative determination, using the technique of ion chromatography, constitutes an analytical challenge. This work aimed to develop and validate a method for the determination of sulphate ions in hyper-saline waters coming from the oil wells of the pre-salt, using 2D IC. In 2D IC the first column can be understood as a separating column, in which the species with retention times outside a preset range are discarded, while those belonging to this range are retained in a pre-concentrator column to further injecting a second column, the second dimension in which occurs the separation and quantification of the analytes of interest. As the chloride ions have a retention time lower than that of sulfate, a method was developed a for determining sulfate in very low range (mg L-1) by 2D IC, applicable to hypersaline waters, wherein the first dimension is used to the elimination of the matrix, ie, chloride ions, and the second dimension utilized in determining sulfate. For sulphate in a concentration range from 1.00 mg L-1 was obtained an accuracy of 1.0%. The accuracy of the method was tested by the standard addition method different samples of formation water in the pre

  20. Gas amplified ionization detector for gas chromatography

    DOEpatents

    Huston, Gregg C.

    1992-01-01

    A gas-amplified ionization detector for gas chromatrography which possesses increased sensitivity and a very fast response time. Solutes eluding from a gas chromatographic column are ionized by UV photoionization of matter eluting therefrom. The detector is capable of generating easily measured voltage signals by gas amplification/multiplication of electron products resulting from the UV photoionization of at least a portion of each solute passing through the detector.

  1. Ionization-based detectors for gas chromatography.

    PubMed

    Poole, Colin F

    2015-11-20

    The gas phase ionization detectors are the most widely used detectors for gas chromatography. The column and makeup gases commonly used in gas chromatography are near perfect insulators. This facilitates the detection of a minute number of charge carriers facilitating the use of ionization mechanisms of low efficiency while providing high sensitivity. The main ionization mechanism discussed in this report are combustion in a hydrogen diffusion flame (flame ionization detector), surface ionization in a plasma (thermionic ionization detector), photon ionization (photoionization detector and pulsed discharge helium ionization detector), attachment of thermal electrons (electron-capture detector), and ionization by collision with metastable helium species (helium ionization detector). The design, response characteristics, response mechanism, and suitability for fast gas chromatography are the main features summarized in this report. Mass spectrometric detection and atomic emission detection, which could be considered as ionization detectors of a more sophisticated and complex design, are not discussed in this report.

  2. Fully Automated Portable Comprehensive 2-Dimensional Gas Chromatography Device.

    PubMed

    Lee, Jiwon; Zhou, Menglian; Zhu, Hongbo; Nidetz, Robert; Kurabayashi, Katsuo; Fan, Xudong

    2016-10-06

    We developed a fully automated portable 2-dimensional (2-D) gas chromatography (GC x GC) device, which had a dimension of 60 cm × 50 cm × 10 cm and weight less than 5 kg. The device incorporated a micropreconcentrator/injector, commercial columns, micro-Deans switches, microthermal injectors, microphotoionization detectors, data acquisition cards, and power supplies, as well as computer control and user interface. It employed multiple channels (4 channels) in the second dimension ((2)D) to increase the (2)D separation time (up to 32 s) and hence (2)D peak capacity. In addition, a nondestructive flow-through vapor detector was installed at the end of the (1)D column to monitor the eluent from (1)D and assist in reconstructing (1)D elution peaks. With the information obtained jointly from the (1)D and (2)D detectors, (1)D elution peaks could be reconstructed with significantly improved (1)D resolution. In this Article, we first discuss the details of the system operating principle and the algorithm to reconstruct (1)D elution peaks, followed by the description and characterization of each component. Finally, 2-D separation of 50 analytes, including alkane (C6-C12), alkene, alcohol, aldehyde, ketone, cycloalkane, and aromatic hydrocarbon, in 14 min is demonstrated, showing the peak capacity of 430-530 and the peak capacity production of 40-80/min.

  3. A 2D mesoporous imine-linked covalent organic framework for high pressure gas storage applications.

    PubMed

    Rabbani, Mohammad Gulam; Sekizkardes, Ali Kemal; Kahveci, Zafer; Reich, Thomas E; Ding, Ransheng; El-Kaderi, Hani M

    2013-03-04

    Hole-some mixture: A 2D mesoporous covalent organic framework (see figure) featuring expanded pyrene cores and linked by imine linkages has a high surface area (SA(BET) = 2723 m(2)  g(-1)) and exhibits significant gas storage capacities under high pressure, which make this class of material very promising for gas storage applications.

  4. Evolved gas composition monitoring by repetitive injection gas chromatography.

    PubMed

    White, Robert L

    2015-11-20

    Performance characteristics and applications of a small volume gas chromatograph oven are described. Heating and cooling properties of the apparatus are evaluated and examples are given illustrating the advantages of greatly reducing the air bath volume surrounding fused silica columns. Fast heating and cooling of the oven permit it to be employed for repetitive injection analyses. By using fast gas chromatography separations to achieve short assay cycle times, the apparatus can be employed for on-line species-specific gas stream composition monitoring when volatile species concentrations vary on time scales of a few minutes or longer. This capability facilitates repeated sampling and fast gas chromatographic separations of volatile product mixtures produced during thermal analyses. Applications of repetitive injection gas chromatography-mass spectrometry evolved gas analyses to monitoring purge gas effluent streams containing volatile acid catalyzed polymer cracking products are described. The influence of thermal analysis and chromatographic experimental parameters on effluent sampling frequency are delineated.

  5. Temperature programmable microfabricated gas chromatography column

    DOEpatents

    Manginell, Ronald P.; Frye-Mason, Gregory C.

    2003-12-23

    A temperature programmable microfabricated gas chromatography column enables more efficient chemical separation of chemical analytes in a gas mixture by the integration of a resistive heating element and temperature sensing on the microfabricated column. Additionally, means are provided to thermally isolate the heated column from their surroundings. The small heat capacity and thermal isolation of the microfabricated column improves the thermal time response and power consumption, both important factors for portable microanalytical systems.

  6. Soil moisture by extraction and gas chromatography

    NASA Technical Reports Server (NTRS)

    Merek, E. L.; Carle, G. C.

    1973-01-01

    To determine moisture content of soils rapidly and conveniently extract moisture with methanol and determine water content of methanol extract by gas chromatography. Moisture content of sample is calculated from weight of water and methanol in aliquot and weight of methanol added to sample.

  7. 2D-MoO3 nanosheets for superior gas sensors

    NASA Astrophysics Data System (ADS)

    Ji, Fangxu; Ren, Xianpei; Zheng, Xiaoyao; Liu, Yucheng; Pang, Liuqing; Jiang, Jiaxing; Liu, Shengzhong (Frank)

    2016-04-01

    By taking advantages of both grinding and sonication, an effective exfoliation process is developed to prepare two-dimensional (2D) molybdenum oxide (MoO3) nanosheets. The approach avoids high-boiling-point solvents that would leave a residue and cause aggregation. Gas sensors fabricated using the 2D-MoO3 nanosheets provide a significantly enhanced chemical sensor performance. Compared with the sensors using bulk MoO3, the response of the 2D-MoO3 sensor increases from 7 to 33; the sensor response time is reduced from 27 to 21 seconds, and the recovery time is shortened from 26 to 10 seconds. We attribute the superior performance to the 2D-structure with a much increased surface area and reactive sites.By taking advantages of both grinding and sonication, an effective exfoliation process is developed to prepare two-dimensional (2D) molybdenum oxide (MoO3) nanosheets. The approach avoids high-boiling-point solvents that would leave a residue and cause aggregation. Gas sensors fabricated using the 2D-MoO3 nanosheets provide a significantly enhanced chemical sensor performance. Compared with the sensors using bulk MoO3, the response of the 2D-MoO3 sensor increases from 7 to 33; the sensor response time is reduced from 27 to 21 seconds, and the recovery time is shortened from 26 to 10 seconds. We attribute the superior performance to the 2D-structure with a much increased surface area and reactive sites. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00880a

  8. Non-planar microfabricated gas chromatography column

    DOEpatents

    Lewis, Patrick R.; Wheeler, David R.

    2007-09-25

    A non-planar microfabricated gas chromatography column comprises a planar substrate having a plurality of through holes, a top lid and a bottom lid bonded to opposite surfaces of the planar substrate, and inlet and outlet ports for injection of a sample gas and elution of separated analytes. A plurality of such planar substrates can be aligned and stacked to provide a longer column length having a small footprint. Furthermore, two or more separate channels can enable multi-channel or multi-dimensional gas chromatography. The through holes preferably have a circular cross section and can be coated with a stationary phase material or packed with a porous packing material. Importantly, uniform stationary phase coatings can be obtained and band broadening can be minimized with the circular channels. A heating or cooling element can be disposed on at least one of the lids to enable temperature programming of the column.

  9. Flow field thermal gradient gas chromatography.

    PubMed

    Boeker, Peter; Leppert, Jan

    2015-09-01

    Negative temperature gradients along the gas chromatographic separation column can maximize the separation capabilities for gas chromatography by peak focusing and also lead to lower elution temperatures. Unfortunately, so far a smooth thermal gradient over a several meters long separation column could only be realized by costly and complicated manual setups. Here we describe a simple, yet flexible method for the generation of negative thermal gradients using standard and easily exchangeable separation columns. The measurements made with a first prototype reveal promising new properties of the optimized separation process. The negative thermal gradient and the superposition of temperature programming result in a quasi-parallel separation of components each moving simultaneously near their lowered specific equilibrium temperatures through the column. Therefore, this gradient separation process is better suited for thermally labile molecules such as explosives and natural or aroma components. High-temperature GC methods also benefit from reduced elution temperatures. Even for short columns very high peak capacities can be obtained. In addition, the gradient separation is particularly beneficial for very fast separations below 1 min overall retention time. Very fast measurements of explosives prove the benefits of using negative thermal gradients. The new concept can greatly reduce the cycle time of high-resolution gas chromatography and can be integrated into hyphenated or comprehensive gas chromatography setups.

  10. Improved Thermal Modulator for Gas Chromatography

    NASA Technical Reports Server (NTRS)

    Hasselbrink, Ernest Frederick, Jr.; Hunt, Patrick J.; Sacks, Richard D.

    2008-01-01

    An improved thermal modulator has been invented for use in a variant of gas chromatography (GC). The variant in question denoted as two-dimensional gas chromatography (2DGC) or GC-GC involves the use of three series-connected chromatographic columns, in the form of capillary tubes coated interiorly with suitable stationary phases (compounds for which different analytes exhibit different degrees of affinity). The two end columns are relatively long and are used as standard GC columns. The thermal modulator includes the middle column, which is relatively short and is not used as a standard GC column: instead, its temperature is modulated to affect timed adsorption and desorption of analyte gases between the two end columns in accordance with a 2DGC protocol.

  11. Non Lyapunov stability of a constant spatially developing 2-D gas flow

    NASA Astrophysics Data System (ADS)

    Balint, Agneta M.; Balint, Stefan; Tanasie, Loredana

    2017-01-01

    Different types of stabilities (global, local) and instabilities (global absolute, local convective) of the constant spatially developing 2-D gas flow are analyzed in a particular phase space of continuously differentiable functions, endowed with the usual algebraic operations and the topology generated by the uniform convergence on the plane. For this purpose the Euler equations linearized at the constant flow are used. The Lyapunov stability analysis was presented in [1] and this paper is a continuation of [1].

  12. Permanent gas analysis using gas chromatography with vacuum ultraviolet detection.

    PubMed

    Bai, Ling; Smuts, Jonathan; Walsh, Phillip; Fan, Hui; Hildenbrand, Zacariah; Wong, Derek; Wetz, David; Schug, Kevin A

    2015-04-03

    The analysis of complex mixtures of permanent gases consisting of low molecular weight hydrocarbons, inert gases, and toxic species plays an increasingly important role in today's economy. A new gas chromatography detector based on vacuum ultraviolet (VUV) spectroscopy (GC-VUV), which simultaneously collects full scan (115-240 nm) VUV and UV absorption of eluting analytes, was applied to analyze mixtures of permanent gases. Sample mixtures ranged from off-gassing of decomposing Li-ion and Li-metal batteries to natural gas samples and water samples taken from private wells in close proximity to unconventional natural gas extraction. Gas chromatography separations were performed with a porous layer open tubular column. Components such as C1-C5 linear and branched hydrocarbons, water, oxygen, and nitrogen were separated and detected in natural gas and the headspace of natural gas-contaminated water samples. Of interest for the transport of lithium batteries were the detection of flammable and toxic gases, such as methane, ethylene, chloromethane, dimethyl ether, 1,3-butadiene, CS2, and methylproprionate, among others. Featured is the capability for deconvolution of co-eluting signals from different analytes.

  13. Responsive ionic liquid-polymer 2D photonic crystal gas sensors.

    PubMed

    Smith, Natasha L; Hong, Zhenmin; Asher, Sanford A

    2014-12-21

    We developed novel air-stable 2D polymerized photonic crystal (2DPC) sensing materials for visual detection of gas phase analytes such as water and ammonia by utilizing a new ionic liquid, ethylguanidine perchlorate (EGP) as the mobile phase. Because of the negligible ionic liquid vapor pressure these 2DPC sensors are indefinitely air stable and, therefore, can be used to sense atmospheric analytes. 2D arrays of ~640 nm polystyrene nanospheres were attached to the surface of crosslinked poly(hydroxyethyl methacrylate) (pHEMA)-based polymer networks dispersed in EGP. The wavelength of the bright 2D photonic crystal diffraction depends sensitively on the 2D array particle spacing. The volume phase transition response of the EGP-pHEMA system to water vapor or gaseous ammonia changes the 2DPC particle spacing, enabling the visual determination of the analyte concentration. Water absorbed by EGP increases the Flory-Huggins interaction parameter, which shrinks the polymer network and causes a blue shift in the diffracted light. Ammonia absorbed by the EGP deprotonates the pHEMA-co-acrylic acid carboxyl groups, swelling the polymer which red shifts the diffracted light.

  14. High pH reversed-phase chromatography with fraction concatenation for 2D proteomic analysis

    SciTech Connect

    Yang, Feng; Shen, Yufeng; Camp, David G.; Smith, Richard D.

    2012-04-01

    Orthogonal high-resolution separations are critical for attaining improved analytical dynamic ranges of proteome measurements. Concatenated high pH reversed phase liquid chromatography affords better separations than the strong cation exchange conventionally applied for two-dimensional shotgun proteomic analysis. For example, concatenated high pH reversed phase liquid chromatography increased identification coverage for peptides (e.g., by 1.8-fold) and proteins (e.g., by 1.6-fold) in shotgun proteomics analyses of a digested human protein sample. Additional advantages of concatenated high pH RPLC include improved protein sequence coverage, simplified sample processing, and reduced sample losses, making this an attractive first dimension separation strategy for two-dimensional proteomics analyses.

  15. Axial thermal gradients in microchip gas chromatography.

    PubMed

    Wang, Anzi; Hynynen, Sampo; Hawkins, Aaron R; Tolley, Samuel E; Tolley, H Dennis; Lee, Milton L

    2014-12-29

    Fabrication technologies for microelectromechanical systems (MEMS) allow miniaturization of conventional benchtop gas chromatography (GC) to portable, palm-sized microfabricated GC (μGC) devices, which are suitable for on-site chemical analysis and remote sensing. The separation performance of μGC systems, however, has not been on par with conventional GC. Column efficiency, peak symmetry and resolution are often compromised by column defects and non-ideal injections. The relatively low performance of μGC devices has impeded their further commercialization and broader application. In this work, the separation performance of μGC columns was improved by incorporating thermal gradient gas chromatography (TGGC). The analysis time was ∼20% shorter for TGGC separations compared to conventional temperature-programmed GC (TPGC) when a wide sample band was introduced into the column. Up to 50% reduction in peak tailing was observed for polar analytes, which improved their resolution. The signal-to-noise ratios (S/N) of late-eluting peaks were increased by 3-4 fold. The unique focusing effect of TGGC overcomes many of the previous shortcomings inherent in μGC analyses.

  16. Lyapunov stability of a spatially developing constant 2D gas flow

    NASA Astrophysics Data System (ADS)

    Balint, Agneta M.; Balint, Stefan; Szabo, Robert

    2017-01-01

    The well posedness of the perturbation propagation problem and the Lyapunov stability of a spatially developing constant 2D gas flow is analyzed in a particular infinite dimensional phase space. The elements of the phase space are continuously differentiable functions, the algebraic operations are usual and the topology is that generated by the uniform convergence. The well posedness of the propagation problem as well the Lyapunov stability with respect to the instantaneous and with respect to source produced permanent time harmonic perturbations is investigated. Some of the obtained results are completely different from those reported in the literature.

  17. Laser Absorption spectrometer instrument for tomographic 2D-measurement of climate gas emission from soils

    NASA Astrophysics Data System (ADS)

    Seidel, Anne; Wagner, Steven; Dreizler, Andreas; Ebert, Volker

    2014-05-01

    One of the most intricate effects in climate modelling is the role of permafrost thawing during the global warming process. Soil that has formerly never totally lost its ice cover now emits climate gases due to melting processes[1]. For a better prediction of climate development and possible feedback mechanisms, insights into physical procedures (like e.g. gas emission from underground reservoirs) are required[2]. Therefore, a long-term quantification of greenhouse gas concentrations (and further on fluxes) is necessary and the related structures that are responsible for emission need to be identified. In particular the spatial heterogeneity of soils caused by soil internal structures (e.g. soil composition changes or surface cracks) or by surface modifications (e.g. by plant growth) generate considerable complexities and difficulties for local measurements, for example with soil chambers. For such situations, which often cannot be avoided, a spatially resolved 2D-measurement to identify and quantify the gas emission from the structured soil would be needed, to better understand the influence of the soil sub-structures on the emission behavior. Thus we designed a spatially scanning laser absorption spectrometer setup to determine a 2D-gas concentration map in the soil-air boundary layer. The setup is designed to cover the surfaces in the range of square meters in a horizontal plane above the soil to be investigated. Existing field instruments for gas concentration or flux measurements are based on point-wise measurements, so structure identification is very tedious or even impossible. For this reason, we have developed a tomographic in-situ instrument based on TDLAS ('tunable diode laser absorption spectroscopy') that delivers absolute gas concentration distributions of areas with 0.8m × 0.8m size, without any need for reference measurements with a calibration gas. It is a simple and robust device based on a combination of scanning mirrors and reflecting foils, so

  18. Ferroelectricity, Antiferroelectricity and Ultrathin 2D Electron/Hole Gas in Multifunctional Monolayer MXene.

    PubMed

    Chandrasekaran, Anand; Mishra, Avanish; Singh, Abhishek Kumar

    2017-04-04

    Presence of ferroelectric polarization in 2D materials is extremely rare due to the effect of the surface depolarizing field. Here, we use first-principles calculations to show the largest out-of-plane polarization observed in a monolayer in functionalized MXenes (Sc2CO2). The switching of polarization in this new class of ferroelectric materials occurs through an previously unknown intermediate antiferroelectric structure thus establishing three states for applications in low-dimensional non-volatile memory. We show that the armchair domain-interface acts as an 1D metallic nanowire separating two insulating domains. In the case of the van-der-Waals bilayer we observe, interestingly, the presence of an ultrathin 2D electron/hole gas (2DEG) on the top/bottom layers, respectively, due to the redistrubution of charge carriers. The 2DEG is non-degenerate due to spin-orbit-coupling, thus paving the way for spin-orbitronic devices. The coexistence of ferroelectricity, antiferroelectricity, 2DEG and spin-orbit splitting in this system suggests that such 2D polar materials possess high potential for device application in a multitude of fields ranging from nanoelectronics to photovoltaics.

  19. Ternary recombination of H3+, H2D+, HD2+, and D3+ with electrons in He/Ar/H2/D2 gas mixtures

    NASA Astrophysics Data System (ADS)

    Kalosi, Abel; Dohnal, Petr; Plasil, Radek; Johnsen, Rainer; Glosik, Juraj

    2016-09-01

    The temperature dependence of the ternary recombination rate coefficients of H2D+ and HD2+ ions has been studied in the temperature range of 80-150 K at pressures from 500 to 1700 Pa in a stationary afterglow apparatus equipped with a cavity ring-down spectrometer. Neutral gas mixtures consisting of He/Ar/H2/D2 (with typical number densities 1017 /1014 /1014 /1014 cm-3) were employed to produce the desired ionic species and their fractional abundances were monitored as a function of helium pressure and the [D2]/[H2] ratio of the neutral gas. In addition, the translational and the rotational temperature and the ortho to para ratio were monitored for both H2D+ and HD2+ ions. A fairly strong pressure dependence of the effective recombination rate coefficient was observed for both ion species, leading to ternary recombination rate coefficients close to those previously found for (helium assisted) ternary recombination of H3+ and D3+. Work supported by: Czech Science Foundation projects GACR 14-14649P, GACR 15-15077S, GACR P209/12/0233, and by Charles University in Prague Project Nr. GAUK 692214.

  20. Multidimensional gas chromatography beyond simple volatiles separation.

    PubMed

    Chin, Sung-Tong; Marriott, Philip J

    2014-08-18

    Multidimensional separation in gas chromatography (MDGC) plays an important role in chemical analysis. This review presents selected literature on MDGC development and examples of the range of functionality reported for MDGC methods over the past 2 decades. With the most obvious advantage of providing much greater capacity for resolving constituents of a sample, MDGC extends analytical efficiency to a more substantial molecular coverage, combined with operational flexibility. But by judicious choice of implementation method, important chemical information relating to the sample, its components, potentially physico-chemical properties, and improved capacity for absolute identification may be realised. Sample-to-sample comparison is improved, and sample characterisation is facilitated especially when MDGC is combined with the informing power of modern mass spectrometry. Innovative MDGC arrangements allow high resolution coupled with spectroscopy and alternative bioassays, and delivers molecular elucidation in ways that are beyond just simple analysis of volatiles.

  1. Freeze drying for gas chromatography stationary phase deposition

    DOEpatents

    Sylwester, Alan P.

    2007-01-02

    The present disclosure relates to methods for deposition of gas chromatography (GC) stationary phases into chromatography columns, for example gas chromatography columns. A chromatographic medium is dissolved or suspended in a solvent to form a composition. The composition may be inserted into a chromatographic column. Alternatively, portions of the chromatographic column may be exposed or filled with the composition. The composition is permitted to solidify, and at least a portion of the solvent is removed by vacuum sublimation.

  2. Applications of resistive heating in gas chromatography: a review.

    PubMed

    Jacobs, Matthew R; Hilder, Emily F; Shellie, Robert A

    2013-11-25

    Gas chromatography is widely applied to separate, identify, and quantify components of samples in a timely manner. Increasing demand for analytical throughput, instrument portability, environmental sustainability, and more economical analysis necessitates the development of new gas chromatography instrumentation. The applications of resistive column heating technologies have been espoused for nearly thirty years and resistively heated gas chromatography has been commercially available for the last ten years. Despite this lengthy period of existence, resistively heated gas chromatography has not been universally adopted. This low rate of adoption may be partially ascribed to the saturation of the market with older convection oven technology, coupled with other analytical challenges such as sampling, injection, detection and data processing occupying research. This article assesses the advantages and applications of resistive heating in gas chromatography and discusses practical considerations associated with adoption of this technology.

  3. Moving thermal gradients in gas chromatography.

    PubMed

    Tolley, H Dennis; Tolley, Samuel E; Wang, Anzi; Lee, Milton L

    2014-12-29

    This paper examines the separation effects of a moving thermal gradient on a chromatographic column in gas chromatography. This movement of the gradient has a focusing effect on the analyte bands, limiting band broadening in the column. Here we examine the relationship between the slope of this gradient, the velocity of the gradient and the resulting band width. Additionally we examine how transport of analytes along the column at their analyte specific constant temperatures, determined by the gradient slope and velocity, affects resolution. This examination is based primarily on a theoretical model of partitioning and transport of analyte under low concentration conditions. Preliminary predictions indicate that analytes reach near constant temperatures, relative positions and resolutions in less than 100cm of column transport. Use of longer columns produces very little improvement in resolution for any fixed slope. Properties of the thermal gradient determine a fixed solute band width for each analyte. These widths are nearly reached within the first 40-70cm, after which little broadening or narrowing of the bands occur. The focusing effect of the thermal gradient corrects for broad injections, reduces effects of irregular stationary phase coatings and can be used with short columns for fast analysis. Thermal gradient gas chromatographic instrumentation was constructed and used to illustrate some characteristics predicted from the theoretical results.

  4. Vacuum ultraviolet detector for gas chromatography.

    PubMed

    Schug, Kevin A; Sawicki, Ian; Carlton, Doug D; Fan, Hui; McNair, Harold M; Nimmo, John P; Kroll, Peter; Smuts, Jonathan; Walsh, Phillip; Harrison, Dale

    2014-08-19

    Analytical performance characteristics of a new vacuum ultraviolet (VUV) detector for gas chromatography (GC) are reported. GC-VUV was applied to hydrocarbons, fixed gases, polyaromatic hydrocarbons, fatty acids, pesticides, drugs, and estrogens. Applications were chosen to feature the sensitivity and universal detection capabilities of the VUV detector, especially for cases where mass spectrometry performance has been limited. Virtually all chemical species absorb and have unique gas phase absorption cross sections in the approximately 120-240 nm wavelength range monitored. Spectra are presented, along with the ability to use software for deconvolution of overlapping signals. Some comparisons with experimental synchrotron data and computed theoretical spectra show good agreement, although more work is needed on appropriate computational methods to match the simultaneous broadband electronic and vibronic excitation initiated by the deuterium lamp. Quantitative analysis is governed by Beer-Lambert Law relationships. Mass on-column detection limits reported for representatives of different classes of analytes ranged from 15 (benzene) to 246 pg (water). Linear range measured at peak absorption for benzene was 3-4 orders of magnitude. Importantly, where absorption cross sections are known for analytes, the VUV detector is capable of absolute determination (without calibration) of the number of molecules present in the flow cell in the absence of chemical interferences. This study sets the stage for application of GC-VUV technology across a wide breadth of research areas.

  5. Spin relaxations in 2D electron gas determined by the memory in the carrier dynamics.

    NASA Astrophysics Data System (ADS)

    Sherman, Eugene; Glazov, Mikhail

    2007-03-01

    The effects of long memory, in carrier dynamics in a magnetic field, on spin polarization evolution in 2D electron gas are investigated qualitatively and quantitatively. As examples we consider (i) systems with random Rashba-type SO coupling and (ii) quantum wells with rigid short-range scatterers (antidotes) and regular Dresselhaus SO coupling. In both cases the spin dynamics is strongly non-Markovian. In the system with the random SO coupling the time dependence of the spin polarization shows Gaussian rather than exponential behavior with the cusps corresponding to the electron revolutions. The relaxation speeds up with the increase of the magnetic field. In the system with antidotes scattering, the spin polarization shows a long-tail behavior with the relaxation rate determined by inelastic electron-phonon and electron-electron collisions and demonstrates unusual field dependence.

  6. Chromatography

    MedlinePlus

    Chromatography is a way of separating two or more chemical compounds. Chemical compounds are chemicals that are ... of chemical compound. There are different kinds of chromatography. These include gas, high pressure liquid, or ion ...

  7. Metal Decoration Effects on the Gas-Sensing Properties of 2D Hybrid-Structures on Flexible Substrates

    PubMed Central

    Cho, Byungjin; Yoon, Jongwon; Lim, Sung Kwan; Kim, Ah Ra; Choi, Sun-Young; Kim, Dong-Ho; Lee, Kyu Hwan; Lee, Byoung Hun; Ko, Heung Cho; Hahm, Myung Gwan

    2015-01-01

    We have investigated the effects of metal decoration on the gas-sensing properties of a device with two-dimensional (2D) molybdenum disulfide (MoS2) flake channels and graphene electrodes. The 2D hybrid-structure device sensitively detected NO2 gas molecules (>1.2 ppm) as well as NH3 (>10 ppm). Metal nanoparticles (NPs) could tune the electronic properties of the 2D graphene/MoS2 device, increasing sensitivity to a specific gas molecule. For instance, palladium NPs accumulate hole carriers of graphene/MoS2, electronically sensitizing NH3 gas molecules. Contrarily, aluminum NPs deplete hole carriers, enhancing NO2 sensitivity. The synergistic combination of metal NPs and 2D hybrid layers could be also applied to a flexible gas sensor. There was no serious degradation in the sensing performance of metal-decorated MoS2 flexible devices before/after 5000 bending cycles. Thus, highly sensitive and endurable gas sensor could be achieved through the metal-decorated 2D hybrid-structure, offering a useful route to wearable electronic sensing platforms. PMID:26404279

  8. A new model for two-dimensional numerical simulation of pseudo-2D gas-solids fluidized beds

    SciTech Connect

    Li, Tingwen; Zhang, Yongmin

    2013-10-11

    Pseudo-two dimensional (pseudo-2D) fluidized beds, for which the thickness of the system is much smaller than the other two dimensions, is widely used to perform fundamental studies on bubble behavior, solids mixing, or clustering phenomenon in different gas-solids fluidization systems. The abundant data from such experimental systems are very useful for numerical model development and validation. However, it has been reported that two-dimensional (2D) computational fluid dynamic (CFD) simulations of pseudo-2D gas-solids fluidized beds usually predict poor quantitative agreement with the experimental data, especially for the solids velocity field. In this paper, a new model is proposed to improve the 2D numerical simulations of pseudo-2D gas-solids fluidized beds by properly accounting for the frictional effect of the front and back walls. Two previously reported pseudo-2D experimental systems were simulated with this model. Compared to the traditional 2D simulations, significant improvements in the numerical predictions have been observed and the predicted results are in better agreement with the available experimental data.

  9. Two dimensional assisted liquid chromatography - a chemometric approach to improve accuracy and precision of quantitation in liquid chromatography using 2D separation, dual detectors, and multivariate curve resolution.

    PubMed

    Cook, Daniel W; Rutan, Sarah C; Stoll, Dwight R; Carr, Peter W

    2015-02-15

    Comprehensive two-dimensional liquid chromatography (LC×LC) is rapidly evolving as the preferred method for the analysis of complex biological samples owing to its much greater resolving power compared to conventional one-dimensional (1D-LC). While its enhanced resolving power makes this method appealing, it has been shown that the precision of quantitation in LC×LC is generally not as good as that obtained with 1D-LC. The poorer quantitative performance of LC×LC is due to several factors including but not limited to the undersampling of the first dimension and the dilution of analytes during transit from the first dimension ((1)D) column to the second dimension ((2)D) column, and the larger relative background signals. A new strategy, 2D assisted liquid chromatography (2DALC), is presented here. 2DALC makes use of a diode array detector placed at the end of each column, producing both multivariate (1)D and two-dimensional (2D) chromatograms. The increased resolution of the analytes provided by the addition of a second dimension of separation enables the determination of analyte absorbance spectra from the (2)D detector signal that are relatively pure and can be used to initiate the treatment of data from the first dimension detector using multivariate curve resolution-alternating least squares (MCR-ALS). In this way, the approach leverages the strengths of both separation methods in a single analysis: the (2)D detector data is used to provide relatively pure analyte spectra to the MCR-ALS algorithm, and the final quantitative results are obtained from the resolved (1)D chromatograms, which has a much higher sampling rate and lower background signal than obtained in conventional single detector LC×LC, to obtain accurate and precise quantitative results. It is shown that 2DALC is superior to both single detector selective or comprehensive LC×LC and 1D-LC for quantitation of compounds that appear as severely overlapped peaks in the (1)D chromatogram - this is

  10. Gas chromatography using resistive heating technology.

    PubMed

    Wang, Anzi; Tolley, H Dennis; Lee, Milton L

    2012-10-26

    Air bath ovens are standard in conventional gas chromatography (GC) instruments because of their simplicity and reliability for column temperature control. However, their low heating rates, high power consumption and bulky size are in conflict with the increasing demands for fast separation and portable instrumentation. The deficiencies of air bath ovens can be eliminated using resistive heating technology, as the column is conductively heated by compact resistive heaters with low thermal mass. Resistive heating methods were employed in the early years of GC history, and they are emerging again as instrumentation is becoming more compact and sophisticated. Numerous designs have been tested and some have been successfully commercialized. Development of portable GC systems, including lab-on-a-chip devices, greatly benefits from the use of small, low-power resistive heating hardware. High speed GC separations using conventional instruments also can be best achieved with resistive heating modules. Despite some of its own inherent disadvantages, including efficiency loss, complex manufacturing and inconvenient column maintenance, resistive heating is expected to rapidly become a mature technology and even replace oven heating in the not-to-distant future.

  11. The success of Fermi gas model for overall scaling of 2D metal-to-insulator transition data

    NASA Astrophysics Data System (ADS)

    Cheremisin, M. V.

    2017-03-01

    The melting condition for two-dimensional Wigner solid (Platzman and Fukuyama, 1974) [14] is shown to contain an error of a factor of π. The analysis of experimental data for apparent 2D metal-to-insulator transition shows that the Wigner solidification (Tanatar and Ceperley, 1989) [16] has been never achieved. Within routine Fermi gas model both the metallic and insulating behavior of different 2D system for actual range of carrier densities and temperatures is explained.

  12. Mixed Stationary Liquid Phases for Gas-Liquid Chromatography.

    ERIC Educational Resources Information Center

    Koury, Albert M.; Parcher, Jon F.

    1979-01-01

    Describes a laboratory technique for use in an undergraduate instrumental analysis course that, using the interpretation of window diagrams, prepares a mixed liquid phase column for gas-liquid chromatography. A detailed procedure is provided. (BT)

  13. ENVIRONMENTAL APPLICATION OF GAS CHROMATOGRAPHY/ATOMIC EMISSION DETECTION

    EPA Science Inventory

    A gas chromatography/atomic emission detector (GC/AED) system has been evaluated for its applicability to environmental analysis. Detection limits, elemental response factors, and regression analysis data were determined for 58 semivolatile environmental contaminants. Detection l...

  14. Numerical and experimental study of gas flows in 2D and 3D microchannels

    NASA Astrophysics Data System (ADS)

    Guo, Xiaohui; Huang, Chihyung; Alexeenko, Alina; Sullivan, John

    2008-02-01

    In the experiments conducted at Purdue, the air flow in rectangular cross-section microchannels was investigated using pressure sensitive paint. The high resolution pressure measurements were obtained for inlet-to-outlet pressure ratios from 1.76 to 20 with the outlet Knudsen numbers in the range from 0.003 to 0.4 based on the hydraulic diameter of 151.7 µm and the length-to-height ratio of about 50. In the slip flow regime, the air flow was simulated by the 2D and 3D Navier-Stokes equations with no-slip and slip boundary conditions. For various pressure ratios, the entrance flow development, compressibility and rarefaction effects were observed in both experiments and numerical simulations. It was found that the accurate modeling of gas flows in finite-length channels requires the inlet and outlet reservoirs to be included in computations. Effects of entrance geometry on the friction factor were studied for 3D cases. In both experiments and numerical modeling, significant pressure drop was found starting at the inlet chamber. The numerical modeling also predicted an apparent temperature drop at the channel exit.

  15. Intracellular ROS mediates gas plasma-facilitated cellular transfection in 2D and 3D cultures

    PubMed Central

    Xu, Dehui; Wang, Biqing; Xu, Yujing; Chen, Zeyu; Cui, Qinjie; Yang, Yanjie; Chen, Hailan; Kong, Michael G.

    2016-01-01

    This study reports the potential of cold atmospheric plasma (CAP) as a versatile tool for delivering oligonucleotides into mammalian cells. Compared to lipofection and electroporation methods, plasma transfection showed a better uptake efficiency and less cell death in the transfection of oligonucleotides. We demonstrated that the level of extracellular aqueous reactive oxygen species (ROS) produced by gas plasma is correlated with the uptake efficiency and that this is achieved through an increase of intracellular ROS levels and the resulting increase in cell membrane permeability. This finding was supported by the use of ROS scavengers, which reduced CAP-based uptake efficiency. In addition, we found that cold atmospheric plasma could transfer oligonucleotides such as siRNA and miRNA into cells even in 3D cultures, thus suggesting the potential for unique applications of CAP beyond those provided by standard transfection techniques. Together, our results suggest that cold plasma might provide an efficient technique for the delivery of siRNA and miRNA in 2D and 3D culture models. PMID:27296089

  16. Rise characteristics of gas bubbles in a 2D rectangular column: VOF simulations vs experiments

    SciTech Connect

    Krishna, R.; Baten, J.M. van

    1999-10-01

    About five centuries ago, Leonardo da Vinci described the sinuous motion of gas bubbles rising in water. The authors have attempted to simulate the rise trajectories of bubbles of 4, 5, 7, 8, 9, 12, and 20 mm in diameter rising in a 2D rectangular column filled with water. The simulations were carried out using the volume-of-fluid (VOF) technique developed by Hirt and Nichols (J. Computational Physics, 39, 201--225 (1981)). To solve the Navier-Stokes equations of motion the authors used a commercial solver, CFX 4.1c of AEA Technology, UK. They developed their own bubble-tracking algorithm to capture sinuous bubble motions. The 4 and 5 mm bubbles show large lateral motions observed by Da Vinci. The 7, 8 and 9 mm bubble behave like jellyfish. The 12 mm bubble flaps its wings like a bird. The extent of lateral motion of the bubbles decreases with increasing bubble size. Bubbles larger than 20 mm in size assume a spherical cap form and simulations of the rise characteristics match experiments exactly. VOF simulations are powerful tools for a priori determination of the morphology and rise characteristics of bubbles rising in a liquid. Bubble-bubble interactions are also properly modeled by the VOF technique.

  17. Solid surface mapping by inverse gas chromatography.

    PubMed

    Gutiérrez, M C; Osuna, S; Baráibar, I

    2005-09-16

    Inverse gas chromatography (IGC) at infinite dilution, is a technique for characterising solid surfaces. Current practice is the injection of n-alkane homologous series to obtain the free energy of adsorption of the CH2 group, from which the London component of the solid surface free energy, gamma(d)s, is calculated. A value around 40 mJ/m2 is obtained for poly(ethylene), and 30 mJ/m2 for a clean glass fibre, while the potential surface interactivity of a glass fibre is far greater than that of poly(ethylene). A specific component of the surface, in mJ/m2, should be calculated in order to obtain significant parameters. As applied up to date, when calculating the specific component of the surface energy, the fact that W(sp)a energy values are in a totally different scale than AN or DN values is a major drawback. Consequently, Ka and Kb values obtained are in arbitrary energy units, different from those of the London component measured by injecting the n-alkane series. This paper proposes a method to obtain Ka and Kb values of the surface in the same energetic scale than the London component. The method enables us to correct the traditional London component of a solid, obtaining a new value, where the amount of WaCH2 accounting for Debye interactions with polar sites, is excluded. As a result, an approach to surface mapping is performed in several different substrate materials. We show results obtained on different solid surfaces: poly(ethylene), clean glass fibre, glass beads, chemically modified glass beads and carbon fibre.

  18. NOVEL CONTINUOUS PH/SALT GRADIENT AND PEPTIDE SCORE FOR STRONG CATION EXCHANGE CHROMATOGRAPHY IN 2D-NANO-LC/MSMS PEPTIDE IDENTIFICATION FOR PROTEOMICS

    EPA Science Inventory

    Tryptic digests of human serum albumin (HSA) and human lung epithelial cell lysates were used as test samples in a novel proteomics study. Peptides were separated and analyzed using 2D-nano-LC/MSMS with strong cation exchange (SCX) and reverse phase (RP) chromatography and contin...

  19. Condensate fraction in a 2D Bose gas measured across the Mott-insulator transition.

    PubMed

    Spielman, I B; Phillips, W D; Porto, J V

    2008-03-28

    We realize a single-band 2D Bose-Hubbard system with Rb atoms in an optical lattice and measure the condensate fraction as a function of lattice depth, crossing from the superfluid to the Mott-insulating phase. We quantitatively identify the location of the superfluid to normal transition by observing when the condensed fraction vanishes. Our measurement agrees with recent quantum Monte Carlo calculations for a finite-sized 2D system to within experimental uncertainty.

  20. Upgrade of PARC2D to include real gas effects. [computer program for flowfield surrounding aeroassist flight experiment

    NASA Technical Reports Server (NTRS)

    Saladino, Anthony; Praharaj, Sarat C.; Collins, Frank G.; Seaford, C. Mark

    1990-01-01

    This paper presents a description of the changes and additions to the perfect gas PARC2D code to include chemical equilibrium effects, resulting in a code called PARCEQ2D. The work developed out of a need to have the capability of more accurately representing the flowfield surrounding the aeroassist flight experiment (AFE) vehicle. Use is made of the partition function of statistical mechanics in the evaluation of the thermochemical properties. This approach will allow the PARC code to be extended to thermal nonequilibrium when this task is undertaken in the future. The transport properties follow from formulae from the kinetic theory of gases. Results are presented for a two-dimensional AFE that compare perfect gas and real gas solutions at flight conditions, showing vast differences between the two cases.

  1. Time evolution analysis of a 2D solid gas equilibrium: a model system for molecular adsorption and diffusion

    NASA Astrophysics Data System (ADS)

    Berner, S.; Brunner, M.; Ramoino, L.; Suzuki, H.; Güntherodt, H.-J.; Jung, T. A.

    2001-11-01

    The adsorption of sub-phthalocyanine molecules on Ag(1 1 1) has been studied by means of scanning tunneling microscopy (STM). The molecules are observed in different two-dimensional (2D) phases of adsorption which coexist in thermodynamic equilibrium. In the condensed phase the molecules form well-ordered islands with a honeycomb pattern. In the gas phase single molecules can be discriminated in single scan lines by characteristic tip excursions which occur randomly. The energy barrier for surface diffusion as well as the condensation energy to form 2D islands is estimated and discussed.

  2. Less common applications of monoliths III. Gas chromatography

    PubMed Central

    Svec, Frantisek; Kurganov, Alexander A.

    2008-01-01

    Porous polymer monoliths emerged about two decades ago. Despite this short time, they are finding applications in a variety of fields. In addition to the most common and certainly best known use of this new category of porous media as stationary phases in liquid chromatography, monolithic materials also found their applications in other areas. This review article focuses on monoliths in capillaries designed for separations in gas chromatography. PMID:17645884

  3. Continuum in MDGC Technology: From Classical Multidimensional to Comprehensive Two-Dimensional Gas Chromatography.

    PubMed

    Kulsing, Chadin; Nolvachai, Yada; Rawson, Paul; Evans, David J; Marriott, Philip J

    2016-04-05

    Recent advances in multidimensional gas chromatography (MDGC) comprise methods such as multiple heart-cut (H/C) analysis and comprehensive two-dimensional gas chromatography (GC × GC); however, clear approaches to evaluate the MDGC results, choice of the most appropriate method, and optimized separation remain of concern. In order to track the capability of these analytical techniques and select an effective experimental approach, a fundamental approach was developed utilizing a time summation model incorporating temperature-dependent linear solvation energy relationship (LSER). The approach allows prediction of optimized analyte distribution in the 2D space for various MDGC approaches employing different experimental variables such as column lengths, temperature programs, and stationary phase combinations in order to evaluate separation performance (apparent (1)D, (2)D, total number of separated peaks, and orthogonality) for simulated MDGC results. The methodology applied LSER to generate results for nonpolar-polar and polar-nonpolar 2D column configurations for separation of 678 compounds in an oxidized kerosene-based jet fuel sample. Three-dimensional plots were generated in order to illustrate the dependency of separation performance on (2)D column length and number of injections for different stationary phase combinations. With a given limit of analysis time, a MDGC approach to obtain an optimized total separated peak number for a particular column set was proposed depending on (1)D and (2)D analyte peak distribution. This study introduces fundamental concepts and establishes approaches to design effective GC × GC or multiple H/C systems for different column combinations, to provide the best overall separation outcomes with the highest separated peak number and/or orthogonality.

  4. Gas chromatography/matrix-isolation apparatus

    DOEpatents

    Reedy, Gerald T.

    1986-01-01

    A gas-sample collection device provides matrix isolation of individual gas bands from a gas chromatographic separation and for the spectroscopic analysis of the individual sample bands. The device includes a vacuum chamber containing a rotatably supported, specular carousel having at least one reflecting surface for holding a sample deposited thereon. A gas inlet is provided for depositing a mixture of sample and matrix material on the reflecting surface which is maintained at a sufficiently low temperature to cause solidification. A first parabolic mirror directs an incident beam of electromagnetic radiation, such as in the infrared (IR) spectrum, from a source onto the sample/matrix mixture while a second parabolic mirror directs a second beam of electromagnetic radiation reflected by the specular surface to an IR spectrometer for determining the absorption spectra of the sample material deposited on the reflecting surface. The pair of off-axis parabolic mirrors having a common focal point are positioned outside of the vacuum chamber and may be displaced in combination for improved beam positioning and alignment. The carousel is provided with an aperture for each reflecting surface to facilitate accurate positioning of the incident beam relative to the gas-samples under analysis. Improved gas-sample deposition is insured by the use of a long focal length stereomicroscope positioned outside of the vacuum chamber for monitoring sample formation through a window, while the sample collector is positioned outside of the zone bounded by the incident and reflected electromagnetic beams for improved sample access and monitoring.

  5. Micromachined Gas Chromatography Microsystem For Complex Gas Analysis (BRIEFING CHARTS)

    DTIC Science & Technology

    2007-03-07

    Wireless Integrated Microsystems (WIMS), Applications • Gas Analysis Using µGC • The “Actuator”: Integrated Gas Micropump • Concluding Remarks, Future...mode Analysis mode • No previous gas micropump meets the WIMS µGC requirements. • Size and power...leakage. • Single mode operation Summary of Previous Gas Micropumps NSF ERC for Wireless Integrated MicroSystems (WIMS) 22 • Goal: Develop a miniature

  6. Gas chromatography/matrix-isolation apparatus

    DOEpatents

    Reedy, G.T.

    1986-06-10

    A gas-sample collection device provides matrix isolation of individual gas bands from a gas chromatographic separation and for the spectroscopic analysis of the individual sample bands. The device includes a vacuum chamber containing a rotatably supported, specular carousel having at least one reflecting surface for holding a sample deposited thereon. A gas inlet is provided for depositing a mixture of sample and matrix material on the reflecting surface which is maintained at a sufficiently low temperature to cause solidification. A first parabolic mirror directs an incident beam of electromagnetic radiation, such as in the infrared (IR) spectrum, from a source onto the sample/matrix mixture while a second parabolic mirror directs a second beam of electromagnetic radiation reflected by the specular surface to an IR spectrometer for determining the absorption spectra of the sample material deposited on the reflecting surface. The pair of off-axis parabolic mirrors having a common focal point are positioned outside of the vacuum chamber and may be displaced in combination for improved beam positioning and alignment. The carousel is provided with an aperture for each reflecting surface to facilitate accurate positioning of the incident beam relative to the gas-samples under analysis. Improved gas-sample deposition is insured by the use of a long focal length stereomicroscope positioned outside of the vacuum chamber for monitoring sample formation through a window, while the sample collector is positioned outside of the zone bounded by the incident and reflected electromagnetic beams for improved sample access and monitoring. 10 figs.

  7. An application of gas chromatography to planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Oyama, V.

    1974-01-01

    A gas chromatography developed for the Viking experiment is described. The instrument is designed to measure gases in planetary atmospheres and head space in a chamber. It is hoped that the chromatograph will also measure any biological activity present in these environments.

  8. Specialized Gas Chromatography--Mass Spectrometry Systems for Clinical Chemistry.

    ERIC Educational Resources Information Center

    Gochman, Nathan; And Others

    1979-01-01

    A discussion of the basic design and characteristics of gas chromatography-mass spectrometry systems used in clinical chemistry. A comparison of three specific systems: the Vitek Olfax IIA, Hewlett-Packard HP5992, and Du Pont DP-102 are included. (BB)

  9. Enthalpy of Vaporization by Gas Chromatography: A Physical Chemistry Experiment

    ERIC Educational Resources Information Center

    Ellison, Herbert R.

    2005-01-01

    An experiment is conducted to measure the enthalpy of vaporization of volatile compounds like methylene chloride, carbon tetrachloride, and others by using gas chromatography. This physical property was measured using a very tiny quantity of sample revealing that it is possible to measure the enthalpies of two or more compounds at the same time.

  10. Using Single Drop Microextraction for Headspace Analysis with Gas Chromatography

    ERIC Educational Resources Information Center

    Riccio, Daniel; Wood, Derrick C.; Miller, James M.

    2008-01-01

    Headspace (HS) gas chromatography (GC) is commonly used to analyze samples that contain non-volatiles. In 1996, a new sampling technique called single drop microextraction, SDME, was introduced, and in 2001 it was applied to HS analysis. It is a simple technique that uses equipment normally found in the undergraduate laboratory, making it ideal…

  11. Simulation of the Physical Chemistry of Gas Chromatography

    NASA Astrophysics Data System (ADS)

    Haigh, John; Lord, J. R.

    2000-11-01

    A menu allows navigation between the sections of Simulation of the Physical Chemistry of Gas Chromatography. Experiments can be stopped and restarted easily. Many definitions and other technical points are available as hypertext. The student is encouraged to look quickly through the whole package, then to carefully work through the text and experiments.

  12. Highly crosslinked silicon polymers for gas chromatography columns

    NASA Technical Reports Server (NTRS)

    Shen, Thomas C. (Inventor)

    1994-01-01

    A new highly crosslinked silicone polymer particle for gas chromatography application and a process for synthesizing such copolymer are described. The new copolymer comprises vinyltriethoxysilane and octadecyltrichlorosilane. The copolymer has a high degree of crosslinking and a cool balance of polar to nonpolar sites in the porous silicon polymer assuring fast separation of compounds of variable polarity.

  13. 2D models of gas flow and ice grain acceleration in Enceladus' vents using DSMC methods

    NASA Astrophysics Data System (ADS)

    Tucker, Orenthal J.; Combi, Michael R.; Tenishev, Valeriy M.

    2015-09-01

    The gas distribution of the Enceladus water vapor plume and the terminal speeds of ejected ice grains are physically linked to its subsurface fissures and vents. It is estimated that the gas exits the fissures with speeds of ∼300-1000 m/s, while the micron-sized grains are ejected with speeds comparable to the escape speed (Schmidt, J. et al. [2008]. Nature 451, 685-688). We investigated the effects of isolated axisymmetric vent geometries on subsurface gas distributions, and in turn, the effects of gas drag on grain acceleration. Subsurface gas flows were modeled using a collision-limiter Direct Simulation Monte Carlo (DSMC) technique in order to consider a broad range of flow regimes (Bird, G. [1994]. Molecular Gas Dynamics and the Direct Simulation of Gas Flows. Oxford University Press, Oxford; Titov, E.V. et al. [2008]. J. Propul. Power 24(2), 311-321). The resulting DSMC gas distributions were used to determine the drag force for the integration of ice grain trajectories in a test particle model. Simulations were performed for diffuse flows in wide channels (Reynolds number ∼10-250) and dense flows in narrow tubular channels (Reynolds number ∼106). We compared gas properties like bulk speed and temperature, and the terminal grain speeds obtained at the vent exit with inferred values for the plume from Cassini data. In the simulations of wide fissures with dimensions similar to that of the Tiger Stripes the resulting subsurface gas densities of ∼1014-1020 m-3 were not sufficient to accelerate even micron-sized ice grains to the Enceladus escape speed. In the simulations of narrow tubular vents with radii of ∼10 m, the much denser flows with number densities of 1021-1023 m-3 accelerated micron-sized grains to bulk gas speed of ∼600 m/s. Further investigations are required to understand the complex relationship between the vent geometry, gas source rate and the sizes and speeds of ejected grains.

  14. Bayesian inversion of marine CSEM data from the Scarborough gas field using a transdimensional 2-D parametrization

    NASA Astrophysics Data System (ADS)

    Ray, Anandaroop; Key, Kerry; Bodin, Thomas; Myer, David; Constable, Steven

    2014-12-01

    We apply a reversible-jump Markov chain Monte Carlo method to sample the Bayesian posterior model probability density function of 2-D seafloor resistivity as constrained by marine controlled source electromagnetic data. This density function of earth models conveys information on which parts of the model space are illuminated by the data. Whereas conventional gradient-based inversion approaches require subjective regularization choices to stabilize this highly non-linear and non-unique inverse problem and provide only a single solution with no model uncertainty information, the method we use entirely avoids model regularization. The result of our approach is an ensemble of models that can be visualized and queried to provide meaningful information about the sensitivity of the data to the subsurface, and the level of resolution of model parameters. We represent models in 2-D using a Voronoi cell parametrization. To make the 2-D problem practical, we use a source-receiver common midpoint approximation with 1-D forward modelling. Our algorithm is transdimensional and self-parametrizing where the number of resistivity cells within a 2-D depth section is variable, as are their positions and geometries. Two synthetic studies demonstrate the algorithm's use in the appraisal of a thin, segmented, resistive reservoir which makes for a challenging exploration target. As a demonstration example, we apply our method to survey data collected over the Scarborough gas field on the Northwest Australian shelf.

  15. Acousto-exciton interaction in a gas of 2D indirect dipolar excitons in the presence of disorder

    NASA Astrophysics Data System (ADS)

    Kovalev, V. M.; Chaplik, A. V.

    2016-03-01

    A theory for the linear and quadratic responses of a 2D gas of indirect dipolar excitons to an external surface acoustic wave perturbation in the presence of a static random potential is considered. The theory is constructed both for high temperatures, definitely greater than the exciton gas condensation temperature, and at zero temperature by taking into account the Bose-Einstein condensation effects. The particle Green functions, the density-density correlation function, and the quadratic response function are calculated by the "cross" diagram technique. The results obtained are used to calculate the absorption of Rayleigh surface waves and the acoustic exciton gas drag by a Rayleigh wave. The damping of Bogoliubov excitations in an exciton condensate due to theirs scattering by a random potential has also been determined.

  16. Multiplex gas chromatography for use in space craft

    NASA Technical Reports Server (NTRS)

    Valentin, J. R.

    1985-01-01

    Gas chromatography is a powerful technique for the analysis of gaseous mixtures. Some limitations in this technique still exist which can be alleviated with multiplex gas chromatography (MGC). In MGC, rapid multiple sample injections are made into the column without having to wait for one determination to be finished before taking a new sample. The resulting data must then be reduced using computational methods such as cross correlation. In order to efficiently perform multiplexgas chromatography, experiments in the laboratory and on board future space craft, skills, equipment, and computer software were developed. Three new techniques for modulating, i.e., changing, sample concentrations were demonstrated by using desorption, decomposition, and catalytic modulators. In all of them, the need for a separate gas stream as the carrier was avoided by placing the modulator at the head of the column to directly modulate a sample stream. Finally, the analysis of an environmental sample by multiplex chromatography was accomplished by employing silver oxide to catalytically modulate methane in ambient air.

  17. Identification of volatiles from pineapple (Ananas comosus L.) pulp by comprehensive two-dimensional gas chromatography and gas chromatography/mass spectrometry.

    PubMed

    Pedroso, Marcio P; Ferreira, Ernesto C; Hantao, Leandro W; Bogusz, Stanislau; Augusto, Fabio

    2011-07-01

    Combining qualitative data from the chromatographic structure of 2-D gas chromatography with flame ionization detection (GC×GC-FID) and that from gas chromatography-mass spectrometry (GC/MS) should result in a more accurate assignment of the peak identities than the simple analysis by GC/MS, where coelution of analytes is unavoidable in highly complex samples (rendering spectra unsuitable for qualitative purposes) or for compounds in very low concentrations. Using data from GC×GC-FID combined with GC/MS can reveal coelutions that were not detected by mass spectra deconvolution software. In addition, some compounds can be identified according to the structure of the GC×GC-FID chromatogram. In this article, the volatile fractions of fresh and dehydrated pineapple pulp were evaluated. The extraction of the volatiles was performed by dynamic headspace extraction coupled to solid-phase microextraction (DHS-SPME), a technique appropriate for slurries or solid matrices. Extracted analytes were then analyzed by GC×GC-FID and GC/MS. The results obtained using both techniques were combined to improve compound identifications.

  18. 21 CFR 862.2250 - Gas liquid chromatography system for clinical use.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Gas liquid chromatography system for clinical use... Instruments § 862.2250 Gas liquid chromatography system for clinical use. (a) Identification. A gas liquid chromatography system for clinical use is a device intended to separate one or more drugs or compounds from...

  19. 21 CFR 862.2250 - Gas liquid chromatography system for clinical use.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Gas liquid chromatography system for clinical use... Instruments § 862.2250 Gas liquid chromatography system for clinical use. (a) Identification. A gas liquid chromatography system for clinical use is a device intended to separate one or more drugs or compounds from...

  20. 21 CFR 862.2250 - Gas liquid chromatography system for clinical use.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Gas liquid chromatography system for clinical use... Instruments § 862.2250 Gas liquid chromatography system for clinical use. (a) Identification. A gas liquid chromatography system for clinical use is a device intended to separate one or more drugs or compounds from...

  1. 21 CFR 862.2250 - Gas liquid chromatography system for clinical use.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Gas liquid chromatography system for clinical use... Instruments § 862.2250 Gas liquid chromatography system for clinical use. (a) Identification. A gas liquid chromatography system for clinical use is a device intended to separate one or more drugs or compounds from...

  2. 21 CFR 862.2250 - Gas liquid chromatography system for clinical use.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Gas liquid chromatography system for clinical use... Instruments § 862.2250 Gas liquid chromatography system for clinical use. (a) Identification. A gas liquid chromatography system for clinical use is a device intended to separate one or more drugs or compounds from...

  3. 2D Time-lapse Resistivity Monitoring of an Organic Produced Gas Plume in a Landfill using ERT.

    NASA Astrophysics Data System (ADS)

    Amaral, N. D.; Mendonça, C. A.; Doherty, R.

    2014-12-01

    This project has the objective to study a landfill located on the margins of Tietê River, in São Paulo, Brazil, using the electroresistivity tomography method (ERT). Due to huge organic matter concentrations in the São Paulo Basin quaternary sediments, there is subsurface depth related biogas accumulation (CH4 and CO2), induced by anaerobic degradation of the organic matter. 2D resistivity sections were obtained from a test area since March 2012, a total of 7 databases, being the last one dated from October 2013. The studied line has the length of 56m, the electrode interval is of 2m. In addition, there are two boreholes along the line (one with 3 electrodes and the other one with 2) in order to improve data quality and precision. The boreholes also have a multi-level sampling system that indicates the fluid (gas or water) presence in relation to depth. With our results it was possible to map the gas plume position and its area of extension in the sections as it is a positive resistivity anomaly, with the gas level having approximately 5m depth. With the time-lapse analysis (Matlab script) between the obtained 2D resistivity sections from the site, it was possible to map how the biogas volume and position change in the landfill in relation to time. Our preliminary results show a preferential gas pathway through the subsurface studied area. A consistent relation between the gas depth and obtained microbiological data from archea and bacteria population was also observed.

  4. A detailed postprocess analysis of an argon gas puff Z-pinch plasma using SPEC2D

    NASA Astrophysics Data System (ADS)

    Chong, Y. K.; Kammash, T.; Davis, J.

    1997-05-01

    A postprocess analysis of a single time frame hydrodynamic profile from the PRISM two-dimensional MHD simulation of an argon gas puff Z-pinch plasma experiment on Double-Eagle generator at Physics Internationals, Co. is presented. In addition, spatially resolved emission spectra and filtered (K- and L-shell radiation) x-ray pinhole images, generated using the SPEC2D code, are examined toward the understanding of the emission characteristics of the hot spots and the formation of the Rayleigh-Taylor instability in the plasma.

  5. Charge balancing in GaN-based 2-D electron gas devices employing an additional 2-D hole gas and its influence on dynamic behaviour of GaN-based heterostructure field effect transistors

    SciTech Connect

    Hahn, Herwig Reuters, Benjamin; Geipel, Sascha; Schauerte, Meike; Kalisch, Holger; Vescan, Andrei; Benkhelifa, Fouad; Ambacher, Oliver

    2015-03-14

    GaN-based heterostructure FETs (HFETs) featuring a 2-D electron gas (2DEG) can offer very attractive device performance for power-switching applications. This performance can be assessed by evaluation of the dynamic on-resistance R{sub on,dyn} vs. the breakdown voltage V{sub bd}. In literature, it has been shown that with a high V{sub bd}, R{sub on,dyn} is deteriorated. The impairment of R{sub on,dyn} is mainly driven by electron injection into surface, barrier, and buffer traps. Electron injection itself depends on the electric field which typically peaks at the gate edge towards the drain. A concept suitable to circumvent this issue is the charge-balancing concept which employs a 2-D hole gas (2DHG) on top of the 2DEG allowing for the electric field peak to be suppressed. Furthermore, the 2DEG concentration in the active channel cannot decrease by a change of the surface potential. Hence, beside an improvement in breakdown voltage, also an improvement in dynamic behaviour can be expected. Whereas the first aspect has already been demonstrated, the second one has not been under investigation so far. Hence, in this report, the effect of charge-balancing is discussed and its impact on the dynamic characteristics of HFETs is evaluated. It will be shown that with appropriate device design, the dynamic behaviour of HFETs can be improved by inserting an additional 2DHG.

  6. Subsurface Gas Flow and Ice Grain Acceleration within Enceladus and Europa Fissures: 2D DSMC Models

    NASA Astrophysics Data System (ADS)

    Tucker, O. J.; Combi, M. R.; Tenishev, V.

    2014-12-01

    The ejection of material from geysers is a ubiquitous occurrence on outer solar system bodies. Water vapor plumes have been observed emanating from the southern hemispheres of Enceladus and Europa (Hansen et al. 2011, Roth et al. 2014), and N2plumes carrying ice and ark particles on Triton (Soderblom et al. 2009). The gas and ice grain distributions in the Enceladus plume depend on the subsurface gas properties and the geometry of the fissures e.g., (Schmidt et al. 2008, Ingersoll et al. 2010). Of course the fissures can have complex geometries due to tidal stresses, melting, freezing etc., but directly sampled and inferred gas and grain properties for the plume (source rate, bulk velocity, terminal grain velocity) can be used to provide a basis to constrain characteristic dimensions of vent width and depth. We used a 2-dimensional Direct Simulation Monte Carlo (DSMC) technique to model venting from both axi-symmetric canyons with widths ~2 km and narrow jets with widths ~15-40 m. For all of our vent geometries, considered the water vapor source rates (1027­ - 1028 s-1) and bulk gas velocities (~330 - 670 m/s) obtained at the surface were consistent with inferred values obtained by fits of the data for the plume densities (1026 - 1028 s-1, 250 - 1000 m/s) respectively. However, when using the resulting DSMC gas distribution for the canyon geometries to integrate the trajectories of ice grains we found it insufficient to accelerate submicron ice grains to Enceladus' escape speed. On the other hand, the gas distributions in the jet like vents accelerated grains > 10 μm significantly above Enceladus' escape speed. It has been suggested that micron-sized grains are ejected from the vents with speeds comparable to the Enceladus escape speed. Here we report on these results including comparisons to results obtained from 1D models as well as discuss the implications of our plume model results. We also show preliminary results for similar considerations applied to Europa

  7. Characterization and quantification of humic substances 2D-Fluorescence by usage of extended size exclusion chromatography.

    PubMed

    Wagner, Martin; Schmidt, Wido; Imhof, Lutz; Grübel, Anika; Jähn, Camilla; Georgi, Denise; Petzoldt, Heike

    2016-04-15

    In this article, two methods for in-depth analysis of humic substances fluorescence are presented. The first one allows the combined analysis of fluorescence excitation-emission matrix (EEM) with chromatography technique. The main issue is the coupling of size exclusion chromatography (SEC) with spectroscopy by the use of an absorption and a fluorescence spectrometer as additional detectors. These allow a detailed characterization of humic substances depending on their molecular size, concentration and optical properties. For the evaluation of the resulting complex data, a model based on non-negative matrix factorization, which is also presented in this article, was developed. From the results of the examined humic substances standards, the second method was developed. It allows the characterization and quantification of humic substances fluorescence of a natural water sample solely on the basis of an excitation-emission matrix. The validation of the model is carried out within the framework of extensive analysis of real water samples.

  8. A Complete 2D Stability Analysis of Fast MHD Shocks in an Ideal Gas

    NASA Astrophysics Data System (ADS)

    Trakhinin, Yuri

    An algorithm of numerical testing of the uniform Lopatinski condition for linearized stability problems for 1-shocks is suggested. The algorithm is used for finding the domains of uniform stability, neutral stability, and instability of planar fast MHD shocks. A complete stability analysis of fast MHD shock waves is first carried out in two space dimensions for the case of an ideal gas. Main results are given for the adiabatic constant γ=5/3 (mono-atomic gas), that is most natural for the MHD model. The cases γ=7/5 (two-atomic gas) and γ>5/3 are briefly discussed. Not only the domains of instability and linear (in the usual sense) stability, but also the domains of uniform stability, for which a corresponding linearized stability problem satisfies the uniform Lopatinski condition, are numerically found for different given angles of inclination of the magnetic field behind the shock to the planar shock front. As is known, uniform linearized stability implies the nonlinear stability, that is local existence of discontinuous shock front solutions of a quasilinear system of hyperbolic conservation laws.

  9. Environmental analysis of present and future fuels in 2D simple model marine gas tubines

    NASA Astrophysics Data System (ADS)

    El Gohary, M. Morsy

    2013-12-01

    Increased worldwide concerns about fossil fuel costs and effects on the environment lead many governments and scientific societies to consider the hydrogen as the fuel of the future. Many researches have been made to assess the suitability of using the hydrogen gas as fuel for internal combustion engines and gas turbines; this suitability was assessed from several viewpoints including the combustion characteristics, the fuel production and storage and also the thermodynamic cycle changes with the application of hydrogen instead of ordinary fossil fuels. This paper introduces the basic environmental differences happening when changing the fuel of a marine gas turbine from marine diesel fuel to gaseous hydrogen for the same power output. Environmentally, the hydrogen is the best when the CO2 emissions are considered, zero carbon dioxide emissions can be theoretically attained. But when the NOx emissions are considered, the hydrogen is not the best based on the unit heat input. The hydrogen produces 270% more NOx than the diesel case without any control measures. This is primarily due to the increased air flow rate bringing more nitrogen into the combustion chamber and the increased combustion temperature (10% more than the diesel case). Efficient and of course expensive NOx control measures are a must to control these emissions levels.

  10. Quantum-dot systems prepared by 2D organization of nanoclusters preformed in the gas phase on functionalized substrates

    NASA Astrophysics Data System (ADS)

    Perez, A.; Bardotti, L.; Prevel, B.; Jensen, P.; Treilleux, M.; Mélinon, P.; Gierak, J.; Faini, G.; Mailly, D.

    2002-10-01

    The low-energy cluster beam deposition (LECBD) technique is used to deposit gold nanoclusters preformed in the gas phase on functionalized graphite substrates (highly oriented pyrolitic graphite (HOPG)), to prepare 2D-organized arrays of cluster assembled dots. Functionalized HOPG substrates are obtained using the focused ion beam (FIB) nanoengraving technique to pattern 2D-organized arrays of defects (nanoholes, nanobumps) which act as traps for the diffusing clusters. Depending on the deposition conditions (nature, size and fluence of the deposited clusters) and the functionalized substrates (nature and size of the FIB-induced defects, geometry of the 2D array of defects and temperature during deposition) high-quality quantum-dot arrays can be obtained with well controlled and reproducible morphologies. Kinetic Monte Carlo simulations of the cluster deposition experiments on functionalized substrates allow us to obtain quite good fits of the experimental images performed by tapping mode atomic force microscopy (TMAFM), leading to systematic investigations of the best conditions to realize high-quality quantum dots systems. This combined top-down-bottom-up approach (LECBD-FIB) seems a promising method for preparing high-integration-density devices (~Tbit cm-2) well suited for future applications to data storage, nanoelectronics, nano-optics, nanomagnetic systems.

  11. Pressure Tuning of First Dimension Columns in Comprehensive Two-Dimensional Gas Chromatography.

    PubMed

    Sharif, Khan M; Kulsing, Chadin; Marriott, Philip J

    2016-09-20

    The experimental approach and mechanism of pressure tuning (PT) are introduced for the first stage of a comprehensive two-dimensional gas chromatography (GC × GC) separation. The PT-GC × GC system incorporates a first dimension ((1)D) coupled column ensemble comprising a pair of (1)D columns ((1)D1 and (1)D2) connected via a microfluidic splitter device, allowing variable decompression of carrier gas across each (1)D column, and a conventional (2)D narrow bore column. By variation of junction pressure between the (1)D1 and (1)D2 columns, tunable total (1)D retentions of analytes are readily derived. Separations of a standard mixture comprising a number of different chemical classes (including alkanes, monoaromatics, alcohols, aldehydes, ketones, and esters) and Australian tea tree oil (TTO) were studied as practical examples of the PT-GC × GC system application. This illustrated the change of analyte retention time with experimental conditions depending on void time and retention on the different columns. In addition to void time change, variation of carrier gas relative decompression in the (1)D ensemble leads to tunable contribution of the (1)D1/(1)D2 columns that changes apparent polarity and selectivity of the ensemble. The resulting changes in (1)D elution order further altered elution temperature and thus retention of each analyte on the (2)D column in temperature-programmed GC × GC. 2D orthogonality measurements were then conducted to evaluate overall separation performance under application of different (1)D junction pressure. As a result, distribution and selectivity of particular target compounds, monoterpenes, sesquiterpenes, and oxygenated terpenes in 2D space, and thus orthogonality, could be adequately tuned. This indicates the potential of PT-GC × GC to be applicable for practical sample separation and provides a general approach to tune selectivity of target compounds.

  12. The determination of soil moisture by extraction and gas chromatography

    NASA Technical Reports Server (NTRS)

    Merek, E. L.; Carle, G. C.

    1974-01-01

    Soil moisture content was determined by extracting soil with methanol and subsequently analyzing the extract for water by gas chromatography. With air-dried mineral soils, this method gave slightly higher moisture content values than those obtained by the oven-dry method. Moisture content was determined quantitatively in soils to which various amounts of water had been added. The complete procedure, including extraction and analysis, requires less than one hour and gives results that closely compare to the oven-dry method.

  13. 2D fluid simulations of discharges at atmospheric pressure in reactive gas mixtures

    NASA Astrophysics Data System (ADS)

    Bourdon, Anne

    2015-09-01

    Since a few years, low-temperature atmospheric pressure discharges have received a considerable interest as they efficiently produce many reactive chemical species at a low energy cost. This potential is of great interest for a wide range of applications as plasma assisted combustion or biomedical applications. Then, in current simulations of atmospheric pressure discharges, there is the need to take into account detailed kinetic schemes. It is interesting to note that in some conditions, the kinetics of the discharge may play a role on the discharge dynamics itself. To illustrate this, we consider the case of the propagation of He-N2 discharges in long capillary tubes, studied for the development of medical devices for endoscopic applications. Simulation results put forward that the discharge dynamics and structure depend on the amount of N2 in the He-N2 mixture. In particular, as the amount of N2 admixture increases, the discharge propagation velocity in the tube increases, reaches a maximum for about 0 . 1 % of N2 and then decreases, in agreement with experiments. For applications as plasma assisted combustion with nanosecond repetitively pulsed discharges, there is the need to handle the very different timescales of the nanosecond discharge with the much longer (micro to millisecond) timescales of combustion processes. This is challenging from a computational point of view. It is also important to better understand the coupling of the plasma induced chemistry and the gas heating. To illustrate this, we present the simulation of the flame ignition in lean mixtures by a nanosecond pulsed discharge between two point electrodes. In particular, among the different discharge regimes of nanosecond repetitively pulsed discharges, a ``spark'' regime has been put forward in the experiments, with an ultra-fast local heating of the gas. For other discharge regimes, the gas heating is much weaker. We have simulated the nanosecond spark regime and have observed shock waves

  14. Chelate-modified polymers for atmospheric gas chromatography

    NASA Technical Reports Server (NTRS)

    Christensen, W. W.; Mayer, L. A.; Woeller, F. H. (Inventor)

    1980-01-01

    Chromatographic materials were developed to serve as the stationary phase of columns used in the separation of atmospheric gases. These materials consist of a crosslinked porous polymer matrix, e.g., a divinylbenzene polymer, into which has been embedded an inorganic complexed ion such as N,N'-ethylene-bis-(acetylacetoniminato)-cobalt (2). Organic nitrogenous bases, such as pyridine, may be incorporated into the chelate polymer complexes to increase their chromatographic utility. With such materials, the process of gas chromatography is greatly simplified, especially in terms of time and quantity of material needed for a gas separation.

  15. [Identification of narcotics in urine by capillary gas chromatography].

    PubMed

    Akalaev, A N; Shpagin, M G; Shabolenko, V P; Kovalenko, A E

    2004-01-01

    It is demonstrated that gas chromatography with quartz capillary columns (QCC) and with cross-sewn SE-52 by polysiloxane provides for the possibility to divide and identify, in human urine, 16 narcotic substances of the amphetamine, 1.4-benzodiazepine, morphine and other groups. The suggested extraction method makes it possible to isolate the above compounds from urine simultaneously and, after derivatization, to determine them by gas chromatography (GC) with programmed temperature within one stage analysis session. GC tests were performed on 2 both foreign and Russian QCC with SE-52. There is a description of 2 methods of how to obtain the trifluor-acetyl derivatives (TFA-derivatives) by using trifluor-acetate anhydride and N-methyl-bis-trifluor-acetamide. The limit of detecting the TFA-derivatives was 1-2 ng for the plasma-ionizing detector. The extraction method as well as the positive and negative aspects of using the TFA-derivatives are under discussion. The method of gas-chromatography/mass-spectrometry confirms that the positive results of radioreceptor assay are verified by GC in 92% of cases.

  16. Characterisation of odorants in roasted stem tea using gas chromatography-mass spectrometry and gas chromatography-olfactometry analysis.

    PubMed

    Sasaki, Tetsuya; Koshi, Erina; Take, Harumi; Michihata, Toshihide; Maruya, Masachika; Enomoto, Toshiki

    2017-04-01

    Roasted stem tea has a characteristic flavour, which is obtained by roasting tea stems, by-product of green tea production. This research aims to understand the characteristic odorants in roasted stem tea by comparing it to roasted leaf tea. We revealed potent odorants in commercial roasted stem tea using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry with aroma extract dilution analysis (AEDA). The difference between roasted stem and leaf tea derived from the same tea plants were investigated using GC-MS. Pyrazine compounds exhibited a roasted odour and high flavour dilution (FD) factors, as determined via AEDA. Roasted stem tea was richer in these pyrazines than roasted leaf tea. Geraniol and linalool exhibited high FD factors and a floral odour, and roasted stem tea was richer in these compounds than roasted leaf tea. These results may have a positive impact on the development of tea products.

  17. Pyrolysis-high resolution gas chromatography and pyrolysis gas chromatography-mass spectrometry of kerogens and kerogen precursors

    NASA Technical Reports Server (NTRS)

    Van De Meent, D.; Brown, S. C.; Philp, R. P.; Simoneit, B. R. T.

    1980-01-01

    A series of kerogens and kerogen precursors isolated from DSDP samples, oil shales and recent algal mats have been examined by Curie point pyrolysis-high resolution gas chromatography and gas chromatography-mass spectrometry. This study has shown that the three main types of kerogens (marine, terrestrial and mixtures of both) can be characterized using these techniques. The marine (algal) kerogens yield principally aliphatic products and the terrestrial kerogens yield more aromatic and phenolic products with some n-alkanes and n-alkenes. The yields of n-alkanes and n-alkenes increase and phenols decrease with increasing geologic age, however, pyrolysis-GC cannot be used to characterize the influence of short term diagenesis on the kerogen structure.

  18. Determination of Vinyl Chloride at ug/l. Level in Water by Gas Chromatography

    ERIC Educational Resources Information Center

    Bellar, Thomas A.; And Others

    1976-01-01

    A quantitative method for the determination of vinyl chloride in water is presented. Vinyl chloride is transfered to the gas phase by bubbling inert gas through the water. After concentration on silica gel or Carbosieve-B, determination is by gas chromatography. Confirmation of vinyl chloride is by gas chromatography-mass spectrometry. (Author/BT)

  19. ``SAFFMAN-TAYLOR'' Finger in 2d Parallel Viscous: BGK Lattice Gas Simulations

    NASA Astrophysics Data System (ADS)

    Salin, Dominique; Rakotomalala, Nicole; Watzky, Philippe

    1996-11-01

    We study the displacement of miscible fluids between two parallel plates for different values of the Peclet number Pe and of the viscosity ratio M. The full Navier-Stokes problem is addressed. We use the BGK lattice gas method, which is well suited for miscible fluids and allows to introduce molecular diffusion at the microscopic scale of the lattice. This numerical experiment leads to a symmetric concentration profile about the middle of the gap between the plates. At Pe numbers of the order of 1, mixing involves diffusion and advection in the flow direction. At large Pe, the fluids do not mix and an interface between them can be defined. Moreover, above M ~ 10, the interface becomes a well defined finger, the reduced width of which tends to λ_∞=0.56 at large values of M. Assuming that miscible fluids at high Pe numbers are similar to immiscible fluids at high capillary numbers, we find the analytical shape of the finger, using an extrapolation of the Reinelt-Saffman calculations for a Stokes immiscible flow. Surprisingly, the result is that our finger can be deduced from the celebrated Saffman-Taylor' s one, obtained in a potential flow, by a streching in the flow direction by a numerical factor of 2.125.

  20. Comparisons between tokamak fueling of gas puffing and supersonic molecular beam injection in 2D simulations

    SciTech Connect

    Zhou, Y. L.; Wang, Z. H.; Xu, X. Q.; Li, H. D.; Feng, H.; Sun, W. G.

    2015-01-09

    Plasma fueling with high efficiency and deep injection is very important to enable fusion power performance requirements. It is a powerful and efficient way to study neutral transport dynamics and find methods of improving the fueling performance by doing large scale simulations. Furthermore, two basic fueling methods, gas puffing (GP) and supersonic molecular beam injection (SMBI), are simulated and compared in realistic divertor geometry of the HL-2A tokamak with a newly developed module, named trans-neut, within the framework of BOUT++ boundary plasma turbulence code [Z. H. Wang et al., Nucl. Fusion 54, 043019 (2014)]. The physical model includes plasma density, heat and momentum transport equations along with neutral density, and momentum transport equations. In transport dynamics and profile evolutions of both plasma and neutrals are simulated and compared between GP and SMBI in both poloidal and radial directions, which are quite different from one and the other. It finds that the neutrals can penetrate about four centimeters inside the last closed (magnetic) flux surface during SMBI, while they are all deposited outside of the LCF during GP. Moreover, it is the radial convection and larger inflowing flux which lead to the deeper penetration depth of SMBI and higher fueling efficiency compared to GP.

  1. Comparisons between tokamak fueling of gas puffing and supersonic molecular beam injection in 2D simulations

    SciTech Connect

    Zhou, Y. L.; Wang, Z. H.; Xu, X. Q.; Li, H. D.; Feng, H.; Sun, W. G.

    2015-01-15

    Plasma fueling with high efficiency and deep injection is very important to enable fusion power performance requirements. It is a powerful and efficient way to study neutral transport dynamics and find methods of improving the fueling performance by doing large scale simulations. Two basic fueling methods, gas puffing (GP) and supersonic molecular beam injection (SMBI), are simulated and compared in realistic divertor geometry of the HL-2A tokamak with a newly developed module, named trans-neut, within the framework of BOUT++ boundary plasma turbulence code [Z. H. Wang et al., Nucl. Fusion 54, 043019 (2014)]. The physical model includes plasma density, heat and momentum transport equations along with neutral density, and momentum transport equations. Transport dynamics and profile evolutions of both plasma and neutrals are simulated and compared between GP and SMBI in both poloidal and radial directions, which are quite different from one and the other. It finds that the neutrals can penetrate about four centimeters inside the last closed (magnetic) flux surface during SMBI, while they are all deposited outside of the LCF during GP. It is the radial convection and larger inflowing flux which lead to the deeper penetration depth of SMBI and higher fueling efficiency compared to GP.

  2. Comparisons between tokamak fueling of gas puffing and supersonic molecular beam injection in 2D simulations

    DOE PAGES

    Zhou, Y. L.; Wang, Z. H.; Xu, X. Q.; ...

    2015-01-09

    Plasma fueling with high efficiency and deep injection is very important to enable fusion power performance requirements. It is a powerful and efficient way to study neutral transport dynamics and find methods of improving the fueling performance by doing large scale simulations. Furthermore, two basic fueling methods, gas puffing (GP) and supersonic molecular beam injection (SMBI), are simulated and compared in realistic divertor geometry of the HL-2A tokamak with a newly developed module, named trans-neut, within the framework of BOUT++ boundary plasma turbulence code [Z. H. Wang et al., Nucl. Fusion 54, 043019 (2014)]. The physical model includes plasma density,more » heat and momentum transport equations along with neutral density, and momentum transport equations. In transport dynamics and profile evolutions of both plasma and neutrals are simulated and compared between GP and SMBI in both poloidal and radial directions, which are quite different from one and the other. It finds that the neutrals can penetrate about four centimeters inside the last closed (magnetic) flux surface during SMBI, while they are all deposited outside of the LCF during GP. Moreover, it is the radial convection and larger inflowing flux which lead to the deeper penetration depth of SMBI and higher fueling efficiency compared to GP.« less

  3. Ultratrace detector for hand-held gas chromatography

    DOEpatents

    Andresen, Brian D.; Miller, Fred S.

    1999-01-01

    An ultratrace detector system for hand-held gas chromatography having high sensitivity, for example, to emissions generated during production of weapons, biological compounds, drugs, etc. The detector system is insensitive to water, air, helium, argon, oxygen, and C0.sub.2. The detector system is basically composed of a hand-held capillary gas chromatography (GC), an insulated heated redox-chamber, a detection chamber, and a vapor trap. For example, the detector system may use gas phase redox reactions and spectral absorption of mercury vapor. The gas chromatograph initially separates compounds that percolate through a bed of heated mercuric oxide (HgO) in a silica--or other metal--aerogel material which acts as an insulator. Compounds easily oxidized by HgO liberate atomic mercury that subsequently pass through a detection chamber which includes a detector cell, such as quartz, that is illuminated with a 254 nm ultra-violet (UV) mercury discharge lamp which generates the exact mercury absorption bands that are used to detect the liberated mercury atoms. Atomic mercury strongly absorbs 254 nm energy is therefore a specific signal for reducing compounds eluting from the capillary GC, whereafter the atomic mercury is trapped for example, in a silicon-aerogel trap.

  4. The Use of Gas Chromatography for Biogas Analysis

    NASA Astrophysics Data System (ADS)

    Andersen, Amanda; Seeley, John; Aurandt, Jennifer

    2010-04-01

    Energy from natural gas accounts for 24 percent of energy consumed in the US. Natural gas is a robust form of energy which is rich in methane content and is low in impurities. This quality suggests that it is a very clean and safe gas; it can be used in providing heat, a source for cooking, and in powering vehicles. The downside is that it is a non-renewable resource. On the contrary, methane rich gas that is produced by the breakdown of organic material in an anaerobic environment, called biogas, is a renewable energy source. This research focuses on the gas analysis portion of the creation of the anaerobic digestion and verification laboratory where content and forensic analysis of biogas is performed. Gas Chromatography is implemented as the optimal analytical tool for quantifying the components of the biogas including methane, carbon dioxide, hydrogen sulfide and siloxanes. In addition, the problems associated with the undesirable components are discussed. Anaerobic digestion of primary sludge has consistently produced about 55 percent methane; future goals of this research include studying different substrates to increase the methane yield and decrease levels of impurities in the gas.

  5. High-Throughput Gas Chromatography for Volatile Compounds Analysis by Fast Temperature Programming and Adsorption Chromatography.

    PubMed

    Gras, Ronda; Hua, Yujuan; Luong, Jim

    2017-03-20

    The synergy of combining fast temperature programming capability and adsorption chromatography using fused silica based porous layer open tubular columns to achieve high throughput chromatography for the separation of volatile compounds is presented.A gas chromatograph with built-in fast temperature programming capability and having a fast cool down rate was used as a platform. When these performance features were combined with the high degree of selectivity and strong retention characteristic of porous layer open tubular column technology, volatile compounds such as light hydrocarbons of up to C7 , primary alcohols, and mercaptans can be well separated and analyzed in a matter of minutes. This analytical approach substantially improves sample throughput by at least a factor of ten times when compared to published methodologies. In addition, the use of porous layer open tubular columns advantageously eliminates the need for costly and time-consuming cryogenic gas chromatography required for the separation of highly volatile compounds by partition chromatography with wall coated open tubular column technology.Relative standard deviations of retention time for model compounds such as alkanes from methane to hexane were found to be less than 0.3% (n = 10) and less than 0.5% for area counts for the compounds tested at two levels of concentration by manual injection, namely, 10 and 1000 ppm v/v (n = 10). Difficult separations were accomplished in one single analysis in less than 2 min such as the characterization of seventeen components in cracked gas containing alkanes, alkenes, dienes, branched hydrocarbons, and cyclic hydrocarbons. This article is protected by copyright. All rights reserved.

  6. Characterization of crude oils by inverse gas chromatography.

    PubMed

    Mutelet, F; Ekulu, G; Rogalski, M

    2002-09-06

    It was shown that the flocculation onset of asphaltenes in crude oils could be predicted on the basis of the inverse gas chromatography characterization of the crude oil properties. Hildebrand's solubility parameters of four crude oils were calculated from inverse chromatography data and compared with values obtained from the onset of asphaltene flocculation measurements. A good agreement was observed with three crude oils of different origin. A relation between Hildebrand's solubility parameter and linear solvation energy relationship descriptors was established and it was demonstrated that the solubility parameter of a crude oil is determined mainly with dispersion interactions and the hydrogen bond basicity. A large basicity lowers the oil solubility parameter, and increases its stability in respect to flocculation.

  7. MEMS Liquid and Gas Chromatography for Miniaturized Planetary In Situ Instruments

    NASA Astrophysics Data System (ADS)

    Kidd, R. D.; Bae, B.; Willis, P. A.; Noell, A. C.; Scianmarello, N.; Tai, Y.-C.

    2016-10-01

    Micro-Electro-Mechanical Systems (MEMS) technology to reduce the size, mass and power of the three classical chromatographic technologies: gas chromatography (GC), capillary electrophoresis (CE) and high performance liquid chromatography (HPLC).

  8. Determination of Free-Energy Relationships Using Gas Chromatography

    NASA Astrophysics Data System (ADS)

    Snow, Nicholas H.

    1996-06-01

    By performing a few straightforward analyses on a gas chromatograph, it is possible to calculate the free energy, enthalpy, and entropy changes that occur when a compound transfers between the mobile and stationary phases. The partition theory of chromatography allows this transfer to be expressed as a chemical equlibrium. By calculating the equilibrium constant for this reaction from chromatographic retention times, the standard free energy change may be determined, and from this, the standard enthalpy and entropy changes. Also, by calculating these values at several temperatures for structurally related compounds, it is possible to explore the relationship between chromatographic retention, standard free energy, and the structure of a compound. These calculations were performed for groups of homologous alcohols, acetates, and hydrocarbons on packed and capillary column gas chromatographs, using both polar and non-polar columns, and on computer simulation software. It is seen that for homologous compounds, the relationship between standard free energy change in partitioning and hydrocarbon chain length for this reaction is linear. It is also seen that gas chromatography represents a useful tool for the calculation and comparison of thermodynamic properties of compounds and that straightforward exercise of this type allows training of students in chromatographic analysis, basic partition theory, thermodynamic relationships, and linear free energy relationships.

  9. Offline coupling of high-speed counter-current chromatography and gas chromatography/mass spectrometry generates a two-dimensional plot of toxaphene components.

    PubMed

    Kapp, Thomas; Vetter, Walter

    2009-11-20

    High-speed counter-current chromatography (HSCCC), a separation technique based solely on the partitioning of solutes between two immiscible liquid phases, was applied for the fractionation of technical toxaphene, an organochlorine pesticide which consists of a complex mixture of structurally closely related compounds. A solvent system (n-hexane/methanol/water 34:24:1, v/v/v) was developed which allowed to separate compounds of technical toxaphene (CTTs) with excellent retention of the stationary phase (S(f) = 88%). Subsequent analysis of all HSCCC fractions by gas chromatography coupled to electron-capture negative ion mass spectrometry (GC/ECNI-MS) provided a wealth of information regarding separation characteristics of HSCCC and the composition of technical toxaphene. The visualization of the large amount of data obtained from the offline two-dimensional HSCCC-GC/ECNI-MS experiment was facilitated by the creation of a two-dimensional (2D) contour plot. The contour plot not only provided an excellent overview of the HSCCC separation progress, it also illustrated the differences in selectivity between HSCCC and GC. The results of this proof-of-concept study showed that the 2D chromatographic approach involving HSCCC facilitated the separation of CTTs that coelute in unidimensional GC. Furthermore, the creation of 2D contour plots may provide a useful means of enhancing data visualization for other offline two-dimensional separations.

  10. Analysis of beechwood creosote by gas chromatography-mass spectrometry and high-performance liquid chromatography.

    PubMed

    Ogata, N; Baba, T

    1989-12-01

    Compounds in beechwood creosote were analyzed by gas chromatography-mass spectrometry, and 22 major constituents were identified. Of these, 19 were phenolic compounds, i. e., guaiacol, phenol, two cresol isomers, four methylguaiacol (creosol) isomers, six xylenol isomers, two trimethylphenol isomers, 4-ethylguaiacol, 4-ethyl-5-methylguaiacol, and 4-propylguaiacol. The remaining three were hitherto unpredicted five-membered ring compounds, i. e., 3-methyl-2-hydroxy-2-cyclopenten-1-one, 3,5-dimethyl-2-hydroxy-2-cyclopenten-1-one, and 3-ethyl-2-hydroxy-2-cyclopenten-1-one. The relative quantities of these compounds were also compared with those obtained by high-resolution high-performance liquid chromatography. This report probably represents the first extensive analysis of beechwood creosote.

  11. Gas chromatography and high-performance liquid chromatography of natural steroids.

    PubMed

    Shimada, K; Mitamura, K; Higashi, T

    2001-11-23

    This review article underlines the importance of gas chromatography (GC), high-performance liquid chromatography (HPLC) and their hyphenated techniques using mass spectrometry (MS) for the determination of natural steroids, especially in human biological fluids. Steroids are divided into eight categories based on their structures and functions, and recent references using the above methodologies for the analysis of these steroids are cited. GC and GC-MS are commonly used for the determination of volatile steroids. Although HPLC is a widely used analytical method for the determination of steroids including the conjugated type in biological fluids, LC-MS is considered to be the most promising one for this purpose because of its sensitivity, specificity and versatility.

  12. Analysis and quantification of plant membrane lipids by thin-layer chromatography and gas chromatography.

    PubMed

    Wewer, Vera; Dörmann, Peter; Hölzl, Georg

    2013-01-01

    Galactolipids represent the predominant membrane lipid class in plants. In general, galactolipids are restricted to plastids, but during phosphate deficiency, they also accumulate in extraplastidial membranes. Two groups of plants can be distinguished based on the presence of a specific fatty acid, hexadecatrienoic acid (16:3), in chloroplast lipids. Plants that contain galactolipids with 16:3 acids are designated "16:3-plants"; the other group of plants which lack 16:3 contain mostly 18:3 in their galactolipids ("18:3-plants"). The methods in this chapter describe the extraction of membrane lipids from whole leaves, or from subcellular fractions, and their analysis via thin-layer chromatography (TLC) with different staining methods. Furthermore, a protocol for membrane lipid quantification is presented starting with the separation via TLC, transmethylation of the isolated lipids to fatty acid methyl esters, and their quantitative analysis via gas chromatography (GC).

  13. Multidimensional gas chromatography using microfluidic switching and low thermal mass gas chromatography for the characterization of targeted volatile organic compounds.

    PubMed

    Luong, J; Gras, R; Hawryluk, M; Shellie, R A; Cortes, H J

    2013-05-03

    Volatile organic compounds such as light hydrocarbons, dienes, and aromatic compounds are often encountered in the manufacturing and processing environments of chemical and petrochemical segments. These compounds need to be closely monitored for process optimization, plant maintenance and industrial hygiene purposes. A high throughput analytical approach has been successfully developed and implemented for the accurate measurement of fourteen commonly encountered analytes. The approach incorporates a recently introduced 5-port planar microfluidic device configured for use as a Deans switch for multidimensional gas chromatography. The use of multidimensional gas chromatography allows the elimination of potential chromatographic contaminants with a substantial enhancement of stationary phase selectivity via the use of columns with different separation mechanisms, and the back-flushing of heavier undesired hydrocarbons. A low thermal mass gas chromatographic module was employed in the second dimension of the two-dimensional gas chromatography system and was used to provide independent temperature control, and rapid heating and cooling to meet the high throughput requirements. By successfully combining these concepts, complete analysis of fourteen targeted components can be conducted in less than 120s. Repeatability of retention times for all compounds was found to be less than 0.05% (n=20). Repeatability of area counts at two levels, namely 10ppmv and 1000ppmv over a period of two days was found to be less than 3% (n=20). Apart from methane, which has a detection limit of 0.4ppmv, the rest of the compounds were found to have detection limits of less than 0.2ppmv. Compounds of interest were found to be linear over a range of 500ppbv-3000ppmv with correlation coefficients greater than 0.999.

  14. Gas-liquid chromatography in lunar organic analysis.

    NASA Technical Reports Server (NTRS)

    Gehrke, C. W.

    1972-01-01

    Gas-liquid chromatography (GLC) is a powerful and sensitive method for the separation and detection of organic compounds at nanogram levels. The primary requirement for successful analyses is that the compounds of interest must be volatile under the chromatographic conditions employed. Nonvolatile organic compounds must be converted to volatile derivatives prior to analysis. The derivatives of choice must be both amenable to chromatographic separation and be relatively stable. The condition of volatility necessitates the development of efficient derivatization reactions for important groups of compounds as amino acids, carbohydrates, nucleosides, etc. Trimethylsilylation and trifluoroacetylation represent specific areas of recent prominence. Some relevant practical aspects of GLC are discussed.

  15. Capillary gas chromatography with two new moderately high temperature phases.

    NASA Technical Reports Server (NTRS)

    Pollock, G. E.

    1972-01-01

    Gas chromatography test results are presented for two new moderately high-temperature phases of Dexsil 400-GC with free hydroxyl end groups (uncapped) and with end groups covered by trimethyl silyl groups (capped). The two Dexsil 400-GC phases were tested for their ability to resolve N-TFA-DL-(+)-2-butyl esters and n-butyl esters, as well as fatty acid methyl esters and hydrocarbon standards. Generally the more polar uncapped phase was superior to the capped phase in all separation comparisons, except for the hydrocarbons.

  16. Thermal History Of PMRs Via Pyrolysis-Gas Chromatography

    NASA Technical Reports Server (NTRS)

    Gluyas, Richard E.; Alston, William B.; Snyder, William J.

    1994-01-01

    Pyrolysis-gas chromatography (PY-GC) useful as analytical technique to determine extents of cure or postcure of PMR-15 polyimides and to lesser extent, cumulative thermal histories of PMR-15 polyimides exposed to high temperatures. Also applicable for same purposes to other PMR polyimides and to composite materials containing PMR polyimides. Valuable in reducing costs and promoting safety in aircraft industry by helping to identify improperly cured or postcured PMR-15 composite engine and airframe components and helping to identify composite parts nearing ends of their useful lives.

  17. Continuous monitoring of a changing sample by multiplex gas chromatography

    NASA Technical Reports Server (NTRS)

    Valentin, Jose R.; Hall, Kirsten W.; Becker, Joseph F.

    1990-01-01

    Results are presented from a study in which a continuously changed gaseous sample was monitored by multiplex gas chromatography (MGC), using the exponential dilution (ED) technique of Ritter and Adams (1976) to change the composition and concentration of a gaseous mixture in such a way as to imitate changes in the atmospheric gases sampled by a descending aircraft. A calibration of the MGC system was performed with four different rates of sample dilution, and the errors resulting from various degrees of change in the sample concentration were determined.

  18. New insights in the velocity dependency of the external mass transfer coefficient in 2D and 3D porous media for liquid chromatography.

    PubMed

    Deridder, Sander; Desmet, Gert

    2012-03-02

    Numerical calculations of the mobile zone mass transfer rate in a variety of ordered 2D and 3D structures are presented. These calculations are in line with earlier theoretical and experimental findings made in the field of chemical engineering and suggest that the Sherwood-number (Sh(m)) appearing in the mobile phase mass transfer term of the general plate height expression of liquid chromatography is not correctly predicted by the Wilson-Geankoplis--or the Kataoka--or the penetration model expression that have been used up to now to in the field of LC, and that at least more research is needed before these expressions can be continued to be used with confidence. The aforementioned expressions were obtained by neglecting the effect of axial dispersion on the mass transfer process, and it seems that they therefore underestimate the true Sh(m)-number by a factor of 2-5 around the minimum of the van Deemter-curve. New correlations describing the variation of the Sh(m)-coefficient as a function of the reduced velocity for a number of other packing geometries (tetrahedral monolith, 2D pillar array) are proposed. These correlations are in agreement with earlier theoretical and experimental studies showing that at low velocities the local-driving force-based Sh(m)-value is of the order of 10-20 in a packed bed column with an external porosity on the order of 35-40%.

  19. 2D fluid model analysis for the effect of 3D gas flow on a capacitively coupled plasma deposition reactor

    NASA Astrophysics Data System (ADS)

    Kim, Ho Jun; Lee, Hae June

    2016-06-01

    The wide applicability of capacitively coupled plasma (CCP) deposition has increased the interest in developing comprehensive numerical models, but CCP imposes a tremendous computational cost when conducting a transient analysis in a three-dimensional (3D) model which reflects the real geometry of reactors. In particular, the detailed flow features of reactive gases induced by 3D geometric effects need to be considered for the precise calculation of radical distribution of reactive species. Thus, an alternative inclusive method for the numerical simulation of CCP deposition is proposed to simulate a two-dimensional (2D) CCP model based on the 3D gas flow results by simulating flow, temperature, and species fields in a 3D space at first without calculating the plasma chemistry. A numerical study of a cylindrical showerhead-electrode CCP reactor was conducted for particular cases of SiH4/NH3/N2/He gas mixture to deposit a hydrogenated silicon nitride (SiN x H y ) film. The proposed methodology produces numerical results for a 300 mm wafer deposition reactor which agree very well with the deposition rate profile measured experimentally along the wafer radius.

  20. Characterization of complex phthalic acid/propylene glycol based polyesters by the combination of 2D chromatography and MALDI-TOF mass spectrometry.

    PubMed

    Pretorius, Nadine O; Rhode, Karsten; Simpson, Jaylin M; Pasch, Harald

    2015-01-01

    The combination of gradient HPLC, 2D chromatography, and MALDI-TOF MS facilitated the analysis of the various distributions of phthalic acid/propylene glycol-based model polyesters. Investigations of kinetic samples taken at various reaction times highlighted the subsequent differences at various stages of the polyesterification reaction in terms of molecular weight, chemical composition, and endgroups. Normal-phase gradient-HPLC analysis successfully enabled an oligomeric separation of the respective samples. Peak-splitting behavior in early eluting peaks suggested that the separation was affected by a combination of factors and not solely based on chemical composition, functionality type or degree of polycondensation. Two-dimensional chromatography provided the link between chemical composition and molecular weight distribution, confirming that the first dimension gradient HPLC separation was based on chemical composition with increasing degree of oligomerization in the second dimension. The off-line coupling of LAC with MALDI-TOF MS provided structural details in combination with improved molecular weight determination of the more homogeneous LC fractions. The study indicated that all aspects related to the model saturated anhydride system should be considered in the case of copolyester synthesis to produce industrial type polyester resins. It was shown that the present multidimensional approach provided most comprehensive structural information on the polyester system.

  1. Warm ionized gas in CALIFA early-type galaxies. 2D emission-line patterns and kinematics for 32 galaxies

    NASA Astrophysics Data System (ADS)

    Gomes, J. M.; Papaderos, P.; Kehrig, C.; Vílchez, J. M.; Lehnert, M. D.; Sánchez, S. F.; Ziegler, B.; Breda, I.; Dos Reis, S. N.; Iglesias-Páramo, J.; Bland-Hawthorn, J.; Galbany, L.; Bomans, D. J.; Rosales-Ortega, F. F.; Cid Fernandes, R.; Walcher, C. J.; Falcón-Barroso, J.; García-Benito, R.; Márquez, I.; Del Olmo, A.; Masegosa, J.; Mollá, M.; Marino, R. A.; González Delgado, R. M.; López-Sánchez, Á. R.; CALIFA Collaboration

    2016-04-01

    Context. The morphological, spectroscopic, and kinematical properties of the warm interstellar medium (wim) in early-type galaxies (ETGs) hold key observational constraints to nuclear activity and the buildup history of these massive, quiescent systems. High-quality integral field spectroscopy (IFS) data with a wide spectral and spatial coverage, such as those from the CALIFA survey, offer an unprecedented opportunity for advancing our understanding of the wim in ETGs. Aims: This article centers on a 2D investigation of the wim component in 32 nearby (≲150 Mpc) ETGs from CALIFA, complementing a previous 1D analysis of the same sample. Methods: The analysis presented here includes Hα intensity and equivalent width (EW) maps and radial profiles, diagnostic emission-line ratios, and ionized-gas and stellar kinematics. It is supplemented by τ-ratio maps, which are a more efficient means to quantify the role of photoionization by the post-AGB stellar component than alternative mechanisms (e.g., AGN, low-level star formation). Results: Confirming and strengthening our previous conclusions, we find that ETGs span a broad continuous sequence in the properties of their wim, exemplified by two characteristic classes. The first (type i) comprises systems with a nearly constant EW(Hα) in their extranuclear component, which quantitatively agrees with (but is no proof of) the hypothesis that photoionization by the post-AGB stellar component is the main driver of extended wim emission. The second class (type ii) stands for virtually wim-evacuated ETGs with a very low (≤0.5 Å), outwardly increasing EW(Hα). These two classes appear indistinguishable from one another by their LINER-specific emission-line ratios in their extranuclear component. Here we extend the tentative classification we proposed previously by the type i+, which is assigned to a subset of type i ETGs exhibiting ongoing low-level star-forming activity in their periphery. This finding along with faint

  2. High performance mini-gas chromatography-flame ionization detector system based on micro gas chromatography column

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaofeng; Sun, Jianhai; Ning, Zhanwu; Zhang, Yanni; Liu, Jinhua

    2016-04-01

    Monitoring Volatile organic compounds (VOCs) was a very important measure for preventing environmental pollution, therefore, a mini gas chromatography (GC) flame ionization detector (FID) system integrated with a mini H2 generator and a micro GC column was developed for environmental VOC monitoring. In addition, the mini H2 generator was able to make the system explode from far away due to the abandoned use of a high pressure H2 source. The experimental result indicates that the fabricated mini GC FID system demonstrated high repeatability and very good linear response, and was able to rapidly monitor complicated environmental VOC samples.

  3. Measurement of carboxyhaemoglobin by spectrophotometry and gas chromatography.

    PubMed

    Johansson, M B; Wollmer, P

    1989-12-01

    The purpose of this study was to evaluate state-of-the-art spectrophotometry for measurement of carboxyhaemoglobin (COHb). We measured the fractional concentration of COHb in 109 blood samples from patients under investigation of anaemia or with exposure to carbon monoxide (smokers) with the OSM3 Hemoximeter and by gas chromatography. Duplicate measurements were made with both methods in 42 samples. We found only a trivial systematic difference between the two methods. There was, however, a considerable scatter of the measurements, the limits of agreement (95% confidence limits for the difference between the two methods) being -0.98 and 0.86% COHb. The poor agreement between the methods was largely explained by a large random scatter in duplicate spectrophotometric measurements, whereas the method based on gas chromatography was highly reproducible. We conclude that the low accuracy of spectrophotometric measurements of COHb precludes its use for assessment of the endogenous production of CO, but that it may be useful for assessment of exposure to exogenous CO.

  4. Novel stationary phases based on asphaltenes for gas chromatography.

    PubMed

    Boczkaj, Grzegorz; Momotko, Malwina; Chruszczyk, Dorota; Przyjazny, Andrzej; Kamiński, Marian

    2016-07-01

    We present the results of investigations on the possibility of the application of the asphaltene fraction isolated from the oxidized residue from vacuum distillation of crude oil as a stationary phase for gas chromatography. The results of the investigation revealed that the asphaltene stationary phases can find use for the separation of a wide range of volatile organic compounds. The experimental values of Rohrschneider/McReynolds constants characterize the asphaltenes as stationary phases of medium polarity and selectivity similar to commercially available phases based on alkyl phthalates. Isolation of asphaltenes from the material obtained under controlled process conditions allows the production of a stationary phase having reproducible sorption properties and chromatographic columns having the same selectivity. Unique selectivity and high thermal stability make asphaltenes attractive as a material for stationary phases for gas chromatography. A low production cost from a readily available raw material (oxidized petroleum bitumens) is an important economic factor in case of application of the asphaltene stationary phases for preparative and process separations.

  5. Identification of polychlorinated styrene compounds in heron tissues by gas-liquid chromatography-mass spectrometry.

    PubMed

    Reichel, W L; Prouty, R M; Gay, M L

    1977-01-01

    Unknown compounds detected in Ardea herodias tissues are identified by gas-liquid chromatography-mass spectrometry as residues of octachlorostyrene. Heptachlorostyrene and hexachlorostyrene were tentatively identified.

  6. Identification of polychlorinated styrene compounds in heron tissues by gas-liquid chromatography-mass spectrometry

    USGS Publications Warehouse

    Reichel, W.L.; Prouty, R.M.; Gay, M.L.

    1977-01-01

    Unknown compounds detected in Ardea herodias tissues are identified by gas-liquid chromatography-mass spectrometry as residues of octachlorostyrene. Heptachlorostyrene and hexachlorostyrene were tentatively identified.

  7. 2D multinuclear NMR, hyperpolarized xenon and gas storage in organosilica nanochannels with crystalline order in the walls.

    PubMed

    Comotti, Angiolina; Bracco, Silvia; Valsesia, Patrizia; Ferretti, Lisa; Sozzani, Piero

    2007-07-11

    The combination of 2D 1H-13C and 1H-29Si solid state NMR, hyperpolarized 129Xe NMR, synchrotron X-ray diffraction, together with adsorption measurements of vapors and gases for environmental and energetic relevance, was used to investigate the structure and the properties of periodic mesoporous hybrid p-phenylenesilica endowed with crystalline order in the walls. The interplay of 1H, 13C, and 29Si in the 2D heteronuclear correlation NMR measurements, together with the application of Lee-Goldburg homonuclear decoupling, revealed the spatial relationships (<5 angstroms) among various spin-active nuclei of the framework. Indeed, the through-space correlations in the 2D experiments evidenced, for the first time, the interfaces of the matrix walls with guest molecules confined in the nanochannels. Organic-inorganic and organic-organic heterogeneous interfaces between the matrix and the guests were identified. The open-pore structure and the easy accessibility of the nanochannels to the gas phase have been demonstrated by highly sensitive hyperpolarized (HP) xenon NMR, under extreme xenon dilution. Two-dimensional exchange experiments showed the exchange time to be as short as 2 ms. Through variable-temperature HP 129Xe NMR experiments we were able to achieve an unprecedented description of the nanochannel space and surface, a physisorption energy of 13.9 kJ mol-1, and the chemical shift value of xenon probing the internal surfaces. These results prompted us to measure the high storage capacity of the matrix towards benzene, hexafluorobenzene, ethanol, and carbon dioxide. Both host-guest, CH...pi, and OH...pi interactions contribute to the stabilization of the aromatic guests (benzene and hexafluorobenzene) on the extended surfaces. The full carbon dioxide loading in the channels could be detected by synchrotron radiation X-ray diffraction experiments. The selective adsorption of carbon dioxide (ca. 90 wt %) vs that of oxygen and hydrogen, together with the permanent

  8. Chemical discrimination in turbulent gas mixtures with MOX sensors validated by gas chromatography-mass spectrometry.

    PubMed

    Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

    2014-10-16

    Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance.

  9. Photogalvanic effects originating from the violation of the Einstein relation in a 2D electron gas in high Landau levels

    NASA Astrophysics Data System (ADS)

    Dmitriev, Ivan

    2010-03-01

    This talk will present a quantum kinetic theory [1] of the microwave-induced photocurrent and photovoltage magnetooscillations emerging in a spatially nonuniform 2D electron system in the absence of external dc driving [2]. It will show that in an irradiated sample the Landau quantization leads to violation of the Einstein relation between the dc conductivity and diffusion coefficient. Then, in the presence of a built-in electric field in a sample, the microwave illumination causes photo-galvanic signals which oscillate as a function of magnetic field as observed in the experiment. The discussed effects should also play an essential role for the transport in the zero resistance states where the system breaks into current domains and peculiarities of the transport properties of the inhomogeneous system become of central importance.[1] I. A. Dmitriev, S. I. Dorozhkin, and A. D. Mirlin, ``Theory of microwave-induced photocurrent and photovoltage magneto-oscillations in a spatially nonuniform two-dimensional electron gas '', Phys. Rev. B 80, 125418 (2009).[2] S. I. Dorozhkin, I. V. Pechenezhskiy, L. N. Pfeiffer, K. W. West, V. Umansky, K. von Klitzing, and J. H. Smet, ``Photocurrent and Photovoltage Oscillations in the Two-Dimensional Electron System: Enhancement and Suppression of Built-In Electric Fields'', Phys. Rev.Lett. 102, 036602 (2009).

  10. Bcs-Bose Crossover Picture for a 2d Electron Gas with a Finite-Range Attractive Interfermion Interaction

    NASA Astrophysics Data System (ADS)

    Solís, Miguel A.; Sevilla, Francisco J.; Fortes, Mauricio; de Llano, Manuel

    2002-03-01

    Cooper pair formation is studied in a 2D electron gas interacting pairwise through a finite-range, separable interfermion potential in wavevector space V_ kk^' =-(v_0/L^2)g_kg_k^' , where L^2 is the system area, v0 >= 0 the interaction strength, g_k≡ (1+k^2/k_0^2)-1/2 with k0 the inverse interaction range. The interaction strength v0 is eliminated [1] in favor of the (positive) binding energy B2 of an electron pair in vacuum under the same interfermion interaction. For finite range, i.e., 1/k_0>0, we report numerical calculations of the gap, the critical temperature and the chemical potential as functions of B2 and 1/k_0. For k_0= ∞ or zero-range (viz., a delta potential well) we recover at T=0 the well-known Miyake [2] results. Finally, the gap-to-Tc ratio is exhibited as a function of B2 and compared with other calculations as well as with empirical values for cuprate superconductors. [1] S.K. Adhikari, M. Casas, A. Puente, A. Rigo, M. Fortes, M.A. Solís, M. de Llano, A.A. Valladares and O. Rojo, Phys. Rev. B 62, 8671 (2000). [2] K. Miyake, Prog. Theor. Phys. 69, 1794 (1983). We thank UNAM-DGAPA-PAPIIT # IN102198 and CONACyT # 27828E for partial support.

  11. Spin-Orbit Interaction in High-κ Dielectric Gated Rashba-2D Electron Gas and Mesoscopic Rings

    NASA Astrophysics Data System (ADS)

    Dai, Yanhua; Yuan, Zhuoquan; Stone, Kristjan; Du, Rui-Rui; Xu, Min; Ye, Peide

    2008-03-01

    There is increasing current interest in the quantum interference effect in mesoscopic devices fabricated on a Rashba-2D electron gas (2DEG), where the spin-orbit interaction parameters can be tuned by a potential gate. We explore ring structures that use a gate consisting of thin (5nm-50nm) high-κ dielectric Al2O3 or HfO2 layer and nano-patterned metals. The 2DEG is provided by lattice-matched In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As quantum wells that have a typical electron density n of 1.5x10^12/cm^2 and mobility μ>=2x10^4cm^2/Vs. The dielectric material was grown by atomic layer deposition. We will present the gate characteristics of Hall bars as well as magnetic transport data from gated mesoscopic rings. The work at Rice is funded by NSF DMR-0706634. Reference: M. Konig et al, Phys. Rev. Lett. 96, 076804 (2006); T. Bergsten et al, Phys. Rev. Lett. 97, 196803 (2006); B. Grbic et al, Phys. Rev. Lett. 99, 176803 (2007).

  12. Qualitative analysis of Copaifera oleoresin using comprehensive two-dimensional gas chromatography and gas chromatography with classical and cold electron ionisation mass spectrometry.

    PubMed

    Wong, Yong Foo; Uekane, Thais M; Rezende, Claudia M; Bizzo, Humberto R; Marriott, Philip J

    2016-12-16

    Improved separation of both sesquiterpenes and diterpenic acids in Copaifera multijuga Hayne oleoresin, is demonstrated by using comprehensive two-dimensional gas chromatography (GC×GC) coupled to accurate mass time-of-flight mass spectrometry (accTOFMS). GC×GC separation employs polar phases (including ionic liquid phases) as the first dimension ((1)D) column, combined with a lower polarity (2)D phase. Elution temperatures (Te) of diterpenic acids (in methyl ester form, DAME) increased as the (1)D McReynolds' polarity value of the column phase decreased. Since Te of sesquiterpene hydrocarbons decreased with increased polarity, the very polar SLB-IL111 (1)D phase leads to excessive peak broadening in the (2)D apolar phase due to increased second dimension retention ((2)tR). The combination of SLB-IL59 with a nonpolar column phase was selected, providing reasonable separation and low Te for sesquiterpenes and DAME, compared to other tested column sets, without excessive (2)tR. Identities of DAME were aided by both soft (30eV) electron ionisation (EI) accurate mass TOFMS analysis and supersonic molecular beam ionisation (cold EI) TOFMS, both which providing less fragmentation and increased relative abundance of molecular ions. The inter-relation between EI energies, emission current, signal-to-noise and mass error for the accurate mass measurement of DAME are reported. These approaches can be used as a basis for conducting of GC×GC with soft EI accurate mass measurement of terpenes, particularly for unknown phytochemicals.

  13. Microfabricated planar glass gas chromatography with photoionization detection.

    PubMed

    Lewis, Alastair C; Hamilton, Jacqueline F; Rhodes, Christopher N; Halliday, Jaydene; Bartle, Keith D; Homewood, Philip; Grenfell, Robin J P; Goody, Brian; Harling, Alice M; Brewer, Paul; Vargha, Gergely; Milton, Martin J T

    2010-01-29

    We report the development of a microfabricated gas chromatography system suitable for the separation of volatile organic compounds (VOCs) and compatible with use as a portable measurement device. Hydrofluoric acid etching of 95x95mm Schott B270 wafers has been used to give symmetrical hemi-spherical channels within a glass substrate. Two matching glass plates were subsequently cold bonded with the channels aligned; the flatness of the glass surfaces resulted in strong bonding through van der Waals forces. The device comprised gas fluidic interconnections, injection zone and 7.5 and 1.4m long, 320microm internal diameter capillaries. Optical microscopy confirmed the capillaries to have fully circular channel profiles. Direct column heating and cooling could be achieved using a combination of resistive heaters and Peltier devices. The low thermal conductivity of glass allowed for multiple uniform temperature zones to be achieved within a single glass chip. Temperature control over the range 10-200 degrees C was achieved with peak power demand of approximately 25W. The 7.5m capillary column was static coated with a 2microm film of non-polar dimethylpolysiloxane stationary phase. A standard FID and a modified lightweight 100mW photoionization detector (PID) were coupled to the column and performance tested with gas mixtures of monoaromatic and monoterpene species at the parts per million concentration level. The low power GC-PID device showed good performance for a small set of VOCs and sub ng detection sensitivity to monoaromatics.

  14. Possibility of diagnosing meningitis by gas chromatography: cryptococcal meningitis.

    PubMed Central

    Schlossberg, D; Brooks, J B; Shulman, J

    1976-01-01

    Cerebrospinal fluid (CSF) from eight patients with cryptococcal meningitis, from ten patients with viral meningitis, and from four control patients without meningitis were analyzed by electron-capture gas-liquid chromatography (EC-GLC). All cryptococcal specimens had similar EC-GLC profiles, and these differed from those of the controls. Viral EC-GLC patterns were different from those obtained with specimens from the patients with cryptococcal infection and from the controls. In addition, specimens from patients with various types of viral infections gave profiles that differed from each other. Two normal CSFs were inoculated with Cryptococcus neoformans; aliquots of these cultures showed an EC-GLC pattern very similar to that seen in CSF of patients with cryptococcal meningitis. The EC-GLC procedure is rapid, reproducible, and easy to perform and may hold promise as an additional aid in the diagnosis of cryptococcal infection. PMID:773956

  15. Low thermal mass gas chromatography: principles and applications.

    PubMed

    Luong, Jim; Gras, Ronda; Mustacich, Robert; Cortes, Hernan

    2006-01-01

    In gas chromatography (GC), temperature programming is often considered to be the second most important parameter to control, the first being column selectivity. A radically new GC technology to achieve ultrafast temperature programming with an unprecedented cool down time and low power consumption has recently become available. This technology is referred to as low thermal mass GC (LTMGC). Though the technology has its roots in resistive heating, which forms the basis of principle and design concept, the approach taken to achieve ultrafast heating and cool down time by LTMGC represents a significant break-through in GC. Despite some rectifiable shortcomings, LTMGC has proven to be an ideal methodology to deliver near/real time GC data, high precision, and high throughput applications. It is a new approach for modern high-speed GC. This paper documents the fundamental design principles behind LTMGC, performance data, and examples of applications investigated.

  16. Design, testing, and simulation of microscale gas chromatography columns

    SciTech Connect

    Hudson, M.L.; Kottenstette, R.; Matzke, C.M.; Frye-Mason, G.C.; Shollenberger, K.A.; Adkins, D.R.; Wong, C.C.

    1998-08-01

    A microscale gas chromatography column is one component in a microscale chemistry laboratory for detecting chemical agents. Several columns were fabricated using the Bosch etch process which allows deep, high aspect ratio channels of rectangular cross-section. A design tool, based on analytical models, was developed to evaluate the effects of operating conditions and column specifications on separation resolution and time. The effects of slip flow, channel configuration, and cross-sectional shape were included to evaluate the differences between conventional round, straight columns and the microscale rectangular, spiral columns. Experimental data were obtained and compared with the predicted flowrates and theoretical number of plates. The design tool was then employed to select more optimum channel dimensions and operating conditions for high resolution separations.

  17. Field gas chromatography-mass spectrometry for fast analysis.

    PubMed

    Makas, Alexei L; Troshkov, Mikhail L

    2004-02-05

    The objective of this presentation is to demonstrate the original device and procedure for fast gas chromatography-mass spectrometry (GC-MS) analysis of gaseous and liquid samples and to discuss its features and capabilities. The concept was developed in order to expand the range of compounds suitable for GC separation and to reduce the time of analysis. Field GC-MS, consisting of original "concentrator-thermodesorber" (CTD) unit, multiple module GC system and compact magnetic mass spectrometer with powerful two-stage vacuum system and multicollector ion detector, is represented. The whole weight of the device is 90 kg. Power consumption is 250 W. The device and analytical procedures allow high speed screening of toxic substances in air and extracts within 100 s per sample. The examples of applications are described, including fast screening of tributyl phosphate (TBP) in air at low ppt level at the rate 1 sample/min.

  18. A simple parallel gas chromatography column screening system.

    PubMed

    Schafer, Wes; Hamilton, Simon E; Pirzada, Zainab; Welch, Christopher J

    2012-01-01

    A simple approach to the automated screening of four different columns on a single gas chromatography (GC) instrument is used for rapid chiral GC method development. Configuration of a conventional GC instrument with a second autosampler and several inexpensive Y-splitters enables simultaneous evaluation of two different columns, allowing a total of four different columns to be evaluated in two automated back to back runs. The resulting system affords a simple and effective approach to chiral GC method development that speeds analysis while eliminating the need for slow and tedious manual interchange of columns. An example of developing a rapid isothermal GC method from the screening results obtained by the instrument is also shown.

  19. Hansen solubility parameters for polyethylene glycols by inverse gas chromatography.

    PubMed

    Adamska, Katarzyna; Voelkel, Adam

    2006-11-03

    Inverse gas chromatography (IGC) has been applied to determine solubility parameter and its components for nonionic surfactants--polyethylene glycols (PEG) of different molecular weight. Flory-Huggins interaction parameter (chi) and solubility parameter (delta(2)) were calculated according to DiPaola-Baranyi and Guillet method from experimentally collected retention data for the series of carefully selected test solutes. The Hansen's three-dimensional solubility parameters concept was applied to determine components (delta(d), delta(p), delta(h)) of corrected solubility parameter (delta(T)). The molecular weight and temperature of measurement influence the solubility parameter data, estimated from the slope, intercept and total solubility parameter. The solubility parameters calculated from the intercept are lower than those calculated from the slope. Temperature and structural dependences of the entopic factor (chi(S)) are presented and discussed.

  20. Quantification of antidepressants using gas chromatography-mass spectrometry.

    PubMed

    Winecker, Ruth E

    2010-01-01

    Antidepressants are of great interest to clinical and forensic toxicologists as they are frequently used in suicidal gestures; they can be the source of drug interactions and some have narrow therapeutic indices making the potential for toxicity more likely. There are five categories of antidepressants based on function and/or structure. These are monoamine oxidase inhibitors (MAOI), cyclic antidepressants including tricyclic and tetracyclic compounds (TCA), selective serotonin reuptake inhibitors (SSRI), serotonin-norepinephrine reuptake inhibitors (SNRI), and atypical compounds. This method is designed to detect the presence of antidepressant drugs in blood/serum, urine, and tissue specimens using gas chromatography/mass spectrometry (GC/MS) following liquid-liquid extraction (LLE) and identified by relative retention times and mass spectra.

  1. c2d Spitzer IRS spectra of embedded low-mass young stars: gas-phase emission lines

    NASA Astrophysics Data System (ADS)

    Lahuis, F.; van Dishoeck, E. F.; Jørgensen, J. K.; Blake, G. A.; Evans, N. J.

    2010-09-01

    Context. A survey of mid-infrared gas-phase emission lines of H2, H2O and various atoms toward a sample of 43 embedded low-mass young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer “Cores to Disks” (c2d) legacy program. Aims: The environment of embedded protostars is complex both in its physical structure (envelopes, outflows, jets, protostellar disks) and the physical processes (accretion, irradiation by UV and/or X-rays, excitation through slow and fast shocks) which take place. The mid-IR spectral range hosts a suite of diagnostic lines which can distinguish them. A key point is to spatially resolve the emission in the Spitzer-IRS spectra to separate extended PDR and shock emission from compact source emission associated with the circumstellar disk and jets. Methods: An optimal extraction method is used to separate both spatially unresolved (compact, up to a few hundred AU) and spatially resolved (extended, thousand AU or more) emission from the IRS spectra. The results are compared with the c2d disk sample and literature PDR and shock models to address the physical nature of the sources. Results: Both compact and extended emission features are observed. Warm (T_ex few hundred K) H2, observed through the pure rotational H2 S(0), S(1) and S(2) lines, and [S i] 25 μm emission is observed primarily in the extended component. [S i] is observed uniquely toward truly embedded sources and not toward disks. On the other hand hot (T_ex ⪆ 700 K) H2, observed primarily through the S(4) line, and [Ne ii] emission is seen mostly in the spatially unresolved component. [Fe ii] and [Si ii] lines are observed in both spatial components. Hot H2O emission is found in the spatially unresolved component of some sources. Conclusions: The observed emission on ≥1000 AU scales is characteristic of PDR emission and likely originates in the outflow cavities in the remnant envelope created by the stellar wind and jets from the embedded

  2. Impact of comprehensive two-dimensional gas chromatography with mass spectrometry on food analysis.

    PubMed

    Tranchida, Peter Q; Purcaro, Giorgia; Maimone, Mariarosa; Mondello, Luigi

    2016-01-01

    Comprehensive two-dimensional gas chromatography with mass spectrometry has been on the separation-science scene for about 15 years. This three-dimensional method has made a great positive impact on various fields of research, and among these that related to food analysis is certainly at the forefront. The present critical review is based on the use of comprehensive two-dimensional gas chromatography with mass spectrometry in the untargeted (general qualitative profiling and fingerprinting) and targeted analysis of food volatiles; attention is focused not only on its potential in such applications, but also on how recent advances in comprehensive two-dimensional gas chromatography with mass spectrometry will potentially be important for food analysis. Additionally, emphasis is devoted to the many instances in which straightforward gas chromatography with mass spectrometry is a sufficiently-powerful analytical tool. Finally, possible future scenarios in the comprehensive two-dimensional gas chromatography with mass spectrometry food analysis field are discussed.

  3. A high-throughput 2D-analytical technique to obtain single protein parameters from complex cell lysates for in silico process development of ion exchange chromatography.

    PubMed

    Kröner, Frieder; Elsäßer, Dennis; Hubbuch, Jürgen

    2013-11-29

    The accelerating growth of the market for biopharmaceutical proteins, the market entry of biosimilars and the growing interest in new, more complex molecules constantly pose new challenges for bioseparation process development. In the presented work we demonstrate the application of a multidimensional, analytical separation approach to obtain the relevant physicochemical parameters of single proteins in a complex mixture for in silico chromatographic process development. A complete cell lysate containing a low titre target protein was first fractionated by multiple linear salt gradient anion exchange chromatography (AEC) with varying gradient length. The collected fractions were subsequently analysed by high-throughput capillary gel electrophoresis (HT-CGE) after being desalted and concentrated. From the obtained data of the 2D-separation the retention-volumes and the concentration of the single proteins were determined. The retention-volumes of the single proteins were used to calculate the related steric-mass action model parameters. In a final evaluation experiment the received parameters were successfully applied to predict the retention behaviour of the single proteins in salt gradient AEC.

  4. The 2D method for determining the temperatures field of the gas flow at the outlet of a multi-channel heat exchanger

    NASA Astrophysics Data System (ADS)

    Slesareva, E. Yu; Elistratov, S. L.; Ovchinnikov, V. V.

    2016-10-01

    The method for experimental determination of energy efficiency in the multichannel heat exchanger was tested. The visualization of a temperatures field has been performed to determine the thermal structure of gas flows with the use of fast-response fine- meshed wire. Thermograms of the temperature fields of the multi-channels assembly at the outlet were registered by thermal imaging camera. Results show that the 2D method provides a sufficient time resolution for the temperature field for the steady-state gas flow regime, heat generation, and nonsteady regime. The 2D method allows us to determine the gas stream parameters at the channel outlet in real time, which are necessary for determining the efficiency of the heat exchanger. Qualitative and quantitative characters of temperature changes in the thermograms are consistent with modern physical understanding of the gas flow in channels.

  5. Headspace solid-phase microextraction--comprehensive two-dimensional gas chromatography of wound induced plant volatile organic compound emissions.

    PubMed

    Perera, Ranjini M M; Marriott, Philip J; Galbally, Ian E

    2002-12-01

    Plant emissions of volatile organic compounds from mechanically wounded Agrostis stolonifera, Pennisetum clandestinum, Eucalyptus leucoxylon and Trifolium repens have been sampled by headspace-solid phase microextraction (HS-SPME) and analysed by using comprehensive two-dimensional gas chromatography (GCxGC) for measurement of the plant emissions. GCxGC produces a fingerprint of the volatile organic compounds in a 2D separation space that may be approximately interpreted as a boiling point-polarity space, and may then be presented as a two-dimensional contour plot. This allows identification of sample-dependent variations in component distributions in the 2D plot, which will contain information about plant differences and should therefore facilitate recognition of different plant materials and displays the gross differences in volatiles between each plant species.

  6. Identification of New Metabolites of Bacterial Transformation of Indole by Gas Chromatography-Mass Spectrometry and High Performance Liquid Chromatography

    PubMed Central

    Arora, Pankaj Kumar

    2014-01-01

    Arthrobacter sp. SPG transformed indole completely in the presence of an additional carbon source. High performance liquid chromatography and gas chromatography-mass spectrometry detected indole-3-acetic acid, indole-3-glyoxylic acid, and indole-3-aldehyde as biotransformation products. This is the first report of the formation of indole-3-acetic acid, indole-3-glyoxylic acid, and indole-3-aldehyde from indole by any bacterium. PMID:25548566

  7. [Analysis of the phthalates in cosmetics by capillary gas chromatography].

    PubMed

    Chen, Huiming; Wang, Chao; Wang, Xing

    2004-05-01

    A capillary gas chromatographic method with flame ionization detector (GC-FID) for the detection of the six phthalates (dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), butyl benzyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DOP)) in the cosmetics was developed. The phthalates were extracted from cosmetics with methanol under ultrasonication and then separated with high-speed centrifugation. The supernatant was dehydrated and filtrated through membrane with 0.5 microm pore diameter. The filtrate was injected into the GC system for analysis. Then the positive results observed in the GC-FID chromatogram were confirmed by gas chromatography-electron impact-mass detection (GC-EI-MS) analysis. Retention times of the peaks could be applied for qualitative analysis. External standard method was used for quantitative analysis. The recoveries of the six phthalates were between 82.90% and 109.50%. The relative standard deviations were between 2.1% and 4.6%. The detection limits of the method were: 0.1 ng for DMP, DEP, DBP and BBP, and 0.5 ng for DEHP and DOP, respectively. The method presented the advantages of high precision, high sensitivity, small sample size, and simple pretreatment. The method can be used to test the six phthalates in the cosmetics.

  8. Analysis of odour compounds from scented consumer products using gas chromatography-mass spectrometry and gas chromatography-olfactometry.

    PubMed

    Bartsch, Jennifer; Uhde, Erik; Salthammer, Tunga

    2016-01-21

    Scented consumer products are being bought in increasing amounts and gaining more popularity. There is, however, relatively little information available about their ingredients, emissions and allergenic potential. Frequently, a mixture of different fragrance substances and not solely an individual substance contributes to the overall desired smell. The aim of this study was to investigate the odorous volatile organic compounds (OVOCs) in consumer products containing fragrances. Over 44 products were selected: various scented candles, printing products with different scent types and other products types particularly meant to be used indoors. Measurements were carried out in a desiccator. Air samples were collected on thermal desorption tubes to determine the released fragrance substances by means of gas chromatography-mass spectrometry (GC-MS). Moreover, gas chromatography-olfactometry (GC-O) was used to obtain sensory data and to ensure no important odorant was overlooked. Using both methods it was possible to distinguish between odour active and inactive compounds and subsequently to identify almost 300 different odorants across all scented products. Besides the advantage of differentiation, as the human nose is a very sensitive detector, GC-O was found to be a useful tool for detecting traces and chosen target compounds. One focus in this study lay on the 26 EU-regulated fragrance allergens to prove their relevance in scented consumer goods. In total, 18 of them were identified, with at least one substance being present in almost every product. Benzyl alcohol, cinnamaldehyde, citronellol, eugenol, linalool and limonene were the prevalently detected allergens. Particularly linalool and limonene were observed in over 50% of the products. In addition, eugenol appeared to be one of the most frequently detected compounds in trace-level concentrations in the candle emissions.

  9. Chromatography.

    ERIC Educational Resources Information Center

    Brantley, L. Reed, Sr.; Demanche, Edna L.; Klemm, E. Barbara; Kyselka, Will; Phillips, Edwin A.; Pottenger, Francis M.; Yamamoto, Karen N.; Young, Donald B.

    This booklet presents some activities on chromatography. Directions for preparing leaf pigment extracts using alcohol are given, and paper chromatography and thin-layer chromatography are described as modifications of the basic principles of chromatography. (KHR)

  10. An improved multiple flame photometric detector for gas chromatography.

    PubMed

    Clark, Adrian G; Thurbide, Kevin B

    2015-11-20

    An improved multiple flame photometric detector (mFPD) is introduced, based upon interconnecting fluidic channels within a planar stainless steel (SS) plate. Relative to the previous quartz tube mFPD prototype, the SS mFPD provides a 50% reduction in background emission levels, an orthogonal analytical flame, and easier more sensitive operation. As a result, sulfur response in the SS mFPD spans 4 orders of magnitude, yields a minimum detectable limit near 9×10(-12)gS/s, and has a selectivity approaching 10(4) over carbon. The device also exhibits exceptionally large resistance to hydrocarbon response quenching. Additionally, the SS mFPD uniquely allows analyte emission monitoring in the multiple worker flames for the first time. The findings suggest that this mode can potentially further improve upon the analytical flame response of sulfur (both linear HSO, and quadratic S2) and also phosphorus. Of note, the latter is nearly 20-fold stronger in S/N in the collective worker flames response and provides 6 orders of linearity with a detection limit of about 2.0×10(-13)gP/s. Overall, the results indicate that this new SS design notably improves the analytical performance of the mFPD and can provide a versatile and beneficial monitoring tool for gas chromatography.

  11. Gas-liquid chromatography of fecal neutral steriods.

    PubMed

    Gerhardt, K O; Gehrke, C W; Rogers, I T; Flynn, M A; Hentges, D J

    1977-05-21

    A method is described for the analysis of fecal neutral steriods with a dual-column gas-liquid chromatography (GLC) system. After saponification of the fecal slurry, the neutral steroids were extracted with hexane. The GLC separation of the compounds and quantitation were achieved by simultaneous injection of the derivatized and derivatized aliquots of the extract onto dual colmuns under identical conditions. The neutral steroids of interest were than identified by matching the retention times with those of known standards, and identification was confirmed by use of an interfaced GLC high-resolution mass spectrometry system. The detection limit was 0.003 mg of steroid/g of fecal slurry. The pricision of the method is illustrated by a relative standard diviation of 2-10% and a recovery of neutral steroids from 73-96%. The method was applied to the determination of fecal neutral steroids in a "High protein diet in colon cancer study". A considerably larger level of coprostanone than of coprostanol was observed. Data on neutral steroids in fecal samples from subjects on different diets are the subject of a separate publication.

  12. [Determination of dimethyl ether correction factors in gas chromatography with TCD and FID].

    PubMed

    Chen, J; Zhang, L; Yang, L; Cai, G

    1997-05-01

    Dimethyl ether (DME) correction factors in gas chromatography with thermal conductivity detector (TCD) and flame ionization detector (FID) by using H2 as carrier gas were determined in this work. The homemade DME gas was quantitatively absorbed in ice-cold water. With ethanol as standard, the aqueous mixture was injected into a gas chromatograph, equipped with serially-connected TCD and FID. The weight correction factors of DME based on methanol were 0.86 and 0.55 for TCD and FID respectively. The result for TCD was also confirmed by calculation based on the stoichiometrical transformation of methanol into DME in reaction gas chromatography.

  13. 3D Reservoir Modeling of Semutang Gas Field: A lonely Gas field in Chittagong-Tripura Fold Belt, with Integrated Well Log, 2D Seismic Reflectivity and Attributes.

    NASA Astrophysics Data System (ADS)

    Salehin, Z.; Woobaidullah, A. S. M.; Snigdha, S. S.

    2015-12-01

    Bengal Basin with its prolific gas rich province provides needed energy to Bangladesh. Present energy situation demands more Hydrocarbon explorations. Only 'Semutang' is discovered in the high amplitude structures, where rest of are in the gentle to moderate structures of western part of Chittagong-Tripura Fold Belt. But it has some major thrust faults which have strongly breached the reservoir zone. The major objectives of this research are interpretation of gas horizons and faults, then to perform velocity model, structural and property modeling to obtain reservoir properties. It is needed to properly identify the faults and reservoir heterogeneities. 3D modeling is widely used to reveal the subsurface structure in faulted zone where planning and development drilling is major challenge. Thirteen 2D seismic and six well logs have been used to identify six gas bearing horizons and a network of faults and to map the structure at reservoir level. Variance attributes were used to identify faults. Velocity model is performed for domain conversion. Synthetics were prepared from two wells where sonic and density logs are available. Well to seismic tie at reservoir zone shows good match with Direct Hydrocarbon Indicator on seismic section. Vsh, porosity, water saturation and permeability have been calculated and various cross plots among porosity logs have been shown. Structural modeling is used to make zone and layering accordance with minimum sand thickness. Fault model shows the possible fault network, those liable for several dry wells. Facies model have been constrained with Sequential Indicator Simulation method to show the facies distribution along the depth surfaces. Petrophysical models have been prepared with Sequential Gaussian Simulation to estimate petrophysical parameters away from the existing wells to other parts of the field and to observe heterogeneities in reservoir. Average porosity map for each gas zone were constructed. The outcomes of the research

  14. Insights into Gulf of Mexico Gas Hydrate Study Sites GC955 and WR313 from New Multicomponent and High-Resolution 2D Seismic Data

    NASA Astrophysics Data System (ADS)

    Haines, S. S.; Hart, P. E.; Collett, T. S.; Shedd, W. W.; Frye, M.

    2014-12-01

    In 2013, the U.S. Geological Survey led a seismic acquisition expedition in the Gulf of Mexico, acquiring multicomponent data and high-resolution 2D multichannel seismic (MCS) data at Green Canyon 955 (GC955) and Walker Ridge 313 (WR313). Based on previously collected logging-while-drilling (LWD) borehole data, these gas hydrate study sites are known to include high concentrations of gas hydrate within sand layers. At GC955 our new 2D data reveal at least three features that appear to be fluid-flow pathways (chimneys) responsible for gas migration and thus account for some aspects of the gas hydrate distribution observed in the LWD data. Our new data also show that the main gas hydrate target, a Pleistocene channel/levee complex, has an areal extent of approximately 5.5 square kilometers and that a volume of approximately 3 x 107 cubic meters of this body lies within the gas hydrate stability zone. Based on LWD-inferred values and reasonable assumptions for net sand, sand porosity, and gas hydrate saturation, we estimate a total equivalent gas-in-place volume of approximately 8 x 108 cubic meters for the inferred gas hydrate within the channel/levee deposits. At WR313 we are able to map the thin hydrate-bearing sand layers in considerably greater detail than that provided by previous data. We also can map the evolving and migrating channel feature that persists in this area. Together these data and the emerging results provide valuable new insights into the gas hydrate systems at these two sites.

  15. [Analysis of cracking gas compressor fouling by pyrolysis gas chromatography-mass spectrometry].

    PubMed

    Hu, Yunfeng; Fang, Fei; Wei, Tao; Liu, Shuqing; Jiang, Guangshen; Cai, Jun

    2013-06-01

    The fouling from the different sections of the cracked gas compressor in Daqing Petrochemical Corporation was analyzed by pyrolysis gas chromatography-mass spectrometry (Py/GC-MS). All the samples were cracked in RJ-1 tube furnace cracker at the cracking temperature of 500 degrees C, and separated with a 60 m DB-1 capillary column. An electron impact ionization (EI) source was used with the ionizing voltage of 70 eV. The results showed the formation of fouling was closely related with cyclopentadiene which accounted for about 50% of the cracking products. Other components detected were 1-butylene, propylene, methane and n-butane. This Py/GC-MS method can be used as an effective approach to analyze the causes of fouling in the petrochemical plants.

  16. Separation of stereoisomers of several furan derivatives by capillary gas chromatography-mass spectrometry, supercritical fluid chromatography, and liquid chromatography using chiral stationary phases.

    PubMed

    Kasai, Hiroko F; Tsubuki, Masayoshi; Takahashi, Kazunori; Shirao, Mika; Matsumoto, Yohichiro; Honda, Toshio; Seyama, Yoshiyuki

    2002-11-15

    The direct separation of several stereoisomers (enantiomers and geometrical isomers) of furan derivatives, important intermediates for the synthesis of physiologically active natural products, was achieved using capillary gas chromatography/mass spectrometry with a per-O-methyl-beta-cyclodextrin, supercritical fluid chromatography and high-performance liquid chromatography with a tris(3,5-dimethylphenylcarbamate) of cellulose or amylose for the chiral stational phases, respectively. The temperature dependence of the peak resolution (Rs) and the retention factor (k) over the range of 110-130 degrees was studied using crotyl furfuryl ether in gas chromatography. Successive increases in the Rs value and of the difference between the k value of the E-isomer and the k value of the Z-isomer were observed when the gradient temperature was decreased. The per-O-methyl-beta-cyclodextrin column was suitable for use with volatile furan ethers whose molecular masses are between 150 and 180. In conclusion, the separation of thermally unstable furan derivatives was accomplished using supercritical fluid chromatography and high-performance liquid chromatography.

  17. Multiresidue analysis of pesticides in soil by gas chromatography with nitrogen-phosphorus detection and gas chromatography mass spectrometry.

    PubMed

    Fenoll, José; Hellín, Pilar; Marín, Cristóbal; Martínez, Carmen M; Flores, Pilar

    2005-10-05

    A rapid multiresidue method for the simultaneous determination of 25 fungicides and insecticides in soil was developed. Soil samples are extracted by sonication with a water-acetonitrile mixture, and the pesticides are partitioned into dichloromethane. Final determination was made by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). Confirmation analysis of pesticides was carried out by GC-MS in the selected ion monitoring (SIM) mode. The identification of compounds was based on retention time and on comparison of the primary and secondary ions. The average recovery by the GC-NPD method obtained for these compounds varied from 68.5% to 112.1% with a relative standard deviation between 1.8% and 6.2%. The GC-NPD method presents good linearity over the range assayed 50-2000 microg/L, and the detection limit for the pesticides studied varied from 0.1 to 10.4 microg/kg. The proposed method was used to determine pesticide levels in soil samples from experimental greenhouse pepper cultivation.

  18. DIRECT-DEPOSITION INFRARED SPECTROMETRY WITH GAS AND SUPERCRITICAL FLUID CHROMATOGRAPHY

    EPA Science Inventory

    A direct-deposition Fourier transform infrared (FT-IR) system has been evaluated for applicability to gas chromatography (GC) and supercritical fluid chromatography (SFC) of environmental analytes. A 100-um i.d. fused-silica transfer line was used for GC, and a 50-um transfer lin...

  19. Preparation of pure microbiological samples for pyrolysis gas-liquid chromatography studies

    NASA Technical Reports Server (NTRS)

    Oxborrow, G. S.; Fields, N. D.; Puleo, J. R.

    1976-01-01

    Bacterial samples were prepared for pyrolysis gas-liquid chromatography using cells grown on membrane filters. Pyrochromatograms were reproducible when cells harvested from the filters were pyrolyzed without being washed.

  20. VACUUM DISTILLATION COUPLED WITH GAS CHROMATOGRAPHY/MASS SPECTROMETRY FOR THE ANALYSIS OF ENVIRONMENTAL SAMPLES

    EPA Science Inventory

    A procedure is presented that uses a vacuum distillation/gas chromatography/mass spectrometry system for analysis of problematic matrices of volatile organic compounds. The procedure compensates for matrix effects and provides both analytical results and confidence intervals from...

  1. ENVIRONMENTAL ANALYSIS BY AB INITIO QUANTUM MECHANICAL COMPUTATION AND GAS CHROMATOGRAPHY/FOURIER TRANSFORM INFRARED SPECTROMETRY.

    EPA Science Inventory

    Computational chemistry, in conjunction with gas chromatography/mass spectrometry/Fourier transform infrared spectrometry (GC/MS/FT-IR), was used to tentatively identify seven tetrachlorobutadiene (TCBD) isomers detected in an environmental sample. Computation of the TCBD infrare...

  2. Chemical Composition of Latent Fingerprints by Gas Chromatography-Mass Spectrometry

    ERIC Educational Resources Information Center

    Hartzell-Baguley, Brittany; Hipp, Rachael E.; Morgan, Neal R.; Morgan, Stephen L.

    2007-01-01

    An experiment in which gas chromatography-mass spectrometry (GC-MS) is used for latent fingerprint extraction and analysis on glass beads or glass slides is conducted. The results determine that the fingerprint residues are gender dependent.

  3. DETERMINATION OF CHLOROETHENES IN ENVIRONMENTAL BIOLOGICAL SAMPLES USING GAS CHROMATOGRAPHY COUPLED WITH SOLID PHASE MICRO EXTRACTION

    EPA Science Inventory

    An analytical method has been developed to determine the chloroethene series, tetrachloroethene (PCE), trichloroethene (TCE),cisdichloroethene (cis-DCE) andtransdichloroethene (trans-DCE) in environmental biotreatment studies using gas chromatography coupled with a solid phase mi...

  4. Reversible Formation of 2D Electron Gas at the LaFeO3 /SrTiO3 Interface via Control of Oxygen Vacancies.

    PubMed

    Xu, Pengfa; Han, Wei; Rice, Philip M; Jeong, Jaewoo; Samant, Mahesh G; Mohseni, Katayoon; Meyerheim, Holger L; Ostanin, Sergey; Maznichenko, Igor V; Mertig, Ingrid; Gross, Eberhard K U; Ernst, Arthur; Parkin, Stuart S P

    2017-03-01

    A conducting 2D electron gas (2DEG) is formed at the interface between epitaxial LaFeO3 layers >3 unit cells thick and the surface of SrTiO3 single crystals. The 2DEG is exquisitely sensitive to cation intermixing and oxygen nonstoichiometry. It is shown that the latter thus allows the controllable formation of the 2DEG via ionic liquid gating, thereby forming a nonvolatile switch.

  5. Evaluation of Gas Chromatography/Mini-IMS to Detect VOCs

    NASA Technical Reports Server (NTRS)

    Limero, Thomas; Reese, Eric; Peters, Randy; James, John T.; Billica, Roger (Technical Monitor)

    1999-01-01

    The Toxicology Laboratory at Johnson Space Center (JSC) has pioneered the use of gas chromatography-ion mobility spectrometry (GC/IMS) for measuring target volatile organic compounds (VOCs) aboard spacecraft. Graseby Dynamics, under contract to NASA/Wyle, has built several volatile organic analyzers (VOA) based on GC/IMS. Foremost among these have been the volatile organic analyzer-risk mitigation unit and the two flight VOA units for International Space Station (ISS). The development and evaluation of these instruments has been chronicled through presentations at the International Conference on Ion Mobility Spectrometry over the past three years. As the flight VOA from Graseby is prepared for operation on ISS at JSC, it is time to begin evaluations of technologies for the next generation VOA, Although the desired instrument characteristics for the next generation unit are the same as the current unit, the requirements are much more stringent. As NASA looks toward future missions beyond Earth environs, a premium will be placed upon small, light, reliable, autonomous hardware. It is with these visions in mind that the JSC Toxicology Laboratory began a search for the next generation VOA. One technology that is a candidate for the next generation VOA is GC/IMS. The recent miniaturization of IMS technology permits it to compete with other, inherently small, technologies such as chip-sized sensor arrays. This paper will discuss the lessons learned from the VOA experience and how that has shaped the design of a potential second generation VOA based upon GC/IMS technology. Data will be presented from preliminary evaluations of GC technology and the mini-IMS when exposed to VOCs likely to be detected aboard spacecraft. Results from the evaluation of an integrated GC/mini-IMS system will be shown if available.

  6. Enantiomeric separation in comprehensive two-dimensional gas chromatography with accurate mass analysis.

    PubMed

    Chin, Sung-Tong; Nolvachai, Yada; Marriott, Philip J

    2014-11-01

    Chiral comprehensive two-dimensional gas chromatography (eGC×GC) coupled to quadrupole-accurate mass time-of-flight mass spectrometry (QTOFMS) was evaluated for its capability to report the chiral composition of several monoterpenes, namely, α-pinene, β-pinene, and limonene in cardamom oil. Enantiomers in a standard mixture were fully resolved by direct enantiomeric-GC analysis with a 2,3-di-O-methyl-6-t-butylsilyl derivatized β-cyclodextrin phase; however, the (+)-(R)-limonene enantiomer in cardamom oil was overlapped with other background components including cymene and cineole. Verification of (+)-(R)-limonene components based on characteristic ions at m/z 136, 121, and 107 acquired by chiral single-dimension GC-QTOFMS in the alternate MS/MSMS mode of operation was unsuccessful due to similar parent/daughter ions generated by interfering or co-eluting cymene and cineole. Column phases SUPELCOWAX, SLB-IL111, HP-88, and SLB-IL59, were incorporated as the second dimension column ((2)D) in chiral GC×GC analysis; the SLB-IL59 offered the best resolution for the tested monoterpene enantiomers from the matrix background. Enantiomeric ratios for α-pinene, β-pinene, and limonene were determined to be 1.325, 2.703, and 1.040, respectively, in the cardamom oil sample based on relative peak area data.

  7. Profiling of soil fatty acids using comprehensive two-dimensional gas chromatography with mass spectrometry detection.

    PubMed

    Zeng, Annie Xu; Chin, Sung-Tong; Patti, Antonio; Marriott, Philip J

    2013-11-22

    Profiling of phospholipid fatty acids (PLFA) represents a challenging goal for distinguishing the diversity of microbial communities and biomass in the complex and heterogeneous soil ecosystem. Comprehensive two-dimensional gas chromatography (GC×GC) coupled with simultaneous flame ionisation and mass spectrometry detection was applied as a culture-independent method for PLFA profiling of microbial classification in forest soil. A number of column sets were evaluated for the GC×GC separation of fatty acid methyl esters (FAME). Due to better isomeric separation and compound patterns on the 2D contour plot, an apolar-polar column combination was selected for soil microbial PLFA characterisation. A comprehensive view of PLFA composition with carbon chain length varying from 12 to 20 was observed in forest soil samples, with the commonly reported bacterial FAME of iso-/anteiso-, methyl-branched-, cyclopropyl-, and hydroxyl-substituted FA identified by their mass spectral and retention time according to authentic standards. Notably, some uncommon oxygenated FAME were found in high abundance and were further characterised by GC×GC coupled with high resolution mass spectrometry. This tentatively revealed geometric pairs of methyl 9,10-epoxyoctadecanoate isomers.

  8. Urinary 19-norandrosterone purification by immunoaffinity chromatography: application to gas chromatography/combustion/isotope ratio mass spectrometric analysis.

    PubMed

    Desroches, M C; Mathurin, J C; Richard, Y; Delahaut, P; de Ceaurriz, J

    2002-01-01

    The detection of exogenous 19-norandrosterone (19-NA) in urines was investigated by using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). 19-NA is, for the first time to our knowledge, isolated from urinary matrix by specific immunoaffinity chromatography (IAC) before analysis. The sample preparation consisted of a preliminary purification of urine by solid-phase extraction after hydrolysis by beta-glucuronidase. Unconjugated 19-NA was thus isolated by IAC and directly analysed by GC/C/IRMS. Optimisation of IAC purification was achieved and the reliability of the technique for anti-doping control is discussed.

  9. Growth of 2D sheets of a MOF on graphene surfaces to yield composites with novel gas adsorption characteristics.

    PubMed

    Kumar, Ram; Jayaramulu, Kolleboyina; Maji, Tapas Kumar; Rao, C N R

    2014-05-28

    Homogeneous graphene-MOF composites based on a 2D pillared-bilayer MOF (Cd-PBM), {[Cd4(azpy)2(pyrdc)4(H2O)2]·9H2O}n (azpy = 4,4'-azopyridine, pyrdc = pyridine-2,3-dicarboxylate), have been synthesized, using both graphene oxide (GO) and benzoic acid functionalized graphene (BFG). The composites GO@Cd-PBM and BFG@Cd-PBM demonstrate growth of the 2D nano-sheets of MOF on the graphene surface. While the pristine MOF, Cd-PBM shows selective CO2 uptake with a single-step type-I adsorption profile, the composites show stepwise CO2 uptake with a large hysteresis. With H2O and MeOH, on the other hand, the composites show a single-step adsorption unlike the parent MOF.

  10. High temperature diaphragm valve-based comprehensive two-dimensional gas chromatography.

    PubMed

    Freye, Chris E; Mu, Lan; Synovec, Robert E

    2015-12-11

    A high-temperature diaphragm valve-based comprehensive two-dimensional gas chromatography (GC×GC) instrument is demonstrated which readily allows separations up to 325°C. Previously, diaphragm valve-based GC×GC was limited to 175°C if the valve was mounted in the oven, or limited to 265°C if the valve was faced mounted on the outside of the oven. A new diaphragm valve has been commercially developed, in which the temperature sensitive O-rings that previously limited the separation temperatures have been replaced with Kalrez O-rings, a perfluoroelastomer, allowing for significantly higher temperatures permitting a greater range of volatile and semi-volatile compounds to be readily separated. In the current investigation, a separation temperature up to 325°C is demonstrated with the valve mounted directly in the oven. Since the temperature limit for most commonly used GC columns is at or below 325°C, the scope of diaphragm valve-based GC×GC is now dramatically broadened to encompass a majority of all column stationary phase chemistries. A 44-component mixture of alkanes, alcohols, and polyaromatic hydrocarbons is used to study this new configuration whose boiling points range from 98°C (n-heptane) to 450°C (n-triacontane). For the test mixture using a modulation period PM of 1.0s, peak shapes on second dimension separations, (2)D, are symmetric with average widths at base of 79.4ms, producing a (2)D peak capacity of (2)nc∼12. Based on the average peak width of 2.4s for the first dimension separation with a run time of 32.5min, the (1)D peak capacity is (1)nc∼800. Thus, the ideal two-dimensional peak capacity [Formula: see text] is 9600. Little variation in within-analyte (2)D peak width was observed with an average %RSD of less than 3.0%. Furthermore, retention time on (2)D was very reproducible with an average %RSD less than 0.5%. Measured peak areas (sum of all (2)D peaks for given analyte) had an average %RSD of 4.4%. The transfer fraction from (1)D

  11. Evaluation of reversible interconversion in comprehensive two-dimensional gas chromatography using enantioselective columns in first and second dimensions.

    PubMed

    Kröger, Sabrina; Wong, Yong Foo; Chin, Sung-Tong; Grant, Jacob; Lupton, David; Marriott, Philip J

    2015-07-24

    The reversible molecular interconversion behaviour of a synthesised oxime (2-phenylpropanaldehyde oxime; (C6H5)CH(CH3)CHN(OH)) was investigated by both, single dimensional gas chromatography (1D GC) and comprehensive two-dimensional gas chromatography (GC×GC). Previous studies on small molecular weight oximes were extended to this larger aromatic oxime (molar mass 149.19gmol(-1)) with interest in the extent of interconversion, enantioselective resolution, and retention time. On a polyethylene glycol (PEG; wax-type) column, a characteristic interconversion zone between two antipodes of E and Z isomers was formed by molecules which have undergone isomerisation on the column (E⇌Z). The extent of interconversion was investigated by varying chromatographic conditions (oven temperature and carrier flow rate) to understand the nature of the behaviour observed. The extent of interconversion was negligible in both enantioselective and methyl-phenylpolysiloxane phase-columns, correlating with the low polarity of the stationary phase. In order to obtain isomerisation along with enantio-resolution, a wax-type and an enantioselective column were coupled in either enantioselective-wax or wax-enantioselective order. The most appropriate column arrangement was selected for study by using a GC×GC experiment with either a wax-phase or phenyl-methylpolysiloxane phase as (2)D column. In addition to evaluation of these fast elution columns, a long narrow-bore enantioselective column (10m) was introduced as (2)D, providing an enantioselective-PEG (coupled-column ensemble: (1)D1+(1)D2)×enantioselective ((2)D) column combination. In this instance, the (1)D1 enantioselective column provides enantiomeric separation of the corresponding enantiomers ((R) and (S)) of (E)- and (Z)-2-phenylpropanaldehyde oxime, followed by E/Z isomerisation in the coupled (1)D2 PEG (reactor) column. The resulting chromatographic interconversion region was modulated and separated into either E/Z isomers

  12. Dual-injection system with multiple injections for determining bidimensional retention indexes in comprehensive two-dimensional gas chromatography.

    PubMed

    Bieri, Stefan; Marriott, Philip J

    2008-02-01

    A new instrumental approach for collection of retention index data in the first (1D) and second (2D) dimensions of a comprehensive two-dimensional (2D) gas chromatography (GCxGC) experiment has been developed. First-dimension indexes were determined under conventional linear programmed temperature conditions (Van den Dool indexes). To remove the effect that the short secondary column imposes on derived 1D indexes, as well as to avoid handling of pulsed GCxGC peaks, the proposed approach uses a flow splitter to divert part of the primary column flow to a supplementary detector to simultaneously generate a conventional 1D chromatogram, along with the GCxGC chromatogram. The critical 2D indexes (KovAts indexes) are based upon isovolatility curves of normal alkanes in 2D space, providing a reference scale against which to correlate each individual target peak throughout the entire GCxGC run. This requires the alkanes to bracket the analytes in order to allow retention interpolation. Exponential curves produced in the 2D separation space require a novel approach for delivery of alkane standards into the 2D column by using careful solvent-free solid-phase microextraction (SPME) sampling. Sequential introduction of alkane mixtures during GCxGC runs was performed by thermal desorption in a second injector which was directly coupled through a short transfer line to the entrance of the secondary column, just prior to the modulator so that they do not have to travel through the 1D column. Thus, each alkane mixture injection was quantitatively focused by the cryogenic trap, then launched at predetermined times onto the 2D column. The system permitted construction of an alkane retention map upon which bidimensional indexes of a 25-perfume ingredient mixture could be derived. Comparison of results with indexes determined in temperature-variable one-dimensional (1D) GC showed good correlation. Plotting of the separation power in the second dimension was possible by mapping

  13. Doping control analysis of anabolic steroids in equine urine by gas chromatography-tandem mass spectrometry.

    PubMed

    Wong, April S Y; Leung, Gary N W; Leung, David K K; Wan, Terence S M

    2016-09-08

    Anabolic steroids are banned substances in equine sports. Gas chromatography-mass spectrometry (GC-MS) has been the traditional technique for doping control analysis of anabolic steroids in biological samples. Although liquid chromatography-mass spectrometry (LC/MS) has become an important technique in doping control, the detection of saturated hydroxysteroids by LC-MS remains a problem due to their low ionization efficiency under electrospray. The recent development in fast-scanning gas-chromatography-triple-quadrupole mass spectrometry (GC-MS/MS) has provided a better alternative with a significant reduction in chemical noise by means of selective reaction monitoring. Herein, we present a sensitive and selective method for the screening of over 50 anabolic steroids in equine urine using gas chromatography-tandem mass spectrometry (GC-MS/MS). Copyright © 2016 John Wiley & Sons, Ltd.

  14. Analysis of radioactive mixed hazardous waste using derivatization gas chromatography/mass spectrometry, liquid chromatography, and liquid chromatography/mass spectrometry

    SciTech Connect

    Campbell, J.A.; Lerner, B.D.; Bean, R.M.; Grant, K.E.; Lucke, R.B.; Mong, G.M.; Clauss, S.A.

    1994-08-01

    Six samples of core segments from Tank 101-SY were analyzed for chelators, chelator fragments, and several carboxylic acids by derivatization gas chromatography/mass spectrometry. The major components detected were ethylenediaminetetraacetic acid, nitroso-iminodiacetic acid, nitrilotriacetic acid, citric acid, succinic acid, and ethylenediaminetriacetic acid. The chelator of highest concentration was ethylenediaminetetraacetic acid in all six samples analyzed. Liquid chromatography was used to quantitate low molecular weight acids including oxalic, formic, glycolic, and acetic acids, which are present in the waste as acid salts. From 23 to 61% of the total organic carbon in the samples analyzed was accounted for by these acids.

  15. High resolution gas chromatography analysis of rice bran oil

    NASA Astrophysics Data System (ADS)

    Yu, Fengxiang; Lin, Qinlu; Chen, Xu; Wei, Xiaojun

    To assess the nutritional value and safety quality of rice bran oil (RBO) ,fatty acids of RBO from 15 species rice come from Hunan Province were analyzed by high resolution gas chromatography (HRGC). Crude RBOs were extracted by hexane 3-times using a solvent-to-rice bran ratio of 3:1 (w/w) at 40°C and composition of RBOs was analyzed by HRGC. The result showed that main fatty acids of 15 kinds of RBO include myristic acid (C14:0), palmitic acid (C16:0), palmitoleic acid (C16:1), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), linolenic acid (C18:3), arachidic acid (C20:0), arachidonic acid (C20:1). It is strange that arachidonic acid (C20:1) is not listed in Chinese standard of RBO (GB11192-2003), and it exists in our samples of RBO. The average value of linolenic acid in RBOs is 1.6304% (range from 1.2425% to 2.131%), and it showed higher level comparing with Chinese standard that linolenic acid is less than 1.0%. The average value of USFA and SFA are 76.81% (range 75.96% to 82.06% ) and 20.15% (range 13.72% to 23.06%) respectively, and USFA content is close to olive oil (83.75%), peanut oil (81.75%) and soybean oil (85.86%). USFA in Jingyou 13 RBO is the highest content. The ratio of USFA to SFA content is 4:1 (range from 3.32 to 5.98:1). The ratio of SFA: MUFA: PUFA of 15 RBOs is 1: 2.2: 1.8, and ω6/ω3 ratio is 21.69 (range from16.54 to 27.28) and it is close to the 26:1 which is reported to be helpful to increase SOD activity. The oleic acid /linoleic acid ratio of 15 RBOs is 1.23:1 (rang from 1.04:1 to 1.42:1). Our data analyzed composition of RBOs from 15 species rice of China and will provide new evidence to revise RBO standard. It also helps us to assess nutritional value of RBOs and identify different RBOs from various species rice and places of origin.

  16. Identification of Explosives from Porous Materials: Applications Using Reverse Phase High Performance Liquid Chromatography and Gas Chromatography

    NASA Astrophysics Data System (ADS)

    Miller, C. J.; Elias, G.; Schmitt, N. C.; Rae, C.

    2010-06-01

    High performance liquid chromatography and gas chromatography techniques are well documented and widely used for the detection of trace explosives from organic solvents. These techniques were modified to identify and quantify explosives extracted from various materials taken from people who had recently handled explosives. Documented techniques were modified to specifically detect and quantify trace levels of the military explosives, RDX, TNT, and PETN from denim, colored flannel, vinyl, and canvas extracted in methanol and filtered using no additional sample cleanup of the sample extract prior to analysis. The filtered methanol extracts were injected directly into several different column types and analyzed by high performance liquid chromatography using ultraviolet detection and/or gas chromatography using electron capture detection. This paper describes general screening methods that were used to determine the presence of explosives (RDX, TNT, and PETN) in unknown samples of denim, colored flannel, vinyl and canvas in addition to techniques that have been optimized for quantification of each explosive from the substrate extracts.

  17. Seismic investigation of gas hydrates in the Gulf of Mexico: 2013 multi-component and high-resolution 2D acquisition at GC955 and WR313

    USGS Publications Warehouse

    Haines, Seth S.; Hart, Patrick E.; Shedd, William W.; Frye, Matthew

    2014-01-01

    The U.S. Geological Survey led a seismic acquisition cruise at Green Canyon 955 (GC955) and Walker Ridge 313 (WR313) in the Gulf of Mexico from April 18 to May 3, 2013, acquiring multicomponent and high-resolution 2D seismic data. GC955 and WR313 are established, world-class study sites where high gas hydrate saturations exist within reservoir-grade sands in this long-established petroleum province. Logging-while-drilling (LWD) data acquired in 2009 by the Gulf of Mexico Gas Hydrates Joint Industry Project provide detailed characterization at the borehole locations, and industry seismic data provide regional- and local-scale structural and stratigraphic characterization. Significant remaining questions regarding lithology and hydrate saturation between and away from the boreholes spurred new geophysical data acquisition at these sites. The goals of our 2013 surveys were to (1) achieve improved imaging and characterization at these sites and (2) refine geophysical methods for gas hydrate characterization in other locations. In the area of GC955 we deployed 21 ocean-bottom seismometers (OBS) and acquired approximately 400 km of high-resolution 2D streamer seismic data in a grid with line spacing as small as 50 m and along radial lines that provide source offsets up to 10 km and diverse azimuths for the OBS. In the area of WR313 we deployed 25 OBS and acquired approximately 450 km of streamer seismic data in a grid pattern with line spacing as small as 250 m and along radial lines that provide source offsets up to 10 km for the OBS. These new data afford at least five times better resolution of the structural and stratigraphic features of interest at the sites and enable considerably improved characterization of lithology and the gas and gas hydrate systems. Our recent survey represents a unique application of dedicated geophysical data to the characterization of confirmed reservoir-grade gas hydrate accumulations.

  18. Investigation of Pinus mugo essential oil oxygenated fraction by combined use of gas chromatography and dry column chromatography.

    PubMed

    A, M B; Coran, S A; Giannellini, V; Vincieri, F F; Moneti, G

    1981-09-01

    The oxygenated compounds of Pinus mugo Turra essential oil were investigated by a combination of GC and dry column chromatography (DCC) coordinated by GC data processing. The collected data resulted in a bar graph ("normalized" gas chromatogram) giving the RRT's and relative amounts of 68 components; 38 of them were identified by MS and IR. The described procedure may be used for essential oil analysis in general.

  19. Seismic investigation of gas hydrates in the Gulf of Mexico: Results from 2013 high-resolution 2D and multicomponent seismic surveys

    NASA Astrophysics Data System (ADS)

    Haines, S. S.; Hart, P. E.; Shedd, W. W.; Frye, M.; Agena, W.; Miller, J. J.; Ruppel, C. D.

    2013-12-01

    In the spring of 2013, the U.S. Geological Survey led a 16-day seismic acquisition cruise aboard the R/V Pelican in the Gulf of Mexico to survey two established gas hydrate study sites. We used a pair of 105/105 cubic inch generator/injector airguns as the seismic source, and a 450-m 72-channel hydrophone streamer to record two-dimensional (2D) data. In addition, we also deployed at both sites an array of 4-component ocean-bottom seismometers (OBS) to record P- and S-wave energy at the seafloor from the same seismic source positions as the streamer data. At lease block Green Canyon 955 (GC955), we acquired 400 km of 2-D streamer data, in a 50- to 250-m-spaced grid augmented by several 20-km transects that provide long offsets for the OBS. The seafloor recording at GC955 was accomplished by a 2D array of 21 OBS at approximately 400-m spacing, including instruments carefully positioned at two of the three boreholes where extensive logging-while-drilling data is available to characterize the presence of gas hydrate. At lease block Walker Ridge 313 (WR313), we acquired 450 km of streamer data in a set of 11-km, 150- to 1,000-m-spaced, dip lines and 6- to 8-km, 500- to 1000-m-spaced strike lines. These were augmented by a set of 20-km lines that provide long offsets for a predominantly linear array of 25 400- to 800-m spaced OBS deployed in the dip direction in and around WR313. The 2D data provide at least five times better resolution of the gas hydrate stability zone than the available petroleum industry seismic data from the area; this enables considerably improved analysis and interpretation of stratigraphic and structural features including previously unseen faults and gas chimneys that may have considerable impact on gas migration. Initial processing indicates that the OBS data quality is good, and we anticipate that these data will yield estimates of P- and S-wave velocities, as well as PP (reflected) and PS (converted wave) images beneath each sensor location.

  20. Multiplex gas chromatography: an alternative concept for gas chromatographic analysis of planetary atmospheres.

    PubMed

    Valentin, J R

    1989-03-01

    Gas chromatography (GC) is a powerful technique for analyzing gaseous mixtures. Applied to the earth's atmosphere, GC can be used to determine the permanent gases--such as carbon dioxide, nitrogen, and oxygen--and to analyze organic pollutants in air. The U.S. National Aeronautics and Space Administration (NASA) has used GC in spacecraft missions to Mars (the Viking Biology Gas Exchange Experiment [GEX] and the Viking Gas Chromatograph-Mass Spectrometer [GC-MS]) and to Venus (the Pioneer Venus Gas Chromatograph [PVGC] on board the Pioneer Venus sounder probe) for determining the atmospheric constituents of these two planets. Even though conventional GC was very useful in the Viking and Pioneer missions, spacecraft constraints and limitations intrinsic to the technique prevented the collection of more samples. With the Venus probe, for instance, each measurement took a relatively long time to complete (10 min), and successive samples could not be introduced until the previous samples had left the column. Therefore, while the probe descended through the Venusian atmosphere, only three samples were acquired at widely separated altitudes. With the Viking mission, the sampling rate was not a serious problem because samples were acquired over a period of one year. However, the detection limit was a major disadvantage. The GC-MS could not detect simple hydrocarbons and simple alcohols below 0.1 ppm, and the GEX could not detect them below 1 ppm. For more complex molecules, the detection limits were at the parts-per-billion level for both instruments. Finally, in both the Viking and Pioneer missions, the relatively slow rate of data acquisition limited the number of analyses, and consequently, the amount of information returned. Similar constraints are expected in future NASA missions. For instance, gas chromatographic instrumentation is being developed to collect and analyze organic gases and aerosols in the atmosphere of Titan (one of Saturn's satellites). The Titan

  1. Multiplex gas chromatography: an alternative concept for gas chromatographic analysis of planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Valentin, J. R.

    1989-01-01

    Gas chromatography (GC) is a powerful technique for analyzing gaseous mixtures. Applied to the earth's atmosphere, GC can be used to determine the permanent gases--such as carbon dioxide, nitrogen, and oxygen--and to analyze organic pollutants in air. The U.S. National Aeronautics and Space Administration (NASA) has used GC in spacecraft missions to Mars (the Viking Biology Gas Exchange Experiment [GEX] and the Viking Gas Chromatograph-Mass Spectrometer [GC-MS]) and to Venus (the Pioneer Venus Gas Chromatograph [PVGC] on board the Pioneer Venus sounder probe) for determining the atmospheric constituents of these two planets. Even though conventional GC was very useful in the Viking and Pioneer missions, spacecraft constraints and limitations intrinsic to the technique prevented the collection of more samples. With the Venus probe, for instance, each measurement took a relatively long time to complete (10 min), and successive samples could not be introduced until the previous samples had left the column. Therefore, while the probe descended through the Venusian atmosphere, only three samples were acquired at widely separated altitudes. With the Viking mission, the sampling rate was not a serious problem because samples were acquired over a period of one year. However, the detection limit was a major disadvantage. The GC-MS could not detect simple hydrocarbons and simple alcohols below 0.1 ppm, and the GEX could not detect them below 1 ppm. For more complex molecules, the detection limits were at the parts-per-billion level for both instruments. Finally, in both the Viking and Pioneer missions, the relatively slow rate of data acquisition limited the number of analyses, and consequently, the amount of information returned. Similar constraints are expected in future NASA missions. For instance, gas chromatographic instrumentation is being developed to collect and analyze organic gases and aerosols in the atmosphere of Titan (one of Saturn's satellites). The Titan

  2. From 1D and 2D ZnO nanostructures to 3D hierarchical structures with enhanced gas sensing properties.

    PubMed

    Alenezi, Mohammad R; Henley, Simon J; Emerson, Neil G; Silva, S Ravi P

    2014-01-07

    Facile and low cost hydrothermal routes are developed to fabricate three-dimensional (3D) hierarchical ZnO structures with high surface-to-volume ratios and an increased fraction of (0001) polar surfaces. Hierarchical ZnO nanowires (ZNWs) and nanodisks (ZNDs) assembled from initial ZnO nanostructures are prepared from sequential nucleation and growth following a hydrothermal process. These hierarchical ZnO structures display an enhancement of gas sensing performance and exhibit significantly improved sensitivity and fast response to acetone in comparison to other mono-morphological ZnO, such as nanoparticles, NWs, or NDs. In addition to the high surface-to-volume ratio due to its small size, the nanowire building blocks show the enhanced gas sensing properties mainly ascribed to the increased proportion of exposed active (0001) planes, and the formation of many nanojunctions at the interface between the initial ZnO nanostructure and secondary NWs. This work provides the route for structure induced enhancement of gas sensing performance by designing a desirable nanostructure, which could also be extended to synthesize other metal oxide nanostructures with superior gas sensing performance.

  3. Communication: two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): simultaneous planar imaging and multiplex spectroscopy in a single laser shot.

    PubMed

    Bohlin, Alexis; Kliewer, Christopher J

    2013-06-14

    Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the high efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15,000 spatially correlated rotational CARS spectra in N2 and air over a 2D field of 40 mm(2).

  4. Communication: Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): Simultaneous planar imaging and multiplex spectroscopy in a single laser shot

    NASA Astrophysics Data System (ADS)

    Bohlin, Alexis; Kliewer, Christopher J.

    2013-06-01

    Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the high efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15 000 spatially correlated rotational CARS spectra in N2 and air over a 2D field of 40 mm2.

  5. Communication: Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): Simultaneous planar imaging and multiplex spectroscopy in a single laser shot

    SciTech Connect

    Bohlin, Alexis; Kliewer, Christopher J.

    2013-01-01

    Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the high efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15, 000 spatially correlated rotational CARS spectra in N2 and air over a 2D field of 40 mm2.

  6. Adsorption and displacement effects in the gas-chromatography of metal beta-diketonates.

    PubMed

    Uden, P C; Jenkins, C R

    1969-07-01

    A detailed study of the gas chromatography of the aluminium(III), chromium(III) and iron(III) beta-diketonates has shown that their elution and separation characteristics arise from a number of adsorptive effects. Conditions of optimal peak shape for individual compounds are established by varying Chromatographie parameters, and the adsorption of one metal chelate on a column and its subsequent displacement by another chelate are investigated. The chromatography of iron(III) beta-diketonates is seen to be further complicated by gradual elution of a portion of the chelate before the rest of the sample.

  7. NEW SCX PEPTIDE ELUTION SCORE FOR PH/SALT-GRADIENT SCX CHROMATOGRAPHY IN 2D-NANO-LC/MSMS ANALYSIS OF PROTEIN DIGESTS

    EPA Science Inventory

    A new automated 2D-(SCX/RP)-nano-LC/MSMS method was developed. Separation of the peptides in the first LC dimension was the main focus of this work, and it was optimized using human serum albumin (HSA) and human lung cell lysate tryptic digests. Samples were reduced and alkylated...

  8. Confirmation of cannabinoids in meconium using two-dimensional gas chromatography with mass spectrometry detection.

    PubMed

    Marin, Stephanie J; Coles, Rebecka; Urry, Francis M; McMillin, Gwendolyn A

    2007-10-15

    Meconium has become the specimen of choice for determining fetal exposure to drugs of abuse, but its physical complexity can cause interferences from matrix effects. A new method to determine 9-carboxy-11-nor-Delta(9)-THC (9-THCA) and 11-hydroxy-Delta(9)-THC (11-OH-THC) using two-dimensional (2D) GC-MS was developed to reduce interferences and carryover. The method was validated using 70 spiked samples prepared in drug-free meconium and 46 residual patient specimens that were confirmed to contain cannabinoids. Ten patient specimens that failed to confirm due to interferences using the previous GC-MS method were analyzed using the new 2D method and 9-THCA was quantitated in all ten samples. The 2D GC-MS method improved chromatography which significantly reduced interferences and carryover when compared to the previous GC-MS method.

  9. Application of gas chromatography to analysis of spirit-based alcoholic beverages.

    PubMed

    Wiśniewska, Paulina; Śliwińska, Magdalena; Dymerski, Tomasz; Wardencki, Waldemar; Namieśnik, Jacek

    2015-01-01

    Spirit-based beverages are alcoholic drinks; their production processes are dependent on the type and origin of raw materials. The composition of this complex matrix is difficult to analyze, and scientists commonly choose gas chromatography techniques for this reason. With a wide selection of extraction methods and detectors it is possible to provide qualitative and quantitative analysis for many chemical compounds with various functional groups. This article describes different types of gas chromatography techniques and their most commonly used associated extraction techniques (e.g., LLE, SPME, SPE, SFE, and SBME) and detectors (MS, TOFMS, FID, ECD, NPD, AED, O or EPD). Additionally, brief characteristics of internationally popular spirit-based beverages and application of gas chromatography to the analysis of selected alcoholic drinks are presented.

  10. 2D numerical modelling of gas temperature in a nanosecond pulsed longitudinal He-SrBr2 discharge excited in a high temperature gas-discharge tube for the high-power strontium laser

    NASA Astrophysics Data System (ADS)

    Chernogorova, T. P.; Temelkov, K. A.; Koleva, N. K.; Vuchkov, N. K.

    2016-05-01

    An active volume scaling in bore and length of a Sr atom laser excited in a nanosecond pulse longitudinal He-SrBr2 discharge is carried out. Considering axial symmetry and uniform power input, a 2D model (r, z) is developed by numerical methods for determination of gas temperature in a new large-volume high-temperature discharge tube with additional incompact ZrO2 insulation in the discharge free zone, in order to find out the optimal thermal mode for achievement of maximal output laser parameters. A 2D model (r, z) of gas temperature is developed by numerical methods for axial symmetry and uniform power input. The model determines gas temperature of nanosecond pulsed longitudinal discharge in helium with small additives of strontium and bromine.

  11. Toward a definition of blueprint of virgin olive oil by comprehensive two-dimensional gas chromatography.

    PubMed

    Purcaro, Giorgia; Cordero, Chiara; Liberto, Erica; Bicchi, Carlo; Conte, Lanfranco S

    2014-03-21

    This study investigates the applicability of an iterative approach aimed at defining a chemical blueprint of virgin olive oil volatiles to be correlated to the product sensory quality. The investigation strategy proposed allows to fully exploit the informative content of a comprehensive multidimensional gas chromatography (GC×GC) coupled to a mass spectrometry (MS) data set. Olive oil samples (19), including 5 reference standards, obtained from the International Olive Oil Council, and commercial samples, were submitted to a sensory evaluation by a Panel test, before being analyzed in two laboratories using different instrumentation, column set, and software elaboration packages in view of a cross-validation of the entire methodology. A first classification of samples based on untargeted peak features information, was obtained on raw data from two different column combinations (apolar×polar and polar×apolar) by applying unsupervised multivariate analysis (i.e., principal component analysis-PCA). However, to improve effectiveness and specificity of this classification, peak features were reliably identified (261 compounds), on the basis of the MS spectrum and linear retention index matching, and subjected to successive pair-wise comparisons based on 2D patterns, which revealed peculiar distribution of chemicals correlated with samples sensory classification. The most informative compounds were thus identified and collected in a "blueprint" of specific defects (or combination of defects) successively adopted to discriminate Extra Virgin from defected oils (i.e., lampante oil) with the aid of a supervised approach, i.e., partial least squares-discriminant analysis (PLS-DA). In this last step, the principles of sensomics, which assigns higher information potential to analytes with lower odor threshold proved to be successful, and a much more powerful discrimination of samples was obtained in view of a sensory quality assessment.

  12. Characterization of aroma-active compounds in three Chinese Moutai liquors by gas chromatography-olfactometry, gas chromatography-mass spectrometry and sensory evaluation.

    PubMed

    Niu, Yunwei; Chen, Xiaomei; Xiao, Zuobing; Ma, Ning; Zhu, Jiancai

    2017-04-01

    The aroma-active compounds in three Chinese Moutai liquors, aged 1 year, 15 years and 30 years were investigated in this study. The aroma compounds were analysed by gas chromatography-olfactometry (GC-O) coupled with gas chromatography-mass spectrometry (GC-MS). A total of 79 aroma compounds were identified. Aroma extract dilution analysis (AEDA) was further employed to identify the aroma-active compounds. A total of 35 aroma-active compounds with flavour dilution (FD) values ≧ 64 simultaneously in three Chinese Moutai liquors were quantitated. Among them, ethyl acetate, ethyl lactate and acetic acid appeared with the highest concentrations. They were all >1000 mg/L. Then, the relationships between the aroma-active compounds and seven sensory attributes were studied.

  13. Qualitative and quantitative analysis of vetiver essential oils by comprehensive two-dimensional gas chromatography and comprehensive two-dimensional gas chromatography/mass spectrometry.

    PubMed

    Filippi, Jean-Jacques; Belhassen, Emilie; Baldovini, Nicolas; Brevard, Hugues; Meierhenrich, Uwe J

    2013-05-03

    Vetiver essential oils (VEO) are important raw ingredients used in perfume industry, entering the formula of numerous modern fragrances. Vetiver oils are considered to be among the most complex essential oils, resulting most of the time in highly coeluted chromatograms whatever the analytical technique. In this context, conventional gas chromatography has failed to provide a routine tool for the accurate qualitative and quantitative analysis of their constituents. Applying comprehensive two-dimensional gas chromatography techniques (GC×GC-FID/MS) afforded the mean to separate efficiently vetiver oil constituents in order to identify them in a more reliable way. Moreover, this is the first time that a complete true quantitation of each constituent is carried out on such complex oils by means of internal calibration. Finally, we have studied the influence of the injection mode on the determined chemical composition, and showed that several alcohols underwent dehydration under defined chromatographic conditions (splitless mode) usually recommended for quantitation purposes.

  14. Determination of parts-per-billion concentrations of dioxane in water and soil by purge and trap gas chromatography/mass spectrometry or charcoal tube enrichment gas chromatography

    SciTech Connect

    Epstein, P.S.; Mauer, T.; Wagner, M.; Chase, S.; Giles, B.

    1987-08-01

    Two methods for the determination of 1,4-dioxane in water have been studied. The first method is a heated purge and trap gas chromatography/mass spectrometry system following salting out with sodium sulfate. The second method is an adsorption on coconut-shell charcoal and solvent desorption with carbon disulfide/methanol followed by analysis of the desorbate by gas chromatography with flame ionization detection. The first method is also successful for the determination of 1,4-dioxane in solids and sediments. The second method is shown to be successful for 2-butanone, 4-methyl-2-pentanone, and butoxyethanol in water. The two methods are compared by analyzing 15 samples by both methods and achieving similar results.

  15. Analyzing salvia divinorum and its active ingredient salvinorin a utilizing thin layer chromatography and gas chromatography/mass spectrometry.

    PubMed

    Jermain, John D; Evans, Hiram K

    2009-05-01

    In recent years, Salvia divinorum has become a major focus by state legislatures throughout the United States looking to prohibit the sale of the psychoactive plant. After researching testing procedures presented in the literature and those employed by crime laboratories throughout the country, it was decided that thin layer chromatography (TLC) and gas chromatography/mass spectrometry (GC/MS) were the methods to use to analyze plant material for salvinorin A. With TLC, salvinorin A was detected from extracted plant material and was easily distinguishable from 13 other Salvia species as well as Cannabis sativa L. (marijuana). When using GC/MS, salvinorin A was best extracted from plant material with chloroform at ambient temperature when using a nonpolar solvent and acetone at ambient temperature when using a polar solvent. By utilizing these techniques, criminalists are now able to confirm the presence of salvinorin A in a submitted plant material suspected to be Salvia divinorum.

  16. Identification of Explosives from Porous Materials: Applications Using Reverse Phase High Performance Liquid Chromatography and Gas Chromatography

    SciTech Connect

    C.J. Miller; G. Elias; N.C. Schmitt; C. Rae

    2010-06-01

    High performance liquid chromatography and gas chromatography techniques are well documented and widely used for the detection of trace explosives from organic solvents. These techniques were modified to specifically identify and quantify explosives extracted from various materials taken from people who had recently handled explosives. Documented techniques were modified to specifically detect and quantify RDX, TNT, and PETN from denim, colored flannel, vinyl, and canvas extracted in methanol using no sample cleanup prior to analysis. The methanol extracts were injected directly into several different column types and analyzed by HPLC-UV and/or GC-ECD. This paper describes general screening methods that were used to determine the presence of explosives in unknown samples and techniques that have been optimized for quantification of each explosive from the substrate extracts.

  17. Pyrolysis-gas chromatography-mass spectrometry of a series of bile acid sequestrants.

    PubMed

    Haskins, N J; Eckers, C; Mitchell, R

    1992-09-01

    Pyrolysis of a series of polymers based on polystyrene and used as bile acid sequestrants produced characteristic mixtures of compounds which were analysed by gas chromatography-mass spectrometry. The nature of the substituent groups was clearly apparent while the polymer backbone gave rise to representative styrenes. The reproducibility of the results was examined by experimenting with the temperature of pyrolysis. It was found that at low temperatures very little fragmentation of the polystyrene backbone occurred but the substituents were still released in high yield. The orientation of the various substituted styrenes generated by pyrolysis was confirmed by the use of gas chromatography with infrared and mass spectrometric detection.

  18. Radiation-induced resistance oscillations in a 2D hole gas: a demonstration of a universal effect

    NASA Astrophysics Data System (ADS)

    Iñarrea, Jesús; Platero, Gloria

    2015-09-01

    We report on a theoretical study about the microwave-induced resistance oscillations and zero resistance states when dealing with p-type semiconductors and holes instead of electrons. We consider a high-mobility two-dimensional hole gas hosted in a pure Ge/SiGe quantum well. Similarly to electrons we obtain radiation-induced resistance oscillations and zero resistance states. We analytically deduce a universal expression for the irradiated magnetoresistance, explaining the origin of the minima positions and their 1/4 cycle phase shift. The outcome is that these phenomena are universal and only depend on radiation and cyclotron frequencies. We also study the possibility of having simultaneously two different carriers driven by radiation: light and heavy holes. As a result the calculated magnetoresistance reveals an interference profile due to the different effective masses of the two types of carriers.

  19. An Excel(®)-based visualization tool of 2-D soil gas concentration profiles in petroleum vapor intrusion.

    PubMed

    Verginelli, Iason; Yao, Yijun; Suuberg, Eric M

    2016-01-01

    In this study we present a petroleum vapor intrusion tool implemented in Microsoft(®) Excel(®) using Visual Basic for Applications (VBA) and integrated within a graphical interface. The latter helps users easily visualize two-dimensional soil gas concentration profiles and indoor concentrations as a function of site-specific conditions such as source strength and depth, biodegradation reaction rate constant, soil characteristics and building features. This tool is based on a two-dimensional explicit analytical model that combines steady-state diffusion-dominated vapor transport in a homogeneous soil with a piecewise first-order aerobic biodegradation model, in which rate is limited by oxygen availability. As recommended in the recently released United States Environmental Protection Agency's final Petroleum Vapor Intrusion guidance, a sensitivity analysis and a simplified Monte Carlo uncertainty analysis are also included in the spreadsheet.

  20. Insights into the growth rate of spatially evolving plane turbulent free-shear layers from 2D vortex-gas simulations

    NASA Astrophysics Data System (ADS)

    Suryanarayanan, Saikishan; Narasimha, Roddam

    2017-02-01

    Although the free-shear or mixing layer has been a subject of extensive research over nearly a century, there are certain fundamental issues that remain controversial. These include the influence of initial and downstream conditions on the flow, the effect of velocity ratio across the layer, and the nature of any possible coupling between small scale dynamics and the large scale evolution of layer thickness. In the spirit of the temporal vortex-gas simulations of Suryanarayanan et al. ["Free turbulent shear layer in a point vortex gas as a problem in nonequilibrium statistical mechanics," Phys. Rev. E 89, 013009 (2014)], we revisit the simple 2D inviscid vortex-gas model with extensive computations and detailed analysis, in order to gain insights into some of the above issues. Simulations of the spatially evolving vortex-gas shear layer are carried out at different velocity ratios using a computational model based on the work of Basu et al. ["Vortex sheet simulation of a plane canonical mixing layer," Comput. Fluids 21, 1-30 (1992) and "Modelling plane mixing layers using vortex points and sheets," Appl. Math. Modell. 19, 66-75 (1995)], but with a crucial improvement that ensures conservation of global circulation. The simulations show that the conditions imposed at the origin of the free shear layer and at the exit to the computational domain can affect flow evolution in their respective downstream and upstream neighbourhoods, the latter being particularly strong in the single stream limit. In between these neighbourhoods at the ends is a regime of universal self-preserving growth rate given by a universal function of velocity ratio. The computed growth rates are generally located within the scatter of experimental data on plane mixing layers and closely agree with recent high Reynolds number experiments and 3D large eddy simulation studies. These findings support the view that observed free-shear layer growth can be largely explained by the 2D vortex dynamics of

  1. XCIII. A Low-Cost Temperature Programmer for Gas Chromatography

    ERIC Educational Resources Information Center

    Gallaher, T. N.; And Others

    1977-01-01

    Describes the construction and operation of a temperature programmer; it can be built for less than $100 and can be used with any gas chromatograph that uses a variable resistor to control oven temperature. (MLH)

  2. Trace hydrazines in aqueous solutions accurately determined by gas chromatography

    NASA Technical Reports Server (NTRS)

    Welz, E. A., Jr.

    1967-01-01

    Trace amounts of hydrazines in aqueous solutions can be determined by using polythyleneimine /PEI/ in conjunction with the gas chromatographic column. The PEI specifically retains water without altering the separability or elution order of the hydrazine and associated constituents.

  3. Measuring Carbon Monoxide in Auto Exhaust by Gas Chromatography.

    ERIC Educational Resources Information Center

    Jaffe, Dan; Herndon, Scott

    1995-01-01

    Presents a simple and reliable technique using commonly available equipment for monitoring carbon monoxide in automobile exhaust. The experiment utilizes a gas chromatograph and a thermal conductivity detector (TCD). (DDR)

  4. Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

    NASA Astrophysics Data System (ADS)

    Morrison, C.; Casteleiro, C.; Leadley, D. R.; Myronov, M.

    2016-09-01

    The complex quantum transport of a strained Ge quantum well (QW) modulation doped heterostructure with two types of mobile carriers has been observed. The two dimensional hole gas (2DHG) in the Ge QW exhibits an exceptionally high mobility of 780 000 cm2/Vs at temperatures below 10 K. Through analysis of Shubnikov de-Haas oscillations in the magnetoresistance of this 2DHG below 2 K, the hole effective mass is found to be 0.065 m0. Anomalous conductance peaks are observed at higher fields which deviate from standard Shubnikov de-Haas and quantum Hall effect behaviour due to conduction via multiple carrier types. Despite this complex behaviour, analysis using a transport model with two conductive channels explains this behaviour and allows key physical parameters such as the carrier effective mass, transport, and quantum lifetimes and conductivity of the electrically active layers to be extracted. This finding is important for electronic device applications, since inclusion of highly doped interlayers which are electrically active, for enhancement of, for example, room temperature carrier mobility, does not prevent analysis of quantum transport in a QW.

  5. Advancement and application of gas chromatography isotope ratio mass spectrometry techniques for atmospheric trace gas analysis

    NASA Astrophysics Data System (ADS)

    Giebel, Brian M.

    2011-12-01

    The use of gas chromatography isotope ratio mass spectrometry (GC-IRMS) for compound specific stable isotope analysis is an underutilized technique because of the complexity of the instrumentation and high analytical costs. However stable isotopic data, when coupled with concentration measurements, can provide additional information on a compounds production, transformation, loss, and cycling within the biosphere and atmosphere. A GC-IRMS system was developed to accurately and precisely measure delta13C values for numerous oxygenated volatile organic compounds having natural and anthropogenic sources. The OVOCs include methanol, ethanol, acetone, methyl ethyl ketone, 2-pentanone, and 3-pentanone. Guided by the requirements for analysis of trace components in air, the GC-IRMS system was developed with the goals of increasing sensitivity, reducing dead-volume and peak band broadening, optimizing combustion and water removal, and decreasing the split ratio to the IRMS. The technique relied on a two-stage preconcentration system, a low-volume capillary reactor and water trap, and a balanced reference gas delivery system. Measurements were performed on samples collected from two distinct sources (i.e. biogenic and vehicle emissions) and ambient air collected from downtown Miami and Everglades National Park. However, the instrumentation and the method have the capability to analyze a variety of source and ambient samples. The measured isotopic signatures that were obtained from source and ambient samples provide a new isotopic constraint for atmospheric chemists and can serve as a new way to evaluate their models and budgets for many OVOCs. In almost all cases, OVOCs emitted from fuel combustion were enriched in 13C when compared to the natural emissions of plants. This was particularly true for ethanol gas emitted in vehicle exhaust, which was observed to have a uniquely enriched isotopic signature that was attributed to ethanol's corn origin and use as an alternative

  6. A nonlinear dynamical 2D coupled mathematical model for phase transitions in methane gas hydrates within permafrost under climate change

    NASA Astrophysics Data System (ADS)

    Duxbury, N. S.; Romanovsky, V. E.; Romanovskii, N. N.; Garagulya, L. S.; Brouchkov, A. V.; Komarov, I. A.; Roman, L. T.; Tipenko, G. S.; Buldovich, S. N.; Maximova, L. N.

    2012-12-01

    We have developed coupled permafrost - carbon physical and numerical models, where carbon is in the form of methane clathrate hydrate ( CH4*6H2O ) in a porous subsurface environment. The driving force for the subsurface temperature field dynamics is climate variations on the Earth's surface. This is an upper boundary condition for the nonlinear evolutionary system of partial differential equations (PDEs) describing subsurface heat transfer (parabolic PDEs) in a generalized Stefan formulation. The developed numerical model is a valuable computational tool to quantitatively study nonlinear dynamical thermal processes with phase transitions in terrestrial and Martian subsurfaces. Our model is multifrontal and therefore allows one to perform computations for a problem with any number of emerging/vanishing phase transition interfaces (both in methane gas hydrate deposits and in permafrost), since the model treats these fronts implicitly in an enthalpy formulation and in corresponding finite-difference scheme. This model takes into account the pressure (and therefore the depth) dependence of the phase transition temperature for methane clathrate hydrate. We have performed model computations using the thermophysical characteristics (heat capacity, density/porosity, thermal conductivity) for the Siberian subsurface. It can be used as a terrestrial analog for the Martian subsurface (e.g., Duxbury et al., 2001). Also, thermophysical coefficients from laboratory experiments for methane clathrate hydrate were used in our model. In addition, our model takes into account the dependence of subsurface thermophysical characteristics on temperature and spatial coordinates. The results of our computations and their interpretation will be presented. References. N. S. Duxbury, I. A. Zotikov, K. H. Nealson, V. E. Romanovsky, F. D. Carsey (2001). A numerical model for an alternative origin of Lake Vostok and its exobiological implications for Mars, Journal of Geophysical Research

  7. Determination of Dihydroqinghaosu in Blood by Pyrolysis Gas Chromatography/Mass Spectrometry

    DTIC Science & Technology

    1988-01-15

    capillary the therapeutic range, our laboratory sought to develop new column gas chromatography/mass spectrometry ( GCMS ) specific and sensitive methodologies...paper, the results on the development and validation of packed for pharmacoklneUc an metabolism studies In animals. and capillary column gas...respectively. Petroleum ether washave been treated with QHS or its derivatives in China with purchased from Mallinckrodt, Inc. (Paris, KY), and ethyl acetate

  8. Recent progress of chiral stationary phases for separation of enantiomers in gas chromatography.

    PubMed

    Xie, Sheng-Ming; Yuan, Li-Ming

    2017-01-01

    Chromatography techniques based on chiral stationary phases are widely used for the separation of enantiomers. In particular, gas chromatography has developed rapidly in recent years due to its merits such as fast analysis speed, lower consumption of stationary phases and analytes, higher column efficiency, making it a better choice for chiral separation in diverse industries. This article summarizes recent progress of novel chiral stationary phases based on cyclofructan derivatives and chiral porous materials including chiral metal-organic frameworks, chiral porous organic frameworks, chiral inorganic mesoporous materials, and chiral porous organic cages in gas chromatography, covering original research papers published since 2010. The chiral recognition properties and mechanisms of separation toward enantiomers are also introduced.

  9. Hyphenated and comprehensive liquid chromatography × gas chromatography-mass spectrometry for the identification of Mycobacterium tuberculosis.

    PubMed

    Mourão, Marta P B; Denekamp, Ilse; Kuijper, Sjoukje; Kolk, Arend H J; Janssen, Hans-Gerd

    2016-03-25

    Tuberculosis is one of the world's most emerging public health problems, particularly in developing countries. Chromatography based methods have been used to tackle this epidemic by focusing on biomarker detection. Unfortunately, interferences from lipids in the sputum matrix, particularly cholesterol, adversely affect the identification and detection of the marker compounds. The present contribution describes the serial combination of normal phase liquid chromatography (NPLC) with thermally assisted hydrolysis and methylation followed by gas chromatography-mass spectrometry (THM-GC-MS) to overcome the difficulties of biomarker evaluation. The in-series combination consists of an LC analysis where fractions are collected and then transferred to the THM-GC-MS system. This was either done with comprehensive coupling, transferring all the fractions, or with hyphenated interfacing, i.e. off-line multi heart-cutting, transferring only selected fractions. Owing to the high sensitivity and selectivity of LC as a sample pre-treatment method, and to the high specificity of the MS as a detector, this analytical approach, NPLC × THM-GC-MS, is extremely sensitive. The results obtained indicate that this analytical set-up is able to detect down to 1 × 10(3) mycobacteria/mL of Mycobacterium tuberculosis strain 124, spiked in blank sputum samples. It is a powerful analytical tool and also has great potential for full automation. If further studies demonstrate its usefulness when applied blind in real sputum specimens, this technique could compete with the current smear microscopy in the early diagnosis of tuberculosis.

  10. High-voltage spark atomic emission detector for gas chromatography

    NASA Technical Reports Server (NTRS)

    Calkin, C. L.; Koeplin, S. M.; Crouch, S. R.

    1982-01-01

    A dc-powered, double-gap, miniature nanosecond spark source for emission spectrochemical analysis of gas chromatographic effluents is described. The spark is formed between two thoriated tungsten electrodes by the discharge of a coaxial capacitor. The spark detector is coupled to the gas chromatograph by a heated transfer line. The gas chromatographic effluent is introduced into the heated spark chamber where atomization and excitation of the effluent occurs upon breakdown of the analytical gap. A microcomputer-controlled data acquisition system allows the implementation of time-resolution techniques to distinguish between the analyte emission and the background continuum produced by the spark discharge. Multiple sparks are computer averaged to improve the signal-to-noise ratio. The application of the spark detector for element-selective detection of metals and nonmetals is reported.

  11. Multicomponent, 3-D, and High-Resolution 2-D Seismic Characterization of Gas Hydrate Study Sites in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Haines, S. S.; Hart, P. E.; Ruppel, C. D.; Collett, T. S.; Shedd, W.; Lee, M. W.; Miller, J.

    2012-12-01

    High saturations of gas hydrates have been identified within coarse-grained sediments in the Green Canyon 955 and Walker Ridge 313 lease blocks of the deepwater northern Gulf of Mexico. The thickness, lateral extent, and hydrate saturations in these deposits are constrained by geological and geophysical data and state-of-the-art logging-while-drilling information obtained in multiple boreholes at each site during a 2009 expedition. Presently lacking are multicomponent seismic data that can provide a thorough understanding of the in-situ compressional and shear seismic properties of the hydrate-bearing sediments. Such data may represent an important tool for future characterization of gas hydrate resources. To address this data gap, the U.S. Geological Survey, the U.S. Department of Energy, and the Bureau of Ocean Energy Management will collaborate on a 20-day research expedition to acquire wide-angle ocean bottom seismometer and high-resolution vertical incidence 2-D seismic data at the study sites. In preparation for this mid-2013 expedition, we have analyzed existing industry 3-D seismic data, along with numerically modeled multicomponent data. The 3-D seismic data allow us to identify and rank specific survey targets and can be combined with the numerical modeling results to determine optimal survey line orientation and acquisition parameters. Together, these data also provide a more thorough understanding of the gas hydrate systems at these two sites.

  12. A multivariate statistical analysis approach to analyze gas chromatography-olfactometry data of tangerine hybrids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gas chromatography (GC) hyphenated with olfactometry (O) when a human subject smells the effluent of the GC is a useful technique to identify aroma activity of volatile compounds in a food. Many techniques have been developed, based on olfactory thresholds (CHARM analysis, AEDA), or based on psychop...

  13. Qualitative Analysis by Gas Chromatography: GC versus the Nose in Formulating Artificial Fruit Flavors.

    ERIC Educational Resources Information Center

    Rasmussen, P. W.

    1984-01-01

    Describes an undergraduate laboratory experiment used to illustrate the use of gas chromatography retention indices for the identification of unknown compounds, specifically for the identification of unknown compounds and for the identification of the volatile compounds responsible for the odor of the banana. Procedures, reference data, and sample…

  14. A Gas Chromatography Experiment for Proving the Application of Quantum Symmetry Restrictions in Homonuclear Diatomic Molecules.

    ERIC Educational Resources Information Center

    Dosiere, M.

    1985-01-01

    Background information, procedures used, and typical results obtained are provided for an experiment in which gas chromatography is used to prove the application of quantum symmetry restrictions in homonuclear diatomic molecules. Comparisons between experimental results and theoretical computed values show good agreement, within one to two…

  15. The Separation and Identification of Straight Chain Hydrocarbons: An Experiment Using Gas-Liquid Chromatography.

    ERIC Educational Resources Information Center

    Benson, G. A.

    1982-01-01

    An experiment using gas-liquid chromatography is discussed, introducing the student to concept of dead volume and its measurement, idea and use of an internal reference compound, and to linear relationship existing between measurements of a separation on two different stationary phases. (Author/SK)

  16. The determination of cyclohexylamine in aqueous solutions of sodium cyclamate by electron-capture gas chromatography.

    NASA Technical Reports Server (NTRS)

    Solomon, M. D.; Pereira, W. E.; Duffield, A. M.

    1971-01-01

    A sensitive primary amine assay, capable of detecting 10 to the minus 11th g and utilizing the determination of the amine N-2,4-dinitrophenyl derivative by electron-capture gas chromatography is described. The method is exemplified by the determination of cyclohexylamine in sodium cyclamate.

  17. An Application of Trimethylsilyl Derivatives with Temperature Programmed Gas Chromatography to the Senior Analytical Laboratory.

    ERIC Educational Resources Information Center

    Kelter, Paul B.; Carr, James D.

    1983-01-01

    Describes an experiment designed to teach temperature programed gas chromatography (TPGC) techniques and importance of derivatizing many classes of substrated to be separated. Includes equipment needed, procedures for making trimethylsilyl derivatives, applications, sample calculations, and typical results. Procedure required one, three-hour…

  18. Tracking the Weathering of an Oil Spill with Comprehensive Two-Dimensional Gas Chromatography

    DTIC Science & Technology

    2006-01-01

    15275920500506758 Tracking the Weathering of an Oil Spill with Comprehensive Two-Dimensional Gas Chromatography Robert K. Nelson,1 Brian M. Kile ,1 Desiree L. Plata,1...Robert T. Alexander Trust. Brian M. Kile received support from the National Science Foundation’s Research Experience for Undergraduates program while a

  19. Planar gas chromatography column on aluminum plate with multi-walled carbon nanotubes as stationary phase

    NASA Astrophysics Data System (ADS)

    Platonov, I. A.; Platonov, V. I.; Pavelyev, V. S.

    2016-04-01

    The high selectivity of the adsorption layer for low-boiling alkanes is shown, the separation factor (α) couple iso-butane / butane is 1.9 at a column temperature of 50 °C.The paper presents sorption and selective properties of planar gas chromatography column on aluminum plate with multi-walled carbon nanotubes as the stationary phase.

  20. DEVELOPMENTS IN DIRECT THERMAL EXTRACTION GAS CHROMATOGRAPHY-MASS SPECTROMETRY OF FINE AEROSOLS

    EPA Science Inventory

    This examines thermal extraction gas chromatography-mass spectrometry (TE/GC/MS) applied to aerosols collected on filters. Several different TE/GC/MS systems as a group have speciated hundreds of individual organic constituents in ambient fine aerosols. Molecular marker source ap...

  1. Review of recent developments and applications in low-pressure (vacuum outlet) gas chromatography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The concept of low pressure (LP) vacuum outlet gas chromatography (GC) was introduced more than 50 years ago, but it was not until the 2000s that its theoretical applicability to fast analysis of GC-amenable chemicals was realized. In practice, LPGC is implemented by placing the outlet of a short, ...

  2. Incorporation of Gas Chromatography-Mass Spectrometry into the Undergraduate Organic Chemistry Laboratory Curriculum

    ERIC Educational Resources Information Center

    Giarikos, Dimitrios G.; Patel, Sagir; Lister, Andrew; Razeghifard, Reza

    2013-01-01

    Gas chromatography-mass spectrometry (GC-MS) is a powerful analytical tool for detection, identification, and quantification of many volatile organic compounds. However, many colleges and universities have not fully incorporated this technique into undergraduate teaching laboratories despite its wide application and ease of use in organic…

  3. Quantitation of monomers in poly(glyerol-co-diacid) gels using gas chromatography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The validation of a gas chromatography (GC) method developed to quantify amounts of starting material from the synthesis of hyperbranched polymers made from glycerol and either succinic acid, glutaric acid, or azelaic acid is described. The GC response to concentration was linear for all starting r...

  4. Identification of Synthetic Polymers and Copolymers by Analytical Pyrolysis-Gas Chromatography/Mass Spectrometry

    ERIC Educational Resources Information Center

    Kusch, Peter

    2014-01-01

    An experiment for the identification of synthetic polymers and copolymers by analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was developed and performed in the polymer analysis courses for third-year undergraduate students of chemistry with material sciences, and for first-year postgraduate students of polymer sciences. In…

  5. Analysis of Microorganisms by Oxidative and Non-Oxidative Pyrolysis Gas Chromatography Ion Trap Mass Spectrometry.

    DTIC Science & Technology

    1992-04-01

    Bacillus subtilis, Bacillus pumilus , Bacillus lichenformis, and Bacillus amyloliquefaciens by Pyrolysis-gas Liquid Chromatography, Deoxyribonucleic...FIGURES Number Page 1. Curie point pyrolysis GC-ITD data for Bacillus subtilis ................... 16 2. Total Ion Chromatograms for Bacillus subtilis...under oxidative and non-oxidative pyrolysis conditions ................................... 17 3. Total Lipid Mass Spectra for Bacillus subtilis under

  6. SnO2 quantum dots and quantum wires: controllable synthesis, self-assembled 2D architectures, and gas-sensing properties.

    PubMed

    Xu, Xiangxing; Zhuang, Jing; Wang, Xun

    2008-09-17

    SnO2 quantum dots (QDs) and ultrathin nanowires (NWs) with diameters of approximately 0.5-2.5 and approximately 1.5-4.5 nm, respectively, were controllably synthesized in a simple solution system. They are supposed to be ideal models for studying the continuous evolution of the quantum-confinement effect in SnO2 1D --> 0D systems. The observed transition from strong to weak quantum confinement in SnO2 QDs and ultrathin NWs is interpreted through the use of the Brus effective-mass approximation and the Nosaka finite-depth well model. Photoluminescence properties that were coinfluenced by size effects, defects (oxygen vacancies), and surface capping are discussed in detail. With the SnO2 QDs as building blocks, various 2D porous structures with ordered hexagonal, distorted hexagonal, and square patterns were prepared on silicon-wafer surfaces and exhibited optical features of 2D photonic crystals and enhanced gas sensitivity.

  7. 1-kHz two-dimensional coherent anti-Stokes Raman scattering (2D-CARS) for gas-phase thermometry.

    PubMed

    Miller, Joseph D; Slipchenko, Mikhail N; Mance, Jason G; Roy, Sukesh; Gord, James R

    2016-10-31

    Two-dimensional gas-phase coherent anti-Stokes Raman scattering (2D-CARS) thermometry is demonstrated at 1 kHz in a heated jet. A hybrid femtosecond/picosecond CARS configuration is used in a two-beam phase-matching arrangement with a 100-femtosecond pump/Stokes pulse and a 107-picosecond probe pulse. The femtosecond pulse is generated using a mode-locked oscillator and regenerative amplifier that is synchronized to a separate picosecond oscillator and burst-mode amplifier. The CARS signal is spectrally dispersed in a custom imaging spectrometer and detected using a high-speed camera with image intensifier. 1-kHz, single-shot planar measurements at room temperature exhibit error of 2.6% and shot-to-shot variations of 2.6%. The spatial variation in measured temperature is 9.4%. 2D-CARS temperature measurements are demonstrated in a heated O2 jet to capture the spatiotemporal evolution of the temperature field.

  8. Process gas chromatography study of a Selexol acid gas removal system. Final report Mar-Sep 82

    SciTech Connect

    Williams, W.A.

    1984-01-01

    The report gives results of continuous compositional monitoring by process gas chromatography (GC) for three gas streams associated with the Selexol acid gas removal system at the Bi-Gas pilot plant in Homer City, PA. Data were obtained from the inlet and outlet streams of the Selexol system during tests in April and May 1982. Product gas composition data were logged for 55 hours of plant operation. The Bi-Gas pilot plant, utilizing a two-stage, entrained-bed, high-pressure slagging gasifier, produces a product gas that is low in tars and heavy oils. This gas stream required very little cleanup prior to instrumental analysis. However, some problems were encountered in the analysis of the Selexol acid gas stream due to the presence of high levels of naphthalene. The process gas chromatographs performed well and remained very stable during the tests. Material balances based on GC analyses and process flow rate data show a high degree of material accountability. The H/sub 2/S removal efficiency of the Selexol absorber was about 99% during the tests.

  9. Atmospheric pressure helium afterglow discharge detector for gas chromatography

    DOEpatents

    Rice, Gary; D'Silva, Arthur P.; Fassel, Velmer A.

    1986-05-06

    An apparatus for providing a simple, low-frequency electrodeless discharge system for atmospheric pressure afterglow generation. A single quartz tube through which a gas mixture is passed is extended beyond a concentric electrode positioned thereabout. A grounding rod is placed directly above the tube outlet to permit optical viewing of the discharge between the electrodes.

  10. Position sensitive radioactivity detection for gas and liquid chromatography

    DOEpatents

    Cochran, Joseph L.; McCarthy, John F.; Palumbo, Anthony V.; Phelps, Tommy J.

    2001-01-01

    A method and apparatus are provided for the position sensitive detection of radioactivity in a fluid stream, particularly in the effluent fluid stream from a gas or liquid chromatographic instrument. The invention represents a significant advance in efficiency and cost reduction compared with current efforts.

  11. Atmospheric pressure helium afterglow discharge detector for gas chromatography

    DOEpatents

    Rice, G.; D'Silva, A.P.; Fassel, V.A.

    1985-04-05

    An apparatus for providing a simple, low-frequency, electrodeless discharge system for atmospheric pressure afterglow generation. A single quartz tube through which a gas mixture is passed is extended beyond a concentric electrode positioned thereabout. A grounding rod is placed directly above the tube outlet to permit optical viewing of the discharge between the electrodes.

  12. Determination of methane in ambient air by multiplex gas chromatography

    NASA Technical Reports Server (NTRS)

    Valentin, J. R.; Carle, G. C.; Phillips, J. B.

    1985-01-01

    A multiplex gas chromatographic technique for the determination of methane in ambient air over extended periods is reported. A modest gas chromatograph which uses air as the carrier gas was modified by adding a silver oxide sample modulator for multiplex operation. The modulator selectively catalyzes the decomposition of methane in air. The resulting analytical system requires no consumables beyond power. A profile of the methane concentration in this laboratory was obtained for an 8-day period. During this period, methane concentration varied with an approximately daily period from a low of 1.53 + or - 0.60 ppm to a high of 4.63 + or - 0.59 ppm over the entire 8 days. Some of the measured concentrations are higher than those reported elsewhere indicating the presence of some local source or sources for methane. This work has demonstrated the utility of a relatively simple multiplex gas chromatograph for the analysis of environmental samples. The technique should be applicable to other trace components in air through use of other selective modulators.

  13. Devising an adjustable splitter for dual-column gas chromatography.

    PubMed

    Wang, Chieh-Heng; Chang, Chih-Chung; Wang, Jia-Lin

    2007-09-07

    A flow controlled adjustable splitter was configured from a Deans switch and employed in an automated dual column gas chromatographic (GC) system for analyzing mono-aromatic compounds. Volatile organic compounds (VOCs), thermally desorbed from the sorbent trap, were split by the adjustable splitter onto two columns of different phases for separation and then detection by flame ionization detection (FID). Unlike regular splitters in which the split ratio is passively determined by the diameter and/or length of the connecting columns or tubing, the split ratio in our adjustable splitter is controlled by the auxiliary flow in the Deans switch. The auxiliary flow serves as a gas plug on either side of the column for decreasing the sample flow in one transfer line, but increasing the flow in the other. By adjusting the auxiliary flow and therefore the size of the gas plug, the split ratio can be easily varied and favorable to the side of no auxiliary gas. As an illustration, two columns, DB-1 and Cyclodex-B, were employed in this study for separating benzene, toluene, ethylbenzene, xylenes, denoted as BTEX, in particular the structural isomers of o-, m-, p-xylenes. This configuration demonstrates that BTEX cannot be fully separated with either column, but can be deconvoluted by simple algebra if dual columns are used with a splitter. The applicability of the proposed concept was tested by analyzing a gas standard containing BTEX at different split ratios and with various sample sizes, all leading to a constant ratio of m-xylene versus p-xylene.

  14. Rapid determination of nevirapine in human plasma by gas chromatography.

    PubMed

    Langmann, Peter; Schirmer, Diana; Väth, Thomas; Desch, Steffen; Zilly, Michael; Klinker, Hartwig

    2002-02-05

    A sensitive and rapid gas chromatographic method has been developed to determine the levels of the HIV-1 non-nucleoside reverse transcriptase inhibitor nevirapine in human plasma. Quantitative recovery following liquid-liquid-extraction with diethylether from 500 microl of human plasma was achieved. Subsequently, the assay was performed with a CP-Sil 5CB capillary column, 15 m x 0.32 mm x 1.0 microm film thickness with a nitrogen-phosphorous-detector (NPD), Helium 5.0 was used as carrier gas with a constant inlet pressure of 7 p.s.i. Linear standard curves were obtained for concentrations ranging from 10 to 20 000 ng/ml. The calculated intra- and inter-day coefficients of variation were below 8%.

  15. Automated two-dimensional interface for capillary gas chromatography

    DOEpatents

    Strunk, Michael R.; Bechtold, William E.

    1996-02-20

    A multidimensional gas chromatograph (GC) system having wide bore capillary and narrow bore capillary GC columns in series and having a novel system interface. Heart cuts from a high flow rate sample, separated by a wide bore GC column, are collected and directed to a narrow bore GC column with carrier gas injected at a lower flow compatible with a mass spectrometer. A bimodal six-way valve is connected with the wide bore GC column outlet and a bimodal four-way valve is connected with the narrow bore GC column inlet. A trapping and retaining circuit with a cold trap is connected with the six-way valve and a transfer circuit interconnects the two valves. The six-way valve is manipulated between first and second mode positions to collect analyte, and the four-way valve is manipulated between third and fourth mode positions to allow carrier gas to sweep analyte from a deactivated cold trap, through the transfer circuit, and then to the narrow bore GC capillary column for separation and subsequent analysis by a mass spectrometer. Rotary valves have substantially the same bore width as their associated columns to minimize flow irregularities and resulting sample peak deterioration. The rotary valves are heated separately from the GC columns to avoid temperature lag and resulting sample deterioration.

  16. Automated two-dimensional interface for capillary gas chromatography

    DOEpatents

    Strunk, M.R.; Bechtold, W.E.

    1996-02-20

    A multidimensional gas chromatograph (GC) system is disclosed which has wide bore capillary and narrow bore capillary GC columns in series and has a novel system interface. Heart cuts from a high flow rate sample, separated by a wide bore GC column, are collected and directed to a narrow bore GC column with carrier gas injected at a lower flow compatible with a mass spectrometer. A bimodal six-way valve is connected with the wide bore GC column outlet and a bimodal four-way valve is connected with the narrow bore GC column inlet. A trapping and retaining circuit with a cold trap is connected with the six-way valve and a transfer circuit interconnects the two valves. The six-way valve is manipulated between first and second mode positions to collect analyte, and the four-way valve is manipulated between third and fourth mode positions to allow carrier gas to sweep analyte from a deactivated cold trap, through the transfer circuit, and then to the narrow bore GC capillary column for separation and subsequent analysis by a mass spectrometer. Rotary valves have substantially the same bore width as their associated columns to minimize flow irregularities and resulting sample peak deterioration. The rotary valves are heated separately from the GC columns to avoid temperature lag and resulting sample deterioration. 3 figs.

  17. Construction of a thermodesorption injector for gas chromatography.

    PubMed

    Schröder, Wolfgang

    2011-02-01

    A detailed description for the do-it-yourself construction of a high-performance thermodesorption GC injector (HPTI) is presented. The injector consists of a heated desorption chamber, a cooled loop for focusing the desorbed volatiles as well as a heating control for sample injection into the separation column. The gas flow is controlled by valve switching during the steps of the operation. Two versions of the injector function either for the injection of highly volatile compounds or for compounds with extremely low volatility, e.g. lubricants. The sophisticated gas flow management allows injection of highly concentrated samples without memory effects in a sample gas split mode, while traces may be injected with virtually 1:1 sample transfer. A wide range of adsorbents appropriate for the compounds can be chosen due to homemade adsorbent tubes and the achievability of high desorption temperature. Solutions may be injected from a carrier material after solvent evaporation. The HPTI fulfills all multipurpose GC injector requirements and with the support of downloadable instruction files can be built by anyone working with conventional GC devices.

  18. Kinetic efficiency of polar monolithic capillary columns in high-pressure gas chromatography.

    PubMed

    Kurganov, A A; Korolev, A A; Shiryaeva, V E; Popova, T P; Kanateva, A Yu

    2013-11-08

    Poppe plots were used for analysis of kinetic efficiency of monolithic sorbents synthesized in quartz capillaries for utilization in high-pressure gas chromatography. Values of theoretical plate time and maximum number of theoretical plates occurred to depend significantly on synthetic parameters such as relative amount of monomer in the initial polymerization mixture, temperature and polymerization time. Poppe plots let one to find synthesis conditions suitable either for high-speed separations or for maximal efficiency. It is shown that construction of kinetic Poppe curves using potential Van Deemter data demands compressibility of mobile phase to be taken into consideration in the case of gas chromatography. Model mixture of light hydrocarbons C1 to C4 was then used for investigation of influence of carrier gas nature on kinetic efficiency of polymeric monolithic columns. Minimal values of theoretical plate times were found for CO2 and N2O carrier gases.

  19. Feasibility of the preparation of silica monoliths for gas chromatography: fast separation of light hydrocarbons.

    PubMed

    Azzouz, Imadeddine; Essoussi, Anouar; Fleury, Joachim; Haudebourg, Raphael; Thiebaut, Didier; Vial, Jerome

    2015-02-27

    The preparation conditions of silica monoliths for gas chromatography were investigated. Silica-based monolithic capillary columns based on sol-gel process were tested in the course of high-speed gas chromatographic separations of light hydrocarbons mixture (C1-C4). The impact of modifying the amount of porogen and/or catalyst on the monolith properties were studied. At the best precursor/catalyst/porogen ratio evaluated, a column efficiency of about 6500 theoretical plates per meter was reached with a very good resolution (4.3) for very light compounds (C1-C2). The test mixture was baseline separated on a 70cm column. To our knowledge for the first time a silica-based monolithic capillary column was able to separate light hydrocarbons from methane to n-butane at room temperature with a back pressure in the range of gas chromatography facilities (under 4.1bar).

  20. Metal-Organic Framework Thin Films as Stationary Phases in Microfabricated Gas-Chromatography Columns.

    SciTech Connect

    Read, Douglas; Sillerud, Colin Halliday

    2016-01-01

    The overarching goal of this project is to integrate Sandia's microfabricated gas-chromatography ( GC) columns with a stationary phase material that is capable of retaining high-volatility chemicals and permanent gases. The successful integration of such a material with GCs would dramatically expand the repertoire of detectable compounds for Sandia's various microanalysis systems. One such promising class of candidate materials is metal-organic frameworks (MOFs). In this report we detail our methods for controlled deposition of HKUST-1 MOF stationary phases within GC columns. We demonstrate: the chromatographic separation of natural gas; a method for determining MOF film thickness from chromatography alone; and the first-reported GC x GC separation of natural gas -- in general -- let alone for two disparate MOF stationary phases. In addition we determine the fundamental thermodynamic constant for mass sorption, the partition coefficient, for HKUST-1 and several light hydrocarbons and select toxic industrial chemicals.

  1. Capillary gas-liquid chromatography separation of phenethylamines in amphetamine-positive urine samples.

    PubMed

    DePace, A; Verebey, K; elSohly, M

    1990-11-01

    Good gas chromatography (GC) separation of molecules is essential for clean gas chromatography/mass spectrometry (GC/MS) confirmation of compounds. The trifluoro derivatives of ephedrine (E) and methamphetamine (MA) coelute on dimethyl silicone capillary columns, such as DB-1, which are most commonly used by chromatographers. Methods are described to separate E and MA to aid GC/MS confirmations of methamphetamine, ephedrine, or both E and MA together, whichever may be present in Enzyme Immunoassay (EIA)-analyzed amphetamine-positive urine samples. The use of the heptafluoro derivatives of E and MA on a DB-1 column, or the trifluoro derivatives of E and MA on a DB-17 column, is suggested for good gas chromatographic separation.

  2. Partition coefficients of organic compounds in new imidazolium based ionic liquids using inverse gas chromatography.

    PubMed

    Revelli, Anne-Laure; Mutelet, Fabrice; Jaubert, Jean-Noël

    2009-06-05

    Partition coefficients of organic compounds in four ionic liquids: 1-ethanol-3-methylimidazolium tetrafluoroborate, 1-ethanol-3-methylimidazolium hexafluorophosphate, 1,3-dimethylimidazolium dimethylphosphate and 1-ethyl-3-methylimidazolium diethylphosphate were measured using inverse gas chromatography from 303.3 to 332.55K. The influence of gas-liquid and gas-solid interfacial adsorption of different solutes on ionic liquids was also studied. Most of the polar solutes were retained largely by partition while light hydrocarbons were retained predominantly by interfacial adsorption on the ionic liquids studied in this work. The solvation characteristics of the ionic liquids were evaluated using the Abraham solvation parameter model.

  3. Determination of maximal amount of minor gases adsorbed in a shale sample by headspace gas chromatography.

    PubMed

    Zhang, Chun-Yun; Hu, Hui-Chao; Chai, Xin-Sheng; Pan, Lei; Xiao, Xian-Ming

    2014-02-07

    In this paper, we present a novel method for determining the maximal amount of ethane, a minor gas species, adsorbed in a shale sample. The method is based on the time-dependent release of ethane from shale samples measured by headspace gas chromatography (HS-GC). The study includes a mathematical model for fitting the experimental data, calculating the maximal amount gas adsorbed, and predicting results at other temperatures. The method is a more efficient alternative to the isothermal adsorption method that is in widespread use today.

  4. Development of gas chromatography analysis of fatty acids in marine organisms.

    PubMed

    Tang, Baokun; Row, Kyung Ho

    2013-08-01

    The gas chromatographic analysis of fatty acids has attracted considerable interest. In this analysis, the common derivatives of fatty acids, such as fatty acid methyl esters, can be detected using a flame ionization detector and the mass spectra can indicate the true structure of fatty acids. This paper reviews gas chromatographic methods for obtaining fatty acids from marine organisms. The stationary phase and detector for applications in gas chromatography are discussed. This article also reviews the components of fatty acids in marine animals, marine plants and marine microorganisms.

  5. Bridging the gap between gas and liquid chromatography.

    PubMed

    Gritti, Fabrice; Fogwill, Michael; Gilar, Martin; Jarrell, Joseph A

    2016-11-11

    The rapid and complete baseline separation of both volatile (C5 to C16 alkanes in gasoline or terpenes in plant extracts) and non-volatile (>C20 alkanes) organic compounds was achieved by combining (1) low-density fluid chromatography (LDFC) using carbon dioxide at elevated temperature (>90°C) and low pressure (1500psi) designed to increase the retention of the most volatile compounds and (2) high-vacuum technology (<10(-4)Torr) in order to preserve the maximum efficiency of short analytical columns (3.0mm×150mm packed with 1.8μm fully porous HSS-SB-C18 particles) when used in LDFC. The volatile compounds are eluted first under isobaric conditions (1500psi) in less than a minute followed by a linear gradient of the column back pressure (from 1500 to 3500psi in 5min) for the elution of the non-volatile compounds up to C40. The experimental results demonstrate that LDFC performed with short 3.0mm i.d. columns packed with sub-2μm particles and placed under adiabatic conditions enables the analysts to deliver a single, fast, and high-resolution separation of both volatile and non-volatile compounds.

  6. Analysis of phytosterols and phytostanols in enriched dairy products by Fast gas chromatography with mass spectrometry.

    PubMed

    Inchingolo, Raffaella; Cardenia, Vladimiro; Rodriguez-Estrada, Maria Teresa

    2014-10-01

    A Fast gas chromatography and mass spectrometry method for plant sterols/stanols analysis was developed, using a short capillary gas chromatography column (10 m × 0.1 mm internal diameter × 0.1 μm film thickness) coated with 5% diphenyl-polysiloxane. A silylated mixture of the main plant sterols/stanols standards (β-sitosterol, campesterol, stigmasterol, campestanol, sitostanol) was well separated in 1.5 min, with a good peak resolution (>1.4, determined on a critical chromatographic peak pair (β-sitosterol and sitostanol)), repeatability (<13%), and sensitivity (<0.017 ng/mL). The suitability of this Fast chromatography method was tested on plant sterols/stanols-enriched dairy products (yogurt and milk), which were subjected to lipid extraction, cold saponification, and silylation prior to injection. The analytical performance (sensitivity < 0.256 ng/mL and repeatability < 10.36%) and significant reduction of the analysis time and consumables demonstrate that Fast gas chromatography-mass spectrometry method could be also employed for the plant sterols/stanols analysis in functional dairy products.

  7. Theoretical and experimental study of recycle capillary gas chromatography with carrier gas propelled by a peristaltic pump.

    PubMed

    Kubinec, Róbert; Sevcík, Jirí; Górová, Renáta; Addová, Gabriela; Soják, Ladislav

    2003-04-18

    A new technique of recycle capillary gas chromatography (RCGC) characterized by a very high separation efficiency of more than 10(6) theoretical plates has been developed to solve the problem of separation of isomers with similar physico-chemical properties. The technique replaces the recycle valve by a peristaltic pump that propels the carrier gas. A general model has been developed for description of RCGC characteristics and experimentally verified on the retention behaviour of methane and the separation of a test pair of 3-methyl-1-butene and 2-methylbutane.

  8. Assessment of the chemical changes during storage of phenol-formaldehyde resins pyrolysis gas chromatography mass spectrometry, inverse gas chromatography and Fourier transform infra red methods.

    PubMed

    Strzemiecka, B; Voelkel, A; Zięba-Palus, J; Lachowicz, T

    2014-09-12

    The chemical changes occurring in the phenol-formaldehyde resins (resol and novolac type) during their storage were investigated. In this paper the FT-IR, py-GCMS and inverse gas chromatography methods were applied for assessment of the changes occurring during storage of the phenolic resins. We have found that during storage some examined resins occurred partial curing. The results from all techniques applied are consistent. Py-GCMS is useful technique for screening the storage processes but IGC seems to be most sensitive one.

  9. On the two-domain equations for gas chromatography.

    SciTech Connect

    Romero, Louis Anthony; Parks, Michael L.

    2009-01-01

    We present an analysis of gas chromatographic columns where the stationary phase is not assumed to be a thin uniform coating along the walls of the cross section. We also give an asymptotic analysis assuming that the parameter {beta} = KD{sup II}{rho}{sup II}/D{sup I}{rho}{sup I} is small. Here K is the partition coefficient, and D{sup i} and {rho}{sup i}, i = I, II are the diffusivity and density in the mobile (i = I) and stationary (i = II) regions.

  10. Experimental adsorption isotherms based on inverse gas chromatography.

    PubMed

    Kalogirou, E; Bassiotis, I; Artemiadi, Th; Margariti, S; Siokos, V; Roubani-Kalantzopoulou, F

    2002-09-06

    A new chromatographic perturbation method is used for studying the adsorption-desorption equilibrium in various gas-solid heterogeneous systems. It is the reversed-flow method giving accurate and precise values of many physicochemical constants including the basic and necessary adsorption isotherm values. For four inorganic oxides, namely, Cr2O3, Fe2O3, TiO2 and PbO, and two aromatic hydrocarbons (benzene, toluene) these adsorption isotherms have been determined through a non-linear model.

  11. Pioneer Venus gas chromatography of the lower atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Oyama, V. I.; Carle, G. C.; Woeller, F.; Pollack, J. B.; Reynolds, R. T.; Craig, R. A.

    1980-01-01

    A gas chromatograph mounted in the Pioneer Venus sounder probe measured the chemical composition of the atmosphere of Venus at three altitudes. Ne, N2, O2, Ar, CO, H2O, SO2, and CO2 were measured, and upper limits set for H2, COS, H2S, CH4, Kr, N2O, C2H4, C2H6, and C3H8. Simulation studies have provided indirect evidence for sulfuric acid-like droplets and support the possibility of water vapor at altitudes of 42 and 24 km. The paper discusses the implications of these results for the origin, evolution, and present state of Venus' atmosphere.

  12. CORRIGENDUM: Normalization of natural gas composition data measured by gas chromatography Normalization of natural gas composition data measured by gas chromatography

    NASA Astrophysics Data System (ADS)

    Milton, Martin J. T.; Harris, Peter M.; Brown, Andrew S.; Cowper, Chris J.

    2009-11-01

    The authors unintentionally omitted to mention work [1] that pre-dated the cited work by Haesselbarth and Bremser [2]. This work formulated the problem within a mathematical framework and had been cited by the authors in a previous publication [3]. The major conclusion of the authors' work goes beyond the mathematics presented in [1] and [2] because it is applied to several real data sets and the results are interpreted in practical terms. References [1] Haesselbarth W and Bremser W 2001 Correlation in natural gas composition data Proc. Int. Gas Research Conf. (Amsterdam) [2] Haesselbarth W and Bremser W 2007 Metrologia 44 128-45 [3] Brown A S, Milton M J T, Cowper C J, Squire G D, Bremser W and Branch R W 2004 J. Chromatogr. A 1040 215-25

  13. Singlet delta oxygen production in a 2D micro-discharge array in air: effect of gas residence time and discharge power

    NASA Astrophysics Data System (ADS)

    Nayak, Gaurav; Santos Sousa, João; Bruggeman, Peter J.

    2017-03-01

    The production of singlet delta oxygen (O2(a 1Δg)) is of growing interest for many applications. We report on the measurement of O2(a 1Δg) and ozone (O3) in a room temperature atmospheric pressure discharge in dry air. The plasma source is a 2D array of micro-discharges generated by an alternating current voltage at 20 kHz. The study focuses on the effect of gas flow through the discharge. The maximum investigated flow rate allows reducing the gas residence time in the discharge zone to half the discharge period. Results indicate that the residence time and discharge power have a major effect on the O2(a 1Δg) production. Different O2(a 1Δg) density dependencies on power are observed for different flow rates. Effects of collisional quenching on the as-produced and measured O2(a 1Δg) densities are discussed. The flow rate also allows for control of the O2(a 1Δg) to O3 density ratio in the effluent from 0.7 to conditions of pure O3.

  14. Development of hydraulic fracture network propagation model in shale gas reservoirs: 2D, single-phase and 3D, multi-phase model development, parametric studies, and verification

    NASA Astrophysics Data System (ADS)

    Ahn, Chong Hyun

    The most effective method for stimulating shale gas reservoirs is a massive hydraulic fracture treatment. Recent analysis using microseismic technology have shown that complex fracture networks are commonly created in the field as a result of the stimulation of shale wells. The interaction between pre-existing natural fractures and the propagating hydraulic fracture is a critical factor affecting the created complex fracture network; however, many existing numerical models simulate only planar hydraulic fractures without considering the pre-existing fractures in the formation. The shale formations already contain a large number of natural fractures, so an accurate fracture propagation model needs to be developed to optimize the fracturing process. In this research, we first characterized the mechanics of hydraulic fracturing and fluid flow in the shale gas reservoir. Then, a 2D, single-phase numerical model and a 3D, 2-phase coupled model were developed, which integrate dynamic fracture propagation, interactions between hydraulic fractures and pre-existing natural fractures, fracture fluid leakoff, and fluid flow in a petroleum reservoir. By using the developed model, we conducted parametric studies to quantify the effects of treatment rate, treatment size, fracture fluid viscosity, differential horizontal stress, natural fracture spacing, fracture toughness, matrix permeability, and proppant size on the geometry of the hydraulic fracture network. The findings elucidate important trends in hydraulic fracturing of shale reservoirs that are useful in improving the design of treatments for specific reservoir settings.

  15. Determination of free fatty acids and triglycerides by gas chromatography using selective esterification reactions.

    PubMed

    Kail, Brian W; Link, Dirk D; Morreale, Bryan D

    2012-01-01

    A method for selectively determining both free fatty acids (FFA) and triacylglycerides (TAGs) in biological oils was investigated and optimized using gas chromatography after esterification of the target species to their corresponding fatty acid methyl esters (FAMEs). The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Complete conversion of both free acids and glycerides to corresponding FAMEs was found to require more rigorous reaction conditions involving heating to 120°C for up to 2 h. Method validation was provided using gas chromatography-flame ionization detection, gas chromatography-mass spectrometry, and liquid chromatography-mass spectrometry. The method improves on existing methods because it allows the total esterified lipid to be broken down by FAMEs contributed by FFA compared to FAMEs from both FFA and TAGs. Single and mixed-component solutions of pure fatty acids and triglycerides, as well as a sesame oil sample to simulate a complex biological oil, were used to optimize the methodologies. Key parameters that were investigated included: HCl-to-oil ratio, temperature and reaction time. Pure free fatty acids were found to esterify under reasonably mild conditions (10 min at 50°C with a 2.1:1 HCl to fatty acid ratio) with 97.6 ± 2.3% recovery as FAMEs, while triglycerides were largely unaffected under these reaction conditions. The optimized protocol demonstrated that it is possible to use esterification reactions to selectively determine the free acid content, total lipid content, and hence, glyceride content in biological oils. This protocol also allows gas chromatography analysis of FAMEs as a more ideal analyte than glyceride species in their native state.

  16. Application of Headspace Solid Phase Microextraction and Gas Chromatography/Mass Spectrometry for Rapid Detection of the Chemical Warfare Agent Sulfur Mustard

    DTIC Science & Technology

    2002-05-16

    Title of Thesis: “Application of Headspace Solid Phase Microextraction and Gas Chromatography/Mass Spectrometry for Rapid...TITLE AND SUBTITLE Application of Headspace Solid Phase Microextraction and Gas Chromatography/Mass Spectrometry for Rapid Detection of the Chemical...phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS). Five commercially available SPME fibers were investigated to determine the

  17. 40 CFR Appendix 5 to Subpart A of... - Determination of Crude Oil Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography/Mass Spectrometry (GC/MS) 5 Appendix 5 to... Drilling Fluids by Gas Chromatography/Mass Spectrometry (GC/MS) 1.0Scope and Application 1.1This method... fluids (NAFs) by comparing the gas chromatography/mass spectrometry (GC/MS) fingerprint scan...

  18. Determination of phenoxy acid herbicides in water by electron-capture and microcoulometric gas chromatography

    USGS Publications Warehouse

    Goerlitz, D.F.; Lamar, William L.

    1967-01-01

    A sensitive gas chromatographic method using microcoulometric titration and electron-capture detection for the analysis of 2,4-D, silvex, 2,4,5-T, and other phenoxy acid herbicides in water is described. The herbicides are extracted from unfiltered water samples (800-1,000 ml) by use of ethyl ether ; then the herbicides are concentrated and esterilied. To allow the analyst a choice, two esterilication procedures--using either boron trifluoride-methanol or diazomethane--are evaluated. Microcoulometric gas chromatography is specific for the detection of halogenated compounds such as the phenoxy acid herbicides whereas it does not respond to nonhalogenated components. Microcoulometric gas chromatography requires care and patience. It is not convenient for rapid screening of l-liter samples that contain less than 1 microgram of the herbicide. Although electroncapture gas chromatography is less selective and more critically affected by interfering substances, it is, nevertheless, convenient and more sensitive than microcoulometric gas chromatography. Two different liquid phases are used in the gas chromatographic columns--DC-200 silicone in one column and QF-1 silicone in the other. The performance of both columns is improved by the addition of Carbowax 20M. The Gas Chrom Q support is coated with the liquid phases by the 'frontal-analysis' technique. The practical lower limits for measurement of the phenoxy acid herbicides in water primarily depend upon the sample size, interferences present, anal instrumentation used. With l-liter samples of water, the practical lower limits of measurement are 10 ppt (parts per trillion) for 2,4-D and 2 ppt for silvex and 2,4,5-T when electron-capture detection is used, and approximately 20 ppt for each herbicide when analyzed by microcoulometric-titration gas chromatography. Recoveries of the herbicides immediately after addition to unfiltered water samples averaged 92 percent for 2,4-D, 90 percent for silvex, and 98 percent for 2

  19. Qualitative Gas Chromatography-Mass Spectrometry Analyses Using Amines as Chemical Ionization Reagent Gases

    NASA Astrophysics Data System (ADS)

    Little, James L.; Howard, Adam S.

    2013-12-01

    Ammonia is a very useful chemical ionization (CI) reagent gas for the qualitative analyses of compounds by positive ion gas chromatography-mass spectrometry (GCMS). The gas is readily available, inexpensive, and leaves no carbon contamination in the MS source. Compounds of interest to our laboratory typically yield abundant protonated or ammoniated species, which are indicative of a compound's molecular weight. Nevertheless, some labile compounds fragment extensively by substitution and elimination reactions and yield no molecular weight information. In these cases, a CI reagent gas mixture of methylamine in methane prepared dynamically was found to be very useful in obtaining molecular weight data. Likewise, deuterated ammonia and deuterated methylamine are useful CI reagent gases for determining the exchangeable protons in organic compounds. Deuterated methylamine CI reagent gas is conveniently prepared by dynamically mixing small amounts of methylamine with excess deuterated ammonia.

  20. Peak clustering in two-dimensional gas chromatography with mass spectrometric detection based on theoretical calculation of two-dimensional peak shapes: the 2DAid approach.

    PubMed

    van Stee, Leo L P; Brinkman, Udo A Th

    2011-10-28

    A method is presented to facilitate the non-target analysis of data obtained in temperature-programmed comprehensive two-dimensional (2D) gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-ToF-MS). One main difficulty of GC×GC data analysis is that each peak is usually modulated several times and therefore appears as a series of peaks (or peaklets) in the one-dimensionally recorded data. The proposed method, 2DAid, uses basic chromatographic laws to calculate the theoretical shape of a 2D peak (a cluster of peaklets originating from the same analyte) in order to define the area in which the peaklets of each individual compound can be expected to show up. Based on analyte-identity information obtained by means of mass spectral library searching, the individual peaklets are then combined into a single 2D peak. The method is applied, amongst others, to a complex mixture containing 362 analytes. It is demonstrated that the 2D peak shapes can be accurately predicted and that clustering and further processing can reduce the final peak list to a manageable size.

  1. Characterisation of beeswax in works of art by gas chromatography-mass spectrometry and pyrolysis-gas chromatography-mass spectrometry procedures.

    PubMed

    Bonaduce, Ilaria; Colombini, Maria Perla

    2004-03-05

    Pyrolysis (Py) with in situ derivatisation with hexamethyldisilazane-gas chroma-break tography-mass spectrometry (GC-MS) and a gas chromatography-mass spectrometry procedure based on microwave-assisted saponification were used to identify the organic components in small sized beeswax samples. With the latter procedure quantitative recoveries can be made and hydrocarbons, alcohols and omega-1-diols in the neutral fraction, and fatty acids and omega-1-hydroxy acids in the acidic fraction can be efficiently separated and detected. Both procedures were used to characterise a wax anatomic sculpture "The Plague" (1691-1694) by Gaetano Zumbo, resulting in the identification of beeswax and a Pinaceae resin. The GC-MS analysis brought to light some essential differences in beeswax composition between the raw material and the old modelled wax thus giving some clear indications about the recipe used by the sculptor.

  2. Determination of microstickies in recycled whitewater by headspace gas chromatography.

    PubMed

    Chai, X-S; Samp, J C; Yang, Q F; Song, H N; Zhang, D C; Zhu, J Y

    2006-03-03

    This study proposed a novel headspace gas chromatographic (HS-GC) method for determination of adhesive contaminants (microstickies) in recycled whitewater, a fiber containing process stream, in the paper mill. It is based on the adsorption behavior of toluene (as a tracer) on the hydrophobic surface of microstickies, which affects the apparent vapor-liquid equilibration partitioning of toluene. It was found that the equilibrium concentration of toluene in the vapor phase is inversely proportional to the apparent effective surface area of microstickies that remain in the corresponding solution. Thus, the amount of microsticky materials in the recycled whitewater can be quantified by HS-GC via indirect measurement of the toluene content in the vapor phase of the sample without any pretreatment. The presented method is simple, rapid and automated.

  3. Venus lower atmospheric composition - Analysis by gas chromatography

    NASA Technical Reports Server (NTRS)

    Oyama, V. I.; Carle, G. C.; Woeller, F.; Pollack, J. B.

    1979-01-01

    The first gas chromatographic analysis of the lower atmosphere of Venus is reported. Three atmospheric samples were analyzed. The third of these samples showed carbon dioxide (96.4 percent), molecular nitrogen (3.41 percent), water vapor (0.135 percent), molecular oxygen (69.3 ppm), argon (18.6 ppm), neon (4.31 ppm), and sulfur dioxide (186 ppm). The amounts of water vapor and sulfur dioxide detected are roughly compatible with the requirements of greenhouse models of the high surface temperature of Venus. The large positive gradient of sulfur dioxide, molecular oxygen, and water vapor from the cloud tops to their bottoms, as implied by Earth-based observations and these results, gives added support for the presence of major quantities of aqueous sulfuric acid in the clouds. A comparison of the inventory of inert gases found in the atmospheres of Venus, Earth, and Mars suggests that these components are due to outgassing from the planetary interiors.

  4. Cyclopentadiene evolution during pyrolysis-gas chromatography of PMR polyimides

    NASA Technical Reports Server (NTRS)

    Alston, William B.; Gluyas, Richard E.; Snyder, William J.

    1992-01-01

    The effect of formulated molecular weight (FMW), extent of cure, and cumulative aging on the amount of cyclopentadiene (CPD) evolved from Polymerization of Monomeric Reactants (PMR) polyimides were investigated by pyrolysis-gas chromotography (PY-GC). The PMR polyimides are additional crosslinked resins formed from an aromatic diamine, a diester of an aromatic tetracarboxylic acid and a monoester of 5-norbornene-2, 3-dicarboxylic acid. The PY-GC results were related to the degree of crosslinking and to the thermo-oxidative stability (weight loss) of PMR polyimides. Thus, PY-GC has shown to be a valid technique for the characterization of PMR polyimide resins and composites via correlation of the CPD evolved versus the thermal history of the PMR sample.

  5. Evaluation of fast enantioselective multidimensional gas chromatography methods for monoterpenic compounds: Authenticity control of Australian tea tree oil.

    PubMed

    Wong, Yong Foo; West, Rachel N; Chin, Sung-Tong; Marriott, Philip J

    2015-08-07

    This work demonstrates the potential of fast multiple heart-cut enantioselective multidimensional gas chromatography (GC-eGC) and enantioselective comprehensive two-dimensional gas chromatography (eGC×GC), to perform the stereoisomeric analysis of three key chiral monoterpenes (limonene, terpinen-4-ol and α-terpineol) present in tea tree oil (TTO). In GC-eGC, separation was conducted using a combination of mid-polar first dimension ((1)D) column and a chiral second dimension ((2)D) column, providing interference-free enantioresolution of the individual antipodes of each optically active component. A combination of (1)D chiral column and (2)D polar columns (ionic liquid and wax phases) were tested for the eGC×GC study. Quantification was proposed based on summation of two major modulated peaks for each antipode, displaying comparable results with those derived from GC-eGC. Fast chiral separations were achieved within 25min for GC-eGC and<20min for eGC×GC, while ensuring adequate interference-free enantiomer separation. The suitability of using these two enantioselective multidimensional approaches for the routine assessment of chiral monoterpenes in TTO was evaluated and discussed. Exact enantiomeric composition of chiral markers for authentic TTOs was proposed by analysing a representative number of pure TTOs sourced directly from plantations of known provenance in Australia. Consistent enantiomeric fractions of 61.6±1.5% (+):38.4±1.5% (-) for limonene, 61.7±1.6% (+):38.3±1.6% (-) for terpinen-4-ol and 79.6±1.4% (+):20.4±1.4% (-) for α-terpineol were obtained for the 57 authentic Australian TTOs. The results were compared (using principle component analysis) with commercial TTOs (declared as derived from Melaleuca alternifolia) obtained from different continents. Assessing these data to determine adulteration, or additives that affect the enantiomeric ratios, in commercially sourced TTOs is discussed. The proposed method offers distinct advantages over e

  6. Mass Spectral Studies of 1-(2-Chloroethoxy)-2-[(2-chloroethyl)thio] Ethane and Related Compounds Using Gas ChromatographyMass Spectrometry and Gas ChromatographyTriple-Quadrupole Mass Spectrometry

    DTIC Science & Technology

    2016-02-01

    D’Agostino, P.A.; Provost, L.R. Capillary Column Electron Impact and Ammonia Chemical Ionization Gas Chromatographic–Mass Spectrometric and Gas...D’Agostino, P.A.; Provost, L.R. Capillary Column Gas Chromatography- Ammonia and Deuterated Ammonia Chemical Ionization Mass Spectrometry of Sulfur

  7. Levels of phytosterol oxides in enriched and nonenriched spreads: application of a thin-layer chromatography-gas chromatography methodology.

    PubMed

    Conchillo, Ana; Cercaci, Luisito; Ansorena, Diana; Rodriguez-Estrada, Maria Teresa; Lercker, Giovanni; Astiasarán, Iciar

    2005-10-05

    The content of phytosterol oxidation products (POPs) in enriched and nonenriched commercial spreads was evaluated by thin-layer chromatography-gas chromatography (TLC-GC). Oxides of beta-sitosterol, campesterol, and stigmasterol were produced by thermo-oxidation (7-hydroxy, 7-keto, and epoxy derivatives) and chemical synthesis (triol derivatives), which were then separated and identified by TLC-GC. Their identification was further confirmed by GC-mass spectrometry (GC-MS). The total amounts of phytosterols found were 6.07 and 0.33 g/100 g of sample in phytosterol-enriched and nonenriched spread, respectively, whereas the total POPs contents were 45.60 and 13.31 mg/kg of sample in the enriched and nonenriched products. The main POPs found were the 7-keto derivatives of all phytosterols analyzed; 7-ketositosterol was the most abundant one (14.96 and 5.93 mg/kg of sample in phytosterol-enriched and nonenriched spread). No beta-epoxy and triol derivatives were detected in both types of samples. The enriched spread presented a lower phytosterol oxidation rate (0.07%) than the nonenriched one (0.41%).

  8. Steroid profiling by gas chromatography-mass spectrometry and high performance liquid chromatography-mass spectrometry for adrenal diseases.

    PubMed

    McDonald, Jeffrey G; Matthew, Susan; Auchus, Richard J

    2011-12-01

    The ability to measure steroid hormone concentrations in blood and urine specimens is central to the diagnosis and proper treatment of adrenal diseases. The traditional approach has been to assay each steroid hormone, precursor, or metabolite using individual aliquots of serum, each with a separate immunoassay. For complex diseases, such as congenital adrenal hyperplasia and adrenocortical cancer, in which the assay of several steroids is essential for management, this approach is time consuming and costly, in addition to using large amounts of serum. Gas chromatography/mass spectrometry profiling of steroid metabolites in urine has been employed for many years but only in a small number of specialized laboratories and suffers from slow throughput. The advent of commercial high-performance liquid chromatography instruments coupled to tandem mass spectrometers offers the potential for medium- to high-throughput profiling of serum steroids using small quantities of sample. Here, we review the physical principles of mass spectrometry, the instrumentation used for these techniques, the terminology used in this field and applications to steroid analysis.

  9. Broad range analysis of endocrine disruptors and pharmaceuticals using gas chromatography and liquid chromatography tandem mass spectrometry.

    PubMed

    Trenholm, Rebecca A; Vanderford, Brett J; Holady, Janie C; Rexing, David J; Snyder, Shane A

    2006-12-01

    Endocrine disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs) have been globally detected in impacted natural waters. The detection of trace quantities of EDCs and PPCPs in the environment is of great concern since some of these compounds have known physiological responses at low concentrations. EDCs can have a wide range of polarities, acidic and basic moieties, and exist in trace quantities, which often requires numerous complex extractions, large sample collection volumes, and multiple instrumental analyses. A comprehensive method has been developed allowing for the analysis of 58 potential EDCs in various water matrices using a single solid-phase extraction (SPE) of a 1L sample with subsequent analyses using both gas chromatography and liquid chromatography, each coupled with tandem mass spectrometry (GC-MS/MS and LC-MS/MS). Instrument detection limits ranged between 0.12-7.5 pg with corresponding method reporting limits of 1-10 ng l(-1) in water. Recoveries for most compounds were between 50% and 112% with good reproducibility (RSD 6-22%).

  10. Phytochemical Profile of Erythrina variegata by Using High-Performance Liquid Chromatography and Gas Chromatography-Mass Spectroscopy Analyses.

    PubMed

    Muthukrishnan, Suriyavathana; Palanisamy, Subha; Subramanian, Senthilkumar; Selvaraj, Sumathi; Mari, Kavitha Rani; Kuppulingam, Ramalingam

    2016-08-01

    Natural products derived from plant sources have been utilized to treat patients with numerous diseases. The phytochemical constituents present in ethanolic leaf extract of Erythrina variegata (ELEV) were identified by using high-performance liquid chromatography (HPLC) and gas chromatography-mass spectroscopy (GC-MS) analyses. Shade dried leaves were powdered and extracted with ethanol for analyses through HPLC to identify selected flavonoids and through GC-MS to identify other molecules. The HPLC analysis of ELEV showed the presence of gallic and caffeic acids as the major components at concentrations of 2.0 ppm and 0.1 ppm, respectively, as well as other components. GC-MS analysis revealed the presence of 3-eicosyne; 3,7,11,15-tetramethyl-2-hexadecen-1-ol; butanoic acid, 3-methyl-3,7-dimethyl-6-octenyl ester; phytol; 1,2-benzenedicarboxylic acid, diundecyl ester; 1-octanol, 2-butyl-; squalene; and 2H-pyran, 2-(7-heptadecynyloxy) tetrahydro-derivative. Because pharmacopuncture is a new evolving natural mode that uses herbal extracts for treating patients with various ailments with minimum pain and maximum effect, the results of this study are particularly important and show that ELEV possesses a wide range of phytochemical constituents, as indicated above, as effective active principle molecules that can be used individually or in combination to treat patients with various diseases.

  11. Classification of natural resins by liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry using chemometric analysis.

    PubMed

    Rhourrhi-Frih, B; West, C; Pasquier, L; André, P; Chaimbault, P; Lafosse, M

    2012-09-21

    Twenty-six resins from six botanical sources belonging to the class Magnoliopsida were compared based on gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry data. The extracts were analysed by GC after silylation and by reversed phase LC combined with atmospheric pressure photoionisation (APPI) mass spectrometry. The chromatograms were re-organized in data matrices, where each sample was represented by a single column comprising 2755 observations (intensity, time, m/z) in GC-MS and 360 observations in LC-MS. A simple comparison of resin fingerprints was attempted by organizing data according to a three dimensional bubble chart (retention time against m/z where each point was a bubble which size represented the ion intensity) where it is possible to easily superimpose the fingerprints. Thus the common and different species can be easily observed enabling to classify the resins. Hierarchical cluster analysis based on characteristics of GC-MS and LC-MS profiles affords a complete description of the classes of the resins and shows that 26 resins are divided into five main clusters Commiphora mukul, Daniella oliveri, Gardenia gummifera, Canarium madagascariensis, Boswellia dalzielii and Boswellia serrata, respectively. In conclusion, the proposed method has been applied to three other resinous samples from the Burseraceae family to evaluate their alteration state.

  12. Development, validation and determination of multiclass pesticide residues in cocoa beans using gas chromatography and liquid chromatography tandem mass spectrometry.

    PubMed

    Zainudin, Badrul Hisyam; Salleh, Salsazali; Mohamed, Rahmat; Yap, Ken Choy; Muhamad, Halimah

    2015-04-01

    An efficient and rapid method for the analysis of pesticide residues in cocoa beans using gas and liquid chromatography-tandem mass spectrometry was developed, validated and applied to imported and domestic cocoa beans samples collected over 2 years from smallholders and Malaysian ports. The method was based on solvent extraction method and covers 26 pesticides (insecticides, fungicides, and herbicides) of different chemical classes. The recoveries for all pesticides at 10 and 50 μg/kg were in the range of 70-120% with relative standard deviations of less than 20%. Good selectivity and sensitivity were obtained with method limit of quantification of 10 μg/kg. The expanded uncertainty measurements were in the range of 4-25%. Finally, the proposed method was successfully applied for the routine analysis of pesticide residues in cocoa beans via a monitoring study where 10% of them was found positive for chlorpyrifos, ametryn and metalaxyl.

  13. Comparison between high-performance liquid chromatography and gas chromatography methods for fatty acid identification and quantification in potato crisps.

    PubMed

    Sanches-Silva, A; Rodríguez-Bernaldo de Quirós, A; López-Hernández, J; Paseiro-Losada, P

    2004-04-02

    A reversed-phase high performance liquid chromatographic (RP-HLPC) method was compared with a gas chromatography-flame ionization detection (GC-FID) method for determining fatty acids in potato crisps. Different extraction procedures were used. Fatty acids were quantified by linear regression. Both methods presented good precision (R.S.D. < or = 5.88%) and recovery (> or = 82.31%). The precision using HPLC method was slightly better than for GC-FID method. There was good agreement between the fatty acid composition of potato crisps analysed by both methods. For most purposes the HPLC method would be better. However, when more fatty acids need to be analysed, GC is a more suitable method.

  14. Impact of gas chromatography and mass spectrometry combined with gas chromatography and olfactometry for the sex differentiation of Baccharis articulata by the analysis of volatile compounds.

    PubMed

    Minteguiaga, Manuel; Umpiérrez, Noelia; Fariña, Laura; Falcão, Manuel A; Xavier, Vanessa B; Cassel, Eduardo; Dellacassa, Eduardo

    2015-09-01

    The Baccharis genus has more than 400 species of aromatic plants. However, only approximately 50 species have been studied in oil composition to date. From these studies, very few take into consideration differences between male and female plants, which is a significant and distinctive factor in Baccharis in the Asteraceae family. Baccharis articulata is a common shrub that grows wild in south Brazil, northern and central Argentina, Bolivia, Paraguay and Uruguay. It is considered to be a medicinal plant and is employed in traditional medicine. We report B. articulata male and female volatile composition obtained by simultaneous distillation-extraction technique and analyzed by gas chromatography with mass spectrometry. Also, an assessment of aromatic differences between volatile extracts was evaluated by gas chromatography with olfactometry. The results show a very similar chemical composition between male and female extracts, with a high proportion of terpene compounds of which β-pinene, limonene and germacrene D are the main components. Despite the chemical similarity, great differences in aromatic profile were found: male plant samples exhibited the strongest odorants in number and intensity of aromatic attributes. These differences explain field observations which indicate differences between male and female flower aroma, and might be of ecological significance in the attraction of pollinating insects.

  15. Elucidation of the aroma compositions of Zhenjiang aromatic vinegar using comprehensive two dimensional gas chromatography coupled to time-of-flight mass spectrometry and gas chromatography-olfactometry.

    PubMed

    Zhou, Zhilei; Liu, Shuangping; Kong, Xiangwei; Ji, Zhongwei; Han, Xiao; Wu, Jianfeng; Mao, Jian

    2017-03-03

    In this work, a method to characterize the aroma compounds of Zhenjiang aromatic vinegar (ZAV) was developed using comprehensive two dimensional gas chromatography (GC×GC) coupled with time-of-flight mass spectrometry (TOFMS) and gas chromatography olfactometry (GC-O). The column combination was optimized and good separation was achieved. Structured chromatograms of furans and pyrazines were obtained and discussed. A total of 360 compounds were tentatively identified based on mass spectrum match factors, structured chromatogram and linear retention indices comparison. The most abundant class in number was ketones. A large number of esters, furans and derivatives, aldehydes and alcohols were also detected. The odor-active components were identified by comparison of the reported odor of the identified compounds with the odor of corresponding GC-O region. The odorants of methanethiol, 2-methyl-propanal, 2-methyl-butanal/3-methyl-butanal, octanal, 1-octen-3-one, dimethyl trisulfide, trimethyl-pyrazine, acetic acid, 3-(methylthio)-propanal, furfural, benzeneacetaldehyde, 3-methyl-butanoic acid/2-methyl-butanoic acid and phenethyl acetate were suspected to be the most potent. About half of them were identified as significant aroma constituents in ZAV for the first time. Their contribution to specific sensory attribute of ZAJ was also studied. The results indicated that the presented method is suitable for characterization of ZAV aroma constituents. This study also enriches our knowledge on the components and aroma of ZAV.

  16. Off-odor compounds produced in cork by isolated bacteria and fungi: a gas chromatography-mass spectrometry and gas chromatography-olfactometry study.

    PubMed

    Prat, Chantal; Trias, Rosalia; Culleré, Laura; Escudero, Ana; Anticó, Enriqueta; Bañeras, Lluís

    2009-08-26

    The risk of development of specific olfactory profiles in cork was evaluated after inoculation of cork granules and agglomerated and natural cork stoppers with isolated bacteria and fungi. The highest incidence of off-odor development was found in assays when fungi were inoculated. Cork granules with musty-earthy, musty-earthy-TCA, and vegetative deviations were inspected by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Sixteen odor zones were clearly recognized in the GC-O analyses. Among these, octanal, 2-methoxy-3,5-dimethylpyrazine (MDMP), Z-2-nonenal, 2-methylisoborneol, 2,4,6-trichloroanisole (TCA), geosmin, and guaiacol were the most significant odorants and helped in the discrimination of sensory deviations. Only TCA and guaiacol were detected above their respective detection limits by HS-SPME-GC-MS. The fungi Cryptococcus sp. isolate F020, Rhodotorula sp. isolate F025, Penicillium glabrum isolate F001, and Pennicillium variabile F003A and the bacterium Pseudomonas jessenii isolate A1 were found to produce TCA to a greater extent. Additionally, 13 of 38 isolated microorganisms (2 bacteria and 11 fungi) proved able to produce unpleasant musty-earthy or vegetative odors that were not related to a significant TCA accumulation.

  17. Headspace-solid phase microextraction coupled to gas chromatography-combustion-isotope ratio mass spectrometer and to enantioselective gas chromatography for strawberry flavoured food quality control.

    PubMed

    Schipilliti, Luisa; Dugo, Paola; Bonaccorsi, Ivana; Mondello, Luigi

    2011-10-21

    Authenticity assessment of flavoured strawberry foods was performed using headspace-solid phase microextraction (HS-SPME) coupled to gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). An authenticity range was achieved, investigating on the carbon isotope ratio of numerous selected aroma active volatile components (methyl butanoate, ethyl butanoate, hex-(2E)-enal, methyl hexanoate, buthyl butanoate, ethyl hexanoate, hexyl acetate, linalool, hexyl butanoate, octyl isovalerate, γ-decalactone and octyl hexanoate) of organic Italian fresh strawberries. To the author's knowledge, this is the first time that all these components were investigated simultaneously by GC-C-IRMS on the same sample. The results were compared, when applicable, with those obtained by analyzing the HS-SPME extracts of commercial flavoured food matrices. In addition, one Kenyan pineapple and one fresh Italian peach were analyzed to determine the δ(13)C(VPDB) of the volatile components common to strawberry. The δ(13)C(VPDB) values are allowed to differentiate between different biogenetic pathways (C(3) and CAM plants) and more interestingly between plants of the same CO(2) fixation group (C(3) plants). Additional analyses were performed on all the samples by means of Enantioselective Gas Chromatography (Es-GC), measuring the enantiomeric distribution of linalool and γ-decalactone. It was found that GC-C-IRMS and Es-GC measurements were in agreement to detect the presence of non-natural strawberry aromas in the food matrices studied.

  18. Study of the microbiodegradation of terpenoid resin-based varnishes from easel painting using pyrolysis-gas chromatography-mass spectrometry and gas chromatography-mass spectrometry.

    PubMed

    Doménech-Carbó, María Teresa; Osete-Cortina, Laura; de la Cruz Cañizares, Juana; Bolívar-Galiano, Fernando; Romero-Noguera, Julio; Fernández-Vivas, María Antonia; Martín-Sánchez, Inés

    2006-08-01

    The alterations produced by microbiological attack on terpenoid resin-based varnishes from panel and canvas paintings have been evaluated using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and gas chromatography-mass spectrometry (GC-MS). The proposed methods include the on-line derivatisation of drying oils and diterpenoid resins using hexamethyldisilazane during pyrolysis and the application of methyl chloroformate as a derivatisation reagent for triterpenoid resins in GC-MS. Two types of specimens, consisting of model oil medium prepared from linseed oil and model spirit varnishes prepared from colophony and mastic resins dissolved in turpentine, have been used as reference materials. For a series of specimens upon which different genera of bacteria and fungi were inoculated and encouraged to grow, analyses indicated that no mechanisms that commonly occur during the attack of enzymes on drying oils and terpenoid biodegraders were observed to occur in the oil medium and varnishes studied. Thus, the degradation pathways observed in the performed trials usually occur as consequence of natural ageing. Specific trials consisting of the application of biocides to uninoculated colophony varnish resulted in the identification of processes that produce undesirable degradation of the varnish due to interactions between the biocide and the varnish components. Finally, the studied biocides--Biotin, New-Des and Nipagine--generally exhibited good inhibiting effects on the microorganisms studied, although some interesting differences were found between them regarding the application method and type of biocide.

  19. Evaluation of leaf-derived extracts as an environmentally sustainable source of essential oils by using gas chromatography-mass spectrometry and enantioselective gas chromatography-olfactometry.

    PubMed

    d'Acampora Zellner, Barbara; Lo Presti, Maria; Barata, Lauro Euclides Soares; Dugo, Paola; Dugo, Giovanni; Mondello, Luigi

    2006-02-01

    In consideration of the world's present environmental situation and the threat of species extinction, investigations concerning alternative sustainable sources of natural substances represent an extremely important issue. In this respect, the present research is focused on the analytical evaluation of Brazilian rosewood (Aniba rosaeodora Ducke) leaves, as an alternative source (with respect to wood) of rosewood essential oil and, as such, of natural linalool, which is extensively used in perfumery. Enantioselective-gas chromatography-olfactometry (Es-GC-O) was used as a tool for the simultaneous stereodifferentiation and olfactive evaluation of the volatile optically active components present in the analyzed samples. In addition to Es-GC-O analyses, direct olfactive analyses were also performed, enabling the evaluation of the global aroma exerted by each sample and the influence of each linalool antipode, as also other minor compounds. The samples were also submitted to gas chromatography-mass spectrometric analysis, thus establishing their chemical profiles. The assessment of enantiopure chiral compounds through Es-GC-O, along with direct olfactive analyses, confirmed that the leaves are a potential substituent for wood in the extraction of Brazilian rosewood essential oil, representing a sustainable nonwood source of natural linalool.

  20. Analysis of trapped gas in 1E34 detonators by gas chromatography

    SciTech Connect

    Warner, D.K.; Back, P.S.; Barnhart, B.V.

    1980-05-14

    A method was developed to extract and then analyze gas trapped in thermally aged 1E34 detonators. This gas was extracted into an evacuated volume and injected into a gas chromatograph for separation and quantitative analysis. To effect this gas extraction, a device was designed for puncturing the detonator cup and capturing the effused gas. Limited testing of five detonators in this device shows amounts of gas ranging from about 0.5 X 10 {sup -7} to 12 X 10 {sup - 7} moles.

  1. Dynamic headspace gas chromatography of volatile compounds in milk.

    PubMed

    Urbach, G

    1987-08-28

    A method is described for investigating volatile compounds in milk. The volatiles are removed from milk by a stream of helium swept at 100 ml/min over the surface of the milk at 70 degrees C. They are trapped on 40 mg of NIOSH charcoal and then desorbed by heat and re-trapped on the front of a chromatographic column of Tenax-GC coated with 1% OV-275, the column being maintained at room temperature during trapping. An amount of 40 mg NIOSH charcoal under these conditions traps over 90% of the total quantity of the lowest boiling compounds swept from the milk, such as acetaldehyde and ethanol, and retains 100% of the total quantity of acetone, propanol and higher boiling compounds from the gas stream. The volume of milk and its temperature affect the ratios of volatiles collected and these factors are useful in increasing the proportion of a volatile of particular interest. The addition of potassium carbonate increases the yield of volatiles from 100 ml aqueous phase but not from 10 ml.

  2. Determination of oxalate in black liquor by headspace gas chromatography.

    PubMed

    Li, Hailong; Chai, Xin-Sheng; DeMartini, Nikolai; Zhan, Huaiyu; Fu, Shiyu

    2008-05-30

    This study demonstrated a headspace gas chromatographic method (HS-GC) for the determination of oxalate content in black liquor (alkaline aqueous solution of inorganic chemicals and dissolved wood species from the alkaline pulping of wood). The method described in this paper is based on the reaction between oxalic and manganese dioxide in an acidic medium, in which oxalic acid is converted to carbon dioxide that is measured with a GC using a thermal conductivity detector. The challenge in developing this method was ensuring complete conversion of oxalic acid while minimizing the contribution of side reactions between carbohydrates, lignin and manganese dioxide to the carbon dioxide measured. It was found that a complete conversion of oxalate to carbon dioxide can be achieved within 3 min at a temperature of 70 degrees C; a MnO(2):C(oxalate) (concentration of H(2)C(2)O(4)+HC(2)O(4)(-)+C(2)O(4)(2-)) mole ratio of 60 and H(2)SO(4) concentration of 0.005-0.01 mol/L in the headspace vial. The method can detect concentrations as low as 0.39 microg of oxalate. The standard deviation was found to be 7% while recovery experiments with black liquor showed recoveries of 93-108% which were deemed acceptable for analysis of oxalate in an industrial sample such as black liquor.

  3. Isotope Ratio Monitoring Gas Chromatography Mass Spectrometry (IRM-GCMS)

    NASA Technical Reports Server (NTRS)

    Freeman, K. H.; Ricci, S. A.; Studley, A.; Hayes, J. M.

    1989-01-01

    On Earth, the C-13 content of organic compounds is depleted by roughly 13 to 23 permil from atmospheric carbon dioxide. This difference is largely due to isotope effects associated with the fixation of inorganic carbon by photosynthetic organisms. If life once existed on Mars, then it is reasonable to expect to observe a similar fractionation. Although the strongly oxidizing conditions on the surface of Mars make preservation of ancient organic material unlikely, carbon-isotope evidence for the existence of life on Mars may still be preserved. Carbon depleted in C-13 could be preserved either in organic compounds within buried sediments, or in carbonate minerals produced by the oxidation of organic material. A technique is introduced for rapid and precise measurement of the C-13 contents of individual organic compounds. A gas chromatograph is coupled to an isotope-ratio mass spectrometer through a combustion interface, enabling on-line isotopic analysis of isolated compounds. The isotope ratios are determined by integration of ion currents over the course of each chromatographic peak. Software incorporates automatic peak determination, corrections for background, and deconvolution of overlapped peaks. Overall performance of the instrument was evaluated by the analysis of a mixture of high purity n-alkanes of know isotopic composition. Isotopic values measured via IRM-GCMS averaged withing 0.55 permil of their conventionally measured values.

  4. Detection and identification of bacteria by gas chromatography.

    PubMed

    Henis, Y; Gould, J R; Alexander, M

    1966-07-01

    Ether extracts of cultures of 29 strains representing 6 species of Bacillus, and of individual strains of Escherichia coli, Aerobacter aerogenes, and Pseudomonas aeruginosa were examined in a gas chromatograph by use of flame ionization and electron capture detectors. Among the products detected were compounds with the chromatographic characteristics of acetic, propionic, and butyric acids, ethyl alcohol, diacetyl, acetoin, and 2,3-butanediol. The differences in peak areas of the various products formed by the bacteria were determined statistically for the chromatograms obtained with the two detectors, and the peaks were arranged in order of decreasing areas to yield a signature for each bacterial strain. Different signatures were obtained for the various genera and species and for strains of the same species. B. licheniformis, B. subtilis, and A. aerogenes formed significant quantities of a number of volatile compounds, and qualitative and quantitative differences between strains were noted. The electron capture detector was particularly sensitive to diacetyl and acetoin as well as to unknown compounds. By use of this detector, the presence of 5 pg of diacetyl and 20 pg of acetoin could be demonstrated. The quantity of acetoin detected in B. subtilis and B. licheniformis cultures was present in as little as 6.3 x 10(-3) muliters of medium.

  5. Differentiation of mint (Mentha haplocalyx Briq.) from different regions in China using gas and liquid chromatography.

    PubMed

    Dong, Wenjiang; Ni, Yongnian; Kokot, Serge

    2015-02-01

    In this study, complex substances such as Mint (Mentha haplocalyx Briq.) samples from different growing regions in China were analyzed for phenolic compounds by high-performance liquid chromatography with diode array detection and for the volatile aroma compounds by gas chromatography with mass spectrometry. Chemometrics methods, e.g. principal component analysis, back-propagation artificial neural networks, and partial least squares discriminant analysis, were applied to resolve complex chromatographic profiles of Mint samples. A total of 49 aroma components and 23 phenolic compounds were identified in 79 Mint samples. Principal component analysis score plots from gas chromatography with mass spectrometry and high-performance liquid chromatography with diode array detection data sets showed a clear distinction among Mint from three different regions in China. Classification results showed that satisfactory performance of prediction ability for back-propagation artificial neural networks and partial least squares discriminant analysis. The major compounds that contributed to the discrimination were chlorogenic acid, unknown 3, kaempherol 7-O-rutinoside, salvianolic acid L, hesperidin, diosmetin, unknown 6 and pebrellin in Mint according to regression coefficients of the partial least squares discriminant analysis model. This study indicated that the proposed strategy could provide a simple and rapid technique to distinguish clearly complex profiles from samples such as Mint.

  6. Gas-liquid chromatography in routine processing of blood cultures for detecting anaerobic bacteraemia.

    PubMed Central

    Reig, M; Molina, D; Loza, E; Ledesma, M A; Meseguer, M A

    1981-01-01

    Gas-liquid chromatography was performed on 233 positive blood cultures and findings were compared with culture results. Obligate anaerobic bacteria were recovered from 78 out of 79 blood cultures containing butyric or iso-valeric acids, or both; from 28 out of 69 blood cultures containing succinic acid; and from only one out of 41 blood cultures containing succinic but not butyric or iso-valeric acid. Good correlations (88%) were found for the recovery of anaerobic bacteria and the detection of butyric and/or iso-valeric acids. Detecting volatile fatty acids by gas-liquid chromatography performed on blood cultures at the first signs of growth can therefore provide an early and reliable indication of the presence of anaerobic bacteria. PMID:7014645

  7. Investigating Solvent Purity Utilizing Comprehensive Gas Chromatography: A Study of Acetones

    SciTech Connect

    Wahl, Jon H.; Bolz, Cinnamon DH; Wahl, Karen L.

    2010-04-01

    Broad spectrum chemical analysis of trace level components is a continuing challenge for any analytical chemist. This challenge is further confounded when chemical impurities may be present in common organic solvents or when chemical artifacts may be formed, produced and introduced during an analytical procedure. Minimizing and understanding these chemical artifacts, is critical for trace level detection and is crucial for unambiguous analytical results. Comprehensive gas chromatography is an excellent analytical tool to help address these complex mixture challenges. This work examines the impurities present in various acetone sources utilizing comprehensive gas chromatography. This work highlights the extreme variability possible in solvent sources and hence the importance of understanding the impurities that may confound an analytical method or result.

  8. Gas chromatography with flame photometric detection of 31 organophosphorus pesticide residues in Alpinia oxyphylla dried fruits.

    PubMed

    Zhao, Xiangsheng; Kong, Weijun; Wei, Jianhe; Yang, Meihua

    2014-11-01

    A simple, rapid and effective gas chromatography-flame photometric detection method was established for simultaneous multi-component determination of 31 organophosphorus pesticides (OPPs) residues in Alpinia oxyphylla, which is widely consumed as a traditional medicine and food in China. Sample preparation was completed in a single step without any clean-up procedure. All pesticides expressed good linear relationships between 0.004 and 1.0 μg/mL with correlation coefficients higher than 0.9973. The method gave satisfactory recoveries for most pesticides. The limits of detection varied from 1 to 10 ng/mL, and the limits of quantification (LOQs) were between 4 and 30 ng/mL. The proposed method was successfully applied to 55 commercial samples purchased from five different areas. Five pesticide residues were detected in four (7.27%) samples. The positive samples were confirmed by gas chromatography with tandem mass spectrometry (GC-MS/MS).

  9. Measuring fuel contamination using high speed gas chromatography and cone penetration techniques

    SciTech Connect

    Farrington, S.P.; Bratton, W.L.; Akard, M.L.

    1995-10-01

    Decision processes during characterization and cleanup of hazardous waste sites are greatly retarded by the turnaround time and expense incurred through the use of conventional sampling and laboratory analyses. Furthermore, conventional soil and groundwater sampling procedures present many opportunities for loss of volatile organic compounds (VOC) by exposing sample media to the atmosphere during transfers between and among sampling devices and containers. While on-site analysis by conventional gas chromatography can reduce analytical turnaround time, time-consuming sample preparation procedures are still often required, and the potential for loss of VOC is not reduced. This report describes the development of a high speed gas chromatography and cone penetration testing system which can detect and measure subsurface fuel contamination in situ during the cone penetration process.

  10. [Determination of 2-methyl-3-nitrobenzoic acid through pretreatment with diazomethane by gas chromatography].

    PubMed

    Xue, Ke-She; Nan, Zhi-Xiang

    2002-09-01

    A method for the quantitative determination of 2-methyl-3-nitrobenzoic acid by gas chromatography is described. 2-Methyl-3-nitrobenzoic acid was esterified by pretreatment with diazomethane prior to analysis. A CP-Sil-43CB capillary column(25 m x 0.32 mm i.d. x 0.2 microm), a flame ionization detector and the area normalization method were used. The average recovery was 99.81%. The RSD was 0.08% and the detection limit was 3 x 10(-11) g. The results showed that the method is practical and reliable. It was realized that the higher purity and higher boiler matter was analyzed by gas chromatography. The method can be used to monitor the purity of this type of materials. analysis of research and production. It can be used in the development of new products and in the process.

  11. Structural analysis of commercial ceramides by gas chromatography-mass spectrometry.

    PubMed

    Bleton, J; Gaudin, K; Chaminade, P; Goursaud, S; Baillet, A; Tchapla, A

    2001-05-11

    A simple method using gas chromatography-mass spectrometry was applied to analyse structures of ceramides. Identification of trimethylsilylated ceramides were obtained in short analysis times (derivatization of ceramides in 30 min at room temperature and 20 min gas chromatography mass spectrometry run) even for complex mixtures. For example in ceramide Type III, 18 peaks were observed which represent 27 various structures. The coeluted compounds were ceramides containing the same functional groups and the same carbon number but with a different distribution on the two alkyl chains of the molecule. They were accurately differentiated by mass spectrometry. Therefore, 83 structures of trimethylsilylated ceramides were identified in 11 different commercial mixtures. For 52 structures of these, mass spectral data were not described in the literature, neither full mass spectra nor characteristic fragments.

  12. Pyrolysis gas-liquid chromatography of the genus Bacillus: effect of growth media on pyrochromatogram reproducibility.

    PubMed

    Oxborrow, G S; Fields, N D; Puleo, J R

    1977-04-01

    Pyrolysis gas-liquid chromatography was performed on dried Bacillus microorganisms to evaluate the effects of growth media. Six cultures of Bacillus and six lot numbers of Trypticase soy agar (BBL) were used to test the hypothesis that a microorganism grown on various lot numbers of the same chromatogram. Also tested was the effect of three different media on chromatogram reproduction using the same six cultures. Results show little or no differences observed between the chromatograms of the individual Bacillus spp. grown on the six lot numbers of Trypticase soy agar. When chromatograms of the three different media were compared, several differences were observed, particularly in the areas most characteristic of individual species. Pryolysis gas-liquid chromatography can be a useful tool for the characterization or identification of the genus Bacillus if the chromatographic and cultural conditions are maintained.

  13. Surface energy of microcrystalline cellulose determined by capillary intrusion and inverse gas chromatography.

    PubMed

    Steele, D Fraser; Moreton, R Christian; Staniforth, John N; Young, Paul M; Tobyn, Michael J; Edge, Stephen

    2008-09-01

    Surface energy data for samples of microcrystalline cellulose have been obtained using two techniques: capillary intrusion and inverse gas chromatography. Ten microcrystalline cellulose materials, studied using capillary intrusion, showed significant differences in the measured surface energetics (in terms of total surface energy and the acid-base characteristics of the cellulose surface), with variations noted between the seven different manufacturers who produced the microcrystalline cellulose samples. The surface energy data from capillary intrusion was similar to data obtained using inverse gas chromatography with the column maintained at 44% relative humidity for the three samples of microcrystalline cellulose studied. This suggests that capillary intrusion may be a suitable method to study the surface energy of pharmaceutical samples.

  14. Utilizing a constant peak width transform for isothermal gas chromatography.

    PubMed

    Nadeau, Jeremy S; Wilson, Ryan B; Fitz, Brian D; Reed, Jason T; Synovec, Robert E

    2011-06-10

    A computational approach to partially address the general elution problem (GEP), and better visualize, isothermal gas chromatograms is reported. The theoretical computational approach is developed and applied experimentally. We report a high speed temporally increasing boxcar summation (TIBS) transform that, when applied to the raw isothermal GC data, converts the chromatographic data from the initial time domain (in which the peak widths in isothermal GC increase as a function of their retention factors, k), to a data point based domain in which all peaks have the same peak width in terms of number of points in the final data vector, which aides in preprocessing and data analysis, while minimizing data storage size. By applying the TIBS transform, the resulting GC chromatogram (initially collected isothermally), appears with an x-axis point scale as if it were instrumentally collected using a suitable temperature program. A high speed GC isothermal separation with a test mixture containing 10 compounds had a run time of ∼25 s. The peak at a retention factor k ∼0.7 had a peak width of ∼55 ms, while the last eluting peak at k ∼89 (i.e., retention time of ∼22 s) had a peak width of ∼2000 ms. Application of the TIBS transform increased the peak height of the last eluting peak 45-fold, and S/N ∼20-fold. All peaks in the transformed test mixture chromatogram had the width of an unretained peak, in terms of number of data points. A simulated chromatogram at unit resolution, studied using the TIBS transform, provided additional insight into the benefits of the algorithm.

  15. Analysis of benzo(a)pyrene in airborne particulates by gas chromatography

    NASA Technical Reports Server (NTRS)

    Luedecke, E.

    1976-01-01

    A routine method was developed to measure benzo(a)pyrene in airborne particulates. Samples were collected on a filter and the organic portion was extracted with cyclohexane. The polynuclear hydrocarbon (PNHC) fraction was separated from the aliphatics by column chromatography. An internal standard was added to the extract and a portion of it was injected into a gas chromatograph. Although the gas chromatographic method has often been reported in the literature, satisfactory separation of benzo(a)pyrene and benzo(e)pyrene has not been achieved. With the introduction of a nematic liquid crystal as the stationary phase good separation is now possible.

  16. Sub-to super-ambient temperature programmable microfabricated gas chromatography column

    DOEpatents

    Robinson, Alex L.; Anderson, Lawrence F.

    2004-03-16

    A sub- to super-ambient temperature programmable microfabricated gas chromatography column enables more efficient chemical separation of chemical analytes in a gas mixture by combining a thermoelectric cooler and temperature sensing on the microfabricated column. Sub-ambient temperature programming enables the efficient separation of volatile organic compounds and super-ambient temperature programming enables the elution of less volatile analytes within a reasonable time. The small heat capacity and thermal isolation of the microfabricated column improves the thermal time response and power consumption, both important factors for portable microanalytical systems.

  17. Liquid chromatography and supercritical fluid chromatography as alternative techniques to gas chromatography for the rapid screening of anabolic agents in urine.

    PubMed

    Desfontaine, Vincent; Nováková, Lucie; Ponzetto, Federico; Nicoli, Raul; Saugy, Martial; Veuthey, Jean-Luc; Guillarme, Davy

    2016-06-17

    This work describes the development of two methods involving supported liquid extraction (SLE) sample treatment followed by ultra-high performance liquid chromatography or ultra-high performance supercritical fluid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS and UHPSFC-MS/MS) for the screening of 43 anabolic agents in human urine. After evaluating different stationary phases, a polar-embedded C18 and a diol columns were selected for UHPLC-MS/MS and UHPSFC-MS/MS, respectively. Sample preparation, mobile phases and MS conditions were also finely tuned to achieve highest selectivity, chromatographic resolution and sensitivity. Then, the performance of these two methods was compared to the reference routine procedure for steroid analyses in anti-doping laboratories, which combines liquid-liquid extraction (LLE) followed by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). For this purpose, urine samples spiked with the compounds of interest at five different concentrations were analyzed using the three analytical platforms. The retention and selectivity of the three techniques were very different, ensuring a good complementarity. However, the two new methods displayed numerous advantages. The overall procedure was much faster thanks to high throughput SLE sample treatment using 48-well plates and faster chromatographic analysis. Moreover, the highest sensitivity was attained using UHPLC-MS/MS with 98% of the doping agents detected at the lowest concentration level (0.1ng/mL), against 76% for UHPSFC-MS/MS and only 14% for GC-MS/MS. Finally, the weakest matrix effects were obtained with UHPSFC-MS/MS with 76% of the analytes displaying relative matrix effect between -20 and 20%, while the GC-MS/MS reference method displayed very strong matrix effects (over 100%) for all of the anabolic agents.

  18. Surface energy of bovine dentin and enamel by means of inverse gas chromatography.

    PubMed

    Okulus, Zuzanna; Strzemiecka, Beata; Czarnecka, Beata; Buchwald, Tomasz; Voelkel, Adam

    2015-04-01

    Adhesion between tooth tissues and dental fillings depends on the surface energy of both connected materials. Bond strength can be determined directly or indirectly as a work of adhesion on the basis of values of surface energy of these materials. Inverse gas chromatography (IGC) is one of the methods of surface energy examination. In this study the values of total surface energy components of wet and dry teeth fragments (enamel, crown dentin and root dentin) were determined with the use of inverse gas chromatography. Inverse gas chromatography has never been used for investigation of surface energy of natural tooth tissues. Different storage conditions were examined - wet and dry. Different values of surface energy are observed according to the type of tooth tissue (dentin or enamel), occurring place (crown or root) and storage conditions (dry or wet). The effect of tissue type and occurring place was the greatest, while storage conditions were of secondary importance. Surface energy depends on composition of tissue, its surface area and the presence of pores.

  19. Performance of a Micro-Strip Gas Chamber for event wise, high rate thermal neutron detection with accurate 2D position determination

    NASA Astrophysics Data System (ADS)

    Mindur, B.; Alimov, S.; Fiutowski, T.; Schulz, C.; Wilpert, T.

    2014-12-01

    A two-dimensional (2D) position sensitive detector for neutron scattering applications based on low-pressure gas amplification and micro-strip technology was built and tested with an innovative readout electronics and data acquisition system. This detector contains a thin solid neutron converter and was developed for time- and thus wavelength-resolved neutron detection in single-event counting mode, which improves the image contrast in comparison with integrating detectors. The prototype detector of a Micro-Strip Gas Chamber (MSGC) was built with a solid natGd/CsI thermal neutron converter for spatial resolutions of about 100 μm and counting rates up to 107 neutrons/s. For attaining very high spatial resolutions and counting rates via micro-strip readout with centre-of-gravity evaluation of the signal amplitude distributions, a fast, channel-wise, self-triggering ASIC was developed. The front-end chips (MSGCROCs), which are very first signal processing components, are read out into powerful ADC-FPGA boards for on-line data processing and thereafter via Gigabit Ethernet link into the data receiving PC. The workstation PC is controlled by a modular, high performance dedicated software suite. Such a fast and accurate system is crucial for efficient radiography/tomography, diffraction or imaging applications based on high flux thermal neutron beam. In this paper a brief description of the detector concept with its operation principles, readout electronics requirements and design together with the signals processing stages performed in hardware and software are presented. In more detail the neutron test beam conditions and measurement results are reported. The focus of this paper is on the system integration, two dimensional spatial resolution, the time resolution of the readout system and the imaging capabilities of the overall setup. The detection efficiency of the detector prototype is estimated as well.

  20. Study of Ether-, Alcohol-, or Cyano-Functionalized Ionic Liquids Using Inverse Gas Chromatography

    SciTech Connect

    Revelli, Anne-Laure; Mutelet, Fabrice; Jaubert, Jean-Noel; Garcia-Martinez, Marina; Sprunger, Laura; Acree, William; Baker, Gary A

    2010-01-01

    Activity coefficients of 52 organic compounds in four ionic liquids (ILs), 1,3-dimethoxyimidazolium bis((trifluoromethyl)sulfonyl)imide, 1-(methylethylether)-3-methylimidazolium bis((trifluoromethyl)sulfonyl) imide, 1-ethanol-3-methylimidazolium bis((trifluoromethyl)-sulfonyl)imide, and 1-(3-cyanopropyl)-3- methylimidazolium dicyanamide, were measured using inverse gas chromatography from (312 to 353) K. The retention data were also converted in gas-to-IL partition coefficients and water-to-IL partition coefficients using the corresponding gas-to-water partition coefficients. Both sets of partition coefficients were analyzed using the modified Abraham solvation parameter model. The derived equations correlated the experimental gas-to-IL and water-to-IL partition coefficient data to within (0.09 and 0.14) log units, respectively.

  1. An unambiguous identification of 2D electron gas features in the photoluminescence spectrum of AlGaN/GaN heterostructures

    NASA Astrophysics Data System (ADS)

    Jana, Dipankar; Sharma, T. K.

    2016-07-01

    A fast and non-destructive method for probing the true signatures of 2D electron gas (2DEG) states in AlGaN/GaN heterostructures is presented. Two broad features superimposed with interference oscillations are observed in the low temperature photoluminescence (PL) spectrum. The two features are identified as the ground and excited 2DEG states which are confirmed by comparing the PL spectra of as-grown and top barrier layer etched samples. Broad PL features disappear at a certain temperature along with the associated interference oscillations. Furthermore, the two broad PL features depicts specific temperature and excitation intensity dependencies which make them easily distinguishable from the bandedge excitonic or defect related PL features. The presence of strong interference oscillations associated with the 2DEG PL features is explained by considering the localized generation of PL signal at the AlGaN/GaN heterointerface. Finally, a large value of the polarization induced electric field of ~1.01 MV cm-1 is reported from PL measurements for AlGaN/GaN HEMT structures. It became possible only when the true identification of 2DEG features was made possible by the proposed method.

  2. Quantification of carbonate by gas chromatography-mass spectrometry.

    PubMed

    Tsikas, Dimitrios; Chobanyan-Jürgens, Kristine

    2010-10-01

    Carbon dioxide and carbonates are widely distributed in nature, are constituents of inorganic and organic matter, and are essential in vegetable and animal organisms. CO(2) is the principal greenhouse gas in the atmosphere. In human blood, CO(2)/HCO(3)(-) is an important buffering system. Quantification of bicarbonate and carbonate in inorganic and organic matter and in biological fluids such as blood or blood plasma by means of the GC-MS technology has been impossible so far, presumably because of the lack of suitable derivatization reactions to produce volatile and thermally stable derivatives. Here, a novel derivatization reaction is described for carbonate that allows for its quantification in aqueous alkaline solutions and alkalinized plasma and urine. Carbonate in acetonic solutions of these matrices (1:4 v/v) and added (13)C-labeled carbonate for use as the internal standard were heated in the presence of the derivatization agent pentafluorobenzyl (PFB) bromide for 60 min and 50 °C. Investigations with (12)CO(3)(2-), (13)CO(3)(2-), (CH(3))(2)CO, and (CD(3))(2)CO in alkaline solutions and GC-MS and GC-MS/MS analyses under negative-ion chemical ionization (NICI) or electron ionization (EI) conditions of toluene extracts of the reactants revealed formation of two minor [i.e., PFB-OCOOH and O=CO(2)-(PFB)(2)] and two major [i.e., CH(3)COCH(2)-C(OH)(OPFB)(2) and CH(3)COCH=C(OPFB)(2)] carbonate derivatives. The latter have different retention times (7.9 and 7.5 min, respectively) but virtually identical EI and NICI mass spectra. It is assumed that CH(3)COCH(2)-C(OH)(OPFB)(2) is formed from the reaction of the carbonate dianion with two molecules of PFB bromide to form the diPFB ester of carbonic acid, which further reacts with one molecule of acetone. Subsequent loss of water finally generates the major derivative CH(3)COCH=C(OPFB)(2). This derivatization reaction was utilized to quantify total CO(2)/HCO(3)(-)/CO(3)(2-) (tCO(2)) in human plasma and urine by GC

  3. Organophosphorus pesticide and ester analysis by using comprehensive two-dimensional gas chromatography with flame photometric detection.

    PubMed

    Liu, Xiangping; Li, Dengkun; Li, Jiequan; Rose, Gavin; Marriott, Philip J

    2013-12-15

    Thirty-seven phosphorus (P)-containing compounds comprising organophosphorus pesticides and organophosphate esters were analyzed by using comprehensive two-dimensional gas chromatography with flame photometric detection in P mode (GC × GC-FPD(P)), with a non-polar/moderately polar column set. A suitable modulation temperature and period was chosen based on experimental observation. A number of co-eluting peak pairs on the (1)D column were well separated in 2D space. Excellent FPD(P) detection selectivity, responding to compounds containing the P atom, produces clear 2D GC × GC plots with little interference from complex hydrocarbon matrices. Limits of detection (LOD) were within the range of 0.0021-0.048 μmol L(-1), and linear calibration correlation coefficients (R(2)) for all 37 P-compounds were at least 0.998. The P-compounds were spiked in 2% diesel and good reproducibility for their response areas and retention times was obtained. Spiked recoveries were 88%-157% for 5 μg L(-1) and 80%-138% for 10 μg L(-1) spiked levels. Both (1)tR and (2)tR shifts were noted when the content of diesel was in excess of 5% in the matrix. Soil samples were analyzed by using the developed method; some P-compounds were positively detected. In general, this study shows that GC × GC-FPD(P) is an accurate, sensitive and simple method for P-compound analysis in complicated environmental samples.

  4. Use of greatly-reduced gas flows in flow-modulated comprehensive two-dimensional gas chromatography-mass spectrometry.

    PubMed

    Tranchida, Peter Q; Franchina, Flavio A; Dugo, Paola; Mondello, Luigi

    2014-09-12

    The present research is specifically based on the use of greatly-reduced gas flows, in flow-modulator (FM) comprehensive two-dimensional gas chromatography systems. In particular, focus of the present research is directed to FM devices characterized by an accumulation stage, and a much briefer re-injection step. It has been widely accepted that the operation of such FM systems requires high gas flows (≥20mL/min), to re-inject the gas-phase contents of sample (or accumulation) loops, onto the second column. On the contrary, it will be herein demonstrated that much lower gas flows (≈ 6-8mL/min) can efficiently perform the modulation step of re-injection. The possibility of using such improved operational conditions is given simply by a fine optimization of the processes of accumulation and re-injection. The application of lower gas flows not only means that second-dimension separations are carried out under better analytical conditions, but, even more importantly, greatly reduces problems which arise when using mass spectrometry (i.e., sensitivity and instrumental pumping capacity).

  5. Multiresidue analysis of pesticides in traditional Chinese medicines using gas chromatography - negative chemical ionization tandem mass spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, a residue analysis method for the simultaneous determination of 107 pesticides in the traditional Chinese medicines (TCMs), Angelica sinensis, Angelica dahurica, Leonurus heterophyllus Sweet, Pogostemon cablin, and Lonicera japonica Thunb, was developed using gas chromatography couple...

  6. Simultaneous Determination of Cyanide and Thiocyanate in Plasma by Chemical Ionization Gas Chromatography Mass-Spectrometry (CI-GC-MS)

    DTIC Science & Technology

    2012-09-04

    ORIGINAL PAPER Simultaneous determination of cyanide and thiocyanate in plasma by chemical ionization gas chromatography mass-spectrometry (CI-GC-MS...chemical ioniza- tion gas chromatography-mass spectrometry was developed for the simultaneous determination of cyanide and thiocya- nate in plasma...Sample preparation for this analysis required essentially one-step by combining the reaction of cyanide and thiocyanate with pentafluorobenzyl bromide

  7. Thermal desorption modulation for comprehensive two-dimensional gas chromatography using a simple and inexpensive segmented-loop fluidic interface.

    PubMed

    Mucédola, Vanessa; Vieira, Luis C S; Pierone, Danilo; Gobbi, Angelo L; Poppi, Ronei J; Hantao, Leandro W

    2017-03-01

    In this study, we introduce a modulation strategy for comprehensive two-dimensional gas chromatography (GC×GC) by using a simple and consumable-free modulator. This "Do-It-Yourself" interface comprised a 1.0m×0.25mm segment of MTX-5 metallic column and a low-cost DC power supply. Thermal desorption modulation (TDM) was attained using a dual-stage heater-based modulator in a novel segmented-loop configuration. TDM was achieved by alternating analyte trapping and thermal desorption. Former process relied on analyte partition to sorbent phase, while latter explored direct resistive heating. Introduction of an intermediate delay segment between the two stages mitigated analyte breakthrough, improving peak symmetry and chromatographic efficiency. This feature was critical to acquire reliable GC×GC modulation using such simple heater-based device. The effects of important modulation variables on 2D separations were investigated, including TDM stage length, dimension of delay loop, and outlet pressure. Significant advances and limitations of proposed TDM strategy were carefully determined. Proposed GC×GC prototype by using an in-oven TDM modulator was successfully applied to a series of challenging matrices, including petroleum distillates, biodiesel, and essential oil. This open-hardware, cost-effective modulator was easy to install and operate, as it circumvented the need for sophisticated components (e.g. moving parts and cooling systems). Therefore, our modulator is a compelling alternative to existing GC×GC solutions to operate in resource-limited laboratories.

  8. Isolation and identification of the metolachlor stereoisomers using high-performance liquid chromatography, polarimetric measurements, and enantioselective gas chromatography.

    PubMed

    Müller, M D; Poiger, T; Buser, H

    2001-01-01

    Because of the presence of two chiral elements (an asymmetrically substituted carbon and a chiral axis), the herbicide metolachlor consists of four stereoisomers stable at ambient temperature with aSS-, aRS-, aSR-, and aRR-configurations (aSS, the isomer with aS,1'S-configuration, etc.). Metolachlor, initially introduced into the market as the racemic product containing all four stereoisomers, is currently being replaced worldwide by S-metolachlor, the product enantiomerically enriched with the herbicidally active 1'S-isomers (aSS, aRS). The isomer-specific analysis of metolachlor requires not only enantioselective ("chiral") analytical techniques but also suitable reference compounds. In this study, two of the four metolachlor isomers were isolated from rac-metolachlor in enantio- (ee > 98%) and diastereomerically pure forms by a combination of achiral and chiral high-performance liquid chromatography (HPLC). The two isomers were identified as the aSS- and the aRR-isomers by polarimetric measurements, in reference to previous data. The two isomers were then thermally equilibrated to 1:1 mixtures of the aSS/aRS and aRR/aSR diastereomers, respectively, so that analytical data of all four metolachlor isomers became available; they were then used to identify these isomers in technical products by chiral high-resolution gas chromatography (HRGC). The kinetics of the thermally induced interconversion of the atropisomers was studied and the consequences, such as for GC analysis, are discussed. A comparison of on-column and split/splitless injection indicated that the latter technique results in significant isomerization prior to separation and, therefore, cannot be used for accurate isomer analysis.

  9. Determination of alkylamines in atmospheric aerosol particles: a comparison of gas chromatography-mass spectrometry and ion chromatography approaches

    NASA Astrophysics Data System (ADS)

    Huang, R.-J.; Li, W.-B.; Wang, Y.-R.; Wang, Q. Y.; Jia, W. T.; Ho, K.-F.; Cao, J. J.; Wang, G. H.; Chen, X.; Haddad, I. EI; Zhuang, Z. X.; Wang, X. R.; Prévôt, A. S. H.; O'Dowd, C. D.; Hoffmann, T.

    2014-07-01

    In recent years low molecular weight alkylamines have been recognized to play an important role in particle formation and growth in the lower atmosphere. However, major uncertainties are associated with their atmospheric processes, sources and sinks, mostly due to the lack of ambient measurements and the difficulties in accurate quantification of alkylamines at trace level. In this study, we present the evaluation and optimization of two analytical approaches, i.e., gas chromatography-mass spectrometry (GC-MS) and ion chromatography (IC), for the determination of alkylamines in aerosol particles. Alkylamines were converted to carbamates through derivatization with isobutyl chloroformate for GC-MS determination. A set of parameters affecting the analytical performances of the GC-MS approach, including reagent amount, reaction time and pH value, was evaluated and optimized. The accuracy is 84.3-99.1%, and the limits of detection obtained are 1.8-3.9 pg (or 0.02-0.04 ng m-3). For the IC approach, a solid-phase extraction (SPE) column was used to separate alkylamines from interfering cations before IC analysis. 1-2% (v/v) of acetone (or 2-4% (v/v) of acetonitrile) was added to the eluent to improve the separation of alkylamines on the IC column. The limits of detection obtained are 2.1-15.9 ng (or 0.9-6.4 ng m-3), and the accuracy is 55.1-103.4%. The lower accuracy can be attributed to evaporation losses of amines during the sample concentration procedure. Measurements of ambient aerosol particle samples collected in Hong Kong show that the GC-MS approach is superior to the IC approach for the quantification of primary and secondary alkylamines due to its lower detection limits and higher accuracy.

  10. Determination of alkyl amines in atmospheric aerosol particles: a comparison of gas chromatography-mass spectrometry and ion chromatography approaches

    NASA Astrophysics Data System (ADS)

    Huang, R.-J.; Li, W.-B.; Wang, Y.-R.; Wang, Q. Y.; Ho, K.-F.; Cao, J. J.; Wang, G. H.; Chen, X.; Haddad, I. EI; Zhuang, Z. X.; Wang, X. R.; Prévôt, A. S. H.; O'Dowd, C. D.; Hoffmann, T.

    2014-03-01

    In recent years low molecular weight alkyl amines have been recognized to play an important role in particle formation and growth in the lower atmosphere. However, major uncertainties are associated with their atmospheric processes, sources and sinks, mostly due to the lack of ambient measurements and the difficulties in accurate quantification of alkyl amines at trace level. In this study, we present the evaluation and optimization of two analytical approaches, i.e., gas chromatography-mass spectrometry (GC-MS) and ion chromatography (IC), for the determination of alkyl amines in aerosol particles. Alkyl amines were converted to carbamates through derivatization with isobutyl chloroformate for GC-MS determination. A set of parameters affecting the analytical performances of the GC-MS approach, including reagent amount, reaction time and pH value, was evaluated and optimized. The accuracy is 84.3-99.1%, and the limits of detection obtained are 1.8-3.9 pg. For the IC approach, a solid phase extraction (SPE) column was used to separate alkyl amines from interfering cations before IC analysis. 1-2% (v/v) of acetone (or 2-4% (v/v) of acetonitrile) was added to the eluent to improve the separation of alkyl amines on the IC column. The limits of detection obtained are 2.1-15.9 ng and the accuracy is 55.1-103.4%. The lower accuracy can be attributed to evaporation losses of amines during the sample concentration procedure. Measurements of ambient aerosol particle samples collected in Hong Kong show that the GC-MS approach is superior to the IC approach for the quantification of primary and secondary alkyl amines due to its lower detection limits and higher accuracy.

  11. Identification and measurement of chlorinated organic pesticides in water by electron-capture gas chromatography

    USGS Publications Warehouse

    Lamar, William L.; Goerlitz, Donald F.; Law, LeRoy M.

    1965-01-01

    Pesticides, in minute quantities, may affect the regimen of streams, and because they may concentrate in sediments, aquatic organisms, and edible aquatic foods, their detection and their measurement in the parts-per-trillion range are considered essential. In 1964 the U.S. Geological Survey at Menlo Park, Calif., began research on methods for monitoring pesticides in water. Two systems were selected--electron-capture gas chromatography and microcoulometric-titration gas chromatography. Studies on these systems are now in progress. This report provides current information on the development and application of an electron-capture gas chromatographic procedure. This method is a convenient and extremely sensitive procedure for the detection and measurement of organic pesticides having high electron affinities, notably the chlorinated organic pesticides. The electron-affinity detector is extremely sensitive to these substances but it is not as sensitive to many other compounds. By this method, the chlorinated organic pesticide may be determined on a sample of convenient size in concentrations as low as the parts-per-trillion range. To insure greater accuracy in the identifications, the pesticides reported were separated and identified by their retention times on two different types of gas chromatographic columns.

  12. Separation and Detection of Toxic Gases with a Silicon Micromachined Gas Chromatography System

    NASA Technical Reports Server (NTRS)

    Kolesar, Edward S.; Reston, Rocky R.

    1995-01-01

    A miniature gas chromatography (GC) system was designed and fabricated using silicon micromachining and integrated circuit (IC) processing techniques. The silicon micromachined gas chromatography system (SMGCS) is composed of a miniature sample injector that incorporates a 10 microliter sample loop; a 0.9 meter long, rectangular shaped (300 micrometer width and 10 micrometer height) capillary column coated with a 0.2 micrometer thick copper phthalocyanine (CuPc) stationary phase; and a dual detector scheme based upon a CuPc-coated chemiresistor and a commercially available 125 micrometer diameter thermal conductivity detector (TCD) bead. Silicon micromachining was employed to fabricate the interface between the sample injector and the GC column, the column itself, and the dual detector cavity. A novel IC thin-film processing technique was developed to sublime the CuPc stationary phase coating on the column walls that were micromachined in the host silicon wafer substrate and Pyrex (r) cover plate, which were then electrostatically bonded together. The SMGCS can separate binary gas mixtures composed of parts-per-million (ppm) concentrations of ammonia (NH3) and nitrogen dioxide (NO2) when isothermally operated (55-80 degrees C). With a helium carrier gas and nitrogen diluent, a 10 microliter sample volume containing ammonia and nitrogen dioxide injected at 40 psi ((2.8 x 10(exp 5)Pa)) can be separated in less than 30 minutes.

  13. Continuous determination of volatile products in anaerobic fermenters by on-line capillary gas chromatography.

    PubMed

    Diamantis, V; Melidis, P; Aivasidis, A

    2006-07-28

    Bio-ethanol and biogas produced during the anaerobic conversion of organic compounds has been a subject of great interest since the oil crisis of the 1970s. In ethanol fermentation and anaerobic treatment of wastewaters, end-product (ethanol) and intermediate-products (short-chain fatty acids, SCFA) cause inhibition that results in reduced process efficiency. Control of these constituents is of utmost importance for bioreactor optimization and process stability. Ethanol and SCFA can be detected with precision by capillary gas chromatography usually conducted in off-line measurements. In this work, an on-line monitoring and controlling system was developed and connected to the fermenter via an auto-sampling equipment, which could perform the feeding, filtration and dilution of the sample and final injection into the gas chromatograph through an automation-based programmed procedure. The sample was continuously pumped from the recycle stream of the bioreactor and treated using a microfiltration unit. The concentrate was returned to the reactor while the permeate was quantitatively mixed with an internal standard solution. The system comprised of a gas chromatograph with the flow cell and one-shot sampler and a PC with the appropriate software. The on-line measurement of ethanol and SCFA, directly from the liquid phase of an ethanol fermenter and a high-rate continuous mode anaerobic digester, was accomplished by gas chromatography. Also, this monitoring and controlling system was proved to be effective in the continuous fermentation of alcohol-free beer.

  14. Gas Phase Chromatography of some Group 4, 5, and 6 Halides

    SciTech Connect

    Sylwester, Eric Robert

    1998-10-01

    Gas phase chromatography using The Heavy Element Volatility Instrument (HEVI) and the On Line Gas Apparatus (OLGA III) was used to determine volatilities of ZrBr4, HfBr4, RfBr4, NbBr5, TaOBr3, HaCl5, WBr6, FrBr, and BiBr3. Short-lived isotopes of Zr, Hf, Rf, Nb, Ta, Ha, W, and Bi were produced via compound nucleus reactions at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory and transported to the experimental apparatus using a He gas transport system. The isotopes were halogenated, separated from the other reaction products, and their volatilities determined by isothermal gas phase chromatography. Adsorption Enthalpy (ΔHa) values for these compounds were calculated using a Monte Carlo simulation program modeling the gas phase chromatography column. All bromides showed lower volatility than molecules of similar molecular structures formed as chlorides, but followed similar trends by central element. Tantalum was observed to form the oxybromide, analogous to the formation of the oxychloride under the same conditions. For the group 4 elements, the following order in volatility and ΔHa was observed: RfBr4 > ZrBr4 > HfBr4. The ΔHa values determined for the group 4, 5, and 6 halides are in general agreement with other experimental data and theoretical predictions. Preliminary experiments were performed on Me-bromides. A new measurement of the half-life of 261Rf was performed. 261Rf was produced via the 248Cm(18O, 5n) reaction and observed with a half-life of 74-6+7 seconds, in excellent agreement with the previous measurement of 78-6+11 seconds. We recommend a new half-life of 75±7 seconds for 261Rf based on these two measurements. Preliminary studies in transforming HEVI from an isothermal (constant

  15. The characterization of eight maceral concentrates by means of Curie point pyrolysis-gas chromatography and Curie point pyrolysis-gas chromatography-mass spectrometry

    NASA Astrophysics Data System (ADS)

    Nip, Margriet; De Leeuw, J. W.; Schenck, P. A.

    1988-03-01

    In order to study the relationships between the chemical structures of coals, coal macerals and their precursors (plant tissues), eight coal macerals originating from the Yorkshire coal basin (U.K.) were studied by Curie point pyrolysis-gas chromatography and Curie point pyrolysis-gas chromatography-mass spectrometry. The samples were selected on the basis of a previous study of a large set of macerals. The macerals were studied in order to relate structural moieties of the macerals, as reflected by their pyrolysis products, to structural elements of their likely precursors, plant tissues. The maceral pyrolysates mainly consist of alkylbenzenes, alkylnaphthalenes, alkylphenols and series of straight-chain alk-l-enes and alkanes over a wide molecular weight range. The relative contribution of the (hydroxy)aromatic pyrolysis products and of the straight-chain alk-l-enes and alkanes to each maceral pyrolysate was calculated, although the internal distribution patterns of the alkyl derivatives of these pyrolysis products exhibited to a certain extent dissimilarities. Differences between the relative contributions of these pyrolysis products to the pyrolysates of different macerals with the same coal rank and to those of similar macerals with different coal rank depend on differences in precursor material and the chemical modification of these precursors upon increasing coalification. Multivariate data treatment by means of factor analysis was chosen to compare the pyrolysis data - represented by these histograms - with the petrographic data and the proximate and ultimate analysis values of the macerals. In addition, similar analyses was performed on the macerals using such a low Curie temperature (358°C), that from some of the macerals "thermal extracts" were obtained, containing a series of n-alkanes and some isoprenoids such as pristane and phytane. Although these thermal extracts represent only a low percentage by weight of the maceral samples, their existence

  16. An evolution from 3D face-centered-cubic ZnSnO3 nanocubes to 2D orthorhombic ZnSnO3 nanosheets with excellent gas sensing performance.

    PubMed

    Chen, Yuejiao; Yu, Ling; Li, Qing; Wu, Yan; Li, Qiuhong; Wang, Taihong

    2012-10-19

    We have successfully observed the development of three-dimensional (3D) face-centered-cubic ZnSnO(3) into two-dimensional (2D) orthorhombic ZnSnO(3) nanosheets, which is the first observation of 2D ZnSnO(3) nanostructures to date. The synthesis from 3D to 2D nanostructures is realized by the dual-hydrolysis-assisted liquid precipitation reaction and subsequent hydrothermal treatment. The time-dependent morphology indicates the transformation via a 'dissolution-recrystallization' mechanism, accompanied by a 'further growth' process. Furthermore, the 2D ZnSnO(3) nanosheets consist of smaller sized nanoflakes. This further increases the special specific surface area and facilitates their application in gas sensing. The 2D ZnSnO(3) nanosheets exhibit excellent gas sensing properties, especially through their ultra-fast response and recovery. When exposed to ethanol and acetone, the response rate is as fast as 0.26 s and 0.18 s, respectively, and the concentration limit can reach as low as 50 ppb of ethanol. All these results are much better than those reported so far. Our experimental results indicate an efficient approach to realize high-performance gas sensors.

  17. Metabolomics by Gas Chromatography-Mass Spectrometry: the combination of targeted and untargeted profiling

    PubMed Central

    Fiehn, Oliver

    2016-01-01

    Gas chromatography-mass spectrometry (GC-MS)-based metabolomics is ideal for identifying and quantitating small molecular metabolites (<650 daltons), including small acids, alcohols, hydroxyl acids, amino acids, sugars, fatty acids, sterols, catecholamines, drugs, and toxins, often using chemical derivatization to make these compounds volatile enough for gas chromatography. This unit shows that on GC-MS- based metabolomics easily allows integrating targeted assays for absolute quantification of specific metabolites with untargeted metabolomics to discover novel compounds. Complemented by database annotations using large spectral libraries and validated, standardized standard operating procedures, GC-MS can identify and semi-quantify over 200 compounds per study in human body fluids (e.g., plasma, urine or stool) samples. Deconvolution software enables detection of more than 300 additional unidentified signals that can be annotated through accurate mass instruments with appropriate data processing workflows, similar to liquid chromatography-MS untargeted profiling (LC-MS). Hence, GC-MS is a mature technology that not only uses classic detectors (‘quadrupole’) but also target mass spectrometers (‘triple quadrupole’) and accurate mass instruments (‘quadrupole-time of flight’). This unit covers the following aspects of GC-MS-based metabolomics: (i) sample preparation from mammalian samples, (ii) acquisition of data, (iii) quality control, and (iv) data processing. PMID:27038389

  18. Fast and accurate numerical method for predicting gas chromatography retention time.

    PubMed

    Claumann, Carlos Alberto; Wüst Zibetti, André; Bolzan, Ariovaldo; Machado, Ricardo A F; Pinto, Leonel Teixeira

    2015-08-07

    Predictive modeling for gas chromatography compound retention depends on the retention factor (ki) and on the flow of the mobile phase. Thus, different approaches for determining an analyte ki in column chromatography have been developed. The main one is based on the thermodynamic properties of the component and on the characteristics of the stationary phase. These models can be used to estimate the parameters and to optimize the programming of temperatures, in gas chromatography, for the separation of compounds. Different authors have proposed the use of numerical methods for solving these models, but these methods demand greater computational time. Hence, a new method for solving the predictive modeling of analyte retention time is presented. This algorithm is an alternative to traditional methods because it transforms its attainments into root determination problems within defined intervals. The proposed approach allows for tr calculation, with accuracy determined by the user of the methods, and significant reductions in computational time; it can also be used to evaluate the performance of other prediction methods.

  19. Metabolomics by Gas Chromatography-Mass Spectrometry: Combined Targeted and Untargeted Profiling.

    PubMed

    Fiehn, Oliver

    2016-04-01

    Gas chromatography-mass spectrometry (GC-MS)-based metabolomics is ideal for identifying and quantitating small-molecule metabolites (<650 Da), including small acids, alcohols, hydroxyl acids, amino acids, sugars, fatty acids, sterols, catecholamines, drugs, and toxins, often using chemical derivatization to make these compounds sufficiently volatile for gas chromatography. This unit shows how GC-MS-based metabolomics allows integration of targeted assays for absolute quantification of specific metabolites with untargeted metabolomics to discover novel compounds. Complemented by database annotations using large spectral libraries and validated standard operating procedures, GC-MS can identify and semiquantify over 200 compounds from human body fluids (e.g., plasma, urine, or stool) per study. Deconvolution software enables detection of more than 300 additional unidentified signals that can be annotated through accurate mass instruments with appropriate data processing workflows, similar to untargeted profiling using liquid chromatography-mass spectrometry. GC-MS is a mature technology that uses not only classic detectors (quadrupole) but also target mass spectrometers (triple quadrupole) and accurate mass instruments (quadrupole-time of flight). This unit covers sample preparation from mammalian samples, data acquisition, quality control, and data processing.

  20. Complete elution of vacuum gas oil resins by comprehensive high-temperature two-dimensional gas chromatography.

    PubMed

    Boursier, Laure; Souchon, Vincent; Dartiguelongue, Cyril; Ponthus, Jérémie; Courtiade, Marion; Thiébaut, Didier

    2013-03-08

    The development of efficient conversion processes requires extended knowledge on vacuum gas oils (VGOs). Among these processes, hydrocracking is certainly one of the best suited to meet the increasing demand on high quality diesel fuels. Most of refractory and inhibiting compounds towards hydrocracking and especially nitrogen containing compounds are contained in a fraction of the VGO called the resin fraction, which corresponds to the most polar fraction of a VGO obtained by liquid chromatography (LC) fractionation on a silica column. However, the lack of resolution observed through existing analytical methods does not allow a detailed characterization of these fractions. A recent study showed that comprehensive high temperature two-dimensional gas chromatography (HT-GC×GC) methods could be optimized in order to elute heavy compounds. This method was implemented for the analysis of VGO resin fractions and complete elution was reached. Firstly, the method was validated through repeatability, accuracy, linearity and response factors calculations. Four VGO resin fractions were analyzed and their HT-GC×GC simulated distillation curves were compared to their GC simulated distillation (GC-SimDist) curves. This comparison showed that the method allows complete elution of most of the analyzed VGO resin fractions. However, a detailed characterization of these fractions is not yet obtained due to the very large number of heteroatomic and aromatic species that a flame ionization detector can detect. Current work aims at increasing the selectivity of GC×GC by using heteroatom selective detectors in order to improve the characterization of such products.

  1. Detection of ergot (Claviceps purpurea) in a dairy feed component by gas chromatography and mass spectrometry.

    PubMed

    Mantle, P G

    1996-11-01

    A dairy feed that contained barley malt screenings caused hyperthermia in dairy cattle. The feed was suspected of containing ergot and was subsequently analyzed to determine the ricinoleate component, a special and prominent feature of oil-rich ergot tissue. Triglyceride oil was extracted by organic solvents from the dairy feed, and the oil was saponified to release fatty acids. Ricinoleate, as a methyl ester, was selectively resolved from other fatty acids by silica gel chromatography and was analyzed by capillary gas chromatography coupled with chemical ionization mass spectrometry, which demonstrated the presence of the methyl ricinoleate molecule and proved that the feed contained ergot. The methodology may be refined to monitor for ergot in powdered dairy feed more routinely.

  2. Global urinary metabolic profiling procedures using gas chromatography-mass spectrometry.

    PubMed

    Chan, Eric Chun Yong; Pasikanti, Kishore Kumar; Nicholson, Jeremy K

    2011-09-08

    The role of urinary metabolic profiling in systems biology research is expanding. This is because of the use of this technology for clinical diagnostic and mechanistic studies and for the development of new personalized health care and molecular epidemiology (population) studies. The methodologies commonly used for metabolic profiling are NMR spectroscopy, liquid chromatography mass spectrometry (LC/MS) and gas chromatography-mass spectrometry (GC/MS). In this protocol, we describe urine collection and storage, GC/MS and data preprocessing methods, chemometric data analysis and urinary marker metabolite identification. Results obtained using GC/MS are complementary to NMR and LC/MS. Sample preparation for GC/MS analysis involves the depletion of urea via treatment with urease, protein precipitation with methanol, and trimethylsilyl derivatization. The protocol described here facilitates the metabolic profiling of ∼400-600 metabolites in 120 urine samples per week.

  3. Profiling analysis of volatile compounds from fruits using comprehensive two-dimensional gas chromatography and image processing techniques.

    PubMed

    Schmarr, Hans-Georg; Bernhardt, Jörg

    2010-01-22

    An image processing approach originating from the proteomics field has been transferred successfully to the processing of data obtained with comprehensive two-dimensional gas chromatographic separations data. The approach described here has proven to be a useful analytical tool for unbiased pattern comparison or profiling analyses, as demonstrated with the differentiation of volatile patterns ("aroma") from fruits such as apples, pears, and quince fruit. These volatile patterns were generated by headspace solid phase microextraction coupled to comprehensive two-dimensional gas chromatography (HS-SPME-GC x GC). The data obtained from GC x GC chromatograms were used as contour plots which were then converted to gray-scale images and analyzed utilizing a workflow derived from 2D gel-based proteomics. Run-to-run variations between GC x GC chromatograms, respectively their contour plots, have been compensated by image warping. The GC x GC images were then merged into a fusion image yielding a defined and project-wide spot (peak) consensus pattern. Within detected spot boundaries of this consensus pattern, relative quantities of the volatiles from each GC x GC image have been calculated, resulting in more than 700 gap free volatile profiles over all samples. These profiles have been used for multivariate statistical analysis and allowed clustering of comparable sample origins and prediction of unknown samples. At present state of development, the advantage of using mass spectrometric detection can only be realized by data processing off-line from the identified software packages. However, such information provides a substantial basis for identification of statistically relevant compounds or for a targeted analysis.

  4. Gas chromatography-vacuum ultraviolet spectroscopy for analysis of fatty acid methyl esters.

    PubMed

    Fan, Hui; Smuts, Jonathan; Bai, Ling; Walsh, Phillip; Armstrong, Daniel W; Schug, Kevin A

    2016-03-01

    A new vacuum ultraviolet (VUV) detector for gas chromatography was recently developed and applied to fatty acid methyl ester (FAME) analysis. VUV detection features full spectral acquisition in a wavelength range of 115-240nm, where virtually all chemical species absorb. VUV absorption spectra of 37 FAMEs, including saturated, monounsaturated, and polyunsaturated types were recorded. Unsaturated FAMEs show significantly different gas phase absorption profiles than saturated ones, and these classes can be easily distinguished with the VUV detector. Another advantage includes differentiating cis/trans-isomeric FAMEs (e.g. oleic acid methyl ester and linoleic acid methyl ester isomers) and the ability to use VUV data analysis software for deconvolution of co-eluting signals. As a universal detector, VUV also provides high specificity, sensitivity, and a fast data acquisition rate, making it a powerful tool for fatty acid screening when combined with gas chromatography. The fatty acid profile of several food oil samples (olive, canola, vegetable, corn, sunflower and peanut oils) were analyzed in this study to demonstrate applicability to real world samples.

  5. Determination of vaporization enthalpies of the branched esters from correlation gas chromatography and transpiration methods

    SciTech Connect

    Verevkin, S.P.; Heintz, A.

    1999-12-01

    Vaporization enthalpies are indispensable for the assessment of the environmental fate and behavior of environmental contaminants. The temperature dependencies of retention indices of a set of 80 esters with branched molecular structures were measured on a nonpolar gas chromatographic column. The correlation gas chromatography method and reliable data set of 16 esters selected from the literature were used to derive a correlation for the prediction of the standard molar enthalpies of vaporization {Delta}{sub 1}{sup g}H{sub m}{sup {degree}} at the temperature T = 298.15 K. Experimental values of {Delta}{sub 1}{sup g}H{sub m}{sup {degree}} for 64 branched esters were obtained with the help of this correlation. The vaporization enthalpies of isopentyl acetate, ethyl hexanoate, and neopentyl pivalate were additionally obtained by the transpiration method from the temperature dependence of the vapor pressure measured in a flow system and used for checking the validity of the correlation gas chromatography method.

  6. Multiple inert gas elimination technique by micropore membrane inlet mass spectrometry--a comparison with reference gas chromatography.

    PubMed

    Kretzschmar, Moritz; Schilling, Thomas; Vogt, Andreas; Rothen, Hans Ulrich; Borges, João Batista; Hachenberg, Thomas; Larsson, Anders; Baumgardner, James E; Hedenstierna, Göran

    2013-10-15

    The mismatching of alveolar ventilation and perfusion (VA/Q) is the major determinant of impaired gas exchange. The gold standard for measuring VA/Q distributions is based on measurements of the elimination and retention of infused inert gases. Conventional multiple inert gas elimination technique (MIGET) uses gas chromatography (GC) to measure the inert gas partial pressures, which requires tonometry of blood samples with a gas that can then be injected into the chromatograph. The method is laborious and requires meticulous care. A new technique based on micropore membrane inlet mass spectrometry (MMIMS) facilitates the handling of blood and gas samples and provides nearly real-time analysis. In this study we compared MIGET by GC and MMIMS in 10 piglets: 1) 3 with healthy lungs; 2) 4 with oleic acid injury; and 3) 3 with isolated left lower lobe ventilation. The different protocols ensured a large range of normal and abnormal VA/Q distributions. Eight inert gases (SF6, krypton, ethane, cyclopropane, desflurane, enflurane, diethyl ether, and acetone) were infused; six of these gases were measured with MMIMS, and six were measured with GC. We found close agreement of retention and excretion of the gases and the constructed VA/Q distributions between GC and MMIMS, and predicted PaO2 from both methods compared well with measured PaO2. VA/Q by GC produced more widely dispersed modes than MMIMS, explained in part by differences in the algorithms used to calculate VA/Q distributions. In conclusion, MMIMS enables faster measurement of VA/Q, is less demanding than GC, and produces comparable results.

  7. Comprehensive two-dimensional gas chromatography applied to illicit drug analysis.

    PubMed

    Mitrevski, Blagoj; Wynne, Paul; Marriott, Philip J

    2011-11-01

    Multidimensional gas chromatography (MDGC), and especially its latest incarnation--comprehensive two-dimensional gas chromatography (GC × GC)--have proved advantageous over and above classic one-dimensional gas chromatography (1D GC) in many areas of analysis by offering improved peak capacity, often enhanced sensitivity and, especially in the case of GC × GC, the unique feature of 'structured' chromatograms. This article reviews recent advances in MDGC and GC × GC in drug analysis with special focus on ecstasy, heroin and cocaine profiling. Although 1D GC is still the method of choice for drug profiling in most laboratories because of its simplicity and instrument availability, GC × GC is a tempting proposition for this purpose because of its ability to generate a higher net information content. Effluent refocusing due to the modulation (compression) process, combined with the separation on two 'orthogonal' columns, results in more components being well resolved and therefore being analytically and statistically useful to the profile. The spread of the components in the two-dimensional plots is strongly dependent on the extent of retention 'orthogonality' (i.e. the extent to which the two phases possess different or independent retention mechanisms towards sample constituents) between the two columns. The benefits of 'information-driven' drug profiling, where more points of reference are usually required for sample differentiation, are discussed. In addition, several limitations in application of MDGC in drug profiling, including data acquisition rate, column temperature limit, column phase orthogonality and chiral separation, are considered and discussed. Although the review focuses on the articles published in the last decade, a brief chronological preview of the profiling methods used throughout the last three decades is given.

  8. Determination of Surface Energy of Natural Zeolite by Inverse Gas Chromatography

    NASA Astrophysics Data System (ADS)

    Bilgiç, Ceyda; Karakehya, Naile

    2016-10-01

    In this study, surface energy of natural zeolite was investigated using inverse gas chromatography (IGC). Purified zeolite was prepared from natural zeolite applying decantation and centrifugation process together. For IGC studies, retention time of n-octane, n-nonane and n-decane were measured at infinite dilution conditions, between 250 and 280 °C. Dispersive component of the surface energy (γd S)of purified zeolite was calculated. γd S values calculated using Schultz et al methods decrease with temperature.

  9. Analysis of the citric acid cycle intermediates using gas chromatography-mass spectrometry.

    PubMed

    Kombu, Rajan S; Brunengraber, Henri; Puchowicz, Michelle A

    2011-01-01

    Researchers view analysis of the citric acid cycle (CAC) intermediates as a metabolomic approach to identifying unexpected correlations between apparently related and unrelated pathways of metabolism. Relationships of the CAC intermediates, as measured by their concentrations and relative ratios, offer useful information to understanding interrelationships between the CAC and metabolic pathways under various physiological and pathological conditions. This chapter presents a relatively simple method that is sensitive for simultaneously measuring concentrations of CAC intermediates (relative and absolute) and other related intermediates of energy metabolism using gas chromatography-mass spectrometry.

  10. Acid-base and surface energy characterization of grafted polyethylene using inverse gas chromatography.

    PubMed

    Uhlmann, Petra; Schneider, Steffen

    2002-09-06

    For a specific design of interfaces, i.e. in composites and blends, it is essential to know the surface thermodynamics of the components. Polyethylene grafted with maleic anhydride and maleic anhydride-styrene mixtures, respectively, was the component of interest of our investigations. Inverse gas chromatography (IGC) at infinite dilution was shown to be an appropriate method to evaluate the dispersive and acid-base surface characteristics although there is an influence of bulk absorption and morphology when performing IGC above the glass transition temperature of the polymer.

  11. Simple, specific analysis of organophosphorus and carbamate pesticides in sediments using column extraction and gas chromatography

    USGS Publications Warehouse

    Belisle, A.A.; Swineford, D.M.

    1988-01-01

    A simple, specific procedure was developed for the analysis of organophosphorus and carbamate pesticides in sediment. The wet soil was mixed with anhydrous sodium sulfate to bind water and the residues were column extracted in acetone:methylene chloride (1:l,v/v). Coextracted water was removed by additional sodium sulfate packed below the sample mixture. The eluate was concentrated and analyzed directly by capillary gas chromatography using phosphorus and nitrogen specific detectors. Recoveries averaged 93 % for sediments extracted shortly after spiking, but decreased significantly as the samples aged.

  12. [Quantitative determination of strychnine in blood and urine by gas chromatography with mass-selective detector].

    PubMed

    Kataev, S S; Krylova, E A

    2010-01-01

    A method for the quantitative determination of strychnine in biological fluids by gas chromatography--mass spectrometry is proposed. The preparation of samples for the analysis included extraction of strychnine from blood and urine with the use of AccuBond(II) EVIDEX cartridges for solid-phase extraction and SPEC MP3 disks respectively. The efficiency of extraction was estimated at 0.05 mg/l for blood and 0.02 mg/l for urine. The detection limit was 0.10 mg/l in blood and 0.05 mg/l in urine.

  13. Analysis of the anthraquinones aloe-emodin and aloin by gas chromatography/mass spectrometry.

    PubMed

    ElSohly, Mahmoud A; Gul, Waseem; Murphy, Timothy P

    2004-12-20

    A procedure was developed for the determination of low levels of the anthraquinones aloe-emodin and aloin A (barbalin) in aloe products based on gas chromatography/mass spectrometry (GC/MS) of the trimethyl silyl (TMS) derivatives of these analytes in the presence of Chrysophanol used as internal standard. The method was used to analyze several aloe based commercial products (liquids, gels and solids). Wide variation in the level of these anthraquinones was observed among the different products. The method had a sensitivity of 0.005 ppm of aloe-emodin and 0.05 ppm of aloin.

  14. Gas chromatography/mass spectrometry characterization of historical varnishes of ancient Italian lutes and violin.

    PubMed

    Echard, J P; Benoit, C; Peris-Vicente, J; Malecki, V; Gimeno-Adelantado, J V; Vaiedelich, S

    2007-02-12

    The organic constituents of historical vanishes from two ancient Italian lutes and a Stradivari violin, kept in the Musée de la musique in Paris, have been characterized using gas chromatography-mass spectrometry. Results have been compared with the chromatograms and mass spectra of recent as well as old naturally aged reference materials. The three historical varnishes analyzed have been shown to be oil varnishes, probably mixtures of linseed oil with resins. Identification of diterpenoids and triterpenoids compounds, and of the resins that may have been ingredients of the varnishes, are discussed in this paper.

  15. Inverse gas chromatography. V - Computer simulation of diffusion processes on the column

    NASA Technical Reports Server (NTRS)

    Hattam, Paul; Munk, Petr

    1988-01-01

    The elution behavior of low molecular weight probes on inverse gas chromatography (IGC) columns is simulated using a computer. The IGC model is based on a polymer stationary phase of uniform thickness with a nonnegligible resitance to probe penetration. Three characteristic numbers are found to determine the whole process: Z(p) characterizing the distribution of the probe between phases, Z(f) describing the diffusion in the polymer phase, and Z(g) related to diffusion in the gaseous phase. For situations when Z(p)/Z(f) is less than 2, the standard evaluation procedures are virtually useless. The actual behavior of such systems is described.

  16. [Gas chromatography in quantitative analysis of hydrocyanic acid and its salts in cadaveric blood].

    PubMed

    Iablochkin, V D

    2003-01-01

    A direct gas chromatography method was designed for the quantitative determination of cyanides (prussic acid) in cadaveric blood. Its sensitivity is 0.05 mg/ml. The routine volatile products, including substances, which emerge due to putrefaction of organic matters, do not affect the accuracy and reproducibility of the method; the exception is H-propanol that was used as the internal standard. The method was used in legal chemical expertise related with acute cyanide poisoning (suicide) as well as with poisoning of products of combustion of nonmetals (foam-rubber). The absolute error does not exceed 10% with a mean quadratic deviation of 0.0029-0.0033 mg.

  17. Screening of Brazilian fruit aromas using solid-phase microextraction-gas chromatography-mass spectrometry.

    PubMed

    Augusto, F; Valente, A L; dos Santos Tada, E; Rivellino, S R

    2000-03-17

    Manual headspace solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) was used for the qualitative analysis of the aromas of four native Brazilian fruits: cupuassu (Theobroma grandiflorum, Spreng.), cajá (Spondias lutea. L.), siriguela (Spondias purpurea, L.) and graviola (Anona reticulata, L). Industrialized pulps of these fruits were used as samples, and extractions with SPME fibers coated with polydimethylsiloxane, polyacrylate, Carbowax and Carboxen were carried out. The analytes identified included several alcohols, esters, carbonyl compounds and terpernoids. The highest amounts extracted, evaluated from the sum of peak areas, were achieved using the Carboxen fiber.

  18. Analysis of volatile organic compounds in groundwater samples by gas chromatography-mass spectrometry

    SciTech Connect

    Bernhardt, J.

    1995-08-23

    The Savannah River Site contains approximately 1500 monitoring wells from which groundwater samples are collected. Many of these samples are sent off-site for various analyses, including the determination of trace volatile organic compounds (VOCs). This report describes accomplishments that have been made during the past year which will ultimately allow VOC analysis to be performed on-site using gas chromatography-mass spectrometry. Through the use of the on-site approach, it is expected that there will be a substantial cost savings. This approach will also provide split-sample analysis capability which can serve as a quality control measure for off-site analysis.

  19. Comparison of photoacoustic radiometry to gas chromatography/mass spectrometry methods for monitoring chlorinated hydrocarbons

    SciTech Connect

    Sollid, J.E.; Trujillo, V.L.; Limback, S.P.; Woloshun, K.A.

    1996-03-01

    A comparison of two methods of gas chromatography mass spectrometry (GCMS) and a nondispersive infrared technique, photoacoustic radiometry (PAR), is presented in the context of field monitoring a disposal site. First is presented an historical account describing the site and early monitoring to provide an overview. The intent and nature of the monitoring program changed when it was proposed to expand the Radiological Waste Site close to the Hazardous Waste Site. Both the sampling methods and analysis techniques were refined in the course of this exercise.

  20. 40 CFR Appendix 5 to Subpart A of... - Determination of Crude Oil Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography/Mass Spectrometry (GC/MS) (EPA Method 1655) 5... Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography/Mass Spectrometry (GC/MS) (EPA Method 1655) 1... oil contamination, in non-aqueous drilling fluids (NAFs) by comparing the gas...

  1. 40 CFR Appendix 5 to Subpart A of... - Determination of Crude Oil Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography/Mass Spectrometry (GC/MS) (EPA Method 1655) 5... Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography/Mass Spectrometry (GC/MS) (EPA Method 1655) 1... oil contamination, in non-aqueous drilling fluids (NAFs) by comparing the gas...

  2. 40 CFR Appendix 5 to Subpart A of... - Determination of Crude Oil Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography/Mass Spectrometry (GC/MS) (EPA Method 1655) 5... Contamination in Non-Aqueous Drilling Fluids by Gas Chromatography/Mass Spectrometry (GC/MS) (EPA Method 1655) 1... oil contamination, in non-aqueous drilling fluids (NAFs) by comparing the gas...

  3. Rapid gas analyses for the investigation of spontaneous combustion using capillary gas chromatography.

    PubMed

    Havenga, W J

    1993-02-01

    A simple and fast but sensitive and precise gas chromatographic method is described for the quantitative determination of O(2), N(2), CO, CO(2), C1 and C2-hydrocarbons for coal research. Gas analyses are necessary to obtain parameters for modelling spontaneous combustion and to predict long term coal behaviour. The method is based on a single PLOT-type capillary column in a single channel gas chromatograph. Using a micro-volume TCD coupled in series with a FID detector containing a capillary methanizer it is possible to determine high and trace level gases simultaneously. Trace quantities of CO and CO(2) can be determined with a single analysis and the detection limits are improved significantly using the capillary methanizer. The detection limit of the described method is approximately ten parts per million CO(2) and one part per million CO. Using the same instrument configuration the O(2)/N(2) ratios (major components), as parameter for coal reactivity, are also determined. The proposed approach is restricted to the determination of gases evolved during coal studies and the application to other gas mixtures is not considered.

  4. [Rapid determination of pesticide multiresidues in porphyra by dispersive solid-phase extraction coupled with online gel permeation chromatography-gas chromatography-mass spectrometry].

    PubMed

    Sun, Xiaojie; Guo, Mengmeng; Wang, Suyue; Tan, Zhijun; Li, Zhaoxin; Zhai, Yuxiu

    2014-10-01

    A rapid method for the simultaneous identification and quantification of pesticide multiresidues in porphyra was developed using gel permeation chromatography (GPC) coupled to gas chromatography-mass spectrometry (GPC-GC/MS). Nineteen pesticides (organochlorines, organophosphoruses, triazines and pyrethroids) were selected as the target analytes. The pretreatment method was applied consisting of organic solvent extraction followed by dispersive solid-phase extraction with graphitized carbon black (GCB) and primary secondary amine (PSA) adsorbents. GPC was also employed online to remove the large molecules such as pigments and lipids. The quantitative analysis was carried out by external standard method using gas chromatography coupled with mass spectrometry in selective ion monitoring (SIM) mode. Moreover, a large volume of sample was allowed to be injected using the program of GPC programmed-temperature vaporizer of gas chromatography to improve the sensitivity of measurements. The results showed that the calibration curves were linear (r > 0.995) in the range of 10-1,000 μg/L for all the pesticides. The limits of detection (LODs) for the pesticides in porphyra were from 0.005 to 0.03 mg/kg, and the average recoveries were between 70% and 120%. The advantages of the method are simple, sensitive and shorter operation time for analysis of pesticide residues in porphyra samples.

  5. Methods of analysis-Determination of pesticides in sediment using gas chromatography/mass spectrometry

    USGS Publications Warehouse

    Hladik, Michelle; McWayne, Megan M.

    2012-01-01

    A method for the determination of 119 pesticides in environmental sediment samples is described. The method was developed by the U.S. Geological Survey (USGS) in support of the National Water Quality Assessment (NAWQA) Program. The pesticides included in this method were chosen through prior prioritization. Herbicides, insecticides, and fungicides along with degradates are included in this method and span a variety of chemical classes including, but not limited to, chloroacetanilides, organochlorines, organophosphates, pyrethroids, triazines, and triazoles. Sediment samples are extracted by using an accelerated solvent extraction system (ASE®, and the compounds of interest are separated from co-extracted matrix interferences (including sulfur) by passing the extracts through high performance liquid chromatography (HPLC) with gel-permeation chromatography (GPC) along with the use of either stacked graphitized carbon and alumina solid-phase extraction (SPE) cartridges or packed Florisil®. Chromatographic separation, detection, and quantification of the pesticides from the sediment-sample extracts are done by using gas chromatography with mass spectrometry (GC/MS). Recoveries in test sediment samples fortified at 10 micrograms per kilogram (μg/kg) dry weight ranged from 75 to 102 percent; relative standard deviations ranged from 3 to 13 percent. Method detection limits (MDLs), calculated by using U.S. Environmental Protection Agency procedures (40 CFR 136, Appendix B), ranged from 0.6 to 3.4 μg/kg dry weight.

  6. Multidimensional gas chromatography of oxidative degradation products in algae-derived fuel oil samples using narrow heartcuts and rapid cycle times.

    PubMed

    Mitrevski, Blagoj; Webster, Renée L; Rawson, Paul; Evans, David J; Choi, Hyung-Kyoon; Marriott, Philip J

    2012-02-10

    To characterize a fuel's thermal and storage stability an understanding of the process of oxidation and oxidation pathways is essential. Oxidation pathways commence with hydroperoxides which quickly decompose to form a range of alcohols, acids and other oxygen-containing species. In the presence of significant levels of hydrocarbon-based matrix, analysis of these heteroatomic species is difficult. Applying multidimensional gas chromatography with very narrow heart-cut windows (0.20 min) minimizes the number of compounds transferred to the second dimension (2D) column during each heart-cut. Successive heart-cuts every 2.00 min are taken throughout the analytical run, since each heart-cut has a maximum retention on 2D of <2.00 min on the fast elution 2D column. Subsequent analyses involve incrementing or offsetting the heart-cut windows by 0.20 min, so after 10 analyses, a complete coverage of the sample components can be obtained. On the polar 1D and non-polar 2D phase column arrangement, non-polar matrix compounds elute last on the 2D column, and this determines the largest (2t)R; i.e., (2t)R < P(M) to ensure retained components on 2D will not overlap with subsequent heart-cuts. Heartcutting is supported by cryotrapping at the start of the 2D column in order to provide significantly better resolution. Good quality MS library match data generally demonstrate the high resolution separation of oxygenates achieved. Whilst 1D GC-MS was unsuccessful in identifying any of the oxygen-containing compounds reported here, good correlation of MS data (with average MS library similarity data) for acids (903), alcohols (909), ketones (941) and aldehydes (938) in the sample is obtained. The method requires ten sequential runs, and this can be accomplished automatically once the events table is set up. However if fewer target compounds are to be transferred, a reduced number of sequential runs can be implemented.

  7. A sensitive gas chromatography detector based on atmospheric pressure chemical ionization by a dielectric barrier discharge.

    PubMed

    Kirk, Ansgar T; Last, Torben; Zimmermann, Stefan

    2017-02-03

    In this work, we present a novel concept for a gas chromatography detector utilizing an atmospheric pressure chemical ionization which is initialized by a dielectric barrier discharge. In general, such a detector can be simple and low-cost, while achieving extremely good limits of detection. However, it is non-selective apart from the use of chemical dopants. Here, a demonstrator manufactured entirely from fused silica capillaries and printed circuit boards is shown. It has a size of 75×60×25mm(3) and utilizes only 2W of power in total. Unlike other known discharge detectors, which require high-purity helium, this detector can theoretically be operated using any gas able to form stable ion species. Here, purified air is used. With this setup, limits of detection in the low parts-per-billion range have been obtained for acetone.

  8. Gas-liquid chromatography-mass spectrometry of synthetic ceramides containing phytosphingosine.

    PubMed

    Hammarström, S

    1970-05-01

    Ceramides containing phytosphingosine as base and one of the fatty acids 16:0, 18:0, 20:0, 22:0, 23:0, and 24:0, were prepared by direct coupling in the presence of a mixed carbodiimide. The ceramides were analyzed as the 1,3,4-tri-O-trimethylsilyl ether derivatives by gas-liquid chromatography-mass spectrometry. Gas chromatographic data is presented, and structures of mass spectral ions are suggested. The structures are supported by mass spectra of the homologous ceramides, by deuterium-labeling experiments, and by high resolution mass spectrometry. Some ions, formed by cleavage between C-3 and C-4 in the long-chain base, indicate the phytosphingosine nature of the ceramide.

  9. Forensic analysis of ignitable liquids in fire debris by comprehensive two-dimensional gas chromatography.

    PubMed

    Frysinger, Glenn S; Gaines, Richard B

    2002-05-01

    The application of comprehensive two-dimensional gas chromatography (GC x GC) for the forensic analysis of ignitable liquids in fire debris is reported. GC x GC is a high resolution, multidimensional gas chromatographic method in which each component of a complex mixture is subjected to two independent chromatographic separations. The high resolving power of GC x GC can separate hundreds of chemical components from a complex fire debris extract. The GC x GC chromatogram is a multicolor plot of two-dimensional retention time and detector signal intensity that is well suited for rapid identification and fingerprinting of ignitable liquids. GC x GC chromatograms were used to identify and classify ignitable liquids, detect minor differences between similar ignitable liquids, track the chemical changes associated with weathering, characterize the chemical composition of fire debris pyrolysates, and detect weathered ignitable liquids against a background of fire debris pyrolysates.

  10. Rapid determination of cholesterol in milk and milk products by direct saponification and capillary gas chromatography.

    PubMed

    Fletouris, D J; Botsoglou, N A; Psomas, I E; Mantis, A I

    1998-11-01

    A simple method is described for the determination of cholesterol in milk and milk products. Samples (0.2 g) are saponified in capped tubes with 0.5 M methanolic KOH solution by heating for 15 min at 80 degrees C. Water is added to the mixtures, and the unsaponifiable fractions are extracted with hexane to be further analyzed by capillary gas chromatography. Because of the rapid sample preparation and gas chromatographic procedures, a single sample can be analyzed in 30 min. Overall recovery was 98.6%, and the linearity was excellent for the fortification range examined. Precision data that were based on the variation within and between days suggested an overall relative standard deviation value of 1.4%. The method has been successfully applied to quantitate cholesterol in a variety of milk products.

  11. Enantiomeric analysis of limonene and carvone by direct introduction of aromatic plants into multidimensional gas chromatography.

    PubMed

    Barba, C; Toledano, R M; Santa-María, G; Herraiz, M; Martínez, R M

    2013-03-15

    Analysis of chiral compounds in complex mixtures is achieved by multidimensional gas chromatography using heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin stationary phase as the main column of the system to separate specific selected cuts containing components unresolved in the first dimension. The proposed procedure allows rapid analysis of both solid and liquid matrices by direct introduction, into the programmed temperature vaporizer (PTV) of a gas chromatograph, of either the plant material or the essential oil, respectively. A comparison between enantiomeric excesses data obtained, from plant leaves (or plant seeds) and the corresponding essential oils, by direct injection (i.e., without sample pretreatment or concentration step) into the multidimensional system is also included. Reported data demonstrate that no racemization occurs during analysis as identical enantiomeric excesses are obtained in both cases for specific chiral compounds.

  12. Direct determination of volatile compounds in spirit drinks by gas chromatography.

    PubMed

    Charapitsa, Siarhei V; Kavalenka, Anton N; Kulevich, Nikita V; Makoed, Nicolai M; Mazanik, Arkadzi L; Sytova, Svetlana N; Zayats, Natalia I; Kotov, Yurii N

    2013-03-27

    A way of direct determination of volatile compounds in spirit drinks by gas chromatography is proposed by using ethanol as internal standard in gas chromatographic analysis of volatile compounds in spirit drinks for routine tests. This method provides determination of volatile compound concentrations in spirit drinks expressed directly in milligrams per liter of absolute alcohol without measuring the alcohol content of the analyzed sample. Theoretical background of the method shows the opportunity to use it in any tested laboratories all over the world and to ascertain in its efficiency and simplicity. The method was approved in control laboratories of Wine and Distillery Plant "Chashniki" (Belarus) and Branch of Joint Stock Company "Rosspirtprom" Wine and Distillery Plant "Cheboksary" (Russia). The experimental results of method validation in the Laboratory of Analytical Research from Research Institute for Nuclear Problems of Belarusian State University are presented.

  13. Characterization of crude oil biomarkers using comprehensive two-dimensional gas chromatography coupled to tandem mass spectrometry.

    PubMed

    Mogollón, Noroska Gabriela Salazar; Prata, Paloma Santana; Dos Reis, Jadson Zeni; Neto, Eugênio Vaz Dos Santos; Augusto, Fabio

    2016-09-01

    Oil samples from Recôncavo basin (NE Brazil), previously analyzed by traditional techniques such as gas chromatography coupled to tandem mass spectrometry, were evaluated using comprehensive two-dimensional gas chromatography coupled to quadrupole mass spectrometry and comprehensive two-dimensional gas chromatography coupled to tandem mass spectrometry along with simplified methods of samples preparation to evaluate the differences and advantages of these analytical techniques to better understand the development of the organic matter in this basin without altering the normal distribution of the compounds in the samples. As a result, the geochemical parameters calculated by comprehensive two-dimensional gas chromatography coupled to tandem mass spectrometry described better the origin, maturity, and biodegradation of both samples probably by increased selectivity, resolution, and sensitivity inherent of the multidimensional technique. Additionally, the detection of the compounds such as, the C(14α-) homo-26-nor-17α-hopane series, diamoretanes, nor-spergulanes, C19 -C26 A-nor-steranes and 4α-methylsteranes resolved and detected by comprehensive two-dimensional gas chromatography coupled to tandem mass spectrometry were key to classify and differentiate these lacustrine samples according to their maturity and deposition conditions.

  14. Determination of Free Fatty Acids and Triglycerides by Gas Chromatography Using Selective Esterification Reactions

    SciTech Connect

    Kail, Brian W; Link, Dirk D; Morreale, Bryan D

    2012-11-01

    A method for selectively determining both free fatty acids (FFA) and triacylglycerides (TAGs) in biological oils was investigated and optimized using gas chromatography after esterification of the target species to their corresponding fatty acid methyl esters (FAMEs). The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Complete conversion of both free acids and glycerides to corresponding FAMEs was found to require more rigorous reaction conditions involving heating to 120°C for up to 2 h. Method validation was provided using gas chromatography–flame ionization detection, gas chromatography–mass spectrometry, and liquid chromatography–mass spectrometry. The method improves on existing methods because it allows the total esterified lipid to be broken down by FAMEs contributed by FFA compared to FAMEs from both FFA and TAGs. Single and mixed-component solutions of pure fatty acids and triglycerides, as well as a sesame oil sample to simulate a complex biological oil, were used to optimize the methodologies. Key parameters that were investigated included: HCl-to-oil ratio, temperature and reaction time. Pure free fatty acids were found to esterify under reasonably mild conditions (10 min at 50°C with a 2.1:1 HCl to fatty acid ratio) with 97.6 ± 2.3% recovery as FAMEs, while triglycerides were largely unaffected under these reaction conditions. The optimized protocol demonstrated that it is possible to use esterification reactions to selectively determine the free acid content, total lipid content, and hence, glyceride content in biological oils. This protocol also allows gas chromatography analysis of FAMEs as a more ideal analyte than glyceride species in their native state.

  15. Pseudo-absolute quantitative analysis using gas chromatography - Vacuum ultraviolet spectroscopy - A tutorial.

    PubMed

    Bai, Ling; Smuts, Jonathan; Walsh, Phillip; Qiu, Changling; McNair, Harold M; Schug, Kevin A

    2017-02-08

    The vacuum ultraviolet detector (VUV) is a new non-destructive mass sensitive detector for gas chromatography that continuously and rapidly collects full wavelength range absorption between 120 and 240 nm. In addition to conventional methods of quantification (internal and external standard), gas chromatography - vacuum ultraviolet spectroscopy has the potential for pseudo-absolute quantification of analytes based on pre-recorded cross sections (well-defined absorptivity across the 120-240 nm wavelength range recorded by the detector) without the need for traditional calibration. The pseudo-absolute method was used in this research to experimentally evaluate the sources of sample loss and gain associated with sample introduction into a typical gas chromatograph. Standard samples of benzene and natural gas were used to assess precision and accuracy for the analysis of liquid and gaseous samples, respectively, based on the amount of analyte loaded on-column. Results indicate that injection volume, split ratio, and sampling times for splitless analysis can all contribute to inaccurate, yet precise sample introduction. For instance, an autosampler can very reproducibly inject a designated volume, but there are significant systematic errors (here, a consistently larger volume than that designated) in the actual volume introduced. The pseudo-absolute quantification capability of the vacuum ultraviolet detector provides a new means for carrying out system performance checks and potentially for solving challenging quantitative analytical problems. For practical purposes, an internal standardized approach to normalize systematic errors can be used to perform quantitative analysis with the pseudo-absolute method.

  16. In situ search for organics by gas chromatography analysis: new derivatization / thermochemolysis approach

    NASA Astrophysics Data System (ADS)

    Geffroy, Claude; Buch, Arnaud; David, Marc; Aissat, Lyes; El Mufleh, Amel; Papot, S.; Sternberg, Robert

    Many organic molecules are present in interstellar clouds and might be carried to the early Earth by comets and meteorites during the heavy bombardment phase in the first few hundred million years of the solar system. It has been suggested that extraterrestrial organic material may well represent an important part of the organic material available for the origin of life. Until samples, brought by future space missions, are available on Earth, in situ measurements are one of the way to get unaltered and non-contaminated samples for analysis. The analytical technique has to be robust, sensitive and non-specific due to the large scope of targets molecules. The only currently flight qualified technique of analysis of organic molecules in space is gas chromatography (Viking, Cassini-Huygens, SAM-MSL, COSAC-Rosetta). The main objective of this work is to present a new approach with multi step analysis using derivatisation and thermochemolysis reagents for a one pot in situ analysis of volatile and refractory organics in surface or sub-surface samples (Mars, comets).Indeed, no single technology enables to identify all organic compounds because naturally occurring molecules have different polarities, molecular weights, being extractible or recalcitrant, bonded trapped or adsorbed on minerals. Thus, we propose to wider the scope of chemical reagent already validated for in situ wet chemistry such as MTBSTFA (Rodier et al. 2001, 2002), DMF-DMA (Rodier et al. 2002), or TMAH (Rodier et al, 2005, Geffroy-Rodier et al; 2009) to analyze enantiomers of amino acids, carbohydrates and lipids in a one pot several steps sub system using a multi reagent and multi step approach. Thus using a new derivatizing agent, we successfully identified twenty one amino acids including twelve of the twenty proteinic amino acids without inhibiting following multi step thermochemolysis. *Geffroy-Rodier C, Grasset L, Sternberg R. Buch A. Amblès A. (2009) Thermochemolysis in search for organics in

  17. Comprehensive two-dimensional gas chromatography for characterizing mineral oils in foods and distinguishing them from synthetic hydrocarbons.

    PubMed

    Biedermann, Maurus; Grob, Koni

    2015-01-02

    Many foods are contaminated by hydrocarbons of mineral oil or synthetic origin. High performance liquid chromatography on-line coupled with gas chromatography and flame ionization detection (HPLC-GC-FID) is a powerful tool for the quantitative determination, but it would often be desirable to obtain more information about the type of hydrocarbons in order to identify the source of the contamination and specify pertinent legislation. Comprehensive two-dimensional gas chromatography (GC×GC) is shown to produce plots distinguishing mineral oil saturated hydrocarbons (MOSH) from polymer oligomeric saturated hydrocarbons (POSH) and characterizing the degree of raffination of a mineral oil. The first dimension separation occurred on a phenyl methyl polysiloxane, the second on a dimethyl polysiloxane. Mass spectrometry (MS) was used for identification, FID for quantitative determination. This shows the substantial advances in chromatography to characterize complex hydrocarbon mixtures even as contaminants in food.

  18. Determination of toxaphene enantiomers by comprehensive two-dimensional gas chromatography with electron-capture detection.

    PubMed

    Bordajandi, Luisa R; Ramos, Lourdes; González, María José

    2006-09-01

    Comprehensive two-dimensional gas chromatography with micro electron-capture detection (GC x GC-microECD) has been evaluated for the enantioseparation of five chiral toxaphenes typically found in real-life samples (Parlar 26, 32, 40, 44 and 50). From the two enantioselective beta-cyclodextrin-based columns evaluated as first dimension column, BGB-176SE and BGB-172, the latter provided the best results and was further combined with three non-enantioselective columns in the second dimension: HT-8, BPX-50 and Supelcowax-10. The combination BGB-172 x BPX-50 was finally selected because it provided a complete separation among all enantiomers. A satisfactory repeatability and reproducibility of the retention times in both the first and the second dimension were observed for all target compounds (RSDs below 0.8%, n = 4). Linear responses in the tested range of 10-200 pg/microl and limits of detection in the range of 2-6 pg/microl were obtained. The repeatability and reproducibility at a concentration of 100 pg/microl, evaluated as the RSDs calculated for the enantiomeric fraction (EF), was better than 11% (n = 4) in all instances. The feasibility of the method developed for real-life analyses was illustrated by the determination of the enantiomeric ratios and concentration levels of the test compounds in four commercial fish oil samples. These results were compared to those obtained by heart-cut multidimensional gas chromatography using the same enantioselective column.

  19. Detection for Non-Milk Fat in Dairy Product by Gas Chromatography

    PubMed Central

    2016-01-01

    The aim of this study was to evaluate the potential use of fatty acids, triacylglycerols, and cholesterol in the detection of adulterated milk fat. The fatty acid, triacylglycerol, and cholesterol profiles of the mixtures of milk and non-milk fat (adulteration ratios of 10%, 30%, 50%, 70%, and 90%) were analyzed by gas chromatography. The results showed that concentrations of the fatty acids with oleic acid (C18:1n9c) and linoleic acid (C18:2n6c), triglycerides with C52 and C54, and cholesterol detected are proportional to the adulteration ratios remarkably. Oleic acid (C18:1n9c), linoleic acid (C18:2n6c), C52, and C54 were lower in pure milk fat than in adulterated mixtures. In contrast, pure milk has a higher cholesterol concentration than all adulterated mixtures (adulteration concentration in the range 10-90%). Thus, we suggest that oleic acid (C18:1n9c), linoleic acid (C18:2n6c), C52, C54, and cholesterol are suitable indicators and can be used as biomarkers to rapidly detect adulterated milk fat by gas chromatography. This study is expected to provide basic data for adulteration and material usage. Moreover, this new approach can detect the presence of foreign oils and fats in the milk fat of cheese and can find application in related studies. PMID:27194929

  20. Determination of methomyl in the stomach contents of baited wildlife by gas chromatography-mass spectrometry.

    PubMed

    Buchweitz, John P; Bokhart, Mark; Johnson, Margaret; Lehner, Andreas

    2013-11-01

    The poisoning of wildlife with fly-bait containing the active ingredient methomyl is an intentional and illegal act in many jurisdictions. A case of 2 animals poisoned by methomyl through consumption of tainted bait at multiple stations is described. Although thermally and ultraviolet-labile, methomyl can be identified by gas chromatography-mass spectrometry and is detected in abundance in bait samples; however, it is not readily observed in tissues, owing to its rapid metabolism and elimination. The application of derivatizing functionalities, such as trimethylsilyl groups, stabilizes the methomyl-oxime metabolite to facilitate its detectability during exposure to the relatively harsh conditions of gas chromatography. This brief communication reports on the analytical detection of methomyl in baits and biological samples from poisoned wildlife. Essential to the case were the added determination of a fly-bait coactive ingredient, (Z)-9-tricosene, and identification of a chemical indicator, caffeine, to confirm both the type of pesticide product involved in the poisoning incident and the vehicle used to perpetrate its delivery.

  1. Preparation and characterization of alkyl methacrylate-based monolithic columns for capillary gas chromatography applications.

    PubMed

    Yusuf, Kareem; Aqel, Ahmad; A L Othman, Zeid; Badjah-Hadj-Ahmed, Ahmed Yacine

    2013-08-02

    Gas chromatography (GC) is considered the least common application of both polymer and silica-based monolithic columns. This study describes the fabrication of alkyl methacrylate monolithic materials for use as stationary phases in capillary gas chromatography. Following the deactivation of the capillary surface with 3-(trimethoxysilyl)propyl methacrylate (TMSM), the monoliths were formed by the co-polymerization of either hexyl methacrylate (HMA) or lauryl methacrylate (LMA) with different percentage of ethylene glycol dimethacrylate (EDMA) in presence of an initiator (azobisisobutyronitrile, AIBN) and a mixture of porogens include 1-propanol, 1,4-butanediol and water. The monoliths were prepared in 500mm length capillaries possessing inner diameters of 250μm. The efficiencies of the monolithic columns for low molecular weight compounds significantly improved as the percentage of crosslinker was increased, because of the greater proportion of pores less than 50nm. The columns containing lower percentages of crosslinker were able to rapidly separate a series of 8 alkane members in 0.7min, but the separation was less efficient for the light alkanes. Columns prepared with the lauryl methacrylate monomer yielded a different morphology for the monolith-interconnected channels. The channels were more branched, which increased the separation time, and unlike the other columns, allowed for temperature programming.

  2. Oxysterols in cosmetics-Determination by planar solid phase extraction and gas chromatography-mass spectrometry.

    PubMed

    Schrack, S; Hohl, C; Schwack, W

    2016-11-18

    Sterol oxidation products (SOPs) are linked to several toxicological effects. Therefore, investigation of potential dietary uptake sources particularly food of animal origin has been a key issue for these compounds. For the simultaneous determination of oxysterols from cholesterol, phytosterols, dihydrolanosterol and lanosterol in complex cosmetic matrices, planar solid phase extraction (pSPE) was applied as clean-up tool. SOPs were first separated from more non-polar and polar matrix constituents by normal phase thin-layer chromatography and then focussed into one target zone. Zone extraction was performed with the TLC-MS interface, followed by gas chromatography-mass spectrometry analysis. pSPE showed to be effective for cleaning up cosmetic samples as sample extracts were free of interferences, and gas chromatographic columns did not show any signs of overloading. Recoveries were between 86 and 113% with relative standard deviations of below 10% (n=6). Results of our market survey in 2016 showed that some cosmetics with ingredients of plant origin contained phytosterol oxidation products (POPs) in the low ppm range and therefore in line with levels reported for food. In lanolin containing products, total SOPs levels (cholesterol oxidation products (COPs), lanosterol oxidation products (LOPs), dihydrolanosterol oxidation products (DOPs)) being in the low percent range exceeded reported levels for food by several orders of magnitudes.

  3. Multi-residue determination of pesticides in vegetables by gas chromatography/ion trap mass spectrometry.

    PubMed

    Tao, C-J; Hu, J-Y; Li, J-Z; Zheng, S-S; Liu, W; Li, C-J

    2009-01-01

    To monitor possible contamination of edible vegetables by common pesticides, an analytical method using gas chromatography combined with ion trap spectrometry (GC-IT/MS) was developed to measure simultaneously up to 39 pesticide residues, belonging to organophosphors, organochlorines, pyrethroids or carbamates classes, left on four kinds of popular vegetables. The procedure entails addition of acetone, dichloromethane, and sodium chloride to a small amount of vegetable, then the mixture was shaken intensively and centrifuged for phase separation. An aliquot of the organic layer was cleanup using solid-phase extraction (SPE) cartridges filled with graphitized carbon black (GCB) in combination with acidic aluminum oxide. Gas chromatography with ion trap mass spectrometer was then used for qualitative and quantitative determination of the pesticides. The GCB combination with acidic aluminum oxide was found more suitable than florisil, aluminum oxide and silicon dioxide for sample cleanup with recoveries above 70% for most pesticides in removing the majority of co-extracted matrices. Variation coefficients of the repeatability typically smaller than 20% have been achieved for a wide range of the investigated pesticides. A set of critical instrument parameters for the GC-IT/MS Varian system in the MS mode was established. Based on optimization work conducted in this study, the 39 pesticides were separated successively with the limits of detection between 0.02 and 0.1 mg/kg.

  4. Chemical warfare agent detection in complex environments with comprehensive two-dimensional gas chromatography

    NASA Astrophysics Data System (ADS)

    Reichenbach, Stephen E.; Ni, Mingtian; Kottapalli, Visweswara; Visvanathan, Arvind; Ledford, Edward B., Jr.; Oostdijk, John; Trap, Henk C.

    2003-08-01

    Comprehensive two-dimensional gas chromatography (GCxGC) is an emerging technology for chemical separation that provides an order-of-magnitude increase in separation capacity over traditional gas chromatography. GCxGC separates chemical species with two capillary columns interfaced by two-stage thermal desorption. Because GCxGC is comprehensive and has high separation capacity, it can perform multiple traditional analytical methods with a single analysis. GCxGC has great potential for a wide variety of environmental sensing applications, including detection of chemical warfare agents (CWA) and other harmful chemicals. This paper demonstrates separation of nerve agents sarin and soman from a matrix of gasoline and diesel fuel. Using a combination of an initial column separating on the basis of boiling point and a second column separating on the basis of polarity, GCxGC clearly separates the nerve agents from the thousands of other chemicals in the sample. The GCxGC data is visualized, processed, and analyzed as a two-dimensional digital image using a software system for GCxGC image processing developed at the University of Nebraska - Lincoln.

  5. Rapid separation of beryllium and lanthanide derivatives by capillary gas chromatography

    SciTech Connect

    Harvey, Scott D.; Lucke, Richard B.; Douglas, Matt

    2012-09-04

    Previous studies describe derivatization of metal ions followed by analysis using gas chromatography, usually on packed columns. In many of these studies, stable and volatile derivatives were formed using fluorinated β-diketonate reagents. This paper extends previous work by investigating separations of the derivatives on small-diameter capillary gas chromatography columns and exploring on-fiber, solid-phase microextraction derivatization techniques for beryllium. The β-diketonate used for these studies was 1,1,1,2,2,6,6,7,7,7-decafluoro-3,5-heptanedione. Derivatization of lanthanides also required addition of a neutral donor, dibutyl sulfoxide, in addition to 1,1,1,2,2,6,6,7,7,7-decafluoro-3,5-heptanedione. Unoptimized separations on a 100-μm i.d. capillary column proved capable of rapid separations (within 15 min) of lanthanide derivatives that are adjacent to one another in the periodic table. Full-scan mass spectra were obtained from derivatives containing 5 ng of each lanthanide. Studies also developed a simple on-fiber solid-phase microextraction derivatization of beryllium. Beryllium could be analyzed in the presence of other alkali earth elements (Ba(II) and Sr(II)) without interference. Finally, extension of the general approach was demonstrated for several additional elements (i.e. Cu(II), Cr(III), and Ga(III)).

  6. Isotope dilution gas chromatography/mass spectrometry method for determination of pyrethroids in apple juice.

    PubMed

    Wong, Siu-kay; Yu, Kwok-chiu; Lam, Chi-ho

    2010-03-01

    This paper presents the development of a highly precise and accurate analytical method for the determination of three matrix-bound pyrethroids, namely, cypermethrin, permethrin, and bifenthrin, using an isotope dilution gas chromatography/mass spectrometry technique. Identification of the analytes was confirmed under selective ion monitoring mode by the presence of two dominant ion fragments within specific time windows and matching of relative ion intensities of the ions concerned in samples and calibration standards. Quantitation was based on the measurement of concentration ratios of the natural and isotope analogues in the sample and calibration blends. Intraday and interday repeatabilities of replicate analyses of the pyethroids in an apple juice sample were below 0.5%. The expanded relative uncertainty ranged from 3 to 6%, which was significantly lower than the range obtained using internal or external calibration methods. As a labeled analogue is not available for bifenthrin, bifenthrin was determined using labeled cis-permethrin as the internal standard. The results were counterchecked by a gas chromatography-electron capture detection technique using PCB 209 as the internal standard. The method developed was applied to a recent pilot study organized by CCQM and the results were consistent with those of other participants.

  7. Determination of amines used in the oil and gas industry (upstream section) by ion chromatography.

    PubMed

    Kadnar, R

    1999-07-30

    During production and purification of crude oil and natural gas several different amines are used as chemicals or operating materials, e.g. film forming long chain amines as corrosion inhibitors, steam volatile amines for pH correction and corrosion protection, alkanolamines as absorbents in sour gas treatment plants, etc. For analytical checks, e.g. determination of corrosion inhibitor concentration in produced media, classical chemical methods are used predominantly, because most of them can be performed in small field laboratories. Some amines, especially the small molecular aliphatic and heterocyclic amines can also be determined by ion chromatography. In our laboratory two types of separation columns (IonPac CS10 and CS12A) were available for ion chromatographic separation. The analysis of the amines in low-salt-containing water, soft water or steam condensate can be performed without problems. The presence of alkali and/or alkaline earth ions in the sample can lead to coelution with these ions, to poor peak resolution or enhanced analysis times, depending on the chromatographic conditions. This work shows some examples of ion chromatography applications for the determination of low-molecular-mass ethanolamines, morpholine and piperazine and discusses the possible interferences and troubles caused by alkali and alkaline earth ions in the matrix.

  8. Quantification of residual solvents in antibody drug conjugates using gas chromatography.

    PubMed

    Medley, Colin D; Kay, Jacob; Li, Yi; Gruenhagen, Jason; Yehl, Peter; Chetwyn, Nik P

    2014-11-19

    The detection and quantification of residual solvents present in clinical and commercial pharmaceutical products is necessary from both patient safety and regulatory perspectives. Head-space gas chromatography is routinely used for quantitation of residual solvents for small molecule APIs produced through synthetic processes; however residual solvent analysis is generally not needed for protein based pharmaceuticals produced through cultured cell lines where solvents are not introduced. In contrast, antibody drug conjugates and other protein conjugates where a drug or other molecule is covalently bound to a protein typically use solvents such as N,N-dimethylacetamide (DMA), N,N‑dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or propylene glycol (PG) to dissolve the hydrophobic small molecule drug for conjugation to the protein. The levels of the solvent remaining following the conjugation step are therefore important to patient safety as these parental drug products are introduced directly into the patients bloodstream. We have developed a rapid sample preparation followed by a gas chromatography separation for the detection and quantification of several solvents typically used in these conjugation reactions. This generic method has been validated and can be easily implemented for use in quality control testing for clinical or commercial bioconjugated products.

  9. Gas chromatography - optical fiber detector for assessment of fatty acids in urban soils.

    PubMed

    Silva, Lurdes; Cachada, Anabela; Pereira, Ruth; Freitas, Ana Cristina; Rocha-Santos, Teresa A P; Panteleitchouk, Teresa S L; Pereira, Maria E; Duarte, Armando Costa

    2011-07-15

    Fatty acids have been used as biomarkers of the microbial community composition of soils and they are usually separated and quantified by gas-chromatography coupled to a flame ionization detector (GC-FID). The aim of this study was to develop, validate and apply a methodology based on gas chromatography coupled to optical fiber detection (GC-OF) for screening five fatty acids used as indicators of fungal and bacterial communities in urban soils. The performance of the GC-OF methodology (optical fiber detector at 1,550 nm) was evaluated by comparison with the GC-FID methodology and it was found that they were comparable in terms of linear range, detection limit and analytical errors. Besides these similar analytical characteristics, the GC-OF is much cheaper than the GC-FID methodology. Different concentrations were determined for each fatty acid indicator which in turn varied significantly between the soil samples analyzed from Lisbon ornamental gardens. Additionally, the GC-OF showed a great potential as alternative for determination of eleven or more fatty acids in urban soils.

  10. Partial least squares analysis of rocket propulsion fuel data using diaphragm valve-based comprehensive two-dimensional gas chromatography coupled with flame ionization detection.

    PubMed

    Freye, Chris E; Fitz, Brian D; Billingsley, Matthew C; Synovec, Robert E

    2016-06-01

    The chemical composition and several physical properties of RP-1 fuels were studied using comprehensive two-dimensional (2D) gas chromatography (GC×GC) coupled with flame ionization detection (FID). A "reversed column" GC×GC configuration was implemented with a RTX-wax column on the first dimension ((1)D), and a RTX-1 as the second dimension ((2)D). Modulation was achieved using a high temperature diaphragm valve mounted directly in the oven. Using leave-one-out cross-validation (LOOCV), the summed GC×GC-FID signal of three compound-class selective 2D regions (alkanes, cycloalkanes, and aromatics) was regressed against previously measured ASTM derived values for these compound classes, yielding root mean square errors of cross validation (RMSECV) of 0.855, 0.734, and 0.530mass%, respectively. For comparison, using partial least squares (PLS) analysis with LOOCV, the GC×GC-FID signal of the entire 2D separations was regressed against the same ASTM values, yielding a linear trend for the three compound classes (alkanes, cycloalkanes, and aromatics), yielding RMSECV values of 1.52, 2.76, and 0.945 mass%, respectively. Additionally, a more detailed PLS analysis was undertaken of the compounds classes (n-alkanes, iso-alkanes, mono-, di-, and tri-cycloalkanes, and aromatics), and of physical properties previously determined by ASTM methods (such as net heat of combustion, hydrogen content, density, kinematic viscosity, sustained boiling temperature and vapor rise temperature). Results from these PLS studies using the relatively simple to use and inexpensive GC×GC-FID instrumental platform are compared to previously reported results using the GC×GC-TOFMS instrumental platform.

  11. Quantitative analysis of fragrance in selectable one dimensional or two dimensional gas chromatography-mass spectrometry with simultaneous detection of multiple detectors in single injection.

    PubMed

    Tan, Hui Peng; Wan, Tow Shi; Min, Christina Liew Shu; Osborne, Murray; Ng, Khim Hui

    2014-03-14

    A selectable one-dimensional ((1)D) or two-dimensional ((2)D) gas chromatography-mass spectrometry (GC-MS) system coupled with flame ionization detector (FID) and olfactory detection port (ODP) was employed in this study to analyze perfume oil and fragrance in shower gel. A split/splitless (SSL) injector and a programmable temperature vaporization (PTV) injector are connected via a 2-way splitter of capillary flow technology (CFT) in this selectable (1)D/(2)D GC-MS/FID/ODP system to facilitate liquid sample injections and thermal desorption (TD) for stir bar sorptive extraction (SBSE) technique, respectively. The dual-linked injectors set-up enable the use of two different injector ports (one at a time) in single sequence run without having to relocate the (1)D capillary column from one inlet to another. Target analytes were separated in (1)D GC-MS/FID/ODP and followed by further separation of co-elution mixture from (1)D in (2)D GC-MS/FID/ODP in single injection without any instrumental reconfiguration. A (1)D/(2)D quantitative analysis method was developed and validated for its repeatability - tR; calculated linear retention indices (LRI); response ratio in both MS and FID signal, limit of detection (LOD), limit of quantitation (LOQ), as well as linearity over a concentration range. The method was successfully applied in quantitative analysis of perfume solution at different concentration level (RSD≤0.01%, n=5) and shower gel spiked with perfume at different dosages (RSD≤0.04%, n=5) with good recovery (96-103% for SSL injection; 94-107% for stir bar sorptive extraction-thermal desorption (SBSE-TD).

  12. Parallel dual secondary column-dual detection: a further way of enhancing the informative potential of two-dimensional comprehensive gas chromatography.

    PubMed

    Nicolotti, Luca; Cordero, Chiara; Bressanello, Davide; Cagliero, Cecilia; Liberto, Erica; Magagna, Federico; Rubiolo, Patrizia; Sgorbini, Barbara; Bicchi, Carlo

    2014-09-19

    Comprehensive two-dimensional gas chromatography (GC×GC) coupled with Mass Spectrometry (MS) is one of today's most powerful analytical platforms for detailed analysis of medium-to-high complexity samples. The column set usually consists of a long, conventional-inner-diameter first dimension ((1)D) (typically 15-30m long, 0.32-0.25mm dc), and a short, narrow-bore second dimension ((2)D) column (typically 0.5-2m, 0.1mm dc) where separation is run in a few seconds. However, when thermal modulation is used, since the columns of a set are coupled in series, a flow mismatch occurs between the two dimensions, making it impossible to operate simultaneously at optimized flow conditions. Further, short narrow-bore capillaries can easily be overloaded, because of their lower loadability, limiting the effectiveness of (2)D separation. In this study, improved gas linear velocities in both chromatographic dimensions were achieved by coupling the (1)D column with two parallel (2)D columns, having identical inner diameter, stationary phase chemistry, and film thickness. In turn, these were connected to two detectors: a fast quadrupole Mass Spectrometer (MS) and a Flame Ionization Detector (FID). Different configurations were tested and performances compared to a conventional set-up; experimental results on two model mixtures (n-alkanes and fourteen medium-to-high polarity volatiles of interest in the flavor and fragrance field) and on the essential oil of Artemisia umbelliformis Lam., show the system provides consistent results, in terms of analyte identification (reliability of spectra and MS matching) and quantitation, also affording an internal cross-validation of quantitation accuracy.

  13. Determination of pentachlorophenol residue in meat and fish by gas chromatography-electron capture detection and gas chromatography-mass spectrometry with accelerated solvent extraction.

    PubMed

    Zhao, Dongmei

    2014-01-01

    A novel analytical method, using gas chromatography-electron capture detection (GC-ECD) and GC-mass spectrometry detection (MS), was developed for the qualitative and quantitative measurement of pentachlorophenol in meat and fish. The analyte was extracted by methanol-2% trichloroacetic acid (3/1, v/v) with accelerated solvent extraction (ASE). The eluted fraction was evaporated and derivatized with acetic anhydride-pyridine (1/1, v/v) for GC-ECD analysis and GC-MS confirmation. The parameters for extraction pressure, temperature and cycle of ASE, cleanup, derivatization and analysis procedure were optimized. The averaged decision limits and detection capability of the method were in the ranges of 0.25-0.41 and 0.49-1.01 µg/kg in the muscle and liver of swine and bovine and in the muscle of carp and finless eel, respectively. Spiked recoveries from levels of 0.5-2.0 µg/kg were found to be more than 71.1%, with relative standard deviation less than 14.7% in GC-ECD and GC-MS. This rapid and reliable method can be used for the characterization and quantification of residues of pentachlorophenol in animal and fish tissues.

  14. Recognition of chitin and proteins in invertebrate cuticles using analytical pyrolysis/gas chromatography and pyrolysis/gas chromatography/mass spectrometry.

    PubMed

    Stankiewicz, B A; Van Bergen, P F; Duncan, I J; Carter, J F; Briggs, D E; Evershed, R P

    1996-01-01

    Flash pyrolysis/gas chromatography (py/GC) and py/GC/mass spectrometry (MS) have been utilized to characterize the cuticles of invertebrates chemically. Pyrolysis products have been identified and assigned to specific cuticular components. Acetylpyridones, acetamidofuran, 3-acetamido-5-methylfuran and 3-acetamido-(2 and 4)-pyrones are proposed as characteristic pyrolysis markers for chitin. Pyrolysis products displaying ions of m/z 70, 154, 168, 194 are thought to derive from diketopiperazine structures and provide potential markers for proteins and peptides in which proline, alanine, valine, arginine and glycine are the dominant amino acids. These products, constituting specific pyrolysis markers for invertebrate cuticles, may reflect the amino acid composition of their constituent structural proteins. The source of the various pyrolysis products of proteins has been verified by pyrolysis of reference proteins, peptides and amino acid mixtures. The presence of additional pyrolysis products related directly to histidine and catechol moieties is consistent with the chemical structure and composition proposed for arthropod cuticles based on recent work utilizing solid state 13C and 15N nuclear magnetic resonance. This study constitutes the first comprehensive chemical characterization of the pyrolysis products of invertebrate cuticles and provides the basis for future investigations requiring qualitative screening for cross-linked chitin and proteins in modern and fossil cuticles and in materials, e.g. geopolymers, that may be derived from them.

  15. Identification of Aroma-active Compounds in Essential Oil from Uncaria Hook by Gas Chromatography- Mass Spectrometry and Gas Chromatography-Olfactometry.

    PubMed

    Iwasa, Megumi; Nakaya, Satoshi; Maki, Yusuke; Marumoto, Shinsuke; Usami, Atsushi; Miyazawa, Mitsuo

    2015-01-01

    The chemical composition of essential oil extracted from Uncaria Hook ("Chotoko" in Japanese), the branch with curved hook of the herbal medicine Uncaria rhynchophylla has been investigated by GC and GC-MS analyses. Eighty-four compounds, representing 90.8% of the total content was identified in oil obtained from Uncaria Hook. The main components i were (E)-cinnamaldehyde (13.4%), α-copaene (8.0%), methyl eugenol (6.8%), δ-cadinene (5.3%), and curcumene (3.6%). The important key aroma-active compounds in the oil were detected by gas chromatography-olfactometry (GC-O) and aroma extract dilution analysis (AEDA), using the flavor dilution (FD) factor to express the odor potency of each compounds. Furthermore, the odor activity value (OAV) has been used as a measure of the relative contribution of each compound to the aroma of the Uncaria Hook oil. The GC-O and AEDA results showed that α-copaene (FD = 4, OAV = 4376), (E)-linalool oxide (FD = 64, OAV = 9.1), and methyl eugenol (FD = 64, OAV = 29) contributed to the woody and spicy odor of Uncaria Hook oil, whereas furfural (FD = 8, OAV = 4808) contributed to its sweet odor. These results warrant further investigations of the application of essential oil from Uncaria Hook in the phytochemical and medicinal fields.

  16. Purge efficiency in the determination of trihalomethanes in water by purge-and-trap gas chromatography.

    PubMed

    Ruiz-Bevia, Francisco; Fernandez-Torres, Maria J; Blasco-Alemany, Maria P

    2009-01-26

    Purge-and-trap gas chromatography-mass spectrometry (PT-GC-MS) has become an accepted method for the analysis of trihalomethanes (THMs) in water. The purge-and-trap technique is based on an efficient transfer of volatile organic compounds from the liquid (contained in the purge chamber) to the gaseous phase by bubbling with an inert gas. The aim of this work was to study the purge system's efficiency by means of several consecutive purge cycles lasting 11 min each of the same liquid sample. The concentration range chosen of THMs was very wide [5-200 microg L(-1)]. The inert gas flow rate was 40 mL min(-1), and experiments were performed at temperatures of 25, 35 and 50 degrees C. Bromoform (CHBr(3)), the least volatile compound, needed 19 cycles to be purged quantitatively at a concentration of 200 microg L(-1) and only 7 cycles at 5 microg L(-1) for a 25 mL sample at 25 degrees C. Chloroform (CHCl(3)), the most volatile compound, required 4 cycles to be fully extracted at 200 microg L(-1) and 2 at 5 microg L(-1). Finally, Novak's theoretical model, based on the distribution constant between gas and liquid phases, was used to correlate the THMs purging extraction data.

  17. Two-dimensional retention indices improve component identification in comprehensive two-dimensional gas chromatography of saffron.

    PubMed

    Jiang, Ming; Kulsing, Chadin; Nolvachai, Yada; Marriott, Philip J

    2015-06-02

    Comprehensive two-dimensional gas chromatography hyphenated with accurate mass time-of-flight mass spectrometry (GC × GC-accTOFMS) was applied for improved analytical accuracy of saffron analysis, by using retention indices in the two-dimensional separation. This constitutes 3 dimensions of identification. In addition to accTOFMS specificity, and first dimension retention indices ((1)I), a simple method involving direct multiple injections with stepwise isothermal temperature programming is described for construction of isovolatility curves for reference alkane series in GC × GC. This gives access to calculated second dimension retention indices ((2)I). Reliability of the calculated (2)I was evaluated by using a Grob test mixture, and saturated alkanes, revealing good correlation between previously reported I values from the literature, with R(2) correlation being 0.9997. This essentially recognizes the retention property of peaks in the GC × GC 2D space as being reducible to a retention index in each dimension, which should be a valuable tool supporting identification. The benefit of (2)I data, in supplementing (1)I and MS library matching, was clearly demonstrated by the progressive reduction of the number of possible compound matches for peaks observed in saffron. 114 analytes were assessed according to (1)I and (2)I values within ±20 index unit of reference values, and by MS spectrum matching above a match statistic of 750 (including mass accuracy of the molecular ion <20 ppm) and their possible identities derived. The described method provides a new avenue to utilize the full capability of the two-dimensional separation (GC × GC), in combination with MS library matching in complex sample analysis, to provide improved component identification.

  18. High-performance, static-coated silicon microfabricated columns for gas chromatography.

    PubMed

    Reidy, Shaelah; Lambertus, Gordon; Reece, Jennifer; Sacks, Richard

    2006-04-15

    A procedure is described for the preparation of high-performance etched silicon columns for gas chromatography. Rectangular channels, 150 mum wide by 240 mum deep are fabricated in silicon substrates by gas-phase reactive ion etching. A 0.1-0.2-mum-thick film of dimethyl polysiloxane stationary phase is deposited on the channel walls by filling the channel with a dilute solution in 1:1 n-pentane and dichloromethane and pumping away the solvent. A thermally activated cross-linking agent is used for in situ cross-linking. A 3-m-long microfabricated column generated approximately 12 500 theoretical plates at optimal operating conditions using air as carrier gas. A kinetic model for the efficiency of rectangular cross-section columns is used to evaluate column performance. Results indicate an additional source of gas-phase dispersion beyond longitudinal diffusion and nonequilibrium effects, probably resulting from numerous turns in the gas flow path through the channel. The columns are thermally stable to at least 180 degrees C using air carrier gas. Temperature programming is demonstrated for the boiling point range from n-C5 to n-C12. A 3.0-m-long column heated at 10 degrees C/min obtains a peak capacity of over 100 peaks with a resolution of 1.18 and a separation time of approximately 500 s. With a 0.25-m-long column heated at 30 degrees C/min, a peak capacity of 28 peaks is obtained with a separation time of 150 s. Applications are shown for the analysis of air-phase petroleum hydrocarbons and the high-speed analysis of chemical warfare agent and explosive markers.

  19. Aroma characterization of chinese rice wine by gas chromatography-olfactometry, chemical quantitative analysis, and aroma reconstitution.

    PubMed

    Chen, Shuang; Xu, Yan; Qian, Michael C

    2013-11-27

    The aroma profile of Chinese rice wine was investigated in this study. The volatile compounds in a traditional Chinese rice wine were extracted using Lichrolut EN and further separated by silica gel normal phase chromatography. Seventy-three aroma-active compounds were identified by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). In addition to acids, esters, and alcohols, benzaldehyde, vanillin, geosmin, and γ-nonalactone were identified to be potentially important to Chinse rice wine. The concentration of these aroma-active compounds in the Chinese rice wine was further quantitated by combination of four different methods, including headsapce-gas chromatography, solid phase microextraction-gas chromatography (SPME)-GC-MS, solid-phase extraction-GC-MS, and SPME-GC-pulsed flame photometric detection (PFPD). Quantitative results showed that 34 aroma compounds were at concentrations higher than their corresponding odor thresholds. On the basis of the odor activity values (OAVs), vanillin, dimethyl trisulfide, β-phenylethyl alcohol, guaiacol, geosmin, and benzaldehyde could be responsible for the unique aroma of Chinese rice wine. An aroma reconstitution model prepared by mixing 34 aroma compounds with OAVs > 1 in an odorless Chinese rice wine matrix showed a good similarity to the aroma of the original Chinese rice wine.

  20. Absorbents as packing materials in on-line coupling of reversed phase liquid chromatography and gas chromatography via a programmed temperature vaporizer.

    PubMed

    Flores, Gema; Ruiz Del Castillo, Maria Luisa; Herraiz, Marta

    2007-06-15

    A method based on the use of absorbents as packing materials in the interface of the direct coupling between reversed phase liquid chromatography and gas chromatography (RPLC-GC) is proposed. To that end, a comparative study on different adsorbents and absorbents was carried out. Specifically, Tenax TA and Gaschrom were used as adsorbents while polydimethylsiloxane and poly(50% phenyl:50% methylsiloxane) were the absorbents tested. Some experimental variables involved in the solvent elimination were separately optimised for adsorbent and absorbent materials. Relative standard deviations (RSD) lower than 10% were achieved in all cases but the use of absorbents showed interesting advantages with respect to adsorbents, namely a simpler performance of the experimental work, which facilitates the sample preparation step and the subsequent gas chromatographic analysis to be performed.

  1. Analysis of the venom of the Sydney funnel-web spider, Atrax robustus using gas chromatography mass spectrometry.

    PubMed

    Duffield, P H; Duffield, A M; Carroll, P R; Morgans, D

    1979-03-01

    Thirteen compounds have been identified using gas chromatography mass spectrometry in the venom of the Sydney funnel-web spider, Atrax robustus. The compounds were identified as their trimethylsilyl or pentafluoropropionate derivatives and were citric acid, lactic acid, phosphoric acid, glycerol, urea, glucose, gamma-aminobutyric acid, glycine, spermidine, spermine, tyramine and octopamine. Female venom contained trace quantities of 5-methyoxytryptamine which was not detected in male venom. Quantitative determination of tyramine and octopamine was achieved using chemical ionization (CH4) gas chromatography mass spectrometry and deuterated internal standards.

  2. Identification of Gibberellins in Norway Spruce (Picea abies [L.] Karst.) by Combined Gas Chromatography-Mass Spectrometry

    PubMed Central

    Odén, Per Christer; Schwenen, Ludger; Graebe, Jan E.

    1987-01-01

    Gibberellins A1 (GA1), A3 and A9 were identified from extracts of shoots of 6-month old Norway spruce (Picea abies) seedlings by the use of sequential reverse and normal phase high performance liquid chromatography (HPLC), bioassay, radioimmunoassay (RIA) and combined gas chromatography-mass spectrometry (GC-MS). The bioassay and RIA were used after fractionation by HPLC to detect the GA-containing fractions, which were then examined by GC-MS. The GAs identified are considered to be endogenous. PMID:16665471

  3. Metabolism of trimipramine in vitro by human CYP2D6 isozyme.

    PubMed

    Bolaji, O O; Coutts, R T; Baker, G B

    1993-10-01

    In vitro metabolism of the tricyclic antidepressant trimipramine using a commercial preparation of human CYP2D6 isozyme expressed in a human cell line is described. 2-Hydroxytrimipramine and a previously unreported metabolite, 2,10- or 2,11-dihydroxytrimipramine were isolated. Their structures were determined by gas chromatography/mass spectroscopy of underivatized and derivatized extracts. Acetylation of the new metabolite resulted in dehydration at C10 to give 10,11-dehydro-2-acetoxytrimipramine. No N-dealkylation of trimipramine was observed. Prior administration of quinidine produced a large reduction in the metabolic oxidation of trimipramine with CYP2D6 while prior administration of quinine had no effect. The use of this CYP2D6 isozyme preparation in vitro is of value in the identification of possible in vivo substrates for the human CYP2D6 isozyme.

  4. On-column micro gas chromatography detection with capillary-based optical ring resonators.

    PubMed

    Shopova, Siyka I; White, Ian M; Sun, Yuze; Zhu, Hongying; Fan, Xudong; Frye-Mason, Greg; Thompson, Aaron; Ja, Shiou-jyh

    2008-03-15

    We developed a novel on-column micro gas chromatography (microGC) detector using capillary based optical ring resonators (CBORRs). The CBORR is a thin-walled fused silica capillary with an inner diameter ranging from a few tens to a few hundreds of micrometers. The interior surface of the CBORR is coated with a layer of stationary phase for gas separation. The circular cross section of the CBORR forms a ring resonator and supports whispering gallery modes (WGMs) that circulate along the ring resonator circumference hundreds of times. The evanescent field extends into the core and is sensitive to the refractive index change induced by the interaction between the gas sample and the stationary phase. The WGM can be excited and monitored at any location along the CBORR by placing a tapered optical fiber against the CBORR, thus enabling on-column real-time detection. Rapid separation of both polar and nonpolar samples was demonstrated with subsecond detection speed. Theoretical work was also established to explain the CBORR detection mechanism. While low-nanogram detection limits are observed in these preliminary tests, many methods for improvements are under investigation. The CBORR is directly compatible with traditional capillary GC columns without any dead volumes. Therefore, the CBORR-based muGC is a very promising technology platform for rapid, sensitive, and portable analytical devices.

  5. Determination of residual epichlorohydrin in sevelamer hydrochloride by static headspace gas chromatography with flame ionization detection.

    PubMed

    Karthikeyan, Kaliaperumal; Arularasu, Govindasamy T; Devaraj, Perumalsamy; Pillai, Karnam Chandrasekara

    2010-01-01

    A sensitive static headspace gas chromatographic method was developed and validated for the determination of residual epichlorohydrin (ECH) in sevelamer hydrochloride (SVH) drug substance. This method utilized a Phenomenex Zebron ZB-WAX GC column, helium as carrier gas with flame ionization detection. The critical experimental parameters, such as, headspace vial incubation time and incubation temperature were studied and optimized. The method was validated as per United States Pharmacopoeia (USP) and International Conference on Harmonization (ICH) guidelines in terms of detection limit (DL), quantitation limit (QL), linearity, precision, accuracy, specificity and robustness. A linear range from 0.30 to 10 Îg/mL was obtained with the coefficient of determination (r(2)) 0.999. The DL and QL of ECH were 0.09 Îg/mL and 0.30 Îg/mL, respectively. The recovery obtained for ECH was between 91.7 and 96.6%. Also, the specificity of the method was proved through gas chromatography mass spectrometry (GC-MS). This method was applied successfully to determine the content of residual ECH in SVH bulk drug.

  6. Aircraft measurements of nitrogen dioxide and peroxyacyl nitrates using luminol chemiluminescence with fast capillary gas chromatography

    SciTech Connect

    Gaffney, J.S.; Marley, N.A.; Drayton, P.J.

    1997-09-01

    Peroxyacyl nitrates (PANs) and nitrogen dioxide (NO{sub 2}) are important trace gas species associated with photochemical air pollution. The PANs are in thermal equilibrium with the peroxyacetyl radical and NO{sub 2}. Because PANs are trapped peroxy radicals, they are an important indicator species of the photochemical age of an air parcel, as well as being a means of long-range transporting of NO{sub 2}, leading to the formation of regional ozone and other oxidants. Typically, PANs are measured by using a gas chromatograph with electron-capture detection (ECD). Once automated, this method has been shown to be reliable and quite sensitive, allowing the levels of PANs to be measured at low parts per trillion in the troposphere. Unfortunately, a number of other atmospheric gases also have strong ECD signals or act as inferences and limit the speed in which the analysis can be completed. Currently, the shortest analysis time for PAN is approx. 5 minutes with ECD. The authors recent examined the luminol detection of NO{sub 2} and PANs using gas capillary chromatography for rapid monitoring of these important trace gases. Analysis of the PANs (PAN, PPN, and PBN) and NO{sub 2} in one minute has been demonstrated in laboratory studies by using this approach. Reported here are modifications of this instrument for aircraft operation and preliminary results from test flights taken near Pasco, Washington in August of 1997.

  7. Resolution of diacylglycerol moieties of natural glycerophospholipids by gas-liquid chromatography on polar capillary columns.

    PubMed

    Myher, J J; Kuksis, A

    1982-06-01

    A rapid and practical method has been developed for the gas-liquid chromatographic determination of the sn-1,2-diacylglycerol moieties of natural glycerophospholipids using polar wall-coated open tubular columns. The method gives complete resolution and quantitative estimates for all species according to molecular weight and degree of unsaturation, including stearoyl docosahexaenoylglycerol and related polyunsaturates. For this purpose the sn-1,2-diacylglycerols are obtained from the glycerophospholipids by hydrolysis with phospholipase C and are converted into the trimethylsilyl or tertiary-butyldimethylsilyl ethers. The silyl ethers are separated by gas-liquid chromatography on the capillary glass columns coated with a polar cyanopropylsiloxane polymer, in the temperature range 175-250 degrees C, using hydrogen as the carrier gas. Practical applications of the method are illustrated by analyses of the sn-1,2-diacylglycerol moieties of the phosphatidylcholines of soybean phosphatides, egg yolk, and rat liver. The method of analysis is applicable to other classes of glycerophospholipids and the total time requirements for the analysis of any one phospholipid class are comparable to those for a fatty acid analysis.

  8. GLOBAL PEAK ALIGNMENT FOR COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY MASS SPECTROMETRY USING POINT MATCHING ALGORITHMS

    PubMed Central

    Deng, Beichuan; Kim, Seongho; Li, Hengguang; Heath, Elisabeth; Zhang, Xiang

    2016-01-01

    Comprehensive two-dimensional gas chromatography coupled with mass spectrometry (GC×GC-MS) has been used to analyze multiple samples in a metabolomics study. However, due to some uncontrollable experimental conditions, such as the differences in temperature or pressure, matrix effects on samples, and stationary phase degradation, there is always a shift of retention times in the two GC columns between samples. In order to correct the retention time shifts in GC×GC-MS, the peak alignment is a crucial data analysis step to recognize the peaks generated by the same metabolite in different samples. Two approaches have been developed for GC×GC-MS data alignment: profile alignment and peak matching alignment. However, these existing alignment methods are all based on a local alignment, resulting that a peak may not be correctly aligned in a dense chromatographic region where many peaks are present in a small region. False alignment will result in false discovery in the downstream statistical analysis. We, therefore, develop a global comparison based peak alignment method using point matching algorithm (PMA-PA) for both homogeneous and heterogeneous data. The developed algorithm PMA-PA first extracts feature points (peaks) in the chromatography and then searches globally the matching peaks in the consecutive chromatography by adopting the projection of rigid and non-rigid transformation. PMA-PA is further applied to two real experimental data sets, showing that PMA-PA is a promising peak alignment algorithm for both homogenous and heterogeneous data in terms of F1 score, although it uses only peak location information. PMID:27650662

  9. Comparison of gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry with electron ionization for determination of N-nitrosamines in environmental water.

    PubMed

    Chen, Wenwen; Li, Xiaoshui; Huang, Huanfang; Zhu, Xuetao; Jiang, Xiaoyu; Zhang, Yuan; Cen, Kuang; Zhao, Lunshan; Liu, Xiuli; Qi, Shihua

    2017-02-01

    N-nitrosamines are trace organic contaminants of environmental concern when present in groundwater and river water due to their potent carcinogenicity. Therefore, N-nitrosamine analysis is increasingly in demand. Gas chromatography-mass spectrometry (GC-MS) and GC-tandem mass spectrometry (GC-MS/MS), both with electron ionization (EI), were compared for analysis of nine N-nitrosamines extracted from environmental water matrices. A total of 20 fishpond water, river water, and groundwater samples from Sihui and Shunde, China were collected for a survey of N-nitrosamine concentrations in real water samples. Various solid-phase extraction (SPE) conditions and GC conditions were first examined for the pre-concentration and separation steps. The analysis of N-nitrosamines in environmental waters demonstrated that their quantification with GC-MS poses a challenge due to the occurrence of co-eluting interferences. Conversely, the use of GC-MS/MS increased selectivity because of the fragmentation generated from precursor ions in the 'multiple reaction monitoring' (MRM) mode, which is expected to extract target analytes from the environmental water matrix. Thus, the high performance of GC-MS/MS with EI was used to quantify nine N-nitrosamines in environmental waters with detection limits of 1.1-3.1 ng L(-1). N-nitrosodimethylamine (NDMA) concentrations were in the range of N.D. to 258 ng L(-1). Furthermore, other N-nitrosamines, except N-nitrosomethylethylamine (NMEA), N-nitroso-di-n-propylamine (NDPA) and N-nitrosopiperidine (NPIP), were also detected. Our findings suggest that GC-MS/MS with EI would be widely applicable in identifying N-nitrosamines in environmental waters and can be used for routine monitoring of these chemicals.

  10. Simultaneous analysis of polychlorinated biphenyls and organochlorine pesticides in seawater samples by membrane-assisted solvent extraction combined with gas chromatography-electron capture detector and gas chromatography-tandem mass spectrometry.

    PubMed

    Shi, Xizhi; Tang, Zigang; Sun, Aili; Zhou, Lei; Zhao, Jian; Li, Dexiang; Chen, Jiong; Pan, Daodong

    2014-12-01

    A highly efficient and environment-friendly membrane-assisted solvent extraction system combined with gas chromatography-electron capture detector was applied in the simultaneous determination of 17 polychlorinated biphenyls and organochlorine pesticides in seawater samples. Variables affecting extraction efficiency, including extraction solvent used, stirring rate, extraction time, and temperature, were optimized extensively. Under optimal extraction conditions, recoveries between 76.9% and 104.6% in seawater samples were achieved, and relative standard deviation values below 10% were obtained. The limit of detection (signal-to-noise ratio=3) and limit of quantification (signal-to-noise ratio=10) of 17 polychlorinated biphenyls and organochlorine pesticides in seawater ranged from 0.14ngL(-1) to 0.36ngL(-1) and 0.46ngL(-1) to 1.19ngL(-1), respectively. Matrix effects on extraction efficiency were evaluated by comparing with the results obtained using tap water. The extraction effect of developed membrane-assisted solvent extraction method was further demonstrated by gas chromatography-tandem mass spectrometry which can provide structural information of the analytes for more accurate identification, and results identical to those produced by gas chromatography-electron capture detector were obtained. These findings demonstrate the applicability of the developed membrane-assisted solvent extraction determination method for coupling to gas chromatography-electron capture detector or tandem mass spectrometry for determining polychlorinated biphenyls and organochlorine pesticides in seawater samples.

  11. Issues pertaining to the analysis of buprenorphine and its metabolites by gas chromatography-mass spectrometry.

    PubMed

    Wang, Yu-Shan; Lin, Dong-Liang; Yang, Shu-Ching; Wu, Meng-Yan; Liu, Ray H; Su, Lien-Wen; Cheng, Pai-Sheng; Liu, Chiareiy; Fuh, Ming-Ren

    2010-03-05

    "Substitution therapy" and the use of buprenorphine (B) as an agent for treating heroin addiction continue to gain acceptance and have recently been implemented in Taiwan. Mature and widely utilized gas chromatography-mass spectrometry (GC-MS) technology can complement the low cost and highly sensitive immunoassay (IA) approach to facilitate the implementation of analytical tasks supporting compliance monitoring and pharmacokinetic/pharmacogenetic studies. Issues critical to GC-MS analysis of B and norbuprenorphine (NB) (free and as glucuronides), including extraction, hydrolysis, derivatization, and quantitation approaches were studied, followed by comparing the resulting data against those derived from IA and two types of liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Commercial solid-phase extraction devices, highly effective for recovering all metabolites, may not be suitable for the analysis of free B and NB; acetyl-derivatization products exhibit the most favorable chromatographic, ion intensity, and cross-contribution characteristics for GC-MS analysis. Evaluation of IA, GC-MS, and LC-MS/MS data obtained in three laboratories has proven the 2-aliquot GC-MS protocol effective for the determination of free B and NB and their glucuronides.

  12. Measurement of F2- isoprostanes and isofurans using gas chromatography-mass spectrometry.

    PubMed

    Milne, Ginger L; Gao, Benlian; Terry, Erin S; Zackert, William E; Sanchez, Stephanie C

    2013-06-01

    F2-Isoprostanes (IsoPs) are isomers of prostaglandin F2α formed from the nonenzymatic free radical-catalyzed peroxidation of arachidonic acid. Since discovery of these molecules by Morrow and Roberts in 1990, F2-IsoPs have been shown to be excellent biomarkers as well as potent mediators of oxidative stress in vivo in humans. Isofurans (IsoFs) are also oxidation products generated from the nonenzymatic oxidation of arachidonic acid. IsoFs are preferentially formed instead of F2-IsoPs in settings of increased oxygen tension. The protocol presented herein is the current methodology that our laboratory uses to quantify F2-IsoPs and IsoFs in biological tissues and fluids using gas chromatography/mass spectrometry (GC/MS). A variety of analytical procedures to measure F2-IsoPs, including other GC/MS methods and liquid chromatography/MS and immunological approaches, are reported in the literature. This method provides a very low limit of quantitation and is suitable for analysis of both F2-IsoPs and IsoFs from a variety of biological sources including urine, plasma, tissues, cerebral spinal fluid, exhaled breath condensate, and amniotic fluid, among others.

  13. High resolution capillary column development for selective separations in gas chromatography

    SciTech Connect

    Przybyciel, M.

    1985-01-01

    A review of techniques for the preparation of high resolution capillary columns for gas chromatography is presented. Surface roughing, surface deactivation, stationary phase coating, and stationary phase crosslinking are discussed. Criteria for the selection of GC stationary phases and procedures for column evaluation are presented. A method is proposed for the isolation and determination of crude oil contamination in tropical plants and sediments. The method uses Florisil (TM) chromatography for the simultaneous clean-up and fractionation of aliphatic and aromatic hydrocarbons. Crosslinked SE-54 fused silica capillary columns prepared in our laboratory were employed for all GC separations. Mass spectrometry was used to help locate and identify specific oil components despite the intense background of the chromatogram. Crude oil components were identified in extracts of mangrove plant samples collected from the Peck Slip oil spill site at Media Munda, Puerto Rico. Crude oil components were also identified in sediment samples from controlled oil spill of Prudhoe Bay oil at Laguna de Chiriqui, Panama.

  14. Pyrolysis-gas chromatography/mass spectrometry of a coal extract and its fractions separated by planar chromatography: correlation of structural features with molecular mass

    PubMed

    Islas; Suelves; Carter; Herod; Kandiyoti

    2000-01-01

    The structural characterisation of a coal liquefaction extract and its three fractions separated by planar chromatography has been described. Size exclusion chromatography showed the molecular mass distributions to become progressively larger with decreasing mobility on the plate. UV-fluorescence spectroscopy of the fractions indicated parallel increases in the sizes of polynuclear aromatic ring systems. Analysis by probe-mass spectrometry of the 'whole' coal extract showed the expected array of small polynuclear aromatic groups extending to m/z 450. The probe mass spectra of the lightest fraction ('mobile in pyridine and acetonitrile') showed similar features, except for effects due to vacuum drying to remove solvent. In sharp contrast, the two heaviest fractions ('mobile in pyridine and immobile in acetonitrile' and 'immobile in pyridine') showed no significant ions other than those from residual NMP solvent (m/z 98 and 99). Pyrolysis-gas chromatography/mass spectrometry of these two heaviest fractions showed only traces of aromatic compounds or fragments. The aromatic pyrolysis products of these fractions were too large and involatile to pass through the GC column. The major components observed in the pyrolysis-gas chromatography/mass spectrometry of the two heavy fractions were alkanes and alkenes, ranging between C10-C25. Since none of the samples contained free alkanes, alkenes or cycloalkanes before pyrolysis, they were generated during the pyrolysis step. The shifts of UV-fluorescence spectral intensity to shorter wavelengths with decreasing size indicated by size exclusion chromatography (SEC) provide direct evidence of differences in structure with changing molecular mass. This evidence strongly suggests that species identified as being of large molecular mass in this extract sample are not composed of molecular aggregates. It remains difficult to establish whether and when it would be legitimate to invoke molecular aggregates to explain the large

  15. Accurate measurements of thermodynamic properties of solutes in ionic liquids using inverse gas chromatography.

    PubMed

    Mutelet, Fabrice; Jaubert, Jean-Noël

    2006-01-13

    Activity coefficients at infinite dilution of 29 organic compounds in two room temperature ionic liquids were determined using inverse gas chromatography. The measurements were carried out at different temperatures between 323.15 and 343.15K. To establish the influence of concurrent retention mechanisms on the accuracy of activity coefficients at infinite dilution for 1-butyl-3-methylimidazolium octyl sulfate and 1-ethyl-3-methylimidazolium tosylate, phase loading studies of the net retention volume per gram of packing as a function of the percent phase loading were used. It is shown that most of the solutes are retained largely by partition with a small contribution from adsorption on 1-butyl-3-methylimidazolium octyl sulfate and that the n-alkanes are retained predominantly by interfacial adsorption on 1-ethyl-3-methylimidazolium tosylate.

  16. Enthalpy of adsorption for hydrocarbons on concrete by inverse gas chromatography.

    PubMed

    Widegren, Jason A; Bruno, Thomas J

    2011-07-15

    Enthalpies of adsorption, ΔH(a), are reported for several light hydrocarbons on normal construction concrete. ΔH(a), which are a measure of the adhesion strength of a molecule on a surface, were determined by gas-solid chromatography with a packed column containing 60-80 mesh concrete particles. With this approach, the specific retention volume for a compound is measured as a function of temperature, and these data are used to calculate ΔH(a). For the hydrocarbons studied, we found that ΔH(a) was relatively large for unsaturated hydrocarbons. These are the first determinations of ΔH(a) of hydrocarbons on construction concrete, but useful comparisons with other ionic solids such as clays can be made.

  17. Rapid method for determination of carbonyl groups in lignin compounds by headspace gas chromatography.

    PubMed

    Li, Jing; Hu, Hui-Chao; Chai, Xin-Sheng

    2015-07-24

    The paper reports on a novel method for rapid determination of carbonyl in lignins by headspace gas chromatography (HS-GC). The method involves the quantitative carbonyl reduction for aldehydes in 2min at room temperature or for acetones in 30min at 80°C by sodium borohydride solution in a closed headspace sample vial. After the reaction, the solution was acidified by injecting sulfuric acid solution and the hydrogen released to the headspace was determined by GC using thermal-conductivity detector. The results showed that with the addition of SiO2 powder, the reduction reaction of carbonyl groups can be greatly facilitated. The method has a good measurement precision (RSD<7.74%) and accuracy (relative error <10% compared with a reference method) in the carbonyl quantification. It is suitable to be used for rapid determination of carbonyl content in lignin and related materials.

  18. Gas chromatography of safranal as preferable method for the commercial grading of saffron (Crocus sativus L.).

    PubMed

    Bononi, Monica; Milella, Paola; Tateo, Fernando

    2015-06-01

    We present a new extraction protocol, using ethyl alcohol as a solvent, to evaluate safranal by gas chromatography (GC). A linear response was obtained with R(2)=0.995 and a reproducibility standard deviation of 4.7-6.0%. The limit of detection and limit of quantitation were 0.05 and 0.25gkg(-1), respectively. The GC data for several samples of powdered saffron from different origins were compared to specific absorbance values measured according to the ISO Normative 3632-1:2011 method. The aroma strength of saffron samples quantitated by GC and the specific absorbance values of safranal by the UV method did not correlate. Quantitative evaluation of safranal by GC appears to be more specific and useful for commercial comparisons of saffron quality.

  19. Verification of chemical composition of commercially available propolis extracts by gas chromatography-mass spectrometry analysis.

    PubMed

    Czyżewska, Urszula; Konończuk, Joanna; Teul, Joanna; Drągowski, Paweł; Pawlak-Morka, Renata; Surażyński, Arkadiusz; Miltyk, Wojciech

    2015-05-01

    Propolis is a resin that is collected by honeybees from various plant sources. Due to its pharmacological properties, it is used in commercial production of nutritional supplements in pharmaceutical industry. In this study, gas chromatography-mass spectrometry was applied for quality control analysis of the three commercial specimens containing aqueous-alcoholic extracts of bee propolis. More than 230 constituents were detected in analyzed products, including flavonoids, chalcones, cinnamic acids and their esters, phenylpropenoid glycerides, and phenylpropenoid sesquiterpenoids. An allergenic benzyl cinnamate ester was also identified in all tested samples. This analytical method allows to evaluate biological activity and potential allergenic components of bee glue simultaneously. Studies on chemical composition of propolis samples may provide new approach to quality and safety control analysis in production of propolis supplementary specimens.

  20. Gas chromatography/mass spectrometry for the determination of nitrosamines in red wine.

    PubMed

    Lona-Ramirez, Fernando J; Gonzalez-Alatorre, Guillermo; Rico-Ramírez, Vicente; Perez-Perez, Ma Cristina I; Castrejón-González, Edgar O

    2016-04-01

    N-nitrosamines (NAms) are highly active carcinogens that have been detected in food and beverages. Currently certain studies report their presence in red wine, while others fail to detect their presence. In this study the head space solid phase micro-extraction technique coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) was applied to quantify four NAms in different types of red wine. The technique was found to be a simple, precise, fast and environmentally friendly alternative for the quantification of volatile NAms. A factorial analysis was carried out to evaluate the influence of the parameters on the HS-SPME technique. This is the first study that such analysis has been reported and where NAms in red wine have been quantified using HS-SPME-GC-MS. The method was validated by calculating the linearity, limit of detection and quantification. Two of the four NAms analyzed were found to be present in red wine samples.

  1. Preparative monohydroxyflavanone syntheses and a protocol for gas chromatography-mass spectrometry analysis of monohydroxyflavanones.

    PubMed

    Kagawa, Hitoshi; Shigematsu, Asako; Ohta, Shigeru; Harigaya, Yoshihiro

    2005-05-01

    We describe a facile efficient, and preparative approach for monohydroxyflavanone syntheses. Using this protocol, a hydroxyl is regio-selectively introduced at one carbon of a flavanone A- or B-ring per synthesis. The seven possible isomers were each synthesized from the corresponding monomethoxymethoxylated 2'-hydroxychalcones in acidic solution. These monohydroxyflavanones were characterized using a gas chromatography-mass spectrometry (GC-MS) system that incorporated a DB-5 capillary column. Ours is the first report of a preparative synthetic method during which a single hydroxyl can be selectively added to a flavanone A- or B-ring at any position. We are also the first to develop a procedure that separates the seven isomers by GC and characterizes the mass spectra of the isomers. Both the synthetic method and the GC-MS conditions may become important tools during future flavanone metabolism and oxidation studies.

  2. Determination of ibogaine in plasma by gas chromatography--chemical ionization mass spectrometry.

    PubMed

    Ley, F R; Jeffcoat, A R; Thomas, B F

    1996-02-02

    Ibogaine is naturally occurring indole alkaloid that is currently being considered as a treatment medication for drug dependence. Although there have been a variety of investigations regarding the mechanisms of action and pharmacology of ibogaine, relatively little has been reported regarding quantitative methods. Because of the paucity of analytical methodologies, studies involving the pharmacokinetics and metabolism of ibogaine have also been limited. A method is described for the determination of ibogaine levels in plasma by gas chromatography -- methane chemical ionization mass spectrometry. [13C2H3]Ibogaine was synthesized and used as an internal standard to control for recovery during sample preparation. The assay requires one ml of plasma and is shown to be a selective and sensitive means of ibogaine quantitation.

  3. Determination of descriptors for fragrance compounds by gas chromatography and liquid-liquid partition.

    PubMed

    Karunasekara, Thushara; Poole, Colin F

    2012-04-27

    Retention factors on a minimum of eight stationary phases at various temperatures by gas-liquid chromatography and liquid-liquid partition coefficients for five totally organic biphasic systems were combined to estimate descriptors for 28 fragrance compounds with an emphasis on compounds that are known or potential allergens. The descriptors facilitated the estimation of several properties of biological and environmental interest (sensory irritation threshold, odor detection threshold, nasal pungency threshold, skin permeability from water, skin-water partition coefficients, octanol-water partition coefficients, absorption by air particles, adsorption by diesel soot particles, air-water partition coefficients, and adsorption by film water). The descriptors are suitable for use in the solvation parameter model and facilitate the estimation of a wide range of physicochemical, chromatographic, biological, and environmental properties using existing models.

  4. Quantitative detection of trace explosive vapors by programmed temperature desorption gas chromatography-electron capture detector.

    PubMed

    Field, Christopher R; Lubrano, Adam; Woytowitz, Morgan; Giordano, Braden C; Rose-Pehrsson, Susan L

    2014-07-25

    The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples.

  5. Determination of Hexachlorocyclohexane by Gas Chromatography Combined with Femtosecond Laser Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Yang, Xixiang; Imasaka, Tomoko; Li, Adan; Imasaka, Totaro

    2016-12-01

    Structural isomers and enantiomers of hexachlorocyclohexane (HCH) were separated using a chiral column by gas chromatography and quantitatively determined by multiphoton ionization mass spectrometry using an ultraviolet femtosecond laser (200 and 267 nm) as the ionization source. The order of elution of the enantiomers (i.e., (+)-α-HCH and (-)-α-HCH) was predicted from stabilization energies calculated for the complexes using permethylated γ-cyclodextrin as the stationary phase of the column, and the results were compared with the experimental data. The molecular ions observed for HCH were weak, even though they can be ionized through a process of resonance enhanced two-photon ionization at 200 nm. This unfavorable result can be attributed to the dissociation of the molecular ion, as predicted from quantum chemical calculations.

  6. Rapid measurement of phytosterols in fortified food using gas chromatography with flame ionization detection.

    PubMed

    Duong, Samantha; Strobel, Norbert; Buddhadasa, Saman; Stockham, Katherine; Auldist, Martin; Wales, Bill; Orbell, John; Cran, Marlene

    2016-11-15

    A novel method for the measurement of total phytosterols in fortified food was developed and tested using gas chromatography with flame ionization detection. Unlike existing methods, this technique is capable of simultaneously extracting sterols during saponification thus significantly reducing extraction time and cost. The rapid method is suitable for sterol determination in a range of complex fortified foods including milk, cheese, fat spreads, oils and meat. The main enhancements of this new method include accuracy and precision, robustness, cost effectiveness and labour/time efficiencies. To achieve these advantages, quantification and the critical aspects of saponification were investigated and optimised. The final method demonstrated spiked recoveries in multiple matrices at 85-110% with a relative standard deviation of 1.9% and measurement uncertainty value of 10%.

  7. Confirmatory tests for drugs in the workplace by gas chromatography-mass spectrometry.

    PubMed

    Goldberger, B A; Cone, E J

    1994-07-15

    The Mandatory Guidelines for Federal Workplace Drug Testing Programs require the use of gas chromatography-mass spectrometry (GC-MS) for the confirmation of presumptive positive urine specimens. This review focuses upon GC-MS methods developed specifically for forensic confirmation of amphetamine, methamphetamine, 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-acid), benzoylecgonine, morphine, codeine and phencyclidine in urine for purposes of workplace drug testing. In addition, current laboratory issues pertaining to each drug class are reviewed. Generally, drug assays utilized either liquid-liquid or solid-phase extraction methods, derivatization if necessary, and GC-MS detection operating in the selected ion monitoring mode or by full scan acquisition.

  8. Accelerating analysis for metabolomics, drugs and their metabolites in biological samples using multidimensional gas chromatography.

    PubMed

    Mitrevski, Blagoj S; Kouremenos, Konstantinos A; Marriott, Philip J

    2009-05-01

    Gas chromatography (GC) with mass spectrometry (MS) is one of the great enabling analytical tools available to the chemical and biochemical analyst for the measurement of volatile and semi-volatile compounds. From the analysis result, it is possible to assess progress in chemical reactions, to monitor environmental pollutants in a wide range of soil, water or air samples, to determine if an athlete or horse trainer has contravened doping laws, or if crude oil has migrated through subsurface rock to a reservoir. Each of these scenarios and samples has an associated implementation method for GC-MS. However, few samples and the associated interpretation of data is as complex or important as biochemical sample analysis for trace drugs or metabolites. Improving the analysis in both the GC and MS domains is a continual search for better separation, selectivity and sensitivity. Multidimensional methods are playing important roles in providing quality data to address the needs of analysts.

  9. Investigation of the thermal oxidation of a polybutadiene by headspace sampling-gas chromatography.

    PubMed

    Judge, M D

    1994-05-01

    A novel method was developed, utilizing headspace sampling in conjunction with gas chromatography, to quantitatively follow the thermal oxidation in air of a low molecular weight, hydroxy-terminated polybutadiene. This method was found to offer an efficient and simple technique by which to analyze both the rate and the extent of oxidation of the polymer. Rate studies of the oxidation revealed an induction period followed by self-catalyzed oxidation, the rate of which quickly becomes controlled by diffusion of oxygen into the polymer. By determining the rate of oxygen consumption at various temperatures, an Arrhenius-type plot was derived and an activation energy value of 13 kcal/mol was calculated. The relative effects on oxidation of a number of common antioxidants and organometallic cure catalysts were also determined by this technique.

  10. [Determination of 10 volatile organic compounds in toys by headspace gas chromatography-mass spectrometry].

    PubMed

    Lü, Qing; Zhang, Qing; Kang, Suyuan; Bai, Hua; Wang, Chao

    2010-08-01

    A headspace gas chromatography-mass spectrometry (HS-GC-MS) method was developed for the determination of 10 residual volatile organic compounds (VOCs) in toys. The experimental conditions such as headspace temperature, headspace time and the analytical conditions of GC-MS were optimized. Toy samples were treated at 140 degrees C for 45 min, and then the evolved products were separated on a DB-624 column, determined by MS and quantified by external standard method. The recoveries were from 79% to 106% and the relative standard deviations (RSDs) were from 0.4% to 5.6%. The linear range was 0.001 - 2.0 microg with a good linear correlation coefficient (r > 0.994 0) and the limits of quantification (LOQ) were less than 0 66 mg/kg. The method is accurate, simple, rapid, and is suitable for the analysis of residual VOCs in various toys.

  11. Determination of selected fatty acids in dried sweat spot using gas chromatography with flame ionization detection.

    PubMed

    Kanďár, Roman; Drábková, Petra; Andrlová, Lenka; Kostelník, Adam; Čegan, Alexander

    2016-11-01

    A method is described for the determination of fatty acids in dried sweat spot and plasma samples using gas chromatography with flame ionization detection. Plasma and dried sweat spot samples were obtained from a group of blood donors. The sweat was collected from each volunteer during exercise. Sweat was spotted onto collection paper containing butylated hydroxytoluene. Fatty acids were derivatized with acetyl chloride in methanol to form methyl esters of fatty acids. The fatty acids in dried sweat spot samples treated with butylated hydroxytoluene and stored at -20°C were stable for 3 months. Our results indicate that sweat contains, among fatty acids with short chain, also fatty acids with long chain and unsaturated fatty acids. Linear relationships between percentage content of selected fatty acids in dried sweat spot and plasma were observed.

  12. Dispersive surface properties of glass-ionomer cements determined by inverse gas chromatography

    NASA Astrophysics Data System (ADS)

    Andrzejewska, E.; Voelkel, A.; Andrzejewski, M.; Limanowska-Shaw, H.

    2005-05-01

    The surface properties of several glass-ionomer cements (GIC), restorative dental materials, (GC-Fuji, Chemadent G-J, Ketac Fil and Ketac Molar) were investigated for the first time by means of inverse gas chromatography. This method enables characterization of surface activity in dispersive (non-polar) and acid-base interactions. The ability of the surface of glass-ionomers to participate in dispersive interactions was expressed by the use of the dispersive component of surface free energy γsd. This parameter was determined with satisfactory precision, meaning that the values of γsd can be further used in the discussion of the influence of the type of GIC, its preparation and the storage time on the surface properties. The greatest capacity for dispersive interactions was revealed by Ketac Molar and the lowest by GC-Fuji. Dispersive interactions in the surface activity of glass-ionomers increased with increasing storage time after cement preparation.

  13. Determination of pyrethroid residues in tobacco and cigarette smoke by capillary gas chromatography.

    PubMed

    Cai, Jibao; Liu, Baizhan; Zhu, Xiaolan; Su, Qingde

    2002-07-26

    The extraction of fenpropathrin, cyhalothrin, cypermethrin, fenvalerate and deltamethrin from tobacco (Nicotina tobaccum) and cigarette smoke condensate with acetone, followed by partition of resulting acetone mixture with petroleum ether, was investigated and found suitable for capillary gas chromatography (GC) residue analysis. Florisil column clean-up was found to provide clean-up procedure for tobacco and cigarette smoke condensate permitting analysis to < or = 0.01 microgram.g-1 for most of the pyrethroids by GC with a 63Ni electron capture detector (GC-ECD). Quantitative determination was obtained by the method of external standards. Cigarettes made from flue-cured tobacco spiked with different amounts of pyrethroids were used and the pyrethroid levels in mainstream smoke were determined. For all the pyrethroid residues, 1.51-15.50% were transferred from tobacco into cigarette smoke.

  14. Dating of seals produced with stamp-pad ink using gas chromatography method.

    PubMed

    Li, Biao

    2014-09-01

    Seals are often placed on important documents, and determining the date when a seal was affixed can be important to assess the authenticity of a document. In this study, thirty-seven different brands of stamp-pad inks and three different types of paper were used to make diachronic samples of the seals. The volatile components of stamp-pad ink were determined, and the stamp-pad ink was classified by gas chromatography with a flame ionization detector. Calibration curves were created to show the relationship between the content of volatile stamp-pad ink components and the age of stamp-pad ink entries stored under natural aging, UV-induced aging, and heating aging conditions. The experimental results showed that GC was useful in the analysis of stamp-pad ink and applicable for determining the relative age of stamp-pad ink entries in some cases where the seal was placed on the document within 3 months.

  15. Surface Lewis acid-base properties of polymers measured by inverse gas chromatography.

    PubMed

    Shi, Baoli; Zhang, Qianru; Jia, Lina; Liu, Yang; Li, Bin

    2007-05-18

    Surface Lewis acid-base properties are significant for polymers materials. The acid constant, K(a) and base constant, K(b) of many polymers were characterized by some researchers with inverse gas chromatography (IGC) in recent years. In this paper, the surface acid-base constants, K(a) and K(b) of 20 kinds of polymers measured by IGC in recent years are summarized and discussed, including seven polymers characterized in this work. After plotting K(b) versus K(a), it is found that the polymers can be encircled by a triangle. They scatter in two regions of the triangle. Four polymers exist in region I. K(b)/K(a) of the polymers in region I are 1.4-2.1. The other polymers exist in region II. Most of the polymers are relative basic materials.

  16. [Determination of residual epichlorohydrin and sym-dichloroisopropyl alcohol in cationic etherified reagent by gas chromatography].

    PubMed

    Zhou, Weiyi; Fan, Guoliang; Jiang, Dongfeng

    2004-11-01

    A method for the determination of the residual epichlorohydrin and sym-dichloroisopropyl alcohol in cationic etherified reagent by gas chromatography has been established. Methyl benzoate, which has high extraction efficiency for the two components, was used as extractant. With an HP-5 capillary column, the two components were baseline separated and they eluted before the extractant. The linear ranges achieved were 5 - 590 mg/kg for epichlorohydrin and 21 - 480 mg/kg for sym-dichloroisopropyl alcohol. The limits of detection were 1.2 mg/kg for epichlorohydrin and 2.2 mg/kg for sym-dichloroisopropyl alcohol. Recoveries for epichlorohydrin were 95.93% - 103.42% with relative standard deviations of 2.4% - 10.6% and those for sym-dichloroisopropyl alcohol were 98.54% - 107.40% with relative standard deviations of 6.6% -11.1%. The method is simple, fast, and convenient.

  17. Use of Gas Chromatography-Mass Spectrometry (GC-MS) in Nonscience Major Course Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Kostecka, Keith S.; Lerman, Zafra M.; Angelos, Sanford A.

    1996-06-01

    Gas chromatography-mass spectrometry (GC-MS) has been utilized with nonscience majors in the courses: "Modern Methods in Science: Discovering Molecular Secrets"; "The Extraordinary Chemistry of Ordinary Things"; "From Ozone to Oil Spills: Chemistry, the Environment and You"; and "Crime Lab Chemistry: Solving Crime through Analytical Chemistry". Our efforts have centered on introducing prospective science communicators (film, video, radio, television, and journalism majors) to science relative to their majors and personal interests. Quality lecture-discussion topics, "mystery"-based laboratory activities have assisted in introducing and/or explaining specific areas of chemistry that attempt to reduce fear of subject matter. Students have also used GC-MS, as a form of alternative assessment, in course projects that have been based on their majors, personal interests, and cultural backgrounds. Students have also conducted advanced independent work in different areas of chemistry, including the analysis of nail polishes and lacquers and eleven aromatic compounds present in three different brands of gasoline.

  18. Gas Chromatography/Atmospheric Pressure Chemical Ionization Tandem Mass Spectrometry for Fingerprinting the Macondo Oil Spill.

    PubMed

    Lobodin, Vladislav V; Maksimova, Ekaterina V; Rodgers, Ryan P

    2016-07-05

    We report the first application of a new mass spectrometry technique (gas chromatography combined to atmospheric pressure chemical ionization tandem mass spectrometry, GC/APCI-MS/MS) for fingerprinting a crude oil and environmental samples from the largest accidental marine oil spill in history (the Macondo oil spill, the Gulf of Mexico, 2010). The fingerprinting of the oil spill is based on a trace analysis of petroleum biomarkers (steranes, diasteranes, and pentacyclic triterpanes) naturally occurring in crude oil. GC/APCI enables soft ionization of petroleum compounds that form abundant molecular ions without (or little) fragmentation. The ability to operate the instrument simultaneously in several tandem mass spectrometry (MS/MS) modes (e.g., full scan, product ion scan, reaction monitoring) significantly improves structural information content and sensitivity of analysis. For fingerprinting the oil spill, we constructed diagrams and conducted correlation studies that measure the similarity between environmental samples and enable us to differentiate the Macondo oil spill from other sources.

  19. Pesticide residue analysis of vegetables by gas chromatography with electron-capture detection.

    PubMed

    Fenoll, José; Hellín, Pilar; Martínez, Carmen M; Flores, Pilar

    2007-01-01

    A new and original analytical method was developed for the routine analysis of 28 multiclass pesticide residues in vegetables (green pepper, red pepper, and tomato). The extraction was performed with acetone, and the pesticides were partitioned into ethyl acetate-cyclohexane (1 + 1, v/v). Residue levels in vegetables were determined by gas chromatography (GC) with electron-capture detection. Residue identities were confirmed by GC coupled with mass spectrometry in the selected ion monitoring mode. The average recoveries in pepper and tomato obtained for all analytes studied were 67.3 and 123.1%, respectively, with relative standard deviation between 1.8 and 7.0%. The detection limit for the pesticides studied varied from 0.1 to 2.6 microg/kg. The proposed method was applied to the analysis of these compounds in vegetables grown in experimental greenhouses.

  20. [Determination of primary aromatic amines in crayons gas chromatography-mass spectrometry].

    PubMed

    Kang, Suyuan; Zhang, Qing; Bai, Hua; Wang, Chao; Lü, Qing

    2011-05-01

    A method for the determination of nine primary aromatic amines in crayon by solid phase extraction (SPE) and gas chromatography-mass spectrometry (GC-MS) was developed. The alkanes in the sample were removed with n-hexane. Then the sample was extracted twice with ultrasonic extraction by methanol. The extract was evaporated, then the concentrated solution reacted with the reducing agent (sodium hydrosulfite) for 30 min at 70 degrees C. After the extraction with a diatomite SPE column, the aromatic amines were collected and separated on an HP-5M column, determined by MS. The nine primary aromatic amines can be separated and determined successfully. Under the optimized conditions, the detection limits were 5 mg/kg and the spiked recoveries of the samples were in the range of 86.02%-102.43%. The method is accurate and stable. It can be applied in the analysis of the primary aromatic amine of real crayon samples.

  1. Enantiomeric analysis of chiral compounds in irradiated foods using multidimensional gas chromatography.

    PubMed

    Barba, Carmen; Santa-María, Guillermo; Flores, Gema; Herraiz, Marta; Calvo, Marta M

    2010-01-27

    The usefulness of both solid phase microextraction (SPME) and multidimensional gas chromatography (MDGC) coupled to mass spectrometry (MS) to detect chiral compounds in irradiated cheese was evaluated. The enantiomeric resolution of relevant chiral aroma compound was achieved by analyzing the extracts obtained from SPME by means of a permethylated beta-CD stationary phase as the main column of the multidimensional system to separate specific selected cuts containing components unresolved in the first dimension. The proposed procedure allowed to determine, in less than 90 min, that no significant variations had been produced in the stereoisomeric distribution of limonene, 3-hydroxybutanone, and 2,3-butanediol in cheese when applying irradiation doses ranging from 0 to 8 kGy.

  2. [Determination of organophosphorous pesticide residues in red wine by solid phase microextraction-gas chromatography].

    PubMed

    Hu, Yuan; Liu, Wenmin; Zhou, Yanming; Guan, Yafeng

    2006-05-01

    A method for the determination of 12 organophosphorus pesticide residues (OPs) in red wine by fiber solid phase microextraction (SPME) coupled with gas chromatography (GC) was developed and validated. The SPME phase was prepared by sol-gel technology of physical incorporation. The extraction conditions were optimized with the results of stirring rate of 1,250 r/min, NaCl mass concentration of 150 g/L, and extraction time of 30 min. With the sample volume of 25 mL, the relative standard deviations (RSD) of peak areas for most of OPs were below 5%, and the detection limits of OPs were in the range of 5 ng/L-0.38 microg/L. It can be seen from the results that this method has the potential to analyze OPs in other beverages and soft drinking materials.

  3. [Determination of doping in human urine by gas chromatography-high resolution mass spectrometry].

    PubMed

    Xing, Yan-Yi; Liu, Xin; Zhang, Yu-Mei; Wang, Xiao-Bing; Xu, You-Xuan

    2012-12-01

    A method was evaluated for determination of twenty-one doping (including nandrolone, boldenone and methandienone) in human urine by gas chromatography-high resolution mass spectrometry. Samples were prepared by liquid-liquid extraction, concentrated, TMS derivatization and limit of detection at ng x mL(-1) by MID/GC/HRMS. According to the code of the World Anti-Doping Agency (WADA), precision and recoveries of the procedure were evaluated by replicate analysis (n = 6), the recoveries in the range of 66%-103%, with the RSD below 10.0%. The precision within the day of the method with three different concentrations was also determined RSD were less than 9.5%, 10.0% and 9.7%.

  4. Analysis of the surface energy of pharmaceutical powders by inverse gas chromatography.

    PubMed

    Grimsey, Ian M; Feeley, Jane C; York, Peter

    2002-02-01

    The behavior of pharmaceutical solids, during either processing or use, can be noticeably affected by the surface energetics of the constituent particles. Several techniques exist to measure the surface energy, for example, sessile drop, and dynamic contact angle measurements. Inverse gas chromatography (IGC) is an alternative technique where the powder surface is characterized by the retention behavior of minute quantities of well-characterized vapors that are injected into a column containing the material of interest. Recently published articles using IGC on pharmaceutical powders have ranged from linking surface energetic data with triboelectric charging to studying the effect of surface moisture on surface energetics. Molecular modelling has also recently been used to explore the links between IGC data and the structural and chemical factors that influence surface properties, thereby achieving predictive knowledge regarding powder behavior during processing. In this minireview, the reported applications of IGC in the analysis of pharmaceutical powders are summarized and the major findings highlighted.

  5. [Determination of buprofezin, methamidophos, acephate, and triazophos residues in Chinese tea samples by gas chromatography].

    PubMed

    Zhang, Shuiba; Yi, Jun; Ye, Jianglei; Zheng, Wenhui; Cai, Xueqin; Gong, Zhenbin

    2004-03-01

    A method has been developed for the simultaneous determination of buprofezin, methamidophos, acephate and triazophos residues in Chinese tea samples. The pesticide residues were extracted from tea samples with a mixture of ethyl acetate and n-hexane (50:50, v/v) at 45 degrees C. The extracts were subsequently treated with a column packed with 40 mg of active carbon by gradient elution with ethyl acetate and n-hexane. Buprofenzin and the three organophosphorus pesticides were analyzed by gas chromatography using a DB-210 capillary column and a nitrogen-phosphorus detector. The recoveries for spiked standards were 73.4%-96.9%. The relative standard deviations were all within 4.63%. The limits of quantitation (3sigma) in the tea samples were about 7.0-12.0 microg/kg.

  6. High-speed, low-pressure gas chromatography-mass spectrometry for essential oil analysis.

    PubMed

    Poynter, Samuel D H; Shellie, Robert A

    2008-07-18

    Analysis of parsley and fennel essential oils was performed by using low-pressure gas chromatography-mass spectrometry (GC-MS). The low-pressure instrument configuration was achieved by fitting a GC-MS instrument with a 530microm I.D. capillary column and an appropriate capillary restrictor at the inlet of the column. Comparison of the performance of the low-pressure GC-MS setup was made with fast GC-MS using a narrow-bore capillary column. By comparing the two approaches side-by-side the benefits of low-pressure GC-MS for characterisation of moderately complex essential oils comprising less than 50 detectable components can be fully appreciated. Although efficiency is sacrificed, the improved sample capacity of the 530microm I.D. column leads to higher peak intensities and in-turn better mass spectral library matching thus providing highly satisfactory results.

  7. Quantitative Analysis and Fingerprint Profiles for Quality Control of Fructus Schisandrae by Gas Chromatography: Mass Spectrometry

    PubMed Central

    Xia, Yong-Gang; Yang, Bing-You; Liang, Jun; Yang, Qi; Wang, Di; Kuang, Hai-Xue

    2014-01-01

    This paper describes a simple, rapid, and effective quality assessment method for Fructus Schisandrae by gas chromatography-mass spectrum (GC-MS). The method was established by using specific lignan fingerprint profiles and quantitation of characteristic compounds in this herbal medicine. The GC-MS fingerprints of 15 batches of Schisandra samples from different regions of China showed similar lignan profiles. Five peaks were selected as characteristic peaks, and all of these were identified by using GC-MS techniques. The relative retention times of these characteristic peaks in the GC-MS fingerprint were established as an important parameter for identification of Schisandra samples. Meanwhile, relative peak areas may be a feasible approach to discriminate the S. chinensis and S. sphenanthera. Finally, these pharmacologically active constituents in the titled plant, schisandrins A–C and schizandrols A and B, were quantitatively determined using a validated GC-MS method. PMID:24574919

  8. Identification of 19 phthalic acid esters in dairy products by gas chromatography with mass spectrometry.

    PubMed

    Wu, Pinggu; Cai, Chenggang; Yang, Dajin; Wang, Liyuan; Zhou, Yan; Shen, Xianghong; Ma, Bingjie; Tang, Jun

    2015-01-01

    A detection method for 19 kinds of phthalic acid ester compounds analyzed by n-hexane/ether/acetonitrile 1:7:8 v/v/v mixed solvent extraction, quick, easy, cheap, effective, rugged, and safe purification and internal standard method of quantitative gas chromatography with mass spectrometry was established. This method can effectively remove interfering materials, such as lipids, fatty acids, and pigments, from dairy products. The 19 kinds of phthalic acid ester compounds were within a 0.025-0.2 mg/kg range, the recovery rate was 65.2-125.7%, relative standard deviation was 7.9-15.4% (n = 6), and the limit of detection was 0.005-0.02 mg/kg. Concentrations of the 19 kinds of phthalic acid ester compounds ranged between 0.01 and 0.12 mg/kg in ten dairy materials and 20 dairy products. The established method is simple, rapid, accurate, and highly sensitive.

  9. Gas Chromatography-Mass Spectrometry-Based Metabolic Profiling of Cerebrospinal Fluid from Epileptic Dogs

    PubMed Central

    HASEGAWA, Tetsuya; SUMITA, Maho; HORITANI, Yusuke; TAMAI, Reo; TANAKA, Katsuhiro; KOMORI, Masayuki; TAKENAKA, Shigeo

    2013-01-01

    ABSTRACT Epilepsy is a common neurological disorder with seizures, but diagnostic approaches in veterinary clinics remain limited. Cerebrospinal fluid (CSF) is a body fluid used for diagnosis in veterinary medicine. In this study, we explored canine epilepsy diagnostic biomarkers using gas chromatography-mass spectrometry (GC-MS)-based metabolic profiling of CSF and multivariate data analysis. Profiles for subjects with idiopathic epilepsy differed significantly from those of healthy controls and subjects with symptomatic epilepsy. Among 60 identified metabolites, the levels of 20 differed significantly among the three groups. Glutamic acid was significantly increased in idiopathic epilepsy, and some metabolites including ascorbic acid were changed in both forms of epilepsy. These findings show that metabolic profiles of CSF differ between idiopathic and symptomatic epilepsy and that metabolites including glutamic acid and ascorbic acid in CSF may be useful for diagnosis of canine epilepsy. PMID:24334864

  10. Analysis of Iranian rosemary essential oil: application of gas chromatography-mass spectrometry combined with chemometrics.

    PubMed

    Jalali-Heravi, Mehdi; Moazeni, Rudabeh Sadat; Sereshti, Hassan

    2011-05-06

    This paper focuses on characterization of the components of Iranian rosemary essential oil using gas chromatography-mass spectrometry (GC-MS). Multivariate curve resolution (MCR) approach was used to overcome the problem of background, baseline offset and overlapping/embedded peaks in GC-MS. The analysis of GC-MS data revealed that sixty eight components exist in the rosemary essential oil. However, with the help of MCR this number was extended to ninety nine components with concentrations higher than 0.01%, which accounts for 98.23% of the total relative content of the rosemary essential oil. The most important constituents of the Iranian rosemary are 1,8-cineole (23.47%), α-pinene (21.74%), berbonone (7.57%), camphor (7.21%) and eucalyptol (4.49%).

  11. Use of inverse gas chromatography to account for the pervaporation performance in the microemulsion breakdown.

    PubMed

    Hadj-Ziane, Amel; Moulay, Saâd; Canselier, Jean Paul

    2005-10-14

    Mass transfer phenomenon that occurs in the pervaporation process when applied to the microemulsion breakdown, was confirmed by the results of inverse gas chromatography. The stationary phase for this study was polydimethylsiloxane (PDMS), a hydrophobic polymer employed as a membrane in the pervaporation technique. The retention times of the different molecule probes (toluene, cyclohexane, and n-butanol) gave an insight into the extent of the interactions between each of these molecules and the stationary phase; these molecules were the components of the two microemulsions in study. The infinite dilution conditions allowed to determine the thermodynamic and the chromatographic parameters gamma(infinity) (the infinite dilution activity coefficient), the Flory-Huggins parameter interactions X12(infinity), and Vg(0) (the specific retention volume), respectively. The magnitudes of the latter parameters threw some light on the permselectivity of the membrane in the pervaporation operation.

  12. Rapid quantification of dimethyl methylphosphonate from activated carbon particles by static headspace gas chromatography mass spectrometry.

    PubMed

    Mitchell, Brendan L; Billingsley, Brit G; Logue, Brian A

    2013-06-07

    Activated carbon (AC) particles are utilized as an adsorbent for binding hazardous vapors in protective equipment. The binding affinity and utilization of these AC particles should be known to ensure effective and efficient use. Therefore, a simple and effective method was developed for the quantification of the chemical warfare agent simulant, dimethyl methylphosphonate (DMMP), from AC particles. Static headspace gas chromatography mass-spectrometry with internal standard, DMMP-d6, was used to perform the analysis. The method produced a linear dynamic range of 2.48-620g DMMP/kg carbon and a detection limit of 1.24g DMMP/kg carbon. Furthermore, the method produced a coefficient of variation of less than 16% for all intra- and inter-assay analyses. The method provided a simple and effective procedure for quantifying DMMP from AC particles and was applied to the analysis of a DMMP-exposed AC protective respirator filter.

  13. A micro gas chromatography column with a micro thermal conductivity detector for volatile organic compound analysis.

    PubMed

    Sun, J H; Cui, D F; Chen, X; Zhang, L L; Cai, H Y; Li, H

    2013-02-01

    In this paper, a micro gas chromatography (μGC) system contained a μGC column and a micro thermal conductivity detector (μTCD) was proposed. In order to reduce the volume of the system, some micro heaters were integrated on the surface and backside of the GC column, which could provide a robust temperature programming capability and rapidly increase the temperature of the μGC column. In addition, a silicon-glass μTCD with four-thermistor thermal conductivity cells that can offer significant advantages over previously reported designs including low dead volume, good thermal isolation, and elimination of the thermal noise was proposed in this paper. Experimental results have indicated that the μGC system with a detection limit of several ppm concentration levels separated and detected the benzene, toluene, and styrene in less than 3 min, and the μGC system also exhibited a good linear response in the test range.

  14. [Differentiation of ballpoint pen inks by thermodesorption and gas chromatography-mass spectrometry].

    PubMed

    Bügler, Jürgen; Buchner, Hans; Dallmayer, Anton

    2004-01-01

    Differentiation and classification of ink entries with dated samples of a reference collection are important aspects in the examination of questioned documents. Classification of writing inks is presently achieved by analysis of dyes and colorants contained in the ink. This technique has its limitations in newly developed ink formulations with identical dye composition but differing in their solvents and binder resins. This paper introduces a method for the determination of solvents and binder resins of an ink sample directly from paper without sample preparation. This aim is accomplished by thermodesorption of the sample followed by gas chromatography/mass spectroscopy. The method was tested on numerous samples of ballpoint pen inks, which were subsequently grouped into several solvent and resin subgroups. A case study shows the applicability of the newly developed method.

  15. Simultaneous determination of amphetamines and ketamines in urine by gas chromatography/mass spectrometry.

    PubMed

    Lin, Huei Ru; Lua, Ahai Chang

    2006-01-01

    A method for the simultaneous determination of amphetamines and ketamines (ketamine, norketamine and dehydronorketamine) in urine samples by gas chromatography/mass spectrometry was developed and validated. Urine samples were extracted with organic solvent and derivatized with trifluoroacetic anhydride (TFAA). The limits of detection and limits of quantification for each analyte were lower than 19 and 30 ng/mL, respectively. Within-day and between-day precisions were within 0.5% and 10.6%, respectively. Biases for three levels of control samples were within -10.6% and +7.8%. The concentration of dehydronorketamine was greater than those of ketamine or norketamine in 19 of 35 ketamine-positive samples. A group of 110 human urine samples previously determined to contain at least one of the target analytes was analyzed using the new method, and excellent agreement was observed with previous results.

  16. Subsurface detection of fossil fuel pollutants by photoionization and gas chromatography/mass spectrometry.

    PubMed

    Robbat, Albert; Considine, Thomas; Antle, Patrick M

    2010-09-01

    This paper describes analysis of environmental pollutants at depth without bringing sample to the surface. It is based on an improved 3-stage Peltier freeze trap, which efficiently pre-concentrates volatile coal tar and petroleum hydrocarbons, and an integrated system for detecting pollutants on-line, in real-time by photoionization detection and quantitation by gas chromatography/mass spectrometry (GC/MS) as the probe is advanced into the subsurface. Findings indicate measurement precision and accuracy for volatiles meet EPA criteria for hazardous waste site investigations. When a Teflon membrane inlet is used to detect contaminants in groundwater, its 140 degrees C temperature limit restricts analyte collection in soil to C(2)-phenanthrenes. Two case studies demonstrate the probe is well-suited to tracking petroleum and coal tar plumes from source to groundwater.

  17. Discrimination of honeys using colorimetric sensor arrays, sensory analysis and gas chromatography techniques.

    PubMed

    Tahir, Haroon Elrasheid; Xiaobo, Zou; Xiaowei, Huang; Jiyong, Shi; Mariod, Abdalbasit Adam

    2016-09-01

    Aroma profiles of six honey varieties of different botanical origins were investigated using colorimetric sensor array, gas chromatography-mass spectrometry (GC-MS) and descriptive sensory analysis. Fifty-eight aroma compounds were identified, including 2 norisoprenoids, 5 hydrocarbons, 4 terpenes, 6 phenols, 7 ketones, 9 acids, 12 aldehydes and 13 alcohols. Twenty abundant or active compounds were chosen as key compounds to characterize honey aroma. Discrimination of the honeys was subsequently implemented using multivariate analysis, including hierarchical clustering analysis (HCA) and principal component analysis (PCA). Honeys of the same botanical origin were grouped together in the PCA score plot and HCA dendrogram. SPME-GC/MS and colorimetric sensor array were able to discriminate the honeys effectively with the advantages of being rapid, simple and low-cost. Moreover, partial least squares regression (PLSR) was applied to indicate the relationship between sensory descriptors and aroma compounds.

  18. Improvements in bis(cyclopentadienyl)magnesium purity as determined with gas chromatography-mass spectroscopy

    SciTech Connect

    BARTRAM,MICHAEL E.

    2000-03-08

    Bis(cyclopentadienyl)magnesium (MgCp2) is used commonly as a source for doping nitride materials with magnesium. Increased oxygen incorporation known to accompany the use of MgCp2 makes the purity of this precursor an important consideration in nitride CVD. Gas chromatography-mass spectroscopy (GCMS) methods have now been developed for the identification of volatile impurities in MgCp2. Diethylether, an oxygen containing organic compound (CH{sub 3}CH{sub 2}OCH{sub 2}CH{sub 3}), and additional organic impurities were found in the MgCp2 supplied by three manufacturers. Subsequent refinements in the synthetic processes by these companies have resulted in the availability of MgCp2 free of ether and other organic impurities as determined by GCMS.

  19. Rapid determination of moisture content in paper materials by multiple headspace extraction gas chromatography.

    PubMed

    Xie, Wei-Qi; Chai, Xin-Sheng

    2016-04-22

    This paper describes a new method for the rapid determination of the moisture content in paper materials. The method is based on multiple headspace extraction gas chromatography (MHE-GC) at a temperature above the boiling point of water, from which an integrated water loss from the tested sample due to evaporation can be measured and from which the moisture content in the sample can be determined. The results show that the new method has a good precision (with the relative standard deviation <0.96%), high sensitivity (the limit of quantitation=0.005%) and good accuracy (the relative differences <1.4%). Therefore, the method is quite suitable for many uses in research and industrial applications.

  20. New procedure for the determination of Hansen solubility parameters by means of inverse gas chromatography.

    PubMed

    Adamska, K; Bellinghausen, R; Voelkel, A

    2008-06-27

    The Hansen solubility parameter (HSP) seems to be a useful tool for the thermodynamic characterization of different materials. Unfortunately, estimation of the HSP values can cause some problems. In this work different procedures by using inverse gas chromatography have been presented for calculation of pharmaceutical excipients' solubility parameter. The new procedure proposed, based on the Lindvig et al. methodology, where experimental data of Flory-Huggins interaction parameter are used, can be a reasonable alternative for the estimation of HSP values. The advantage of this method is that the values of Flory-Huggins interaction parameter chi for all test solutes are used for further calculation, thus diverse interactions between test solute and material are taken into consideration.

  1. Development of a novel odor measurement system using gas chromatography with surface acoustic wave sensor.

    PubMed

    Staples, Edward J; Viswanathan, Shekar

    2008-12-01

    This paper describes a novel odor measurement system for creating arrays of virtual chemical sensors with nonoverlapping responses using ultrahigh-speed gas chromatography with a surface acoustic wave sensor (GC/SAW). This GC/SAW system provides high-resolution two-dimensional olfactory images for easy recognition of many complex odors. Separation and quantification of the individual chemicals within an odor is performed in seconds. Using a solid-state mass-sensitive detector, picogram sensitivity, universal nonpolar selectivity, and electronically variable sensitivity are achieved. An integrated vapor preconcentrator coupled with the electronically variable detector allows the system to measure vapor concentrations spanning 6 or more orders of magnitude. The system attributes of high speed, accuracy, and precision provide a cost-effective and complimentary tool for traditional sensory evaluations.

  2. Identifying and quantifying contaminants contributing to endogenous analytes in gas chromatography/mass spectrometry.

    PubMed

    Tsikas, Dimitrios

    2010-09-15

    Contaminants from various sources including medical devices, laboratory materials and the environment, and analytical apparatus may contribute to their endogenous congeners at different stages of the analytical process. Here, an approach is reported for the identification and quantification of contaminating analytes in biological fluids by stable-isotope dilution gas chromatography/mass spectrometry (GC/MS) and gas chromatography/tandem mass spectrometry (GC/MS/MS) methods. This approach is based on the analysis of different sample volumes and determination of the peak area ratio (PAR) of the endogenous analyte to the stable-isotope labeled analogue serving as the internal standard. The PAR is obtained by selected-ion monitoring or selected-reaction monitoring of appropriate ions. Generation of PAR values that correlate inversely with the sample volume subjected to analysis reveals the existence of contamination. The extent of contamination is obtained by plotting the PAR of endogenous analyte to internal standard versus the reciprocal of the sample volume analyzed. Examples are given for uncontaminated and contaminated endogenous analytes in biological samples, including nitrite and nitrate analyzed by GC/MS, and the fatty acid metabolites oleic acid oxide, oleic acid ethanol amide, and arachidonic acid ethanol amide analyzed by GC/MS/MS. Dependence of the PAR of endogenous analyte to its internal standard upon derivatization time reveals a unique kind of contamination that was identified in the GC/MS analysis of nitrate in plasma as pentafluorobenzyl ester. This kind of contamination occurs at the latest stage of GC/MS analysis and cannot be controlled by reference to the internal standard.

  3. Comprehensive two-dimensional gas chromatography and food sensory properties: potential and challenges.

    PubMed

    Cordero, Chiara; Kiefl, Johannes; Schieberle, Peter; Reichenbach, Stephen E; Bicchi, Carlo

    2015-01-01

    Modern omics disciplines dealing with food flavor focus the analytical efforts on the elucidation of sensory-active compounds, including all possible stimuli of multimodal perception (aroma, taste, texture, etc.) by means of a comprehensive, integrated treatment of sample constituents, such as physicochemical properties, concentration in the matrix, and sensory properties (odor/taste quality, perception threshold). Such analyses require detailed profiling of known bioactive components as well as advanced fingerprinting techniques to catalog sample constituents comprehensively, quantitatively, and comparably across samples. Multidimensional analytical platforms support comprehensive investigations required for flavor analysis by combining information on analytes' identities, physicochemical behaviors (volatility, polarity, partition coefficient, and solubility), concentration, and odor quality. Unlike other omics, flavor metabolomics and sensomics include the final output of the biological phenomenon (i.e., sensory perceptions) as an additional analytical dimension, which is specifically and exclusively triggered by the chemicals analyzed. However, advanced omics platforms, which are multidimensional by definition, pose challenging issues not only in terms of coupling with detection systems and sample preparation, but also in terms of data elaboration and processing. The large number of variables collected during each analytical run provides a high level of information, but requires appropriate strategies to exploit fully this potential. This review focuses on advances in comprehensive two-dimensional gas chromatography and analytical platforms combining two-dimensional gas chromatography with olfactometry, chemometrics, and quantitative assays for food sensory analysis to assess the quality of a given product. We review instrumental advances and couplings, automation in sample preparation, data elaboration, and a selection of applications.

  4. Identification and Quantification of Pesticides in Environmental Waters With Solid Phase Microextraction and Analysis Using Field-Portable Gas Chromatography-Mass Spectrometry

    DTIC Science & Technology

    2004-06-10

    Microextraction and Analysis using Field-Portable Gas Chromatography-Mass Spectrometry Name of Candidate: CPT Michael J. Nack...in the thesis manuscript entitled: Identification and Quantification of Pesticides in Environmental Waters with Solid Phase Microextraction ...Pesticides in Environmental Waters with Solid Phase Microextraction and Analysis using Field-Portable Gas Chromatography-Mass Spectrometry

  5. One-step multiple component isolation from the oil of Crinitaria tatarica (Less) Sojak by preparative capillary gas chromatography with characterization by spectroscopic and spectrometric techniques

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the present work multiple component isolation from the oil of Crinitaria tatarica (Less.) Sojak. by Preparative Capillary Gas Chromatography (PCGC) with characterization by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy have been carried out. Gas chromatography (GC-FID) ...

  6. [Determination of tracer gas contents in sediment pore water of gas hydrate area by two-dimensional gas chromatography].

    PubMed

    Wang, Hu; Yang, Qunhui; Ji, Fuwu; Zhou, Huaiyang; Xue, Xiang

    2011-01-01

    A two-dimensional gas chromatographic instrument was established by the capillary flow technology (Deans Switch) and two columns (PoraPLOT Q and Molsieve 5A) and three detectors (pulsed discharge helium ionization detector, flame photometric detector and thermal conductivity detector). The instrument can be used to measure tracer gases simultaneously including hydrogen, methane, carbon dioxide and hydrogen sulfide. The detection limits of the hydrogen, methane, carbon dioxide and hydrogen sulfide were 0.51, 0.17, 82 and 0.08 micromol/mol, and the calibration curves presented good linear relationships in the range of 2-1030, 0.6-501, 120-10500 and 0.2- 49.1 micromol/mol, respectively. The relative standard deviations were less than 10% for the measurements of ten standard gases. By this method, the tracer gases in the sediment pore water of gas hydrate area in South China Sea had been detected. This method is simple, sensitive, and suitable for on-board detection. Compared with the usual methods for measuring tracer gases, the amount of a sample necessary is reduced greatly. It is useful for the survey of gas hydrate and hydrothermal resources below sea floor and for the research of dissolved gases in the ocean.

  7. Application of oil gas-chromatography in reservoir compartmentalization in a mature Venezuelan oil field

    SciTech Connect

    Munoz, N.G.; Mompart, L.; Talukdar, S.C.

    1996-08-01

    Gas chromatographic oil {open_quotes}fingerprinting{close_quotes} was successfully applied in a multidisciplinary production geology project by Maraven, S.A. to define the extent of vertical and lateral continuity of Eocene and Miocene sandstone reservoirs in the highly faulted Bloque I field, Maracaibo Basin, Venezuela. Seventy-five non-biodegraded oils (20{degrees}-37.4{degrees} API) were analyzed with gas chromatography. Fifty were produced from the Eocene Misoa C-4, C-5, C-6 or C-7 horizons, fifteen from the Miocene basal La Rosa and ten from multizone completions. Gas chromatographic and terpane and sterane biomarker data show that all of the oils are genetically related. They were expelled from a type II, Upper Cretaceous marine La Luna source rock at about 0.80-0.90% R{sub o} maturity. Alteration in the reservoir by gas stripping with or without subsequent light hydrocarbons mixing was observed in some oils. Detailed chromatographic comparisons among the oils shown by star plots and cluster analysis utilizing several naphthenic and aromatic peak height ratios, resulted in oil pool groupings. This led to finding previously unknown lateral and vertical reservoir communication and also helped in checking and updating the scaling character of faults. In the commingled oils, percentages of each contributing zone in the mixture were also determined giving Maraven engineers a proven, rapid and inexpensive tool for production allocation and reservoir management The oil pool compartmentalization defined by the geochemical fingerprinting is in very good agreement with the sequence stratigraphic interpretation of the reservoirs and helped evaluate the influence of structure in oil migration and trapping.

  8. Detection of Caribbean fruit fly [(Anastrepha suspensa Loew (Diptera: Tephritidae)]-infested grapefruit with portable gas chromatography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    New technologies are being sought by plant protection officials to more quickly and efficiently identify concealed pests in imported commodities. The zNose portable gas chromatography unit was investigated as a tool for identifying organic volatile signatures indicative of Caribbean fruit fly infest...

  9. Quantitation of Phenol Levels in Oil of Wintergreen Using Gas Chromatography-Mass Spectrometry with Selected Ion Monitoring

    ERIC Educational Resources Information Center

    Sobel, Robert M.; Ballantine, David S.; Ryzhov, Victor

    2005-01-01

    Industrial application of gas chromatography-mass spectrometry (GC-MS) analysis is a powerful technique that could be used to elucidate components of a complex mixture while offering the benefits of high-precision quantitative analysis. The natural wintergreen oil is examined for its phenol concentration to determine the level of refining…

  10. An Advanced Analytical Chemistry Experiment Using Gas Chromatography-Mass Spectrometry, MATLAB, and Chemometrics to Predict Biodiesel Blend Percent Composition

    ERIC Educational Resources Information Center

    Pierce, Karisa M.; Schale, Stephen P.; Le, Trang M.; Larson, Joel C.

    2011-01-01

    We present a laboratory experiment for an advanced analytical chemistry course where we first focus on the chemometric technique partial least-squares (PLS) analysis applied to one-dimensional (1D) total-ion-current gas chromatography-mass spectrometry (GC-TIC) separations of biodiesel blends. Then, we focus on n-way PLS (n-PLS) applied to…

  11. Analyzing Inquiry Questions of High-School Students in a Gas Chromatography Open-Ended Laboratory Experiment

    ERIC Educational Resources Information Center

    Blonder, Ron; Mamlock-Naaman, Rachel; Hofstein, Avi

    2008-01-01

    This paper describes the implementation of an open-ended inquiry experiment for high-school students, based on gas chromatography (GC). The research focuses on identifying the level of questions that students ask during the GC open inquiry laboratory, and it examines whether implementing the advanced inquiry laboratory opens up new directions for…

  12. The Use of Gas Chromatography and Mass Spectrometry to Introduce General Chemistry Students to Percent Mass and Atomic Mass Calculations

    ERIC Educational Resources Information Center

    Pfennig, Brian W.; Schaefer, Amy K.

    2011-01-01

    A general chemistry laboratory experiment is described that introduces students to instrumental analysis using gas chromatography-mass spectrometry (GC-MS), while simultaneously reinforcing the concepts of mass percent and the calculation of atomic mass. Working in small groups, students use the GC to separate and quantify the percent composition…

  13. Systematic study of high molecular weight compounds in Amazonian plants by high temperature gas chromatography-mass spectrometry.

    PubMed

    de Siqueira, D S; Pereira, A S; Cabral, J A; Cid Ferreira, C A; de Aquino Neto, F R

    2000-01-01

    The fractions of hexane and dichloromethane extraction from marupá (Simaruba amara) and (Bertholletia excelsa) leaves were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds can be characterized including unusual high molecular weight compounds.

  14. SIMULTANEOUS DETERMINATION OF ORGANOTIN, ORGANOLEAD, AND ORGANOMERCURY COMPOUNDS IN ENVIRONMENTAL SAMPLES USING CAPILLARY GAS CHROMATOGRAPHY WITH ATOMIC EMISSION DETECTION

    EPA Science Inventory

    As part of a continuing evaluation of new analytical and sample preparation techniques conducted by the US Environmental Protection Agency (EPA), the use of capillary gas chromatography with atomic emission detection (GC-AED) for the simultaneous determination of organotin, organ...

  15. Implementation of Gas Chromatography and Microscale Distillation into the General Chemistry Laboratory Curriculum as Vehicles for Examining Intermolecular Forces

    ERIC Educational Resources Information Center

    Csizmar, Clifford M.; Force, Dee Ann; Warner, Don L.

    2011-01-01

    As part of an NSF-funded Course Curriculum and Laboratory Improvement (CCLI) project that seeks, in part, to increase student exposure to scientific instrumentation, a gas chromatography experiment has been integrated into the second-semester general chemistry laboratory curriculum. The experiment uses affordable, commercially available equipment…

  16. CAPILLARY GAS CHROMATOGRAPHY-ATOMIC EMISSION DETECTION METHOD FOR THE DETERMINATION OF PENTYLATED ORGANOTIN COMPOUNDS: INTERLABORATORY STUDY

    EPA Science Inventory

    A capillary gas chromatography-atomic emission detection (GC-AED) method was developed for the U. S. Environmental Protection Agency's Environmental Monitoring Systems Laboratory in Las Vegas, NV, for determination of selected organotin compounds. Here we report on an interlabora...

  17. Introducing Students to Gas Chromatography-Mass Spectrometry Analysis and Determination of Kerosene Components in a Complex Mixture

    ERIC Educational Resources Information Center

    Pacot, Giselle Mae M.; Lee, Lyn May; Chin, Sung-Tong; Marriott, Philip J.

    2016-01-01

    Gas chromatography-mass spectrometry (GC-MS) and GC-tandem MS (GC-MS/MS) are useful in many separation and characterization procedures. GC-MS is now a common tool in industry and research, and increasingly, GC-MS/MS is applied to the measurement of trace components in complex mixtures. This report describes an upper-level undergraduate experiment…

  18. Determination of BROMATE AT PARTS-PER-TRILLION LEVELS BY GAS CHROMATOGRAPHY-MASS SPECTROMETRY WITH NEGATIVE CHEMICAL IONIZATION

    EPA Science Inventory

    The ozonation of bromide-containing source waters produces bromate as a class 2B carcinogenic disinfection by-product. The present work describes the determination of bromate by gas chromatography-negative chemical ionization mass spectrometry (GC-NCIMS) following a bromate react...

  19. ANALYSIS OF TRACE-LEVEL ORGANIC COMBUSTION PROCESS EMISSIONS USING NOVEL MULTIDIMENSIONAL GAS CHROMATOGRAPHY-MASS SPECTROMETRY PROCEDURES

    EPA Science Inventory

    The paper discusses the analysis of trace-level organic combustion process emissions using novel multidimensional gas chromatography-mass spectrometry (MDGC-MS) procedures. It outlines the application of the technique through the analyses of various incinerator effluent and produ...

  20. Multiresidue analysis of 30 organochlorine pesticides in milk and milk powder by gel permeation chromatography-solid phase extraction-gas chromatography-tandem mass spectrometry.

    PubMed

    Zheng, Guocan; Han, Chao; Liu, Yi; Wang, Jing; Zhu, Meiwen; Wang, Chengjun; Shen, Yan

    2014-10-01

    A method for simultaneous determination of the 30 organochlorine pesticides (OCP) in milk and milk powder samples has been developed. Prior to the gas chromatography-tandem mass spectrometric analysis, the residual OCP in samples were extracted with n-hexane and acetone mixture (1/1, vol/vol) and cleaned up by gel permeation chromatography and solid phase extraction. Selected reaction monitoring mode was used for gas chromatography-tandem mass spectrometric data acquisition to identify and quantify the OCP. To avoid the matrix effects, matrix-matched calibration solutions ranging from 2 to 50 ng/mL were used to record the calibration curve. Limits of quantification of all OCP were 0.8 μg/kg. With the exception of endrin, limits of quantification are significantly lower than maximum residue limits set by the European Union and China. The average recoveries were in the range of 70.1 to 114.7% at 3 spiked concentration levels (0.8, 2.0, and 10.0 μg/kg) with residual standard deviation lower than 12.9%. The developed method was successfully applied to analyze the OCP in commercial milk products.

  1. Fast volatile organic compound recovery from soil standards for analysis by thermal desorption gas chromatography.

    PubMed

    Meniconi, Maria de Fátima Guadalupe; Parris, R; Thomas, C L P

    2003-10-01

    The development of high-throughput environmental screening assays are needed to meet high-specification data quality objectives (DQOs) that require large numbers of samples to be taken and analysed rapidly. The acquisition and stabilisation of the sample is a key technical and operational challenge in analytical sequences associated with the determination of volatile organic compound (VOC) contamination of soils. Further the development of miniaturised and embedded analytical systems for environmental conditioning monitoring requires the development of new sampling techniques. A proof-of-concept study is described that shows how pressurised gas, in this case carbon dioxide, may be used to recover reversibly-bound VOCs from soil into an adsorbent sampler, and then analysed by thermal desorption-gas chromatography. The effects of the volume of the pressurised gas, the gas flow rate and the mass of the soil sample on the recovery efficiency and breakthrough from the adsorbent trap were investigated in a preliminary characterisation study. Two distinct approaches were identified. The first involved ventilation of the voids within the soil matrix to displace the soil-gas headspace, a rapid screening approach. The second involved a more prolonged purge of the matrix to strip reversibly bound species into the gas phase and hence pass them into the adsorbent trap, a purge and trap approach. The shortest possible sample processing time required to yield analytically useful responses was 5 s with the use of the headspace approach. In this case n-octane, benzene and toluene were recovered from conditioned spiked soil samples at concentrations in the range 42 to 1690 mg kg(-1). The limit of detection for the system was estimated to be no greater than 1.2 mg kg(-1). Using the purge and trap variant enabled recovery efficiencies greater than 93% to be achieved with liquid spikes of n-octane onto soil samples. These preliminary studies showed that a system based on this approach

  2. High speed Deans switch for low duty cycle comprehensive two-dimensional gas chromatography.

    PubMed

    Ghosh, Abhijit; Bates, Carly T; Seeley, Stacy K; Seeley, John V

    2013-05-24

    A new high-speed valve-based modulator has been designed and tested for use in comprehensive two-dimensional gas chromatography (GC×GC). The modulator is a Deans switch constructed from two micro-volume fittings and a solenoid valve. Modulator performance was characterized over a wide range of device settings including the magnitude of the switching flow, the gap between the tips of the primary and secondary column, the primary column flow rate, and the carrier gas identity. Under optimized conditions, the modulator was found to be capable of generating narrow pulses (<50ms) of primary effluent with a 2mL/min secondary column flow. This capability will ultimately allow the modulator to be used with GC×GC separations employing a wide range of detectors and secondary column geometries. The main disadvantage of this modulator is that it employs a low sampling duty cycle, and thus it produces separations with sensitivities that are lower than those produced with thermal modulators or differential flow modulators. The efficacy of the new high-speed Deans switch modulator was demonstrated through the GC×GC separation of a hydrocarbon standard and gasoline. Precise quantitation of individual components was possible provided the modulation ratio was kept greater than 2.0.

  3. Determination of ortho-phenylphenol in human urine by gas chromatography-mass spectrometry.

    PubMed

    Bartels, M J; Brzak, K A; Bormett, G A

    1997-12-05

    A sensitive gas chromatographic-mass spectrometric method was developed to quantitate total o-phenylphenol (OPP) (free plus conjugates) in human urine. Conjugates of OPP were acid-hydrolyzed to free OPP, derivatized to the pentafluorobenzoyl ester derivative and analyzed via negative-ion chemical ionization gas chromatography-mass spectrometry. Two stable isotope analogs of OPP were shown to be suitable as internal standards for this method (D2-phenol ring, 13C6-phenyl ring). A synthetic method is presented for the preparation of the D2-OPP internal standard. The 13C6-OPP analog was also shown to be useful as an alternate test material for laboratory-based exposure studies. The limit of quantitation for this method was 1 ng OPP/ml urine. Calibration curves were linear for the analyte over the concentration range of 0.5-1117 ng OPP/ml urine. Relative recovery of OPP from urine ranged from 97.0 to 104.7%. Low levels of OPP (mean=6+/-7 ng/ml; n=22) were found in control human urine samples. The method was validated with urine samples obtained from human volunteers undergoing a dermal exposure study with 12C-/13C6-/14C-OPP. This method was developed to aid in assessments of human exposure to OPP during a variety of uses of the compound.

  4. Profiling methods to identify cold-regulated primary metabolites using gas chromatography coupled to mass spectrometry.

    PubMed

    Dethloff, Frederik; Erban, Alexander; Orf, Isabel; Alpers, Jessica; Fehrle, Ines; Beine-Golovchuk, Olga; Schmidt, Stefanie; Schwachtje, Jens; Kopka, Joachim

    2014-01-01

    This book chapter describes the analytical procedures required for the profiling of a metabolite fraction enriched for primary metabolites. The profiling is based on routine gas chromatography coupled to mass spectrometry (GC-MS). The generic profiling method is adapted to plant material, specifically to the analysis of single leaves from plants that were exposed to temperature stress experiments. The described method is modular. The modules include a rapid sampling and metabolic inactivation protocol for samples in a wide size range, a sample extraction procedure, a chemical derivatization step that is required to make the metabolite fraction amenable to gas chromatographic analysis, a routine GC-MS method, and finally the procedures of data processing and data mining. A basic and extendable set of standardizations for metabolite recovery and retention index alignment of the resulting GC-MS chromatograms is included. The method has two applications: (1) the rapid screening for changes of relative metabolite pools sizes under temperature stress and (2) the verification of cold-regulated metabolites by exact quantification using a GC-MS protocol with extended internal and external standardization.

  5. Modeling Transport in Gas Chromatography Columns for the Micro-ChemLab

    SciTech Connect

    ADKINS,DOUGLAS R.; FRYE-MASON,GREGORY CHARLES; HUDSON,MARY L.; KOTTENSTETTE,RICHARD; MATZKE,CAROLYN M.; SALINGER,ANDREW G.; SHADID,JOHN N.; WONG, CHUNGNIN CHANN

    1999-09-01

    The gas chromatography (GC) column is a critical component in the microsystem for chemical detection ({mu}ChemLab{trademark}) being developed at Sandia. The goal is to etch a meter-long GC column onto a 1-cm{sup 2} silicon chip while maintaining good chromatographic performance. Our design strategy is to use a modeling and simulation approach. We have developed an analytical tool that models the transport and surface interaction process to achieve an optimized design of the GC column. This analytical tool has a flow module and a separation module. The flow module considers both the compressibility and slip flow effects that may significantly influence the gas transport in a long and narrow column. The separation module models analyte transport and physico-chemical interaction with the coated surface in the GC column. It predicts the column efficiency and performance. Results of our analysis will be presented in this paper. In addition to the analytical tool, we have also developed a time-dependent adsorption/desorption model and incorporated this model into a computational fluid dynamics (CFD) code to simulate analyte transport and separation process in GC columns. CFD simulations can capture the complex three-dimensional flow and transport dynamics, whereas the analytical tool cannot. Different column geometries have been studied, and results will be presented in this paper. Overall we have demonstrated that the modeling and simulation approach can guide the design of the GC column and will reduce the number of iterations in the device development.

  6. Properties of water as a novel stationary phase in capillary gas chromatography.

    PubMed

    Gallant, Jonathan A; Thurbide, Kevin B

    2014-09-12

    A novel method of separation that uses water as a stationary phase in capillary gas chromatography (GC) is presented. Through applying a water phase to the interior walls of a stainless steel capillary, good separations were obtained for a large variety of analytes in this format. It was found that carrier gas humidification and backpressure were key factors in promoting stable operation over time at various temperatures. For example, with these measures in place, the retention time of an acetone test analyte was found to reduce by only 44s after 100min of operation at a column temperature of 100°C. In terms of efficiency, under optimum conditions the method produced about 20,000 plates for an acetone test analyte on a 250μm i.d.×30m column. Overall, retention on the stationary phase generally increased with analyte water solubility and polarity, but was relatively little correlated with analyte volatility. Conversely, non-polar analytes were essentially unretained in the system. These features were applied to the direct analysis of different polar analytes in both aqueous and organic samples. Results suggest that this approach could provide an interesting alternative tool in capillary GC separations.

  7. Determination of benzene residues in recycled polyethylene terephthalate (PETE) by dynamic headspace-gas chromatography.

    PubMed

    Komolprasert, V; Hargraves, W A; Armstrong, D J

    1994-01-01

    A dynamic headspace-gas chromatography (HS/GC) method was developed to quantitate benzene in recycled PETE material derived from 21 PETE beverage bottles. The analytical system consisted of a purge-and-trap apparatus which was interfaced directly with a gas chromatograph/flame ionization detector. Cryofocusing and non-cryofocusing GC systems were used. The technique was applied to spiked PETE test samples which were prepared at various benzene concentrations ranging from 100 ppb to 117 ppm. The initial spiked benzene concentration in the PETE test samples was determined gravimetrically. The HS/GC technique was limited by the slow desorption rate of benzene from the PETE matrix; as a result, multipurges were performed at 60 degrees C. Regression analysis was done on the multipurge data to develop a desorption model which would predict the total amount of benzene in the PETE. The calculated results agreed with the experimental recoveries within +/- 10%. Recovery depended on the initial benzene level in the PETE and ranged from 70 to 90% after the first five purges.

  8. Application of knowledge-based network processing to automated gas chromatography data interpretation

    SciTech Connect

    Levis, A.P.; Timpany, R.G.; Klotter, D.A.

    1995-10-01

    A method of translating a two-way table of qualified symptom/cause relationships into a four layer Expert Network for diagnosis of machine or sample preparation failure for Gas Chromatography is presented. This method has proven to successfully capture an expert`s ability to predict causes of failure in a Gas Chromatograph based on a small set of symptoms, derived from a chromatogram, in spite of poorly defined category delineations and definitions. In addition, the resulting network possesses the advantages inherent in most neural networks: the ability to function correctly in the presence of missing or uncertain inputs and the ability to improve performance through data-based training procedures. Acquisition of knowledge from the domain experts produced a group of imprecise cause-to-symptom relationships. These are reproduced as parallel pathways composed of Symptom-Filter-Combination-Cause node chains in the network representation. Each symptom signal is passed through a Filter node to determine if the signal should be interpreted as positive or negative evidence and then modified according to the relationship established by the domain experts. The signals from several processed symptoms are then combined in the Combination node(s) for a given cause. The resulting value is passed to the Cause node and the highest valued Cause node is then selected as the most probable cause of failure.

  9. [Analysis of cis-9, trans-11-conjugated linoleic acid in milk fat by capillary gas chromatography].

    PubMed

    Wang, Xiaojing; Shen, Xiangzhen; Han, Hangru; Zhao, Ruqian; Chen, Jie

    2006-11-01

    Conjugated linoleic acid (CLA) is a term representing a mixture of positional and geometric isomers of octadecadienoic acid with a conjugated double bond system. Conjugated linoleic acid has attracted a great deal of interest among nutritionists because it is a natural fat component that appears to have a number of health improvement properties. The cis-9, trans-11-CLA is the major CLA isomer found in dairy products accounting for 75% to 90% of the total CLA in milk fat. A capillary gas chromatographic method equipped with a flame ionization detector for the analysis of the cis-9, trans-11-CLA in milk fat was developed. The cis-9, trans-11-CLA was extracted with hexane-isopropanol, methylated with methanol-sodium methylate and cis-9, trans-11-CLA was separated and quantified using gas chromatography. Retention time of the peaks was used for qualitative analysis, while external standard method was used for quantitative analysis. The recovery of the cis-9, trans-11-CLA was 100.26%. The relative standard deviation was 1.9% (n = 6). This method presented is advantageous for high precision, high sensitivity analysis with smaller sample size and simpler pretreatment. It would be of significance for analyzing the contents of other fatty acids in the milk and milk products.

  10. Determination of Morphine and Codeine in Human Urine by Gas Chromatography-Mass Spectrometry

    PubMed Central

    Zhang, Xiaoqian; Cao, Gaozhong; Hu, Guoxin

    2013-01-01

    A sensitive and selective gas chromatography-mass spectrometry (GC-MS) method was developed and validated for the determination of morphine and codeine in human urine. The GC-MS conditions were developed. The analysis was carried out on a HP-1MS column (30 m × 0.25 mm, 0.25 μm) with temperature programming, and Helium was used as the carrier gas with a flow rate of 1.0 mL/min. Selected ion monitoring (SIM) mode was used to quantify morphine and codeine. The derivation solvent, temperature, and time were optimized. A mixed solvent of propionic anhydride and pyridine (5 : 2) was finally used for the derivation at 80°C for 3 min. Linear calibration curves were obtained in the concentration range of 25–2000.0 ng/mL, with a lower limit of quantification of 25 ng/mL. The intra- and interday precision (RSD) values were below 13%, and the accuracy was in the range 87.2–108.5%. This developed method was successfully used for the determination of morphine and codeine in human urine for forensic identification study. PMID:24222889

  11. Development of an automated high-temperature valveless injection system for online gas chromatography

    DOE PAGES

    Kreisberg, N. M.; Worton, D. R.; Zhao, Y.; ...

    2014-12-12

    A reliable method of sample introduction is presented for online gas chromatography with a special application to in situ field portable atmospheric sampling instruments. A traditional multi-port valve is replaced with a valveless sample introduction interface that offers the advantage of long-term reliability and stable sample transfer efficiency. An engineering design model is presented and tested that allows customizing this pressure-switching-based device for other applications. Flow model accuracy is within measurement accuracy (1%) when parameters are tuned for an ambient-pressure detector and 15% accurate when applied to a vacuum-based detector. Laboratory comparisons made between the two methods of sample introductionmore » using a thermal desorption aerosol gas chromatograph (TAG) show that the new interface has approximately 3 times greater reproducibility maintained over the equivalent of a week of continuous sampling. Field performance results for two versions of the valveless interface used in the in situ instrument demonstrate typically less than 2% week-1 response trending and a zero failure rate during field deployments ranging up to 4 weeks of continuous sampling. Extension of the valveless interface to dual collection cells is presented with less than 3% cell-to-cell carryover.« less

  12. Nitrogen isotopic analyses by isotope-ratio-monitoring gas chromatography/mass spectrometry

    NASA Technical Reports Server (NTRS)

    Merritt, D. A.; Hayes, J. M.

    1994-01-01

    Amino acids containing natural-abundance levels of 15N were derivatized and analyzed isotopically using a technique in which individual compounds are separated by gas chromatography, combusted on-line, and the product stream sent directly to an isotope-ratio mass spectrometer. For samples of N2 gas, standard deviations of ratio measurement were better than 0.1% (Units for delta are parts per thousand or per million (%).) for samples larger than 400 pmol and better than 0.5% for samples larger than 25 pmol (0.1% 15N is equivalent to 0.00004 atom % 15N). Results duplicated those of conventional, batchwise analyses to within 0.05%. For combustion of organic compounds yielding CO2/N2 ratios between 14 and 28, in particular for N-acetyl n-propyl derivatives of amino acids, delta values were within 0.25% of results obtained using conventional techniques and standard deviations were better than 0.35%. Pooled data for measurements of all amino acids produced an accuracy and precision of 0.04 and 0.23%, respectively, when 2 nmol of each amino acid was injected on column and 20% of the stream of combustion products was delivered to the mass spectrometer.

  13. Determination of trace sulfides in turbid waters by gas dialysis/ion chromatography

    SciTech Connect

    Goodwin, L.R.; Francom, D.; Urso, A.; Dieken, F.P.

    1988-02-01

    The accuracy of the methylene blue colorimetric procedure for the determination of sulfide in environmental waters and waste waters is influenced by turbidity interferences even after application of recommended pretreatment techniques. The direct analysis of sulfide by ion chromatography (IC), without sample pretreatment, is complicated by field preservation of samples with zinc ion (or equivalent). A continuous-flow procedure has been developed that converts the acid-extractable sulfide to H/sub 2/S, which is separated from the sample matrix by a gas dialysis membrane and then trapped in a dilute sodium hydroxide solution. A 200-..mu..L portion of this solution is injected into the ion chromatograph for analysis with an electrochemical detector. Detection limits as low as 1.9 ng/mL have been obtained. Good agreement was found between the gas dialysis/IC and methylene blue methods for nonturbid standards. The addition of ascorbic acid as an antioxidant is required to obtain adequate recoveries from spiked tap and well waters.

  14. The contribution of gas chromatography to the resynthesis of the post-Byzantine artist's technique.

    PubMed

    Kouloumpi, Eleni; Lawson, Graham; Pavlidis, Vassilios

    2007-02-01

    Gas chromatographic analysis of ethyl chloroformate derivatives of samples taken from the paint layers of post-Byzantine panel paintings permitted the successful characterisation of the different binding media used in them. This paper describes an analytical study of various post-Byzantine binding media such as egg yolk and egg/oil emulsion, using gas chromatography. The characterisation of these icons' binding media is an important task, as it contributes to our understanding of and the reconstruction of the post-Byzantine artists' palette. It also enables us to investigate the validity of our assumptions about the influences of Venetian style on Greek icon painting techniques from the sixteenth to the early nineteenth century, which up to now have been based on information in artists' handbooks. The methodology involves two experimental steps: (1) hydrolysis of the proteins and triglycerides in the binding media to obtain free amino acids and fatty acids, and (2) the formation of ethyl chloroformate derivatives via derivatization with ethyl chloroformate (ECF). This methodology is of considerable interest, since it permits the identifcation of the nature of the proteinaceous binders used in these works through the simultaneous derivatization and determination of amino acids and fatty acids. Advantages of this methodology include the small quantity of sample required and the minimum preparation time involved. The proteinaceous media can be determined based on the ratios of seven stable amino acids, while the type of emulsions and drying oils used can be determined from the fatty acid ratio.

  15. Characterization of Secondary Organic Aerosol Precursors Using Two-Dimensional Gas-Chromatography

    NASA Astrophysics Data System (ADS)

    Roskamp, M.; Lou, W.; Pankow, J. F.; Harley, P. C.; Turnipseed, A.; Barsanti, K. C.

    2012-12-01

    The oxidation of volatile organic compounds (VOCs) plays a role in both regional and global air quality. However, field and laboratory research indicate that the body of knowledge around the identities, quantities and oxidation processes of these compounds in the ambient atmosphere is still incomplete (e.g., Goldstein & Galbally, 2007; Robinson et al., 2009). VOCs emitted to the atmosphere largely are of biogenic origin (Guenther et al., 2006), and many studies of ambient secondary organic aerosol (SOA) suggest that SOA is largely of biogenic origin (albeit closely connected to anthropogenic activities, e.g., de Gouw and Jimenez, 2009). Accurate modeling of SOA levels and properties will require a more complete understanding of biogenic VOCs (BOCs) and their atmospheric oxidation products. For example, satellite measurements indicate that biogenic VOC emissions are two to three times greater than levels currently included in models (Heald et al., 2010). Two-dimensional gas chromatography (GC×GC) is a powerful analytical technique that shows much promise in advancing the state-of-knowledge regarding BVOCs and their role in SOA formation. In this work, samples were collected during BEACHON-RoMBAS (Bio-hydro-atmosphere Interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen - Rocky Mountain Biogenic Aerosol Study) in July and August of 2011. The field site was a Ponderosa Pine forest near Woodland, CO, inside the Manitou Experimental Forest, which is operated by the US Forest Service. The area is characteristic of the central Rocky Mountains and trace gas monitoring indicates that little anthropogenic pollution is transported from the nearby urban areas (Kim et al. 2010 and references therein). Ambient and enclosure samples were collected on ATD (adsorption/thermal desorption) cartridges and analyzed for BVOCs using two-dimensional gas chromatography (GC×GC) with time of flight mass spectrometry (TOFMS) and flame ionized detection (FID). Measurements of

  16. On-line coupled high performance liquid chromatography-gas chromatography for the analysis of contamination by mineral oil. Part 1: method of analysis.

    PubMed

    Biedermann, Maurus; Grob, Koni

    2012-09-14

    For the analysis of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH), on-line coupled high performance liquid chromatography-gas chromatography-flame ionization detection (HPLC-GC-FID) offers important advantages: it separates MOSH and MOAH in robust manner, enables direct injection of large aliquots of raw extracts (resulting in a low detection limit), avoids contamination of the sample during preparation and is fully automated. This review starts with an overview of the technology, particularly the fundamentals of introducing large volumes of solvent into GC, and their implementation into various transfer techniques. The main part deals with the concepts of MOSH and MOAH analysis, with a thorough discussion of the choices made. It is followed by a description of the method. Finally auxiliary tools are summarized to remove interfering components, enrich the sample in case of a high fat content and obtain additional information about the MOSH and MOAH composition.

  17. A novel fully automated on-line coupled liquid chromatography-gas chromatography technique used for the determination of organochlorine pesticide residues in tobacco and tobacco products.

    PubMed

    Qi, Dawei; Fei, Ting; Sha, Yunfei; Wang, Leijun; Li, Gang; Wu, Da; Liu, Baizhan

    2014-12-29

    In this study, a novel fully automated on-line coupled liquid chromatography-gas chromatography (LC-GC) technique was reported and applied for the determination of organochlorine pesticide residues (OCPs) in tobacco and tobacco products. Using a switching valve to isolate the capillary pre-column and the analytical column during the solvent evaporation period, the LC solvent can be completely removed and prevented from reaching the GC column and the detector. The established method was used to determinate the OCPs in tobacco samples. By using Florisil SPE column and employing GPC technique, polarity impurities and large molecule impurities were removed. A dynamic range 1-100ng/mL was achieved with detection limits from 1.5 to 3.3μg/kg. The method exhibited good repeatability and recoveries. This technology may provide an alternative way for trace analysis of complex samples.

  18. Use of absorbent materials in on-line coupled reversed-phase liquid chromatography-gas chromatography via the through oven transfer adsorption desorption interface.

    PubMed

    Flores, Gema; Díaz-Plaza, Eva María; Cortés, Jose Manuel; Villén, Jesús; Herraiz, Marta

    2008-11-21

    The use of absorbents as retaining materials in the through oven transfer adsorption desorption interface (TOTAD) of an on-line coupled reversed-phase liquid chromatography-gas chromatography system (RPLC-GC) is proposed for the first time. A comparative study of an adsorbent (Tenax TA) and two absorbents, namely polydimethylsiloxane and poly(50% phenyl/50% methylsiloxane) is performed to establish the best experimental conditions for the automated and simultaneous determination of 15 organophosphorus and organochlorine pesticide residues in olive oil. The proposed method provides satisfactory repeatability (RSDs lower, in general, than 8.5%) and sensitivity (limits of detection ranging from 0.6 to 81.9 microg/L) for the investigated compounds.

  19. Determination of residues of UV filters in natural waters by solid-phase extraction coupled to liquid chromatography-photodiode array detection and gas chromatography-mass spectrometry.

    PubMed

    Giokas, Dimosthenis L; Sakkas, Vasilios A; Albanis, Triantafyllos A

    2004-02-13

    This study describes a procedure for the enrichment, separation and quantification of four major UV filters in natural waters. Solid-phase extraction combined with liquid chromatography and photodiode array detection (LC-UV-DAD), and gas chromatography with mass spectroscopy (GC-MS) were employed for the analyses. LC of the four compounds with surfactant-modified hydro-organic eluents gave satisfactory resolution of overlapping peaks. In GC, a significant improvement of the detection limits was attained, but only three compounds could be detected. The method was validated for, and applied to, various water samples prone to UV filter accumulation due to recreational activities. Recoveries from real samples were 86-99% with LOQs as low as 0.5 ng/l depending on the sample volume and the analytical procedure.

  20. Detailed analysis of petroleum hydrocarbon attenuation in biopiles by high-performance liquid chromatography followed by comprehensive two-dimensional gas chromatography.

    PubMed

    Mao, Debin; Lookman, Richard; Van De Weghe, Hendrik; Van Look, Dirk; Vanermen, Guido; De Brucker, Nicole; Diels, Ludo

    2009-02-27

    Enhanced bioremediation of petroleum hydrocarbons in two biopiles was quantified by high-performance liquid chromatography (HPLC) followed by comprehensive two-dimensional gas chromatography (GCXGC). The attenuation of 34 defined hydrocarbon classes was calculated by HPLC-GCXGC analysis of representative biopile samples at start-up and after 18 weeks of biopile operation. In general, a-cyclic alkanes were most efficiently removed from the biopiles, followed by monoaromatic hydrocarbons. Cycloalkanes and polycyclic aromatic hydrocarbons (PAHs) were more resistant to degradation. A-cyclic biomarkers farnesane, trimethyl-C13, norpristane, pristane and phytane dropped to only about 10% of their initial concentrations. On the other hand, C29-C31 hopane concentrations remained almost unaltered after 18 weeks of biopile operation, confirming their resistance to biodegradation. They are thus reliable indicators to estimate attenuation potential of petroleum hydrocarbons in biopile processed soils.

  1. Partition Coefficients of Organic Compounds in New Imidazolium and Tetralkylammonium Based Ionic Liquids Using Inverse Gas Chromatography

    SciTech Connect

    Mutelet, Fabrice; Revelli, Anne-Laure; Jaubert, Jean-Noel; Sprunger, Laura; Acree, William; Baker, Gary A

    2010-01-01

    Partition coefficients of 51 organic compounds in two ionic liquids (IL), 1-ethyl-3-methylimidazolium dicyanamide and trimethylhexylammonium bis((trifluoromethyl)sulfonyl)amide, were measured using inverse gas chromatography from (322.5 to 352.5) K. These partition coefficients were converted into water-to-IL partition coefficients using the corresponding gas-to-water partition coefficients. Both sets of partition coefficients were analyzed using the Abraham solvation parameter model with cation-specific and anionspecific equation coefficients. The derived equations correlated the experimental gas-to-IL and water-to-IL partition coefficient data to within (0.12 and 0.14) log units, respectively.

  2. Gas chromatography-mass spectrometry analysis of nitrite in biological fluids without derivatization.

    PubMed

    Tsikas, Dimitrios; Böhmer, Anke; Mitschke, Anja

    2010-06-15

    We report on a gas chromatography-mass spectrometry (GC-MS) method for the quantification of nitrite in biological fluids without preceding derivatization. This method is based on the solvent extraction with ethyl acetate of nitrous acid (HONO, pK(a) = 3.29), i.e., HO(14)NO and (15)N-labeled nitrous acid (HO(15)NO) which was supplied as the sodium salt of (15)N-labeled nitrite and served as the internal standard. HO(14)NO and HO(15)NO react within the injector (at 300 degrees C) of the gas chromatograph with the solvent ethyl acetate to form presumably unlabeled and (15)N-labeled acetyl nitrite, respectively. Under negative ion chemical ionization (NICI) conditions with methane as the reagent gas, these species ionize to form O(14)NO(-) (m/z 46) and O(15)NO(-) (m/z 47), respectively. Quantification is performed by selected ion monitoring of m/z 46 for nitrite and m/z 47 for the internal standard. Nitrate at concentrations up to 20 mM does not interfere with nitrite analysis in this method. The GC-MS method was validated for the quantification of nitrite in aqueous buffer, human urine (1 mL, acidification) and saliva (0.1-1 mL, acidification), and hemolysates. The method was applied in studying reactions of nitrite (0-10 mM) with oxyhemoglobin ( approximately 6 mM) in lysed human erythrocytes (100 microL aliquots, no acidification).

  3. Analysis of small carbohydrates in several bioactive botanicals by gas chromatography with mass spectrometry and liquid chromatography with tandem mass spectrometry.

    PubMed

    Moldoveanu, Serban; Scott, Wayne; Zhu, Jeff

    2015-11-01

    Bioactive botanicals contain natural compounds with specific biological activity, such as antibacterial, antioxidant, immune stimulating, and taste improving. A full characterization of the chemical composition of these botanicals is frequently necessary. A study of small carbohydrates from the plant materials of 18 bioactive botanicals is further described. The study presents the identification of the carbohydrate using a gas chromatographic-mass spectrometric analysis that allows detection of molecules as large as maltotetraose, after changing them into trimethylsilyl derivatives. A number of carbohydrates in the plant (fructose, glucose, mannose, sucrose, maltose, xylose, sorbitol, and myo-, chiro-, and scyllo-inositols) were quantitated using a novel liquid chromatography with tandem mass spectrometric technique. Both techniques involved new method developments. The gas chromatography with mass spectrometric analysis involved derivatization and separation on a Rxi(®)-5Sil MS column with H2 as a carrier gas. The liquid chromatographic separation was obtained using a hydrophilic interaction type column, YMC-PAC Polyamine II. The tandem mass spectrometer used an electrospray ionization source in multiple reaction monitoring positive ion mode with the detection of the adducts of the carbohydrates with Cs(+) ions. The validated quantitative procedure showed excellent precision and accuracy allowing the analysis in a wide range of concentrations of the analytes.

  4. Evaluation of gas radiation heat transfer in a 2D axisymmetric geometry using the line-by-line integration and WSGG models

    NASA Astrophysics Data System (ADS)

    Centeno, Felipe Roman; Brittes, Rogério; França, Francis. H. R.; Ezekoye, Ofodike A.

    2015-05-01

    The weighted-sum-of-gray-gases (WSGG) model is widely used in engineering computations of radiative heat transfer due to its relative simplicity, robustness and flexibility. This paper presents the computation of radiative heat transfer in a 2D axisymmetric chamber using two WSGG models to compute radiation in H2O and CO2 mixtures. The first model considers a fixed ratio between the molar concentrations of H2O and CO2, while the second allows the solution for arbitrary ratios. The correlations for both models are based on the HITEMP2010 database. The test case considers typical conditions found in turbulent methane flames, with steep variations in the temperature field as well as in the molar concentrations of the participating species. To assess the accuracy of the WSGG model, the results are compared with a solution obtained by line-by-line integration (LBL) of the spectrum.

  5. Application of capillary gas chromatography mass spectrometry/computer techniques to synoptic survey of organic material in bed sediment

    USGS Publications Warehouse

    Steinheimer, T.R.; Pereira, W.E.; Johnson, S.M.

    1981-01-01

    A bed sediment sample taken from an area impacted by heavy industrial activity was analyzed for organic compounds of environmental significance. Extraction was effected on a Soxhlet apparatus using a freeze-dried sample. The Soxhlet extract was fractionated by silica gel micro-column adsorption chromatography. Separation and identification of the organic compounds was accomplished by capillary gas chromatography/mass spectrometry techniques. More than 50 compounds were identified; these include saturated hydrocarbons, olefins, aromatic hydrocarbons, alkylated polycyclic aromatic hydrocarbons, and oxygenated compounds such as aldehydes and ketones. The role of bed sediments as a source or sink for organic pollutants is discussed. ?? 1981.

  6. Multivariate analysis of progressive thermal desorption coupled gas chromatography-mass spectrometry.

    SciTech Connect

    Van Benthem, Mark Hilary; Mowry, Curtis Dale; Kotula, Paul Gabriel; Borek, Theodore Thaddeus, III

    2010-09-01

    Thermal decomposition of poly dimethyl siloxane compounds, Sylgard{reg_sign} 184 and 186, were examined using thermal desorption coupled gas chromatography-mass spectrometry (TD/GC-MS) and multivariate analysis. This work describes a method of producing multiway data using a stepped thermal desorption. The technique involves sequentially heating a sample of the material of interest with subsequent analysis in a commercial GC/MS system. The decomposition chromatograms were analyzed using multivariate analysis tools including principal component analysis (PCA), factor rotation employing the varimax criterion, and multivariate curve resolution. The results of the analysis show seven components related to offgassing of various fractions of siloxanes that vary as a function of temperature. Thermal desorption coupled with gas chromatography-mass spectrometry (TD/GC-MS) is a powerful analytical technique for analyzing chemical mixtures. It has great potential in numerous analytic areas including materials analysis, sports medicine, in the detection of designer drugs; and biological research for metabolomics. Data analysis is complicated, far from automated and can result in high false positive or false negative rates. We have demonstrated a step-wise TD/GC-MS technique that removes more volatile compounds from a sample before extracting the less volatile compounds. This creates an additional dimension of separation before the GC column, while simultaneously generating three-way data. Sandia's proven multivariate analysis methods, when applied to these data, have several advantages over current commercial options. It also has demonstrated potential for success in finding and enabling identification of trace compounds. Several challenges remain, however, including understanding the sources of noise in the data, outlier detection, improving the data pretreatment and analysis methods, developing a software tool for ease of use by the chemist, and demonstrating our belief that

  7. 2D and 3D imaging of the gas phase close to an operating model catalyst by planar laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Blomberg, Sara; Zhou, Jianfeng; Gustafson, Johan; Zetterberg, Johan; Lundgren, Edvin

    2016-11-01

    In recent years, efforts have been made in catalysis related surface science studies to explore the possibilities to perform experiments at conditions closer to those of a technical catalyst, in particular at increased pressures. Techniques such as high pressure scanning tunneling/atomic force microscopy (HPSTM/AFM), near ambient pressure x-ray photoemission spectroscopy (NAPXPS), surface x-ray diffraction (SXRD) and polarization-modulation infrared reflection absorption spectroscopy (PM-IRAS) at semi-realistic conditions have been used to study the surface structure of model catalysts under reaction conditions, combined with simultaneous mass spectrometry (MS). These studies have provided an increased understanding of the surface dynamics and the structure of the active phase of surfaces and nano particles as a reaction occurs, providing novel information on the structure/activity relationship. However, the surface structure detected during the reaction is sensitive to the composition of the gas phase close to the catalyst surface. Therefore, the catalytic activity of the sample itself will act as a gas-source or gas-sink, and will affect the surface structure, which in turn may complicate the assignment of the active phase. For this reason, we have applied planar laser induced fluorescence (PLIF) to the gas phase in the vicinity of an active model catalysts. Our measurements demonstrate that the gas composition differs significantly close to the catalyst and at the position of the MS, which indeed should have a profound effect on the surface structure. However, PLIF applied to catalytic reactions presents several beneficial properties in addition to investigate the effect of the catalyst on the effective gas composition close to the model catalyst. The high spatial and temporal resolution of PLIF provides a unique tool to visualize the on-set of catalytic reactions and to compare different model catalysts in the same reactive environment. The technique can be

  8. 2D and 3D imaging of the gas phase close to an operating model catalyst by planar laser induced fluorescence.

    PubMed

    Blomberg, Sara; Zhou, Jianfeng; Gustafson, Johan; Zetterberg, Johan; Lundgren, Edvin

    2016-11-16

    In recent years, efforts have been made in catalysis related surface science studies to explore the possibilities to perform experiments at conditions closer to those of a technical catalyst, in particular at increased pressures. Techniques such as high pressure scanning tunneling/atomic force microscopy (HPSTM/AFM), near ambient pressure x-ray photoemission spectroscopy (NAPXPS), surface x-ray diffraction (SXRD) and polarization-modulation infrared reflection absorption spectroscopy (PM-IRAS) at semi-realistic conditions have been used to study the surface structure of model catalysts under reaction conditions, combined with simultaneous mass spectrometry (MS). These studies have provided an increased understanding of the surface dynamics and the structure of the active phase of surfaces and nano particles as a reaction occurs, providing novel information on the structure/activity relationship. However, the surface structure detected during the reaction is sensitive to the composition of the gas phase close to the catalyst surface. Therefore, the catalytic activity of the sample itself will act as a gas-source or gas-sink, and will affect the surface structure, which in turn may complicate the assignment of the active phase. For this reason, we have applied planar laser induced fluorescence (PLIF) to the gas phase in the vicinity of an active model catalysts. Our measurements demonstrate that the gas composition differs significantly close to the catalyst and at the position of the MS, which indeed should have a profound effect on the surface structure. However, PLIF applied to catalytic reactions presents several beneficial properties in addition to investigate the effect of the catalyst on the effective gas composition close to the model catalyst. The high spatial and temporal resolution of PLIF provides a unique tool to visualize the on-set of catalytic reactions and to compare different model catalysts in the same reactive environment. The technique can be

  9. A Chemical Detector for Gas Chromatography Using Pulsed Discharge Emission Spectroscopy on a Microchip

    NASA Astrophysics Data System (ADS)

    Luo, X.; Zhu, W.; Mitra, B.; Liu, J.; Liu, T.; Fan, X.; Gianchandani, Y.

    2011-12-01

    There is increasing interest in miniaturized systems for chemical analysis in harsh environments. Chemical detection by emission spectroscopy of on-chip microdischarges [1-3] can be performed at >200°C [4], suggesting utility inspace exploration, volcanic monitoring, and oil well monitoring. This abstract describes the first use of pulsed microdischarge spectroscopy for gas chromatography (GC).This effort supports NASA interests in monitoring closed-loop life support systems for spacecraft. The microdischarge occurs on a 1cm2 glass chip (Fig. 1a), with thin-film Ni electrodes separated by 160μm. A glass lid with a grooved gas-flow channel, and inlet/outlet capillary tubes are epoxy-sealed to the chip. Located downstream of the 1.7m-long, RTX-1-coated, GC separation column, the microdischarge chip is read by a spectrometer. In a typical experiment (Fig. 1b), a mixture of acetone 3.6μg, 1-hexanol 2.8μg and nitrobenzene 3.0μg, is injected, with He carrier gas at 1.56sccm, through the GC. Acetone elutes quickly while nitrobenzene is slower. Microdischarges are triggered at 0.5Hz for 6 min., and 0.04Hz thereafter. Each microdischarge consumes ≈8mJ; the average power is ≈1.14mW. The spectrum (Fig. 1b, inset) shows that the 388nm peak, representing CN/CH fragments [5], is enhanced by carbon compounds. Its strength relative to the 588nm peak of He provides a chromatogram. Fig. 1b also shows a benchmark result from a commercial flame ionization detector (FID). The differences in elution time are attributed to differences in the gas flow paths for the two detectors [1]. REFERENCES [1] Eijkel et al, Anal. Chem, 2000 [2] Mitra et al, IEEE Trans Plasma Sci, 2008 [3] Mitra et al, IEEE Sensors, 2008 [4] Wright et al, APL, 2009 [5] Pearse et al, The Identification of Molecular Spectra, 1963

  10. Evaluation of Enhanced Comprehensive 2-D Gas Chromatography-Time-Of-Flight Mass Spectrometry for the Separation of Recalcitrant Polychlorinated Biphenyl Isomers

    EPA Science Inventory

    The separation of some recalcitrant polychlorinated biphenyl (PCB) isomers in extracts from environmental compartments has been a daunting task for environmental chemists. Summed quantitation values for coeluting PCB isomers are often reported. This composite data obscures the ac...

  11. PIV, 2D-LIF and 1D-Raman measurements of flow field, composition and temperature in premixed gas turbine flames

    SciTech Connect

    Stopper, U.; Aigner, M.; Ax, H.; Meier, W.; Sadanandan, R.; Stoehr, M.; Bonaldo, A.

    2010-04-15

    Several laser diagnostic measurement techniques have been applied to study the lean premixed natural gas/air flames of an industrial swirl burner. This was made possible by equipping the burner with an optical combustion chamber that was installed in the high-pressure test rig facility at the DLR Institute of Combustion Technology in Stuttgart. The burner was operated with preheated air at various operating conditions with pressures up to p = 6 bar and a maximum thermal power of P = 1 MW. The instantaneous planar flow field inside the combustor was studied with particle image velocimetry (PIV). Planar laser induced fluorescence (PLIF) of OH radicals on a single-shot basis was used to determine the shape and the location of the flame front as well as the spatial distribution of reaction products. 1D laser Raman spectroscopy was successfully applied for the measurement of the temperature and the concentration of major species under realistic gas turbine conditions. Results of the flow field analysis show the shape and the size of the main flow regimes: the inflow region, the inner and the outer recirculation zone. The highly turbulent flow field of the inner shear layer is found to be dominated by small and medium sized vortices. High RMS fluctuations of the flow velocity in the exhaust gas indicate the existence of a rotating exhaust gas swirl. From the PLIF images it is seen that the primary reactions happened in the shear layers between inflow and the recirculation zones and that the appearance of the reaction zones changed with flame parameters. The results of the multiscalar Raman measurements show a strong variation of the local mixture fraction allowing conclusions to be drawn about the premix quality. Furthermore, mixing effects of unburnt fuel and air with fully reacted combustion products are studied giving insights into the processes of the turbulence-chemistry interaction. (author)

  12. Rapid screening and identification of illicit drugs by IR absorption spectroscopy and gas chromatography

    NASA Astrophysics Data System (ADS)

    Mengali, Sandro; Liberatore, Nicola; Luciani, Domenico; Viola, Roberto; Cardinali, Gian Carlo; Elmi, Ivan; Poggi, Antonella; Zampolli, Stefano; Biavardi, Elisa; Dalcanale, Enrico; Bonadio, Federica; Delemont, Olivier; Esseiva, Pierre; Romolo, Francesco S.

    2013-01-01

    Analytical instruments based on InfraRed Absorption Spectroscopy (IRAS) and Gas Chromatography (GC) are today available only as bench-top instrumentation for forensic labs and bulk analysis. Within the 'DIRAC' project funded by the European Commission, we are developing an advanced portable sensor, that combines miniaturized GC as its key chemical separation tool, and IRAS in a Hollow Fiber (HF) as its key analytical tool, to detect and recognize illicit drugs and key precursors, as bulk and as traces. The HF-IRAS module essentially consists of a broadly tunable External Cavity (EC) Quantum Cascade Laser (QCL), thermo-electrically cooled MCT detectors, and an infrared hollow fiber at controlled temperature. The hollow fiber works as a miniaturized gas cell, that can be connected to the output of the GC column with minimal dead volumes. Indeed, the module has been coupled to GC columns of different internal diameter and stationary phase, and with a Vapour Phase Pre-concentrator (VPC) that selectively traps target chemicals from the air. The presentation will report the results of tests made with amphetamines and precursors, as pure substances, mixtures, and solutions. It will show that the sensor is capable of analyzing all the chemicals of interest, with limits of detection ranging from a few nanograms to about 100-200 ng. Furthermore, it is suitable to deal with vapours directly trapped from the headspace of a vessel, and with salts treated in a basic solution. When coupled to FAST GC columns, the module can analyze multi-components mixes in less than 5 minutes.

  13. A volatile organic analyzer for Space Station: Description and evaluation of a gas chromatography/ ion mobility

    NASA Technical Reports Server (NTRS)

    Limero, Thomas F.; James, John T.

    1994-01-01

    A Volatile Organic Analyzer (VOA) is being developed as an essential component of the Space Station's Environmental Health System (EHS) air quality monitoring strategy to provide warning to the crew and ground personnel if volatile organic compounds exceed established exposure limits. The short duration of most Shuttle flights and the relative simplicity of the contaminant removal mechanism have lessened the concern about crew exposure to air contaminants on the Shuttle. However, the longer missions associated with the Space Station, the complex air revitalization system and the proposed number of experiments have led to a desire for real-time monitoring of the contaminants in the Space Station atmosphere. Achieving the performance requirements established for the VOA within the Space Station resource (e.g., power, weight) allocations led to a novel approach that joined a gas chromatograph (GC) to an ion mobility spectrometer (IMS). The authors of this paper will discuss the rational for selecting the GC/IMS technology as opposed to the more established gas chromatography/mass spectrometry (GC/MS) for the foundation of the VOA. The data presented from preliminary evaluations will demonstrate the versatile capability of the GC/IMS to analyze the major contaminants expected in the Space Station atmosphere. The favorable GC/IMS characteristics illustrated in this paper included excellent sensitivity, dual-mode operation for selective detection, and mobility drift times to distinguish co-eluting GC peaks. Preliminary studies have shown that the GC/IMS technology can meet surpass the performance requirements of the Space Station VOA.

  14. Characterization of oil shale waters by gas chromatography/mass spectrometry

    SciTech Connect

    Lane, D.C.; Baughman, K.J.; Jones, J.S.

    1986-09-01

    Characterization work has begun on organic compounds and compound classes to establish a baseline for the evaluation and development of alternative instrumental characterization techniques. For this purpose raw water from two oil shale processes has been subjected to an extraction and gas chromatography/mass spectrometry (GC/MS) analysis. Samples from the R-17 and Rio Blanco processes were chosen for comparison with previous characterization work reported by Poulson et al. (1984, 1985), who used low-cost gas and reverse-phase liquid chromatographic (LC) techniques. In addition, various inorganic and physical parameters were re-evaluated. The preliminary comparison of GC/MS data with the GC and reverse phase LC data previously reported by Poulson et al., indicates a number of positive correlations for both the process waters. Aliphatic carboxylic acids, cresols, xylenols, methyl pyridines, dimethyl pyridines, and trimethyl pyridines were found both in present GC/MS analysis and in earlier GC and LC analyses of the samples. In addition, trimethylphenols were observed in both the present GC/MS analysis and in the previous GC and LC analyses of the Rio Blanco sample. A number of tentatively identified compounds and compound classes were observed in the GC/MS analysis but were unreported in either the GC or LC analyses for both samples. Similarly, several compounds and compound classes previously reported by GC and LC techniques were absent in the GC/MS analysis. These discrepancies may be attributed to either the original GC and LC research design or to a fundamental chemical change in the samples used for the GC/MS characterization. Additional research is necessary in the areas of extraction design, use of comparable GC and GC/MS marker compounds for identification, standardization of chromatographic columns and GC conditions, and the validity of computer library identifications. 3 refs., 2 figs., 12 tabs.

  15. A rapid analysis of plasma/serum ethylene and propylene glycol by headspace gas chromatography.

    PubMed

    Ehlers, Alexandra; Morris, Cory; Krasowski, Matthew D

    2013-12-01

    A rapid headspace-gas chromatography (HS-GC) method was developed for the analysis of ethylene glycol and propylene glycol in plasma and serum specimens using 1,3-propanediol as the internal standard. The method employed a single-step derivitization using phenylboronic acid, was linear to 200 mg/dL and had a lower limit of quantitation of 1 mg/dL suitable for clinical analyses. The analytical method described allows for laboratories with HS-GC instrumentation to analyze ethanol, methanol, isopropanol, ethylene glycol, and propylene glycol on a single instrument with rapid switch-over from alcohols to glycols analysis. In addition to the novel HS-GC method, a retrospective analysis of patient specimens containing ethylene glycol and propylene glycol was also described. A total of 36 patients ingested ethylene glycol, including 3 patients who presented with two separate admissions for ethylene glycol toxicity. Laboratory studies on presentation to hospital for these patients showed both osmolal and anion gap in 13 patients, osmolal but not anion gap in 13 patients, anion but not osmolal gap in 8 patients, and 1 patient with neither an osmolal nor anion gap. Acidosis on arterial blood gas was present in 13 cases. Only one fatality was seen; this was a patient with initial serum ethylene glycol concentration of 1282 mg/dL who died on third day of hospitalization. Propylene glycol was common in patients being managed for toxic ingestions, and was often attributed to iatrogenic administration of propylene glycol-containing medications such as activated charcoal and intravenous lorazepam. In six patients, propylene glycol contributed to an abnormally high osmolal gap. The common presence of propylene glycol in hospitalized patients emphasizes the importance of being able to identify both ethylene glycol and propylene glycol by chromatographic methods.

  16. Predicting percent composition of blends of biodiesel and conventional diesel using gas chromatography-mass spectrometry, comprehensive two-dimensional gas chromatography-mass spectrometry, and partial least squares analysis.

    PubMed

    Pierce, Karisa M; Schale, Stephen P

    2011-01-30

    The percent composition of blends of biodiesel and conventional diesel from a variety of retail sources were modeled and predicted using partial least squares (PLS) analysis applied to gas chromatography-total-ion-current mass spectrometry (GC-TIC), gas chromatography-mass spectrometry (GC-MS), comprehensive two-dimensional gas chromatography-total-ion-current mass spectrometry (GCxGC-TIC) and comprehensive two-dimensional gas chromatography-mass spectrometry (GCxGC-MS) separations of the blends. In all four cases, the PLS predictions for a test set of chromatograms were plotted versus the actual blend percent composition. The GC-TIC plot produced a best-fit line with slope=0.773 and y-intercept=2.89, and the average percent error of prediction was 12.0%. The GC-MS plot produced a best-fit line with slope=0.864 and y-intercept=1.72, and the average percent error of prediction was improved to 6.89%. The GCxGC-TIC plot produced a best-fit line with slope=0.983 and y-intercept=0.680, and the average percent error was slightly improved to 6.16%. The GCxGC-MS plot produced a best-fit line with slope=0.980 and y-intercept=0.620, and the average percent error was 6.12%. The GCxGC models performed best presumably due to the multidimensional advantage of higher dimensional instrumentation providing more chemical selectivity. All the PLS models used 3 latent variables. The chemical components that differentiate the blend percent compositions are reported.

  17. Performance evaluation of a versatile multidimensional chromatographic preparative system based on three-dimensional gas chromatography and liquid chromatography-two-dimensional gas chromatography for the collection of volatile constituents.

    PubMed

    Pantò, Sebastiano; Sciarrone, Danilo; Maimone, Mariarosa; Ragonese, Carla; Giofrè, Salvatore; Donato, Paola; Farnetti, Sara; Mondello, Luigi

    2015-10-23

    The present research deals with the multi-collection of the most important sesquiterpene alcohols belonging to sandalwood essential oil, as reported by the international regulations: (Z)-α-santalol, (Z)-α-trans bergamotol, (Z)-β-santalol, epi-(Z)-β-santalol, α-bisabolol, (Z)-lanceol, and (Z)-nuciferol. A versatile multidimensional preparative system, based on the hyphenation of liquid and gas chromatography techniques, was operated in the LC-GC-GC-prep or GC-GC-GC-prep configuration, depending on the concentration to be collected from the sample, without any hardware or software modification. The system was equipped with a silica LC column in combination with polyethylene glycol-poly(5% diphenyl/95% dimethylsiloxane)-medium polarity ionic liquid or β-cyclodextrin based GC stationary phases. The GC-GC-GC-prep configuration was exploited for the collection of four components, by using a conventional split/splitless injector, while the LC-GC-GC-prep approach was applied for three low abundant components (<5%), in order to increase the quantity collected within a single run, by the LC injection of a high sample amount. All target compounds, whose determination is hampered by the unavailability of commercial standards, were collected at milligram levels and with a high degree of purity (>87%).

  18. Aspects of High-Resolution Gas Chromatography as Applied to the Analysis of Hydrocarbon Fuels and Other Complex Organic Mixtures. Volume 2. Survey of Sample Insertion Techniques.

    DTIC Science & Technology

    1985-06-01

    AD-A158 772 ASPECTS OF HIGH-RESOL.UTION GAS CHROMATOGRAPHY S 1ll APPLIED0 TO THE ANALYSIS 0..(U)1 DAYTON UNIV ON RESEARCH INST W A RUSEY ET AL. JUN...RESOLUTION GAS CHROMATOGRAPHY AS APPLIED TO THE ANALYSIS OF HYDROCARBON FUELS AND OTHER COMPLEX ORGANIC MIXTURES Volume II - Survey of Sample Insertion...NO. NO. 45433-6563 62203F 3048 05 91 11. TITLE (Include Security Classification) (cont’ d on reverse) ASPECTS OF HIGH-RESOLUTION GAS CHROMATOGRAPHY T

  19. Formation of new bioactive organic nitrites and their identification with gas chromatography-mass spectrometry and liquid chromatography coupled to nitrite reduction.

    PubMed

    Nilsson, Kristofer F; Lundgren, Michael; Agvald, Per; Adding, L Christofer; Linnarsson, Dag; Gustafsson, Lars E

    2011-08-01

    Nitric oxide (NO) donors, notably organic nitrates and nitrites are used therapeutically but tolerance develops rapidly, making the use of e.g. nitroglycerin difficult. NO donation in the pulmonary vascular bed might be useful in critically ill patients. Organic nitrites are not associated with tachyphylaxis but may induce methaemoglobinemia and systemic hypotension which might hamper their use. We hypothesised that new lung-selective NO donors can be identified by utilizing exhaled NO as measure for pulmonary NO donation and systemic arterial pressure to monitor hypotension and tolerance development. Solutions of alcohols and carbohydrates were reacted with NO gas and administered to ventilated rabbits for evaluation of in vivo NO donation. Chemical characterization was made by liquid chromatography with on-line nitrite reduction (LC-NO) and by gas chromatography-mass spectrometry (GC-MS). In vivo experiments showed that the hydroxyl-containing compounds treated with NO gas yielded potent NO donors, via nitrosylation to organic nitrites. Analyses by LC-NO showed that the reaction products were able to release NO in vitro. In GC-MS the reaction products were determined to be the organic nitrites, where some are new chemical entities. Non-polar donors preferentially increased exhaled NO with less effect on systemic blood pressure whereas more polar molecules had larger effects on systemic blood pressure and less on exhaled NO. We conclude that new organic nitrites suitable for intravenous administration are produced by reacting NO gas and certain hydroxyl-containing compounds in aqueous solutions. Selectivity of different organic nitrites towards the pulmonary and systemic circulation, respectively, may be determined by molecular polarity.

  20. [Determination of five representative ultraviolet filters in water by gas chromatography-mass spectrometry].

    PubMed

    Ding, Yiran; Huang, Yun; Zhao, Tingting; Cai, Qian; Luo, Yu; Huang, Bin; Zhang, Yuxia; Pan, Xuejun

    2014-06-01

    A method for the determination of five representative organic UV filters: ethylhexyl methoxycinnamate (EHMC), benzophenone-3 (BP-3), 4-methylbenzylidene camphor (4-MBC), octocrylene (OC), homosalate (HMS) in water was investigated. The method was ased on derivatization, solid phase extraction (SPE), followed by determination with gas chromatography-mass spectrometry (GC-MS). The variables involved in the derivatization of BP-3 and HMS were optimized, and SPE conditions were studied. For derivatization, 100 microL N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) was used as derivatization reagent and reacted with BP-3 and HMS at 100 degrees C for 100 min. For SPE, the pH value of water sample was adjusted to 3-5. The Oasis HLB cartridges were employed and the solution of ethyl acetate and dichloromethane (1 : 1, v/v) was used as the eluting solvent, and good recoveries of the target compounds were obtained. The limits of detection (LODs) and the limits of quantification (LOQs) for the five target compounds in water samples were 0.5-1.2 ng/L and 1.4-4.0 ng/L, respectively. The recoveries of spiked water samples were 87.85%-102.34% with good repeatability and reproducibility (RSD < 5%, n = 3) for all the target compounds. Finally, the validated method was applied to analysis the representative UV filters in water samples collected from a wastewater treatment plant in Kunming city of Yunnan province.