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Sample records for rapid gas chromatographic

  1. A technique for rapid source apportionment applied to ambient organic aerosol measurements from a thermal desorption aerosol gas chromatograph (TAG

    Y. Zhang

    2016-11-01

    Full Text Available We present a rapid method for apportioning the sources of atmospheric organic aerosol composition measured by gas chromatography–mass spectrometry methods. Here, we specifically apply this new analysis method to data acquired on a thermal desorption aerosol gas chromatograph (TAG system. Gas chromatograms are divided by retention time into evenly spaced bins, within which the mass spectra are summed. A previous chromatogram binning method was introduced for the purpose of chromatogram structure deconvolution (e.g., major compound classes (Zhang et al., 2014. Here we extend the method development for the specific purpose of determining aerosol samples' sources. Chromatogram bins are arranged into an input data matrix for positive matrix factorization (PMF, where the sample number is the row dimension and the mass-spectra-resolved eluting time intervals (bins are the column dimension. Then two-dimensional PMF can effectively do three-dimensional factorization on the three-dimensional TAG mass spectra data. The retention time shift of the chromatogram is corrected by applying the median values of the different peaks' shifts. Bin width affects chemical resolution but does not affect PMF retrieval of the sources' time variations for low-factor solutions. A bin width smaller than the maximum retention shift among all samples requires retention time shift correction. A six-factor PMF comparison among aerosol mass spectrometry (AMS, TAG binning, and conventional TAG compound integration methods shows that the TAG binning method performs similarly to the integration method. However, the new binning method incorporates the entirety of the data set and requires significantly less pre-processing of the data than conventional single compound identification and integration. In addition, while a fraction of the most oxygenated aerosol does not elute through an underivatized TAG analysis, the TAG binning method does have the ability to achieve molecular level

  2. Dual liquid and gas chromatograph system

    Gay, D.D.

    A chromatographic system is described that utilizes one detection system for gas chromatographic and micro-liquid chromatographic determinations. The detection system is a direct-current, atmospheric-pressure, helium plasma emission spectrometer. The detector utilizes a nontransparent plasma source unit which contains the plasma region and two side-arms which receive effluents from the micro-liquid chromatograph and the gas chromatograph. The dual nature of this chromatographic system offers: (1) extreme flexibility in the samples to be examined; (2) extreme low sensitivity; (3) element selectivity; (4) long-term stability; (5) direct correlation of data from the liquid and gas samples; (6) simpler operation than with individual liquid and gas chromatographs, each with different detection systems; and (7) cheaper than a commercial liquid chromatograph and a gas chromatograph.

  3. A gas/liquid chromatographic-mass spectrometric method for the rapid screening of 250 pesticides in aqueous matrices

    Chandramouli, B.; Harvan, D.; Brittain, S.; Hass, R. [Eno River Labs, LLC. Durham, NC (United States)

    2004-09-15

    Pesticide residues in food present a potentially serious and significant cause for concern. Many pesticides have been associated with significant health effects to the nervous and endocrine systems and some have been deemed carcinogenic. There are many well-established techniques for pesticide analysis. However, commercial pesticide methods have traditionally only been available for specific pesticide families, such as chlorinated pesticides or herbicides, and at detection limits ranging from 0.05 ppb to 1 ppm in aqueous matrices. Techniques that can quickly screen for the presence/absence of pesticide residues in food matrices are critical in ensuring the safety of food and water. This paper outlines a combined Gas Chromatographic-High Resolution Mass Spectrometric (GC-HRMS) and Liquid Chromatographic Tandem Mass Spectrometric (LC-MS/MS) screening assay for 250 pesticides that was developed for use in water, and soda samples at screening levels ranging from 0.1-5 ppb. The pesticides selected have been identified by the European Union as being of concern and the target of possible legislation. The list encompasses a variety of pesticide classes and compound groupings.

  4. Rapid and simple clean-up and derivatizaton procedure for the gas chromatographic determination of acidic drugs in plasma

    Roseboom, H.; Hulshoff, A.

    1979-01-01

    A rapid and simple clean-up and derivatization procedure that can be generally applied to the gas chromatographie (GC) determination of acidic drugs of various chemical and therapeutic classes is described. The drugs are extracted from acidified plasma with chloroform containing 5% of isopropanol,

  5. A rapid gas chromatographic injection-port derivatization method for the tandem mass spectrometric determination of patulin and 5-hydroxymethylfurfural in fruit juices.

    Marsol-Vall, Alexis; Balcells, Mercè; Eras, Jordi; Canela-Garayoa, Ramon

    2016-07-01

    A novel method consisting of injection-port derivatization coupled to gas chromatography-tandem mass spectrometry is described. The method allows the rapid assessment of 5-hydroxymethylfurfural (HMF) and patulin content in apple and pear derivatives. The chromatographic separation of the compounds was achieved in a short chromatographic run (12.2min) suitable for routine controls of these compounds in the fruit juice industry. The optimal conditions for the injection-port derivatization were at 270°C, 0.5min purge-off, and a 1:2 sample:derivatization reagent ratio (v/v). These conditions represent an important saving in terms of derivatization reagent consumption and sample preparation time. Quality parameters were assessed for the target compounds, giving LOD of 0.7 and 1.6μg/kg and LOQ of 2 and 5μg/kg for patulin and HMF, respectively. These values are below the maximum patulin concentration in food products intended for infants and young children. Repeatability (%RSD n=5) was below 12% for both compounds. In addition, the method linearity ranged between 25 and 1000μg/kg and between 5 and 192μg/kg for HMF and patulin, respectively. Finally, the method was applied to study HMF and patulin content in various fruit juice samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. A Quantitative Gas Chromatographic Ethanol Determination.

    Leary, James J.

    1983-01-01

    Describes a gas chromatographic experiment for the quantitative determination of volume percent ethanol in water ethanol solutions. Background information, procedures, and typical results are included. Accuracy and precision of results are both on the order of two percent. (JN)

  7. Optimization of the gas chromatographic separations

    Gasco Sanchez, L.

    1973-01-01

    A review and a critical study on the optimization of the gas chromatographic separations are made. After dealing with the fundamental gas chromatographic equations, some methods of expressing column performances are discussed: performance indices, performance parameters, resolution and effective plate number per unit time. This is completed with a comparative study on performances of various types of columns. Moreover, optimization methods for operating chromatographic conditions are extensively dealt with: as resolution optimization, separation time, and normalization techniques for the time of analysis in order to achieve the maximum resolution at constant time. Finally, some others non operating parameters such as: selectivity of stationary phases, column preparation and optimization methods by means of computers are studied. (Author) 68 refs

  8. GAS CHROMATOGRAPHIC AND SPECTROSCOPIC ANALYSIS OF ...

    Peroxyformic acid prepared in-situ was employed for epoxidation of canola oil in the presence of toluene. Gas chromatographic analysis of the product revealed the following species: C16:0; C18:0; C18:1; C18:2; C18:3; monoepoxy C18:0; monoepoxy C18:1; monoepoxy C18:2; diepoxy C18:0; diepoxy C18:1 and triepoxy ...

  9. A Small-Scale Low-Cost Gas Chromatograph

    Gros, Natasa; Vrtacnik, Margareta

    2005-01-01

    The design and application of a small-scale portable gas chromatograph for learning of the basic concepts of chromatography is described. The apparatus consists of two basic separable units, which includes a chromatographic unit and an electronic unit.

  10. A simple and rapid gas chromatographic method for the determination of dissolved deuterium and nitrogen in heavy water coolant of a nuclear reactor

    Nair, B.K.S.

    1976-01-01

    A known volume of a heavy water sample is equilibrated with a known volume of pure helium gas at atmospheric pressure in a sample tube. The dissolved gases evolve into the helium and distribute themselves between the gaseous and liquid phases according to their equilibrium partial pressures. These partial pressures of the gases in the equilibrium gas mixture are determined by analysing it gas-chromatographically. From these analytical data and the absorption coefficients of deuterium and nitrogen, their original concentrations in heavy water are calculated. Corrections for the increase in the total pressure of the gaseous phase owing to evolved gases are calculated and found to be negligible. Air contamination during sampling and analysis can be detected by the presence of the oxygen peak in the chromatogram and corrected for. The calculation is facilitated by programming it on an electronic calculator. The method is much simpler and faster than the vacuum method usually applied for this analysis. One determination can be completed in about an hour. The average deviation and standard deviation have been estimated at 0.19 ml/litre heavy water and 0.25 ml/litre heavy water respectively in deuterium, and 0.36 and 0.68 ml/litre in nitrogen. (author)

  11. Simple gas chromatographic method for furfural analysis.

    Gaspar, Elvira M S M; Lopes, João F

    2009-04-03

    A new, simple, gas chromatographic method was developed for the direct analysis of 5-hydroxymethylfurfural (5-HMF), 2-furfural (2-F) and 5-methylfurfural (5-MF) in liquid and water soluble foods, using direct immersion SPME coupled to GC-FID and/or GC-TOF-MS. The fiber (DVB/CAR/PDMS) conditions were optimized: pH effect, temperature, adsorption and desorption times. The method is simple and accurate (RSDfurfurals will contribute to characterise and quantify their presence in the human diet.

  12. The gas-chromatographic and gas-chromatographic-mass-spectrometric identification of halogen-containing organic compounds

    Gidaspov, B. V.; Zenkevich, I. G.; Rodin, A. A.

    1989-09-01

    The problem of identifying halogen-containing organic compounds in their gas-chromatographic and gas-chromatographic-mass-spectrometric (GC-MS) determination in different materials has been examined. Particular attention has been paid not to the complete characterisation of methods for carrying out this analysis but to the most important problem of increasing the selectivity at the stages of sampling, separation, and interpretation of the gas-chromatographic and GC-MS information. The bibliography contains 292 references.

  13. Gas-Chromatographic Determination Of Water In Freon PCA

    Melton, Donald M.

    1994-01-01

    Gas-chromatographic apparatus measures small concentrations of water in specimens of Freon PCA. Testing by use of apparatus faster and provides greater protection against accidental contamination of specimens by water in testing environment. Automated for unattended operation. Also used to measure water contents of materials, other than Freon PCA. Innovation extended to development of purgeable sampling accessory for gas chromatographs.

  14. On-line gas chromatographic analysis of airborne particles

    Hering, Susanne V [Berkeley, CA; Goldstein, Allen H [Orinda, CA

    2012-01-03

    A method and apparatus for the in-situ, chemical analysis of an aerosol. The method may include the steps of: collecting an aerosol; thermally desorbing the aerosol into a carrier gas to provide desorbed aerosol material; transporting the desorbed aerosol material onto the head of a gas chromatography column; analyzing the aerosol material using a gas chromatograph, and quantizing the aerosol material as it evolves from the gas chromatography column. The apparatus includes a collection and thermal desorption cell, a gas chromatograph including a gas chromatography column, heated transport lines coupling the cell and the column; and a quantization detector for aerosol material evolving from the gas chromatography column.

  15. Rapid and selective derivatizatin method for the nitrogen-sensitive detection of carboxylic acids in biological fluids prior to gas chromatographic analysis

    Lingeman, H.; Haan, H.B.P.; Hulshoff, A.

    1984-01-01

    A rapid and selective derivatization procedure is described for the pre-column labelling of carboxylic acids with a nitrogen-containing label. The carboxylic acid function is activated with 2-bromo-1-methylpyridinium iodide and the activated carboxylic acid function reacts with a primary or a

  16. Gas-chromatographic separation of hydrogen isotopic mixtures

    Preda, Anisoara; Bidica, Nicolae

    2005-01-01

    Full text: Gas chromatographic separation of hydrogen isotopes have been reported in the literature since late of 1950's. Gas chromatography is primarily an analytical method, but because of its properties it may be used in many other fields with excellent results. A simple method is proposed for the gas-chromatographic analysis of complex gas mixtures containing hydrogen isotopes; the method is based on the substantial difference in the thermal conductivity of these isotopes. One of the main disadvantages of the conventional gas chromatography is the long retention times required for the analysis of hydrogen gas mixtures while the column is operated at very low temperature. The method described in this paper was based on using a capillary molecular sieve 5A column operated for this kind of separation at 173 K. The carrier gas was Ne and the detector was TCD. In the paper chromatograms for various carrier flow rates and various hydrogen isotope mixtures are presented. (authors)

  17. Evaluation of pesticide adsorption in gas chromatographic injector and column

    Gevany Paulino de Pinho

    2012-01-01

    Full Text Available Components in complex matrices can cause variations in chromatographic response during analysis of pesticides by gas chromatography. These variations are related to the competition between analytes and matrix components for adsorption sites in the chromatographic system. The capacity of the pesticides chlorpyrifos and deltamethrin to be adsorbed in the injector and chromatographic column was evaluated by constructing three isotherms and changing the column heating rate to 10 and 30 ºC min-1. By using ANCOVA to compare the slope of calibration graphs, results showed that the higher the injector temperature (310 ºC the lower the pesticide adsorption. Also, deltamethrin influenced the adsorption of chlorpyrifos on the column chromatographic.

  18. Gas chromatographic analysis of volatiles in fluid and gas inclusions

    Andrawes, F.; Holzer, G.; Roedder, E.; Gibson, E.K.; Oro, John

    1984-01-01

    Most geological samples and some synthetic materials contain fluid inclusions. These inclusions preserve for us tiny samples of the liquid and/or the gas phase that was present during formation, although in some cases they may have undergone significant changes from the original material. Studies of the current composition of the inclusions provide data on both the original composition and the change since trapping.These inclusions are seldom larger than 1 millimeter in diameter. The composition varies from a single major compound (e.g., water) in a single phase to a very complex mixture in one or more phases. The concentration of some of the compounds present may be at trace levels.We present here some analyses of inclusions in a variety of geological samples, including diamonds. We used a sample crusher and a gas chromatography—mass spectrometry (GC—MS) system to analyze for organic and inorganic volatiles present as major to trace constituents in inclusions. The crusher is a hardened stainless-steel piston cylinder apparatus with tungsten carbide crusing surfaces, and is operated in a pure helium atmosphere at a controlled temperature.Samples ranging from 1 mg to 1 g were crushed and the released volatiles were analyzed using multi-chromatographic columns and detectors, including the sensitive helium ionization detector. Identification of the GC peaks was carried out by GC—MS. This combination of procedures has been shown to provide geochemically useful information on the process involved in the history of the samples analyzed.

  19. A rapid, solid phase extraction (SPE technique for the extraction and gas chromatographic determination lindane pesticide residue in tissue and milk

    Yuningsih

    2006-03-01

    Full Text Available Organochlorine pesticide contamination in feed can cause residue in animal product (tissue and milk, so its become a problem in food safety. Solid phase extraction (SPE has been carried out for determination organochlorine pesticide residues in food animal production. The technique was rapid, not costly and produce limited amount of hazardous-waste. Samples were homogenized with acetonitrile trough cartridge C18, eluted in fluorocyl column with 2% ether-petroleum or acetonitrile fortissue and milk samples respectively. The recoveries of tissue sample by addition lindane standard solution: 0.50 and 1.00 μg are 85.10 and 103.10% respectively, while that of milk with the addition of 0.50, 1.00 and 1.50 μg are 83.80, 88.69 and 91.24% respectively. Three replicates were carried out for every sample. According of validation criteria of FAO/IAEA the recovery for analysis of pesticide residues was 70-110%. Therefore, the method is applicable.

  20. Gas chromatographic column for the Viking 1975 molecular analysis experiment

    Novotny, M.; Hayes, J. M.; Bruner, F.; Simmonds, P. G.

    1975-01-01

    A gas chromatographic column has been developed for use in the remote analysis of the Martian surface. The column, which utilizes a liquid-modified organic adsorbent (Tenax) as the stationary phase, provides efficient transmission and resolution of nanogram quantities of organic materials in the presence of millionfold excesses of water and carbon dioxide.

  1. Gas chromatographic determination of impurities of inorganic compounds

    Drugov, Yu.S.

    1985-01-01

    Methods of concentration, separation, detection in gas chromatographic determination of impurities of inorganic compounds including low-boiling gases, reactive gases, organometallic compounds, free metals, anions, etc. are reviewed. Methods of reaction gas chromatography for determining reactive gases, water, anions, metal chelates are considered in detail as well as methods of reaction-sorption concentration and reaction gas extraction. The application of gas chromatograpny ior anaiysis of water and atmosphere contamination, for determination of impurities in highly pure solid substances and gases is described

  2. Mars Solar Balloon Landed Gas Chromatograph Mass Spectrometer

    Mahaffy, P.; Harpold, D.; Niemann, H.; Atreya, S.; Gorevan, S.; Israel, G.; Bertaux, J. L.; Jones, J.; Owen, T.; Raulin, F.

    1999-01-01

    A Mars surface lander Gas Chromatograph Mass Spectrometer (GCMS) is described to measure the chemical composition of abundant and trace volatile species and isotope ratios for noble gases and other elements. These measurements are relevant to the study of atmospheric evolution and past climatic conditions. A Micromission plan is under study where a surface package including a miniaturized GCMS would be delivered to the surface by a solar heated hot air balloon based system. The balloon system would be deployed about 8 km above the surface of Mars, wherein it would rapidly fill with Martian atmosphere and be heated quickly by the sun. The combined buoyancy and parachuting effects of the solar balloon result in a surface package impact of about 5 m/sec. After delivery of the package to the surface, the balloon would ascend to about 4 km altitude, with imaging and magnetometry data being taken for the remainder of the daylight hours as the balloon is blown with the Martian winds. Total atmospheric entry mass of this mission is estimated to be approximately 50 kg, and it can fit as an Ariane 5 piggyback payload. The GCMS would obtain samples directly from the atmosphere at the surface and also from gases evolved from solid phase material collected from well below the surface with a Sample Acquisition and Transport Mechanism (SATM). The experiment envisioned in the Mars Micromission described would obtain samples from a much greater depth of up to one meter below the surface, and would search for organic molecules trapped in ancient stratified layers well below the oxidized surface. Insitu instruments on upcoming NASA missions working in concert with remote sensing measurement techniques have the potential to provide a more detailed investigation of mineralogy and the extent of simple volatiles such as CO2 and H2O in surface and subsurface solid phase materials. Within the context of subsequent mission opportunities such as those provided by the Ariane 5 piggyback

  3. A Gas Chromatographic System for the Detection of Ethylene Gas Using Ambient Air as a Carrier Gas.

    Zaidi, Nayyer Abbas; Tahir, Muhammad Waseem; Vellekoop, Michael J; Lang, Walter

    2017-10-07

    Ethylene gas is a naturally occurring gas that has an influence on the shelf life of fruit during their transportation in cargo ships. An unintentional exposure of ethylene gas during transportation results in a loss of fruit. A gas chromatographic system is presented here for the detection of ethylene gas. The gas chromatographic system was assembled using a preconcentrator, a printed 3D printed gas chromatographic column, a humidity sensor, solenoid valves, and an electrochemical ethylene gas sensor. Ambient air was used as a carrier gas in the gas chromatographic system. The flow rate was fixed to 10 sccm. It was generated through a mini-pump connected in series with a mass flow controller. The metal oxide gas sensor is discussed with its limitation in ambient air. The results show the chromatogram obtained from metal oxide gas sensor has low stability, drifts, and has uncertain peaks, while the chromatogram from the electrochemical sensor is stable and precise. Furthermore, ethylene gas measurements at higher ppb concentration and at lower ppb concentration were demonstrated with the electrochemical ethylene gas sensor. The system separates ethylene gas and humidity. The chromatograms obtained from the system are stable, and the results are 1.2% repeatable in five similar measurements. The statistical calculation of the gas chromatographic system shows that a concentration of 2.3 ppb of ethylene gas can be detected through this system.

  4. Gas chromatographic determination of calcium propionate added as preservative to bread.

    Lamkin, W M; Unruh, N C; Pomeranz, Y

    1987-01-01

    A simple and rapid gas chromatographic procedure was developed for determining low concentrations of propionate added as a preservative to bread. A bread sample to be analyzed was ground in a meat grinder with a 3 mm hole plate and finely divided by rubbing through a No. 8 sieve. The propionate was then extracted into 0.050M formic acid in a blender at low speed for 5 min, and an aliquot of a filtrate was analyzed directly by gas chromatography. Chromatographic separation was accomplished on a Carbopack C column coated with 0.3% (w/w) Carbowax 20M and 0.1% (w/w) phosphoric acid. Less than 0.2 ppm propionic acid could be detected in the aqueous extract. Over the range of 0.03-0.23% calcium propionate, average relative error was -1.20% with an average coefficient of variation of 2.02%.

  5. Gas chromatographic method fr determination of carbon in metallic uranium

    Nikol'skij, V.A.; Markov, V.K.; Evseeva, T.I.; Cherstvenkova, E.P.

    1983-01-01

    Gas chromatographic device to determine carbon in metal uranium is developed. Burnout unite, permitting to load in the burnout tube simultaneously quite a few (up to 20) weight amounts of materials to be burned is a characteristic feature of the device. As a result amendments for control experiment and determination limit are decreased. The time of a single determination is also reduced. Conditions of carbon burn out from metal uranium are studied and temperature and time of complete extraction of carbon in the form of dioxide from weight amount into gaseous phase are established

  6. Temperature Control of Gas Chromatograph Based on Switched Delayed System Techniques

    Xiao-Liang Wang

    2014-01-01

    Full Text Available We address the temperature control problem of the gas chromatograph. We model the temperature control system of the gas chromatograph into a switched delayed system and analyze the stability by common Lyapunov functional technique. The PI controller parameters can be given based on the proposed linear matrix inequalities (LMIs condition and the designed controller can make the temperature of gas chromatograph track the reference signal asymptotically. An experiment is given to illustrate the effectiveness of the stability criterion.

  7. Gas chromatographic isolation technique for compound-specific radiocarbon analysis

    Uchida, M.; Kumamoto, Y.; Shibata, Y.; Yoneda, M.; Morita, M.; Kawamura, K.

    2002-01-01

    Full text: We present here a gas chromatographic isolation technique for the compound-specific radiocarbon analysis of biomarkers from the marine sediments. The biomarkers of fatty acids, hydrocarbon and sterols were isolated with enough amount for radiocarbon analysis using a preparative capillary gas chromatograph (PCGC) system. The PCGC systems used here is composed of an HP 6890 GC with FID, a cooled injection system (CIS, Gerstel, Germany), a zero-dead-volume effluent splitter, and a cryogenic preparative collection device (PFC, Gerstel). For AMS analysis, we need to separate and recover sufficient quantity of target individual compounds (>50 μgC). Yields of target compounds from C 14 n-alkanes to C 40 to C 30 n-alkanes and approximately that of 80% for higher molecular weights compounds more than C 30 n-alkanes. Compound specific radiocarbon analysis of organic compounds, as well as compound-specific stable isotope analysis, provide valuable information on the origins and carbon cycling in marine system. Above PCGC conditions, we applied compound-specific radiocarbon analysis to the marine sediments from western north Pacific, which showed the possibility of a useful chronology tool for estimating the age of sediment using organic matter in paleoceanographic study, in the area where enough amounts of planktonic foraminifera for radiocarbon analysis by accelerator mass spectrometry (AMS) are difficult to obtain due to dissolution of calcium carbonate. (author)

  8. Gas chromatographic measurement in water-steam circuits

    Zschetke, J.; Nieder, R.

    1984-01-01

    A gas chromatographic technique for measurements in water-steam circuits, which has been well known for many years, has been improved by design modifications. A new type of equipment developed for special measuring tasks on nuclear engineering plant also has a general application. To date measurements have been carried out on the ''Otto Hahn'' nuclear powered ship, on the KNK and AVR experimental nuclear power plants at Karlsruhe and Juelich respectively and on experimental boiler circuits. The measurements at the power plants were carried out under different operating conditions. In addition measurements during the alkali operating mode and during combined cycle operation were carried out on the AVR reactor. It has been possible to draw new conclusion from the many measurements undertaken. (orig.) [de

  9. Headspace gas chromatographic method for the measurement of difluoroethane in blood.

    Broussard, L A; Broussard, A; Pittman, T; Lafferty, D; Presley, L

    2001-01-01

    To develop a gas chromatographic assay for the analysis of difluoroethane, a volatile substance, in blood and to determine assay characteristics including linearity, limit of quantitation, precision, and specificity. Referral toxicology laboratory Difluoroethane, a colorless, odorless, highly flammable gas used as a refrigerant blend component and aerosol propellant, may be abused via inhalation. A headspace gas chromatographic procedure for the identification and quantitation of difluoroethane in blood is presented. A methanolic stock standard prepared from pure gaseous difluoroethane was used to prepare whole blood calibrators. Quantitation of difluoroethane was performed using a six-point calibration curve and an internal standard of 1-propanol. The assay is linear from 0 to 115 mg/L including a low calibrator at 4 mg/L, the limit of quantitation. Within-run coefficients of variation at mean concentrations of 13.8 mg/L and 38.5 mg/L were 5.8% and 6.8% respectively. Between-run coefficients of variation at mean concentrations of 15.9 mg/L and 45.7 mg/L were 13.4% and 9.8% respectively. Several volatile substances were tested as potential interfering compounds with propane having a retention time identical to that of difluoroethane. This method requires minimal sample preparation, is rapid and reproducible, can be modified for the quantitation of other volatiles, and could be automated using an automatic sampler/injector system.

  10. Rapid and sensitive determination of deuterium concentration by gas chromatography

    Takahashi, Tomiki; Ohokoshi, Sumio; Shinriki, Nariko; Sato, Toshio

    1984-01-01

    Gas chromatographic determination of hydrogen isotopes D 2 and HD has hitherto been carried out with a molecular sieve column kept at -195 0 C under the H 2 carrier gas. However, the amount of D 2 in hydrogen gas containing low HD concentration of less than 5 % can be practically neglected judging from the equilibrium constant of H 2 -D 2 exchange reaction. Therefore, there is no need to separate HD from D 2 . As an improvement, in this paper, the gas chromatographic determination of HD in low concentration ( 2 as a carrier gas enabled us to enhance the cell current of TCD drastically, hence gave rise to high sensitivity of HD detection. The limit of determination of the concentration of HD was 0.01%. In the case of the higher concentration (>5%) of HD in hydrogen gas, D 2 and HD have been separated and determined by the method described above, but this method takes more than ten minutes. Therefore, we designed a new gas chromatographic analysis of the HD-D 2 mixture with an activated alumina column at -195 0 C under the H 2 carrier gas (330 ml/min). The advantages of this method are in (1) rapid analysis (in 1 min), (2) no need of the rigid activation temperature ((110--250) 0 C), (3) no change of the relative molar sensitivity of HD to D 2 at the various flow rates of H 2 carrier gas ((100--300)ml/min). (author)

  11. Characterisation of wax works of art by gas chromatographic procedures.

    Regert, M; Langlois, J; Colinart, S

    2005-10-14

    To identify the various natural and synthetic substances used by sculptors at the end of the 19th century, several contemporary reference samples were investigated by high temperature gas chromatography (HT GC) and HT GC-MS. Using specific chromatographic conditions and minimising sample preparation, we could separate, detect and identify a wide range of biomolecular markers covering a great variety of molecular weights and volatilities, with a minimum amount of sample, in a single run. Beeswax, spermaceti, carnauba, candellila and Japan waxes as well as pine resin derivatives, animal fats, paraffin, ozokerite and stearin, used as additives in wax works of art, were chemically investigated. In the case of low volatile compounds, transbutylation was performed. The structure of long-chain esters of spermaceti was elucidated for the first time by HT GC-MS analysis. Such a method was then carried out on 10 samples collected on a statuette of Junon by Antoine-Louis Barye (Louvre Museum, Paris, France) and on a sculpture by Aimé-Jules Dalou (Musée de la Révolution Française, Vizille, France). The analytical results obtained provide new data on the complex recipes elaborated by sculptors at the end of the 19th century.

  12. Recent Advances in Water Analysis with Gas Chromatograph Mass Spectrometers

    MacAskill, John A.; Tsikata, Edem

    2014-01-01

    We report on progress made in developing a water sampling system for detection and analysis of volatile organic compounds in water with a gas chromatograph mass spectrometer (GCMS). Two approaches are described herein. The first approach uses a custom water pre-concentrator for performing trap and purge of VOCs from water. The second approach uses a custom micro-volume, split-splitless injector that is compatible with air and water. These water sampling systems will enable a single GC-based instrument to analyze air and water samples for VOC content. As reduced mass, volume, and power is crucial for long-duration, manned space-exploration, these water sampling systems will demonstrate the ability of a GCMS to monitor both air and water quality of the astronaut environment, thereby reducing the amount of required instrumentation for long duration habitation. Laboratory prototypes of these water sampling systems have been constructed and tested with a quadrupole ion trap mass spectrometer as well as a thermal conductivity detector. Presented herein are details of these water sampling system with preliminary test results.

  13. The behaviour of radionuclides in gas adsorption chromatographic processes with superimposed chemical reactions (chlorides)

    Eichler, B.

    1996-01-01

    Thermochemical relationships are derived describing the gas adsorption chromatographic transport of carrier-free radionuclides. Especially, complex adsorption processes such as dissociative, associative and substitutive adsorption are dealt with. The comparison of experimental with calculated data allows the determination of the type of adsorption reaction, which is the basis of the respective gas chromatographic process. The behaviour of carrier-free radionuclides of elements Pu, Ce, Ru, Co and Cr in thermochromatographic experiments with chlorinating carrier gases can be described as dissociative adsorption of chlorides in higher oxidation states. The gas adsorption chromatographic transport of Zr with oxygen and chlorine containing carrier gas is shown to be a substitutive adsorption process. The consequences of superimposed chemical reactions on the interpretation of results and the conception of gas adsorption chromatographic experiments with carrier-free radionuclides in isothermal columns and in temperature gradient tubes is discussed. (orig.)

  14. Rapid differentiation of rocky mountain spotted fever from chickenpox, measles, and enterovirus infections and bacterial meningitis by frequency-pulsed electron capture gas-liquid chromatographic analysis of sera.

    Brooks, J B; McDade, J E; Alley, C C

    1981-01-01

    Normal sera and sera from patients with Rocky Mountain spotted fever, chickenpox, enterovirus infections, measles, and Neisseria meningitidis infections were extracted with organic solvents under acidic and basic conditions and then derivatized with trichloroethanol or heptafluorobutyric anhydride-ethanol to form electron-capturing derivatives of organic acids, alcohols, and amines. The derivatives were analyzed by frequency-pulsed electron capture gas-liquid chromatography (FPEC-GLC). There were unique differences in the FPEC-GLC profiles of sera obtained from patients with these respective diseases. With Rocky Mountain spotted fever patients, typical profiles were detected as early as 1 day after onset of disease and before antibody could be detected in the serum. Rapid diagnosis of Rocky Mountain spotted fever by FPEC-GLC could permit early and effective therapy, thus preventing many deaths from this disease. PMID:7276147

  15. A Gas Chromatographic Method for the Determination of Bicarbonate and Dissolved Gases

    John H. Loughrin

    2017-11-01

    Full Text Available A gas chromatographic method for the rapid determination of aqueous carbon dioxide and its speciation into solvated carbon dioxide and bicarbonate is presented. One-half mL samples are injected through a rubber septum into 20-mL vials that are filled with 9.5 mL of 0.1 N HCl. A one mL portion of the headspace is withdrawn and injected onto a gas chromatograph equipped with a thermal conductivity detector. Using the dimensionless Henry's constant for carbon dioxide and an adaptation of the Henderson-Hasselbalch equation, carbon dioxide in the samples can be categorized among solvated, bicarbonate, and carbonate forms. Natural water samples as well as wastewater from a municipal sewage treatment plant and a swine rearing operation were analyzed by this method and the results compared favorably to those obtained by titration. Samples stored for up to 5 weeks showed no significant changes in carbon dioxide concentrations. In addition, using flame ionization and electron capture detectors, methane and nitrous oxide concentrations in the samples were also measured.

  16. Gas chromatographic analysis of simmondsins and simmondsin ferulates in jojoba meal.

    Van Boven, M; Holser, R; Cokelaere, M; Flo, G; Decuypere, E

    2000-09-01

    A capillary gas chromatographic method was developed for the simultaneous determination of simmondsins and simmondsin ferulates in jojoba meal, in detoxified jojoba meal, in jojoba meal extracts, and in animal food mixtures.

  17. Separation and determination of high-carbon alcohols using method of column chromatographic and gas-chromatographic analysis

    Kang Zhongrong; Li Biping; Zeng Yongchang

    1988-01-01

    This paper describes the separation and determination of high-carbon alcohols from amine extractant by using the method of column chromatography of aluminium oxide and gas-chromatographic analysis. The total conent of high-carbon alcohols is determined by the method of column chromatography, while the components of the high-carbon alcohols and their relative contents are determined by the method of gas-chromatography. A simple reliable and practical method is provided for the analysis of high-carbon alcohol from the amine extractant in this paper

  18. Gas chromatographic determination of yohimbine in commercial yohimbe products.

    Betz, J M; White, K D; der Marderosian, A H

    1995-01-01

    The bark of Pausinystalia yohimbe [K. Schumann] Pierre (Rubiaceae), long valued as an aphrodisiac in West Africa, recently has been promoted in the United States as a dietary supplement alternative to anabolic steroids for enhancement of athletic performance. As the number of yohimbe products on the retail market increases, concerns about their safety are raised because of the reported toxicity of yohimbine (the major alkaloid of the plant). Although plant materials are usually identified microscopically, we were unable to identify them in many of the products, because as their labels indicated, the products were mixtures of various botanicals or were bark extracts and contained little or no plant material. A method for extraction and capillary gas chromatographic (GC) separation of the alkaloids of P. yohimbe was, therefore, developed and used to analyze a number of commercial yohimbe products. The method involved solvent extraction and partitioning in chloroform-water followed by separation on a methyl silicone capillary GC column (N-P detection). Comparisons of chromatograms of extracts of authentic bark with those of commercial products indicated that, although many products contained measurable quantities of the alkaloid yohimbine, they were largely devoid of the other alkaloids previously reported in this species. Concentrations of yohimbine in the commercial products ranged from < 0.1 to 489 ppm, compared with 7089 ppm in the authentic material. Authentic bark has been reported to contain up to 6% total alkaloids, 10-15% of which are yohimbine. The possible presence of undeclared diluents in the products was indicated by peaks in product chromatograms but not in those of authentic bark.

  19. Direct coupling of a dense (supercritical) gas chromatograph to a mass spectrometer using a supersonic molecular beam interface

    Randall, L.G.; Wahrhaftig, A.L.

    1981-01-01

    A detecting mass spectrometer has been successfully coupled to a dense gas (supercritical fluid) chromatograph to produce an instrument (DGC/MS) that may be an alternative to high performance liquid chromatograph/mass spectrometer instruments (HPLC/MS) and gas chromatograph/mass spectrometer instruments (GC/MS) for analysis of involatile and/or thermally labile compounds. The mobile phase in DGC is a gas held at temperatures above the critical temperature and at pressures sufficient to obtain nearly liquid-like densities. DGC combines advantages of GC and HPLC: rapid separations, moderate operating temperatures, and analysis of involatile compounds. An advantage unique to DGC is the solvent power dependence upon pressure. While several groups have studied DGC, its development has been limited by the lack of a sensitive and selective detector. Hence, work has been directed towards the design and construction of a DGC/MS resulting in a trial instrument capable of chromatographic pressures of at least 300 atm and temperatures from 10 0 to 60 0 C. The DGC/MS coupling has been accomplished by the use of a supersonic molecular beam interface. This application of molecular beam formation appears to be unique in its requirements of a large pressure ratio (approx.10 8 ), low flow rates, and low final pressures. The authors outline characteristics of supersonic jets and molecular beams pertinent to the design of such an instrument. The interface which uses pumping speeds of 2400 and 1200 l/s in the beam forming chambers is described in detail, while the other components: the detecting mass spectrometer, the dense gas supply, and the DGC: are briefly described. Preliminary work with this instrument has established the feasibility of DGC/MS as an analytical technique and further development is recommended

  20. Research on technology of online gas chromatograph for SF6 decomposition products

    Li, L.; Fan, X. P.; Zhou, Y. Y.; Tang, N.; Zou, Z. L.; Liu, M. Z.; Huang, G. J.

    2017-12-01

    Sulfur hexafluoride (SF6) decomposition products were qualitatively and quantitatively analyzed by several gas chromatographs in the laboratory. Test conditions and methods were selected and optimized to minimize and eliminate the SF6’ influences on detection of other trace components. The effective separation and detection of selected characteristic gases were achieved. And by comparison among different types of gas chromatograph, it was found that GPTR-S101 can effectively separate and detect SF6 decomposition products and has best the best detection limit and sensitivity. On the basis of GPTR-S101, online gas chromatograph for SF6decomposition products (GPTR-S201) was developed. It lays the foundation for further online monitoring and diagnosis of SF6.

  1. Development and evaluation of a gas chromatographic method for the determination of triazine herbicides in natural water samples

    Steinheimer, T.R.; Brooks, M.G.

    1984-01-01

    A multi-residue method is described for the determination of triazine herbicides in natural water samples. The technique uses solvent extraction followed by gas chromatographic separation and detection employing nitrogen-selective devices. Seven compounds can be determined simultaneously at a nominal detection limit of 0.1 ??g/L in a 1-litre sample. Three different natural water samples were used for error analysis via evaluation of recovery efficiencies and estimation of overall method precision. As an alternative to liquid-liquid partition (solvent extraction) for removal of compounds of interest from water, solid-phase extraction (SPE) techniques employing chromatographic grade silicas with chemically modified surfaces have been examined. SPE is found to provide rapid and efficient concentration with quantitative recovery of some triazine herbicides from natural water samples. Concentration factors of 500 to 1000 times are obtained readily by the SPE technique.A multi-residue method is described for the determination of triazine herbicides in natural water samples. The technique uses solvent extraction followed by gas chromatographic separation and detection employing nitrogen-selective devices. Seven compounds can be determined simultaneously at a nominal detection limit of 0. 1 mu g/L in a 1-litre sample. As an alternative to liquid-liquid partition (solvent extraction) for removal of compounds of interest from water, solid-phase extraction (SPE) techniques employing chromatographic grade silicas with chemically modified surfaces have been examined. SPE is found to provide rapid and efficient concentration with quantitative recovery of some triazine herbicides from natural water samples. Concentration factors of 500 to 1000 times are obtained readily by the SPE technique.

  2. Determination of hexachlorocyclohexane pesticide residues in wool fat by a combined high-performance liquid chromatographic-gas-liquid chromatographic method

    Ali, S.L.

    1978-01-01

    Beta- and gamma-hexachlorocyclohexane residues were determined in twelve wool fat samples by using a combined high-performance liquid chromatographic (HPLC)-gas-liquid chromatographic (GLC) method. After extraction and chromatographic clean-up on a silca-gel column, the sample was further purified by HPLC on a reversed-phase C-18 column with methanol as the mobile phase. The final determination was effected by GLC with a 1-mCi nickel-63 electron-capture detector. The analytical method was checked by addition of carbon-14-labelled lindane and measurement of the radioactivity in a liquid scintillation counter. (Auth.)

  3. Measurement of water absorption capacity in wheat flour by a headspace gas chromatographic technique.

    Xie, Wei-Qi; Yu, Kong-Xian; Gong, Yi-Xian

    2018-04-17

    The purpose of this work is to introduce a new method for quantitatively analyzing water absorption capacity in wheat flour by a headspace gas chromatographic technique. This headspace gas chromatographic technique was based on measuring the water vapor released from a series of wheat flour samples with different contents of water addition. According to the different trends between the vapor and wheat flour phase before and after the water absorption capacity in wheat flour, a turning point (corresponding to water absorption capacity in wheat flour) can be obtained by fitting the data of the water gas chromatography peak area from different wheat flour samples. The data showed that the phase equilibrium in the vial can be achieved in 25 min at desired temperature (35°C). The relative standard deviation of the reaction headspace gas chromatographic technique in water absorption capacity determination was within 3.48%, the relative differences has been determined by comparing the water absorption capacity obtained from this new analytical technique with the data from the reference technique (i.e., the filtration method), which are less than 8.92%. The new headspace gas chromatographic method is automated, accurate and be a reliable tool for quantifying water absorption capacity in wheat flour in both laboratory research and mill applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Optimization of the gas chromatographic separations; Optimacion de las separaciones cromatograficas en fase gaseosa

    Gasco Sanchez, L

    1973-07-01

    A review and a critical study on the optimization of the gas chromatographic separations are made. After dealing with the fundamental gas chromatographic equations, some methods of expressing column performances are discussed: performance indices, performance parameters, resolution and effective plate number per unit time. This is completed with a comparative study on performances of various types of columns. Moreover, optimization methods for operating chromatographic conditions are extensively dealt with: as resolution optimization, separation time, and normalization techniques for the time of analysis in order to achieve the maximum resolution at constant time. Finally, some others non operating parameters such as: selectivity of stationary phases, column preparation and optimization methods by means of computers are studied. (Author) 68 refs.

  5. Large scale gas chromatographic demonstration system for hydrogen isotope separation

    Cheh, C.H.

    1988-01-01

    A large scale demonstration system was designed for a throughput of 3 mol/day equimolar mixture of H,D, and T. The demonstration system was assembled and an experimental program carried out. This project was funded by Kernforschungszentrum Karlsruhe, Canadian Fusion Fuel Technology Projects and Ontario Hydro Research Division. Several major design innovations were successfully implemented in the demonstration system and are discussed in detail. Many experiments were carried out in the demonstration system to study the performance of the system to separate hydrogen isotopes at high throughput. Various temperature programming schemes were tested, heart-cutting operation was evaluated, and very large (up to 138 NL/injection) samples were separated in the system. The results of the experiments showed that the specially designed column performed well as a chromatographic column and good separation could be achieved even when a 138 NL sample was injected

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

    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

  7. Pyrolysis gas chromatographic atomic emission detection for sediments, coals and other petrochemical precursors

    Seeley, J.A.; Zeng, Y.D.; Uden, P.C.; Eglinton, T.I.; Ericson, I. (Massachusetts University, Amherst, MA (USA). Dept. of Chemistry)

    1992-09-01

    On-line flash pyrolysis coupled to a capillary gas chromatograph for the characterization of marine sediments, coals and other heterogeneous solid samples is described. A helium microwave-induced plasma is used for chromatographic detection by atomic emission spectrometry. Simultaneous multi-element detection is achieved with a photodiode array detector. The optical path of the gas chromatographic atomic emission detector is purged with helium, allowing simultaneous, sensitive detection of atomic emission from sulfur 181 nm, phosphorous 186 nm, arsenic 189 nm, selenium 196 nm and carbon 193 nm. Several sediment and coal samples have been analysed for their carbon, nitrogen, sulfur, oxygen, phosphorous, arsenic and selenium content. Qualitative information indicating the occurrence and distribution of these elements in the samples can be used to gauge the relative stage of diagenetic evolution of the samples and provide information on their depositional environment. In some instances the chromatographic behaviour of the compounds produced upon pyrolysis is improved through on-line alkylation. This on-line derivatization is achieved by adding liquid reagents to the pyrolysis probe or by adding liquid reagents to the pyrolysis probe or by adding solid reagents either to the solid sample or by packing the reagent in the injection port of the chromatograph.

  8. Gas-chromatographic quantitative determination of argon in air samples, by elimination of oxigen

    Sofronie, E.

    1982-08-01

    A method of gas-chromatographic quantitative determination of argon in air samples, by elimination of oxygen, is presented. Experiments were carried out in a static system. Conditions for the application of the method in dynamic systems are specified. Sensibility of the method: 5 10 -4 cm 3 Ar per cm 3 of air. (author)

  9. Improvement of gas chromatographic analysis for organic acids and ...

    Yomi

    2010-08-27

    Aug 27, 2010 ... short retention time and fair recognition peak of the compounds were obtained under the ... GC for acid and solvent analysis from ABE fermentation ... FID was kept at 230°C. Nitrogen gas was used as a carrier gas at a.

  10. Simple gas chromatographic system for analysis of microbial respiratory gases

    Carle, G. C.

    1972-01-01

    Dual column ambient temperature system, consisting of pair of capillary columns, microbead thermistor detector and micro gas-sampling valve, is used in remote life-detection equipment for space experiments. Performance outweighs advantage gained by utilizing single-column systems to reduce weight, conserve carrier gas and operate at lower power levels.

  11. Acrylamide analysis in food by liquid chromatographic and gas chromatographic methods.

    Elbashir, Abdalla A; Omar, Mei M Ali; Ibrahim, Wan Aini Wan; Schmitz, Oliver J; Aboul-Enein, Hassan Y

    2014-01-01

    Acrylamide (AA) is a compound classified as carcinogenic to humans by the International Agency for Research on Cancer. It was first discovered to be present in certain heated processed food by the Swedish National Food Administration (SNFA) and University of Stockholm in early 2002. The major pathway for AA formation in food is the Maillard reaction between reducing sugar and the amino acid asparagine at high temperature. Since the discovery of AA's presence in food, many analytical methods have been developed for determination of AA contents in different food matrices. Also, several studies have been conducted to develop extraction procedures for AA from difficult food matrices. AA is a small, highly polar molecule, which makes its extraction and analysis challenging. Many articles and reviews have been published dealing with AA in food. The aim of the review is to discuss AA formation in food, the factors affecting AA formation and removal, AA exposure assessment, AA extraction and cleanup from food samples, and analytical methods used in AA determination, such as high-performance liquid chromatography (HPLC) and gas chromatography (GC). Special attention is given to sample extraction and cleanup procedures and analytical techniques used for AA determination.

  12. Pyrolysis-gas chromatographic method for kerogen typing

    Larter, S.R.; Douglas, A.G.

    1980-01-01

    The classification of kerogens according to their type and rank is important for the definition of any kerogen assemblage. Whereas optical methods of rank determination are well known, vitrinite reflectance and spore coloration being the most widely accepted chemical methods for typing kerogens are less developed. In this work we show that pyrograms, produced by pyrolyzing microgram quantities of solvent-extracted kerogens, enable not only their characterization in terms of a chromatographic fingerprint but also the production of a numerical type index determined as the ratio of m(+p)-xylene/n-octene (oct-1-ene) in the pyrogram. This index appears to be a close function of kerogen type. Type 3 kerogens (Tissot et al., 1974), including vitrinite, provide a high type index and have pyrolysates dominated by aromatic and phenolic compounds whereas type 1 kerogens provide an aliphatic-rich pyrolysate and consequently a low type index. The type index described here correlates well with microscopic and elemental analysis data and the pyrogram fingerprint provides an additional level of characterization not attainable with other current typing techniques.

  13. Evaluation of serpentine ore as a nuclear shielding material using gas chromatographic techniques

    Singh, B.N.; Unnikrishnan, E.K.; Kumar, Sangita D.

    2007-01-01

    Serpentine ore mixed with cement has been recognized as a candidate shielding material for use in nuclear reactors because of its many desirable properties. Therefore the assessment of serpentine ore for release of volatile gases during exposure to elevated temperatures, irradiation and changes in chemical composition, is essential. The present paper deals with the studies on the serpentine ores using gas chromatography and combustion gas chromatographic techniques. (author)

  14. Gas Chromatographic Determination of Fatty Acids in Oils with Regard to the Assessment of Fire Hazard

    Bartošová, Alica; Štefko, Tomáš

    2017-06-01

    The aim of the paper was to study and research the application of processing gas chromatographic method for the rapid and accurate determination of the composition of different types of oils, such as substances with the possibility of an adverse event spontaneous combustion or self-heating. Tendency to spontaneous combustion is chemically characterized mainly by the amount of unsaturated fatty acids, which have one or more double bonds in their molecule. Vegetable oils essentially consist of the following fatty acids: palmitic, stearic, oleic, linoleic, and linoleic. For the needs of assessment, the fire hazard must be known, in which the double bond is present, as well as their number in a molecule. As an analytical method, GCMS was used for determination of oils content. Three types of oil were used - rapeseed, sunflower, and coconut oil. Owing to the occurrence of linoleic acid C18:2 (49.8 wt.%) and oleic acid C18:1 (43.3 wt.%) with double bonds, sunflower oil is the most prone to self-heating. The coconut and rapeseed oils contain double bond FAME in lesser amount, and their propensity to self-heating is relatively low.

  15. Physicochemical, thin layer and gas-liquid chromatographic ...

    DELL

    2012-05-22

    May 22, 2012 ... PEG (3 m × 3 mm I. D.) was used for gas chromatography. Physicochemical analysis ... subjected to thin layer chromatography on plates (20 × 20 cm) having 0.25 mm thick silica gel ..... Headspace solid- phase microextraction ...

  16. Gas Chromatographic-Mass Spectrometric Analysis of Essential Oil ...

    Purpose: To analyze the essential oil composition of the flower of Jasminum officinale L. var. grandifloroum L. (Jasminum grandiflorum) by gas chromatography-mass spectrometry (GC-MS). Methods: The optimum GC-MS conditions used for the analysis were 250 oC inlet temperature, 150 oC MSD detector temperature, ...

  17. TBP degradation products. Separation and gas-chromatographic determination

    Kuada, T.A.; Alem, C.M.; Matsuda, H.T.; Araujo, B.F. de; Araujo, J.A de.

    1991-11-01

    A separation method for di butylphosphate, mono butylphosphate and phosphoric acid as degradation products in organic and aqueous streams of the process containing variable amounts of actinides and fission products is described. The products were separated by extraction and after methylation the final determination was carried out by gas chromatography. TPP was used as internal standard and 5 to 500 mg/L concentration range was determined with 1 to 10% deviation depending on the concentration of organo phosphates. (author)

  18. Rapid planar chromatographic analysis of 25 water-soluble dyes used as food additives.

    Morlock, Gertrud E; Oellig, Claudia

    2009-01-01

    A rapid planar chromatographic method for identification and quantification of 25 water-soluble dyes in food was developed. In a horizontal developing chamber, the chromatographic separation on silica gel 60F254 high-performance thin-layer chromatography plates took 12 min for 40 runs in parallel, using 8 mL ethyl acetate-methanol-water-acetic acid (65 + 23 + 11 + 1, v/v/v/v) mobile phase up to a migration distance of 50 mm. However, the total analysis time, inclusive of application and evaluation, took 60 min for 40 runs. Thus, the overall time/run can be calculated as 1.5 min with a solvent consumption of 200 microL. A sample throughput of 1000 runs/8 h day can be reached by switching between the working stations (application, development, and evaluation) in a 20 min interval, which triples the analysis throughput. Densitometry was performed by absorption measurement using the multiwavelength scan mode in the UV and visible ranges. Repeatabilities [relative standard deviation (RSD), 4 determinations] at the first or second calibration level showed precisions of mostly or = 0.9987) and RSD values ( or = 0.9996). If necessary for confirmation, online mass spectra were recorded within a minute.

  19. Adsorption and gas-chromatographic properties of tungsten selenide

    Gavrilova, T.B.; Kiselev, A.V.; Roshchina, T.M.

    1988-01-01

    Method of gas chromatography was used to investigate the surface properties of a series of tungsten selenide WSe 2 samples as well as to determine the role of geometrical and electronic structure of adsorbate molecules and their orientation with respect to the surface during adsorption on WSe 2 . Thermodynamic characteristics of hydrocarbon C 6 -C 10 adsorption at surface occupation close to the zero one were determined. Correlation of the values of thermodynamic characteristics of saturated and aromatic hydrocarbon adsorption enabled to refer WSe 2 to nonspecific adsorbents. It is noted that the main role during hydrocarbon adsorption on WSe 2 is played by nonpolar basic facets, occupied by selenium atoms

  20. Gas chromatographic analysis of extractive solvent in reprocessing plants

    Marlet, B.

    1984-01-01

    Operation of a reprocessing plant using the Purex process is recalled and analytical controls for optimum performance are specified. The aim of this thesis is the development of analytical methods using gas chromatography required to follow the evolution of the extraction solvent during spent fuel reprocessing. The solvent at different concentrations, is analysed along the reprocessing lines in organic or aqueous phases. Solvent degradation interferes with extraction and decomposition products are analysed. The solvent becomes less and less efficient, also it is distilled and quality is checked. Traces of solvent should also be checked in waste water. Analysis are made as simple as possible to facilitate handling of radioactive samples [fr

  1. Chromatographic measurement of hydrogen isotopic and permanent gas impurities in tritium

    Warner, D.K.; Kinard, C.; Bohl, D.C.

    1976-01-01

    This paper describes a gas chromatograph that was designed for dedicated analysis of hydrogen isotopic and permanent gas impurities in tritium and tritium-deuterium mixtures. The instrument that was developed substantially improved the accuracy and precision of hydrogen isotopic analysis in the 20 ppM to one mole percent range as compared with other analytical methods. Several unique design features of the instrument were required due to the radiation and isotopic exchange properties of the tritium in the samples; descriptions of these features are presented along with details of the complete chromatographic system. The experimental procedures used to calibrate the detector and statistically evaluate its performance are given, and the sources of analytical error are cited. The limitations of the present system are also discussed

  2. Detection of irradiated fruits and vegetables by gas-chromatographic methods and electron spin-resonance

    Farag, S.E.A. (National Centre for Radiation Research and Technology, Cairo (Egypt))

    1993-01-01

    Gas chromatographic methods detected some hydrocarbons esp. 17:1, 16:2, 15:0 and 14:1 in irradiated, Avocado, Papaya, Mangoes with 0.75, 1.5, 3.0 kGy and Apricot with 0.5 and 3.0 kGy. The detection of hydrocarbons was clearly at high doses but the low doses need more sensitive conditions using Liquid-Liquid-Gas chromatographic method as used here. Using Electron Spin-Resonance, produce a specific signal from irradiated onion (dried leaves) as well as apricot (hard coat of kernels) after some weeks of irradiation process but not clear with the other foodstuffs. (orig.)

  3. Diagnosis of rinderpest in Tanzania by a rapid chromatographic strip-test.

    Wambura, P N; Moshy, D W; Mbise, A N; Mollel, G O; Taylor, W P; Anderson, J; Bruning, A

    2000-06-01

    A simple chromatographic strip-test based on Clearview technology, is under development as a pen-side test for the detection of rinderpest antigen in eye swabs taken from cattle in the field. An outbreak of rinderpest occurred in the northern zone of Tanzania from late February to June 1997. The affected cattle exhibited very mild clinical signs, which made clinical diagnosis difficult. One hundred and seven eye swabs were collected from cattle suspected of infection with rinderpest. These were tested in the field using a prototype of the pen-side test and 13 (12.15%) of the samples were found to be positive for the presence of rinderpest antigen. These were confirmed by ICE. The positive cases were predominantly found in the Ngorongoro district. This demonstrates the usefulness of such a simple, rapid pen-side diagnostic assay, particularly when clinically 'mild' strains of rinderpest are present.

  4. Multidimensional High-Resolution Gas Chromatographic Investigations of Hydrocarbon Fuels and Various Turbine Engine Fuel Precursors.

    1985-08-01

    time were spurious transits observed during the recording of the chromatographic output data. *Packaged gas purification filters supplied by Alltech ... Alltech ) that were needed for these unusual installations. When the column diameters were small and of comparable size, the assembly attach- ments at...into an MDGC system has definite advantages as separations can be made faster and with greater detectability. However, specific precautions must be

  5. The adaptive internet application for interpretation of the transformer oil gas chromatographic analysis results

    Polužanski Vladimir

    2015-01-01

    Full Text Available This paper describes an adaptive Internet application for the interpretation of the transformer oil gas chromatographic analysis results. The first version of the application is developed by following an evolutionary software development concept. The most important software development risks and the appropriate solutions are described. An open-source web framework named Bootstrap is used for an application implementation. The application is developed by using ASP.NET and MS SQL server.

  6. Use of the Keele injector for sample introduction for gas chromatographic analysis of vinclozolin in lettuces.

    Shim, J H; Lee, Y S; Kim, M R; Lee, C J; Kim, I S

    2003-10-10

    We examined a Keele injector for sample introduction for gas chromatographic analysis of vinclozolin treated in lettuces. Samples in milligram quantity were introduced into a glass tube in a Keele injector at a gas chromatograph injection port. The glass tube was then crushed to allow the sample to carry onto a capillary column in a normal manner. The standard calibration curve for quantitative detection of vinclozolin was obtained by determining vinclozolin spiked in samples at variable concentrations. The calibration curve showed a linear response to vinclozolin ranging from 0.05 to 1.0 microg/g, giving a slope value of 174.8, the y-intercept value of -2.8146 and the mean r2-value of 0.9994. Limit of quantification for vinclozolin was 0.05 microg/g by this method, comparable to 0.01 microg/g by a normal injector. When samples treated previously with vinclozolin were determined by the Keele injector, vinclozolin was found to be about 30% lower as compared to a normal method, suggesting about 70% recovery of the spiked vinclozolin by the Keele injector. From these results, the Keele injector was suggested to be potential for sample introduction in gas chromatographic analysis of vinclozolin in lettuce samples.

  7. Gas-liquid chromatographic determination of resmethrin in corn, cornmeal, flour, and wheat.

    Simonaitis, R A; Cail, R S

    1975-09-01

    A gas-liquid chromatographic (GLC) method was developed for the determination of residues of resmethrin ((5-benzyl-3-furyl)methyl cis-trans-(+/-)-2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylate) in corn, cornmeal, flour, and wheat. The commodity, fortified with resmethrin, was extracted by tumbling with pentane and transferred to acetonitrile, the fat was partitioned off, and the sample was chromatographed with 3% ethyl acetate in pentane on Florisil containing 0.5% water. The resmethrin residue was determined by GLC with a flame ionization detector. The results were compared with known standards that had undergone the same cleanup procedures. The method was sensitive to concentrations of resmethrin to 0.2 ppm, recoveries averaged 83%, and reproducibility was good.

  8. New method for evaluating irreversible adsorption and stationary phase bleed in gas chromatographic capillary columns.

    Wright, Bob W; Wright, Cherylyn W

    2012-10-26

    A novel method is described for the evaluation of irreversible adsorption and column bleed in gas chromatographic (GC) columns using a tandem GC approach. This work specifically determined the degree of irreversible adsorption behavior of specific sulfur and phosphorous containing test probe compounds at levels ranging from approximately 50 picograms (pg) to 1 nanogram (ng) on selected gas chromatographic columns. This method does not replace existing evaluation methods that characterize reversible adsorption but provides an additional tool. The test compounds were selected due to their ease of adsorption and their importance in the specific trace analytical detection methodology being developed. Replicate chromatographic columns with 5% phenylmethylpolysiloxane (PMS), polyethylene glycol (wax), trifluoropropylpolysiloxane (TFP), or 78% cyanopropylpolysiloxane stationary phases from a variety of vendors were evaluated. As expected, the results demonstrate that the different chromatographic phases exhibit differing degrees of irreversible adsorption behavior. The results also indicate that all manufacturers do not produce equally inert columns nor are columns from a given manufacturer identical. The wax-coated columns for the test probes used were more inert as a group than 5% PMS coated columns, and they were more reproducibly manufactured. Both TFP and 78% cyanopropylpolysiloxane columns displayed superior inertness to the test compounds compared to either 5% PMS- or wax-coated columns. Irreversible adsorption behavior was characterized for a limited range of stationary phase film thicknesses. In addition, the method was shown effective for characterizing column bleed and methods to remove bleed components. This method is useful in screening columns for demanding applications and to obtain diagnostic information related to improved preparation methods. Copyright © 2012 Elsevier B.V. All rights reserved.

  9. Covalently coating dextran on macroporous polyglycidyl methacrylate microsphere enabled rapid protein chromatographic separation

    Zhang, Rongyue; Li, Qiang; Li, Juan; Zhou, Weiqing; Ye, Peili; Gao, Yang; Ma, Guanghui, E-mail: ghma@home.ipe.ac.cn; Su, Zhiguo

    2012-12-01

    Protein denaturation and nonspecific adsorption on polymer media as a chromatographic support have been a problem which needs to be overcome. Macroporous poly(glycidyl methacrylate-divinylbezene) (PGMA-DVB) microspheres prepared in this study were firstly covalently coated with dextran through a three-step method. The dextran was firstly adsorbed onto the microspheres and then covalently bound to the PGMA-DVB microsphere through ether bonds which were formed by hydroxyl group reacting with epoxy group at the presence of 4-(Dimethylamino) pyridine. Finally, the coating dextran layer was crosslinked by ethylene glycol diglycidyl ether to form the continuous network coating. The coated microspheres were characterized by Fourier transform infrared spectra, scanning electron microscope, mercury porosimetry measurements, laser scanning confocal microscope, and protein adsorption experiments. Results showed that PGMA-DVB microspheres coated with dextran successfully maintained the macroporous structure and high permeability. The backpressure was only 1.69 MPa at a high flow rate of 2891 cm/h. Consequently, the hydrophilicity and biocompatibility of modified microspheres were greatly improved, and the contact angle decreased from 184 Degree-Sign to 13 Degree-Sign , and nonspecific adsorption of proteins was decreased to little or none. The clad dextran coating with large amounts of hydroxyl group was easily derived to be various functional groups. The derived media have great potential applications in rapid protein chromatography. - Highlights: Black-Right-Pointing-Pointer Macroporous PGMA-DVB microspheres were covalently coated with dextran. Black-Right-Pointing-Pointer The hydrophilicity of the coated microspheres was significantly improved. Black-Right-Pointing-Pointer The irreversible adsorption of proteins was reduced to zero. Black-Right-Pointing-Pointer The coated microspheres can maintain the macropore structure. Black-Right-Pointing-Pointer The coated microspheres

  10. Covalently coating dextran on macroporous polyglycidyl methacrylate microsphere enabled rapid protein chromatographic separation

    Zhang, Rongyue; Li, Qiang; Li, Juan; Zhou, Weiqing; Ye, Peili; Gao, Yang; Ma, Guanghui; Su, Zhiguo

    2012-01-01

    Protein denaturation and nonspecific adsorption on polymer media as a chromatographic support have been a problem which needs to be overcome. Macroporous poly(glycidyl methacrylate–divinylbezene) (PGMA–DVB) microspheres prepared in this study were firstly covalently coated with dextran through a three-step method. The dextran was firstly adsorbed onto the microspheres and then covalently bound to the PGMA–DVB microsphere through ether bonds which were formed by hydroxyl group reacting with epoxy group at the presence of 4-(Dimethylamino) pyridine. Finally, the coating dextran layer was crosslinked by ethylene glycol diglycidyl ether to form the continuous network coating. The coated microspheres were characterized by Fourier transform infrared spectra, scanning electron microscope, mercury porosimetry measurements, laser scanning confocal microscope, and protein adsorption experiments. Results showed that PGMA–DVB microspheres coated with dextran successfully maintained the macroporous structure and high permeability. The backpressure was only 1.69 MPa at a high flow rate of 2891 cm/h. Consequently, the hydrophilicity and biocompatibility of modified microspheres were greatly improved, and the contact angle decreased from 184° to 13°, and nonspecific adsorption of proteins was decreased to little or none. The clad dextran coating with large amounts of hydroxyl group was easily derived to be various functional groups. The derived media have great potential applications in rapid protein chromatography. - Highlights: ► Macroporous PGMA–DVB microspheres were covalently coated with dextran. ► The hydrophilicity of the coated microspheres was significantly improved. ► The irreversible adsorption of proteins was reduced to zero. ► The coated microspheres can maintain the macropore structure. ► The coated microspheres were applied to rapid protein separation.

  11. Comparison of two validated gas-chromatographic methods for the determination of trihalomethanes in drinking water Comparação de dois métodos cromatográficos validados para a dosagem de trialometanos em água potável

    Maria Yumiko Tominaga; Antonio Flavio Mídio

    2003-01-01

    In this paper the results obtained using two validated gas-chromatographic procedures on drinking water for the determination of trihalomethanes are compared. The volatile compounds, chloroform (CF), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform (BF) were detected by purge and trap capillary column gas-chromatography with electrolytic conductivity detector ( ELCD) and the simple and rapid gas-chromatographic method by electron capture detector (ECD) after liquid-liqui...

  12. Gas chromatographic sensing on an optical fiber by mode-filtered light detection.

    Bruckner, C A; Synovec, R E

    1996-06-01

    A chemical sensor for gas phase measurements is reported which combines the principles of chemical separation and fiber optic detection. The analyzer incorporates an annular column Chromatographic sensor, constructed by inserting a polymer-clad optical fiber into a silica capillary. Light from a helium-neon laser is launched down the fiber, producing a steady intensity distribution within the fiber, but a low background of scattered light. When sample vapor is introduced to the sensor, and an analyte-rich volume interacts with the polymer cladding, Chromatographic retention is observed simultaneously with a change in the local refractive index of the cladding. An increase in cladding refractive index (RI) causes light to be coupled out of the fiber, with detection at a right-angle to the annular column length to provide optimum S/N ratio. This detection mechanism is called mode-filtered light detection. We report a gas Chromatographic separation on a 3.1 m annular column (320 microm i.d. silica tube, 228 microm o.d. fiber with a 12 microm fluorinated silicone clad) of methane, benzene, butanone and chlorobenzene in 6 min. The annular column length was reduced to 22 cm to function as a sensor, with selected organic vapors exhibiting unique retention times and detection selectivity. The detection selectivity is determined by the analyte RI and the partition coefficient into the cladding. The calculated limit of detection (LOD) for benzene vapor is 0.03% by volume in nitrogen, and several chlorinated species had LOD values less than 1%. For binary mixtures of organic vapors, the detected response appears to be the linear combination of the two organic standards, suggesting that the annular column may be useful as a general approach for designing chemical sensors that incorporate separation and optical detection principles simultaneously.

  13. Gas chromatographic/mass spectrometric determination of carbon isotope composition in unpurified samples: methamphetamine example.

    Low, I A; Liu, R H; Legendre, M G; Piotrowski, E G; Furner, R L

    1986-10-01

    A gas chromatograph/quadrupole mass spectrometer system, operated in electron impact/selected ion monitoring mode, is used to determine the intensity ratio of the m/z 59 and the m/z 58 ions of the [C3H8N]+ fragment derived from methamphetamine samples synthesized with varying amounts of 13C-labeled methylamine. Crude products are introduced into the gas chromatograph without prior cleanup. The ratios measured were in excellent agreement with those calculated. A change in 0.25% use of 13C-methylamine is sufficient for product differentiation. The feasibility of using isotope labeling and subsequent mass spectrometric isotope ratio measurement as the basis of a compound tracing mechanism is discussed. Specifically, if methamphetamine samples manufactured from legal sources are asked to incorporate distinct 13C compositions, their sources can be traced when samples are diverted into illegal channels. Samples derived from illicit preparations can also be traced if the manufacturers of a precursor (methylamine in this case) incorporate distinct 13C compositions in their products.

  14. Application of Gas Chromatographic analysis to RPC detectors in the ATLAS experiment at CERN-LHC

    De Asmundis, R

    2007-01-01

    Starting from 2007 a large number (1200) Resistive Plate Chambers (RPC) detectors will be used as muon trigger detectors in the ATLAS Experiment at CERN-LHC accelerator. RPC are gaseous detector in which the quality and the stability of the gas mixture as well as the design of the gas supplying system, play a fundamental role in their functioning. RPC are foreseen to work more than ten years in the high radiation environment of ATLAS and the gas mixture acts really as a "lifeguard" for the detectors. For this reason a great attention has been devoted to the gas studies in order to optimize RPC performance, robustness and reliability in a high radiation environment. In this paper we describe the work done to decide how to supply and control in an optimal way the gas to the detectors, in order to ensure their best performance for a long time. The activity, based on Gas Chromatographic (GC) analysis, has been carried on a sample of final RPC working in radiation conditions much more intense than those foreseen f...

  15. Detection system for a gas chromatograph. [. cap alpha. -methylnaphthalene,. beta. -methylnapthalene

    Hayes, J.M.; Small, G.J.

    1982-04-26

    A method and apparatus are described for the quantitative analysis of vaporizable compounds, and in particular of polycyclic aromatic hydrocarbons which may be induced to fluoresce. The sample to be analyzed is injected into a gas chromatography column and is eluted through a narrow orifice into a vacuum chamber. The free expansion of the eluted sample into the vacuum chamber creates a supersonic molecular beam in which the sample molecules are cooled to the extent that the excited vibrational and rotational levels are substantially depopulated. The cooled molecules, when induced to fluoresce by laser excitation, give greatly simplified spectra suitable for analytical purposes. The laser induced fluorimetry provides great selectivity, and the gas chromatograph provides quantitative transfer of the sample to the molecular beam. 3 figures, 2 tables.

  16. Qualification of an Agilent Technologies 7890A gas chromatograph used in the biotechnology industry

    Alvarez Gonzalez, Alberto; Tambara Hernandez, Yanet; Alvarez Gil, Felix

    2014-01-01

    The drug manufacture is governed by strict international standards that guarantee reproducibility and consistency of results. The qualification of the instruments used in the productive processes, as well as in the characterization of products and their quality control are prerequisites to the validation of any analytical technique using them. One of the instrumental techniques used in the biotechnical industry is Gas Chromatography. A standard of pure caffeine was used for analysis in addition to a HP-5 30 m x 0,32 mm d.i. and 0,33 μm thick film column was used in a Gas Chromatograph coupled with a Flame Ionization Detector. For the testing of the different modules involved in the analysis (injector, column, oven and detector), an experimental design was made to estimate several parameters

  17. A rapid hydrophilic interaction liquid chromatographic determination of glimepiride in pharmaceutical formulations

    Si Zhou

    2017-09-01

    Full Text Available Glimepiride is one of the most widely prescribed antidiabetic drugs and contains both hydrophobic and hydrophilic functional groups in its molecules, and thus could be analyzed by either reversed-phase high performance liquid chromatography (HPLC or hydrophilic interaction liquid chromatography (HILIC. In the literature, however, only reversed-phase HPLC has been reported. In this study, a simple, rapid and accurate hydrophilic interaction liquid chromatographic method was developed for the determination of glimepiride in pharmaceutical formulations. The analytical method comprised a fast ultrasound-assisted extraction with acetonitrile as a solvent followed by HILIC separation and quantification using a Waters Spherisorb S5NH2 hydrophilic column with a mobile phase consisting of acetonitrile and aqueous acetate buffer (5.0 mM. The retention time of glimepiride increased slightly with decrease of mobile phase pH value from 6.8 to 5.8 and of acetonitrile content from 60% to 40%, indicating that both hydrophilic, ionic, and hydrophobic interactions were involved in the HILIC retention and elution mechanisms. Quantitation was carried out with a mobile phase of 40% acetonitrile and 60% aqueous acetate buffer (5.0 mM at pH 6.3, by relating the peak area of glimepiride to that of the internal standard, with a detection limit of 15.0 μg/L. UV light absorption responses at 228 nm were linear over a wide concentration range from 50.0 μg/L to 6.00 mg/L. The recoveries of the standard added to pharmaceutical tablet samples were 99.4–103.0% for glimepiride, and the relative standard deviation for the analyte was less than 1.0%. This method has been successfully applied to determine the glimepiride contents in pharmaceutical formulations.

  18. Gas chromatographic determination of Di-n-butyl phosphate in radioactive lean organic solvent of FBTR carbide fuel reprocessing

    Velavendan, P.; Ganesh, S.; Pandey, N.K.; Kamachi Mudali, U.; Natarajan, R.

    2011-01-01

    In the present work Di-n- butyl phosphate (DBP) a degraded product of Tri-n-butyl phosphate (TBP) formed by acid hydrolysis and radiolysis in the PUREX process was analyzed. Lean organic streams of different fuel burn-up FBTR carbide fuel reprocessing solution was determined by standard Gas Chromatographic technique. The method involves the conversion of non-volatile Di-n-butyl phosphate into volatile and stable derivatives by the action of diazomethane and then determined by Gas Chromatograph (GC). A calibration graph was made for DBP concentration range of 200-2000 ppm with correlation coefficient of 0.99587 and RSD 1.2 %. (author)

  19. Measurement method for benzene, toluene, and xylene in the atmosphere by the gas chromatographic method

    Shiroyama, H

    1975-08-01

    The chromatographic method for measuring benzene, toluene, and xylene (three isomers) in the atmosphere was evaluated using the Varian model 2740-10 gas chromatograph. As a solvent, n-hexane was most suitable, and the detection limit was improved by increasing the purity of n-hexane. The calibration curves were prepared, the recovery rate was calculated (76.0-99.4 percent), and the correlation coefficient was obtained from regression curves (r equals 0.97-0.99). Samples collected at a naphtha cracking plant, an aluminum smelting mill, a pharmaceutical plant, a carbon electrode manufacturing plant, a plywood manufacturing plant, a plastic bathtub manufacturing plant, and along a major highway were analyzed. All three substances were detected in all samples with the concentration of toluene high compared to the other two. Among xylene isomers, the concentration of p-xylene was always the lowest while m- and o-xylene varied from place to place. In the atmosphere along the highway, the benzene, toluene, and xylene determined were 0.01-0.09 ppM. No benzene, toluene, and xylene were detected in atmospheric samples used as controls.

  20. Rapid on-site sensing aflatoxin B1 in food and feed via a chromatographic time-resolved fluoroimmunoassay.

    Zhaowei Zhang

    Full Text Available Aflatoxin B1 poses grave threats to food and feed safety due to its strong carcinogenesis and toxicity, thus requiring ultrasensitive rapid on-site determination. Herein, a portable immunosensor based on chromatographic time-resolved fluoroimmunoassay was developed for sensitive and on-site determination of aflatoxin B1 in food and feed samples. Chromatographic time-resolved fluoroimmunoassay offered a magnified positive signal and low signal-to-noise ratio in time-resolved mode due to the absence of noise interference caused by excitation light sources. Compared with the immunosensing performance in previous studies, this platform demonstrated a wider dynamic range of 0.2-60 μg/kg, lower limit of detection from 0.06 to 0.12 µg/kg, and considerable recovery from 80.5% to 116.7% for different food and feed sample matrices. It was found to be little cross-reactivity with other aflatoxins (B2, G1, G2, and M1. In the case of determination of aflatoxin B1 in peanuts, corn, soy sauce, vegetable oil, and mouse feed, excellent agreement was found when compared with aflatoxin B1 determination via the conversational high-performance liquid chromatography method. The chromatographic time-resolved fluoroimmunoassay affords a powerful alternative for rapid on-site determination of aflatoxin B1 and holds a promise for food safety in consideration of practical food safety and environmental monitoring.

  1. Rapid on-site sensing aflatoxin B1 in food and feed via a chromatographic time-resolved fluoroimmunoassay.

    Zhang, Zhaowei; Tang, Xiaoqian; Wang, Du; Zhang, Qi; Li, Peiwu; Ding, Xiaoxia

    2015-01-01

    Aflatoxin B1 poses grave threats to food and feed safety due to its strong carcinogenesis and toxicity, thus requiring ultrasensitive rapid on-site determination. Herein, a portable immunosensor based on chromatographic time-resolved fluoroimmunoassay was developed for sensitive and on-site determination of aflatoxin B1 in food and feed samples. Chromatographic time-resolved fluoroimmunoassay offered a magnified positive signal and low signal-to-noise ratio in time-resolved mode due to the absence of noise interference caused by excitation light sources. Compared with the immunosensing performance in previous studies, this platform demonstrated a wider dynamic range of 0.2-60 μg/kg, lower limit of detection from 0.06 to 0.12 µg/kg, and considerable recovery from 80.5% to 116.7% for different food and feed sample matrices. It was found to be little cross-reactivity with other aflatoxins (B2, G1, G2, and M1). In the case of determination of aflatoxin B1 in peanuts, corn, soy sauce, vegetable oil, and mouse feed, excellent agreement was found when compared with aflatoxin B1 determination via the conversational high-performance liquid chromatography method. The chromatographic time-resolved fluoroimmunoassay affords a powerful alternative for rapid on-site determination of aflatoxin B1 and holds a promise for food safety in consideration of practical food safety and environmental monitoring.

  2. Determination of trihalomethanes in waters by ionic liquid-based single drop microextraction/gas chromatographic/mass spectrometry.

    Aguilera-Herrador, Eva; Lucena, Rafael; Cárdenas, Soledad; Valcárcel, Miguel

    2008-10-31

    A simple, rapid, solventless method for the determination of trihalomethanes (THMs) (chloroform, bromodichloromethane, dibromochloromethane and bromoform) in water samples is presented. The analytes are extracted from the headspace of the aqueous matrix into a 2 microL drop of the ionic liquid 1-octyl-3-methyl-imidazolium hexafluorophosphate working at 30 degrees C for 30 min. The separation and detection of the target compounds is accomplished by gas chromatography/mass spectrometry owing to the use of an interface that efficiently transfers the analytes extracted in the ionic liquid drop to the gas chromatograph while preventing the ionic liquid from entering the column. The detection limits obtained are below the values compelled by the legislation, ranging from 0.5 microg L(-1) for chloroform and bromodichloromethane to 0.9 microg L(-1) for dibromochloromethane. The use of ionic liquid in the extraction procedure avoids the use of organic solvents and leads to relative standard deviations that range from 3.1% to 4.8%.

  3. Gas chromatographic determination of residual hydrazine and morpholine in boiler feed water and steam condensates

    Vatsala, S.; Bansal, V.; Tuli, D.K.; Rai, M.M.; Jain, S.K.; Srivastava, S.P.; Bhatnagar, A.K.

    1994-01-01

    Hydrazine, an oxygen scavenger in boiler water, was derivatised to the corresponding acetone azine and determined at the ng ml -1 level by gas chromatography. Morpholine, a corrosion inhibitor used in steam boilers, was estimated either directly (if >2.0 μg ml -1 ) or by quantitative preconcentration (0.1 ng-2.0 μg ml -1 ). To obtain symmetrical peaks for these amines, the column packing was coated with KOH. Use of a nitrogen-specific detector improved accuracy of estimation of hydrazine and morpholine, giving a RSD of 1.9-3.6%. Chromatographic analysis of these amines in boiler feed water and steam condensate samples collected from boilers servicing a pertroleum refinery is described. Environmental safety regulations calls for monitoring of hydrazine and the methods developed can easily be adapted for this purpose. (orig.)

  4. Use of adsorption and gas chromatographic techniques in estimating biodegradation of indigenous crude oils

    Kokub, D.; Allahi, A.; Shafeeq, M.; Khalid, Z.M.; Malik, K.A.; Hussain, A.

    1993-01-01

    Indigenous crude oils could be degraded and emulsified upto varying degree by locally isolated bacteria. Degradation and emulsification was found to be dependent upon the chemical composition of the crude oils. Tando Alum and Khashkheli crude oils were emulsified in 27 and 33 days of incubation respectively. While Joyamair crude oil and not emulsify even mainly due to high viscosity of this oil. Using adsorption chromatographic technique, oil from control (uninoculated) and bio degraded flasks was fractioned into the deasphaltened oil containing saturate, aromatic, NSO (nitrogen, sulphur, oxygen) containing hydrocarbons) and soluble asphaltenes. Saturate fractions from control and degraded oil were further analysed by gas liquid chromatography. From these analyses, it was observed that saturate fraction was preferentially utilized and the crude oils having greater contents of saturate fraction were better emulsified than those low in this fraction. Utilization of various fractions of crude oils was in the order saturate> aromatic> NSO. (author)

  5. Gas Chromatographic Mass Spectrometric Determination of Myo-inositol in Humans Utilizing a Deuterated Internal Standard

    Andersen, Jan Rud; Larsen, Elfinn; Harbo, Helge

    1982-01-01

    The isotopic dilution technique was used for determining the content of myo-inositol in human urine, plasma and haemolysed erythrocyte samples. A deuterated myo-inositol, synthesized from inosose-2 by base-catalysed exchange of hydrogens by deuterium, followed by reduction of the inosose with 2H2......, was added as internal standard to the samples at an early stage in the analytical procedure. After separation and derivatization to the hexa-acetate, the gas chromatographic mass spectrometric analysis was carried out. A 25 m fused silica capillary column coated with methyl silicone was used, and the ions...... selected for monitoring were m/z 210 and m/z 214, which are characteristic and abundant fragment ions from unlabelled and hexadeuterated myo-inositolhexa-acetate, respectively. Calibration curves from water, urine, plasma and haemolysed erythrocytes show parallel, linear responses in the ratio between...

  6. Determination and discrimination of biodiesel fuels by gas chromatographic and chemometric methods

    Milina, R.; Mustafa, Z.; Bojilov, D.; Dagnon, S.; Moskovkina, M.

    2016-03-01

    Pattern recognition method (PRM) was applied to gas chromatographic (GC) data for a fatty acid methyl esters (FAME) composition of commercial and laboratory synthesized biodiesel fuels from vegetable oils including sunflower, rapeseed, corn and palm oils. Two GC quantitative methods to calculate individual fames were compared: Area % and internal standard. The both methods were applied for analysis of two certified reference materials. The statistical processing of the obtained results demonstrates the accuracy and precision of the two methods and allows them to be compared. For further chemometric investigations of biodiesel fuels by their FAME-profiles any of those methods can be used. PRM results of FAME profiles of samples from different vegetable oils show a successful recognition of biodiesels according to the feedstock. The information obtained can be used for selection of feedstock to produce biodiesels with certain properties, for assessing their interchangeability, for fuel spillage and remedial actions in the environment.

  7. Modified molecular sieves: stationary phase for the gas chromatographic separation of hydrogen isotopes

    Pushpa, K.K.; Annaji Rao, K.; Iyer, R.M.

    1993-01-01

    Gas chromatographic separation of hydrogen isotopes on different molecular sieves at liquid nitrogen temperature has been investigated. Normal molecular sieves 5A, 13X and AW500 are not satisfactory for the purpose both in the partially dehydrated as well as totally dehydrated state. Molecular sieve 4A in partially dehydrated state separated H 2 and D 2 while H 2 and HD are not well resolved. Iron exchanged or coated molecular sieves 4A, 5A, 13X and AW500 in the partially dehydrated state separated the isotopic mixtures H 2 , HD, D 2 and H 2 , HT, T 2 . The resolution varied depending on the amount of iron content and the residual moisture in the molecular sieves. Good separations were obtained on 15% Fe coated molecular sieve 5A and 5% Fe coated molecular sieve 4A. (author). 18 refs., 6 figs., 3 tabs

  8. Headspace solid-phase microextraction procedures for gas chromatographic analysis of biological fluids and materials.

    Mills, G A; Walker, V

    2000-12-01

    Solid-phase microextraction (SPME) is a new solventless sample preparation technique that is finding wide usage. This review provides updated information on headspace SPME with gas chromatographic separation for the extraction and measurement of volatile and semivolatile analytes in biological fluids and materials. Firstly the background to the technique is given in terms of apparatus, fibres used, extraction conditions and derivatisation procedures. Then the different matrices, urine, blood, faeces, breast milk, hair, breath and saliva are considered separately. For each, methods appropriate for the analysis of drugs and metabolites, solvents and chemicals, anaesthetics, pesticides, organometallics and endogenous compounds are reviewed and the main experimental conditions outlined with specific examples. Then finally, the future potential of SPME for the analysis of biological samples in terms of the development of new devices and fibre chemistries and its coupling with high-performance liquid chromatography is discussed.

  9. On the ability of the Viking gas chromatograph-mass spectrometer to detect organic matter.

    Biemann, Klaus

    2007-06-19

    A recent paper by Navarro-Gonzalez et al. [Navarro-Gonzalez R, Navarro KF, de la Rosa J, Iniguez E, Molina P, Miranda LD, Morales P, Cienfuegos E, Coll P, Raulin F, et al. (2006) Proc Natl Acad Sci USA 103:16089-16094] claims to show that the Viking GCMS (gas chromatograph-mass spectrometer) experiment, which carried out a search for organic matter at the surface of Mars in 1976, "may have been blind to low levels of organics." To rebut this assertion, the Viking experiment, test data, and results on Mars are reviewed, and the fallacies in the design, execution, and interpretation of the new experiments presented by Navarro-Gonzalez et al. are critically examined.

  10. Formation of hydrocarbons in irradiated Brazilian beans: gas chromatographic analysis to detect radiation processing

    Villavicencio, A.L.C.H.; Mancini-Filho, J.; Hartmann, M.; Ammon, J.; Delincee, H.

    1997-01-01

    Radiation processing of beans, which are a major source of dietary protein in Brazil, is a valuable alternative to chemical fumigation to combat postharvest losses due to insect infestation. To ensure free consumer choice, irradiated food will be labeled as such, and to enforce labeling, analytical methods to detect the irradiation treatment in the food product itself are desirable. In two varieties of Brazilian beans, Carioca and Macacar beans, the radiolytic formation of hydrocarbons formed after alpha and beta cleavage, with regard to the carbonyl group in triglycerides, have been studied. Using gas chromatographic analysis of these radiolytic hydrocarbons, different yields per precursor fatty acid are observed for the two types of beans. However, the typical degradation pattern allows the identification of the irradiation treatment in both bean varieties, even after 6 months of storage

  11. Volatile hexafluoroacetylacetonates for the isolation and gas-chromatographic determination of trace metals. Pt. 1

    Hellmuth, K.H.; Mirzai, H.

    1985-01-01

    The optimization of the extraction of metal cations [Sc(III), Cr(III), Mn(II), Fe(III), Co(II), Cu(II), Zn(II), Y(III), Ag(I), Cd(II), La(IIII), Ce(III), Eu(III), Yb(III), Hg(II), Pb(II), Th(IV), U(IV, VI) and Am(III)] in the form of mixed-ligand complexes with hexafluoroacetylacetone and neutral donators with nitrogen atoms or P=O-groups is described. The thermal and gas-chromatographic characteristics of the extracted volatile compounds are reported. Optimal results were achieved using tri-n-butyl-phosphine oxide as donator. (orig.) [de

  12. Determination and discrimination of biodiesel fuels by gas chromatographic and chemometric methods

    Milina R.

    2016-03-01

    Full Text Available Pattern recognition method (PRM was applied to gas chromatographic (GC data for a fatty acid methyl esters (FAME composition of commercial and laboratory synthesized biodiesel fuels from vegetable oils including sunflower, rapeseed, corn and palm oils. Two GC quantitative methods to calculate individual fames were compared: Area % and internal standard. The both methods were applied for analysis of two certified reference materials. The statistical processing of the obtained results demonstrates the accuracy and precision of the two methods and allows them to be compared. For further chemometric investigations of biodiesel fuels by their FAME-profiles any of those methods can be used. PRM results of FAME profiles of samples from different vegetable oils show a successful recognition of biodiesels according to the feedstock. The information obtained can be used for selection of feedstock to produce biodiesels with certain properties, for assessing their interchangeability, for fuel spillage and remedial actions in the environment.

  13. Thermal soil desorption for total petroleum hydrocarbon testing on gas chromatographs

    Mott, J.

    1995-01-01

    Testing for total petroleum hydrocarbons (TPH) is one of the most common analytical tests today. A recent development in chromatography incorporates Thermal Soil Desorption technology to enable analyses of unprepared soil samples for volatiles such as BTEX components and semi-volatiles such as diesel, PCBs, PAHs and pesticides in the same chromatogram, while in the field. A gas chromatograph is the preferred method for determining TPH because the column in a GC separates the individual hydrocarbons compounds such as benzene and toluene from each other and measures each individually. A GC analysis will determine not only the total amount of hydrocarbon, but also whether it is gasoline, diesel or another compound. TPH analysis with a GC is typically conducted with a Flame Ionization Detector (FID). Extensive field and laboratory testing has shown that incorporation of a Thermal Soil Desorber offers many benefits over traditional analytical testing methods such as Headspace, Solvent Extraction, and Purge and Trap. This paper presents the process of implementing Thermal Soil Desorption in gas chromatography, including procedures for, and advantages of faster testing and analysis times, concurrent volatile and semi-volatile analysis, minimized sample manipulation, single gas (H 2 ) operation, and detection to the part-per billion levels

  14. A purge-and-trap capillary column gas chromatographic method for the measurement of halocarbons in water and air

    Happell, J.D.; Wallace, D.W.R.; Wills, K.D.; Wilke, R.J.; Neill, C.C.

    1996-06-01

    This report describes an automated, accurate, precise and sensitive capillary column purge- and -trap method capable of quantifying CFC-12, CFC-11, CFC-113, CH{sub 3}CCL{sub 3}, and CCL{sub 4} during a single chromatographic analysis in either water or gas phase samples.

  15. Abnormal tyrosine and phenylalanine metabolism in patients with tyrosyluria and phenylketonuria; gas-liquid chromatographic analysis of urinary metabolites

    Wadman, S.K.; Heiden, C. van der; Ketting, D.; Sprang, F.J. van

    Gas-liquid chromatographic methods have been developed for the analysis of: urinary phenylalanine metabolites (I) in patients with phenylketonuria, tyrosine metabolites (II) in patients with a disturbed tyrosine metabolism at the level of p-hydroxyphenylpyruvate hydroxylase, and homogentisic acid in

  16. A Rapid Process for Fabricating Gas Sensors

    Chun-Ching Hsiao

    2014-07-01

    Full Text Available Zinc oxide (ZnO is a low-toxicity and environmentally-friendly material applied on devices, sensors or actuators for “green” usage. A porous ZnO film deposited by a rapid process of aerosol deposition (AD was employed as the gas-sensitive material in a CO gas sensor to reduce both manufacturing cost and time, and to further extend the AD application for a large-scale production. The relative resistance change (△R/R of the ZnO gas sensor was used for gas measurement. The fabricated ZnO gas sensors were measured with operating temperatures ranging from 110 °C to 180 °C, and CO concentrations ranging from 100 ppm to 1000 ppm. The sensitivity and the response time presented good performance at increasing operating temperatures and CO concentrations. AD was successfully for applied for making ZnO gas sensors with great potential for achieving high deposition rates at low deposition temperatures, large-scale production and low cost.

  17. Autonomous gas chromatograph system for Thermal Enhanced Vapor Extraction System (TEVES) proof of concept demonstration

    Peter, F.J.; Laguna, G.R.

    1996-09-01

    An autonomous gas chromatograph system was designed and built to support the Thermal Enhanced Vapor Extraction System (TEVES) demonstration. TEVES is a remediation demonstration that seeks to enhance an existing technology (vacuum extraction) by adding a new technology (soil heating). A pilot scale unit was set up at one of the organic waste disposal pits at the Sandia National Laboratories Chemical Waste Landfill (CWL) in Tech Area 3. The responsibility for engineering a major part of the process instrumentation for TEVES belonged to the Manufacturing Control Subsystems Department. The primary mission of the one-of-a-kind hardware/software system is to perform on-site gas sampling and analysis to quantify a variety of volatile organic compounds (VOCs) from various sources during TEVES operations. The secondary mission is to monitor a variety of TEVES process physical parameters such as extraction manifold temperature, pressure, humidity, and flow rate, and various subsurface pressures. The system began operation in September 1994 and was still in use on follow-on projects when this report was published

  18. A Gas Chromatographic Continuous Emissions Monitoring System for the Determination of VOCs and HAPs.

    Coleman, William M; Gordon, Bert M

    1996-01-01

    This article describes a new gas chromatography-based emissions monitoring system for measuring volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). The system is composed of a dual-column gas chromatograph equipped with thermal conductivity detectors, in which separation is optimized for fast chromatography. The system has the necessary valving for stream selection, which allows automatic calibration of the system at predetermined times and successive measurement of individual VOCs before and after a control device. Nine different VOCs (two of which are HAPs), plus methane (CH4) and carbon dioxide (CO2) are separated and quantified every two minutes. The accuracy and precision of this system has been demonstrated to be greater than 95%. The system employs a mass flow measurement device and also calculates and displays processed emission data, such as control device efficiency and total weight emitted during given time periods. Two such systems have been operational for one year in two separate gravure printing facilities; minimal upkeep is required, about one hour per month. One of these systems, used before and after a carbon adsorber, has been approved by the pertinent local permitting authority.

  19. Authentication of commercial spices based on the similarities between gas chromatographic fingerprints.

    Matsushita, Takaya; Zhao, Jing Jing; Igura, Noriyuki; Shimoda, Mitsuya

    2018-06-01

    A simple and solvent-free method was developed for the authentication of commercial spices. The similarities between gas chromatographic fingerprints were measured using similarity indices and multivariate data analyses, as morphological differentiation between dried powders and small spice particles was challenging. The volatile compounds present in 11 spices (i.e. allspice, anise, black pepper, caraway, clove, coriander, cumin, dill, fennel, star anise, and white pepper) were extracted by headspace solid-phase microextraction, and analysed by gas chromatography-mass spectrometry. The largest 10 peaks were selected from each total ion chromatogram, and a total of 65 volatiles were tentatively identified. The similarity indices (i.e. the congruence coefficients) were calculated using the data matrices of the identified compound relative peak areas to differentiate between two sets of fingerprints. Where pairs of similar fingerprints produced high congruence coefficients (>0.80), distinctive volatile markers were employed to distinguish between these samples. In addition, hierarchical cluster analysis and principal component analysis were performed to visualise the similarity among fingerprints, and the analysed spices were grouped and characterised according to their distinctive major components. This method is suitable for screening unknown spices, and can therefore be employed to evaluate the quality and authenticity of various spices. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  20. A low-power pressure-and temperature-programmed separation system for a micro gas chromatograph.

    Sacks, Richard D. (University of Michigan, Ann Arbor, MI); Robinson, Alex Lockwood (Advanced Sensor Technologies, Albuquerque, NM); Lambertus, Gordon R. (University of Michigan, Ann Arbor, MI); Potkay, Joseph A. (University of Michigan, Ann Arbor, MI); Wise, Kensall D. (University of Michigan, Ann Arbor, MI)

    2006-10-01

    This thesis presents the theory, design, fabrication and testing of the microvalves and columns necessary in a pressure- and temperature-programmed micro gas chromatograph ({micro}GC). Two microcolumn designs are investigated: a bonded Si-glass column having a rectangular cross section and a vapor-deposited silicon oxynitride (Sion) column having a roughly circular cross section. Both microcolumns contain integrated heaters and sensors for rapid, controlled heating. The 3.2 cm x 3.2 cm, 3 m-long silicon-glass column, coated with a non-polar polydimethylsiloxane (PDMS) stationary phase, separates 30 volatile organic compounds (VOCs) in less than 6 min. This is the most efficient micromachined column reported to date, producing greater than 4000 plates/m. The 2.7 mm x 1.4 mm Sion column eliminates the glass sealing plate and silicon substrate using deposited dielectrics and is the lowest power and fastest GC column reported to date; it requires only 11 mW to raise the column temperature by 100 C and has a response time of 11s and natural temperature ramp rate of 580 C/min. A 1 m-long PDMS-coated Sion microcolumn separates 10 VOCs in 52s. A system-based design approach was used for both columns.

  1. Simultaneous derivatisation and preconcentration of parabens in food and other matrices by isobutyl chloroformate and dispersive liquid-liquid microextraction followed by gas chromatographic analysis.

    Jain, Rajeev; Mudiam, Mohana Krishna Reddy; Chauhan, Abhishek; Ch, Ratnasekhar; Murthy, R C; Khan, Haider A

    2013-11-01

    A simple, rapid and economical method has been proposed for the quantitative determination of parabens (methyl, ethyl, propyl and butyl paraben) in different samples (food, cosmetics and water) based on isobutyl chloroformate (IBCF) derivatisation and preconcentration using dispersive liquid-liquid microextraction in single step. Under optimum conditions, solid samples were extracted with ethanol (disperser solvent) and 200 μL of this extract along with 50 μL of chloroform (extraction solvent) and 10 μL of IBCF was rapidly injected into 2 mL of ultra-pure water containing 150 μL of pyridine to induce formation of a cloudy state. After centrifugation, 1 μL of the sedimented phase was analysed using gas chromatograph-flame ionisation detector (GC-FID) and the peaks were confirmed using gas chromatograph-positive chemical ionisation-mass spectrometer (GC-PCI-MS). Method was found to be linear over the range of 0.1-10 μg mL(-1) with square of correlation coefficient (R(2)) in the range of 0.9913-0.9992. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.029-0.102 μg mL(-1) and 0.095-0.336 μg mL(-1) with a signal to noise ratio of 3:1 and 10:1, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Characterization of crude oils and petroleum products: (I Elution liquid chromatographic separation and gas chromatographic analysis of crude oils and petroleum products

    E.O. Odebunmi

    2002-12-01

    Full Text Available Some physical and chemical properties of samples of light, medium and heavy Nigerian crude oils and petroleum products including gasoline, kerosene and engine oil have been measured and are reported in this paper. The crude oils and petroleum products have also been characterized by fractional distillation and elution liquid chromatography. The fractions obtained from elution liquid chromatography were analyzed using gas chromatography (GC. The GC fractions were identified by comparing the retention time of peaks in the unknown samples with those of components of calibration standard mixtures. The importance of the physico-chemical properties and the significance of the fractional distillation and chromatographic separation methods to industrial process operations have been discussed.

  3. Chromatographic efficiency of polar capillary columns applied for the analysis of fatty acid methyl esters by gas chromatography.

    Waktola, Habtewold D; Mjøs, Svein A

    2018-04-01

    The chromatographic efficiency that could be achieved in temperature-programmed gas chromatography was compared for four capillary columns that are typically applied for analysis of fatty acid methyl esters (FAME). Three different carrier gases, hydrogen, helium and nitrogen, were applied. For each experiment, the carrier gas velocities and the temperature rates were varied with a full 9 × 3 design, with nine levels on the carrier gas velocity and temperature rates of 1, 2 or 3°C/min. Response surface methodology was used to create models of chromatographic efficiency as a function of temperature rate and carrier gas velocity. The chromatographic efficiency was defined as the inverse of peak widths measured in retention index units. The final results were standardized so that the efficiencies that could be achieved within a certain time frame, defined by the retention time of the last compound in the chromatogram, could be compared. The results show that there were clear differences in the efficiencies that could be achieved with the different columns and that the efficiency decreased with increasing polarity of the stationary phase. The differences can be explained by higher resistance to mass transfer in the stationary phase in the most polar columns. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Gas chromatographic determination with electron capture detection of residual ethylene oxide in intraocular lenses

    Kikuchi, H.; Nakamura, A.; Tsuji, K.

    1988-01-01

    A sensitive method is described to determine trace quantities of ethylene oxide (EO) in EO-sterilized intraocular lenses (IOLs). An IOL is dipped in ethanol containing 0.25 ppm propylene oxide (PO) in a 4 mL vial, 2 drops of freshly distilled hydrobromic acid is added through a septum, and the mixture is warmed at 50/sup 0/C for 24 h. It is then neutralized by vigorous shaking with sodium bicarbonate, dehydrated with anhydrous sodium sulfate, and filtered. The filtrate is injected into a gas chromatograph with electron-capture detection, and the peak height ratio of ethylene bromohydrin/propylene bromohydrin is measured. EO residue is calculated from the calibration curve obtained through a similar procedure with the standard EO/PO solutions. The limit of determination is 0.04 ..mu..g/lens (ca 2.0 ppm). When EO residue levels were determined for IOLs sampled at 3 different aeration periods after stabilization, the authors found that 9 days of aeration was necessary to meet the US Food and Drug Administration proposed limit for EO residue in IOLs.

  5. Chromatographic analysis of methylglyoxal and other α-dicarbonyls using gas-diffusion microextraction.

    Santos, Christiane M; Valente, Inês M; Gonçalves, Luís M; Rodrigues, José A

    2013-12-07

    Many α-dicarbonyl compounds such as methylglyoxal, diacetyl and pentane-2,3-dione are important quality markers of processed foods. They are produced by enzymatic and chemical processes, the Maillard reaction is the most known chemical route for α-dicarbonyl formation. In the case of methylglyoxal, there are obstacles to be overcome when analysing this compound due to its high reactivity, low volatility and low concentration. The use of extraction techniques based on the volatilization of methylglyoxal (like solid-phase microextraction) showed to be ineffective for the methylglyoxal extraction from aqueous solutions. Therefore, derivatization is typically applied to increase analyte's volatility. In this work a new methodology for the extraction and analysis of methylglyoxal and also diacetyl and pentane-2,3-dione from selected food matrices is presented. It is based on a gas-diffusion microextraction step followed by high performance liquid chromatographic analysis. It was successfully applied to port wines, black tea and soy sauce. Methylglyoxal, diacetyl and pentane-2,3-dione were quantified in the following concentration ranges: 0.24-1.74 mg L(-1), 0.1-1.85 mg L(-1) and 0.023-0.15 mg L(-1), respectively. The main advantages over existing methodologies are its simplicity in terms of sample handling, not requiring any chemical modification of the α-dicarbonyls prior to the extraction, low reagent consumption and short time of analysis.

  6. Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating.

    Eglinton, T I; Aluwihare, L I; Bauer, J E; Druffel, E R; McNichol, A P

    1996-03-01

    This paper describes the application of a novel, practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This is achieved through the use of automated preparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of individual target compounds for (14)C analysis by accelerator mass spectrometry (AMS). We developed and tested this approach using a suite of samples (plant lipids, petroleums) whose ages spanned the (14)C time scale and which contained a variety of compound types (fatty acids, sterols, hydrocarbons). Comparison of individual compound and bulk radiocarbon signatures for the isotopically homogeneous samples studied revealed that Δ(14)C values generally agreed well (±10%). Background contamination was assessed at each stage of the isolation procedure, and incomplete solvent removal prior to combustion was the only significant source of additional carbon. Isotope fractionation was addressed through compound-specific stable carbon isotopic analyses. Fractionation of isotopes during isolation of individual compounds was minimal (radiocarbon measurements. The addition of carbon accompanying derivatization of functionalized compounds (e.g., fatty acids and sterols) prior to chromatographic separation represents a further source of potential error. This contribution can be removed using a simple isotopic mass balance approach. Based on these preliminary results, the PCGC-based approach holds promise for accurately determining (14)C ages on compounds specific to a given source within complex, heterogeneous samples.

  7. Different reactivities of amphetamines with N-methyl-bis(trifluoroacetamide) in heated gas chromatographic injectors.

    Hidvégi, E; Hideg, Zs; Somogyi, G P

    2008-03-01

    A fast gas chromatographic mass spectrometric method has been developed earlier for the determination of amphetamine derivatives in human serum and urine. For derivatization, N-methyl-bis(trifluoroacetamide) (MBTFA) was used. Derivatization was performed using an on-line mode, since 1 microl of MBTFA and 1 microl sample extract, dissolved in toluene were injected simultaneously. In this study, the reactivity of the several amphetamine type analytes with MBTFA was investigated. MBTFA used for flash derivatization was applied undiluted on the one hand and diluted 4--4096-fold with acetonitrile on the other hand. Studying several amphetamines in the test sample spiked at the same concentrations we found that they could be divided into 3 groups based on relative target ion peak areas as a function of MBTFA dilution. Group 1, containing only primary amines showed an early increase of the relative peak areas if we increased MBTFA concentration, where group 2 (mainly N-methyl secondary amines) showed that relative peak areas started to increase intensively at higher MBTFA concentrations. Finally, MDEA as an N-ethyl secondary amine, representing group 3, showed significant increase if only slightly diluted MBTFA was used as a flash reagent. This phenomenon can be explained mainly with the less and less reactivity of amine groups in the case of groups 2 and 3, compared to group 1. These findings could help to optimise analytical methods involving flash derivatization processes.

  8. Capillary gas chromatographic analysis of nerve agents using large volume injections. Final report

    Deinum, T.; Nieuwenhuy, C.

    1994-11-01

    The procedure developed at TNO-Prins Maurits Laboratory (TNO-PML) for the verification of intact organophosphorus chemical warfare agents in water samples was improved. The last step in this procedure, the laborious and non-reproducible transfer of an ethyl acetate extract onto a Tenax-adsorption tube followed by thermal desorption of the Tenax-tube, was replaced by large volume injection of the extract onto a capillary gas chromatographic system. The parameters controlling the injection of a large volume of an extract (200 ul) were investigated and optimized. As ethyl acetate caused severe problems, potential new solvents were evaluated. With the improved procedure, the nerve agents sarin, tabun, soman, diisopropyl fluorophosphate (DFP) and VX could be determined in freshly prepared water samples at pg/ml (ppt) levels. The fate of the nerve agents under study in water at two pH`s (4.8 and 6) was investigated. For VX, the pH should be adjusted before extraction. Moreover, it is worthwhile to acidify water samples to diminish hydrolysis.

  9. Gas chromatographic simulated distillation-mass spectrometry for the determination of the boiling point distributions of crude oils

    Roussis; Fitzgerald

    2000-04-01

    The coupling of gas chromatographic simulated distillation with mass spectrometry for the determination of the distillation profiles of crude oils is reported. The method provides the boiling point distributions of both weight and volume percent amounts. The weight percent distribution is obtained from the measured total ion current signal. The total ion current signal is converted to weight percent amount by calibration with a reference crude oil of a known distillation profile. Knowledge of the chemical composition of the crude oil across the boiling range permits the determination of the volume percent distribution. The long-term repeatability is equivalent to or better than the short-term repeatability of the currently available American Society for Testing and Materials (ASTM) gas chromatographic method for simulated distillation. Results obtained by the mass spectrometric method are in very good agreement with results obtained by conventional methods of physical distillation. The compositional information supplied by the method can be used to extensively characterize crude oils.

  10. Implementation of a fully automated process purge-and-trap gas chromatograph at an environmental remediation site

    Blair, D.S.; Morrison, D.J.

    1997-01-01

    The AQUASCAN, a commercially available, fully automated purge-and-trap gas chromatograph from Sentex Systems Inc., was implemented and evaluated as an in-field, automated monitoring system of contaminated groundwater at an active DOE remediation site in Pinellas, FL. Though the AQUASCAN is designed as a stand alone process analytical unit, implementation at this site required additional hardware. The hardware included a sample dilution system and a method for delivering standard solution to the gas chromatograph for automated calibration. As a result of the evaluation the system was determined to be a reliable and accurate instrument. The AQUASCAN reported concentration values for methylene chloride, trichloroethylene, and toluene in the Pinellas ground water were within 20% of reference laboratory values

  11. Gas--liquid chromatographic determination of total inorganic iodine in milk

    Bakker, H.J.

    1977-01-01

    Total inorganic iodine in milk is determined by conversion to iodobutanone, which is quantitated by gas-liquid chromatography and electron capture detection. As little as 10 μg/L can be determined. The thyroid-active iodine content of milk can be determined rapidly with a relative standard deviation of 1.9%. Average recoveries for added iodide and iodine were 95.5 and 94.6%, respectively

  12. A pyrolysis/gas chromatographic method for the determination of hydrogen in solid samples

    Carr, R. H.; Bustin, R.; Gibson, E. K.

    1987-01-01

    A method is described for the determination of hydrogen in solid samples. The sample is heated under vacuum after which the evolved gases are separated by gas chromatography with a helium ionization detector. The system is calibrated by injecting known amounts of hydrogen, as determined manometrically. The method, which is rapid and reliable, was checked for a variety of lunar soils; the limit of detection is about 10 ng of hydrogen.

  13. An integrated methodological approach to the computer-assisted gas chromatographic screening of basic drugs in biological fluids using nitrogen selective detection.

    Dugal, R; Massé, R; Sanchez, G; Bertrand, M J

    1980-01-01

    This paper presents the methodological aspects of a computerized system for the gas-chromatographic screening and primary identification of central nervous system stimulants and narcotic analgesics (including some of their respective metabolites) extracted from urine. The operating conditions of a selective nitrogen detector for optimized analytical functions are discussed, particularly the effect of carrier and fuel gas on the detector's sensitivity to nitrogen-containing molecules and discriminating performance toward biological matrix interferences. Application of simple extraction techniques, combined with rapid derivatization procedures, computer data acquisition, and reduction of chromatographic data are presented. Results show that this system approach allows for the screening of several drugs and their metabolites in a short amount of time. The reliability and stability of the system have been tested by analyzing several thousand samples for doping control at major international sporting events and for monitoring drug intake in addicts participating in a rehabilitation program. Results indicate that these techniques can be used and adapted to many different analytical toxicology situations.

  14. Domestic Preparedness Program: Evaluation of the Agilent Gas Chromatograph - Flame Photometric Detector/Mass Selective Detector (GC-FPD/MSD) System Against Chemical Warfare Agents Summary Report

    Longworth, Terri

    2003-01-01

    This report characterizes the chemical warfare agent (CWA) detection potential of the commercially available Agilent gas chromatograph-flame photometric detector/mass selective detector (GC-FPD/MSD...

  15. Rapid process development of chromatographic process using direct analysis in real time mass spectrometry as a process analytical technology tool.

    Yan, Binjun; Chen, Teng; Xu, Zhilin; Qu, Haibin

    2014-06-01

    The concept of quality by design (QbD) is widely applied in the process development of pharmaceuticals. However, the additional cost and time have caused some resistance about QbD implementation. To show a possible solution, this work proposed a rapid process development method, which used direct analysis in real time mass spectrometry (DART-MS) as a process analytical technology (PAT) tool for studying the chromatographic process of Ginkgo biloba L., as an example. The breakthrough curves were fast determined by DART-MS at-line. A high correlation coefficient of 0.9520 was found between the concentrations of ginkgolide A determined by DART-MS and HPLC. Based on the PAT tool, the impacts of process parameters on the adsorption capacity were discovered rapidly, which showed a decreased adsorption capacity with the increase of the flow rate. This work has shown the feasibility and advantages of integrating PAT into QbD implementation for rapid process development. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Rapid determination of methanol in black liquors by full evaporation headspace gas chromatography.

    Li, Hailong; Zhan, Huaiyu; Fu, Shiyu; Liu, Mengru; Chai, Xin-Sheng

    2007-12-14

    This paper reported a full evaporation headspace gas chromatographic (GC) technique for determination of methanol content in black liquors (pulping spent liquor). In this method, a very small volume (10-20 microL) of liquor sample is introduced into a headspace sample vial (20 mL) and heated up to a temperature of 105 degrees C. A near-complete mass transfer of methanol from the liquid phase to vapor phase (headspace), i.e., a full evaporation, can be achieved within 3 min. The methanol in the headspace of the vial is then measured by GC. The present method is simple, rapid and accurate.

  17. Development of new process network for gas chromatograph and analyzers connected with SCADA system and Digital Control Computers at Cernavoda NPP Unit 1

    Deneanu, Cornel; Popa Nemoiu, Dragos; Nica, Dana; Bucur, Cosmin

    2007-01-01

    The continuous monitoring of gas mixture concentrations (deuterium/ hydrogen/oxygen/nitrogen) accumulated in 'Moderator Cover Gas', 'Liquid Control Zone' and 'Heat Transport D 2 O Storage Tank Cover Gas', as well as the continuous monitoring of Heavy Water into Light Water concentration in 'Boilers Steam', 'Boilers Blown Down', 'Moderator heat exchangers', and 'Recirculated Water System', sensing any leaks of Cernavoda NPP U1 led to requirement of developing a new process network for gas chromatograph and analyzers connected to the SCADA system and Digital Control Computers of Cernavoda NPP Unit 1. In 2005 it was designed and implemented the process network for gas chromatograph which connected the gas chromatograph equipment to the SCADA system and Digital Control Computers of the Cernavoda NPP Unit 1. Later this process network for gas chromatograph has been extended to connect the AE13 and AE14 Fourier Transform Infrared (FTIR) analyzers with either. The Gas Chromatograph equipment measures with best accuracy the mixture gases (deuterium/ hydrogen/oxygen/nitrogen) concentration. The Fourier Transform Infrared (FTIR) AE13 and AE14 Analyzers measure the Heavy Water into Light Water concentration in Boilers Steam, Boilers BlownDown, Moderator heat exchangers, and Recirculated Water System, monitoring and signaling any leaks. The Gas Chromatograph equipment and Fourier Transform Infrared (FTIR) AE13 and AE14 Analyzers use the new OPC (Object Link Embedded for Process Control) technologies available in ABB's VistaNet network for interoperability with automation equipment. This new process network has interconnected the ABB chromatograph and Fourier Transform Infrared analyzers with plant Digital Control Computers using new technology. The result was an increased reliability and capability for inspection and improved system safety

  18. Evaluation of rapid immuno chromatographic assay kit using monoclonal mpt64 antibodies for identification of mycobacterium tuberculosis complex

    Satti, L.; Ikram, A.; Malik, N.

    2010-01-01

    To evaluate the performance of rapid immuno chromatographic kit MPT64 Ag for the identification of Mycobacterium tuberculosis complex from various Mycobacterium tuberculosis culture positive specimens. Department of Microbiology, Armed Forces Institute of Pathology Rawalpindi, from August 2008 through March 2009. Eighty four Mycobacterium tuberculosis positive cultures on I BACTEC 460 and MGIT 960, one ATCC 25177 MTB strain, three institutional control MTB strains, two institutional control MOTT strains and 20 different bacterial isolates were tested. Tests were performed according to the instructional manual. Out of total 84 tested samples, MPT64 showed positive result in 80 cultures. Only four positive cultures did not display any band on MPT64 kit. These four strains were reconfirmed as Mycobacterium tuberculosis by PCR method. MOTT control strains and all the 20 bacterial isolates were negative for band. The sensitivity and specificity of ICT assay in our study was 95.2% and 100% respectively. Rapid MPT64 Kit is a good diagnostic tool to differentiate between Mycobacterium tuberculosis complex and MOTT with 100% specificity. The technique is simple and can provide prompt information to the clinicians to initiate early and appropriate antituberculosis therapy. (author)

  19. Gas Chromatograph Method Optimization Trade Study for RESOLVE: 20-meter Column v. 8-meter Column

    Huz, Kateryna

    2014-01-01

    RESOLVE is the payload on a Class D mission, Resource Prospector, which will prospect for water and other volatile resources at a lunar pole. The RESOLVE payload's primary scientific purpose includes determining the presence of water on the moon in the lunar regolith. In order to detect the water, a gas chromatograph (GC) will be used in conjunction with a mass spectrometer (MS). The goal of the experiment was to compare two GC column lengths and recommend which would be best for RESOLVE's purposes. Throughout the experiment, an Inficon Fusion GC and an Inficon Micro GC 3000 were used. The Fusion had a 20m long column with 0.25mm internal diameter (Id). The Micro GC 3000 had an 8m long column with a 0.32mm Id. By varying the column temperature and column pressure while holding all other parameters constant, the ideal conditions for testing with each column length in their individual instrument configurations were determined. The criteria used for determining the optimal method parameters included (in no particular order) (1) quickest run time, (2) peak sharpness, and (3) peak separation. After testing numerous combinations of temperature and pressure, the parameters for each column length that resulted in the most optimal data given my three criteria were selected. The ideal temperature and pressure for the 20m column were 95 C and 50psig. At this temperature and pressure, the peaks were separated and the retention times were shorter compared to other combinations. The Inficon Micro GC 3000 operated better at lower temperature mainly due to the shorter 8m column. The optimal column temperature and pressure were 70 C and 30psig. The Inficon Micro GC 3000 8m column had worse separation than the Inficon Fusion 20m column, but was able to separate water within a shorter run time. Therefore, the most significant tradeoff between the two column lengths was peak separation of the sample versus run time. After performing several tests, it was concluded that better

  20. A low thermal mass fast gas chromatograph and its implementation in fast gas chromatography mass spectrometry with supersonic molecular beams.

    Fialkov, Alexander B; Moragn, Mati; Amirav, Aviv

    2011-12-30

    A new type of low thermal mass (LTM) fast gas chromatograph (GC) was designed and operated in combination with gas chromatography mass spectrometry (GC-MS) with supersonic molecular beams (SMB), including GC-MS-MS with SMB, thereby providing a novel combination with unique capabilities. The LTM fast GC is based on a short capillary column inserted inside a stainless steel tube that is resistively heated. It is located and mounted outside the standard GC oven on its available top detector port, while the capillary column is connected as usual to the standard GC injector and supersonic molecular beam interface transfer line. This new type of fast GC-MS with SMB enables less than 1 min full range temperature programming and cooling down analysis cycle time. The operation of the fast GC-MS with SMB was explored and 1 min full analysis cycle time of a mixture of 16 hydrocarbons in the C(10)H(22) up to C(44)H(90) range was achieved. The use of 35 mL/min high column flow rate enabled the elution of C(44)H(90) in less than 45 s while the SMB interface enabled splitless acceptance of this high flow rate and the provision of dominant molecular ions. A novel compound 9-benzylazidanthracene was analyzed for its purity and a synthetic chemistry process was monitored for the optimization of the chemical reaction yield. Biodiesel was analyzed in jet fuel (by both GC-MS and GC-MS-MS) in under 1 min as 5 ppm fatty acid methyl esters. Authentic iprodion and cypermethrin pesticides were analyzed in grapes extract in both full scan mode and fast GC-MS-MS mode in under 1 min cycle time and explosive mixture including TATP, TNT and RDX was analyzed in under 1 min combined with exhibiting dominant molecular ion for TATP. Fast GC-MS with SMB is based on trading GC separation for speed of analysis while enhancing the separation power of the MS via the enhancement of the molecular ion in the electron ionization of cold molecules in the SMB. This paper further discusses several features of

  1. An automated multidimensional preparative gas chromatographic system for isolation and enrichment of trace amounts of xenon from ambient air.

    Larson, Tuula; Östman, Conny; Colmsjö, Anders

    2011-04-01

    The monitoring of radioactive xenon isotopes is one of the principal methods for the detection of nuclear explosions in order to identify clandestine nuclear testing. In this work, a miniaturized, multiple-oven, six-column, preparative gas chromatograph was constructed in order to isolate trace quantities of radioactive xenon isotopes from ambient air, utilizing nitrogen as the carrier gas. The multidimensional chromatograph comprised preparative stainless steel columns packed with molecular sieves, activated carbon, and synthetic carbon adsorbents (e.g., Anasorb®-747 and Carbosphere®). A combination of purification techniques--ambient adsorption, thermal desorption, back-flushing, thermal focusing, and heart cutting--was selectively optimized to produce a well-defined xenon peak that facilitated reproducible heart cutting and accurate quantification. The chromatographic purification of a sample requires approximately 4 h and provides complete separation of xenon from potentially interfering components (such as water vapor, methane, carbon dioxide, and radon) with recovery and accuracy close to 100%. The preparative enrichment process isolates and concentrates a highly purified xenon gas fraction that is suitable for subsequent ultra-low-level γ-, ß/γ-spectroscopic or high-resolution mass spectrometric measurement (e.g., to monitor the gaseous fission products of nuclear explosions at remote locations). The Xenon Processing Unit is a free-standing, relatively lightweight, and transportable system that can be interfaced to a variety of sampling and detection systems. It has a relatively inexpensive, rugged, and compact modular (19-inch rack) design that provides easy access to all parts for maintenance and has a low power requirement.

  2. Automated-process gas-chromatograph system for use in accelerated corrosion testing of HTGR core-support posts

    Harper, R.E.; Herndon, P.G.

    1982-01-01

    An automated-process gas chromatograph is the heart of a gaseous-impurities-analysis system developed for the Oak Ridge National Laboratory Core Support Performance Test, at which graphite core-support posts for high-temperature gas-cooled fission reactors are being subjected to accelerated corrosion tests under tightly controlled conditions of atmosphere and temperature. Realistic estimation of in-core corrosion rates is critically dependent upon the accurate measurement of low concentrations of CO, CO 2 , CH 4 , H 2 , and O 2 in the predominantly helium atmosphere. In addition, the capital and labor investment associated with each test puts a premium upon the reliability of the analytical system, as excessive downtime or failure to obtain accurate data would result in unacceptable costs and schedule delays. After an extensive survey of available measurement techniques, gas chromatography was chosen for reasons of accuracy, flexibility, good-performance record, and cost

  3. In situ derivatization and hollow fiber membrane microextraction for gas chromatographic determination of haloacetic acids in water

    Varanusupakul, Pakorn; Vora-adisak, Narongchai; Pulpoka, Bancha

    2007-01-01

    An alternative method for gas chromatographic determination of haloacetic acids (HAAs) in water using direct derivatization followed by hollow fiber membrane liquid-phase microextraction (HF-LPME) has been developed. The method has improved the sample preparation step according to the conventional US EPA Method 552.2 by combining the derivatization and the extraction into one step prior to determination by gas chromatography electron captured detector (GC-ECD). The HAAs were derivatized with acidic methanol into their methyl esters and simultaneously extracted with supported liquid hollow fiber membrane in headspace mode. The derivatization was attempted directly in water sample without sample evaporation. The HF-LPME was performed using 1-octanol as the extracting solvent at 55 deg. C for 60 min with 20% Na 2 SO 4 . The linear calibration curves were observed for the concentrations ranging from 1 to 300 μg L -1 with the correlation coefficients (R 2 ) being greater than 0.99. The method detection limits of most analytes were below 1 μg L -1 except DCAA and MCAA that were 2 and 18 μg L -1 , respectively. The recoveries from spiked concentration ranged from 97 to 109% with %R.S.D. less than 12%. The method was applied for determination of HAAs in drinking water and tap water samples. The method offers an easy one step high sample throughput sample preparation for gas chromatographic determination of haloacetic acids as well as other contaminants in water

  4. Incident at university research facility - melt down of gas chromatograph evaporation block and failure of a passive safety barrier

    Jensen, Niels; Jørgensen, Sten Bay

    2014-01-01

    Two incidents are described highlighting the importance of process hazard analysis in university laboratories. In the first incident, an online gas chromatograph (GC) was being developed. A complete meltdown of the heating blog was experienced during testing because the PC had failed to turn off...... the heating of the evaporation circuit. There had been no design review of the GC, nor any code review of the software controlling the GC. Neither had there been any management of change review for the introduction of the GC in the pilot plant environment, and so the GC had been introduced without any...

  5. A high-throughput headspace gas chromatographic technique for the determination of nitrite content in water samples.

    Zhang, Shu-Xin; Peng, Rong; Jiang, Ran; Chai, Xin-Sheng; Barnes, Donald G

    2018-02-23

    This paper reports on a high-throughput headspace gas chromatographic method (HS-GC) for the determination of nitrite content in water sample, based on GC measurement of cyclohexene produced from the reaction between nitrite and cyclamate in a closed vial. The method has a relative standard deviation of water samples. In short, the present HS-GC method is simple, accurate, and sensitive, and it is very suitable to be used in the batch sample testing. Copyright © 2018 Elsevier B.V. All rights reserved.

  6. Direct chromatographic methods for the rapid determination of homogentisic acid in strawberry tree (Arbutus unedo L.) honey.

    Scanu, Roberta; Spano, Nadia; Panzanelli, Angelo; Pilo, Maria I; Piu, Paola C; Sanna, Gavino; Tapparo, Andrea

    2005-10-07

    Two rapid and direct chromatographic methods based on reverse phase-high performance liquid chromatography (RP-HPLC) and ion chromatography (IC) were developed for the determination of homogentisic acid (HA) in honey. This is the marker of the botanic origin of strawberry tree honey. The methods were validated and tested using 22 samples from Sardinia, Italy. The IC method is faster than the RP-HPLC one (6 min versus 13 min of total run), but it is slightly less sensitive (the limit of detection (LOD), is 26 mg kg(-1) versus 15 mg kg(-1)) and reproducible (relative standard deviation, RSD, of 10.4 and 4.4%, respectively). The whole dataset of validation parameters allows both the proposed methods to be considered as bias-free (by recovery tests, comparison of analytical results of the two independent methods and analysis of a synthetic sample) and precise (both the techniques show a repeatability better than 2% repeatability in the range between 70 and 600 mg kg(-1)).

  7. Rapid ion-pair liquid chromatographic method for the determination of fenbendazole marker residue in fermented dairy products.

    Vousdouka, Venetia I; Papapanagiotou, Elias P; Angelidis, Apostolos S; Fletouris, Dimitrios J

    2017-04-15

    A simple, rapid and sensitive liquid chromatographic method that allows for the quantitative determination of fenbendazole residues in fermented dairy products is described. Samples were extracted with a mixture of acetonitrile-phosphoric acid and the extracts were defatted with hexane to be further partitioned into ethyl acetate. The organic layer was evaporated to dryness and the residue was reconstituted in mobile phase. Separation of fenbendazole and its sulphoxide, sulphone, and p-hydroxylated metabolites was carried out isocratically with a mobile phase containing both positively and negatively charged pairing ions. Overall recoveries ranged from 79.8 to 88.8%, while precision data, based on within and between days variations, suggested an overall relative standard deviation of 6.3-11.0%. The detection and quantification limits were lower than 9 and 21μg/kg, respectively. The method has been successfully applied to quantitate fenbendazole residues in Feta cheese and yoghurt made from spiked and incurred ovine milk. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Further Validation of a Rapid Screening Semiquantitative Thin-Layer Chromatographic Method for Marketed Antimalarial Medicines for Adoption in Malawi

    Dorcas Osei-Safo

    2018-01-01

    Full Text Available A recently developed semiquantitative thin-layer chromatographic (SQ-TLC assay has been employed in postmarketing surveillance of antimalarial medicines used in Malawi prior to HPLC assay. Both methods gave analogous results in a significant majority of the samples, with a good correlation (r = 0.9012 for the active pharmaceutical ingredients of the dosage forms assayed. Artemether-containing medicines had the highest percentage (92.67% of samples with comparable results for both assays. The lowest percentage (66.67% was observed in artesunate-containing medicines. The SQ-TLC method was validated for specificity, accuracy, precision, linearity, and stability according to the International Conference on Harmonisation guidelines, with the results falling within acceptable limits. For specificity, retention factor values of the test samples and reference standards were comparable, while accuracy and precision of 91.1 ± 5.7% were obtained for all samples. The method was linear in the range 1.0–2.0 µg/spot with a correlation coefficient of r = 0.9783. Stability tests also fell within acceptable limits. In this study, we present the validation of the SQ-TLC method and propose its adoption as a rapid screening tool for field estimation of the quality of antimalarial and other essential medicines in Malawi and other parts of the developing world prior to a more accurate HPLC assay.

  9. A gas chromatograph system for semi-continuous greenhouse gas measurements at Puy de Dôme station, Central France

    Lopez, M.; Schmidt, M.; Ramonet, M.; Bonne, J.-L.; Colomb, A.; Kazan, V.; Laj, P.; Pichon, J.-M.

    2015-03-01

    Three years of greenhouse gases measurements, obtained using a gas chromatograph (GC) system located at the Puy de Dôme station at 1465 m a.s.l. in Central France are presented. The GC system was installed in 2010 at Puy de Dôme and was designed for automatic and accurate semi-continuous measurements of atmospheric carbon dioxide, methane, nitrous oxide and sulfur hexafluoride mole fractions. We present in detail the instrumental set up and the calibration strategy, which together allow the GC to reach repeatabilities of 0.1 μmol mol-1, 1.2, 0.3 nmol mol-1 and 0.06 pmol mol-1 for CO2, CH4, N2O and SF6, respectively. Comparisons of the atmospheric time series with those obtained using other instruments shown that the GC system meets the World Meteorological Organization recommendations. The analysis of the three-year atmospheric time series revealed how the planetary boundary layer height drives the mole fractions observed at a mountain site such as Puy de Dôme where air masses alternate between the planetary boundary layer and the free troposphere. Accurate long-lived greenhouse gases measurements collocated with 222Rn measurements as an atmospheric tracer, allowed us to determine the CO2, CH4 and N2O emissions in the catchment area of the station. The derived CO2 surface flux revealed a clear seasonal cycle with net uptake by plant assimilation in the spring and net emission caused by the biosphere and burning of fossil fuel during the remainder of the year. We calculated a mean annual CO2 flux of 1150 t(CO2) km-2. The derived CH4 and N2O emissions in the station catchment area were 5.6 t(CH4) km-2 yr-1 and 1.5 t(N2O) km-2 yr-1, respectively. Our derived annual CH4 flux is in agreement with the national French inventory, whereas our derived N2O flux is five times larger than the same inventory.

  10. A single gas chromatograph for accurate atmospheric mixing ratio measurements of CO2, CH4, N2O, SF6 and CO

    van der Laan, S.; Neubert, R. E. M.; Meijer, H. A. J.; Simpson, W.R.

    2009-01-01

    We present an adapted gas chromatograph capable of measuring simultaneously and semi-continuously the atmospheric mixing ratios of the greenhouse gases CO2, CH4, N2O and SF6 and the trace gas CO with high precision and long-term stability. The novelty of our design is that all species are measured

  11. In-line gas chromatographic apparatus for measuring the hydrophobic micropore volume (HMV) and contaminant transformation in mineral micropores

    Cheng Hefa; Reinhard, Martin

    2010-01-01

    Desorption of hydrophobic organic compounds from micropores is characteristically slow compared to surface adsorption and partitioning. The slow-desorbing mass of a hydrophobic probe molecule can be used to calculate the hydrophobic micropore volume (HMV) of microporous solids. A gas chromatographic apparatus is described that allows characterization of the sorbed mass with respect to the desorption rate. The method is demonstrated using a dealuminated zeolite and an aquifer sand as the model and reference sorbents, respectively, and trichloroethylene (TCE) as the probe molecule. A glass column packed with the microporous sorbent is coupled directly to a gas chromatograph that is equipped with flame ionization and electron capture detectors. Sorption and desorption of TCE on the sorbent was measured by sampling the influent and effluent of the column using a combination of switching and injection valves. For geosorbents, the HMV is quantified based on Gurvitsch's rule from the mass of TCE desorbed at a rate that is characteristic for micropores. Instrumental requirements, design considerations, hardware details, detector calibration, performance, and data analysis are discussed along with applications. The method is novel and complements traditional vacuum gravimetric and piezometric techniques, which quantify the total pore volume under vacuum conditions. The HMV is more relevant than the total micropore volume for predicting the fate and transport of organic contaminants in the subsurface. Sorption in hydrophobic micropores strongly impacts the mobility of organic contaminants, and their chemical and biological transformations. The apparatus can serve as a tool for characterizing microprous solids and investigating contaminant-solid interactions.

  12. Proposal for data acquisition system of gas chromatograph and natural gas transfer custody via web; Proposta para um sistema de aquisicao de dados de cromatografia e medicao fiscal de gas natural via web

    Santana, Jose Paulo C.; Guimaraes, Marcelo F.; Zeitoune, Rafael J. [PETROBRAS, Rio de Janeiro, RJ (Brazil)

    2005-07-01

    In this paper, is presented a proposal of a Chromatograph and Transfer Custody Measurement Data Acquisition System through Web, complementary to the SCADA System, responsible for control and monitoring PETROBRAS Gas Pipelines, intended to comply with the requirements of the Gerencias de Qualidade e Medicao (MQD) and Planejamento Integrado da Logistica (PCL) from PETROBRAS Gas e Energia, regarding the evaluation of the quality of the natural gas that is being commercialized, as well as its billing. (author)

  13. Gas industry construction expenditures to grow rapidly

    Quarles, W.R.

    1991-01-01

    Between 1991 and 1993, the natural gas industry will invest $28.297 billion to install additional facilities for natural gas production and storage, transmission, underground storage, gas distribution and for other general expenditures, estimates the American Gas Association as shown in the 1990 Gas Facts. This is a 38% investment increase from the forecasts in the 1989 Gas Facts. This issue forecasts investments of $13.303 billion for 1991 and $18.396 billion for 1992. This issue does not include investments for 1993. In 1989, (the last figures released) the gas industry invested $7,341 billion for new transmission lines, distribution mains, underground storage, production and storage and general facilities. Included in the 1989 expenditures are: $3.980 billion in distribution facilities; $2.081 billion in gas transmission systems and $159 million in underground storage facilities. Investment in new distribution facilities in 1991 and $4.550 billion in 1993. This is a steady increase for these three years. Investments in natural gas transmission facilities show a steady increase also. In 1991, pipe line operating companies will invest $9.391 billion for new facilities, $9.005 in 1992 and $9.901 billion in 1993

  14. Rapid determination of cholesterol in milk and milk products by direct saponification and capillary gas chromatography.

    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.

  15. In situ derivatization and hollow fiber membrane microextraction for gas chromatographic determination of haloacetic acids in water

    Varanusupakul, Pakorn [Chromatography and Separation Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Patumwan, Bangkok 10330 (Thailand)], E-mail: pakorn.v@chula.ac.th; Vora-adisak, Narongchai; Pulpoka, Bancha [Chromatography and Separation Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Patumwan, Bangkok 10330 (Thailand)

    2007-08-15

    An alternative method for gas chromatographic determination of haloacetic acids (HAAs) in water using direct derivatization followed by hollow fiber membrane liquid-phase microextraction (HF-LPME) has been developed. The method has improved the sample preparation step according to the conventional US EPA Method 552.2 by combining the derivatization and the extraction into one step prior to determination by gas chromatography electron captured detector (GC-ECD). The HAAs were derivatized with acidic methanol into their methyl esters and simultaneously extracted with supported liquid hollow fiber membrane in headspace mode. The derivatization was attempted directly in water sample without sample evaporation. The HF-LPME was performed using 1-octanol as the extracting solvent at 55 deg. C for 60 min with 20% Na{sub 2}SO{sub 4}. The linear calibration curves were observed for the concentrations ranging from 1 to 300 {mu}g L{sup -1} with the correlation coefficients (R{sup 2}) being greater than 0.99. The method detection limits of most analytes were below 1 {mu}g L{sup -1} except DCAA and MCAA that were 2 and 18 {mu}g L{sup -1}, respectively. The recoveries from spiked concentration ranged from 97 to 109% with %R.S.D. less than 12%. The method was applied for determination of HAAs in drinking water and tap water samples. The method offers an easy one step high sample throughput sample preparation for gas chromatographic determination of haloacetic acids as well as other contaminants in water.

  16. Equations for nickel-chromium wire heaters of column transfer lines in gas chromatographic-electroantennographic detection (GC-EAD).

    Byers, John A

    2004-05-30

    Heating of chromatographic columns, transfer lines, and other devices is often required in neuroscience research. For example, volatile compounds passing through a capillary column of a gas chromatograph (GC) can be split, with half exiting the instrument through a heated transfer line to an insect antenna or olfactory sensillum for electroantennographic detector (GC-EAD) recordings. The heated transfer line is used to prevent condensation of various chemicals in the capillary that would otherwise occur at room temperature. Construction of such a transfer line heater is described using (80/20%) nickel-chromium heating wire wrapped in a helical coil and powered by a 120/220 V ac rheostat. Algorithms were developed in a computer program to estimate the voltage at which a rheostat should be set to obtain the desired heater temperature for a specific coil. The coil attributes (radius, width, number of loops, or length of each loop) are input by the user, as well as AWG size of heating wire and desired heater temperature. The program calculates total length of wire in the helix, resistance of the wire, amperage used, and the voltage to set the rheostat. A discussion of semiochemical isolation methods using the GC-EAD and bioassays is presented.

  17. Gas-chromatographic separation of hydrogen isotopes mixtures on capillary molecular sieve 5 A column at 173 K

    Bidica, N.; Preda, A.; Stanciu, V.

    2002-01-01

    Analysis of a gas mixture of hydrogen species, is not too easy because the differences in their physical-chemical properties are very small; the most different are their masses, and consequently most common analytical method appear to be the mass-spectrometry. However, the impossibility to distinguish between two ions (atomic or molecular) with the same mass renders this method as unapplicable. Another problem is the decay of tritium with production of 3 He. These disadvantages of mass-spectrometry have made that other analytical methods, like gas chromatography, to be considered and developed. Thus, there are many papers about various chromatographic columns especially prepared for hydrogen species separation but the preparation and treatment of these columns are very difficult to reproduce. Besides these, there are two other main disadvantages: column operating temperature is very low and long retention times for hydrogen species (more than half an hour) are required. However, the gas-chromatography method still remains an appropriate one. The method described in this paper was based on using a capillary molecular sieve 5A column which has been operated for this kind of separation. The retention times were relatively short, about 8-9 minutes. The carrier gas was Ne and the detector - TCD. In the paper chromatograms for various carrier flow rates and various hydrogen isotope mixtures are presented. The results demonstrated a quite good efficiency for H 2 , HD, D 2 and a not very good one for orthoH 2 -paraH 2 . (authors)

  18. Gas chromatographic studies of the relative retention of the sulfur isotopes in carbonyl sulfide, carbon disulfide, and sulfur dioxide

    Fetzer, J.C.; Rogers, L.B.

    1980-01-01

    A precision gas chromatograph, coupled to a quadrupole mass spectrometer and an on-line computer, was used to study the fractionation on Porasil A of the 32 S/ 34 S isotopic pair in a variety of sulfur-containing molecules. Carbonyl sulfide (COS) yielded an average α value of 1.00074 +- 0.00017 (standard deviation) for the temperature range 25 0 C to 75 0 C. The carbon disulfide (CS 2 ) value was 1.00069 +- 0.00023 for the range 53 0 C to 103 0 C, and that for sulfur dioxide (SO 2 ) was 1.00090 +- 0.00018 for the range 62 0 C to 112 0 C. Differential thermodynamic data have been reported. A Porapak Q column showed no fractionation of this isotopic pair in these three molecules

  19. In-line gas chromatographic apparatus for measuring the hydrophobic micropore volume (HMV) and contaminant transformation in mineral micropores.

    Cheng, Hefa; Reinhard, Martin

    2010-07-15

    Desorption of hydrophobic organic compounds from micropores is characteristically slow compared to surface adsorption and partitioning. The slow-desorbing mass of a hydrophobic probe molecule can be used to calculate the hydrophobic micropore volume (HMV) of microporous solids. A gas chromatographic apparatus is described that allows characterization of the sorbed mass with respect to the desorption rate. The method is demonstrated using a dealuminated zeolite and an aquifer sand as the model and reference sorbents, respectively, and trichloroethylene (TCE) as the probe molecule. A glass column packed with the microporous sorbent is coupled directly to a gas chromatograph that is equipped with flame ionization and electron capture detectors. Sorption and desorption of TCE on the sorbent was measured by sampling the influent and effluent of the column using a combination of switching and injection valves. For geosorbents, the HMV is quantified based on Gurvitsch's rule from the mass of TCE desorbed at a rate that is characteristic for micropores. Instrumental requirements, design considerations, hardware details, detector calibration, performance, and data analysis are discussed along with applications. The method is novel and complements traditional vacuum gravimetric and piezometric techniques, which quantify the total pore volume under vacuum conditions. The HMV is more relevant than the total micropore volume for predicting the fate and transport of organic contaminants in the subsurface. Sorption in hydrophobic micropores strongly impacts the mobility of organic contaminants, and their chemical and biological transformations. The apparatus can serve as a tool for characterizing microporous solids and investigating contaminant-solid interactions. 2010 Elsevier B.V. All rights reserved.

  20. In-line gas chromatographic apparatus for measuring the hydrophobic micropore volume (HMV) and contaminant transformation in mineral micropores

    Cheng Hefa [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Reinhard, Martin, E-mail: reinhard@stanford.edu [Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020 (United States)

    2010-07-15

    Desorption of hydrophobic organic compounds from micropores is characteristically slow compared to surface adsorption and partitioning. The slow-desorbing mass of a hydrophobic probe molecule can be used to calculate the hydrophobic micropore volume (HMV) of microporous solids. A gas chromatographic apparatus is described that allows characterization of the sorbed mass with respect to the desorption rate. The method is demonstrated using a dealuminated zeolite and an aquifer sand as the model and reference sorbents, respectively, and trichloroethylene (TCE) as the probe molecule. A glass column packed with the microporous sorbent is coupled directly to a gas chromatograph that is equipped with flame ionization and electron capture detectors. Sorption and desorption of TCE on the sorbent was measured by sampling the influent and effluent of the column using a combination of switching and injection valves. For geosorbents, the HMV is quantified based on Gurvitsch's rule from the mass of TCE desorbed at a rate that is characteristic for micropores. Instrumental requirements, design considerations, hardware details, detector calibration, performance, and data analysis are discussed along with applications. The method is novel and complements traditional vacuum gravimetric and piezometric techniques, which quantify the total pore volume under vacuum conditions. The HMV is more relevant than the total micropore volume for predicting the fate and transport of organic contaminants in the subsurface. Sorption in hydrophobic micropores strongly impacts the mobility of organic contaminants, and their chemical and biological transformations. The apparatus can serve as a tool for characterizing microprous solids and investigating contaminant-solid interactions.

  1. Gas chromatographic-mass spectrometric analysis of biomarkers related to folate and cobalamin status in human serum after dimercaptopropanesulfonate reduction and heptafluorobutyl chloroformate derivatization

    Šimek, Petr; Hušek, Petr; Zahradníčková, Helena

    2008-01-01

    Roč. 80, č. 15 (2008), s. 5776-5782 ISSN 0003-2700 R&D Projects: GA ČR GA303/06/1674 Institutional research plan: CEZ:AV0Z50070508 Keywords : biomarkers * gas chromatographic * chloroformate derivatization Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 5.712, year: 2008

  2. Evaluation of a gas chromatograph with a novel surface acoustic wave detector (SAW GC) for screening of volatile organic compounds in Hanford waste tank samples

    Lockrem, L.L.

    1998-01-01

    A novel instrument, a gas chromatograph with a Surface Acoustic Wave Detector (SAW GC), was evaluated for the screening of organic compounds in Hanford tank headspace vapors. Calibration data were developed for the most common organic compounds, and the accuracy and precision were measured with a certified standard. The instrument was tested with headspace samples collected from seven Hanford waste tanks

  3. Rapid gas development in the Fayetteville shale basin, Arkansas

    Advances in drilling and extraction of natural gas have resulted in rapid expansion of wells in shale basins. The rate of gas well installation in the Fayetteville shale is 774 wells a year since 2005 with thousands more planned. The Fayetteville shale covers 23,000 km2 although ...

  4. Comparison of radioimmunoassay and gas chromatographic mass spectrometric assay for d-amphetamine

    Powers, K.H.; Ebert, M.H.

    1979-01-01

    Quantification of low levels of psychotropic drugs (10 -7 to 10 -9 g ml -1 ) in small volumes of plasma requires sensitive and accurate methods. Validation of these methods is best achieved by comparing results obtained using several techniques. In this study, amphetamine levels in plasma were measured using gas chromatography mass spectrometry and radioimmunoassay. Correlation of the results obtained by the two methods was found to be positive and high (R = 0.9822). The average coefficient of variation between assays for gas chromatography mass spectrometry was 5.8% and for radioimmunoassay was 12.3%, while the average coefficient of variation within assays for gas chromatography mass spectrometry was 4.9% and for radioimmunoassay 6.9%. Although gas chromatography mass spectrometry was 1.9 times more sensitive than radioimmunoassay, for most purposes, the convenience of the radioimmunoassay method outweighs the technical superiority of gas chromatography mass spectrometry. (author)

  5. Effects of γ-irradiation on caprolactam level from multilayer PA-6 films for food packaging: Development and validation of a gas chromatographic method

    Araujo, Henrique Peres; Felix, Juliana Silva; Manzoli, Jose Eduardo; Padula, Marisa; Monteiro, Magali

    2008-01-01

    A gas chromatographic method to determine caprolactam in multilayer PA-6 films used for meat foodstuffs and cheese was developed and validated. A wide linear range (0.8-400 μg/ml), RSD≤4.1% and recovery higher than 90.0% were obtained for the chromatographic system, while precision and accuracy of the method showed RSD≤3.8%, recovery from 95.5-100.0% and LOQ of 32 μg/g. Irradiated (3, 7 and 12 kGy) and non-irradiated commercial films were analyzed. Most of them increased caprolactam levels with the increase of irradiation doses

  6. Effects of {gamma}-irradiation on caprolactam level from multilayer PA-6 films for food packaging: Development and validation of a gas chromatographic method

    Araujo, Henrique Peres; Felix, Juliana Silva [Department of Food and Nutrition, School of Pharmaceutical Science, Sao Paulo State University, PO Box 502, 14801-902 Araraquara, SP (Brazil); Manzoli, Jose Eduardo [Nuclear and Energetic Research Institute (IPEN), Sao Paulo, SP (Brazil); Padula, Marisa [Packaging Technology Center/Food Technology Institute (CETEA/ITAL), Campinas, SP (Brazil); Monteiro, Magali [Department of Food and Nutrition, School of Pharmaceutical Science, Sao Paulo State University, PO Box 502, 14801-902 Araraquara, SP (Brazil)], E-mail: monteiro@fcfar.unesp.br

    2008-07-15

    A gas chromatographic method to determine caprolactam in multilayer PA-6 films used for meat foodstuffs and cheese was developed and validated. A wide linear range (0.8-400 {mu}g/ml), RSD{<=}4.1% and recovery higher than 90.0% were obtained for the chromatographic system, while precision and accuracy of the method showed RSD{<=}3.8%, recovery from 95.5-100.0% and LOQ of 32 {mu}g/g. Irradiated (3, 7 and 12 kGy) and non-irradiated commercial films were analyzed. Most of them increased caprolactam levels with the increase of irradiation doses.

  7. Chromatographic separations of stereoisomers

    Souter, R.W.

    1985-01-01

    This text covers both diastereomers and enantiomers; describes techniques for GC, HPLC, and other chromatographic methods; and tabulates results of various applications by both techniques and compound class. It provides current knowledge about separation mechanisms and interactions of asymmetric molecules, as well as experimental and commercial materials such as columns, instruments, and derivatization reagents. The contents also include stereoisomer separations by gas chromatography. Stereoisomer separations by high-performance liquid chromatography. Stereoisomer separations by other chromatographic techniques.

  8. Gas Chromatographic Determination of Methyl Salicylate in Rubbing Alcohol: An Experiment Employing Standard Addition.

    Van Atta, Robert E.; Van Atta, R. Lewis

    1980-01-01

    Provides a gas chromatography experiment that exercises the quantitative technique of standard addition to the analysis for a minor component, methyl salicylate, in a commercial product, "wintergreen rubbing alcohol." (CS)

  9. Evaluation of highly polar ionic liquid gas chromatographic column for the determination of the fatty acids in milk fat.

    Delmonte, Pierluigi; Fardin-Kia, Ali Reza; Kramer, John K G; Mossoba, Magdi M; Sidisky, Len; Tyburczy, Cynthia; Rader, Jeanne I

    2012-04-13

    The SLB-IL111, a new ionic liquid capillary column for gas chromatography available from Supelco Inc., was recently shown to provide enhanced separation of unsaturated geometric and positional isomers of fatty acid (FAs) when it was compared to cyanopropylsiloxane (CPS) columns currently recommended for the analysis of fatty acid methyl esters (FAMEs). A 200 m SLB-IL111 capillary column, operated under a combined temperature and eluent flow gradient, was successfully used to resolve most of the FAs contained in milk fat in a single 80 min chromatographic separation. The selected chromatographic conditions provided a balanced, simultaneous separation of short-chain (from 4:0), long-chain polyunsaturated fatty acids (PUFAs), and most of the unsaturated FA positional/geometric isomers contained in milk fat. Among the monounsaturated fatty acids (MUFAs), these conditions separated t11-18:1 and t10-18:1 FAs, the two most abundant trans fatty acids (t-FA) contained in most dairy products. These t-FAs reportedly have different biological activities. The conjugated linoleic acid (CLA) isomers commonly found in dairy products were separated from each other, including t7,c9-18:2 from c9,t11-18:2, which eliminated the need for their complementary silver ion HPLC analysis. The application of the SLB-IL111 column provided a complementary elution profile of FAMEs to those obtained by CPS columns, allowing for a more comprehensive FA analysis of total milk fat. The FAMEs were identified by the use of available reference materials, previously synthesized and characterized reference mixtures, and prior separations of the milk fat FAMEs by silver ion chromatography based on the number/geometry of double bonds. Published by Elsevier B.V.

  10. Gas chromatographic analysis of dimethyltryptamine and beta-carboline alkaloids in ayahuasca, an Amazonian psychoactive plant beverage.

    Pires, Ana Paula Salum; De Oliveira, Carolina Dizioli Rodrigues; Moura, Sidnei; Dörr, Felipe Augusto; Silva, Wagner Abreu E; Yonamine, Mauricio

    2009-01-01

    Ayahuasca is obtained by infusing the pounded stems of Banisteriopsis caapi in combination with the leaves of Psychotria viridis. P. viridis is rich in the psychedelic indole N,N-dimethyltryptamine, whereas B. caapi contains substantial amounts of beta-carboline alkaloids, mainly harmine, harmaline and tetrahydroharmine, which are monoamine-oxidase inhibitors. Because of differences in composition in ayahuasca preparations, a method to measure their main active constituents is needed. To develop a gas chromatographic method for the simultaneous determination of dimethyltryptamine and the main beta-carbolines found in ayahuasca preparations. The alkaloids were extracted by means of solid phase extraction (C(18)) and detected by gas chromatography with nitrogen/phosphorous detector. The lower limit of quantification (LLOQ) was 0.02 mg/mL for all analytes. The calibration curves were linear over a concentration range of 0.02-4.0 mg/mL (r(2 )> 0.99). The method was also precise (RSD ayahuasca was developed and validated. The method can be useful to estimate administered doses in animals and humans for further pharmacological and toxicological investigations of ayahuasca. Copyright (c) 2009 John Wiley & Sons, Ltd.

  11. Gas-liquid chromatographic determination of aniline metabolites of substituted urea and carbamate herbicides in aqueous solution.

    Hargesheimer, E E; Coutts, R T; Pasutto, F M

    1981-07-01

    A simple gas-liquid chromatographic (GLC) method has been developed which provides sensitivity and specificity for the analysis of complex mixtures of the commonly occurring herbicide metabolites aniline, 3-chloroaniline, 4-chloroaniline, 4-bromoaniline, and 3-chloro-4-methylaniline. All of these anilines react with acetic anhydride directly in basified aqueous solution. Further reaction of the acetylated anilines with trifluoroacetic anhydride gave diacyl derivatives which were readily resolved by gas chromatography. The structures of the N-acetylated and N-trifluoroacetylated derivatives of benzylamine (internal standard) and the anilines were confirmed by GLC-mass spectrometry. In distilled water the minimum detectable concentrations of aniline and the substituted anilines, using electron capture GLC, are 0.1 nmole/100 mL and 0.05 nmole/100 mL, respectively. The detection limit for the anilines is 1 nmole/100 mL distilled water, using GLC with flame ionization detection. The technique was applied to the determination of anilines added to urine samples obtained from the general population.

  12. Gas chromatograph study of bitumen from oil shale of Amman Formation (upper cretaceous), NW Jordan

    Darwish, H.; Mustafa, H.

    1997-01-01

    The extractable organic matter of seven outcrop samples of Amman Formation Oil Shale have been analysed by Gas Chromatography (GC). The bitumen is rich in heterocompounds contents (> 60 wt%). Gas chromatograms show a predominance of iosprenoids, specially phytane over n-alkanes, and low carbon preference index (CPI). This indicates that the organic matter is immature, and its origin is mainly of marine organisms. These rocks could be possible source rocks due to the high content of hydrocarbon. (authors). 22 refs., 4 figs. 3 tabs

  13. Environmental Technology Verification Report. Field Portable Gas Chromatograph/Mass Spectrometer. Viking Instruments Corporation SpectraTrak (Trademark) 672

    Enfield, Wayne

    1997-01-01

    .... This self-contained, field transportable system, whose design has been adapted from laboratory technology, uses a contained, chromatographic column and accompanying mass spectrometer to provide...

  14. A mobile automatic gas chromatograph system to measure CO2, CH4 and N2O fluxes from soil in the field

    Silvola, J.; Martikainen, P.; Nykaenen, H.

    1992-01-01

    A caravan has been converted into mobile laboratory for measuring fluxes of CO 2 , CH 4 and N 2 O from the soil in the field. The caravan was equipped with a gas chromatograph fitted with TC-, FI- and EC-detectors, and a PC controlled data logger. The gas collecting chambers can be used up to 50 m from the caravan. The closing and opening of the chambers, as well as the flows of sample gases from chambers to the gas chromatograph. is pneumatically regulated. Simultaneous recordings of temperature, light intensity and the depth of water table are made. The system has been used for two months in 1992, and some preliminary results are presented

  15. Large-volume injection in gas chromatographic trace analysis using temperature-programmable (PTV) injectors

    Mol, J.G.J.; Janssen, J.G.M.; Cramers, C.A.M.G.; Brinkman, U.A.T.

    1996-01-01

    The use of programmed-temperature vaporising (PTV) injectors for large-volume injection in capillary gas chromatography is briefly reviewed. The principles and optimisation of large-volume PTV injection are discussed. Guidelines are given for selection of the PTV conditions and injection mode for

  16. High-resolution gas chromatographic analysis of polycyclic aromatic hydrocarbons and aliphatic hydrocarbons

    Perez, M.; Gonzalez, D.

    1988-01-01

    A study of the analysis by gas chromatography of aromatic polycyclic hydrocarbons and aliphatic hydrocarbons is presented. The separation has been carried out by glass and fused silica capillary column in two different polar stationary phases OV-1 and SE-54. The limitation and the advantages of the procedure are discussed in terms of separation, sensitivity and precision. (Author) 20 refs

  17. On-line gas chromatographic studies of rutherfordium (Element 104), hahnium (Element 105), and homologs

    Kadkhodayan, B.

    1993-05-01

    Gas-phase isothermal chromatogaphy is a method by which volatile compounds of different chemical elements can be separated according to their volatilities. The technique, coupled with theoretical modeling of the processes occurring in the chromatogaphy column, provides accurate determination of thermodynamic properties (e.g., adsorption enthalpies) for compounds of elements, such as the transactinides, which can only be produced on an atom-at-a-time basis. In addition, the chemical selectivity of the isothermal chromatogaphy technique provides the decontamination from interfering activities necessary for the determination of the nuclear decay properties of isotopes of the transactinide elements. Volatility measurements were performed on chloride species of Rf and its group 4 homologs, Zr and Hf, as well as Ha and its group 5 homologs, Nb and Ta. Adsorption enthalpies were calculated for all species using a Monte Carlo code simulation based on a microscopic model for gas thermochromatography in open columns with laminar flow of the carrier gas. Preliminary results are presented for Zr- and Nb-bromides

  18. Effects of Gas Dynamics on Rapidly Collapsing Bubbles

    Bauman, Spenser; Fomitchev-Zamilov, Max

    2013-01-01

    The dynamics of rapidly collapsing bubbles are of great interest due to the high degree of energy focusing that occurs withing the bubble. Molecular dynamics provides a way to model the interior of the bubble and couple the gas dynamics with the equations governing the bubble wall. While much theoretical work has been done to understand how a bubble will respond to an external force, the internal dynamics of the gas system are usually simplified greatly in such treatments. This paper shows ho...

  19. A novel headspace gas chromatographic method for in situ monitoring of monomer conversion during polymerization in an emulsion environment.

    Chai, Xin-Sheng; Zhong, Jin-Feng; Hu, Hui-Chao

    2012-05-18

    This paper describes a novel multiple-headspace extraction/gas chromatographic (MHE-GC) technique for monitoring monomer conversion during a polymerization reaction in a water-based emulsion environment. The polymerization reaction of methyl methacrylate (MMA) in an aqueous emulsion is used as an example. The reaction was performed in a closed headspace sample vial (as a mini-reactor), with pentane as a tracer. In situ monitoring of the vapor concentration of the tracer, employing a multiple headspace extraction (sampling) scheme, coupled to a GC, makes it possible to quantitatively follow the conversion of MMA during the early stages of polymerization. Data on the integrated amount of the tracer vapor released from the monomer droplet phase during the polymerization is described by a mathematic equation from which the monomer conversion can be calculated. The present method is simple, automated and economical, and provides an efficient tool in the investigation of the reaction kinetics and effects of the reaction conditions on the early stage of polymerization. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Interlaboratory tests to identify irradiation treatment of various foods via gas chromatographic detection of hydrocarbons, ESR spectroscopy and TL analysis

    Schreiber, G.A.; Helle, N.; Schulzki, G.; Linke, B.; Spiegelberg, A.; Mager, M.; Boegl, K.W. [BgVV - Federal Inst. for Health Protection of Consumers and Veterinary Medicine, Berlin (Germany)

    1996-12-31

    The gas chromatographic (GC) analysis of radiation-induced volatile hydrocarbons (HC) and 2-alkylcyclobutanones, the ESR spectroscopic detection of radiation-specific radicals and the thermoluminescence (TL) analysis of silicate mineral are the most important methods for identification of irradiated foods. After successful performance in interlaboratory studies on meat products, fish, spices, herbs and shells of nuts, all or some of these methods have been approved by national authorities in Germany and the United Kingdom. Recently, draft European Standards have been elaborated for approval by member states of the European Committee for Standardization (CEN). Several research laboratories have shown that these methods can be applied to various foods not yet tested in collaborative studies. However, for an effective application in food control it is necessary to prove their suitability in interlaboratory studies. Therefore, in 1993/94, various interlaboratory tests were organised by the BgVV. In an ESR spectroscopic test, shrimps and paprika powder were examined. Shrimps were also the subject of examination in a TL test. Finally, GC detection of radiation-induced hydrocarbons in the fat fraction of foods was used in another test to identify irradiated Camembert, avocado, papaya and mango. In the following paper, results of the interlaboratory tests are summarised. Detailed reports are published by this institute. (author).

  1. Interlaboratory tests to identify irradiation treatment of various foods via gas chromatographic detection of hydrocarbons, ESR spectroscopy and TL analysis

    Schreiber, G.A.; Helle, N.; Schulzki, G.; Linke, B.; Spiegelberg, A.; Mager, M.; Boegl, K.W.

    1996-01-01

    The gas chromatographic (GC) analysis of radiation-induced volatile hydrocarbons (HC) and 2-alkylcyclobutanones, the ESR spectroscopic detection of radiation-specific radicals and the thermoluminescence (TL) analysis of silicate mineral are the most important methods for identification of irradiated foods. After successful performance in interlaboratory studies on meat products, fish, spices, herbs and shells of nuts, all or some of these methods have been approved by national authorities in Germany and the United Kingdom. Recently, draft European Standards have been elaborated for approval by member states of the European Committee for Standardization (CEN). Several research laboratories have shown that these methods can be applied to various foods not yet tested in collaborative studies. However, for an effective application in food control it is necessary to prove their suitability in interlaboratory studies. Therefore, in 1993/94, various interlaboratory tests were organised by the BgVV. In an ESR spectroscopic test, shrimps and paprika powder were examined. Shrimps were also the subject of examination in a TL test. Finally, GC detection of radiation-induced hydrocarbons in the fat fraction of foods was used in another test to identify irradiated Camembert, avocado, papaya and mango. In the following paper, results of the interlaboratory tests are summarised. Detailed reports are published by this institute. (author)

  2. Gas chromatographic analysis of reactive carbonyl compounds formed from lipids upon UV-irradiation

    Dennis, K.J.; Shibamoto, T.

    1990-01-01

    Peroxidation of lipids produces carbonyl compounds; some of these, e.g., malonaldehyde and 4-hydroxynonenal, are genotoxic because of their reactivity with biological nucleophiles. Analysis of the reactive carbonyl compounds is often difficult. The methylhydrazine method developed for malonaldehyde analysis was applied to simultaneously measure the products formed from linoleic acid, linolenic acid, arachidonic acid, and squalene upon ultraviolet-irradiation (UV-irradiation). The photoreaction products, saturated monocarbonyl, alpha,beta-unsaturated carbonyls, and beta-dicarbonyls, were derivatized with methylhydrazine to give hydrazones, pyrazolines, and pyrazoles, respectively. The derivatives were analyzed by gas chromatography and gas chromatography-mass spectrometry. Lipid peroxidation products identified included formaldehyde, acetaldehyde, acrolein, malonaldehyde, n-hexanal, and 4-hydroxy-2-nonenal. Malonaldehyde levels formed upon 4 hr of irradiation were 0.06 micrograms/mg from squalene, 2.4 micrograms/mg from linolenic acid, and 5.7 micrograms/mg from arachidonic acid. Significant levels of acrolein (2.5 micrograms/mg) and 4-hydroxy-2-nonenal (0.17 micrograms/mg) were also produced from arachidonic acid upon 4 hr irradiation

  3. Gas chromatographic determination of cholesterol from food samples using extraction/saponification method

    Ali, Z.M.; Soomro, A.S.A.

    2007-01-01

    A simple and fast one-step extraction/saponification with Na/OH/KOH (Ethanolic, Sodium Hydroxide/Potassium Hydroxide was compared and validated for determination of cholesterol from locally available 10 edible oil and egg samples. The importance of the use of edible oils and eggs in routine diet is unquestionable, but presence of cholesterol is considered as a risk factor for coronary heart disease and hypertension. The lowering of cholesterol level in order to reduce the risk is widely accepted. The cholesterol in the edible oil and eggs was determined by gas chromatography, through elution from the column (2x3 mm i.d) packed with 3% OV-I01, on Chromosorb G/'NAW 80-100 mesh size at 250-300C with programmed heating rate of 3 degree C/min. Nitrogen gas flow rate was 40 ml/min. The cholesterol samples were run under the conditions after selective extraction in diethyl ether. The calibration was linear within 50-500 IJg/ml concentration range. The amount of cholesterol detected were from 12.92-18.05 mg/g in edible oil and 117.54-143.42 mg/g in egg samples with RSD 1.3-2.7%. (author)

  4. A rapid and simple procedure for monitoring valproic acid by gas chromatography

    Mohamed Said Mostafa

    2018-02-01

    Full Text Available Valproic acid (VPA, a widely used antiepileptic drug, has a narrow therapeutic range of 50-100 μg/mL and shows large individual variability. It is very important to monitor the trough VPA concentration using a reliable method. The aim of this study was to develop and validate a rapid gas chromatographic (GC technique for VPA quantification in human plasma and to compare it with the traditional immunoassay method. VPA extraction from human serum was efficient by dichloromethane and hydrochloric acid using octanoic acid as an internal standard. GC analysis was performed using a gas-chromatograph equipped with a flame ionization detector (GC/FID. VPA detection and quantification were accomplished isothermally at 135°C on a Gs-BP 100% dimethylpolysiloxane capillary column (10 m×0.53 mm ID, 2.65 μm film thickness, Supelco, Bellefonte, PA. Injection port and detector temperature were 280°C. Retention times of VPA and internal standard were 1.83 min and 2.33 min, respectively. The calibration curve was linear over the concentration range of 5-320 μg/mL, with a lower limit of detection of 1.25 μg/mL. The internal and inter-day precision was less than 5.3% and 6.1%, respectively, and the accuracy was below 2.8%. VPA recovery was 94.6%. A quick and accurate method for VPA determination in human plasma was developed and validated. It resulted sufficiently selective and sensitive.

  5. Gas supply from WCSB -- Matured more rapidly than expected

    Hawkins, D. J.

    2003-01-01

    A 2002 National Energy Board report forecast a decline in short-term gas deliverability from the Western Canadian Sedimentary Basin (WCSB) through 2004. However, this report contradicts a 1999 report which forecast a robust supply of natural gas through 2010. To obtain some clarity about the situation, this article undertakes an assessment of the information on gas supply in Alberta during the second half of the 1990s, in an attempt to account for the dramatic shift in outlook for gas supply in the WCSB by 2002. After a thorough examination of natural gas activities in the Basin during the 1990s, the author concludes that gas production in the WCSB has matured more rapidly than expected; moreover, there were clear indications that this might occur as early as the mid-1990s. Further curtailment in Alberta gas production might be expected as the debate on gas production in the Athabasca area heats up. The result of the assessment is that new resources of gas such as coal-bed methane and natural gas deposits in northeast British Columbia may come on stream, but governments will be challenged to provide incentives for sustaining gas pipeline activity in the WCSB. In the longer term there is potential for a gas pipeline from Alaska, but there is still much uncertainty about the route, line size, operating pressure, utilization of downstream pipelines and ultimate timing. In Canada, there is considerable support for a gas pipeline in the Mackenzie Valley, and plans for development are well advanced. 9 refs., 7 figs

  6. Potential for Measurement of Trace Volatile Organic Compounds in Closed Environments Using Gas Chromatograph/Differential Mobility Spectrometer

    Limero, Thomas; Cheng, Patti

    2007-01-01

    For nearly 3.5 years, the Volatile Organic Analyzer (VOA) has routinely analyzed the International Space Station (ISS) atmosphere for a target list of approximately 20 volatile organic compounds (VOCs). Additionally, an early prototype of the VOA collected data aboard submarines in two separate trials. Comparison of the data collected on ISS and submarines showed a surprising similarity in the atmospheres of the two environments. Furthermore, in both cases it was demonstrated that the VOA data can detect hardware issues unrelated to crew health. Finally, it was also clear in both operations that the VOA s size and resource consumption were major disadvantages that would restrict its use in the future. The VOA showed the value of measuring VOCs in closed environments, but it had to be shrunk if it was to be considered for future operations in these environments that are characterized by cramped spaces and limited resources. The Sionex Microanalyzer is a fraction of the VOA s size and this instrument seems capable of maintaining or improving upon the analytical performance of the VOA. The two design improvements that led to a smaller, less complex instrument are the Microanalyzer s use of recirculated air as the gas chromatograph s carrier gas and a micromachined detector. Although the VOA s ion mobility spectrometer and the Microanalyzer s differential mobility spectrometer (DMS) are related detector technologies, the DMS was more amenable to micromachining. This paper will present data from the initial assessment of the Microanalyzer. The instrument was challenged with mixtures that simulated the VOCs typically detected in closed-environment atmospheres.

  7. Technical Note: Precise quantitative measurements of total dissolved inorganic carbon from small amounts of seawater using a gas chromatographic system

    T. Hansen

    2013-10-01

    Full Text Available Total dissolved inorganic carbon (CT is one of the most frequently measured parameters used to calculate the partial pressure of carbon dioxide in seawater. Its determination has become increasingly important because of the rising interest in the biological effects of ocean acidification. Coulometric and infrared detection methods are currently favored in order to precisely quantify CT. These methods however are not sufficiently validated for CT measurements of biological experiments manipulating seawater carbonate chemistry with an extended CT measurement range (~1250–2400 μmol kg–1 compared to natural open ocean seawater (~1950–2200 μmol kg−1. The requirement of total sample amounts between 0.1–1 L seawater in the coulometric- and infrared detection methods potentially exclude their use for experiments working with much smaller volumes. Additionally, precise CT analytics become difficult with high amounts of biomass (e.g., phytoplankton cultures or even impossible in the presence of planktonic calcifiers without sample pre-filtration. Filtration however, can alter CT concentration through gas exchange induced by high pressure. Addressing these problems, we present precise quantification of CT using a small, basic and inexpensive gas chromatograph as a CT analyzer. Our technique is able to provide a repeatability of ±3.1 μmol kg−1, given by the pooled standard deviation over a CT range typically applied in acidification experiments. 200 μL of sample is required to perform the actual CT measurement. The total sample amount needed is 12 mL. Moreover, we show that sample filtration is applicable with only minor alteration of the CT. The method is simple, reliable and with low cumulative material costs. Hence, it is potentially attractive for all researchers experimentally manipulating the seawater carbonate system.

  8. Evaluation of a portable gas chromatograph with photoionization detector under variations of VOC concentration, temperature, and relative humidity.

    Soo, Jhy-Charm; Lee, Eun Gyung; LeBouf, Ryan F; Kashon, Michael L; Chisholm, William; Harper, Martin

    2018-04-01

    The objective of this present study was to evaluate the performance of a portable gas chromatograph-photoionization detector (GC-PID), under various test conditions to determine if it could be used in occupational settings. A mixture of 7 volatile organic compounds (VOCs)-acetone, ethylbenzene, methyl isobutyl ketone, toluene, m-xylene, p-xylene, and o-xylene-was selected because its components are commonly present in paint manufacturing industries. A full-factorial combination of 4 concentration levels (exposure scenarios) of VOC mixtures, 3 different temperatures (25°C, 30°C, and 35°C), and 3 relative humidities (RHs; 25%, 50%, and 75%) was conducted in a full-size controlled environmental chamber. Three repetitions were conducted for each test condition allowing for estimation of accuracy. Time-weighted average exposure data were collected using solid sorbent tubes (Anasorb 747, SKC Inc.) as the reference sampling medium. Calibration curves of Frog-4000 using the dry gases showed R 2 > 0.99 for all analytes except for toluene (R 2 = 0.97). Frog-4000 estimates within a test condition showed good consistency for the performance of repeated measurement. However, there was ∼41-64% reduction in the analysis of polar acetone with 75% RH relative to collection at 25% RH. Although Frog-4000 results correlated well with solid sorbent tubes (r = 0.808-0.993, except for toluene) most of the combinations regardless of analyte did not meet the <25% accuracy criterion recommended by NIOSH. The effect of chromatographic co-elution can be seen with m, p-xylene when the results are compared to the sorbent tube sampling technique with GC-flame ionization detector. The results indicated an effect of humidity on the quantification of the polar compounds that might be attributed to the pre-concentrator placed in the selected GC-PID. Further investigation may resolve the humidity effect on sorbent trap with micro GC pre-concentrator when water vapor is present. Although this

  9. Pyrolysis gas chromatographic study of homo polymers and copolymers of chlorotrifluoroethylene and styrene

    Rizvi, M.; Munir, A.

    1993-01-01

    Polymer degradation reactions have always been important for the development of thermally stable polymers. Among different available techniques, pyrolysis gas chromatography (PGC) has been used frequently to establish thermal stability and the plausible mechanism of degradation reactions. In the present work, homo polymers of chlorotrifluoroethylene (CTFE) and styrene and their copolymers were studied by PGC/IR for separation and identification of degraded products and to understand the degradation mechanism. Besides monomers, C/sub 2/H/sub 4/, C/sub 2/H/sub 2/, SiF/sub 4/, C/sub 6/H/sub 6/ C/sub 3/F/sub 5/Cl, C/sub 7/H sub 8/, C/sub 8/H/sub 10/ are the observed pyrolysis products. Mechanism for different degradation reactions have also been studied. (author)

  10. Headspace Solid Phase Micro Extraction Gas Chromatographic Determination of Fenthion in Human Serum

    Kyriaki Machera

    2008-05-01

    Full Text Available A simple and effective analytical procedure was developed for the determination of fenthion residues in human serum samples. The sample treatment was performed using the headspace solid-phase micro extraction with polyacrylate fiber, which has the advantage to require low amount of serum (1 mL without tedious pre-treatment. The quantification of fenthion was carried out by gas chromatography-mass spectrometry and the recoveries ranged from 79 to 104% at two spiking levels for 6 replicates. Detection and quantification limits were calculated as 1.51 and 4.54 ng/mL of serum respectively. Two fenthion metabolites − fenoxon and fenthion–sulfoxide − were also identified.

  11. Liquid chromatographic analysis of a formulated ester from a gas-turbine engine test

    Jones, W. R., Jr.; Morales, W.

    1983-01-01

    Size exclusion chromatography (SEC) utilizing mu-Bondagel and mu-Styragel columns with a tetrahydrofuran mobile phase was used to determine the chemical degradation of lubricant samples from a gas-turbine engine test. A MIL-L-27502 candidate, ester-based lubricant was run in a J57-29 engine at a bulk oil temperature of 216 C. In general, the analyses indicated a progressive loss of primary ester, additive depletion, and formation of higher molecular weight material. An oil sample taken at the conclusion of the test showed a reversal of this trend because of large additions of new oil. The high-molecular-weight product from the degraded ester absorbed strongly in the ultraviolet region at 254 nanometers. This would indicate the presence of chromophoric groups. An analysis of a similar ester lubricant from a separate high-temperature bearing test yielded qualitatively similar results.

  12. Gas chromatographic study of degradation phenomena concerning building and cultural heritage materials

    Metaxa, E.; Agelakopoulou, T.; Bassiotis, I.; Karagianni, Ch.; Roubani-Kalantzopoulou, F.

    2009-01-01

    Air pollution influences all aspects of social and economical life nowadays. In order to investigate the impact of air pollution on materials of works of art, the method of Reversed Flow-Inverse Gas Chromatography has been selected. The presence of various atmospheric pollutants is studied on marbles, oxides-building materials and samples of authentic statues from the Greek Archaeological Museums of Kavala and of Philippi. The method leads to the determination of several physicochemical quantities and the characterization of the heterogeneous surfaces of these solids. Moreover, the influence of a second pollutant (synergistic effect) is examined. The structure, the properties and the behavior of the materials are examined by X-Ray Diffraction, Scanning Electron Microscopy and Raman Spectroscopy. Therefore, the precise measurement of the above mentioned quantities form the scientific basis for elucidation of the mechanism of the whole phenomenon of the degradation, thus providing a scientific platform to conservation procedures.

  13. Determination of Profenofos Pesticidal Residue in Lettuce (Lactuca sativa L. by Gas Chromatographic Method

    Yohannes Alen

    2015-05-01

    Full Text Available The determination of profenofos pesticidal residue in the lettuce (Lactuca sativa L. by using gas chromatography using flame photometric detector (FPD had been investigated. The lettuce was collected from Padang Luar area, Agam distric, West Sumatera. Sample for determination of profenofos residue divided into three groups: unwashed (A, washed with water (B, and washed with detergent (C. Maceration with sonication was used for the extraction using ethylacetateas a solvent. The results showed that profenofos pesticide residue in sample A, B and C were 0.204, 0.080 and 0.061 ppm, respectively. These profenofos pesticidal residue are over than the Maximum Residue Limits (MRL that established by The Japan Food Chemical Research Foundation (0.05 ppm even though World Health Organization (WHO has not established Maximum Residue Limits (MRL profenofos on lettuce. Based on the statistical analysis one-way method (Anova using SPSS 20.0 showed that there was a significant concentrations difference between lettuce A from lettuce B and lettuce C with p < 0.05.

  14. Gas chromatographic determination of purines and pyrimidines from DNA using ethyl chloroformate as derivatizing reagent

    Brohi, R.O.Z.; Khuhawar, M.Y.; Laghari, A.J.; Channa, A.

    2016-01-01

    An analytical method has been proposed for the separation and determination of guanine, adenine, cytosine, thymine and uracil by gas chromatography (GC) following precolumn derivatization using ethyl chloroformate. The GC separation was achieved from HP-5 (30 m x 0.32 rnrn id) column with layer thickness 0.25 microm. The linear calibrations were observed within 0.5-50.0 micro mole/L for each of the compound and limits of detection were within 0.1-0.17 micro mol/L. The derivatization, separation and quantitation was repeatable with intra (n=5) and inter (n=5) variation in terms of peak height/peak area and retention time with relative standard deviation (RSD) within 4.70-6.43%. The method was applied for the analysis of isolated DNA from human blood and plant leaves after acid hydrolysis. The concentration of thymine, adenine, cytosine and guanine in blood samples were observed within 0.602-2.135 micro mol/L of each compounds with RSD 2.60- 6.00%. The recovery of the nucleobases by standard addition was calculated within 98-108% with RSD 2.5-7.8%. (author)

  15. Gas Chromatographic Determination of Purines and Pyrimidines from DNA Using Ethyl Chloroformate as Derivatizing Reagent

    Rafi O. Zaman Brohi

    2016-06-01

    Full Text Available An analytical method has been proposed for the separation and determination of guanine, adenine, cytosine, thymine and uracil by gas chromatography (GC following precolumn derivatization using ethyl chloroformate. The GC separation was achieved from HP-5 (30 m × 0.32 mm id column with layer thickness 0.25 µm. The linear calibrations were observed within 0.5-50.0 µmol/L for each of the compound and limits of detection were within 0.1-0.17 µmol/L. The derivatization, separation and quantitation was repeatable with intra (n=5 and inter (n=5 variation in terms of peak height/peak area and retention time with relative standard deviation (RSD within 4.70-6.43%. The method was applied for the analysis of isolated DNA from human blood and plant leaves after acid hydrolysis. The concentration of thymine, adenine, cytosine and guanine in blood samples were observed within 0.602-2.135 µmol/L of each compounds with RSD 2.60-6.00%. The recovery of the nucleobases by standard addition was calculated within 98-108% with RSD 2.5-7.8%.

  16. π-Extended triptycene-based material for capillary gas chromatographic separations.

    Yang, Yinhui; Wang, Qinsi; Qi, Meiling; Huang, Xuebin

    2017-10-02

    Triptycene-based materials feature favorable physicochemical properties and unique molecular recognition ability that offer good potential as stationary phases for capillary gas chromatography (GC). Herein, we report the investigation of utilizing a π-extended triptycene material (denoted as TQPP) for GC separations. As a result, the TQPP capillary column exhibited high column efficiency of 4030 plates m -1 and high-resolution performance for a wide range of analytes, especially structural and positional isomers. Interestingly, the TQPP stationary phase showed unique shape selectivity for alkanes isomers and preferential retention for analytes with halogen atoms and H-bonding nature mainly through their halogen-bonding and H-bonding interactions. In addition, the TQPP column had good repeatability and reproducibility with the RSD values of 0.02-0.34% for run-to-run, 0.09-0.80% for day-to-day and 1.4-5.2% for column-to-column, respectively, and favorable thermal stability up to 280 °C. This work demonstrates the promising future of triptycene-based materials as a new class of stationary phases for GC separations. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Gas chromatographic/mass spectrometric characterization of dromostanolone metabolites in human urine

    Kim, Tae Wook; Choi, Man Ho; Jung, Byung Hwa; Chung, Bong Chul

    1998-01-01

    The metabolism of dromostanolone (2α-methyl-5α-androstan-17β-ol-3-one) was studied in three adult volunteers after oral dose of 20 mg. Solvent extracts of urine obtained after enzyme hydrolysis were derivatized with MSTFA/TMCS and MSTFA/TMIS. The structures of intact drug and its metabolites were determined by gas chromatography/mass spectrometry (GC/MS) in electron impact (EI) mode. The major metabolite (2α-methyl-5α-androstan-3α-ol-17-one), its 3β-epimer, parent compound, and several hydroxylated metabolites including intact drug were detected by comparing total ion chromatograms of control urine with that of the administered sample. Two epimers of 2α-methyl-5α-androstan-3, 17β-diol were detected using selected ion monitoring. The maximum excretion of dromostanolone and 2α-methyl-5α-androstan-3α-ol-17-one was reached in 6.2-15 hr. The half-life of intact dromostanolone was 5.3 hr. About 3.0% of the administered amount was found to be excreted within 95 hr as unchanged form

  18. Characterization of Atypical Off-Flavor Compounds in Natural Cork Stoppers by Multidimensional Gas Chromatographic Techniques.

    Slabizki, Petra; Fischer, Claus; Legrum, Charlotte; Schmarr, Hans-Georg

    2015-09-09

    Natural cork stoppers with sensory deviations other than the typical cork taint were subgrouped according to their sensory descriptions and compared with unaffected control cork stoppers. The assessment of purge and trap extracts obtained from corresponding cork soaks was performed by heart-cut multidimensional gas chromatography-olfactometry (MDGC-O). The identification of compounds responsible for atypical cork taint detected in MDGC-O was further supported with additional multidimensional GC analysis in combination with mass spectrometric detection. Geosmin and 2-methylisoborneol were mainly found in cork stoppers described as moldy and cellarlike; 3-isopropyl-2-methoxypyrazine and 3-isobutyl-2-methoxypyrazine were found in cork stoppers described with green attributes. Across all cork subgroups, the impact compound for typical cork taint, 2,4,6-trichloroanisole (TCA), was present and is therefore a good marker for cork taint in general. Another potent aroma compound, 3,5-dimethyl-2-methoxypyrazine (MDMP), was also detected in each subgroup, obviously playing an important role with regard to the atypical cork taint. Sensory deviations possibly affecting the wine could be generated by MDMP and its presence should thus be monitored in routine quality control.

  19. Disposable pipette extraction for gas chromatographic determination of codeine, morphine, and 6-monoacetylmorphine in vitreous humor.

    Kovatsi, Leda; Rentifis, Konstantinos; Giannakis, Dimitrios; Njau, Samuel; Samanidou, Victoria

    2011-07-01

    The availability of a sensitive and rapid analytical method for the determination of opiates, and other substances of forensic interest, in a variety of biological specimens is of utmost importance to forensic laboratories. Solid-phase extraction is very popular in the pre-treatment of forensic samples. Nevertheless, a new approach, disposable pipette extraction (DPX), is gaining increasing interest in sample preparation. DPX has already been applied to the analysis of drugs of abuse in common biological matrices, such as urine and blood, but has not yet been evaluated on alternative biological samples, such as vitreous humor. The objective of this study was to evaluate the applicability of DPX on the analysis of opiates in vitreous humor. The currently developed method is fast, reliable, and easy to perform. The sensitivity, precision, and accuracy are satisfactory. Recoveries obtained are within the range of 72-91%, whereas the sample volume of vitreous humor required is only 100 μL. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Gas chromatographic quantitative analysis of the gaseous emissions and carbon balance in the alcoholic fermentation

    C. Chon

    1997-06-01

    ln order to try to answer to this question, methods able to analyse simultaneously and quantitatively the liquid phase, the gaseous emissions and the biomass are needed. Recently, we have shown that under suitable defined conditions 13C NMR spectroscopy allows the quantitative measurement of at least eight components present at a concentration up to 5 x 10-3M (glycerol, glucose, butandiols, tartric, malic, lactic, citric and succinic acids in a short time (one hour with a precision of about 3 p. cent. The measurements of the ethanol concentrations and of the amount of carbon transferred in the biomass are easily achieved using respectively ebullioscopic and standard combustion techniques. We are now able to extend these results and to show that, by using gas chromatography in a continuous dynamic mode and under a sweep of air at the head space of the fermentor, it is possible to measure quantitatively the mixture of volatile substances (composed mainly of air, carbon dioxide, ethanol and water emanating from an alcoholic fermentation. The results obtained, when correlated with quantitative 13C NMR spectroscopy on the medium components permits the total balance sheet of the carbon transfers occuring during the fermentation process betwcen the liquid and the gaseous phases to be established. Our results indicate that the losses of ethanol during the fermentation process conducted under an air flow at the head space of the fermentor, may reach about 10 p. cent of the theoretical maximal amount of ethanol produced. The experiments presented here could explain the ethanol losses observed during some vinification processes conducted in open tanks.

  1. Antioxidant and Antiangiogenic Properties, and Gas Chromatographic-Time of Flight Analysis of Sonchus arvensis Leaves Extracts

    Itam, A.; Shah, A. M.; Majid, A.; Ismail, Z.

    2015-01-01

    Sonchus arvensis L. (Asteraceae) is one of the medicinal herbs used in traditional medicines, in which the leaf extract was used as a diuretic, lithotriptic and antiurolithiasis agent. The leaves of S. arvensis reported contain several compounds, including a variety of flavonoids, terpenoids and sterol, even this plant also contain silica and potassium. Flavonoids are secondary metabolite compound which have ability as antioxidant. In this study, the aims are to determine of antioxidants and antiangiogenic properties, and phytoconstituents quantitative of aqueous and methanol extracts of S. arvensis leaves. The antioxidant properties were studied using 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radical, xanthine oxidase and beta-carotene-linoleate models system. Furthermore, the antiangiogenic property was evaluated using ex vivo rat aorta ring assay. Quantitative determination of extracts phytoconstituents were carried out by using Gas Chromatographic-Time of Flight (GC-TOF) mass spectrophotometric methods. The results showed that the aqueous and methanol extracts have ability as antioxidant which is antioxidant activities of aqueous extracts on DPPH radical and inhibition of xanthine oxidase activity are higher than that of methanol extracts. Meanwhile antioxidant activity using beta-carotene-linoleate model system of S. arvensis aqueous extract is lower than that of methanol extracts. Nevertheless, the differences of these antioxidant activities are not significant. Antiangiogenic property of aqueous extract is also higher than that of methanol extract which is measured at 100 meu g mL/sup -1/ of extracts. This indicates that there is correlation between antioxidant activity and antiangigenic property, exhibiting that this plant possesses the potential to prevent or cure the diseases that related to angiogenesis such as cancer. (author)

  2. Gas chromatographic-mass spectrometric analysis of di(2-ethylhexyl) phthalate and its metabolites in hepatic microsomal incubations

    Pietrogrande, M.C.; Rossi, D.; Paganetto, G

    2003-03-17

    A method is reported for the determination of di(2-ethylhexyl) phthalate (DEHP) and its metabolites in in vitro metabolism studies. Gas chromatography-mass spectrometry (GC-MS) analysis allows separation of 18 by-products of DEHP metabolism. On the basis of retention time and specific mass spectra m/z values, three classes of compounds can be identified: (i) alcohols as hydrolysis product; (ii) acids produced by alcohol oxidation; (iii) compounds retaining phthalic moiety. The chromatogram can also be acquired in SIM mode at m/z 149 resulting in 13 well-separated chromatographic peaks: from retention time and mass spectra it can be inferred that the main peaks correspond to mono(2-ethylhexyl) phthalate (MEHP) and ({omega}-1)-hydroxyl-MEHP. The kinetics of DEHP metabolism was studied using an S9 Aroclor-induced liver fraction as in vitro model and following incubation assay after 20, 40, 60 and 90 min. The composition of incubation mixtures can be quantitatively evaluated from selected ion monitoring chromatograms at m/z 149: the by-product concentration increases during the incubation time, as a consequence of DEHP degradation. During the incubation test a significant conversion of DEHP into MEHP is observed: a conversion yield of 10, 13, 16 and 20% of the original DEHP is obtained after 20, 40, 60 and 90 min, respectively. The metabolic conversion of DEHP to MEHP explains the endocrine-disrupting activity of the original DEHP; moreover, it has been demonstrated that MEHP and its ({omega}-1)-oxidation metabolite induce peroxisome proliferation. This result strengthens the suggestion that the study of DEHP metabolic pathway is fundamental to better understanding its toxicological behavior.

  3. Total OH reactivity measurements using a new fast Gas Chromatographic Photo-Ionization Detector (GC-PID

    V. Sinha

    2012-12-01

    Full Text Available The primary and most important oxidant in the atmosphere is the hydroxyl radical (OH. Currently OH sinks, particularly gas phase reactions, are poorly constrained. One way to characterize the overall sink of OH is to measure directly the ambient loss rate of OH, the total OH reactivity. To date, direct measurements of total OH reactivity have been either performed using a Laser-Induced Fluorescence (LIF system ("pump-and-probe" or "flow reactor" or the Comparative Reactivity Method (CRM with a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS. Both techniques require large, complex and expensive detection systems. This study presents a feasibility assessment for CRM total OH reactivity measurements using a new detector, a Gas Chromatographic Photoionization Detector (GC-PID. Such a system is smaller, more portable, less power consuming and less expensive than other total OH reactivity measurement techniques.

    Total OH reactivity is measured by the CRM using a competitive reaction between a reagent (here pyrrole with OH alone and in the presence of atmospheric reactive molecules. The new CRM method for total OH reactivity has been tested with parallel measurements of the GC-PID and the previously validated PTR-MS as detector for the reagent pyrrole during laboratory experiments, plant chamber and boreal field studies. Excellent agreement of both detectors was found when the GC-PID was operated under optimum conditions. Time resolution (60–70 s, sensitivity (LOD 3–6 s−1 and overall uncertainty (25% in optimum conditions for total OH reactivity were similar to PTR-MS based total OH reactivity measurements. One drawback of the GC-PID system was the steady loss of sensitivity and accuracy during intensive measurements lasting several weeks, and a possible toluene interference. Generally, the GC-PID system has been shown to produce closely comparable results to the PTR-MS and thus in suitable environments (e.g. forests it

  4. Immunological screening of drugs of abuse and gas chromatographic-mass spectrometric confirmation of opiates and cocaine in hair.

    Segura, J; Stramesi, C; Redón, A; Ventura, M; Sanchez, C J; González, G; San, L; Montagna, M

    1999-03-05

    The work presents an analytical strategy to detect drugs of abuse in hair. It involves two sequential steps: a screening by a simple enzyme-linked immunosorbent assay (ELISA) methodology to detect opiates, cocaine and its metabolites, and benzodiacepines, followed by confirmation of opiates and cocaine metabolites in positive samples by gas chromatography coupled to mass spectrometry (GC-MS). In the same GC-MS run other drugs for substitution therapy (e.g. methadone and its main metabolite) can also be detected. After a double washing of hair samples with dichloromethane, hair specimens were cut into small pieces and 10 mg samples were incubated in 2 ml of methanol-trifluoroacetic acid (9:1) mixture, overnight at 37 degrees C. Aliquots of the extract were then evaporated, reconstituted in buffer and analysed according to the ELISA procedure. Confirmation involved solid-phase extraction of another fraction of the extract kept at -20 degrees C, derivatization with heptafluorobutyric anhydride and hexafluoroisopropanol and detection of cocaine, benzoylecgonine, ecgonine methylester, cocaethylene, morphine, codeine, 6-monoacetylmorphine, methadone and 2-ethylidene-1.5-dimethyl-3,3-diphenylpirrolidine (methadone metabolite) by selective ion monitoring after gas chromatographic separation. During the development of the method it was verified that no more than 10% of cocaine, opiates and benzodiacepines were lost when dichloromethane was used to wash real samples. The results also confirmed the increase of extractability power of TFA when it was added to methanol: the recovery for the analytes (cocaine and its metabolites and opiates) added to methanol-TFA alone was of the order of 90% except for benzoylecgonine (75%), and the recovery for the analytes added to methanol-TFA extract of drug-free hair was about 90% for all analytes except for benzoylecgonine and 6-MAM (around 70%). Regarding the stability of labile compounds, only small amounts of ecgonine methylester (2

  5. Rapid determination of environmental plutonium in large water samples by means of manganese dioxide Co-precipitation and extraction chromatographic separation

    Sidhu, R.S.; Hoff, P.

    1999-01-01

    Plutonium activity determinations in environmental water samples are routinely performed in many laboratories. Due to the low plutonium concentrations and the complexity of the plutonium aqueous chemistry, these analysis involve cumbersome preconcentration and separation procedures and long measurement times. We describe a procedure where MnO 2 (s) is used as scavenger to preconcentrate Pu prior to separation by the transuranium specific extraction chromatographic resin TRU-Resin. The ability of MnO 4 - /MnO 2 (s) to destroy organic matter and oxidise plutonium is combined with the specific behaviour of the TRU-resin for transuranium elements. The method facilitates a rapid preconcentration and separation of plutonium. With the use of this procedure, the laboratory work on one sample can be performed in one day with minimum attention. The overall yields from a 200 litre fresh- or seawater sample to a measurable Pu source are between 70-85%. (orig.)

  6. Method for the routine quantitative gas chromatographic analysis of major free fatty acids in butter and cream.

    Woo, A H; Lindsay, R C

    1980-07-01

    A rapid quantiative method was developed for routine analysis of the major, even carbon-numbered free fatty acids in butter and cream. Free fatty acids were isolated directly from intact samples by a modified silicic acid-potassium hydroxide arrestant column and were separated by gas chromatography with a 1.8 m x 2 mm inner diameter glass column packed with 10% neopentyl glycol adipate on 80/100 Chromosorb W. Purified, formic acid-saturated carrier gas was required for minimal peak tailing and extended column life. The accuracy and reproducibility of the mmethod was established through quantitative recovery studies of free fatty acid mixtures, free fatty acids added to butter, and replicate analysis of butter and cream samples.

  7. Determination of Diffusion Coefficients and Activation Energy of Selected Organic Liquids using Reversed-Flow Gas Chromatographic Technique

    Khalisanni Khalid; Rashid Atta Khan; Sharifuddin Mohd Zain

    2012-01-01

    Evaporation of vaporize organic liquid has ecological consequences when the compounds are introduced into both freshwater and marine environments through industrial effluents, or introduced directly into the air from industrial unit processes such as bioreactors and cooling towers. In such cases, a rapid and simple method are needed to measure physicochemical properties of the organic liquids. The Reversed-Flow Gas Chromatography (RF-GC) sampling technique is an easy, fast and accurate procedure. It was used to measure the diffusion coefficients of vapors from liquid into a carrier gas and at the same time to determine the rate coefficients for the evaporation of the respective liquid. The mathematical expression describing the elution curves of the samples peaks was derived and used to calculate the respective parameters for the selected liquid pollutants selected such as methanol, ethanol, 1-propanol, 1-butanol, n-pentane, n-hexane, n-heptane and n-hexadecane, evaporating into the carrier gas of nitrogen. The values of diffusion coefficients found were compared with those calculated theoretically or reported in the literature. The values of evaporation rate were used to determine the activation energy of respective samples using Arrhenius equation. An interesting finding of this work is by using an alternative mathematical analysis based on equilibrium at the liquid-gas interphase, the comparison leads to profound agreement between theoretical values of diffusion coefficients and experimental evidence. (author)

  8. Rapid chromatographic determination of caseins in milk with photometric and fluorimetric detection using a hydrophobic monolithic column.

    Ramírez-Palomino, P; Fernández-Romero, J M; Gómez-Hens, A

    2014-01-01

    Reverse-phase liquid chromatographic methods using a hydrophobic C18 monolithic column and on-line photometric and fluorimetric detection for the determination of the major casein (CN) proteins in milk are presented. The separation of αs1-CN, αs2-CN, β-CN and κ-CN was achieved in only five minutes. Fluorimetric detection enabled better analytical results than photometric detection. Thus, the dynamic ranges of the calibration graphs and detection limits obtained using fluorimetric detection were (mgmL(-)(1)): αs1-CN (0.74-10.0, 0.22), αs2-CN (0.15-10.0, 0.045), β-CN (0.68-10.0, 0.20) and κ-CN (0.21-10.0, 0.06). The analytical features of the photometric method, which does not allow the quantification of β-casein, were (mgmL(-)(1)): αs1-CN (1.5-9.0, 0.45), αs2-CN (1.4-10.0, 0.43) and κ-CN (0.4-9.0, 0.12). Precision data, expressed as relative standard deviation, ranged between 0.6% and 5.3% for the fluorimetric method and between 2.4% and 6.2% for the photometric method. Both methods were applied to the analysis of three different milk samples, obtaining recoveries in the ranges of 86.6-103.2% and 92.0-106.5% using fluorimetric and photometric detection, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Magnesium ferrite nanoparticles: a rapid gas sensor for alcohol

    Godbole, Rhushikesh; Rao, Pratibha; Bhagwat, Sunita

    2017-02-01

    Highly porous spinel MgFe2O4 nanoparticles with a high specific surface area have been successfully synthesized by a sintering free auto-combustion technique and characterized for their structural and surface morphological properties using XRD, BET, TEM and SEM techniques. Their sensing properties to alcohol vapors viz. ethanol and methanol were investigated. The site occupation of metal ions was investigated by VSM. The as-synthesized sample shows the formation of sponge-like porous material which is necessary for gas adsorption. The gas sensing characteristics were obtained by measuring the gas response as a function of operating temperature, concentration of the gas, and the response-recovery time. The response of magnesium ferrite to ethanol and methanol vapors was compared and it was revealed that magnesium ferrite is more sensitive and selective to ethanol vapor. The sensor operates at a substantially low vapor concentration of about 1 ppm of alcohol vapors, exhibits fantastic response reproducibility, long term reliability and a very fast response and recovery property. Thus the present study explored the possibility of making rapidly responding alcohol vapor sensor based on magnesium ferrite. The sensing mechanism has been discussed in co-relation with magnetic and morphological properties. The role of occupancy of Mg2+ ions in magnesium ferrite on its gas sensing properties has also been studied and is found to influence the response of magnesium ferrite ethanol sensor.

  10. An aircraft gas chromatograph-mass spectrometer System for Organic Fast Identification Analysis (SOFIA): design, performance and a case study of Asian monsoon pollution outflow

    Bourtsoukidis, Efstratios; Helleis, Frank; Tomsche, Laura; Fischer, Horst; Hofmann, Rolf; Lelieveld, Jos; Williams, Jonathan

    2017-12-01

    Volatile organic compounds (VOCs) are important for global air quality and oxidation processes in the troposphere. In addition to ground-based measurements, the chemical evolution of such species during transport can be studied by performing in situ airborne measurements. Generally, aircraft instrumentation needs to be sensitive, robust and sample at higher frequency than ground-based systems while their construction must comply with rigorous mechanical and electrical safety standards. Here, we present a new System for Organic Fast Identification Analysis (SOFIA), which is a custom-built fast gas chromatography-mass spectrometry (GC-MS) system with a time resolution of 2-3 min and the ability to quantify atmospheric mixing ratios of halocarbons (e.g. chloromethanes), hydrocarbons (e.g isoprene), oxygenated VOCs (acetone, propanal, butanone) and aromatics (e.g. benzene, toluene) from sub-ppt to ppb levels. The relatively high time resolution is the result of a novel cryogenic pre-concentration unit which rapidly cools (˜ 6 °C s-1) the sample enrichment traps to -140 °C, and a new chromatographic oven designed for rapid cooling rates (˜ 30 °C s-1) and subsequent thermal stabilization. SOFIA was installed in the High Altitude and Long Range Research Aircraft (HALO) for the Oxidation Mechanism Observations (OMO) campaign in August 2015, aimed at investigating the Asian monsoon pollution outflow in the tropical upper troposphere. In addition to a comprehensive instrument characterization we present an example monsoon plume crossing flight as a case study to demonstrate the instrument capability. Hydrocarbon, halocarbon and oxygenated VOC data from SOFIA are compared with mixing ratios of carbon monoxide (CO) and methane (CH4), used to define the pollution plume. By using excess (ExMR) and normalized excess mixing ratios (NEMRs) the pollution could be attributed to two air masses of distinctly different origin, identified by back-trajectory analysis. This work

  11. A multiresidue method by high performance liquid chromatography-based fractionation and gas chromatographic determination of trace levels of pesticides in air and water.

    Seiber, J N; Glotfelty, D E; Lucas, A D; McChesney, M M; Sagebiel, J C; Wehner, T A

    1990-01-01

    A multiresidue analytical method is described for pesticides, transformation products, and related toxicants based upon high performance liquid chromatographic (HPLC) fractionation of extracted residue on a Partisil silica gel normal phase column followed by selective-detector gas chromatographic (GC) determination of components in each fraction. The HPLC mobile phase gradient (hexane to methyl t-butyl ether) gave good chromatographic efficiency, resolution, reproducibility and recovery for 61 test compounds, and allowed for collection in four fractions spanning polarities from low polarity organochlorine compounds (fraction 1) to polar N-methylcarbamates and organophosphorus oxons (fraction 4). The multiresidue method was developed for use with air samples collected on XAD-4 and related trapping agents, and water samples extracted with methylene chloride. Detection limits estimated from spiking experiments were generally 0.3-1 ng/m3 for high-volume air samples, and 0.01-0.1 microgram/L for one-liter water samples. Applications were made to determination of pesticides in fogwater and air samples.

  12. A RAPID THIN-LAYER CHROMATOGRAPHIC PROCEDURE TO IDENTIFY POOR AND EXTENSIVE OXIDATIVE DRUG METABOLIZERS IN MAN USING DEXTROMETHORPHAN

    DEZEEUW, RA; EIKEMA, D; FRANKE, JP; JONKMAN, JHG

    A rapid TLC method is presented to distinguish poor oxidative drug metabolizers from extensive oxidative drug metabolizers. Dextromethorphan (1) is used as test probe because it is safe, well characterized, generally available and easy to measure. The method is based on the extraction of 1 and its

  13. Electrochemical reduction of phthalide at carbon cathodes in dimethylformamide: Effects of supporting electrolyte and gas chromatographic injector-port chemistry on the product distribution

    Pasciak, Erick M.; Hochstetler, Spencer E.; Mubarak, Mohammad S.; Evans, Dennis H.; Peters, Dennis G.

    2013-01-01

    Highlights: • Reduction of phthalide gives a radical-anion that undergoes ring-opening in 3.5 s. • Phthalide reduction gives 2-methylbenzoate esters with electrolyte-derived moieties. • Electrolysis of phthalide affords products that depend on the method of analysis. • Upon reduction, phthalide undergoes deuteration in the presence of deuterium oxide. -- Abstract: Cyclic voltammetry and controlled-potential (bulk) electrolysis have been used to investigate the direct reduction of phthalide at carbon electrodes in dimethylformamide (DMF) containing 0.10 M tetramethylammonium perchlorate (TMAP) or tetra-n-butylammonium perchlorate (TBAP). Cyclic voltammograms recorded with a glassy carbon electrode exhibit a single cathodic peak and a corresponding anodic peak that arise, respectively, from one-electron reduction of phthalide to generate a radical-anion intermediate and from reoxidation of the intermediate. At a scan rate of 100 mV s −1 , quasi-reversible behavior is observed (due to ring-opening of the radical-anion), whereas fully reversible behavior is seen at 5 V s −1 or higher. Digital simulation of cyclic voltammograms indicates that the lifetime of the radical-anion is 3.5 s. Bulk electrolysis of phthalide at a reticulated vitreous carbon cathode affords products that depend on the procedure used to analyze the catholyte. Direct injection of catholyte into a gas chromatograph shows phthalide and a 2-methylbenzoate ester bearing an alkyl moiety from the supporting-electrolyte cation. However, if the catholyte is partitioned between diethyl ether and aqueous hydrochloric acid before gas chromatographic analysis, phthalide and 2-methylbenzoic acid are observed. Thermally induced reactions that occur in the injector port of the gas chromatograph are responsible for the formation of the 2-methylbenzoate ester as well as for the phthalide found in all electrolyzed solutions

  14. SIMULTANEOUS ANALYSIS OF AZIDOTHYMIDINE AND ITS MONOPHOSPHATE, DIPHOSPHATE AND TRIPHOSPHATE DERIVATIVES IN BIOLOGICAL-FLUIDS, TISSUE AND CULTURED-CELLS BY A RAPID HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC METHOD

    MOLEMA, G; JANSEN, RW; Visser, Jan; MEIJER, DKF

    1992-01-01

    A rapid high-performance liquid chromatographic (HPLC) method for the simultaneous analysis of the antiviral drug azidothymidine (AZT), AZT monophosphate, AZT diphosphate and AZT triphosphate, with ultraviolet detection in the nanomolar range, is described. Determination of these compounds in vitro

  15. Miniaturized Planar Room Temperature Ionic Liquid Electrochemical Gas Sensor for Rapid Multiple Gas Pollutants Monitoring.

    Wan, Hao; Yin, Heyu; Lin, Lu; Zeng, Xiangqun; Mason, Andrew J

    2018-02-01

    The growing impact of airborne pollutants and explosive gases on human health and occupational safety has escalated the demand of sensors to monitor hazardous gases. This paper presents a new miniaturized planar electrochemical gas sensor for rapid measurement of multiple gaseous hazards. The gas sensor features a porous polytetrafluoroethylene substrate that enables fast gas diffusion and room temperature ionic liquid as the electrolyte. Metal sputtering was utilized for platinum electrodes fabrication to enhance adhesion between the electrodes and the substrate. Together with carefully selected electrochemical methods, the miniaturized gas sensor is capable of measuring multiple gases including oxygen, methane, ozone and sulfur dioxide that are important to human health and safety. Compared to its manually-assembled Clark-cell predecessor, this sensor provides better sensitivity, linearity and repeatability, as validated for oxygen monitoring. With solid performance, fast response and miniaturized size, this sensor is promising for deployment in wearable devices for real-time point-of-exposure gas pollutant monitoring.

  16. Development and validation of a rapid chromatographic method for the analysis of flunarizine and its main production impurities

    Niamh O’Connor

    2013-06-01

    Full Text Available A rapid selective method for the analysis of flunarizine and its associated impurities was developed and validated according to ICH guidelines. The separation was carried out using a Thermo Scientific Hypersil Gold C18 column (50mm×4.6mm i.d., 1.9μm particle size with a gradient mobile phase of acetonitrile–ammonium acetate–tetrabutylammoniumhydrogen sulfate buffer, at a flow rate of 1.8mL/min and UV detection at 230nm. Naturally aged samples were also tested to determine sample stability. A profile of sample and impurity breakdown was also presented. Keywords: Flunarizine, Sub 2μm column, Active pharmaceutical ingredient, HPLC

  17. A simple and rapid chromatographic method to determine unauthorized basic colorants (rhodamine B, auramine O, and pararosaniline) in processed foods.

    Tatebe, Chiye; Zhong, Xining; Ohtsuki, Takashi; Kubota, Hiroki; Sato, Kyoko; Akiyama, Hiroshi

    2014-09-01

    A simple and rapid high-performance liquid chromatography (HPLC) method to determine basic colorants such as pararosaniline (PA), auramine O (AO), and rhodamine B (RB) in various processed foods was developed. Linearity of the calibration curves ranged from 0.05 to 50 μg/mL for PA and 0.05-100 μg/mL for AO and RB. The detection and quantification limits (LOD and LOQ) of the basic colorants, which were evaluated as signal-to-noise ratios of 3 for LOD and 10 for LOQ, ranged from 0.0125 to 0.05 and 0.025 to 0.125 μg/g, respectively. The recoveries and relative standard deviations of three basic colorants in six processed foods, namely, chili sauce, curry paste, gochujang (hot pepper paste), tandoori chicken (roasted chicken prepared with yogurt and spices), powder soup, and shrimp powder ranged from 70.2% to 102.8% and 0.8% to 8.0%, respectively. The intraday precision of the recovery test ranged from 1.7% to 4.5%, whereas the interday precision ranged from 3.7% to 7.7%. The reported method has been successfully applied to basic colorant determination in various processed foods such as fat-based food matrices (curry paste and tandoori chicken), chili products (gochujang and chili sauce), and protein-based products (shrimp powder and powder soup). Thin layer chromatography and liquid chromatography/mass spectrometry methods for the determination of basic colorants in processed foods were also developed for rapid analysis and identification, respectively. These methods are very useful for monitoring unauthorized basic colorants in inspection centers or quarantine laboratories in many countries.

  18. Gas and particle motions in a rapidly decompressed flow

    Johnson, Blair; Zunino, Heather; Adrian, Ronald; Clarke, Amanda

    2017-11-01

    To understand the behavior of a rapidly decompressed particle bed in response to a shock, an experimental study is performed in a cylindrical (D = 4.1 cm) glass vertical shock tube of a densely packed (ρ = 61%) particle bed. The bed is comprised of spherical glass particles, ranging from D50 = 44-297 μm between experiments. High-speed pressure sensors are incorporated to capture shock speeds and strengths. High-speed video and particle image velocimetry (PIV) measurements are collected to examine vertical and radial velocities of both the particles and gas to elucidate features of the shock wave and resultant expansion wave in the lateral center of the tube, away from boundaries. In addition to optically analyzing the front velocity of the rising particle bed, interaction between the particle and gas phases are investigated as the flow accelerates and the particle front becomes more dilute. Particle and gas interactions are also considered in exploring mechanisms through which turbulence develops in the flow. This work is supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science and Academic Alliance Program, under Contract No. DE-NA0002378.

  19. Towards the interaction between calcium carbide and water during gas-chromatographic determination of trace moisture in ultra-high purity ammonia.

    Trubyanov, Maxim M; Mochalov, Georgy M; Suvorov, Sergey S; Puzanov, Egor S; Petukhov, Anton N; Vorotyntsev, Ilya V; Vorotyntsev, Vladimir M

    2018-05-16

    The current study focuses on the processes involved during the flow conversion of water into acetylene in a calcium carbide reaction cell for the trace moisture analysis of ammonia by reaction gas chromatography. The factors negatively affecting the reproducibility and the accuracy of the measurements are suggested and discussed. The intramolecular reaction of the HOCaCCH intermediate was found to be a side reaction producing background acetylene during the contact of wet ammonia gas with calcium carbide. The presence of the HOCaCCH intermediate among the reaction products is confirmed by an FTIR spectral study of calcium carbide powder exposed to wet gas. The side reaction kinetics is evaluated experimentally and its influence on the results of the gas chromatographic measurements is discussed in relation to the determination of the optimal operating parameters for ammonia analysis. The reaction gas chromatography method for the trace moisture measurements in an ammonia matrix was experimentally compared to an FTIR long-path length gas cell technique to evaluate the accuracy limitations and the resource intensity. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Rapid Analysis Procedures for Triglycerides and Fatty Acids as Pentyl and Phenethyl Esters for the Detection of Butter Adulteration Using Chromatographic Techniques

    Daniele Naviglio

    2017-01-01

    Full Text Available This paper presents the development of three methods for quality control, fraud detection, and authentication of butter fat and other oils/fats using chromatographic techniques, with one method for triglycerides and two methods for fatty acids (FAs. The procedure for the analysis of triglycerides requires only dissolution of the sample in n-hexane and gas chromatography (GC analysis using a capillary column. The second method is based on the transesterification of triglycerides as pentyl esters in a single-step reaction using sodium pentanoate in pentanol. The reaction proceeds at room temperature and is similar to the potassium hydroxide-catalysed transesterification of triglycerides with methanol and even more similar to the sodium methoxide method and sodium butanoate method. The advantage of using pentyl esters includes reducing the volatility of short-chain FAs, and substantial recoveries were obtained compared with methyl ester analysis. The third method involves the transesterification of triglycerides in fat through reaction with 2-phenylethanol in a single step; 2-phenylethanol possesses a chromophore, and the phenethyl esters formed are analysed by high-performance liquid chromatography (HPLC with UV detection.

  1. Solid-phase microextraction for gas chromatographic/mass spectrometric analysis of dimethoate in human biological samples.

    Gallardo, E; Barroso, M; Margalho, C; Cruz, A; Vieira, D N; López-Rivadulla, M

    2006-01-01

    A new, simple and rapid procedure for the determination of dimethoate in urine and blood samples was developed using direct immersion solid-phase microextraction and gas chromatography/mass spectrometry. This technique required only 0.1 mL of sample, and ethion was used as internal standard. Two types of coated fibre were compared (100 microm polydimethylsiloxane, and 65 microm Carbowax/divinylbenzene). Other parameters, such as extraction temperature, adsorption and desorption time, salt addition, agitation and pH, were optimized to enhance the sensitivity of the method. Limits of detection (LODs) and quantitation (LOQs) were 50 and 100 ng/mL for urine and 200 and 500 ng/mL for blood, respectively. The method was found to be linear between the LOQ and 40 microg/mL for urine, and between the LOQ and 50 microg/mL for blood, with correlation coefficients ranging from 0.9923-0.9996. Precision (intra- and interday) and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The mean absolute recoveries of dimethoate were 1.24 and 0.50% for urine and blood, respectively. Because of its simplicity and the fact that small volumes of sample are used, the described method can be successfully used in the diagnosis of poisoning by this pesticide, namely in those situations where the sample volume is limited, as frequently occurs in forensic toxicology. Copyright 2006 John Wiley & Sons, Ltd.

  2. Rapid chromatographic separation of dissoluble Ag(I) and silver-containing nanoparticles of 1-100 nanometer in antibacterial products and environmental waters.

    Zhou, Xiao-Xia; Liu, Rui; Liu, Jing-Fu

    2014-12-16

    Sensitive and rapid methods for speciation analysis of nanoparticulate Ag (NAg) and Ag(I) in complex matrices are urgently needed for understanding the environmental effects and biological toxicity of silver nanoparticles (AgNPs). Herein we report the development of a universal liquid chromatography (LC) method for rapid and high resolution separation of dissoluble Ag(I) from nanoparticles covering the entire range of 1-100 nm in 5 min. By using a 500 Å poresize amino column, and an aqueous mobile phase containing 0.1% (v/v) FL-70 (a surfactant) and 2 mM Na2S2O3 at a flow rate of 0.7 mL/min, all the nanoparticles of various species such as Ag and Ag2S were eluted in one fraction, while dissoluble Ag(I) was eluted as a baseline separated peak. The dissoluble Ag(I) was quantified by the online coupled ICP-MS with a detection limit of 0.019 μg/L. The NAg was quantified by subtracting the dissoluble Ag(I) from the total Ag content, which was determined by ICP-MS after digestion of the sample without LC separation. While the addition of FL-70 and Na2S2O3 into the mobile phase is essential to elute NAg and Ag(I) from the column, the use of 500 Å poresize column is the key to baseline separation of Ag(I) from ∼ 1 nm AgNPs. The feasibility of the proposed method was demonstrated in speciation analysis of dissoluble Ag(I) and NAg in antibacterial products and environmental waters, with very good chromatographic repeatability (relative standard deviations) in both peak area (<2%) and retention time (<0.6%), excellent spiked recoveries in the range of 84.7-102.7% for Ag(I) and 81.3-106.3% for NAg. Our work offers a novel approach to rapid and baseline separation of dissoluble metal ions from their nanoparticulate counterparts covering the whole range of 1-100 nm.

  3. Gas chromatographic-mass spectrometric determination of hydrophilic compounds in environmental water by solid-phase extraction with activated carbon fiber felt.

    Kawata, K; Ibaraki, T; Tanabe, A; Yagoh, H; Shinoda, A; Suzuki, H; Yasuhara, A

    2001-03-09

    Simple gas chromatographic-mass spectrometric determination of hydrophilic organic compounds in environmental water was developed. A cartridge containing activated carbon fiber felt was made by way of trial and was evaluated for solid-phase extraction of the compounds in water. The hydrophilic compounds investigated were acrylamide, N,N-dimethylacetamide, N,N-dimethylformamide, 1,4-dioxane, furfural, furfuryl alcohol, N-nitrosodiethylamine and N-nitrosodimethylamine. Overall recoveries were good (80-100%) from groundwater and river water. The relative standard deviations ranged from 4.5 to 16% for the target compounds. The minimum detectable concentrations were 0.02 to 0.03 microg/l. This method was successfully applied to several river water samples.

  4. Stereometabolism of ethylbenzene in man: gas chromatographic determination of urinary excreted mandelic acid enantiomers and phenylglyoxylic acid and their relation to the height of occupational exposure.

    Korn, M; Gfrörer, W; Herz, R; Wodarz, I; Wodarz, R

    1992-01-01

    Ethylbenzene is an important industrial solvent and a key substance in styrene production. Ethylbenzene metabolism leads to the formation of mandelic acid, which occurs in two enantiomeric forms, and phenylglyoxylic acid. To decide which enantiomer is preferably formed, 70 urine samples of exposed workers were taken at the end of shifts and--after 3-pentyl ester derivatisation--gas chromatographically analysed. The R/S ratio of mandelic acid enantiomers in urine amounts to 19:1, which means that R-mandelic acid is a major metabolite and S-mandelic acid is one of the minor urinary metabolites of ethylbenzene in man. The R/S ratio is independent of ambient air concentration of ethylbenzene within the investigated range. Compared to an ethylbenzene monoexposure the height of total mandelic acid excretion is decreased in the case of coexposure to other aromatic solvents.

  5. In situ alcoholysis of triacylglycerols by application of switchable-polarity solvents. A new derivatization procedure for the gas-chromatographic analysis of vegetable oils.

    Saliu, Francesco; Orlandi, Marco

    2013-10-01

    We describe a new use of switchable-polarity solvents for the simultaneous derivatization and extraction of triacylglycerols from vegetable oils before gas-chromatographic analysis. Different equimolecular mixtures of the commercially available amidine 1,8-diazabicyclo[5.4.0]undec-7-ene and n-alkyl alcohols were tested. Triolein was used as a model compound. Very good results were achieved by using butanol (recovery of butyl oleate was 89 ± 4%). The procedure was applied for the characterization of the fatty acid profile of different vegetable oils. No statistically significant differences from the results obtained with the application of two traditional methods were evidenced. Moreover, the use of switchable-polarity solvents showed many advantages: owing to the basicity of the amidines, no catalyst was required; the transterification reaction was conducted under mild conditions, one step and in situ; no particular matrix interferences were evidenced; the solvent was recovered.

  6. Chromatographic methods

    Marhol, M.; Stary, J.

    1975-01-01

    The characteristics are given of chromatographic separation and the methods are listed. Methods and data on materials used in partition, adsorption, precipitation and ion exchange chromatography are listed and conditions are described under which ion partition takes place. Special attention is devoted to ion exchange chromatography where tables are given to show the course of values of the partition coefficients of different ions in dependence on the concentration of agents and the course of equilibrium sorptions on different materials in dependence on the solution pH. A theoretical analysis is given and the properties of the most widely used ion exchangers are listed. Experimental conditions and apparatus used for each type of chromatography are listed. (L.K.)

  7. Finland: Scandinavia's top gas user sees demand rising rapidly

    Nielsen, H.H.

    1992-01-01

    The rising demand for natural gas in Finland which already uses more gas than any other Nordic country is noted. The natural gas market which is based on sales to large industries and for heating is compared to the market in Denmark which is geared to small private heating customers. Imports of Norwegian gas allowing increased sales for power generation in Finland, and the influence of the impending Finnish application for membership of the EC on the gas market are considered. (UK)

  8. Gas chromatography-mass spectrometry and high-performance liquid chromatographic analyses of thermal degradation products of common plastics

    Pacakova, V.; Leclercq, P.A.

    1991-01-01

    The thermo-oxidation of five commonly used materials, namely low-density polyethylene, retarded polyethylene, paper with a polyethylene foil, a milk package and filled polypropylene, was studied. Capillary gas chromatography and gas chromatography-mass spectrometry were used to analyze the volatile

  9. Contingency planning for rapid reduction of greenhouse gas emissions

    Larsson, Nils K.

    2010-03-01

    Full Text Available The current and predicted levels of greenhouse gas (GHG emissions are, according to the best international scientific estimates, leading the world towards climate change that will have serious consequences for all countries. The problem is aggravated by the tendency of people and institutions not to take action until catastrophic consequences emerge. The history of crises in other sectors show us that reactions are likely to focus on ad-hoc reactions or using plans that are readily available, with negative results. However, the alternative of developing public plans for drastic and rapid reductions is not likely to gain support because of their radical nature. The author therefore proposes that large organizations with direct or indirect control over substantial GHG emissions should prepare private contingency plans for very rapid reductions in emissions, so that more rational and less destructive plans will be available when the appropriate moment comes for last-minute action. Examples of the type of specific plans that may be appropriate are suggested.

    Según las estimaciones científicas internacionales más optimistas, los niveles actuales y previstos de emisiones de gases de efecto invernadero (GEI están llevando al mundo hacia un cambio climático que tendrá graves consecuencias para todos los países. El problema se ve agravado por la tendencia de personas e instituciones a no tomar medidas hasta que no se perciben las catastróficas consecuencias. El historial de crisis ocurridas en otros sectores nos demuestra que las reacciones probablemente se centren en medidas ad hoc o en emplear planes que ya existían, pero sin resultados. Sin embargo, es poco probable que la alternativa al desarrollo de planes públicos para las reducciones drásticas y rápidas consiga el apoyo necesario, debido precisamente a su radicalidad. El autor recomienda por tanto que las grandes organizaciones que tengan control directo o indirecto sobre un

  10. Gas chromatography-mass spectrometry and high-performance liquid chromatographic analyses of thermal degradation products of common plastics

    Pacakova, V.; Leclercq, P.A.

    1991-01-01

    The thermo-oxidation of five commonly used materials, namely low-density polyethylene, retarded polyethylene, paper with a polyethylene foil, a milk package and filled polypropylene, was studied. Capillary gas chromatography and gas chromatography-mass spectrometry were used to analyze the volatile degradation products, while high-performance liquid chromatography was employed to measure polycyclic aromatic hydrocarbons. The results are discussed from the point of view of toxicity of the prod...

  11. Multiplex real-time quantitative PCR, microscopy and rapid diagnostic immuno-chromatographic tests for the detection of Plasmodium spp: performance, limit of detection analysis and quality assurance

    Ralevski Filip

    2009-12-01

    Full Text Available Abstract Background Accurate laboratory diagnosis of malaria species in returning travelers is paramount in the treatment of this potentially fatal infectious disease. Materials and methods A total of 466 blood specimens from returning travelers to Africa, Asia, and South/Central America with suspected malaria infection were collected between 2007 and 2009 at the reference public health laboratory. These specimens were assessed by reference microscopy, multipex real-time quantitative polymerase chain reaction (QPCR, and two rapid diagnostic immuno-chromatographic tests (ICT in a blinded manner. Key clinical laboratory parameters such as limit of detection (LOD analysis on clinical specimens by parasite stage, inter-reader variability of ICTs, staffing implications, quality assurance and cost analysis were evaluated. Results QPCR is the most analytically sensitive method (sensitivity 99.41%, followed by CARESTART (sensitivity 88.24%, and BINAXNOW (sensitivity 86.47% for the diagnosis of malaria in returning travelers when compared to reference microscopy. However, microscopy was unable to specifically identify Plasmodia spp. in 18 out of 170 positive samples by QPCR. Moreover, the 17 samples that were negative by microscopy and positive by QPCR were also positive by ICTs. Quality assurance was achieved for QPCR by exchanging a blinded proficiency panel with another reference laboratory. The Kappa value of inter-reader variability among three readers for BINAXNOW and CARESTART was calculated to be 0.872 and 0.898 respectively. Serial dilution studies demonstrated that the QPCR cycle threshold correlates linearly with parasitemia (R2 = 0.9746 in a clinically relevant dynamic range and retains a LOD of 11 rDNA copies/μl for P. falciparum, which was several log lower than reference microscopy and ICTs. LOD for QPCR is affected not only by parasitemia but the parasite stage distribution of each clinical specimen. QPCR was approximately 6-fold more

  12. [The elaboration of gas chromatographic method of the determination of N-nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine) in biological samples (urine)].

    Zaytseva, N V; Ulanova, T S; Nurislamova, T V; Popova, N A

    2014-01-01

    The issues of the elaboration of a method for the determination of N-nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine) in urine by means of the method of capillary gas chromatography with the use of a thermionic detector are considered. There were performed investigations on the study of the efficacy of the extraction of N-nitrosamines from the urine by steam distillation and gas chromatographic detection of headspace. With the aim of the maximal recovery of N-nitrosamines from the urine and setting parameters of the extraction two method were used to prepare the bioassay for the analysis the alkalization with potassium hydroxide and the addition of salting out reagent--neutral salts of alkali and alkaline earth metals. During the process of performed studies there was found that the greatest degree of extraction of N-nitrosamines from the urine by the method of headspace analysis is achieved if using the salting-out agent in an amount of 16 g of sodium sulfate and for N-nitrosodimethylamine is 99%, for N-nitrosodiethylamine--100%.

  13. Rapid analysis of dissolved methane, ethylene, acetylene and ethane using partition coefficients and headspace-gas chromatography.

    Lomond, Jasmine S; Tong, Anthony Z

    2011-01-01

    Analysis of dissolved methane, ethylene, acetylene, and ethane in water is crucial in evaluating anaerobic activity and investigating the sources of hydrocarbon contamination in aquatic environments. A rapid chromatographic method based on phase equilibrium between water and its headspace is developed for these analytes. The new method requires minimal sample preparation and no special apparatus except those associated with gas chromatography. Instead of Henry's Law used in similar previous studies, partition coefficients are used for the first time to calculate concentrations of dissolved hydrocarbon gases, which considerably simplifies the calculation involved. Partition coefficients are determined to be 128, 27.9, 1.28, and 96.3 at 30°C for methane, ethylene, acetylene, and ethane, respectively. It was discovered that the volume ratio of gas-to-liquid phase is critical to the accuracy of the measurements. The method performance can be readily improved by reducing the volume ratio of the two phases. Method validation shows less than 6% variation in accuracy and precision except at low levels of methane where interferences occur in ambient air. Method detection limits are determined to be in the low ng/L range for all analytes. The performance of the method is further tested using environmental samples collected from various sites in Nova Scotia.

  14. Analysis of carbonyl compounds via headspace solid-phase microextraction with on-fiber derivatization and gas chromatographic-ion trap tandem mass spectrometric determination of their O-(2,3,4,5,6-pentafluorobenzyl)oxime derivatives

    Schmarr, Hans-Georg [Dienstleistungszentrum Laendlicher Raum (DLR) Rheinpfalz, Breitenweg 71, D-67435 Neustadt an der Weinstrasse (Germany)], E-mail: hans-georg.schmarr@dlr.rlp.de; Potouridis, Theodoros; Ganss, Sebastian; Sang, Wei; Koepp, Benedikt; Bokuz, Ursula; Fischer, Ulrich [Dienstleistungszentrum Laendlicher Raum (DLR) Rheinpfalz, Breitenweg 71, D-67435 Neustadt an der Weinstrasse (Germany)

    2008-06-09

    An improved method for the analysis of carbonyls is described utilizing a headspace solid-phase microextraction (HS-SPME) step and on-fiber derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) hydrochloride. Thermal desorption of the oxime derivatives formed on the fiber is followed by gas chromatographic separation coupled to an ion trap tandem mass spectrometer (GC-ITMS). Selecting specific fragment ions within the electron ionization (EI{sup +}) mass spectra of these oxime derivatives as precursor ions for MS-MS fragmentation provides a suitable method for the target analysis of individual carbonyl classes, such as alkanals, (E)-2-alkenals, (E,E)-2,4-alkadienals, and others. Retention indices on polar as well as on apolar stationary phases along with EI{sup +} mass spectra patterns are presented for a large set of oxime derivatives, giving valuable information needed for unambiguous assignment of substances in complex sample matrices. The fast sample preparation and derivatization step via HS-SPME can be automated and is applicable to a variety of biological samples and foodstuffs, allowing rapid and sensitive screening analyses of important aldehydic biomarkers and aroma active compounds.

  15. Chemometric strategy for automatic chromatographic peak detection and background drift correction in chromatographic data.

    Yu, Yong-Jie; Xia, Qiao-Ling; Wang, Sheng; Wang, Bing; Xie, Fu-Wei; Zhang, Xiao-Bing; Ma, Yun-Ming; Wu, Hai-Long

    2014-09-12

    Peak detection and background drift correction (BDC) are the key stages in using chemometric methods to analyze chromatographic fingerprints of complex samples. This study developed a novel chemometric strategy for simultaneous automatic chromatographic peak detection and BDC. A robust statistical method was used for intelligent estimation of instrumental noise level coupled with first-order derivative of chromatographic signal to automatically extract chromatographic peaks in the data. A local curve-fitting strategy was then employed for BDC. Simulated and real liquid chromatographic data were designed with various kinds of background drift and degree of overlapped chromatographic peaks to verify the performance of the proposed strategy. The underlying chromatographic peaks can be automatically detected and reasonably integrated by this strategy. Meanwhile, chromatograms with BDC can be precisely obtained. The proposed method was used to analyze a complex gas chromatography dataset that monitored quality changes in plant extracts during storage procedure. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Volatilizable Biogenic Organic Compounds (VBOCs with two dimensional Gas Chromatography-Time of Flight Mass Spectrometry (GC × GC-TOFMS: sampling methods, VBOC complexity, and chromatographic retention data

    C. Chen

    2012-02-01

    Full Text Available Two dimensional gas chromatography (GC × GC with detection by time-of-flight mass spectrometry (TOFMS was applied in the rapid analysis of air samples containing highly complex mixtures of volatilizable biogenic organic compounds (VBOCs. VBOC analytical methodologies are briefly reviewed, and optimal conditions are discussed for sampling with both adsorption/thermal desorption (ATD cartridges and solid-phase microextraction (SPME fibers. Air samples containing VBOC emissions from leaves of two tree species (Cedrus atlantica and Calycolpus moritzianus were obtained by both ATD and SPME. The optimized gas chromatographic conditions utilized a 45 m, 0.25 mm I.D. low-polarity primary column (DB-VRX, 1.4 μm film and a 1.5 m, 0.25 mm I.D. polar secondary column (StabilwaxTM, 0.25 μm film. Excellent separation was achieved in a 36 min temperature programmed GC × GC chromatogram. Thousands of VBOC peaks were present in the sample chromatograms; hundreds of tentative identifications by NIST mass spectral matching are provided. Very few of the tentatively identified compounds are currently available as authentic standards. Minimum detection limit values for a 5 l ATD sample were 3.5 pptv (10 ng m−3 for isoprene, methyl vinyl ketone, and methacrolein, and ~1.5 pptv (~10 ng m−3 for monoterpenes and sesquiterpenes. Kovats-type chromatographic retention index values on the primary column and relative retention time values on the secondary column are provided for 21 standard compounds and for 417 tentatively identified VBOCs. 19 of the 21 authentic standard compounds were found in one of the Cedrus atlantica SPME samples. In addition, easily quantifiable levels of at least 13 sesquiterpenes were found in an ATD sample obtained from a branch enclosure of Calycolpus moritzianus. Overall, the results obtained via GC × GC-TOFMS highlight an extreme, and largely uncharacterized diversity of VBOCs, consistent with the hypothesis that sesquiterpenes and

  17. Volatilizable Biogenic Organic Compounds (VBOCs) with two dimensional Gas Chromatography-Time of Flight Mass Spectrometry (GC × GC-TOFMS): sampling methods, VBOC complexity, and chromatographic retention data

    Pankow, J. F.; Luo, W.; Melnychenko, A. N.; Barsanti, K. C.; Isabelle, L. M.; Chen, C.; Guenther, A. B.; Rosenstiel, T. N.

    2012-02-01

    Two dimensional gas chromatography (GC × GC) with detection by time-of-flight mass spectrometry (TOFMS) was applied in the rapid analysis of air samples containing highly complex mixtures of volatilizable biogenic organic compounds (VBOCs). VBOC analytical methodologies are briefly reviewed, and optimal conditions are discussed for sampling with both adsorption/thermal desorption (ATD) cartridges and solid-phase microextraction (SPME) fibers. Air samples containing VBOC emissions from leaves of two tree species (Cedrus atlantica and Calycolpus moritzianus) were obtained by both ATD and SPME. The optimized gas chromatographic conditions utilized a 45 m, 0.25 mm I.D. low-polarity primary column (DB-VRX, 1.4 μm film) and a 1.5 m, 0.25 mm I.D. polar secondary column (StabilwaxTM, 0.25 μm film). Excellent separation was achieved in a 36 min temperature programmed GC × GC chromatogram. Thousands of VBOC peaks were present in the sample chromatograms; hundreds of tentative identifications by NIST mass spectral matching are provided. Very few of the tentatively identified compounds are currently available as authentic standards. Minimum detection limit values for a 5 l ATD sample were 3.5 pptv (10 ng m-3) for isoprene, methyl vinyl ketone, and methacrolein, and ~1.5 pptv (~10 ng m-3) for monoterpenes and sesquiterpenes. Kovats-type chromatographic retention index values on the primary column and relative retention time values on the secondary column are provided for 21 standard compounds and for 417 tentatively identified VBOCs. 19 of the 21 authentic standard compounds were found in one of the Cedrus atlantica SPME samples. In addition, easily quantifiable levels of at least 13 sesquiterpenes were found in an ATD sample obtained from a branch enclosure of Calycolpus moritzianus. Overall, the results obtained via GC × GC-TOFMS highlight an extreme, and largely uncharacterized diversity of VBOCs, consistent with the hypothesis that sesquiterpenes and other compounds

  18. Selective removal of water in purge and cold-trap capillary gas chromatographic analysis of volatile organic traces in aqueous samples

    Noij, T.H.M.; van Es, A.J.J.; Cramers, C.A.M.G.; Rijks, J.A.; Dooper, R.P.M.

    1987-01-01

    The design and features of an on-line purge and cold-trap pre-concentration device for rapid analysis of volatile organic compounds in aqueous samples are discussed. Excessive water is removed from the purge gas by a condenser or a water permeable membrane in order to avoid blocking of the capillary

  19. Capillary gas chromatographic analysis of mycolic acid cleavage products, cellular fatty acids, and alcohols of Mycobacterium xenopi.

    Luquin, M; Lopez, F; Ausina, V

    1989-01-01

    The fatty acids, alcohols, and mycolic acids of 26 strains of Mycobacterium xenopi were studied by capillary gas chromatography and thin-layer chromatography. All strains contained alpha-, keto-, and omega-carboxymycolates. The primary mycolic acid cleavage product was hexacosanoic acid. The fatty acid patterns and, especially, the presence of 2-docosanol are characteristic markers of M. xenopi.

  20. Gas chromatographic analysis of Tri-N-Octyl-Phosphine oxide (Topo) in D2EHPA-Topo-Kerosene mixtures

    Perez Garcia, M.

    1973-01-01

    A study about the minimum limit of TOPO, detectable by gas chromatography in an organic phase formed by D2EHPA and kerosene is carried out. The retention time and response factor under the same conditions are also studied. Octacosane has been used as a reference hydrocarbon. (Author) 8 refs

  1. Gas chromatographic quadrupole time-of-flight full scan high resolution mass spectrometric screening of human urine in antidoping analysis

    Abushareeda, Wadha; Lyris, Emmanouil; Kraiem, Suhail; Wahaibi, Aisha Al; Alyazidi, Sameera; Dbes, Najib; Lommen, Arjen; Nielen, Michel; Horvatovich, Peter L.; Alsayrafi, Mohammed; Georgakopoulos, Costas

    2017-01-01

    This paper presents the development and validation of a high-resolution full scan (FS) electron impact ionization (EI) gas chromatography coupled to quadrupole Time-of-Flight mass spectrometry (GC/QTOF) platform for screening anabolic androgenic steroids (AAS) in human urine samples. The World

  2. Gas chromatographic quadrupole time-of-flight full scan high resolution mass spectrometric screening of human urine in antidoping analysis

    Abushareeda, Wadha; Lyris, Emmanouil; Kraiem, Suhail; Wahaibi, Aisha Al; Alyazidi, Sameera; Dbes, Najib; Lommen, Arjen; Nielen, Michel; Horvatovich, Peter L.; Alsayrafi, Mohammed; Georgakopoulos, Costas

    2017-01-01

    This paper presents the development and validation of a high-resolution full scan (FS) electron impact ionization (EI) gas chromatography coupled to quadrupole Time-of-Flight mass spectrometry (GC/QTOF) platform for screening anabolic androgenic steroids (AAS) in human urine samples. The World

  3. A charge-polarized porous metal-organic framework for gas chromatographic separation of alcohols from water.

    Sun, Jian-Ke; Ji, Min; Chen, Cheng; Wang, Wu-Gen; Wang, Peng; Chen, Rui-Ping; Zhang, Jie

    2013-02-25

    A bipyridinium ligand with a charge separated skeleton has been introduced into a metal-organic framework to yield a porous material with charge-polarized pore space, which exhibits selective adsorption for polar guest molecules and can be further used in gas chromatography for the separation of alcohol-water mixtures.

  4. Test Structures for Rapid Prototyping of Gas and Pressure Sensors

    Buehler, M.; Cheng, L. J.; Martin, D.

    1996-01-01

    A multi-project ceramic substrate was used in developing a gas sensor and pressure sensor. The ceramic substrate cantained 36 chips with six variants including sensors, process control monitors, and an interconnect ship. Tha gas sensor is being developed as an air quality monitor and the pressure gauge as a barometer.

  5. Chromatographic and biological aspects of organomercurials

    Fishbein, L

    1970-01-01

    A thorough review on the biological and chromatographic aspects of methylmercury, phenylmercurials, and miscellaneous organomercurials is presented. Areas covered include ecology, epidemiology, paper chromatography, thin-layer chromatography, gas chromatography, metabolism and toxicity, and environmental degradation. 183 references.

  6. Determination of polycyclic aromatic hydrocarbons (PAHs). gas chromatographic method; Determinazione degli idrocarburi policiclici aromatici (IPA). Metodo gascaromatografico

    Menichini, E; Viviano, G [Istituto Superiore di Sanita` , Rome (Italy). Lab. di Igiene Ambientale

    1997-12-01

    The method enables the determination of 4- to 6- ring PAHs and particularly of carcinogenic PAHs regulated in Italy. This revision is based on the results of a national collaborative study. Sample extract, obtained by a method described in a previous report (Rapporto ISTISAN: 90/33) is cleaned up by thin layer chromatography and analysed by gas chromatography; identification is confirmed by mass spectrometry. An intralaboratory quality control program is described.

  7. Rapid estimation of the organic sulphur content of kerogens, coals and asphaltenes by pyrolysis-gas chromatography

    Sinninghe Damsté, J.S.; Eglinton, T.I.; Kohnen, M.E.L.; Leeuw, J.W. de

    1990-01-01

    A pyrolysis-gas Chromatographic (py-g.c.) method for estimation of the Sorg/C ratio in kerogens and other forms of sedimentary macromolecular organic matter is described. The method is based upon flash pyrolysis at 610 °C for 10s and areal integration of the FID peaks attributed to

  8. Pulse gas chromatographic study of adsorption of substituted aromatics and heterocyclic molecules on MIL-47 at zero coverage.

    Duerinck, Tim; Couck, Sarah; Vermoortele, Frederik; De Vos, Dirk E; Baron, Gino V; Denayer, Joeri F M

    2012-10-02

    The low coverage adsorptive properties of the MIL-47 metal organic framework toward aromatic and heterocyclic molecules are reported in this paper. The effect of molecular functionality and size on Henry adsorption constants and adsorption enthalpies of alkyl and heteroatom functionalized benzene derivates and heterocyclic molecules was studied using pulse gas chromatography. By means of statistical analysis, experimental data was analyzed and modeled using principal component analysis and partial least-squares regression. Structure-property relationships were established, revealing and confirming several trends. Among the molecular properties governing the adsorption process, vapor pressure, mean polarizability, and dipole moment play a determining role.

  9. Comparison of gas chromatographic and gravimetric methods for quantization of total fat and fatty acids in foodstuffs

    Sabria Aued-Pimentel

    2010-01-01

    Full Text Available Different methods to determine total fat (TF and fatty acids (FA, including trans fatty acids (TFA, in diverse foodstuffs were evaluated, incorporating gravimetric methods and gas chromatography with flame ionization detector (GC/FID, in accordance with a modified AOAC 996.06 method. Concentrations of TF and FA obtained through these different procedures diverged (p< 0.05 and TFA concentrations varied beyond 20 % of the reference values. The modified AOAC 996.06 method satisfied both accuracy and precision, was fast and employed small amounts of low toxicity solvents. Therefore, the results showed that this methodology is viable to be adopted in Brazil for nutritional labeling purposes.

  10. Determination of plant stanols and plant sterols in phytosterol enriched foods with a gas chromatographic-flame ionization detection method: NMKL collaborative study.

    Laakso, Päivi H

    2014-01-01

    This collaborative study with nine participating laboratories was conducted to determine the total plant sterol and/or plant stanol contents in phytosterol fortified foods with a gas chromatographic method. Four practice and 12 test samples representing mainly commercially available foodstuffs were analyzed as known replicates. Twelve samples were enriched with phytosterols, whereas four samples contained only natural contents of phytosterols. The analytical procedure consisted of two alternative approaches: hot saponification method, and acid hydrolysis treatment prior to hot saponification. As a result, sterol/stanol compositions and contents in the samples were measured. The amounts of total plant sterols and total plant stanols varying from 0.005 to 8.04 g/100 g product were statistically evaluated after outliers were eliminated. The repeatability RSD (RSDr) varied from 1.34 to 17.13%. The reproducibility RSD (RSDR) ranged from 3.03 to 17.70%, with HorRat values ranging from 0.8 to 2.1. When only phytosterol enriched food test samples are considered, the RSDr ranged from 1.48 to 6.13%, the RSD, ranged from 3.03 to 7.74%, and HorRat values ranged from 0.8 to 2.1. Based on the results of this collaborative study, the study coordinator concludes the method is fit for its purpose.

  11. Comparison of multiple linear regression, partial least squares and artificial neural networks for prediction of gas chromatographic relative retention times of trimethylsilylated anabolic androgenic steroids.

    Fragkaki, A G; Farmaki, E; Thomaidis, N; Tsantili-Kakoulidou, A; Angelis, Y S; Koupparis, M; Georgakopoulos, C

    2012-09-21

    The comparison among different modelling techniques, such as multiple linear regression, partial least squares and artificial neural networks, has been performed in order to construct and evaluate models for prediction of gas chromatographic relative retention times of trimethylsilylated anabolic androgenic steroids. The performance of the quantitative structure-retention relationship study, using the multiple linear regression and partial least squares techniques, has been previously conducted. In the present study, artificial neural networks models were constructed and used for the prediction of relative retention times of anabolic androgenic steroids, while their efficiency is compared with that of the models derived from the multiple linear regression and partial least squares techniques. For overall ranking of the models, a novel procedure [Trends Anal. Chem. 29 (2010) 101-109] based on sum of ranking differences was applied, which permits the best model to be selected. The suggested models are considered useful for the estimation of relative retention times of designer steroids for which no analytical data are available. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Gas chromatographic determination of polycyclic aromatic hydrocarbons in water and smoked rice samples after solid-phase microextraction using multiwalled carbon nanotube loaded hollow fiber.

    Matin, Amir Abbas; Biparva, Pourya; Gheshlaghi, Mohammad

    2014-12-29

    A novel solid-phase microextraction fiber was prepared based on multiwalled carbon nanotubes (MWCNTs) loaded on hollow fiber membrane pores. Stainless steel wire was used as unbreakable support. The major advantages of the proposed fiber are its (a) high reproducibility due to the uniform structure of the hollow fiber membranes, (b) high extraction capacity related to the porous structure of the hollow fiber and outstanding adsorptive characteristics of MWCNTs. The proposed fiber was applied for the microextraction of five representative polycyclic aromatic hydrocarbons (PAHs) from aqueous media (river and hubble-bubble water) and smoked rice samples followed by gas chromatographic determination. Analytical merits of the method, including high correlation coefficients [(0.9963-0.9992) and (0.9982-0.9999)] and low detection limits [(9.0-13.0ngL(-1)) and (40.0-150.0ngkg(-1))] for water and rice samples, respectively, made the proposed method suitable for the ultra-trace determination of PAHs. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Acidic methanolysis v. alkaline saponification in gas chromatographic characterization of mycobacteria: differentiation between Mycobacterium avium-intracellulare and Mycobacterium gastri.

    Larsson, L

    1983-08-01

    Mycobacterium avium-intracellulare and M.gastri were analyzed with capillary gas chromatography after each strain had been subjected to acidic methanolysis or to alkaline saponification followed by methylation. Prominent peaks of myristic, palmitoleic, palmitic, oleic, stearic and tuberculostearic acids were found in the chromatograms of both species, whereas 2-octadecanol and 2-eicosanol were detected only in M. avium-intracellulare. In initial runs, both of the derivatization principles yielded virtually identical chromatograms for a given strain. After repeated injections of extracts from alkaline saponification, however, the alcohol peaks showed pronounced tailing and finally almost disappeared from the chromatograms. This disadvantage, which was not observed when only acid methanolysis was used, could be overcome with trifluoroacetylation. Restored peak shape of the underivatized alcohols could be achieved by washing the cross-linked stationary phase in the capillary tubing with organic solvents. The study demonstrated the importance of conditions which enable separation of 2-octadecanol and 2-eicosanol when gas chromatography is used for species identification of mycobacteria.

  14. Loop system for creating jet fuel vapor standards used in the calibration of infrared spectrophotometers and gas chromatographs.

    Reboulet, James; Cunningham, Robert; Gunasekar, Palur G; Chapman, Gail D; Stevens, Sean C

    2009-02-01

    A whole body inhalation study of mixed jet fuel vapor and its aerosol necessitated the development of a method for preparing vapor only standards from the neat fuel. Jet fuel is a complex mixture of components which partitions between aerosol and vapor when aspirated based on relative volatility of the individual compounds. A method was desired which could separate the vapor portion from the aerosol component to prepare standards for the calibration of infrared spectrophotometers and a head space gas chromatography system. A re-circulating loop system was developed which provided vapor only standards whose composition matched those seen in an exposure system. Comparisons of nominal concentrations in the exposure system to those determined by infrared spectrophotometry were in 92-95% agreement. Comparison of jet fuel vapor concentrations determined by infrared spectrophotometry compared to head space gas chromatography yielded a 93% overall agreement in trial runs. These levels of agreement show the loop system to be a viable method for creating jet fuel vapor standards for calibrating instruments.

  15. A single gas chromatograph for accurate atmospheric mixing ratio measurements of CO2, CH4, N2O, SF6 and CO

    H. A. J. Meijer

    2009-09-01

    Full Text Available We present an adapted gas chromatograph capable of measuring simultaneously and semi-continuously the atmospheric mixing ratios of the greenhouse gases CO2, CH4, N2O and SF6 and the trace gas CO with high precision and long-term stability. The novelty of our design is that all species are measured with only one device, making it a very cost-efficient system. No time lags are introduced between the measured mixing ratios. The system is designed to operate fully autonomously which makes it ideal for measurements at remote and unmanned stations. Only a small amount of sample air is needed, which makes this system also highly suitable for flask air measurements. In principle, only two reference cylinders are needed for daily operation and only one calibration per year against international WMO standards is sufficient to obtain high measurement precision and accuracy. The system described in this paper is in use since May 2006 at our atmospheric measurement site Lutjewad near Groningen, The Netherlands at 6°21´ E, 53°24´N, 1 m a.s.l. Results show the long-term stability of the system. Observed measurement precisions at our remote research station Lutjewad were: ±0.04 ppm for CO2, ±0.8 ppb for CH4, ±0.8 ppb for CO, ±0.3 ppb for N2O, and ±0.1 ppt for SF6. The ambient mixing ratios of all measured species as observed at station Lutjewad for the period of May 2007 to August 2008 are presented as well.

  16. Comparison of gravimetric and gas chromatographic methods for assessing performance of textile materials against liquid pesticide penetration.

    Shaw, Anugrah; Abbi, Ruchika

    2004-01-01

    Penetration of liquid pesticides through textile materials is a criterion for determining the performance of protective clothing used by pesticide handlers. The pipette method is frequently used to apply liquid pesticides onto textile materials to measure penetration. Typically, analytical techniques such as Gas Chromatography (GC) are used to measure percentage penetration. These techniques are labor intensive and costly. A simpler gravimetric method was developed, and tests were conducted to compare the gravimetric and GC methods of analysis. Three types of pesticide formulations and 4 fabrics were used for the study. Diluted pesticide formulations were pipetted onto the test specimens and percentage penetration was measured using the 2 methods. For homogeneous formulation, the results of the two methods were fairly comparable. However, due to the filtering action of the textile materials, there were differences in the percentage penetration between the 2 methods for formulations that were not homogeneous.

  17. Evaluation of advanced gas chromatographs for on-site analysis. Final CRADA report for number Y-1295-0374

    Wise, M.B.; Guerin, M.R.; Palausky, A.; Merriweather, R. [Lockheed Martin Energy Research, Oak Ridge, TN (United States); Forsberg, R.E. [Mine Safety Appliances-Baseline Industries, Lyons, CO (United States)

    1997-02-21

    The EKHO gas chromatography (GC) is being marketed by Mine Safety Appliances as an instrument for on-site environmental analysis and for process applications. This GC utilizes a unique bundled capillary column produced in Russia that provides very fast analysis and a wide linear dynamic range. Oak Ridge National Laboratory (ORNL) has been involved in a CRADA with Mine Safety Appliances in order to evaluate the analytical performance of the EKHO GC and is suitability for on-site environmental applications. Tests that were performed at ORNL included the analysis of air, water, and soil samples for aromatic hydrocarbons including benzene, toluene, xylene, and ethylbenzene (BTEX). These compounds were selected in order to simulate contamination by gasoline and other petroleum fuels. Performance factors that were studied included the instrument detection limits, the linearity, dynamic range, and precision for replicate samples. Other factors that were evaluated include the ease of set-up and operation.

  18. Portable rapid gas content measurement - an opportunity for a step change in the coal industry?

    Beamish, Basil; Kizil, Mehmet; Gu, Ming

    2013-01-01

    The last major advance in gas content measurement for coal seams was the introduction of the quick crush technique in the early 1990s. This is a laboratory test method that has proven very reliable over the years. Recent laboratory testing using a portable quick crushing device, known as the portable gas content analyser, has produced consistent gas content results for a set of core samples obtained from a single borehole that intersected four coal seams. The retained gas content values obtained for the seams show the same increasing gas content pattern and gas composition change with depth as the standard quick crush technique. Use of the portable gas content analyser provides the opportunity to produce rapid, reliable gas content measurement of coal that could be developed for assessing gas compliance cores and outburst-prone conditions at a mine site.

  19. Measurement of Activity Coefficients of Solvents in Poly ( ethylene oxide ) Using Gas-Chromatographic Method and Correlation by Polymer-ASOG; Poriechirenokishido chu no yobai katsuryo keisu no gasukuromatogurafu ho ni yoru sokutei to Polymer-ASOG ni yoru sokan

    Tochigi, K.; Kurita, S.; Ohashi, M. [Yuki Gosei Kogyo Co. LTd., (Japan); Kojima, K. [Nihon University, Tokyo (Japan). Department of Industrial Chemistry

    1997-09-01

    Infinite dilution activity coefficients (353.15-393.15 K) of six solvents (benzene, toluene, p-xylene, cyclohexane, acetone and methylethylketone) and activity coefficient at finite concentrations (353.15 K, 373.15 K) of these solvents in poly (ethylene oxide) are measured using gas-chromatographic method. The experimental data are then correlated by a polymer-ASOG model. 18 refs., 2 figs., 3 tabs.

  20. Evaluation of Pentachlorophenol Residues in Some Hygienic Papers Prepared from Virgin and Secondary Pulp by Electron Capture Gas Chromatographic Method

    Behrouz Akbari-adergani

    2016-01-01

    Full Text Available In this study, residual amount of pentachlorophenol (PCP as the most important paper preservative, which is extremely hazardous pollutant, was determined in some tissue papers and napkins. Twenty-five samples of two producing hygienic paper factories prepared from virgin and secondary pulp were analyzed for the presence of trace amount of PCP. The analytical procedure involved direct extraction of PCP from hygienic paper and its determination by gas chromatography with electron capture detection. The statistical results for the analysis of all samples revealed that there were significant differences between mean of PCP in hygienic papers prepared from virgin and secondary pulp (P<0.05. This method gave recoveries of 86-98% for hygienic paper made from virgin pulp and 79-92% for hygienic paper made from secondary pulp. The limit of detection (LOD and limit of quantification (LOQ for PCP were 6.3 and 21.0 mg/kg, respectively. The analytical method has the requisite sensitivity, accuracy, precision and specificity to assay PCP in hygienic papers. This study demonstrates a concern with exposition to PCP considering that hygienic paper is largely consumed in the society.

  1. Gas chromatographic sulphur speciation in heavy crude oil using a modified standard D5623 method and microfluidic Deans switching.

    Heshka, Nicole E; Choy, Joanne M; Chen, Jinwen

    2017-12-29

    A modification to American Society for Testing and Materials (ASTM) method D5623 is proposed to enable successful and repeatable analysis of heavy crude oil samples. A two-dimensional gas chromatography configuration was implemented, with separation of sulphur compounds occurring on two columns. A Deans switch is used to enable heart-cutting of volatile sulphur compounds onto a DB-Sulfur stationary phase, and separation occurs concurrently with the backflushing of the primary column. The use of a sulphur-selective detector increases selectivity, and 22 volatile sulphur species are quantified in less than 15min, which is almost half the time of the original ASTM method. Samples ranging from light distillation cuts to whole crudes (boiling from 100°C to >750°C) were analyzed with minimal sample preparation. The calculated limit of detection was 0.7mg/kg, repeatability was 3% relative standard deviation (RSD), and a linear range of 1-250mg/kg was obtained, with an R 2 value of 0.994 or better, depending on the compound. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

  2. Capillary gas chromatographic separation of organic bases using a pH-adjusted basic water stationary phase.

    Darko, Ernest; Thurbide, Kevin B

    2016-09-23

    The use of a pH-adjusted water stationary phase for analyzing organic bases in capillary gas chromatography (GC) is demonstrated. Through modifying the phase to typical values near pH 11.5, it is found that various organic bases are readily eluted and separated. Conversely, at the normal pH 7 operating level, they are not. Sodium hydroxide is found to be a much more stable base than ammonium hydroxide for altering the pH due to the higher volatility and evaporation of the latter. In the basic condition, such analytes are not ionized and are observed to produce good peak shapes even for injected masses down to about 20ng. By comparison, analyses on a conventional non-polar capillary GC column yield more peak tailing and only analyte masses of 1μg or higher are normally observed. Through carefully altering the pH, it is also found that the selectivity between analytes can be potentially further enhanced if their respective pKa values differ sufficiently. The analysis of different pharmaceutical and petroleum samples containing organic bases is demonstrated. Results indicate that this approach can potentially offer unique and beneficial selectivity in such analyses. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Determination of methyl mercury by aqueous phase Eehylation, followed by gas chromatographic separation with cold vapor atomic fluorescence detection

    De Wild, John F.; Olsen, Mark L.; Olund, Shane D.

    2002-01-01

    A recent national sampling of streams in the United States revealed low methyl mercury concentrations in surface waters. The resulting median and mean concentrations, calculated from 104 samples, were 0.06 nanograms per liter (ng/L) and 0.15 ng/L, respectively. This level of methyl mercury in surface water in the United States has created a need for analytical techniques capable of detecting sub-nanogram per liter concentrations. In an attempt to create a U.S. Geological Survey approved method, the Wisconsin District Mercury Laboratory has adapted a distillation/ethylation/ gas-phase separation method with cold vapor atomic fluorescence spectroscopy detection for the determination of methyl mercury in filtered and unfiltered waters. This method is described in this report. Based on multiple analyses of surface water and ground-water samples, a method detection limit of 0.04 ng/L was established. Precision and accuracy were evaluated for the method using both spiked and unspiked ground-water and surface-water samples. The percent relative standard deviations ranged from 10.2 to 15.6 for all analyses at all concentrations. Average recoveries obtained for the spiked matrices ranged from 88.8 to 117 percent. The precision and accuracy ranges are within the acceptable method-performance limits. Considering the demonstrated detection limit, precision, and accuracy, the method is an effective means to quantify methyl mercury in waters at or below environmentally relevant concentrations

  4. Rapid thin-layer chromatographic photodensitometric method for the determination of metoclopramide and clebopride in the presence of some of their metabolic products.

    Huizing, G; Beckett, A H; Segura, J

    1979-04-21

    Metoclopramide and its newly developed analogue clebopride, together with some of their metabolic products are quantitated, following extraction from biological tissues and fluids, and subsequent separation on silica gel thin-layer chromatographic plates. Diazotisation, followed by coupling with N-(1-naphthyl)ethylenediammonium dichloride, carried out on the thin-layer plate, is utilised for visualisation. The intensity of the spots is measured by photodensitometric analysis. The effect of variation of various experimental conditions is studied. The method has proven to be satisfactory for the measurement of 20 ng/ml of these compounds in biological material; the results are well within the accepted limits of deviation.

  5. Gas-chromatographic resolution of enantiomeric secondary alcohols. Stereoselective reductive metabolism of ketones in rabbit-liver cytosol.

    Gal, J; DeVito, D; Harper, T W

    1981-01-01

    Chiral secondary alcohols were treated with (S)-(-)-1-phenylethyl isocyanate. For each racemic alcohol, the resulting diastereomeric urethane derivatives were resolved on flexible fused-silica capillary GLC columns with retention times of 15 min or less. Derivatization of individual enantiomers showed that the urethane derivatives of (R)-(-)-2-octanol, (R)-(+)-1-phenylethyl alcohol, and (S)-(+)-2,2,2-trifluoro-1-phenylethanol are eluted before the corresponding diastereomers. The procedure is simple and rapid, and is suitable for the determination of the enantiomeric composition of chiral alcohols extracted from biological media. A series of aliphatic alcohols, aryl alkyl carbinols, and arylalkyl alkyl carbinols were resolved with the procedure, and the degree of resolution varied from good to excellent. Eight achiral ketones were incubated, individually, with rabbit-liver 90,000 g supernatant fractions, and the enantiomeric composition of the alcohol metabolites was determined with the GLC procedure. The reductions proceeded with high stereoselectivity to give alcohol products of 90% or greater enantiomeric purity. The reduction of 2-octanone and acetophenone gave predominant alcohols of (S)-configuration, in agreement with the Baumann-Prelog rule. The configuration of the predominant alcohols arising in the reduction of the remainder of the ketones could not be firmly established, but the evidence suggests that they are also of the (S)-configuration. Fluorine or methyl substitution in the ortho position of acetophenone produced an increase in the stereoselectivity, and the alcohol produced from ortho-methylacetophenone was enantiomerically greater than 99% pure.

  6. Nanoparticle-coated micro-optofluidic ring resonator as a detector for microscale gas chromatographic vapor analysis.

    Scholten, K; Collin, W R; Fan, X; Zellers, E T

    2015-05-28

    A vapor sensor comprising a nanoparticle-coated microfabricated optofluidic ring resonator (μOFRR) is introduced. A multilayer film of polyether functionalized, thiolate-monolayer-protected gold nanoparticles (MPN) was solvent cast on the inner wall of the hollow cylindrical SiOxμOFRR resonator structure, and whispering gallery mode (WGM) resonances were generated with a 1550 nm tunable laser via an optical fiber taper. Reversible shifts in the WGM resonant wavelength upon vapor exposure were detected with a photodetector. The μOFRR chip was connected to a pair of upstream etched-Si chips containing PDMS-coated separation μcolumns and calibration curves were generated from the peak-area responses to five volatile organic compounds (VOCs). Calibration curves were linear, and the sensitivities reflected the influence of analyte volatility and analyte-MPN functional group affinity. Sorption-induced changes in film thickness apparently dominate over changes in the refractive index of the film as the determinant of responses for all VOCs. Peaks from the MPN-coated μOFRR were just 20-50% wider than those from a flame ionization detector for similar μcolumn separation conditions, reflecting the rapid response of the sensor for VOCs. The five VOCs were baseline separated in <1.67 min, with detection limits as low as 38 ng.

  7. Nanoparticle-coated micro-optofluidic ring resonator as a detector for microscale gas chromatographic vapor analysis

    Scholten, K.; Collin, W. R.; Fan, X.; Zellers, E. T.

    2015-05-01

    A vapor sensor comprising a nanoparticle-coated microfabricated optofluidic ring resonator (μOFRR) is introduced. A multilayer film of polyether functionalized, thiolate-monolayer-protected gold nanoparticles (MPN) was solvent cast on the inner wall of the hollow cylindrical SiOx μOFRR resonator structure, and whispering gallery mode (WGM) resonances were generated with a 1550 nm tunable laser via an optical fiber taper. Reversible shifts in the WGM resonant wavelength upon vapor exposure were detected with a photodetector. The μOFRR chip was connected to a pair of upstream etched-Si chips containing PDMS-coated separation μcolumns and calibration curves were generated from the peak-area responses to five volatile organic compounds (VOCs). Calibration curves were linear, and the sensitivities reflected the influence of analyte volatility and analyte-MPN functional group affinity. Sorption-induced changes in film thickness apparently dominate over changes in the refractive index of the film as the determinant of responses for all VOCs. Peaks from the MPN-coated μOFRR were just 20-50% wider than those from a flame ionization detector for similar μcolumn separation conditions, reflecting the rapid response of the sensor for VOCs. The five VOCs were baseline separated in <1.67 min, with detection limits as low as 38 ng.

  8. Development of a gas-liquid chromatographic method for the analysis of fatty acid tryptamides in cocoa products.

    Hug, Bernadette; Golay, Pierre-Alain; Giuffrida, Francesca; Dionisi, Fabiola; Destaillats, Frédéric

    2006-05-03

    The determination of the occurrence and level of cocoa shells in cocoa products and chocolate is an important analytical issue. The recent European Union directive on cocoa and chocolate products (2000/36/EC) has not retained the former limit of a maximum amount of 5% of cocoa shells in cocoa nibs (based on fat-free dry matter), previously authorized for the elaboration of cocoa products such as cocoa mass. In the present study, we report a reliable gas-liquid chromatography procedure suitable for the determination of the occurrence of cocoa shells in cocoa products by detection of fatty acid tryptamides (FATs). The precision of the method was evaluated by analyzing nine different samples (cocoa liquors with different ranges of shells) six times (replicate repeatability). The variations of the robust coefficient of variation of the repeatability demonstrated that FAT(C22), FAT(C24), and total FATs are good markers for the detection of shells in cocoa products. The trueness of the method was evaluated by determining the FAT content in two spiked matrices (cocoa liquors and cocoa shells) at different levels (from 1 to 50 mg/100 g). A good relation was found between the results obtained and the spiking (recovery varied between 90 and 130%), and the linearity range was established between 1 and 50 mg/100 g in cocoa products. For total FAT contents of cocoa liquor containing 5% shells, the measurement uncertainty allows us to conclude that FAT is equal to 4.01 +/- 0.8 mg/100 g. This validated method is perfectly suitable to determine shell contents in cocoa products using FAT(C22), FAT(C24), and total FATs as markers. The results also confirmed that cocoa shells contain FAT(C24) and FAT(C22) in a constant ratio of nearly 2:1.

  9. An analytical method for trifluoroacetic Acid in water and air samples using headspace gas chromatographic determination of the methyl ester.

    Zehavi, D; Seiber, J N

    1996-10-01

    An analytical method has been developed for the determination of trace levels of trifluoroacetic acid (TFA), an atmospheric breakdown product of several of the hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) replacements for the chlorofluorocarbon (CFC) refrigerants, in water and air. TFA is derivatized to the volatile methyl trifluoroacetate (MTFA) and determined by automated headspace gas chromatography (HSGC) with electron-capture detection or manual HSGC using GC/MS in the selected ion monitoring (SIM) mode. The method is based on the reaction of an aqueous sample containing TFA with dimethyl sulfate (DMS) in concentrated sulfuric acid in a sealed headspace vial under conditions favoring distribution of MTFA to the vapor phase. Water samples are prepared by evaporative concentration, during which TFA is retained as the anion, followed by extraction with diethyl ether of the acidified sample and then back-extraction of TFA (as the anion) in aqueous bicarbonate solution. The extraction step is required for samples with a relatively high background of other salts and organic materials. Air samples are collected in sodium bicarbonate-glycerin-coated glass denuder tubes and prepared by rinsing the denuder contents with water to form an aqueous sample for derivatization and analysis. Recoveries of TFA from spiked water, with and without evaporative concentration, and from spiked air were quantitative, with estimated detection limits of 10 ng/mL (unconcentrated) and 25 pg/mL (concentrated 250 mL:1 mL) for water and 1 ng/m(3) (72 h at 5 L/min) for air. Several environmental air, fogwater, rainwater, and surface water samples were successfully analyzed; many showed the presence of TFA.

  10. Catalyst functionalized buffer sorbent pebbles for rapid separation of carbon dioxide from gas mixtures

    Aines, Roger D

    2015-03-31

    A method for separating CO.sub.2 from gas mixtures uses a slurried media impregnated with buffer compounds and coating the solid media with a catalyst or enzyme that promotes the transformation of CO.sub.2 to carbonic acid. Buffer sorbent pebbles with a catalyst or enzyme coating are provided for rapid separation of CO.sub.2 from gas mixtures.

  11. Catalyst functionalized buffer sorbent pebbles for rapid separation of carbon dioxide from gas mixtures

    Aines, Roger D.

    2013-03-12

    A method for separating CO.sub.2 from gas mixtures uses a slurried media impregnated with buffer compounds and coating the solid media with a catalyst or enzyme that promotes the transformation of CO.sub.2 to carbonic acid. Buffer sorbent pebbles with a catalyst or enzyme coating are provided for rapid separation of CO.sub.2 from gas mixtures.

  12. Microfabricated gas chromatograph for on-site determinations of TCE in indoor air arising from vapor intrusion. 2. Spatial/temporal monitoring.

    Kim, Sun Kyu; Burris, David R; Bryant-Genevier, Jonathan; Gorder, Kyle A; Dettenmaier, Erik M; Zellers, Edward T

    2012-06-05

    We demonstrate the use of two prototype Si-microfabricated gas chromatographs (μGC) for continuous, short-term measurements of indoor trichloroethylene (TCE) vapor concentrations related to the investigation of TCE vapor intrusion (VI) in two houses. In the first house, with documented TCE VI, temporal variations in TCE air concentrations were monitored continuously for up to 48 h near the primary VI entry location under different levels of induced differential pressure (relative to the subslab). Concentrations ranged from 0.23 to 27 ppb by volume (1.2-150 μg/m(3)), and concentration trends agreed closely with those determined from concurrent reference samples. The sensitivity and temporal resolution of the measurements were sufficiently high to detect transient fluctuations in concentration resulting from short-term changes in variables affecting the extent of VI. Spatial monitoring showed a decreasing TCE concentration gradient with increasing distance from the primary VI entry location. In the second house, with no TCE VI, spatial profiles derived from the μGC prototype data revealed an intentionally hidden source of TCE within a closet, demonstrating the capability for locating non-VI sources. Concentrations measured in this house ranged from 0.51 to 56 ppb (2.7-300 μg/m(3)), in good agreement with reference method values. This first field demonstration of μGC technology for automated, near-real-time, selective VOC monitoring at low- or subppb levels augurs well for its use in short- and long-term on-site analysis of indoor air in support of VI assessments.

  13. Development of a Small, Inexpensive, and Field-deployable Gas Chromatograph for the Automated Collection, Separation, and Analysis of Gas-phase Organic Compounds

    Skog, K.; Xiong, F.; Gentner, D. R.

    2017-12-01

    The identification and quantification of gas-phase organic compounds, like volatile organic compounds (VOCs), in the atmosphere relies on separation of complex mixtures and sensitive detection. Gas chromatography (GC) is widely applied, but relies on the need for high-purity compressed gases for separation and, often for detection. We have developed a low-cost, compact GC-based system for the collection and quantitative chemical speciation of complex mixtures of common atmospheric VOCs without the need for compressed high-purity gases or expensive detectors. We present results of lab and field testing against a commercially-available GC system. At optimized linear velocities challenging VOC pairs of similar volatility were resolved within 30 minutes, including n- and i-pentane; n-pentane and isoprene; and ethylbenzene and m/p-xylene. For 5-30 minute samples, we observe ppt-level detection limits for common VOCs such as benzene, toluene, ethylbenzene, xylenes, alpha-pinene, and limonene. We also present results of in-field use for VOC measurements. In all, this instrument is accurate, precise, small, and inexpensive (<$2500). Its lack of compressed gas cylinders make it ideal for field deployment and has been demonstrated to produce similar quality data to available GC technology.

  14. A solid-phase microextraction-gas chromatographic approach combined with triple quadrupole mass spectrometry for the assay of carbamate pesticides in water samples.

    Cavaliere, Brunella; Monteleone, Marcello; Naccarato, Attilio; Sindona, Giovanni; Tagarelli, Antonio

    2012-09-28

    A simple and sensitive method was developed for the quantification of five carbamate pesticides in water samples using solid phase microextraction (SPME) combined with gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS). The performance of five SPME fibers was tested in univariate mode whereas the other variables affecting the efficiency of SPME analysis were optimized by the multivariate approach of design of experiment (DoE) and, in particular, a central composite design (CCD) was applied. The optimum working conditions in terms of response values were achieved by performing analysis with polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber in immersion mode for 45min at room temperature with addition of NaCl (10%). The multivariate chemometric approach was also used to explore the chromatographic behavior of the carbamates and to evaluate the importance of each variable investigated. An overall appraisement of results shows that the factor which gave a statistically significant effect on the response was only the injection temperature. Identification and quantification of carbamates was performed by using a gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS) system in multiple reaction monitoring (MRM) acquisition. Since the choice of internal standard represented a crucial step in the development of method to achieve good reproducibility and robustness for the entire analytical protocol, three compounds (2,3,5-trimethacarb, 4-bromo-3,5-dimethylphenyl-n-methylcarbamate (BDMC) and carbaryl-d7) were evaluated as internal standards. Both precision and accuracy of the proposed protocol tested at concentration of 0.08, 5 and 3 μg l⁻¹ offered values ranging from 70.8% and 115.7% (except for carbaryl at 3 μg l⁻¹) and from 1.0% and 9.0% for accuracy and precision, respectively. Moreover, LOD and LOQ values ranging from 0.04 to 1.7 ng l⁻¹ and from 0.64 to 2.9 ng l⁻¹, respectively, can be considered very satisfactory. Copyright

  15. Rapid determination of methadone and its major metabolite in biological fluids by gas-liquid chromatography with thermionic detection for maintenance treatment of opiate addicts.

    Chikhi-Chorfi, N; Pham-Huy, C; Galons, H; Manuel, N; Lowenstein, W; Warnet, J M; Claude, J R

    1998-11-06

    A rapid gas-liquid chromatographic assay is developed for the quantification of methadone (Mtd) and its major metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), in biological fluids of opiate addicts. After alkaline extraction from samples with lidocaine hydrochloride as internal standard, Mtd and EDDP are separated on SP-2250 column at 220 degrees C and detected with a thermionic detector. The chromatographic time is about 6 min. The relative standard deviations (R.S.D.) of Mtd and EDDP standards are between 1.5 and 5.5%. Most drugs of abuse (morphine, codeine, narcotine, cocaine, benzoylecgonine, cocaethylene, dextropropoxyphene etc) are shown not to interfere with this technique. The method has been applied to study the levels of Mtd and EDDP metabolite in serum, saliva and urine of patients under maintenance treatment for opiate dependence. EDDP levels were found higher than those of Mtd in urine samples from four treated patients, but lower in serum and undetectable in saliva. However, Mtd concentrations were higher in saliva than in serum.

  16. A modified commercial gas chromatograph for the continuous monitoring of the thermal degradation of sunflower oil and off-line solid phase extraction gas-chromatography-mass spectrometry characterization of released volatiles.

    Ontañon, I; Sanz, J; Escudero, A; de Marcos, S; Ferreira, V; Galbán, J

    2015-04-03

    A homemade flow cell attached to a commercial Gas Chromatograph equipped with a Flame Ionization Detector (FID) has been designed for the continuous monitoring of volatile compounds released during heating edible oils. Analytical parameters such as mass of sample, temperature and flow rates have been optimized and the obtained results have been compared with the corresponding thermographs from standard TG systems. Results show that under optimum conditions, the profiles of volatiles released upon heating are comparable to the profiles of TG curves, suggesting that the FID based system could be an alternative to TGA. Additionally, volatiles have been retained in a Lichrolut EN(®) resin, eluted and analyzed by Gas Chromatography-Mass Spectrometry. In this case, forty five compounds have been identified (acids, alcohols, alkanes, aldehydes, ketones and furans) and compared with the FID signals, working both in air or nitrogen atmosphere. It has been concluded that the oxidative thermal degradation is prevented in the presence of a nitrogen atmosphere. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Rapid vertical trace gas transport by an isolated midlatitude thunderstorm

    Hauf, Thomas; Schulte, Peter; Alheit, Reiner; Schlager, Hans

    1995-11-01

    During the cloud dynamics and chemistry field experiment CLEOPATRA in the summer of 1992 in southern Germany, the Deutsche Forschungsanstalt für Luft- und Raumfahrt (DLR) (German Aerospace Research Establishment) research aircraft Falcon traversed four times the anvil of a severe, isolated thunderstorm. The first two traverses were at 8 km altitude and close to the anvil cloud base, while the second two traverses were at 10 km. During the 8-km traverse, measured ozone mixing ratios dropped by 13 parts per billion by volume (ppbv) from the ambient cloud free environment to the anvil cloud, while water vapor increased by 0.3 g kg-1. At the 10-km traverses, ozone dropped by 25 ppbv, while water vapor increased by 0.18 g kg-1. Three-dimensional numerical thunderstorm simulations were performed to understand the cause of these changes. The simulations included the transport of two chemical inert tracers. Ozone was assumed to be one of them. The initial ozone profile was composed from an ozone routine sounding and the in situ Falcon measurements prior to the thunderstorm development. The second tracer is typical for a surface released pollutant with a nonzero, constant value in the boundary layer but zero above it. The redistribution of both tracers by the storm is calculated and compared with the observations. For the anvil penetration at 10 km, the calculated difference in ozone mixing ratios is 21 ppbv, while for water vapor an increase of 0.25 g kg-1 was found, in good agreement with the observations. To validate the model results, the radar reflectivity was calculated from simulated fields of cloud water, rain, graupel, hail, and snow and ice crystals and compared with observed values. With respect to maximum reflectivity values and spatial scales, again, excellent agreement was achieved. It is concluded that the rapid transport from the boundary layer directly into the anvil level is the most likely cause of the observed ozone decrease and water vapor increase

  18. Improved Chromatographic Bioavailability Estimations

    Dorsey, John

    1996-01-01

    .... Since the inception of reversed phase liquid chromatography there have been many attempts to correlate chromatographic retention with bioavailability and the most often used bulk measure, the octanol...

  19. Determination of the analytical performance of a headspace capillary gas chromatographic technique and karl Fischer coulometric titration by system calibration using oil samples containing known amounts of moisture.

    Jalbert, J; Gilbert, R; Tétreault, P

    1999-08-01

    Over the past few years, concerns have been raised in the literature about the accuracy of the Karl Fischer (KF) method for assessing moisture in transformer mineral oils. To better understand this issue, the performance of a static headspace capillary gas chromatographic (HS-CGC) technique was compared to that of KF coulometric titration by analyzing moisture in samples containing known amounts of water and various samples obtained from the National Institute of Standards and Technology (NIST). Two modes of adding samples into the KF vessel were used:  direct injection and indirect injection via an azeotropic distillation of the moisture with toluene. Under the conditions used for direct injection, the oil matrix was totally dissolved in the anolyte, which allowed the moisture to be titrated in a single-phase solution rather than in a suspension. The results have shown that when HS-CGC and combined azeotropic distillation/KF titration are calibrated with moisture-in-oil standards, a linear relation is observed over 0-60 ppm H(2)O with a correlation coefficient better than 0.9994 (95% confidence), with the regression line crossing through zero. A similar relation can also be observed when calibration is achieved by direct KF addition of standards prepared with octanol-1, but in this case an intercept of 4-5 ppm is noted. The amount of moisture determined by curve interpolation in NIST reference materials by the three calibrated systems ranges from 13.0 to 14.8 ppm for RM 8506 and 42.5 to 46.4 ppm for RM 8507, and in any case, the results were as high as those reported in the literature with volumetric KF titration. However, titration of various dehydrated oil and solvent samples showed that direct KF titration is affected by a small bias when samples contain very little moisture. The source of error after correction for the large sample volume used for the determination (8 mL) is about 6 ppm for Voltesso naphthenic oil and 4 ppm for toluene, revealing a matrix

  20. Application of a 1,1,3,3-tetramethylguanidine (TMG)/MeOH-CO2 in situ derivatization procedure for the gas chromatographic characterization of the fatty acid profile in olive oil.

    Saliu, F; Anzano, M; Franzetti, A

    2015-03-01

    1,1,3,3-Tetramethylguanidine (TMG), methanol and carbon dioxide were investigated as switchable polarity solvents (SPS) in the simultaneous derivatization and extraction of triacylglycerols for the gas chromatographic (GC) characterization of olive oil. Three commercial olive oils were used as test samples. Results of the developed method did not differ statistically from those provided by reference derivatization procedures. The transesterification reaction was carried out under a very mild condition, one step and in situ, and no particular matrix interferences were evidenced. The method represented the first example of the use of a switchable polarity mixture for the preparation of methyl ester derivatives of fatty acids (FAME).

  1. An assessment of the usefulness of a rapid immuno-chromatographic test, "Determine™ malaria pf" in evaluation of intervention measures in forest villages of central India

    Shukla Manmohan

    2001-08-01

    Full Text Available Abstract Background Plasmodium falciparum malaria, is a major health problem in forested tribal belt of central India. Rapid and accurate methods are needed for the diagnosis of P. falciparum. We performed a blinded evaluation of the recently introduced Determine™ malaria pf test (Abbott, Laboratories, Japan compared with microscopy and splenomegaly in children in epidemic prone areas of district Mandla to assess the impact of intervention measures. Methods Children aged 2–10 yrs with and without fever were examined for spleen enlargement by medical specialist by establishing a mobile field clinic. From these children thick blood smears were prepared from finger prick and read by a technician. Simultaneously, rapid tests were performed by a field lab attendant. The figures for specificity, sensitivity and predictive values were calculated using microscopy as gold standard. Results In all 349 children were examined. The sensitivity and specificity for Determine rapid diagnostic test were 91 and 80% respectively. The positive predictive values (PPV, negative predictive values (NPV and accuracy of the test were respectively 79, 91 and 85%. On the contrary, the sensitivity and specificity of spleen in detecting malaria infection were 57 and 74 % respectively with PPV of 73%, NPV 59 % and an accuracy of 65%. Conclusions Determine™ malaria rapid diagnostic test is easier and quicker to perform and has other advantages over microscopy in not requiring prior training of personnel or quality control. Thus, highlighting the usefulness of a rapid antigen test in assessing prevailing malaria situation in remote areas.

  2. Ionic liquid-based single-drop microextraction/gas chromatographic/mass spectrometric determination of benzene, toluene, ethylbenzene and xylene isomers in waters.

    Aguilera-Herrador, Eva; Lucena, Rafael; Cárdenas, Soledad; Valcárcel, Miguel

    2008-08-01

    The direct coupling between ionic liquid-based single-drop microextraction and gas chromatography/mass spectrometry is proposed for the rapid and simple determination of benzene, toluene, ethylbenzene and xylenes isomers (BTEX) in water samples. The extraction procedure exploits not only the high affinity of the selected ionic liquid (1-methyl-3-octyl-imidazolium hexaflourophosphate) to these aromatic compounds but also its special properties like viscosity, low vapour pressure and immiscibility with water. All the variables involved in the extraction process have been studied in depth. The developed method allows the determination of these single-ring compounds in water under the reference concentration level fixed by the international legislation. In this case, limits of detection were in the range 20 ng L(-1) (obtained for benzene) and 91 ng L(-1) (for o-xylene). The repeatability of the proposed method, expressed as RSD (n=5), varied between 3.0% (o-xylene) and 5.2% (toluene).

  3. Rapid Immuno-Chromatographic Assay for the Detection of Antibodies to HIV Compare with Elisa among Voluntary and Replacement Blood Donor of Mymensingh Medical College Hospital.

    Chakrabarty, P; Rudra, S; Hossain, M A; Begum, S A; Mirza, T T; Rudra, M

    2015-04-01

    Suitable algorithms based on a combination of two or more simple rapid HIV assays have been shown to have a diagnostic accuracy comparable to double enzyme-linked immunosorbent assay (ELISA) or double ELISA with Western Blot strategies. The aims of this study were to evaluate the performance of five simple rapid HIV assays using whole blood samples from voluntary and replacement blood donors & HIV-infected patients (positive samples from BSMMU, Dhaka). Five rapid HIV assays: Determine™ HIV-1/2 (Inverness Medical), SD Bioline HIV 1/2 3.0 (Standard Diagnostics Inc.), First Response HIV Card 1-2.0 (PMC Medical India Pvt Ltd.), HIV1/2 Stat-Pak Dipstick (Chembio Diagnostic System, Inc) and Uni-Gold™ HIV-1/2 (Biotech) were evaluated between 1st February to 30th June, 2013 using 400 whole blood samples from voluntary and replacement blood donors. All samples that were reactive on all or any of the five rapid assays and 10% of non-reactive samples were tested on a confirmatory Inno-Lia HIV I/II immunoblot assay (Immunogenetics). Only 01 sample including ten positive samples from BSMMU were confirmed HIV-1 antibody positive, while 399 were HIV negative. The sensitivity at initial testing of Determine, SD Bioline and Uni-Gold™ was 100% (95% CI; 99.1-100) while First Response and Stat-Pak had sensitivity of 99.5% (95% CI; 98.2-99.9) and 97.7% (95% CI; 95.7-98.9) respectively, which increased to 100% (95% CI; 99.1-100) on repeat testing. The initial specificity of the Uni-Gold™ assay was 100% (95% CI; 99.6-100) while specificities were 99.6% (95% CI; 99-99.9), 99.4% (95% CI; 98.8-99.7), 99.6% (95% CI; 99-99.9) and 99.8% (95% CI; 99.3-99.9) for Determine, SD Bioline, First Response and Stat-Pak assays, respectively. There was no any sample which was concordantly false positive in Uni-Gold™, Determine and SD Bioline assays. An alternative confirmatory HIV testing strategy based on initial testing on either SD Bioline or Determine assays followed by testing of reactive

  4. Chemically synthesized PbS Nano particulate thin films for a rapid NO2 gas sensor

    Burungale Vishal V.

    2016-03-01

    Full Text Available Rapid NO2 gas sensor has been developed based on PbS nanoparticulate thin films synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR method at different precursor concentrations. The structural and morphological properties were investigated by means of X-ray diffraction and field emission scanning electron microscope. NO2 gas sensing properties of PbS thin films deposited at different concentrations were tested. PbS film with 0.25 M precursor concentration showed the highest sensitivity. In order to optimize the operating temperature, the sensitivity of the sensor to 50 ppm NO2 gas was measured at different operating temperatures, from 50 to 200 °C. The gas sensitivity increased with an increase in operating temperature and achieved the maximum value at 150 °C, followed by a decrease in sensitivity with further increase of the operating temperature. The sensitivity was about 35 % for 50 ppm NO2 at 150 °C with rapid response time of 6 s. T90 and T10 recovery time was 97 s at this gas concentration.

  5. Quantification of rifampicin in human plasma and cerebrospinal fluid by a highly sensitive and rapid liquid chromatographic-tandem mass spectrometric method.

    Srivastava, Abhishek; Waterhouse, David; Ardrey, Alison; Ward, Stephen A

    2012-11-01

    A highly sensitive and rapid liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed to measure the levels of the antitubercular drug rifampicin (RIF) in human plasma and cerebrospinal fluid (CSF). The analyte and internal standard (IS) were isolated from plasma and CSF by a simple organic solvent based precipitation of proteins followed by centrifugation. Detection was carried out by electrospray positive ionization mass spectrometry in the multiple-reaction monitoring (MRM) mode. The assay was linear in the concentration range 25-6400 ng/mL with intra- and inter-day precision of <7% and <8%, respectively. The validated method was applied to the study of RIF pharmacokinetics in human CSF and plasma over 25 h period after a 10 mg/kg oral dose. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Isotope separations using chromatographic methods

    Leseticky, L.

    1985-01-01

    A survey is given of chromatographic separations of compounds only differing in isotope composition. Isotope effects on physical properties which allow chromatographic separation (vapour tension, adsorption heat, partition coefficient) are very small, with the exception of the simplest molecules. Therefore, separation factors only assume the value of several per cent. From this ensues the necessity of using columns which are specially and very carefully prepared and have a separation efficiency of the order of 10 4 theoretical plates. Briefly discussed is liquid chromatography on ion exchangers which with a varied degree of success was used for separating simple inorganic compounds or ions. Ion exchange chromatography of amino acids labelled with tritium, and chromatography of tritium labelled steroids also provided only a certain degree of separation. A detailed analysis is presented of gas chromatography separation of various deuterium and tritium labelled low-molecular compounds, to which a number of studies has been devoted in the literature. Very promising is the method of complexation gas chromatography based on the reversible formation of a complex of the ligand (the compound being separated) and the compound of the (transition) metal as the steady-state phase. (author)

  7. Method and apparatus for rapid adjustment of process gas inventory in gaseous diffusion cascades

    Dyer, R.H.; Fowler, A.H.; Vanstrum, P.R.

    1977-01-01

    The invention relates to an improved method and system for making relatively large and rapid adjustments in the process gas inventory of an electrically powered gaseous diffusion cascade in order to accommodate scheduled changes in the electrical power available for cascade operation. In the preferred form of the invention, the cascade is readied for a decrease in electrical input by simultaneously withdrawing substreams of the cascade B stream into respective process-gas-freezing and storage zones while decreasing the datum-pressure inputs to the positioning systems for the cascade control valves in proportion to the weight of process gas so removed. Consequently, the control valve positions are substantially unchanged by the reduction in invention, and there is minimal disturbance of the cascade isotopic gradient. The cascade is readied for restoration of the power cut by simultaneously evaporating the solids in the freezing zones to regenerate the process gas substreams and introducing them to the cascade A stream while increasing the aforementioned datum pressure inputs in proportion to the weight of process gas so returned. In the preferred form of the system for accomplishing these operations, heat exchangers are provided for freezing, storing, and evaporating the various substreams. Preferably, the heat exchangers are connected to use existing cascade auxiliary systems as a heat sink. A common control is employed to adjust and coordinate the necessary process gas transfers and datum pressure adjustments

  8. Rapid identification and quantification of methamphetamine and amphetamine in hair by gas chromatography/mass spectrometry coupled with micropulverized extraction, aqueous acetylation and microextraction by packed sorbent.

    Miyaguchi, Hajime; Iwata, Yuko T; Kanamori, Tatsuyuki; Tsujikawa, Kenji; Kuwayama, Kenji; Inoue, Hiroyuki

    2009-05-01

    We developed a rapid identification and quantification method for the toxicological analysis of methamphetamine and amphetamine in human hair by gas chromatography/mass spectrometry coupled with a novel combination of micropulverized extraction, aqueous acetylation and microextraction by packed sorbent (MEPS) named MiAMi-GC/MS. A washed hair sample (1-5 mg) was micropulverized for 5 min in a 2 mL plastic tube with 250 microL of water. An anion-exchange sorbent was added to adsorb anionic interferences. After removing the residue with a membrane-filter unit, sodium carbonate and acetic anhydride was admixed in turn. Acetylation was completed in approximately 20 min at room temperature. The acetylated analytes in the reaction liquid were concentrated to an octadecylsilica sorbent packed in the needle of a syringe by a CombiPAL autosampler. Elution was carried out with 50 microL of methanol, and the entire eluate injected into a gas chromatograph using a programmable temperature vaporizing (PTV) technique. The time required for sample preparation and GC/MS analysis was approximately 1 h from a washed hair sample, and an evaporation process was not required. Ranges for quantification were 0.20-50 (ng/mg) each for methamphetamine and amphetamine using 1 mg of hair. Accuracy and relative standard deviation (RSD) were evaluated intraday and interday at three concentrations, and the results were within the limit of a guidance issued by U.S. Food and Drug Administration. For identification, full-scan mass spectra of methamphetamine and amphetamine were obtained using 5 mg of fortified hair samples at 0.2 ng/mg. The extraction device of MEPS was durable for at least 300 extractions, whereas the liner of the gas chromatograph should be replaced after 20-30 times use. The carry over was estimated to be about 1-2%. This sample-preparation method coupled with GC/MS is fast and labor-saving in comparison with conventional methods.

  9. Simple setup for gas-phase H/D exchange mass spectrometry coupled to electron transfer dissociation and ion mobility for analysis of polypeptide structure on a liquid chromatographic time scale.

    Mistarz, Ulrik H; Brown, Jeffery M; Haselmann, Kim F; Rand, Kasper D

    2014-12-02

    Gas-phase hydrogen/deuterium exchange (HDX) is a fast and sensitive, yet unharnessed analytical approach for providing information on the structural properties of biomolecules, in a complementary manner to mass analysis. Here, we describe a simple setup for ND3-mediated millisecond gas-phase HDX inside a mass spectrometer immediately after ESI (gas-phase HDX-MS) and show utility for studying the primary and higher-order structure of peptides and proteins. HDX was achieved by passing N2-gas through a container filled with aqueous deuterated ammonia reagent (ND3/D2O) and admitting the saturated gas immediately upstream or downstream of the primary skimmer cone. The approach was implemented on three commercially available mass spectrometers and required no or minor fully reversible reconfiguration of gas-inlets of the ion source. Results from gas-phase HDX-MS of peptides using the aqueous ND3/D2O as HDX reagent indicate that labeling is facilitated exclusively through gaseous ND3, yielding similar results to the infusion of purified ND3-gas, while circumventing the complications associated with the use of hazardous purified gases. Comparison of the solution-phase- and gas-phase deuterium uptake of Leu-Enkephalin and Glu-Fibrinopeptide B, confirmed that this gas-phase HDX-MS approach allows for labeling of sites (heteroatom-bound non-amide hydrogens located on side-chains, N-terminus and C-terminus) not accessed by classical solution-phase HDX-MS. The simple setup is compatible with liquid chromatography and a chip-based automated nanoESI interface, allowing for online gas-phase HDX-MS analysis of peptides and proteins separated on a liquid chromatographic time scale at increased throughput. Furthermore, online gas-phase HDX-MS could be performed in tandem with ion mobility separation or electron transfer dissociation, thus enabling multiple orthogonal analyses of the structural properties of peptides and proteins in a single automated LC-MS workflow.

  10. A hybrid thermal video and FTIR spectrometer system for rapidly locating and characterizing gas leaks

    Williams, David J.; Wadsworth, Winthrop; Salvaggio, Carl; Messinger, David W.

    2006-08-01

    Undiscovered gas leaks, known as fugitive emissions, in chemical plants and refinery operations can impact regional air quality and present a loss of product for industry. Surveying a facility for potential gas leaks can be a daunting task. Industrial leak detection and repair programs can be expensive to administer. An efficient, accurate and cost effective method for detecting and quantifying gas leaks would both save industries money by identifying production losses and improve regional air quality. Specialized thermal video systems have proven effective in rapidly locating gas leaks. These systems, however, do not have the spectral resolution for compound identification. Passive FTIR spectrometers can be used for gas compound identification, but using these systems for facility surveys is problematic due to their small field of view. A hybrid approach has been developed that utilizes the thermal video system to locate gas plumes using real time visualization of the leaks, coupled with the high spectral resolution FTIR spectrometer for compound identification and quantification. The prototype hybrid video/spectrometer system uses a sterling cooled thermal camera, operating in the MWIR (3-5 μm) with an additional notch filter set at around 3.4 μm, which allows for the visualization of gas compounds that absorb in this narrow spectral range, such as alkane hydrocarbons. This camera is positioned alongside of a portable, high speed passive FTIR spectrometer, which has a spectral range of 2 - 25 μm and operates at 4 cm -1 resolution. This system uses a 10 cm telescope foreoptic with an onboard blackbody for calibration. The two units are optically aligned using a turning mirror on the spectrometer's telescope with the video camera's output.

  11. Chromatographic hydrogen isotope separation

    Aldridge, F.T.

    1983-01-01

    Intermetallic compounds with the CaCu5 type of crystal structure, particularly LaNiCo and CaNi5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation column. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale multi-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors

  12. Chromatographic hydrogen isotope separation

    Aldridge, F.T.

    1981-01-01

    Intermetallic compounds with the CaCu5 type of crystal structure , particularly LaNiCo and CaNi5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation colum. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale mutli-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors

  13. Headspace solid-phase microextraction-gas chromatographic-time-of-flight mass spectrometric methodology for geographical origin verification of coffee

    Risticevic, Sanja; Carasek, Eduardo; Pawliszyn, Janusz

    2008-01-01

    Increasing consumer awareness of food safety issues requires the development of highly sophisticated techniques for the authentication of food commodities. The food products targeted for falsification are either products of high commercial value or those produced in large quantities. For this reason, the present investigation is directed towards the characterization of coffee samples according to the geographical origin. The conducted research involves the development of a rapid headspace solid-phase microextraction (HS-SPME)-gas chromatography-time-of-flight mass spectrometry (GC-TOFMS) method that is utilized for the verification of geographical origin traceability of coffee samples. As opposed to the utilization of traditional univariate optimization methods, the current study employs the application of multivariate experimental designs to the optimization of extraction-influencing parameters. Hence, the two-level full factorial first-order design aided in the identification of two influential variables: extraction time and sample temperature. The optimum set of conditions for the two variables was 12 min and 55 deg. C, respectively, as directed by utilization of Doehlert matrix and response surface methodology. The high-throughput automated SPME procedure was completed by implementing a single divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) 50/30 μm metal fiber with excellent durability properties ensuring the completion of overall sequence of coffee samples. The utilization of high-speed TOFMS instrument ensured the completion of one GC-MS run of a complex coffee sample in 7.9 min and the complete list of benefits provided by ChromaTOF software including fully automated background subtraction, baseline correction, peak find and mass spectral deconvolution algorithms was exploited during the data evaluation procedure. The combination of the retention index (RI) system using C 8 -C 40 alkanes and the mass spectral library search was utilized for the

  14. Headspace solid-phase microextraction-gas chromatographic-time-of-flight mass spectrometric methodology for geographical origin verification of coffee

    Risticevic, Sanja [Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Carasek, Eduardo [Department of Chemistry, Federal University of Santa Catarina, Trindade, Florianopolis, 88040-900, Santa Catarina (Brazil); Pawliszyn, Janusz [Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada)], E-mail: janusz@uwaterloo.ca

    2008-06-09

    Increasing consumer awareness of food safety issues requires the development of highly sophisticated techniques for the authentication of food commodities. The food products targeted for falsification are either products of high commercial value or those produced in large quantities. For this reason, the present investigation is directed towards the characterization of coffee samples according to the geographical origin. The conducted research involves the development of a rapid headspace solid-phase microextraction (HS-SPME)-gas chromatography-time-of-flight mass spectrometry (GC-TOFMS) method that is utilized for the verification of geographical origin traceability of coffee samples. As opposed to the utilization of traditional univariate optimization methods, the current study employs the application of multivariate experimental designs to the optimization of extraction-influencing parameters. Hence, the two-level full factorial first-order design aided in the identification of two influential variables: extraction time and sample temperature. The optimum set of conditions for the two variables was 12 min and 55 deg. C, respectively, as directed by utilization of Doehlert matrix and response surface methodology. The high-throughput automated SPME procedure was completed by implementing a single divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) 50/30 {mu}m metal fiber with excellent durability properties ensuring the completion of overall sequence of coffee samples. The utilization of high-speed TOFMS instrument ensured the completion of one GC-MS run of a complex coffee sample in 7.9 min and the complete list of benefits provided by ChromaTOF software including fully automated background subtraction, baseline correction, peak find and mass spectral deconvolution algorithms was exploited during the data evaluation procedure. The combination of the retention index (RI) system using C{sub 8}-C{sub 40} alkanes and the mass spectral library search was

  15. Pressure disequilibria induced by rapid valve closure in noble gas extraction lines

    Morgan, Leah; Davidheiser-Kroll, Brett

    2015-01-01

    Pressure disequilibria during rapid valve closures can affect calculated molar quantities for a range of gas abundance measurements (e.g., K-Ar geochronology, (U-Th)/He geochronology, noble gas cosmogenic chronology). Modeling indicates this effect in a system with a 10 L reservoir reaches a bias of 1% before 1000 pipette aliquants have been removed from the system, and a bias of 10% before 10,000 aliquants. Herein we explore the causes and effects of this problem, which is the result of volume changes during valve closure. We also present a solution in the form of an electropneumatic pressure regulator that can precisely control valve motion. This solution reduces the effect to ∼0.3% even after 10,000 aliquants have been removed from a 10 L reservoir.

  16. Pressure disequilibria induced by rapid valve closure in noble gas extraction lines

    Morgan, Leah E.; Davidheiser-Kroll, Brett

    2015-06-01

    Pressure disequilibria during rapid valve closures can affect calculated molar quantities for a range of gas abundance measurements (e.g., K-Ar geochronology, (U-Th)/He geochronology, noble gas cosmogenic chronology). Modeling indicates this effect in a system with a 10 L reservoir reaches a bias of 1% before 1000 pipette aliquants have been removed from the system, and a bias of 10% before 10,000 aliquants. Herein we explore the causes and effects of this problem, which is the result of volume changes during valve closure. We also present a solution in the form of an electropneumatic pressure regulator that can precisely control valve motion. This solution reduces the effect to ˜0.3% even after 10,000 aliquants have been removed from a 10 L reservoir.

  17. Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications

    Ross, Pierre-Simon; White, James D. L.; Zimanowski, Bernd; Büttner, Ralf

    2008-10-01

    In diatremes and other volcanic vents, steep bodies of volcaniclastic material having differing properties (particle size distribution, proportion of lithic fragments, etc.) from those of the surrounding vent-filling volcaniclastic material are often found. It has been proposed that cylindrical or cone-shaped bodies result from the passage of “debris jets” generated after phreatomagmatic explosions or other discrete subterranean bursts. To learn more about such phenomena, we model experimentally the injection of gas-particulate dispersions through other particles. Analogue materials (glass beads or sand) and a finite amount of compressed air are used in the laboratory. The gas is made available by rapidly opening a valve—therefore the injection of gas and coloured particles into a granular host is a brief (non-erupting injections produce cylindrical bodies of coloured beads whereas erupting runs produce flaring upward or conical deposits. Changing the particle size of the host glass beads does not have a large effect under the size range investigated (100 200 to 300 400 μm). Doubling the host thickness (injection depth) requires a doubling of the initial gas pressure to produce similar phenomena. Such injections—whether erupting or wholly subterranean—provide a compelling explanation for the origin and characteristics of multiple cross-cutting bodies that have been documented for diatreme and other vent deposits.

  18. Rapid hydrogen gas generation using reactive thermal decomposition of uranium hydride.

    Kanouff, Michael P.; Van Blarigan, Peter; Robinson, David B.; Shugard, Andrew D.; Gharagozloo, Patricia E.; Buffleben, George M.; James, Scott Carlton; Mills, Bernice E.

    2011-09-01

    Oxygen gas injection has been studied as one method for rapidly generating hydrogen gas from a uranium hydride storage system. Small scale reactors, 2.9 g UH{sub 3}, were used to study the process experimentally. Complimentary numerical simulations were used to better characterize and understand the strongly coupled chemical and thermal transport processes controlling hydrogen gas liberation. The results indicate that UH{sub 3} and O{sub 2} are sufficiently reactive to enable a well designed system to release gram quantities of hydrogen in {approx} 2 seconds over a broad temperature range. The major system-design challenge appears to be heat management. In addition to the oxidation tests, H/D isotope exchange experiments were performed. The rate limiting step in the overall gas-to-particle exchange process was found to be hydrogen diffusion in the {approx}0.5 {mu}m hydride particles. The experiments generated a set of high quality experimental data; from which effective intra-particle diffusion coefficients can be inferred.

  19. Rapid validated liquid chromatographic method coupled with ...

    NTB in human plasma, and thus can be applied efficiently for the analysis of clinical samples containing. NTB. Keywords: ... permits the analysis of a lot of clinical samples containing NTB in a ... from Milli-Q plus purification system, Millipore, ... Fifty microliter of CBP working standard solution ... Percentage relative error (%.

  20. [Evaluation of a new blood gas analysis system: RapidPoint 500(®)].

    Nicolas, Thierry; Cabrolier, Nadège; Bardonnet, Karine; Davani, Siamak

    2013-01-01

    We present here evaluation of a new blood gas analysis system, RapidPoint 500(®) (Siemens Healthcare Diagnostics). The aim of this research was to compare the ergonomics and analytical performances of this analyser with those of the RapidLab 1265 for the following parameters: pH, partial oxygen pressure, partial carbon dioxide pressure, sodium, potassium, ionized calcium, lactate and the CO-oximetry parameters: hemoglobin, oxyhemoglobin, carboxyhemoglobin, methemoglobin, reduced hemoglobin, neonatal bilirubin; as well as with the Dimension Vista 500 results for chloride and glucose. The Valtec protocol, recommended by the French Society of Clinical Biology (SFBC), was used to analyze the study results. The experiment was carried out over a period of one month in the Department of medical biochemistry. One hundred sixty five samples from adult patients admitted to the ER or hospitalized in intensive care were tested. The RapidPoint 500(®) was highly satisfactory from an ergonomic point of view. Intra-and inter- assay coefficients of variation (CV) with the three control levels were below those recommended by the SFBC for all parameters, and the comparative study gave coefficients of determination higher than 0.91. Taken together, the RapidPoint 500(®) appears fully satisfactory in terms of ergonomics and analytical performance.

  1. Towards the development of rapid screening techniques for shale gas core properties

    Cave, Mark R.; Vane, Christopher; Kemp, Simon; Harrington, Jon; Cuss, Robert

    2013-04-01

    Shale gas has been produced for many years in the U.S.A. and forms around 8% of total their natural gas production. Recent testing for gas on the Fylde Coast in Lancashire UK suggests there are potentially large reserves which could be exploited. The increasing significance of shale gas has lead to the need for deeper understanding of shale behaviour. There are many factors which govern whether a particular shale will become a shale gas resource and these include: i) Organic matter abundance, type and thermal maturity; ii) Porosity-permeability relationships and pore size distribution; iii) Brittleness and its relationship to mineralogy and rock fabric. Measurements of these properties require sophisticated and time consuming laboratory techniques (Josh et al 2012), whereas rapid screening techniques could provide timely results which could improve the efficiency and cost effectiveness of exploration. In this study, techniques which are portable and provide rapid on-site measurements (X-ray Fluorescence (XRF) and Infra-red (IR) spectroscopy) have been calibrated against standard laboratory techniques (Rock-Eval 6 analyser-Vinci Technologies) and Powder whole-rock XRD analysis was carried out using a PANalytical X'Pert Pro series diffractometer equipped with a cobalt-target tube, X'Celerator detector and operated at 45kV and 40mA, to predict properties of potential shale gas material from core material from the Bowland shale Roosecote, south Cumbria. Preliminary work showed that, amongst various mineralogical and organic matter properties of the core, regression models could be used so that the total organic carbon content could be predicted from the IR spectra with a 95 percentile confidence prediction error of 0.6% organic carbon, the free hydrocarbons could be predicted with a 95 percentile confidence prediction error of 0.6 mgHC/g rock, the bound hydrocarbons could be predicted with a 95 percentile confidence prediction error of 2.4 mgHC/g rock, mica content

  2. Quantification of extra virgin olive oil in dressing and edible oil blends using the representative TMS-4,4'-desmethylsterols gas-chromatographic-normalized fingerprint.

    Pérez-Castaño, Estefanía; Sánchez-Viñas, Mercedes; Gázquez-Evangelista, Domingo; Bagur-González, M Gracia

    2018-01-15

    This paper describes and discusses the application of trimethylsilyl (TMS)-4,4'-desmethylsterols derivatives chromatographic fingerprints (obtained from an off-line HPLC-GC-FID system) for the quantification of extra virgin olive oil in commercial vinaigrettes, dressing salad and in-house reference materials (i-HRM) using two different Partial Least Square-Regression (PLS-R) multivariate quantification methods. Different data pre-processing strategies were carried out being the whole one: (i) internal normalization; (ii) sampling based on The Nyquist Theorem; (iii) internal correlation optimized shifting, icoshift; (iv) baseline correction (v) mean centering and (vi) selecting zones. The first model corresponds to a matrix of dimensions 'n×911' variables and the second one to a matrix of dimensions 'n×431' variables. It has to be highlighted that the proposed two PLS-R models allow the quantification of extra virgin olive oil in binary blends, foodstuffs, etc., when the provided percentage is greater than 25%. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Chromatographic monitoring procedures in laboratory practice

    Kaplina, E G; Belova, O I; Lasunina, N A

    1976-01-01

    The Moscow Coke and Chemical Works consist of three plants in combination, viz., the coking plant, the synthetic ammonia plant using coke-oven-gas hydrogen and the oxygen plant. The plant requirements include daily analyses not only of the coke-oven gas but also of a rich gas and an ethylene fraction. The analyses are carried out in VTI-2 apparatus. The analytical data are used to calculate the calorific values and densities of the gases. The time requirements are very considerable and the laboratory has long been engaged in developing and introducing chromatographic procedures for the major constituents of coke-oven gas, rich gas and ethylene fraction. The procedure developed for the coke-oven and rich gases uses two parallel columns, one packed with molecular sieves and the other with grade KSM silica gel. Hydrogen was determined with argon as the carrier gas, and all other constituents with helium. The procedure was time-consuming and complicated. An attempt was made to separate the gases in an LKhM-7a chromatograph with a programme-controlled 50 to 250/sup 0/C heating cycle, but the procedure still had a number of serious defects and could not be recommended for regular quality control. The final variant involved two parallel columns and a procedure based on that in GOST 14920 (''Dry gas. Proximate analysis''). The chromatograph was a type KhL-69 with a 6-way cock in the gas line so that each of the columns could be brought on stream in succession. The analytical column packings were zeolite (in a 2 m column) and diatomaceous brick with 25% n-hexadecane (in a 6 m column).

  4. Rapid fuel switching from coal to natural gas through effective carbon pricing

    Wilson, I. A. Grant; Staffell, Iain

    2018-05-01

    Great Britain's overall carbon emissions fell by 6% in 2016, due to cleaner electricity production. This was not due to a surge in low-carbon nuclear or renewable sources; instead it was the much-overlooked impact of fuel switching from coal to natural gas generation. This Perspective considers the enabling conditions in Great Britain and the potential for rapid fuel switching in other coal-reliant countries. We find that spare generation and fuel supply-chain capacity must already exist for fuel switching to deliver rapid carbon savings, and to avoid further high-carbon infrastructure lock-in. More important is the political will to alter the marketplace and incentivize this switch, for example, through a stable and strong carbon price. With the right incentives, fuel switching in the power sector could rapidly achieve on the order of 1 GtCO2 saving per year worldwide (3% of global emissions), buying precious time to slow the growth in cumulative carbon emissions.

  5. A study of the adsorption activities of silanol surface structures on a fused silica model substrate by combining 29Si CP MAS NMR and inverse gas chromatographic data

    Scholten, A.B.; Janssen, J.G.M.; Haan, de J.W.; Cramers, C.A.

    1994-01-01

    The possibilities of inverse gas-solid chromatog. (IGC) in obtaining chromatog. data on fumed silica were examd. Aerosil A-200, a fused silica model substrate in 29Si NMR anal., was trimethylsilylated to different degrees. IGC was used to vary reproducibly det. the free specific energies of

  6. Gas Chromatographic-Ion Trap Mass Spectrometric Analysis of Volatile Organic Compounds by Ion-Molecule Reactions Using the Electron-Deficient Reagent Ion CCl{3/+}

    Wang, Cheng-Zhong; Su, Yue; Wang, Hao-Yang; Guo, Yin-Long

    2011-10-01

    When using tetrachloromethane as the reagent gas in gas chromatography-ion trap mass spectrometry equipped with hybrid ionization source, the cation CCl{3/+} was generated in high abundance and further gas-phase experiments showed that such an electron-deficient reagent ion CCl{3/+} could undergo interesting ion-molecule reactions with various volatile organic compounds, which not only present some informative gas-phase reactions, but also facilitate qualitative analysis of diverse volatile compounds by providing unique mass spectral data that are characteristic of particular chemical structures. The ion-molecule reactions of the reagent ion CCl{3/+} with different types of compounds were studied, and results showed that such reactions could give rise to structurally diagnostic ions, such as [M + CCl3 - HCl]+ for aromatic hydrocarbons, [M - OH]+ for saturated cyclic ether, ketone, and alcoholic compounds, [M - H]+ ion for monoterpenes, M·+ for sesquiterpenes, [M - CH3CO]+ for esters, as well as the further fragment ions. The mechanisms of ion-molecule reactions of aromatic hydrocarbons, aliphatic ketones and alcoholic compounds with the reagent ion CCl{3/+} were investigated and proposed according to the information provided by MS/MS experiments and theoretical calculations. Then, this method was applied to study volatile organic compounds in Dendranthema indicum var. aromaticum and 20 compounds, including monoterpenes and their oxygen-containing derivatives, aromatic hydrocarbon and sesquiterpenes were identified using such ion-molecule reactions. This study offers a perspective and an alternative tool for the analysis and identification of various volatile compounds.

  7. At-line gas chromatographic-mass spectrometric analysis of fatty acid profiles of green microalgae using a direct thermal desorption interface

    Blokker, P.; Pel, R.; Akoto, L.; Udo, A.; Brinkman, U.A.Th.; Vreuls, R.J.J.

    2002-01-01

    Thermally assisted hydrolysis and methylation¯gas chromatography (THM¯GC) is an important tool to analyse fatty acid in complex matrices. Since THM¯GC has major drawbacks such as isomerisation when applied to fatty acids in natural matrices, a direct thermal desorption (DTD) interface and an

  8. Analysis and chromatographic purification of eicosanoids multiply labeled by tritium

    Shevchenko, V.P.; Nagaev, I.Yu.; Myasoedov, N.F.

    1989-01-01

    We show the possibility of analysis and chromatographic purification of eicosanoids triply labeled by tritium. The described methods allow us to isolate chromatographically pure products obtained by selective hydrogenatin, chemical, and enzyme methods, with radiochemical purity at least 95-97%. The following methods are used to analyze the reaction mixtures and to isolate the tritium-labeled eicosanoids: gas-liquid chromatography, high-efficiency liquid chromatography, and thin-layer chromatography on supports impregnated with silver nitrate

  9. The effects of curvature on the flow field in rapidly rotating gas centrifuges

    Wood, H.G.; Jordan, J.A.

    1984-01-01

    The effects of curvature on the fluid dynamics of rapidly rotating gas centrifuges are studied. A governing system of a linear partial differential equation and boundary conditions is derived based on a linearization of the equations for viscous compressible flow. This system reduces to the Onsager pancake model if the effects of curvature are neglected. Approximations to the solutions of the governing equations with and without curvature terms are obtained via a finite-element method. Two examples are considered: first where the flow is driven by a thermal gradient at the wall of the centrifuge, and then for the flow being driven by the introduction and removal of mass through the ends of the centrifuge. Comparisons of the results obtained show that, especially for the second example, the inclusion of the terms due to curvature in the model can have an appreciable effect on the solution. (author)

  10. Developing a Natural Gas-Powered Bus Rapid Transit Service: A Case Study

    Mitchell, G.

    2015-11-03

    The Roaring Fork Transit Authority (RFTA) and its VelociRFTA Bus Rapid Transit (BRT) program are unique in many ways. For example, VelociRFTA was the first rural BRT system in the United States and the operational environment of the VelociRFTA BRT is one of the most severe in the country, with extreme winter temperatures and altitudes close to 8,000 feet. RFTA viewed high altitude operation as the most challenging characteristic when it began considering the use of natural gas. RFTA is the second-largest public transit system in Colorado behind Denver's Regional Transportation District (RTD), and it is one of the largest rural public transit systems in the country. In 2013, RFTA accepted delivery of 22 new compressed natural gas (CNG) buses that went into service after completion of maintenance and refueling facilities earlier that year. This paper examines the lessons learned from RFTA's experience of investigating--and ultimately choosing--CNG for their new BRT program and focuses on the unique environment of RFTA's BRT application; the decision process to include CNG fueling in the project; unforeseen difficulties encountered in the operation of CNG buses; public perception; cost comparison to competing fuels; and considerations for indoor fueling facilities and project funding.

  11. Developing a Natural Gas-Powered Bus Rapid Transit Service. A Case Study

    Mitchell, George [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-11-01

    The Roaring Fork Transit Authority (RFTA) and its VelociRFTA Bus Rapid Transit (BRT) program are unique in many ways. For example, VelociRFTA was the first rural BRT system in the United States and the operational environment of the VelociRFTA BRT is one of the most severe in the country, with extreme winter temperatures and altitudes close to 8,000 feet. RFTA viewed high altitude operation as the most challenging characteristic when it began considering the use of natural gas. RFTA is the second-largest public transit system in Colorado behind Denver's Regional Transportation District (RTD), and it is one of the largest rural public transit systems in the country. In 2013, RFTA accepted delivery of 22 new compressed natural gas (CNG) buses that went into service after completion of maintenance and refueling facilities earlier that year. This paper examines the lessons learned from RFTA's experience of investigating--and ultimately choosing--CNG for their new BRT program and focuses on the unique environment of RFTA's BRT application; the decision process to include CNG fueling in the project; unforeseen difficulties encountered in the operation of CNG buses; public perception; cost comparison to competing fuels; and considerations for indoor fueling facilities and project funding.

  12. Use of a hand-portable gas chromatograph-toroidal ion trap mass spectrometer for self-chemical ionization identification of degradation products related to O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate (VX)

    Smith, Philip A., E-mail: Smith.Philip.A@dol.gov [Uniformed Services University of the Health Sciences, Department of Preventive Medicine and Biometrics, 4301 Jones Bridge Road, Bethesda, MD, 20814 (United States); Lepage, Carmela R. Jackson [Defence R and D Canada - Suffield, Box 400, Station Main, Medicine Hat, Alberta, T1A 8K6 (Canada); Savage, Paul B. [Brigham Young University, Department of Chemistry and Biochemistry, Provo, UT, 84602 (United States); Bowerbank, Christopher R.; Lee, Edgar D. [Torion Technologies Inc., 796 East Utah Valley Drive, Suite 200, American Fork, UT, 84003 (United States); Lukacs, Michael J. [Defence R and D Canada - Suffield, Box 400, Station Main, Medicine Hat, Alberta, T1A 8K6 (Canada)

    2011-04-01

    The chemical warfare agent O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate (VX) and many related degradation products produce poorly diagnostic electron ionization (EI) mass spectra by transmission quadrupole mass spectrometry. Thus, chemical ionization (CI) is often used for these analytes. In this work, pseudomolecular ([M+H]{sup +}) ion formation from self-chemical ionization (self-CI) was examined for four VX degradation products containing the diisopropylamine functional group. A person-portable toroidal ion trap mass spectrometer with a gas chromatographic inlet was used with EI, and both fixed-duration and feedback-controlled ionization time. With feedback-controlled ionization, ion cooling (reaction) times and ion formation target values were varied. Evidence for protonation of analytes was observed under all conditions, except for the largest analyte, bis(diisopropylaminoethyl)disulfide which yielded [M+H]{sup +} ions only with increased fixed ionization or ion cooling times. Analysis of triethylamine-d{sub 15} provided evidence that [M+H]{sup +} production was likely due to self-CI. Analysis of a degraded VX sample where lengthened ion storage and feedback-controlled ionization time were used resulted in detection of [M+H]{sup +} ions for VX and several relevant degradation products. Dimer ions were also observed for two phosphonate compounds detected in this sample.

  13. Use of a hand-portable gas chromatograph-toroidal ion trap mass spectrometer for self-chemical ionization identification of degradation products related to O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate (VX)

    Smith, Philip A.; Lepage, Carmela R. Jackson; Savage, Paul B.; Bowerbank, Christopher R.; Lee, Edgar D.; Lukacs, Michael J.

    2011-01-01

    The chemical warfare agent O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate (VX) and many related degradation products produce poorly diagnostic electron ionization (EI) mass spectra by transmission quadrupole mass spectrometry. Thus, chemical ionization (CI) is often used for these analytes. In this work, pseudomolecular ([M+H] + ) ion formation from self-chemical ionization (self-CI) was examined for four VX degradation products containing the diisopropylamine functional group. A person-portable toroidal ion trap mass spectrometer with a gas chromatographic inlet was used with EI, and both fixed-duration and feedback-controlled ionization time. With feedback-controlled ionization, ion cooling (reaction) times and ion formation target values were varied. Evidence for protonation of analytes was observed under all conditions, except for the largest analyte, bis(diisopropylaminoethyl)disulfide which yielded [M+H] + ions only with increased fixed ionization or ion cooling times. Analysis of triethylamine-d 15 provided evidence that [M+H] + production was likely due to self-CI. Analysis of a degraded VX sample where lengthened ion storage and feedback-controlled ionization time were used resulted in detection of [M+H] + ions for VX and several relevant degradation products. Dimer ions were also observed for two phosphonate compounds detected in this sample.

  14. Analytical Method Development and Validation for the Quantification of Acetone and Isopropyl Alcohol in the Tartaric Acid Base Pellets of Dipyridamole Modified Release Capsules by Using Headspace Gas Chromatographic Technique

    Sriram Valavala

    2018-01-01

    Full Text Available A simple, sensitive, accurate, robust headspace gas chromatographic method was developed for the quantitative determination of acetone and isopropyl alcohol in tartaric acid-based pellets of dipyridamole modified release capsules. The residual solvents acetone and isopropyl alcohol were used in the manufacturing process of the tartaric acid-based pellets of dipyridamole modified release capsules by considering the solubility of the dipyridamole and excipients in the different manufacturing stages. The method was developed and optimized by using fused silica DB-624 (30 m × 0.32 mm × 1.8 µm column with the flame ionization detector. The method validation was carried out with regard to the guidelines for validation of analytical procedures Q2 demanded by the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH. All the validation characteristics were meeting the acceptance criteria. Hence, the developed and validated method can be applied for the intended routine analysis.

  15. A Sensitive Method Approach for Chromatographic Analysis of Gas Streams in Separation Processes Based on Columns Packed with an Adsorbent Material

    I. A. A. C. Esteves

    2016-01-01

    Full Text Available A sensitive method was developed and experimentally validated for the in-line analysis and quantification of gaseous feed and product streams of separation processes under research and development based on column chromatography. The analysis uses a specific mass spectrometry method coupled to engineering processes, such as Pressure Swing Adsorption (PSA and Simulated Moving Bed (SMB, which are examples of popular continuous separation technologies that can be used in applications such as natural gas and biogas purifications or carbon dioxide sequestration. These processes employ column adsorption equilibria on adsorbent materials, thus requiring real-time gas stream composition quantification. For this assay, an internal standard is assumed and a single-point calibration is used in a simple mixture-specific algorithm. The accuracy of the method was found to be between 0.01% and 0.25% (-mol for mixtures of CO2, CH4, and N2, tested as case-studies. This makes the method feasible for streams with quality control levels that can be used as a standard monitoring and analyzing procedure.

  16. A novel multiple headspace extraction gas chromatographic method for measuring the diffusion coefficient of methanol in water and in olive oil.

    Zhang, Chun-Yun; Chai, Xin-Sheng

    2015-03-13

    A novel method for the determination of the diffusion coefficient (D) of methanol in water and olive oil has been developed. Based on multiple headspace extraction gas chromatography (MHE-GC), the methanol released from the liquid sample of interest in a closed sample vial was determined in a stepwise fashion. A theoretical model was derived to establish the relationship between the diffusion coefficient and the GC signals from MHE-GC measurements. The results showed that the present method has an excellent precision (RSDwater and olive oil, when compared with data reported in the literature. The present method is simple and practical and can be a valuable tool for the determination of the diffusion coefficient of volatile analyte(s) into food simulants from food and beverage packaging material, both in research studies and in actual applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Rapid estimation of aquifer salinity structure from oil and gas geophysical logs

    Shimabukuro, D.; Stephens, M.; Ducart, A.; Skinner, S. M.

    2016-12-01

    We describe a workflow for creating aquifer salinity maps using Archie's equation for areas that have geophysical data from oil and gas wells. We apply this method in California, where geophysical logs are available in raster format from the Division of Oil, Gas, and Geothermal Resource (DOGGR) online archive. This method should be applicable to any region where geophysical logs are readily available. Much of the work is controlled by computer code, allowing salinity estimates for new areas to be rapidly generated. For a region of interest, the DOGGR online database is scraped for wells that were logged with multi-tool suites, such as the Platform Express or Triple Combination Logging Tools. Then, well construction metadata, such as measured depth, spud date, and well orientation, is attached. The resultant local database allows a weighted criteria selection of wells that are most likely to have the shallow resistivity, deep resistivity, and density porosity measurements necessary to calculate salinity over the longest depth interval. The algorithm can be adjusted for geophysical log availability for older well fields and density of sampling. Once priority wells are identified, a student researcher team uses Neuralog software to digitize the raster geophysical logs. Total dissolved solid (TDS) concentration is then calculated in clean, wet sand intervals using the resistivity-porosity method, a modified form of Archie's equation. These sand intervals are automatically selected using a combination of spontaneous potential and the difference in shallow resistivity and deep resistivity measurements. Gamma ray logs are not used because arkosic sands common in California make it difficult to distinguish sand and shale. Computer calculation allows easy adjustment of Archie's parameters. The result is a semi-continuous TDS profile for the wells of interest. These profiles are combined and contoured using standard 3-d visualization software to yield preliminary salinity

  18. Gas chromatographic-mass spectrometric analysis of urinary volatile organic metabolites: Optimization of the HS-SPME procedure and sample storage conditions.

    Živković Semren, Tanja; Brčić Karačonji, Irena; Safner, Toni; Brajenović, Nataša; Tariba Lovaković, Blanka; Pizent, Alica

    2018-01-01

    Non-targeted metabolomics research of human volatile urinary metabolome can be used to identify potential biomarkers associated with the changes in metabolism related to various health disorders. To ensure reliable analysis of urinary volatile organic metabolites (VOMs) by gas chromatography-mass spectrometry (GC-MS), parameters affecting the headspace-solid phase microextraction (HS-SPME) procedure have been evaluated and optimized. The influence of incubation and extraction temperatures and times, coating fibre material and salt addition on SPME efficiency was investigated by multivariate optimization methods using reduced factorial and Doehlert matrix designs. The results showed optimum values for temperature to be 60°C, extraction time 50min, and incubation time 35min. The proposed conditions were applied to investigate urine samples' stability regarding different storage conditions and freeze-thaw processes. The sum of peak areas of urine samples stored at 4°C, -20°C, and -80°C up to six months showed a time dependent decrease over time although storage at -80°C resulted in a slight non-significant reduction comparing to the fresh sample. However, due to the volatile nature of the analysed compounds, more than two cycles of freezing/thawing of the sample stored for six months at -80°C should be avoided whenever possible. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Monolithic silica spin column extraction and simultaneous derivatization of amphetamines and 3,4-methylenedioxyamphetamines in human urine for gas chromatographic-mass spectrometric detection

    Nakamoto, Akihiro; Nishida, Manami; Saito, Takeshi; Kishiyama, Izumi; Miyazaki, Shota; Murakami, Katsunori; Nagao, Masataka; Namura, Akira

    2010-01-01

    A simple, sensitive, and specific method with gas chromatography-mass spectrometry was developed for simultaneous extraction and derivatization of amphetamines (APs) and 3,4-methylenedioxyamphetamines (MDAs) in human urine by using a monolithic silica spin column. All the procedures, such as sample loading, washing, and elution were performed by centrifugation. APs and MDAs in urine were adsorbed on the monolithic silica and derivatized with propyl chloroformate in the column. Methamphetamine-d 5 was used as an internal standard. The linear ranges were 0.01-5.0 μg mL -1 for methamphetamine (MA) and 3,4-methylenedioxymethamphetamine (MDMA) and 0.02-5.0 μg mL -1 for amphetamine (AP) and 3,4-methylenedioxyamphetamine (MDA) (coefficient of correlation ≥0.995). The recovery of APs and MDAs in urine was 84-94%, and the relative standard deviation of the intra- and interday reproducibility for urine samples containing 0.1, 1.0, and 4.0 μg mL -1 of APs and MDAs ranged from 1.4% to 13.6%. The lowest detection limit (signal-to-noise ratio ≥ 3) in urine was 5 ng mL -1 for MA and MDMA and 10 ng mL -1 for AP and MDA. The proposed method can be used to perform simultaneous extraction and derivatization on spin columns that have been loaded with a small quantity of solvent by using centrifugation.

  20. Performance evaluation of a thermal desorption/gas chromatographic/mass spectrometric method for the characterization of waste tank headspace samples

    Ma, C.Y.; Skeen, J.T.; Dindal, A.B.; Bayne, C.K.; Jenkins, R.A.

    1997-01-01

    A thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) method was validated for the determination of volatile organic compounds collected on carbonaceous triple sorbent traps and applied to characterize samples of headspace gases collected from underground nuclear waste storage tanks at the U.S. Department of Energy's Hanford site, in Richland, WA. Method validation used vapor-phase standards generated from 25 target analytes, including alkanes, alkyl alcohols, alkyl ketones, alkylated aromatics, and alkyl nitriles. The target analytes represent a group of compounds identified in one of the most problematic tanks. TD/GC/MS was carried out with modified injectors. Performance was characterized based on desorption efficiency, reproducibility, stability, and linearity of the calibration, method detection limits, preanalytical holding time, and quality control limits for surrogate standard recoveries. Desorption efficiencies were all greater than 82%, and the majority of the analytes (23 out of 25) had reproducibility values less than 24% near the method detection levels. The method was applied to the analysis of a total of 305 samples collected from the headspaces of 48 underground waste storge tanks. Quality control procedures were implemented to monitor sampling and TD/GC/MS method. 33 refs., 2 figs., 4 tabs

  1. Microphotonic sensors for the rapid detection of the presence of explosive gas mixtures

    McNesby, Kevin L.; Miziolek, Andrzej W.

    2002-02-01

    A first generation, microphotonic sensor for rapid (10 ms response time) measurement of vapors from the hydrocarbon-based fuels JP-8, DF-2, and gasoline has been developed at the U.S. Army Research Laboratory. This sensor is based upon a previously reported laser mixing technique that uses two tunable diode lasers emitting in the near-infrared spectral region to measure concentrations of gases having unstructured absorption spectra. The fiber-mixed laser beam consists of two wavelengths, one of which is absorbed by the fuel vapor, and one of which is not absorbed. By sinusoidally modulating the power of the two lasers at the same frequency but 180 degrees out of phase, a sinusoidal signal is generated at the detector (when the target gas is present in the line of sight). The signal amplitude, measured using standard phase sensitive detection techniques, is proportional to fuel vapor concentration. A second generation sensor, designed to measure the full envelope of the first overtone C-H vibrations in middle distillate fuels is currently being developed. Both sensors are described. Limits of detection using the first generation sensor are reported for vapors of the three fuels studied.

  2. Monolithic silica spin column extraction and simultaneous derivatization of amphetamines and 3,4-methylenedioxyamphetamines in human urine for gas chromatographic-mass spectrometric detection

    Nakamoto, Akihiro [Scientific Investigation Laboratory, Hiroshima Prefectural Police Headquarters, Kohnan 2-26-3, Naka-ku, Hiroshima 730-0825 (Japan); Nishida, Manami [Hiroshima University Technical Center, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551 (Japan); Saito, Takeshi [Department of Emergency and Critical Care Medicine, Tokai University School of Medicine, Shimokasuya 143, Isehara, Kanagawa 259-1143 (Japan); Kishiyama, Izumi; Miyazaki, Shota [GL Sciences Inc., Sayamagahara 237-2, Iruma, Saitama 358-0032 (Japan); Murakami, Katsunori [Scientific Investigation Laboratory, Hiroshima Prefectural Police Headquarters, Kohnan 2-26-3, Naka-ku, Hiroshima 730-0825 (Japan); Nagao, Masataka [Department of Forensic Medicine, Graduate School of Biomedical Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551 (Japan); Namura, Akira, E-mail: namera@hiroshima-u.ac.jp [Department of Forensic Medicine, Graduate School of Biomedical Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551 (Japan)

    2010-02-19

    A simple, sensitive, and specific method with gas chromatography-mass spectrometry was developed for simultaneous extraction and derivatization of amphetamines (APs) and 3,4-methylenedioxyamphetamines (MDAs) in human urine by using a monolithic silica spin column. All the procedures, such as sample loading, washing, and elution were performed by centrifugation. APs and MDAs in urine were adsorbed on the monolithic silica and derivatized with propyl chloroformate in the column. Methamphetamine-d{sub 5} was used as an internal standard. The linear ranges were 0.01-5.0 {mu}g mL{sup -1} for methamphetamine (MA) and 3,4-methylenedioxymethamphetamine (MDMA) and 0.02-5.0 {mu}g mL{sup -1} for amphetamine (AP) and 3,4-methylenedioxyamphetamine (MDA) (coefficient of correlation {>=}0.995). The recovery of APs and MDAs in urine was 84-94%, and the relative standard deviation of the intra- and interday reproducibility for urine samples containing 0.1, 1.0, and 4.0 {mu}g mL{sup -1} of APs and MDAs ranged from 1.4% to 13.6%. The lowest detection limit (signal-to-noise ratio {>=} 3) in urine was 5 ng mL{sup -1} for MA and MDMA and 10 ng mL{sup -1} for AP and MDA. The proposed method can be used to perform simultaneous extraction and derivatization on spin columns that have been loaded with a small quantity of solvent by using centrifugation.

  3. Gas chromatographic-mass spectrometric investigation of n-alkanes and carboxylic acids in bottom sediments of the northern Caspian Sea

    Kenzhegaliev, Akimgali; Zhumagaliev, Sagat; Kenzhegalieva, Dina; Orazbayev, Batyr

    2018-03-01

    Prior to the start of experimental oil production in the Kashagan field (northern part of the Caspian Sea), n-alkanes and carboxylic acids contained in samples obtained from bottom sediments in the area of artificial island "D" were investigated by gas chromatography-mass spectrometry. Concentrations of 10 n-alkanes (composed of C10-C13, C15-C20) and 11 carboxylic acids (composed of C6-C12, C14-C16) were identified and measured. Concentrations of individual alkanes and carboxylic acids in bottom sediments of the various samples varied between 0.001 ÷ 0.88 μg/g and 0.001 ÷ 1.94 μg/g, respectively. Mass spectra, in particular the M+ molecular ion peak and the most intense peaks of fragment ions, are given. The present study illustrates the stability of molecular ions to electronic ionisation and the main fragment ions to the total ion current and shows that the initial fragmentation of alkanes implies radical cleavage of C2H5 rather than CH3. All aliphatic monocarboxylic acids studied were characterised by McLafferty rearrangement leading to the formation of F4 cation-radical with m/z 60 and F3 cation-radical with m/z 88 in the case of ethylhexanoic acid. The formation of oxonium ions presents another important aspect of acid fragmentation. Using mass numbers of oxonium ions and rearrangement ions allows determination of the substitution character in α- and β- C atoms. The essence of our approach is to estimate the infiltration of hydrocarbon fluids from the enclosing formation into sea water, comprising an analysis of derivatives of organic compounds in bottom sediments. Thus, concentrations of derived organic molecules can serve as a basis for estimates of the depth at which hydrocarbon fluids leak, i.e., to serve as an auxiliary technique in the search for hydrocarbon deposits and to repair well leaks.

  4. Application of acetone acetals as water scavengers and derivatization agents prior to the gas chromatographic analysis of polar residual solvents in aqueous samples.

    van Boxtel, Niels; Wolfs, Kris; Van Schepdael, Ann; Adams, Erwin

    2015-12-18

    The sensitivity of gas chromatography (GC) combined with the full evaporation technique (FET) for the analysis of aqueous samples is limited due to the maximum tolerable sample volume in a headspace vial. Using an acetone acetal as water scavenger prior to FET-GC analysis proved to be a useful and versatile tool for the analysis of high boiling analytes in aqueous samples. 2,2-Dimethoxypropane (DMP) was used in this case resulting in methanol and acetone as reaction products with water. These solvents are relatively volatile and were easily removed by evaporation enabling sample enrichment leading to 10-fold improvement in sensitivity compared to the standard 10μL FET sample volumes for a selection of typical high boiling polar residual solvents in water. This could be improved even further if more sample is used. The method was applied for the determination of residual NMP in an aqueous solution of a cefotaxime analogue and proved to be considerably better than conventional static headspace (sHS) and the standard FET approach. The methodology was also applied to determine trace amounts of ethylene glycol (EG) in aqueous samples like contact lens fluids, where scavenging of the water would avoid laborious extraction prior to derivatization. During this experiment it was revealed that DMP reacts quantitatively with EG to form 2,2-dimethyl-1,3-dioxolane (2,2-DD) under the proposed reaction conditions. The relatively high volatility (bp 93°C) of 2,2-DD makes it possible to perform analysis of EG using the sHS methodology making additional derivatization reactions superfluous. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Monolithic silica spin column extraction and simultaneous derivatization of amphetamines and 3,4-methylenedioxyamphetamines in human urine for gas chromatographic-mass spectrometric detection.

    Nakamoto, Akihiro; Nishida, Manami; Saito, Takeshi; Kishiyama, Izumi; Miyazaki, Shota; Murakami, Katsunori; Nagao, Masataka; Namura, Akira

    2010-02-19

    A simple, sensitive, and specific method with gas chromatography-mass spectrometry was developed for simultaneous extraction and derivatization of amphetamines (APs) and 3,4-methylenedioxyamphetamines (MDAs) in human urine by using a monolithic silica spin column. All the procedures, such as sample loading, washing, and elution were performed by centrifugation. APs and MDAs in urine were adsorbed on the monolithic silica and derivatized with propyl chloroformate in the column. Methamphetamine-d(5) was used as an internal standard. The linear ranges were 0.01-5.0 microg mL(-1) for methamphetamine (MA) and 3,4-methylenedioxymethamphetamine (MDMA) and 0.02-5.0 microg mL(-1) for amphetamine (AP) and 3,4-methylenedioxyamphetamine (MDA) (coefficient of correlation > or = 0.995). The recovery of APs and MDAs in urine was 84-94%, and the relative standard deviation of the intra- and interday reproducibility for urine samples containing 0.1, 1.0, and 4.0 microg mL(-1) of APs and MDAs ranged from 1.4% to 13.6%. The lowest detection limit (signal-to-noise ratio > or = 3) in urine was 5 ng mL(-1) for MA and MDMA and 10 ng mL(-1) for AP and MDA. The proposed method can be used to perform simultaneous extraction and derivatization on spin columns that have been loaded with a small quantity of solvent by using centrifugation. Copyright 2009 Elsevier B.V. All rights reserved.

  6. Rapid and selective detection of acetone using hierarchical ZnO gas sensor for hazardous odor markers application.

    Jia, Qianqian; Ji, Huiming; Zhang, Ying; Chen, Yalu; Sun, Xiaohong; Jin, Zhengguo

    2014-07-15

    Hierarchical nanostructured ZnO dandelion-like spheres were synthesized via solvothermal reaction at 200°C for 4h. The products were pure hexagonal ZnO with large exposure of (002) polar facet. Side-heating gas sensor based on hierarchical ZnO spheres was prepared to evaluate the acetone gas sensing properties. The detection limit to acetone for the ZnO sensor is 0.25ppm. The response (Ra/Rg) toward 100ppm acetone was 33 operated at 230°C and the response time was as short as 3s. The sensor exhibited remarkable acetone selectivity with negligible response toward other hazardous gases and water vapor. The high proportion of electron depletion region and oxygen vacancies contributed to high gas response sensitivity. The hollow and porous structure of dandelion-like ZnO spheres facilitated the diffusion of gas molecules, leading to a rapid response speed. The largely exposed (002) polar facets could adsorb acetone gas molecules easily and efficiently, resulting in a rapid response speed and good selectivity of hierarchical ZnO spheres gas sensor at low operating temperature. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Bubble development and fission gas release during rapid heating of 18 GWd/TeU UO2

    Small, G.J.

    1985-01-01

    Small samples (approximately 50 mg) of UO 2 irradiated to 18 GWd/TeU have been heated rapidly in an out-of-pile furnace. Ramp rates were in the range 10-80 deg. C.s -1 , peak temperatures varied from 1400 deg. C to 2500 deg. C and dwell times from one to fifteen min. The specimens were sealed in small capsules which were subsequently pierced to determine the total amount of fission gas ( 85 Kr) released during each test. Changes in the size and number of gas bubbles on grain boundaries were examined using SEM, TEM, replication and fractography techniques will be employed later. In this paper are reported the first series of gas release results and some metallography. The results are compared with related experiments and some qualitative conclusions are drawn regarding the mechanisms and kinetics of transient fission gas behaviour. (author)

  8. A rapid method for simultaneously determining ethanol and methanol content in wines by full evaporation headspace gas chromatography.

    Zhang, Chun-Yun; Lin, Neng-Biao; Chai, Xin-Sheng; Zhong-Li; Barnes, Donald G

    2015-09-15

    This work reports on a full evaporation headspace gas chromatographic (FE HS-GC) method for simultaneously determining the ethanol (EtOH) and methanol (MeOH) content in wines. A small sample (10μL) was placed in a headspace sample vial, and a near-complete mass transfer of ethanol and methanol from the liquid sample to the vapor phase was obtained within three minutes at a temperature of 105°C, which allowed the measurement of the EtOH and MeOH content in the sample by GC. The results showed excellent precision and accuracy, as shown by the reproducibilities of 1.02% and 2.11% for EtOH and MeOH, respectively, and recoveries that ranged from 96.1% to 104% for both alcohols. The method is efficient, accurate and suitable for the determination of EtOH and MeOH in wine production and quality control. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Method and apparatus for rapid adjustment of process gas inventory in gaseous diffusion cascades

    1980-01-01

    A method is specified for the operation of a gaseous diffusion cascade wherein electrically driven compressors circulate a process gas through a plurality of serially connected gaseous diffusion stages to establish first and second countercurrently flowing cascade streams of process gas, one of the streams being at a relatively low pressure and enriched in a component of the process gas and the other being at a higher pressure and depleted in the same, and wherein automatic control systems maintain the stage process gas pressures by positioning process gas flow control valve openings at values which are functions of the difference between reference-signal inputs to the systems, and signal inputs proportional to the process gas pressures in the gaseous diffusion stages associated with the systems, the cascade process gas inventory being altered, while the cascade is operating, by simultaneously directing into separate process-gas freezing zones a plurality of substreams derived from one of the first and second streams at different points along the lengths thereof to solidify approximately equal weights of process gas in the zone while reducing the reference-signal inputs to maintain the positions of the control valves substantially unchanged despite the removal of process gas inventory via the substreams. (author)

  10. Gas chromatographic analysis of plant sterols

    Phytosterols are well-known for their ability to lower blood cholesterol by competing with absorption of cholesterol from the diet and reabsorption of bile cholesterol. Phytosterols as food ingredients are “Generally Recognized As Safe” (GRAS) by the FDA, and they are increasingly incorporated into ...

  11. Gas chromatographic and mass spectrometric analysis of ...

    Unknown

    Following oral administration three major metabolites of ... It is well established that the stimulating anabolic effect of ... oral application of a single dose of clostebol (dose,. 20 mg) ..... 17â and testosterone production by ovarian follicles of the.

  12. Radioimmunoassay of methaqualone in human urine compared with chromatographic methods

    Mule, S.J.; Kogan, M.; Jukofsky, D.

    1978-01-01

    The 125 I-radioimmunoassay for methaqualone in human urine was evaluated by a comparison with newly modified gas-liquid chromatographic and thin-layer chromatographic methods. The statistically significant sensitivity value for the radioimmunoassay was at 2 μg of methaqualone per liter of urine. The coefficient of variation was 2.88 -+ 0.16% intraassay. There was cross-reactivity only with metabolites of methaqualone, 4'-hydroxymethaqualone being twice as sensitively measured as methaqualone. There was complete agreement between results by radioimmunoassay and by gas-liquid chromatography in 96.7% of the samples analyzed. Only 1.2% of the radioimmunoassay values were false positives, and 2.1% false negatives (phi = 0.8917, P < 0.001). Comparisons between the thin-layer chromatographic data and the gas--liquid chromatographic or radioimmunoassay data showed less agreement because of the 50- to 200-fold higher sensitivity of the latter techniques. Gas--liquid chromatography therefore appears to represent the best reference method for the evaluation of the radioimmunoassay, which appears to be a very sensitive and reliable technique for detecting methaqualone and its metabolites in human urine

  13. Recent rapid increases in the demand for city gas in manufacturing industries and future developments

    Kusano, Shigero

    1992-01-01

    City gas companies in Japan are experiencing an expansion in demand for gas in all manufacturing industries. The reason for this is, first and foremost, external, in that the first and second oil crises and the recent Gulf War have placed the oil market in a state of flux. That is to say, supply and demand in the oil products market is unstable while the stability of city gas, which is the main raw material for LNG, is being highly appraised. Another external reason is related to a subject much in the news recently the world over - the environment. City gas is highly regarded for its minimum environmental impact. Domestic reasons for the expansion include the fact that with the increase in use of city gas in manufacturing industries, the end user is beginning to recognize the various special qualities that city gas possesses. The expansion is also due in part to the unrelenting efforts in sales by the gas producers themselves. This report focuses on the expansion in demand in city gas over the past ten years from the point of view of Tokyo Gas as a producer that has been party to the increased sales of city gas in manufacturing industries for over 10 years giving views on the reasons for the increase. Graphic reports of the actual situation of the industry at meetings such as these are rare and therefore although this is slightly different from the main theme, I would like to proceed with the debate in the hope that this will be beneficial in the expansion of future gas demand in countries all over the world

  14. Determination of solute descriptors by chromatographic methods

    Poole, Colin F.; Atapattu, Sanka N.; Poole, Salwa K.; Bell, Andrea K.

    2009-01-01

    The solvation parameter model is now well established as a useful tool for obtaining quantitative structure-property relationships for chemical, biomedical and environmental processes. The model correlates a free-energy related property of a system to six free-energy derived descriptors describing molecular properties. These molecular descriptors are defined as L (gas-liquid partition coefficient on hexadecane at 298 K), V (McGowan's characteristic volume), E (excess molar refraction), S (dipolarity/polarizability), A (hydrogen-bond acidity), and B (hydrogen-bond basicity). McGowan's characteristic volume is trivially calculated from structure and the excess molar refraction can be calculated for liquids from their refractive index and easily estimated for solids. The remaining four descriptors are derived by experiment using (largely) two-phase partitioning, chromatography, and solubility measurements. In this article, the use of gas chromatography, reversed-phase liquid chromatography, micellar electrokinetic chromatography, and two-phase partitioning for determining solute descriptors is described. A large database of experimental retention factors and partition coefficients is constructed after first applying selection tools to remove unreliable experimental values and an optimized collection of varied compounds with descriptor values suitable for calibrating chromatographic systems is presented. These optimized descriptors are demonstrated to be robust and more suitable than other groups of descriptors characterizing the separation properties of chromatographic systems.

  15. Determination of solute descriptors by chromatographic methods.

    Poole, Colin F; Atapattu, Sanka N; Poole, Salwa K; Bell, Andrea K

    2009-10-12

    The solvation parameter model is now well established as a useful tool for obtaining quantitative structure-property relationships for chemical, biomedical and environmental processes. The model correlates a free-energy related property of a system to six free-energy derived descriptors describing molecular properties. These molecular descriptors are defined as L (gas-liquid partition coefficient on hexadecane at 298K), V (McGowan's characteristic volume), E (excess molar refraction), S (dipolarity/polarizability), A (hydrogen-bond acidity), and B (hydrogen-bond basicity). McGowan's characteristic volume is trivially calculated from structure and the excess molar refraction can be calculated for liquids from their refractive index and easily estimated for solids. The remaining four descriptors are derived by experiment using (largely) two-phase partitioning, chromatography, and solubility measurements. In this article, the use of gas chromatography, reversed-phase liquid chromatography, micellar electrokinetic chromatography, and two-phase partitioning for determining solute descriptors is described. A large database of experimental retention factors and partition coefficients is constructed after first applying selection tools to remove unreliable experimental values and an optimized collection of varied compounds with descriptor values suitable for calibrating chromatographic systems is presented. These optimized descriptors are demonstrated to be robust and more suitable than other groups of descriptors characterizing the separation properties of chromatographic systems.

  16. DEVELOPMENT OF NOVEL CERAMIC NANOFILM-FIBER INTEGRATED OPTICAL SENSORS FOR RAPID DETECTION OF COAL DERIVED SYNTHESIS GAS

    Junhang Dong; Hai Xiao; Xiling Tang; Hongmin Jiang; Kurtis Remmel; Amardeep Kaur

    2012-09-30

    The overall goal of this project is to conduct fundamental studies on advanced ceramic materials and fiber optic devices for developing new types of high temperature (>500{degree}C) fiber optic chemical sensors (FOCS) for monitoring fossil (mainly coal) and biomass derived gases in power plants. The primary technical objective is to investigate and demonstrate the nanocrystalline doped-ceramic thin film enabled FOCS that possess desired stability, sensitivity and selectivity for in-situ, rapid gas detection in the syngas streams from gasification and combustion flue gases. This report summarizes research works of two integrated parts: (1) development of metal oxide solid thin films as sensing materials for detection and measurement of important gas components relevant to the coal- and biomass-derived syngas and combustion gas streams at high temperatures; and (2) development of fiber optic devices that are potentially useful for constructing FOCS in combination with the solid oxide thin films identified in this program.

  17. Properties of rapidly solidified Fe-Cr-Al ribbons for the use as automotive exhaust gas catalyst substrates

    Emmerich, K.

    1993-01-01

    Metallic honeycomb structures are used as catalyst substrates in automotive exhaust gas systems. This application requires an outstanding corrosion resistance at elevated temperatures of the substrate material. Technical improvements can be achieved by the use of rapid solidification technology for the production of the Fe-Cr-Al ribbons since the Al content can be substantially increased from about 5% Al in the conventionally rolled material to about 12% Al in the rapid solidified ribbon. As a result the lifetime of the ribbon in a higher-temperature corrosion environment is drastically increased. In addition the scale/metal adherance is improved. The impediment of recrystallization in the rapidly solidified ribbons prevents an embrittlement even in carbonizing atmospheres. (orig.)

  18. Rapid and selective detection of acetone using hierarchical ZnO gas sensor for hazardous odor markers application

    Jia, Qianqian; Ji, Huiming; Zhang, Ying; Chen, Yalu; Sun, Xiaohong; Jin, Zhengguo

    2014-01-01

    Highlights: • ZnO spheres fabricated via solvothermal method are with (0 0 2) polar facet exposed. • Response time of ZnO sensor for detecting 100 ppm acetone is as short as 3 s. • R a /R g toward 100 ppm acetone is 33 when operated at 230 °C. • ZnO sensor exhibits good selectivity against other toxic gases and water vapor. • Porous structure and exposure of polar facet contribute to good sensing properties. - Abstract: Hierarchical nanostructured ZnO dandelion-like spheres were synthesized via solvothermal reaction at 200 °C for 4 h. The products were pure hexagonal ZnO with large exposure of (0 0 2) polar facet. Side-heating gas sensor based on hierarchical ZnO spheres was prepared to evaluate the acetone gas sensing properties. The detection limit to acetone for the ZnO sensor is 0.25 ppm. The response (R a /R g ) toward 100 ppm acetone was 33 operated at 230 °C and the response time was as short as 3 s. The sensor exhibited remarkable acetone selectivity with negligible response toward other hazardous gases and water vapor. The high proportion of electron depletion region and oxygen vacancies contributed to high gas response sensitivity. The hollow and porous structure of dandelion-like ZnO spheres facilitated the diffusion of gas molecules, leading to a rapid response speed. The largely exposed (0 0 2) polar facets could adsorb acetone gas molecules easily and efficiently, resulting in a rapid response speed and good selectivity of hierarchical ZnO spheres gas sensor at low operating temperature

  19. Derivatization reactions in the gas—liquid chromatographic analysis of drugs in biological fluids

    Hulshoff, A.; Lingeman, H.

    1984-01-01

    Alkylation, acylation, silylation and other derivatization reactions applied to the gas chromatographic analysis of drugs in biological matrices are reviewed. Reaction conditions are discussed in relation to reaction mechanisms. Detector-oriented labelling of drugs, and derivatization with chiral

  20. Research on Rapid Identification and Evaluation Technology for Gas Formation during Underbalanced Drilling

    Hao Wu

    2017-01-01

    Full Text Available The underbalanced drilling (UBD technology has been widely implemented due to its advantages in drilling efficiency improvement and cost reduction. However, this advanced technology requires very special equipment and operational mechanism, which raises multiple challenges to traditional well logging techniques. In this study, a real-time logging system (MWD/LWD and mud logging was developed and utilized during underbalanced drilling, to quickly identify and evaluate gas formation. This advanced system enables fast detection of gas formation and determining the formation type while drilling, by monitoring the changes in gas production. This real-time logging system provides a powerful technical support to the gas reservoir drilling and development. A case study has clearly shown that the interpretation and evaluation results based on the real-time logging data agree well with the results of conventional well logging. Therefore, this advanced real-time logging technique can be utilized as an effective guidance for field operation.

  1. Rapid formation of gas giants, ice giants and super-Earths

    Boss, A P [DTM, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015 (United States)], E-mail: boss@dtm.ciw.edu

    2008-08-15

    Giant planets might have been formed by either of the two basic mechanisms, top-down (disk instability) or bottom-up (core accretion). The latter mechanism is the most generally accepted mechanism and it begins with the collisional accumulation of solid cores that may then accrete sufficient gas to become gas giants. The former mechanism is more heretical and begins with the gravitational instability of the protoplanetary disk gas, leading to the formation of self-gravitating protoplanets, within which the dust settles to form a solid core. The disk instability mechanism has been thought of primarily as a mechanism for the formation of gas giants, but if it occurs in a disk that is being photoevaporated by the ultraviolet radiation from nearby massive stars, then the outer gaseous protoplanets can be photoevaporated as well and stripped of their gaseous envelopes. The result would then be ice giants (cold super-Earths), such as the objects discovered recently by microlensing orbiting two presumed M dwarf stars. M dwarfs that form in regions of future high-mass star formation would be expected to produce cold super-Earths orbiting at distances of several astronomical units (AU) and beyond, while M dwarfs that form in regions of low-mass star formation would be expected to have gas giants at those distances. Given that most stars are born in the former rather than in the latter regions, M dwarfs should have significantly more super-Earths than gas giants on orbits of several AU or more.

  2. Rapid formation of gas giants, ice giants and super-Earths

    Boss, A P

    2008-01-01

    Giant planets might have been formed by either of the two basic mechanisms, top-down (disk instability) or bottom-up (core accretion). The latter mechanism is the most generally accepted mechanism and it begins with the collisional accumulation of solid cores that may then accrete sufficient gas to become gas giants. The former mechanism is more heretical and begins with the gravitational instability of the protoplanetary disk gas, leading to the formation of self-gravitating protoplanets, within which the dust settles to form a solid core. The disk instability mechanism has been thought of primarily as a mechanism for the formation of gas giants, but if it occurs in a disk that is being photoevaporated by the ultraviolet radiation from nearby massive stars, then the outer gaseous protoplanets can be photoevaporated as well and stripped of their gaseous envelopes. The result would then be ice giants (cold super-Earths), such as the objects discovered recently by microlensing orbiting two presumed M dwarf stars. M dwarfs that form in regions of future high-mass star formation would be expected to produce cold super-Earths orbiting at distances of several astronomical units (AU) and beyond, while M dwarfs that form in regions of low-mass star formation would be expected to have gas giants at those distances. Given that most stars are born in the former rather than in the latter regions, M dwarfs should have significantly more super-Earths than gas giants on orbits of several AU or more

  3. Miniaturized chromatographic radiochemical procedure for 131I - MIBG

    Barboza, M.F. de; Pereira, N.S. de; Colturato, M.T.; Silva, C.P.G. da.

    1989-12-01

    Different solvents were used in paper chromatographic methods to obtain the best system in routine radiochemical control for 131 I-MIBG produced at IPEN-CNEN/SP. The dates were compared with those obtained with eletrophoresis method in buffer acetate, pH=4.5, 350V, during 40 minutes. The stability of the labeled compound store under 4 0 C was studied during 15 days. Miniaturized chromatographic procedures were established using Whatman 3MM (8x1cm) and n-butanol-:acetic acid: water (S:2:1) as a solvent. the Rf values were: 0.3 (I - ) and 1.0 (MIBG). The radiochemical purity was 99.3 and 99.2% (first day) obtained with eletrophoresis and miniaturized chromatographic procedures, respectively and, 84.7% after 15 days of its preparation. It is a rapid, practical and reproductive method. (author) [pt

  4. Appearance of rapid carbon on hydrogasification of coal; Suiten gas ka ni okeru kokassei tanso no hatsugen

    Soneda, Y.; Makino, M. [National Institute for Resources and Environment, Tsukuba (Japan)9] Xu, W. [New Energy and Industrial Technology Development Organization, Tokyo, (Japan)

    1998-09-20

    The technology of hydrogasification of coal now under development under a State project aims to produce light oil as well as methane-rich high calorie gas through the direct reaction between coal and hydrogen, and is expected to deal with the difficult natural gas demand/supply relationship anticipated for the future. Although it is mandatory to fully understand the reaction between coal and hydrogen for the completion of this technology, yet there are many tasks to be fulfilled. One of the tasks is the elucidation of the behavior of what is named rapid carbon that appears upon the rapid heating of coal in a high-pressure hydrogen environment. In this paper, some interesting findings about the appearance of rapid carbon are reported. When coal is placed in such an environment, volatile components are lost first of all and then the active carbon reaction occurs. When the behavior of active carbon in the reaction is observed, it is found that active carbon is not so small in quantity, and the result of observation of its appearance and deactivation during the reaction justifies an inference that the reaction is regarded as one of the primary reactions in the process of hydrogasification. Accordingly, systematic studies of its physical and chemical features from various viewpoints are necessary. 5 refs., 3 figs., 1 tab.

  5. Research on waterhammer caused by a rapid gas production in the severe accident of a light water reactor

    Inasaka, Fujio; Adachi, Masaki; Shiozaki, Kohki; Aya, Izuo; Nariai, Hideki

    2004-01-01

    In the severe accident of an LWR (Light Water Reactor), it is supposed that a large quantity of gas is generated in a water pool of the containment vessel due to a water-metal reaction or a steam explosion. A rapid bubble growth, if the water mass is pushed up having a coherency in time and direction in its movement, would give a severe waterhammer to the structure. In this study, we conducted experiments using two cylindrical model containment vessels with 1.0 and 0.428 m diameters, and investigated the behavior of water mass pushed up by a growing bubble and the scale effect of this phenomenon. In addition, we also closely observed the heavier of a growing bubble. In these experiments, a rapid bubble growth was simulated by injecting high-pressure air into a water pool. It was observed that the water mass was pushed up without an air penetration until the water level reached a certain elevation. On the basis of all data, experimental correlations which gave a rise distance or velocity of the water mass with coherency were proposed and the waterhammer pressure which affected the structure was quantitatively evaluated. The applicability of the existing two-phase flow numerical analysis code, RELAP5-3D to the waterhammer phenomenon caused by a rapid gas production was also verified. (author)

  6. Rapid estimate of solid volume in large tuff cores using a gas pycnometer

    Thies, C.; Geddis, A.M.; Guzman, A.G.

    1996-09-01

    A thermally insulated, rigid-volume gas pycnometer system has been developed. The pycnometer chambers have been machined from solid PVC cylinders. Two chambers confine dry high-purity helium at different pressures. A thick-walled design ensures minimal heat exchange with the surrounding environment and a constant volume system, while expansion takes place between the chambers. The internal energy of the gas is assumed constant over the expansion. The ideal gas law is used to estimate the volume of solid material sealed in one of the chambers. Temperature is monitored continuously and incorporated into the calculation of solid volume. Temperature variation between measurements is less than 0.1 degrees C. The data are used to compute grain density for oven-dried Apache Leap tuff core samples. The measured volume of solid and the sample bulk volume are used to estimate porosity and bulk density. Intrinsic permeability was estimated from the porosity and measured pore surface area and is compared to in-situ measurements by the air permeability method. The gas pycnometer accommodates large core samples (0.25 m length x 0.11 m diameter) and can measure solid volume greater than 2.20 cm 3 with less than 1% error

  7. Rapid estimate of solid volume in large tuff cores using a gas pycnometer

    Thies, C. [ed.; Geddis, A.M.; Guzman, A.G. [and others

    1996-09-01

    A thermally insulated, rigid-volume gas pycnometer system has been developed. The pycnometer chambers have been machined from solid PVC cylinders. Two chambers confine dry high-purity helium at different pressures. A thick-walled design ensures minimal heat exchange with the surrounding environment and a constant volume system, while expansion takes place between the chambers. The internal energy of the gas is assumed constant over the expansion. The ideal gas law is used to estimate the volume of solid material sealed in one of the chambers. Temperature is monitored continuously and incorporated into the calculation of solid volume. Temperature variation between measurements is less than 0.1{degrees}C. The data are used to compute grain density for oven-dried Apache Leap tuff core samples. The measured volume of solid and the sample bulk volume are used to estimate porosity and bulk density. Intrinsic permeability was estimated from the porosity and measured pore surface area and is compared to in-situ measurements by the air permeability method. The gas pycnometer accommodates large core samples (0.25 m length x 0.11 m diameter) and can measure solid volume greater than 2.20 cm{sup 3} with less than 1% error.

  8. Rapid direct analysis to discriminate geographic origin of extra virgin olive oils by flash gas chromatography electronic nose and chemometrics.

    Melucci, Dora; Bendini, Alessandra; Tesini, Federica; Barbieri, Sara; Zappi, Alessandro; Vichi, Stefania; Conte, Lanfranco; Gallina Toschi, Tullia

    2016-08-01

    At present, the geographical origin of extra virgin olive oils can be ensured by documented traceability, although chemical analysis may add information that is useful for possible confirmation. This preliminary study investigated the effectiveness of flash gas chromatography electronic nose and multivariate data analysis to perform rapid screening of commercial extra virgin olive oils characterized by a different geographical origin declared in the label. A comparison with solid phase micro extraction coupled to gas chromatography mass spectrometry was also performed. The new method is suitable to verify the geographic origin of extra virgin olive oils based on principal components analysis and discriminant analysis applied to the volatile profile of the headspace as a fingerprint. The selected variables were suitable in discriminating between "100% Italian" and "non-100% Italian" oils. Partial least squares discriminant analysis also allowed prediction of the degree of membership of unknown samples to the classes examined. Copyright © 2016. Published by Elsevier Ltd.

  9. Development and validation of a highly sensitive gas chromatographic-mass spectrometric screening method for the simultaneous determination of nanogram levels of fentanyl, sufentanil and alfentanil in air and surface contamination wipes.

    Van Nimmen, Nadine F J; Veulemans, Hendrik A F

    2004-05-07

    A highly sensitive gas chromatographic-mass spectrometric (GC-MS) analytical method for the determination of the opioid narcotics fentanyl, alfentanil, and sufentanil in industrial hygiene personal air samples and surface contamination wipes was developed and comprehensively validated. Sample preparation involved a single step extraction of the samples with methanol, fortified with a fixed amount of the penta-deuterated analogues of the opioid narcotics as internal standard. The GC-MS analytical procedure using selected ion monitoring (SIM) was shown to be highly selective. Linearity was shown for levels of extracted wipe and air samples corresponding to at least 0.1-2 times their surface contamination limit (SCL) and accordingly to 0.1-2 times their time weighted average occupational exposure limit (OEL-TWA) based on a full shift 9601 air sample. Extraction recoveries were determined for spiked air samples and surface wipes and were found to be quantitative for both sampling media in the entire range studied. The air sampling method's limit of detection (LOD) was determined to be 0.4 ng per sample for fentanyl and sufentanil and 1.6 ng per sample for alfentanil, corresponding to less than 1% of their individual OEL for a full shift air sample (9601). The limit of quantification (LOQ) was found to be 1.4, 1.2, and 5.0 ng per filter for fentanyl, sufentanil, and alfentanil, respectively. The wipe sampling method had LODs of 4 ng per wipe for fentanyl and sufentanil and 16 ng per wipe for alfentanil and LOQs of respectively, 14, 12, and 50 ng per wipe. The analytical intra-assay precision of the air sampling and wipe sampling method, defined as the coefficient of variation on the analytical result of six replicate spiked media was below 10 and 5%, respectively, for all opioids at all spike levels. Accuracy expressed as relative error was determined to be below 10%, except for alfentanil at the lowest spike level (-13.1%). The stability of the opioids during simulated

  10. Water hammer caused by rapid gas production in a severe accident in a light water reactor

    Inasaka, Fujio; Adachi, Masaki; Aya, Izuo; Nariai, Hideki; Shiozaki, Kohki

    2005-01-01

    We investigated the water hammer caused by striking of water mass pushed up by a rapidly growing bubble and its scale effects using two cylindrical model containment vessels of 1.0 and 0.428 m diameters. We also closely observed the movement of water mass and the growing bubble in the vessels. In these experiments, rapid bubble growth was simulated by injecting high-pressure air into a water pool. It was clarified that the water mass was pushed up without any air penetration until the water level reached a certain elevation. On the basis of all data, experimental correlations for estimating the height and striking velocity of the water mass with coherency were proposed, and the water hammer pressure for exerting large forces on the structures was quantitatively evaluated. (author)

  11. Chromatographic and electrophoretic approaches in ink analysis.

    Zlotnick, J A; Smith, F P

    1999-10-15

    Inks are manufactured from a wide variety of substances that exhibit very different chemical behaviors. Inks designed for use in different writing instruments or printing methods have quite dissimilar components. Since the 1950s chromatographic and electrophoretic methods have played important roles in the analysis of inks, where compositional information may have bearing on the investigation of counterfeiting, fraud, forgery, and other crimes. Techniques such as paper chromatography and electrophoresis, thin-layer chromatography, high-performance liquid chromatography, gas chromatography, gel electrophoresis, and the relatively new technique of capillary electrophoresis have all been explored as possible avenues for the separation of components of inks. This paper reviews the components of different types of inks and applications of the above separation methods are reviewed.

  12. Rapid X-ray crystal structure analysis in few second measurements using microstrip gas chamber

    Ochi, A; Tanimori, T; Ohashi, Y; Toyokawa, H; Nishi, Y; Nishi, Y; Nagayoshi, T; Koishi, S

    2001-01-01

    X-ray crystal structure analysis using microstrip gas chamber was successfully carried out in a measurement time within a few seconds. The continuous rotation photograph method, in which most of the diffraction peaks can be obtained within one continuous rotation of the sample crystal (without stopping or oscillation), was applied for this measurement. As an example, the structure of a single crystal of ammonium bitartrate (r=1 mm, spherical) was measured. Diffraction spots from the sample, which were sufficient to obtain crystal structure, were successfully obtained by taking only 2 s measurements with a commercially available laboratory X-ray source.

  13. Rapid One-Pot Microwave Synthesis of Mixed-Linker Hybrid Zeolitic-Imidazolate Framework Membranes for Tunable Gas Separations.

    Hillman, Febrian; Brito, Jordan; Jeong, Hae-Kwon

    2018-02-14

    The relatively slow and complex fabrication processes of polycrystalline metal-organic framework (MOF) membranes often times restrict their way to commercialization, despite their potential for molecular separation applications. Herein, we report a rapid one-pot microwave synthesis of mixed-linker hybrid zeolitic-imidazolate framework (ZIF) membranes consisting of 2-methylimidazolate (ZIF-8 linker) and benzimidazolate (ZIF-7 linker) linkers, termed ZIF-7-8 membranes. The fast-volumetric microwave heating in conjunction with a unique counter diffusion of metal and linker solutions enabled unprecedented rapid synthesis of well-intergrown ZIF-7-8 membranes in ∼90 s, the fastest MOF membrane preparation up to date. Furthermore, we were able to tune the molecular sieving properties of the ZIF-7-8 membranes by varying the benzimidazole-to-2-methylimidazole (bIm-to-mIm) linker ratio in the hybrid frameworks. The tuning of their molecular sieving properties led to the systematic change in the permeance and selectivity of various small gases. The unprecedented rapid synthesis of well-intergrown ZIF-7-8 membranes with tunable molecular sieving properties is an important step forward for the commercial gas separation applications of ZIF membranes.

  14. Micro-column plasma emission liquid chromatograph. [Patent application

    Gay, D.D.

    1982-08-12

    In a direct current plasma emission spectrometer for use in combination with a microcolumn liquid chromatograph, an improved plasma source unit is claimed. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

  15. Smart multi-channel two-dimensional micro-gas chromatography for rapid workplace hazardous volatile organic compounds measurement.

    Liu, Jing; Seo, Jung Hwan; Li, Yubo; Chen, Di; Kurabayashi, Katsuo; Fan, Xudong

    2013-03-07

    We developed a novel smart multi-channel two-dimensional (2-D) micro-gas chromatography (μGC) architecture that shows promise to significantly improve 2-D μGC performance. In the smart μGC design, a non-destructive on-column gas detector and a flow routing system are installed between the first dimensional separation column and multiple second dimensional separation columns. The effluent from the first dimensional column is monitored in real-time and decision is then made to route the effluent to one of the second dimensional columns for further separation. As compared to the conventional 2-D μGC, the greatest benefit of the smart multi-channel 2-D μGC architecture is the enhanced separation capability of the second dimensional column and hence the overall 2-D GC performance. All the second dimensional columns are independent of each other, and their coating, length, flow rate and temperature can be customized for best separation results. In particular, there is no more constraint on the upper limit of the second dimensional column length and separation time in our architecture. Such flexibility is critical when long second dimensional separation is needed for optimal gas analysis. In addition, the smart μGC is advantageous in terms of elimination of the power intensive thermal modulator, higher peak amplitude enhancement, simplified 2-D chromatogram re-construction and potential scalability to higher dimensional separation. In this paper, we first constructed a complete smart 1 × 2 channel 2-D μGC system, along with an algorithm for automated control/operation of the system. We then characterized and optimized this μGC system, and finally employed it in two important applications that highlight its uniqueness and advantages, i.e., analysis of 31 workplace hazardous volatile organic compounds, and rapid detection and identification of target gas analytes from interference background.

  16. Rapid screening and identification of illicit drugs by IR absorption spectroscopy and gas chromatography

    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.

  17. Versatile, ultra-low sample volume gas analyzer using a rapid, broad-tuning ECQCL and a hollow fiber gas cell

    Kriesel, Jason M.; Makarem, Camille N.; Phillips, Mark C.; Moran, James J.; Coleman, Max L.; Christensen, Lance E.; Kelly, James F.

    2017-05-01

    We describe a versatile mid-infrared (Mid-IR) spectroscopy system developed to measure the concentration of a wide range of gases with an ultra-low sample size. The system combines a rapidly-swept external cavity quantum cascade laser (ECQCL) with a hollow fiber gas cell. The ECQCL has sufficient spectral resolution and reproducibility to measure gases with narrow features (e.g., water, methane, ammonia, etc.), and also the spectral tuning range needed to measure volatile organic compounds (VOCs), (e.g., aldehydes, ketones, hydrocarbons), sulfur compounds, chlorine compounds, etc. The hollow fiber is a capillary tube having an internal reflective coating optimized for transmitting the Mid-IR laser beam to a detector. Sample gas introduced into the fiber (e.g., internal volume = 0.6 ml) interacts strongly with the laser beam, and despite relatively modest path lengths (e.g., L 3 m), the requisite quantity of sample needed for sensitive measurements can be significantly less than what is required using conventional IR laser spectroscopy systems. Example measurements are presented including quantification of VOCs relevant for human breath analysis with a sensitivity of 2 picomoles at a 1 Hz data rate.

  18. Versatile, ultra-low sample volume gas analyzer using a rapid, broad-tuning ECQCL and a hollow fiber gas cell

    Kriesel, Jason M.; Makarem, Camille N.; Phillips, Mark C.; Moran, James J.; Coleman, Max; Christensen, Lance; Kelly, James F.

    2017-05-05

    We describe a versatile mid-infrared (Mid-IR) spectroscopy system developed to measure the concentration of a wide range of gases with an ultra-low sample size. The system combines a rapidly-swept external cavity quantum cascade laser (ECQCL) with a hollow fiber gas cell. The ECQCL has sufficient spectral resolution and reproducibility to measure gases with narrow features (e.g., water, methane, ammonia, etc.), and also the spectral tuning range needed to measure volatile organic compounds (VOCs), (e.g., aldehydes, ketones, hydrocarbons), sulfur compounds, chlorine compounds, etc. The hollow fiber is a capillary tube having an internal reflective coating optimized for transmitting the Mid-IR laser beam to a detector. Sample gas introduced into the fiber (e.g., internal volume = 0.6 ml) interacts strongly with the laser beam, and despite relatively modest path lengths (e.g., L ~ 3 m), the requisite quantity of sample needed for sensitive measurements can be significantly less than what is required using conventional IR laser spectroscopy systems. Example measurements are presented including quantification of VOCs relevant for human breath analysis with a sensitivity of ~2 picomoles at a 1 Hz data rate.

  19. Assays for chloramphenicol compared: radioenzymatic, gas chromatographic with electron capture, and gas chromatographic-mass specteometric

    Pickering, L.K.; Hoecker, J.L.; Kramer, W.G.; Liehr, J.G.; Caprioli, R.M.

    1979-01-01

    We compared these three techniques for measuring chloramphenicol in serum or urine. Although each has its particular advantages, any of them is shown to be satisfactory and may appropriately be used by clinical laboratories, according to the facilities available

  20. Transformation kinetics of chlorinated ethenes by Methylosinus trichosporium OB3b and detection of unstable epoxides by on-line gas chromatography

    van Hylckama Vlieg, Johan. E.T.; Koning, Wim de; Janssen, Dick B.

    A rapid and accurate method for the determination of transformation kinetics of volatile organic substrates was developed. Concentrations were monitored by on-line gas chromatographic analysis of the headspace of well-mixed incubation mixtures. With this method, the kinetics of transformation of a

  1. Rapid hydraulic recovery in Eucalyptus pauciflora after drought: linkages between stem hydraulics and leaf gas exchange.

    Martorell, Sebastià; Diaz-Espejo, Antonio; Medrano, Hipólito; Ball, Marilyn C; Choat, Brendan

    2014-03-01

    In woody plants, photosynthetic capacity is closely linked to rates at which the plant hydraulic system can supply water to the leaf surface. Drought-induced embolism can cause sharp declines in xylem hydraulic conductivity that coincide with stomatal closure and reduced photosynthesis. Recovery of photosynthetic capacity after drought is dependent on restored xylem function, although few data exist to elucidate this coordination. We examined the dynamics of leaf gas exchange and xylem function in Eucalyptus pauciflora seedlings exposed to a cycle of severe water stress and recovery after re-watering. Stomatal closure and leaf turgor loss occurred at water potentials that delayed the extensive spread of embolism through the stem xylem. Stem hydraulic conductance recovered to control levels within 6 h after re-watering despite a severe drought treatment, suggesting an active mechanism embolism repair. However, stomatal conductance did not recover after 10 d of re-watering, effecting tighter control of transpiration post drought. The dynamics of recovery suggest that a combination of hydraulic and non-hydraulic factors influenced stomatal behaviour post drought. © 2013 John Wiley & Sons Ltd.

  2. Rapid solar-thermal dissociation of natural gas in an aerosol flow reactor

    Dahl, Jaimee K.; Buechler, Karen J.; Finley, Ryan; Stanislaus, Timothy; Weimer, Alan W.; Lewandowski, Allan; Bingham, Carl; Smeets, Alexander; Schneider, Adrian

    2004-01-01

    A solar-thermal aerosol flow reactor process is being developed to dissociate natural gas (NG) to hy drogen (H 2 ) and carbon black at high rates. Concentrated sunlight approaching 10 kW heats a 9.4 cm long x2.4 cm diameter graphite reaction tube to temperatures ∼2000 K using a 74% theoretically efficient secondary concentrator. Pure methane feed has been dissociated to 70% for residence times less than 0.1 s. The resulting carbon black is 20-40 nm in size, amorphous, and pure. A 5 million (M) kg/yr carbon black/1.67 M kg/yr H 2 plant is considered for process scale-up. The total permanent investment (TPI) of this plant is $12.7 M. A 15% IRR after tax is achieved when the carbon black is sold for $0.66/kg and the H 2 for $13.80/GJ. This plant could supply 0.06% of the world carbon black market. For this scenario, the solar-thermal process avoids 277 MJ fossil fuel and 13.9 kg-equivalent CO 2 /kg H 2 produced as compared to conventional steam-methane reforming and furnace black processing

  3. Gas evolution as a rapid screening method for detection of irradiated foods

    Roberts, P.B.; Chambers, D.M.; Brailsford, G.W.

    1996-01-01

    A number of detection methods for irradiated foods are in advanced state of development. No single method is likely to be universally applicable but a battery of tests such as thermoluminescence, electron spin resonance and analysis of lipid radiolytic products may soon be available for most foods and technical uses of irradiation. Most of these proposed tests require relatively sophisticated equipment or technical skills and are often time consuming and costly. There would be value in relatively simple tests which could be used as a rapid screening system or confirmatory method. The literature on the use of radiolytic gases as a detection method is limited and this paper extends the above studies. In particular, it extends the work to frozen shellfish, for which irradiation has been used as a commercial decontaminant technique for many years, and considers the effect of storage temperature. Work on poultry is also reported as a cross-reference to earlier work and because irradiated poultry has recently been released into the US retail trade. (author)

  4. Thin-film culturing technique allowing rapid gas-liquid equilibration (6 sec) with no toxicity to mammalian cells

    Koch, C.J.

    1984-01-01

    A method is described for inoculating mammalian cells onto the central area of glass petri dishes. The medium depth above the cells is only 100 μm for an added medium volume of 1 ml and increases linearly and rapidly with additional medium. The theoretical time constant for equilibration of the medium with the gas is related to the square of the medium depth. The experimental time constant was measured in two different ways for large and small medium depths, giving excellent agreement with the theoretical values. Although the time constant is only 6 sec for the case of 1 ml of added medium, there is no drying out of the medium or toxicity to the cells because of a large reservoir of medium in the meniscus at the periphery of the dish

  5. Development of a Method for Rapid Determination of Morpholine in Juices and Drugs by Gas Chromatography-Mass Spectrometry

    Mengsi Cao

    2018-01-01

    Full Text Available A reliable derivatization method has been developed to detect and quantify morpholine in apple juices and ibuprofen with gas chromatography-mass spectrometry. Morpholine can react with sodium nitrite under acidic condition to produce stable and volatile N-nitrosomorpholine derivative. In this experiment, various factors affecting the derivatization and extraction process were optimized, including volume and concentration of hydrochloric acid, quantity of sodium nitrite, derivatization temperature, derivatization time, extraction reagents, and extraction time. The derivative was extracted with dichloromethane and determined by gas chromatography-mass spectrometry. The linearity range of morpholine was 10–500 μg·L−1 with good correlation, and limits of detection (LOD and limits of quantification (LOQ were 7.3 μg·L−1 and 24.4 μg·L−1, respectively. Low, medium, and high concentrations of morpholine were added in apple juices and ibuprofen samples to evaluate standard recovery rate and relative standard deviation. The spiked recovery rate ranged from 94.3% to 109.0%, and the intraday repeatability and interday reproducibility were 2.0%–4.4% and 3.3%–7.0%, respectively. The developed method has good accuracy and precision. This quantitative method for morpholine is simple, sensitive, rapid, and low cost and can successfully be applied to analyze the residual morpholine in apple juices and drug samples.

  6. Realization of rapid debugging for detection circuit of optical fiber gas sensor: Using an analog signal source

    Tian, Changbin; Chang, Jun; Wang, Qiang; Wei, Wei; Zhu, Cunguang

    2015-03-01

    An optical fiber gas sensor mainly consists of two parts: optical part and detection circuit. In the debugging for the detection circuit, the optical part usually serves as a signal source. However, in the debugging condition, the optical part can be easily influenced by many factors, such as the fluctuation of ambient temperature or driving current resulting in instability of the wavelength and intensity for the laser; for dual-beam sensor, the different bends and stresses of the optical fiber will lead to the fluctuation of the intensity and phase; the intensity noise from the collimator, coupler, and other optical devices in the system will also result in the impurity of the optical part based signal source. In order to dramatically improve the debugging efficiency of the detection circuit and shorten the period of research and development, this paper describes an analog signal source, consisting of a single chip microcomputer (SCM), an amplifier circuit, and a voltage-to-current conversion circuit. It can be used to realize the rapid debugging detection circuit of the optical fiber gas sensor instead of optical part based signal source. This analog signal source performs well with many other advantages, such as the simple operation, small size, and light weight.

  7. Rapid changes in ice core gas records - Part 1: On the accuracy of methane synchronisation of ice cores

    Köhler, P.

    2010-08-01

    Methane synchronisation is a concept to align ice core records during rapid climate changes of the Dansgaard/Oeschger (D/O) events onto a common age scale. However, atmospheric gases are recorded in ice cores with a log-normal-shaped age distribution probability density function, whose exact shape depends mainly on the accumulation rate on the drilling site. This age distribution effectively shifts the mid-transition points of rapid changes in CH4 measured in situ in ice by about 58% of the width of the age distribution with respect to the atmospheric signal. A minimum dating uncertainty, or artefact, in the CH4 synchronisation is therefore embedded in the concept itself, which was not accounted for in previous error estimates. This synchronisation artefact between Greenland and Antarctic ice cores is for GRIP and Byrd less than 40 years, well within the dating uncertainty of CH4, and therefore does not calls the overall concept of the bipolar seesaw into question. However, if the EPICA Dome C ice core is aligned via CH4 to NGRIP this synchronisation artefact is in the most recent unified ice core age scale (Lemieux-Dudon et al., 2010) for LGM climate conditions of the order of three centuries and might need consideration in future gas chronologies.

  8. Development of a fast and simple gas chromatographic protocol based on the combined use of alkyl chloroformate and solid phase microextraction for the assay of polyamines in human urine.

    Naccarato, Attilio; Elliani, Rosangela; Cavaliere, Brunella; Sindona, Giovanni; Tagarelli, Antonio

    2018-05-11

    Polyamines are aliphatic amines with low molecular weight that are widely recognized as one of the most important cancer biomarkers for early diagnosis and treatment. The goal of the work herein presented is the development of a rapid and simple method for the quantification of free polyamines (i.e., putrescine, cadaverine, spermidine, spermine) and N-monoacetylated polyamines (i.e., N 1 -Acetylspermidine, N 8 -Acetylspermidine, and N 1 -Acetylspermine) in human urine. A preliminary derivatization with propyl chloroformate combined with the use of solid phase microextraction (SPME) allowed for an easy and automatable protocol involving minimal sample handling and no consumption of organic solvents. The affinity of the analytes toward five commercial SPME coatings was evaluated in univariate mode, and the best result in terms of analyte extraction was achieved using the divinylbenzene/carboxen/polydimethylsiloxane fiber. The variables affecting the performance of SPME analysis were optimized by the multivariate approach of experimental design and, in particular, using a central composite design (CCD). The optimal working conditions in terms of response values are the following: extraction temperature 40 °C, extraction time of 15 min and no addition of NaCl. Analyses were carried out by gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS) in selected reaction monitoring (SRM) acquisition mode. The developed method was validated according to the guidelines issued by the Food and Drug Administration (FDA). The satisfactory performances reached in terms of linearity, sensitivity (LOQs between 0.01 and 0.1 μg/mL), matrix effect (68-121%), accuracy, and precision (inter-day values between -24% and +16% and in the range 3.3-28.4%, respectively) make the proposed protocol suitable to be adopted for quantification of these important biomarkers in urine samples. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Simple setup for gas-phase h/d exchange mass spectrometry coupled to electron transfer dissociation and ion mobility for analysis of polypeptide structure on a liquid chromatographic time scale

    Mistarz, Ulrik Hvid; Brown, Jeffery M; Haselmann, Kim F

    2014-01-01

    gas immediately upstream or downstream of the primary skimmer cone. The approach was implemented on three commercially available mass spectrometers and required no or minor fully reversible reconfiguration of gas-inlets of the ion source. Results from gas-phase HDX-MS of peptides using the aqueous ND3....../D2O as HDX reagent indicate that labeling is facilitated exclusively through gaseous ND3, yielding similar results to the infusion of purified ND3-gas, while circumventing the complications associated with the use of hazardous purified gases. Comparison of the solution-phase- and gas-phase deuterium...

  10. Vibrational Spectroscopy of Chromatographic Interfaces

    Jeanne E. Pemberton

    2011-03-10

    Chromatographic separations play a central role in DOE-supported fundamental research related to energy, biological systems, the environment, and nuclear science. The overall portfolio of research activities in the Separations and Analysis Program within the DOE Office of Basic Energy Sciences includes support for activities designed to develop a molecular-level understanding of the chemical processes that underlie separations for both large-scale and analytical-scale purposes. The research effort funded by this grant award was a continuation of DOE-supported research to develop vibrational spectroscopic methods to characterize the interfacial details of separations processes at a molecular level.

  11. Decomposition of pilocarpine eye drops assessed by a highly efficient high pressure liquid chromatographic method

    Kuks, P. F.; Weekers, L. E.; Goldhoorn, P. B.

    1990-01-01

    A rapid high-resolution high pressure liquid chromatographic method was developed for assaying pilocarpine. Pilocarpine in ophthalmic solutions decomposes fairly rapidly to give isopilocarpine, pilocarpic acid and isopilocarpic acid. The quality of an ophthalmic solution can be assessed by assaying

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

    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. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Chiral ionic liquids in chromatographic and electrophoretic separations.

    Kapnissi-Christodoulou, Constantina P; Stavrou, Ioannis J; Mavroudi, Maria C

    2014-10-10

    This report provides an overview of the application of chiral ionic liquids (CILs) in separation technology, and particularly in capillary electrophoresis and both gas and liquid chromatography. There is a large number of CILs that have been synthesized and designed as chiral agents. However, only a few have successfully been applied in separation technology. Even though this application of CILs is still in its early stages, the scientific interest is increasing dramatically. This article is focused on the use of CILs as chiral selectors, background electrolyte additives, chiral ligands and chiral stationary phases in electrophoretic and chromatographic techniques. Different examples of CILs, which contain either a chiral cation, a chiral anion or both, are presented in this review article, and their major advantages along with their potential applications in chiral electrophoretic and chromatographic recognition are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Technical note: Rapid image-based field methods improve the quantification of termite mound structures and greenhouse-gas fluxes

    P. A. Nauer

    2018-06-01

    Full Text Available Termite mounds (TMs mediate biogeochemical processes with global relevance, such as turnover of the important greenhouse gas methane (CH4. However, the complex internal and external morphology of TMs impede an accurate quantitative description. Here we present two novel field methods, photogrammetry (PG and cross-sectional image analysis, to quantify TM external and internal mound structure of 29 TMs of three termite species. Photogrammetry was used to measure epigeal volume (VE, surface area (AE and mound basal area (AB by reconstructing 3-D models from digital photographs, and compared against a water-displacement method and the conventional approach of approximating TMs by simple geometric shapes. To describe TM internal structure, we introduce TM macro- and micro-porosity (θM and θμ, the volume fractions of macroscopic chambers, and microscopic pores in the wall material, respectively. Macro-porosity was estimated using image analysis of single TM cross sections, and compared against full X-ray computer tomography (CT scans of 17 TMs. For these TMs we present complete pore fractions to assess species-specific differences in internal structure. The PG method yielded VE nearly identical to a water-displacement method, while approximation of TMs by simple geometric shapes led to errors of 4–200 %. Likewise, using PG substantially improved the accuracy of CH4 emission estimates by 10–50 %. Comprehensive CT scanning revealed that investigated TMs have species-specific ranges of θM and θμ, but similar total porosity. Image analysis of single TM cross sections produced good estimates of θM for species with thick walls and evenly distributed chambers. The new image-based methods allow rapid and accurate quantitative characterisation of TMs to answer ecological, physiological and biogeochemical questions. The PG method should be applied when measuring greenhouse-gas emissions from TMs to avoid large errors from inadequate shape

  15. Rapid, Real-time Methane Detection in Ground Water Using a New Gas-Water Equilibrator Design

    Ruybal, C. J.; DiGiulio, D. C.; Wilkin, R. T.; Hargrove, K. D.; McCray, J. E.

    2014-12-01

    Recent increases in unconventional gas development have been accompanied by public concern for methane contamination in drinking water wells near production areas. Although not a regulated pollutant, methane may be a marker contaminant for others that are less mobile in groundwater and thus may be detected later, or at a location closer to the source. In addition, methane poses an explosion hazard if exsolved concentrations reach 5 - 15% volume in air. Methods for determining dissolved gases, such as methane, have evolved over 60 years. However, the response time of these methods is insufficient to monitor trends in methane concentration in real-time. To enable rapid, real-time monitoring of aqueous methane concentrations during ground water purging, a new gas-water equilibrator (GWE) was designed that increases gas-water mass exchange rates of methane for measurement. Monitoring of concentration trends allows a comparison of temporal trends between sampling events and comparison of baseline conditions with potential post-impact conditions. These trends may be a result of removal of stored casing water, pre-purge ambient borehole flow, formation physical and chemical heterogeneity, or flow outside of well casing due to inadequate seals. Real-time information in the field can help focus an investigation, aid in determining when to collect a sample, save money by limiting costs (e.g. analytical, sample transport and storage), and provide an immediate assessment of local methane concentrations. Four domestic water wells, one municipal water well, and one agricultural water well were sampled for traditional laboratory analysis and compared to the field GWE results. Aqueous concentrations measured on the GWE ranged from non-detect to 1,470 μg/L methane. Some trends in aqueous methane concentrations measured on the GWE were observed during purging. Applying a paired t-test comparing the new GWE method and traditional laboratory analysis yielded a p-value 0

  16. Rapid analysis of cyclamate in foods and beverages by gas chromatography-electron capture detector (GC-ECD).

    Yu, Shengbing; Zhu, Binghui; Lv, Fen; Li, Shaoxiao; Huang, Weixiong

    2012-10-15

    A rapid method for determination of sodium cyclamate in foods and beverages was developed. Sodium cyclamate was converted to N,N-dichloridecyclohexylamine by reaction with sodium hypochlorite under acid condition. N,N-dichloridecyclohexylamine was subsequently extracted by n-hexane and determined by gas chromatography. Conditions such as derivatization time, the concentration of sodium hypochlorite and sulphuric acid were optimised. Amino acids, aliphatic amines, and food additives such as preservatives, dyes and sweeteners showed no interference for quantification of cyclamate. The correlation coefficient of calibration curve was 0.9993 in the range of 5.0-250mg/L. The limits of detection (LOD) and limits of quantification (LOQ) were calculated as three or ten times the signal-to-noise ratio (S/N), respectively. The LOD and LOQ for yellow wine and fruit juice were 0.05 and 0.2mg/L, respectively. The LOD and LOQ for cake and preserved fruit were 0.25 and 0.8mg/kg, respectively. The intra-day and inter-day RSD were 0.28% and 1.1% (n=5), respectively. The method was successfully applied for determination of cyclamate in yellow wine, cake, fruit juice and preserved fruit. This method was simple, fast, and sensitive. It was suitable for the determination of cyclamate in foods and beverages for safety and quality control inspections. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Comprehensive two-dimensional gas chromatography in combination with rapid scanning quadrupole mass spectrometry in perfume analysis.

    Mondello, Luigi; Casillia, Alessandro; Tranchida, Peter Quinto; Dugo, Giovanni; Dugo, Paola

    2005-03-04

    Single column gas chromatography (GC) in combination with a flame ionization detector (FID) and/or a mass spectrometer is routinely employed in the determination of perfume profiles. The latter are to be considered medium to highly complex matrices and, as such, can only be partially separated even on long capillaries. Inevitably, several monodimensional peaks are the result of two or more overlapping components, often hindering reliable identification and quantitation. The present investigation is based on the use of a comprehensive GC (GC x GC) method, in vacuum outlet conditions, for the near to complete resolution of a complex perfume sample. A rapid scanning quadrupole mass spectrometry (qMS) system, employed for the assignment of GC x GC peaks, supplied high quality mass spectra. The validity of the three-dimensional (3D) GC x GC-qMS application was measured and compared to that of GC-qMS analysis on the same matrix. Peak identification, in all applications, was achieved through MS spectra library matching and the interactive use of linear retention indices (LRI).

  18. Rapid Determination of Clenbuterol in Pork by Direct Immersion Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry.

    Ye, Diru; Wu, Susu; Xu, Jianqiao; Jiang, Ruifen; Zhu, Fang; Ouyang, Gangfeng

    2016-02-01

    Direct immersion solid-phase microextraction (DI-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was developed for rapid analysis of clenbuterol in pork for the first time. In this work, a low-cost homemade 44 µm polydimethylsiloxane (PDMS) SPME fiber was employed to extract clenbuterol in pork. After extraction, derivatization was performed by suspending the fiber in the headspace of the 2 mL sample vial saturated with a vapor of 100 µL hexamethyldisilazane. Lastly, the fiber was directly introduced to GC-MS for analysis. All parameters that influenced absorption (extraction time), derivatization (derivatization reagent, time and temperature) and desorption (desorption time) were optimized. Under optimized conditions, the method offered a wide linear range (10-1000 ng g(-1)) and a low detection limit (3.6 ng g(-1)). Finally, the method was successfully applied in the analysis of pork from the market, and recoveries of the method for spiked pork were 97.4-105.7%. Compared with the traditional solvent extraction method, the proposed method was much cheaper and fast. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  19. Chromatographic Techniques for Rare Earth Elements Analysis

    Chen, Beibei; He, Man; Zhang, Huashan; Jiang, Zucheng; Hu, Bin

    2017-04-01

    The present capability of rare earth element (REE) analysis has been achieved by the development of two instrumental techniques. The efficiency of spectroscopic methods was extraordinarily improved for the detection and determination of REE traces in various materials. On the other hand, the determination of REEs very often depends on the preconcentration and separation of REEs, and chromatographic techniques are very powerful tools for the separation of REEs. By coupling with sensitive detectors, many ambitious analytical tasks can be fulfilled. Liquid chromatography is the most widely used technique. Different combinations of stationary phases and mobile phases could be used in ion exchange chromatography, ion chromatography, ion-pair reverse-phase chromatography and some other techniques. The application of gas chromatography is limited because only volatile compounds of REEs can be separated. Thin-layer and paper chromatography are techniques that cannot be directly coupled with suitable detectors, which limit their applications. For special demands, separations can be performed by capillary electrophoresis, which has very high separation efficiency.

  20. Chromatographic Separation of Vitamin E Enantiomers

    Ju-Yen Fu

    2017-02-01

    Full Text Available Vitamin E is recognized as an essential vitamin since its discovery in 1922. Most vegetable oils contain a mixture of tocopherols and tocotrienols in the vitamin E composition. Structurally, tocopherols and tocotrienols share a similar chromanol ring and a side chain at the C-2 position. Owing to the three chiral centers in tocopherols, they can appear as eight different stereoisomers. Plant sources of tocopherol are naturally occurring in the form of RRR while synthetic tocopherols are usually in the form of all-racemic mixture. Similarly, with only one chiral center, natural tocotrienols occur as the R-isoform. In this review, we aim to discuss a few chromatographic methods that had been used to separate the stereoisomers of tocopherols and tocotrienols. These methods include high performance liquid chromatography, gas chromatography and combination of both. The review will focus on method development including selection of chiral columns, detection method and choice of elution solvent in the context of separation efficiency, resolution and chiral purity. The applications for separation of enantiomers in vitamin E will also be discussed especially in terms of the distinctive biological potency among the stereoisoforms.

  1. Modeling Aquatic Toxicity through Chromatographic Systems.

    Fernández-Pumarega, Alejandro; Amézqueta, Susana; Farré, Sandra; Muñoz-Pascual, Laura; Abraham, Michael H; Fuguet, Elisabet; Rosés, Martí

    2017-08-01

    Environmental risk assessment requires information about the toxicity of the growing number of chemical products coming from different origins that can contaminate water and become toxicants to aquatic species or other living beings via the trophic chain. Direct toxicity measurements using sensitive aquatic species can be carried out but they may become expensive and ethically questionable. Literature refers to the use of chromatographic measurements that correlate to the toxic effect of a compound over a specific aquatic species as an alternative to get toxicity information. In this work, we have studied the similarity in the response of the toxicity to different species and we have selected eight representative aquatic species (including tadpoles, fish, water fleas, protozoan, and bacteria) with known nonspecific toxicity to chemical substances. Next, we have selected four chromatographic systems offering good perspectives for surrogation of the eight selected aquatic systems, and thus prediction of toxicity from the chromatographic measurement. Then toxicity has been correlated to the chromatographic retention factor. Satisfactory correlation results have been obtained to emulate toxicity in five of the selected aquatic species through some of the chromatographic systems. Other aquatic species with similar characteristics to these five representative ones could also be emulated by using the same chromatographic systems. The final aim of this study is to model chemical products toxicity to aquatic species by means of chromatographic systems to reduce in vivo testing.

  2. Microfabricated Gas Phase Chemical Analysis Systems

    FRYE-MASON, GREGORY CHARLES; HELLER, EDWIN J.; HIETALA, VINCENT M.; KOTTENSTETTE, RICHARD; LEWIS, PATRICK R.; MANGINELL, RONALD P.; MATZKE, CAROLYN M.; WONG, CHUNGNIN C.

    1999-01-01

    A portable, autonomous, hand-held chemical laboratory ((micro)ChemLab(trademark)) is being developed for trace detection (ppb) of chemical warfare (CW) agents and explosives in real-world environments containing high concentrations of interfering compounds. Microfabrication is utilized to provide miniature, low-power components that are characterized by rapid, sensitive and selective response. Sensitivity and selectivity are enhanced using two parallel analysis channels, each containing the sequential connection of a front-end sample collector/concentrator, a gas chromatographic (GC) separator, and a surface acoustic wave (SAW) detector. Component design and fabrication and system performance are described

  3. Chromatographic analysis and purification of multiply tritium-labelled eicosanoids

    Shevchenko, V.P.; Nagaev, I.Yu.; Myasoedov, N.F.

    1988-01-01

    A comparative study of different chromatographic techniques (gas-liquid (GLC), thin-layer (TLC), liquid (LC), high-pressure liquid (HPLC) chromatography) is presented. They were applied to the analysis and preparative purification of tritium-labelled eicosanoids with a molar radioactivity of 1.8-8.8 TBq/mmol, obtained by selective hydrogenation and by chemical or enzymic methods. The possibility of analyzing reaction mixtures and isolating individual multiply labelled eicosanoids with a chemical and radiochemical purity of 95-98% was demonstrated. Special features of HPLC for high molar radioactivity eicosanoids are considered. (author) 9 refs.; 6 tabs

  4. Rapid and simultaneous determination of polychlorinated biphenyls and their main metabolites (hydroxylated and methyl sulfonyl) by gas chromatography coupled to mass spectrometry: Comparison of different ionisation modes

    Castro-Puyana, M.; Herrero, L.; González, M.J.; Gómara, B.

    2013-01-01

    Graphical abstract: -- Highlights: •Simultaneous determination of PCB, OH-PCBs and MeSO 2 -PCBs in a single GC–MS run. •Two different ionisation modes (EI and ECNI) are studied and compared. •The analytical characterisation of both methods is satisfactory. •Better LODs are achieved using ECNI-MS as ionisation mode. •The developed methodology is successfully applied to fish liver oil. -- Abstract: Instrumental methods based on gas chromatography coupled to mass spectrometry (GC–MS) have been developed and compared using two different MS ionisation modes, electron impact (EI) and electron capture negative ionisation (ECNI), for the fast, quantitative and simultaneous determination of polychlorinated biphenyls (PCBs) and their main metabolites (hydroxylated PCBs, OH-PCBs, and methyl sulfone PCBs, MeSO 2 -PCBs). Parameters affecting chromatographic separation and MS detection were evaluated in order to achieve the highest selectivity and sensitivity for both operation modes. The analytical characteristics of the developed methods were studied and compared in terms of linear range, limits of detection (LODs), limits of quantification (LOQs), and instrumental precision (repeatability and intermediate precision). Both ionisation methods showed similar precision, being relative standard deviations (RSD, %) lower than 9% and 14% for repeatability and intermediate precision, respectively. However, better LODs (from 0.01 to 0.14 pg injected for the three families of congeners studied) were achieved using ECNI-MS as ionisation mode. The suitability of the developed method was demonstrated through their application to fish liver oil samples

  5. Large-volume constant-concentration sampling technique coupling with surface-enhanced Raman spectroscopy for rapid on-site gas analysis.

    Zhang, Zhuomin; Zhan, Yisen; Huang, Yichun; Li, Gongke

    2017-08-05

    In this work, a portable large-volume constant-concentration (LVCC) sampling technique coupling with surface-enhanced Raman spectroscopy (SERS) was developed for the rapid on-site gas analysis based on suitable derivatization methods. LVCC sampling technique mainly consisted of a specially designed sampling cell including the rigid sample container and flexible sampling bag, and an absorption-derivatization module with a portable pump and a gas flowmeter. LVCC sampling technique allowed large, alterable and well-controlled sampling volume, which kept the concentration of gas target in headspace phase constant during the entire sampling process and made the sampling result more representative. Moreover, absorption and derivatization of gas target during LVCC sampling process were efficiently merged in one step using bromine-thiourea and OPA-NH 4 + strategy for ethylene and SO 2 respectively, which made LVCC sampling technique conveniently adapted to consequent SERS analysis. Finally, a new LVCC sampling-SERS method was developed and successfully applied for rapid analysis of trace ethylene and SO 2 from fruits. It was satisfied that trace ethylene and SO 2 from real fruit samples could be actually and accurately quantified by this method. The minor concentration fluctuations of ethylene and SO 2 during the entire LVCC sampling process were proved to be gas targets from real samples by SERS. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. High-resolution gas chromatographic analysis of polycyclic aromatic hydrocarbons and aliphatic hydrocarbons; Separacion por cromatografia de gases de alta eficiencia de hidrocarburos aromaticos policiclicos, (PAH) y alifaticos (AH) ambientales, empleado como fases estacionarias OV-1 y SE-54

    Perez, M.; Gonzalez, D.

    1988-07-01

    A study of the analysis by gas chromatography of aromatic polycyclic hydrocarbons and aliphatic hydrocarbons is presented. The separation has been carried out by glass and fused silica capillary column in two different polar stationary phases OV-1 and SE-54. The limitation and the advantages of the procedure are discussed in terms of separation, sensitivity and precision. (Author) 20 refs.

  7. Gas

    1996-01-01

    The French government has decided to modify the conditions of extension of local natural gas authorities to neighbouring districts. The European Union is studying the conditions of internal gas market with the objective of more open markets although considering public service requirements

  8. Chromatographic retention and structure roofing tile effect of isomers and its fine structure

    Walraven, J.J.; Ladon, A.W.; Keulemans, A.I.M.

    1968-01-01

    Logarithmic plots of gas chromatographic retention data for different classes of compds. on different pairs of stationary phases were constructed. A remarkable effect was found. Isomers are spread along parallel lines in a repeated pattern, forming a \\"roofing-tile\\" series. The scattering of points

  9. Large-volume constant-concentration sampling technique coupling with surface-enhanced Raman spectroscopy for rapid on-site gas analysis

    Zhang, Zhuomin; Zhan, Yisen; Huang, Yichun; Li, Gongke

    2017-08-01

    In this work, a portable large-volume constant-concentration (LVCC) sampling technique coupling with surface-enhanced Raman spectroscopy (SERS) was developed for the rapid on-site gas analysis based on suitable derivatization methods. LVCC sampling technique mainly consisted of a specially designed sampling cell including the rigid sample container and flexible sampling bag, and an absorption-derivatization module with a portable pump and a gas flowmeter. LVCC sampling technique allowed large, alterable and well-controlled sampling volume, which kept the concentration of gas target in headspace phase constant during the entire sampling process and made the sampling result more representative. Moreover, absorption and derivatization of gas target during LVCC sampling process were efficiently merged in one step using bromine-thiourea and OPA-NH4+ strategy for ethylene and SO2 respectively, which made LVCC sampling technique conveniently adapted to consequent SERS analysis. Finally, a new LVCC sampling-SERS method was developed and successfully applied for rapid analysis of trace ethylene and SO2 from fruits. It was satisfied that trace ethylene and SO2 from real fruit samples could be actually and accurately quantified by this method. The minor concentration fluctuations of ethylene and SO2 during the entire LVCC sampling process were proved to be samples were achieved in range of 95.0-101% and 97.0-104% respectively. It is expected that portable LVCC sampling technique would pave the way for rapid on-site analysis of accurate concentrations of trace gas targets from real samples by SERS.

  10. Rapid Economic Growth and Natural Gas Consumption Nexus: Looking forward from Perspective of 11th Malaysian Plan

    Bekhet, H. A.; Yasmin, T.

    2016-03-01

    The present study investigates the relationship between economic growth and energy consumption by incorporating CO2 emissions, natural gas consumption and population in Malaysia. Annual data and F-bound test and granger causality have applied to test the existence of long run relationship between the series. The results show that variables are cointegrated for long run relationship. The results also indicate that natural gas consumption is an important contributing factor to energy demand and hence economic growth in case of Malaysia. The causality analysis highlights that the feedback hypothesis exists between economic growth and energy consumption. While, conservative hypothesis is validated between natural gas consumption and economic growth which implies that economic growth will push natural gas consumption policies in future. This study opens up new direction for policy makers to formulate a comprehensive natural gas policy to sustain environment for long span of time in case to achieve 11th MP targets.

  11. Development of analytical methods for the gas chromatographic determination of 1,2-epoxy-3-butene, 1,2:3,4-diepoxybutane, 3-butene-1,2-diol, 3,4-epoxybutane-1,2-diol and crotonaldehyde from perfusate samples of 1,3-butadiene exposed isolated mouse and rat livers

    Bhowmik, S.; Schuster, A.; Filser, J.G.

    2003-07-01

    Mutagenicity and carcinogenicity of 1,3-butadiene (BD) highly probably results from epoxide metabolites as 1,2-epoxy-3-butene (EB), 1,2:3,4-diepoxybutane (DEB) and 3,4-epoxybutane-1,2-diol (EBD). A further metabolite crotonaldehyde (CA) has also been discussed to be relevant. So far, in BD exposed rodents only EB and DEB concentrations had been quantified. However, the methods used were either not very sensitive or instrumentally expensive. Therefore, the goal of the present work was to establish simple analytical methods selective and sensitive enough to determine all of these compounds and a further secondary BD intermediate, 3-butene-1,2-diol (B-diol), in BD exposed rodent livers. The once-through perfused liver system was chosen for testing the applicability of the methods to be developed, since it enables BD exposures of this quantitatively most relevant metabolising organ near to the in-vivo situation. All the metabolites were extracted from the aqueous perfusion medium and analysed using a gas chromatograph equipped with a mass selective detector (GC/MS) in the PCI mode. (orig.)

  12. Preparation of {sup 183,184}Re samples for modelling a rapid gas phase chemistry of Nielsbohrium (Ns), element 107

    Eichler, R.; Gaeggeler, H.W.; Eichler, B.; Tuerler, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Chemical gas phase reactions of the heavier group 7 elements in the system O{sub 2}/H{sub 2}O are presumably best suited for a separation of Nielsbohrium from the lighter transactinides. We expect a higher reaction velocity using the more reactive gas system O{sub 3}/H{sub 2}O{sub 2}. For the experimental verification of this idea we prepared {sup 183}Re/{sup 184}Re samples for thermochromatography experiments with both gas systems. (author) 8 refs.

  13. Mechanical stability of a salt cavern submitted to rapid pressure variations: Application to the underground storage of natural gas, compressed air and hydrogen

    Djizanne-Djakeun, Hippolyte

    2014-01-01

    Salt caverns used for the underground storage of large volumes of natural gas are in high demand given the ever-increasing energy needs. The storage of renewable energy is also envisaged in these salt caverns for example, storage of compressed air and hydrogen mass storage. In both cases, salt caverns are more solicited than before because they are subject to rapid injection and withdrawal rates. These new operating modes raise new mechanical problems, illustrated in particular by sloughing, and falling of overhanging blocks at cavern wall. Indeed, to the purely mechanical stress related to changes in gas pressure variations, repeated dozens of degrees Celsius of temperature variation are superimposed; causes in particular during withdrawal, additional tensile stresses whom may lead to fractures at cavern wall; whose evolution could be dangerous. The mechanical behavior of rock salt is known: it is elasto-viscoplastic, nonlinear and highly thermo sensitive. The existing rock salt constitutive laws and failures and damages criteria have been used to analyze the behavior of caverns under the effects of these new loading. The study deals with the thermo mechanics of rocks and helps to analyze the effects of these new operations modes on the structural stability of salt caverns. The approach was to firstly design and validate a thermodynamic model of the behavior of gas in the cavern. This model was used to analyze blowout in gas salt cavern. Then, with the thermo mechanical coupling, to analyze the effects of rapid withdrawal, rapid injection and daily cycles on the structural stability of caverns. At the experimental level, we sought the optimal conditions to the occurrence and the development of cracks on a pastille and a block of rock salt. The creep behavior of rock salt specimens in triaxial extension also was analyzed. (author)

  14. Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of semivolatile organic compounds in bottom sediment by solvent extraction, gel permeation chromatographic fractionation, and capillary-column gas chromatography/mass spectrometry

    Furlong, E.T.; Vaught, D.G.; Merten, L.M.; Foreman, W.T.; Gates, Paul M.

    1996-01-01

    A method for the determination of 79 semivolatile organic compounds (SOCs) and 4 surrogate compounds in soils and bottom sediment is described. The SOCs are extracted from bottom sediment by solvent extraction, followed by partial isolation using high-performance gel permeation chromatography (GPC). The SOCs then are qualitatively identified and quantitative concentrations determined by capillary-column gas chromatography/mass spectrometry (GC/MS). This method also is designed for an optional simultaneous isolation of polychlorinated biphenyls (PCBs) and organochlorine (OC) insecticides, including toxaphene. When OCs and PCBs are determined, an additional alumina- over-silica column chromatography step follows GPC cleanup, and quantitation is by dual capillary- column gas chromatography with electron-capture detection (GC/ECD). Bottom-sediment samples are centrifuged to remove excess water and extracted overnight with dichloromethane. The extract is concentrated, centrifuged, and then filtered through a 0.2-micrometer polytetrafluoro-ethylene syringe filter. Two aliquots of the sample extract then are quantitatively injected onto two polystyrene- divinylbenzene GPC columns connected in series. The SOCs are eluted with dichloromethane, a fraction containing the SOCs is collected, and some coextracted interferences, including elemental sulfur, are separated and discarded. The SOC-containing GPC fraction then is analyzed by GC/MS. When desired, a second aliquot from GPC is further processed for OCs and PCBs by combined alumina-over-silica column chromatography. The two fractions produced in this cleanup then are analyzed by GC/ECD. This report fully describes and is limited to the determination of SOCs by GC/MS.

  15. High Performance Liquid Chromatographic Method for Determination of Dipyridamole in Human Plasma

    DAVOOD BEIGI BAND ARAB ADI

    1999-08-01

    Full Text Available A simple, rapid and specific high-performance liquid chromatographic procedure is reported for"nquantitative determination of dipyridamole in human -plasma. The assay uses a reversed-phase"nhigh-performance liquid chromatographic (HPLC and UV detection at 280nm and has a limit"nof detection of approximately 5ng/mL. The mobile phase consists of MeOH-H20 (60:40"nadjusted to pH 3.3. Dipyridamole was extracted from plasma by back-extraction procedure, with"npropranolol as the internal standard. The reproducibility of the method is satisfactory

  16. More than 170 polyunsaturated tocopherol-related compounds in a vitamin E capsule: Countercurrent chromatographic enrichment, gas chromatography/mass spectrometry analysis and preliminary identification of the potential artefacts.

    Hammann, Simon; Kröpfl, Alexander; Vetter, Walter

    2016-12-09

    Tocopherols and tocotrienols (usually summed up as vitamin E) are a class of structurally related natural antioxidants. Commonly, only some of the eight classic representatives (four tocopherols and four tocotrienols) are found with varied composition in food. In this study we fractionated 230mg oil from commercial vitamin E supplement capsules by countercurrent chromatography (CCC) and subsequent analysis by gas chromatography with mass spectrometry (GC/MS) of silylated CCC fractions showed that these eight isomers represented only about 70% of total tocopherol compounds. Detailed analysis enabled the detection of 161T 3 isomers (α-, γ- and δ-T 3 ) along with 18 tetra- and several penta-unsaturated isomers (tocools), two tocomonoenol isomers, and several degradation products with shorter isoprenoid side chain (apo-tocools). Altogether, over 170 tocool compounds, most likely artefacts which originated from an inappropriate oil refining process were described in this study. Silver ion high performance liquid chromatography (Ag + -HPLC) was used to separate one fraction rich in γ-T 3 into four peaks each consisting of at least five peaks according to GC/MS. About ten γ-T 3 isomers were also detected in rice bran oils from one producer bought retail in Germany. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Liquid-liquid extraction/headspace/gas chromatographic/mass spectrometric determination of benzene, toluene, ethylbenzene, (o-, m- and p-)xylene and styrene in olive oil using surfactant-coated carbon nanotubes as extractant.

    Carrillo-Carrión, Carolina; Lucena, Rafael; Cárdenas, Soledad; Valcárcel, Miguel

    2007-11-09

    BTEX-S compounds are widely distributed in the environment and can be present in different foodstuffs, including olive oil. Taking into account the risks of the exposure to these compounds, analytical methods for their determination in different matrices are mandatory. In this paper, the use of surfactant-coated multiwalled carbon nanotubes as additive in liquid-liquid extraction is applied for the determination of single-ring aromatic compounds in olive oil samples. After sample treatment, the aqueous extracts are subsequently analyzed by headspace/gas chromatography/mass spectrometry allowing the determination of BTEX-S within ca. 15 min. Each stage of the proposed LLE/HS/GC/MS configuration involves a selectivity enhancement avoiding the interference of other compounds of the sample matrix. Limits of detection were in the range 0.25 ng mL(-1) (obtained for ethylbenzene) and 0.43 ng mL(-1) (for benzene). The repeatability of the proposed method expressed as RSD varied between 1.9% (styrene) and 3.3% (benzene) (n=11).

  18. A novel analytical method of 1-(3-trifluoromethylphenyl piperazine and 1-(3-chlorophenyl piperazine in fluids of drug addicts using liquid-liquid extraction-gas chromatographic/nitrogen-phosphorous detection

    Jing Chang

    2017-01-01

    Full Text Available In accordance with the research specifications and guidelines in China, we developed a novel experimental method to detect new piperazine-type drugs, such as 1-(3-trifluoromethylphenyl piperazine and 1-(3-chlorophenyl piperazine. In this study, a new pretreatment method and gas chromatography (GC/nitrogen-phosphorus detector detection technique were used to characterize these two kinds of drugs in urine and blood samples. For the purpose of isolation of these trace drugs from the samples, liquid-liquid extraction/solid-phase extraction was modified and validated for this specific study. The pretreatment method presented in this paper has many advantages, such as high recovery rate, high extraction efficiency, high detection sensitivity, low limit of detection, and simple operation. The GC/NPD instrument is popular in most laboratories because it can meet the routine requirements of forensic science. All these aspects make this combination of sample pretreatment and GC/NPD technique the most suitable choice for drug detection in biological samples.

  19. An inquiry into prospects for the Dutch industry in the rapidly growing natural gas business in Egypt

    Naarding, C.J.

    1999-06-01

    The prospects for the production of natural gas in Egypt are very high. Expectations are that a fully developed national market can be served for many decades to come and that above that substantial exports will be possible. The Egyptian government puts much effort in further development of the home market. Gas usage for power generation and industrial applications like fertiliser plants, chemical industries and cement production is to be maximised. Six Public Distribution Companies have been founded, each serving a certain geographical area. Various export possibilities, markets and delivery modes are being studied, but decisions are not expected in a short time. The National Government is dominating the gas scene in Egypt trough the EGPC. The organisation is clearly defined and participation of private companies and investors is increasing. The Egyptian market is open for foreign equipment and services. Interested companies have to qualify for the excepted vendor list via a standardised procedure. The use of an agent is the sole decision of the vendor. Through the whole range of activities, from exploration to domestic gas utilisation, many opportunities for Dutch equipment manufacturers and vendors of services are specified. Large investments are expected for the development of the new offshore prospects and the infrastructure needed to bring the production to the end consumers. Especially the connection to natural gas of several million households is an opportunity for consulting firms and suppliers of equipment. Also new laws to preserve the environment bring niches for Dutch experience, skills and materials. Together with private investors participation in new projects is asked for. Doing business in Egypt has special angles and cultural aspects that are worthwhile learning and working along. Building a fruitful relationship is time consuming but inevitable. Patience is needed for working in Egypt but the results can be rewarding. Egypt offers many

  20. Shrinking of silicon nanocrystals embedded in an amorphous silicon oxide matrix during rapid thermal annealing in a forming gas atmosphere

    van Sebille, M.; Fusi, A.; Xie, L.; Ali, H.; van Swaaij, R. A. C. M. M.; Leifer, K.; Zeman, M.

    2016-09-01

    We report the effect of hydrogen on the crystallization process of silicon nanocrystals embedded in a silicon oxide matrix. We show that hydrogen gas during annealing leads to a lower sub-band gap absorption, indicating passivation of defects created during annealing. Samples annealed in pure nitrogen show expected trends according to crystallization theory. Samples annealed in forming gas, however, deviate from this trend. Their crystallinity decreases for increased annealing time. Furthermore, we observe a decrease in the mean nanocrystal size and the size distribution broadens, indicating that hydrogen causes a size reduction of the silicon nanocrystals.

  1. Comparison of a disposable sorptive sampler with thermal desorption in a gas chromatographic inlet, or in a dedicated thermal desorber, to conventional stir bar sorptive extraction-thermal desorption for the determination of micropollutants in water.

    Wooding, Madelien; Rohwer, Egmont R; Naudé, Yvette

    2017-09-01

    The presence of micropollutants in the aquatic environment is a worldwide environmental concern. The diversity of micropollutants and the low concentration levels at which they may occur in the aquatic environment have greatly complicated the analysis and detection of these chemicals. Two sorptive extraction samplers and two thermal desorption methods for the detection of micropollutants in water were compared. A low-cost, disposable, in-house made sorptive extraction sampler was compared to SBSE using a commercial Twister sorptive sampler. Both samplers consisted of polydimethylsiloxane (PDMS) as a sorptive medium to concentrate micropollutants. Direct thermal desorption of the disposable samplers in the inlet of a GC was compared to conventional thermal desorption using a commercial thermal desorber system (TDS). Comprehensive gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-TOFMS) was used for compound separation and identification. Ten micropollutants, representing a range of heterogeneous compounds, were selected to evaluate the performance of the methods. The in-house constructed sampler, with its associated benefits of low-cost and disposability, gave results comparable to commercial SBSE. Direct thermal desorption of the disposable sampler in the inlet of a GC eliminated the need for expensive consumable cryogenics and total analysis time was greatly reduced as a lengthy desorption temperature programme was not required. Limits of detection for the methods ranged from 0.0010 ng L -1 to 0.19 ng L -1 . For most compounds, the mean (n = 3) recoveries ranged from 85% to 129% and the % relative standard deviation (% RSD) ranged from 1% to 58% with the majority of the analytes having a %RSD of less than 30%. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Chromatographic properties PLOT multicapillary columns.

    Nikolaeva, O A; Patrushev, Y V; Sidelnikov, V N

    2017-03-10

    Multicapillary columns (MCCs) for gas chromatography make it possible to perform high-speed analysis of the mixtures of gaseous and volatile substances at a relatively large amount of the loaded sample. The study was performed using PLOT MCCs for gas-solid chromatography (GSC) with different stationary phases (SP) based on alumina, silica and poly-(1-trimethylsilyl-1-propyne) (PTMSP) polymer as well as porous polymers divinylbenzene-styrene (DVB-St), divinylbenzene-vinylimidazole (DVB-VIm) and divinylbenzene-ethylene glycol dimethacrylate (DVB-EGD). These MCCs have the efficiency of 4000-10000 theoretical plates per meter (TP/m) and at a column length of 25-30cm can separate within 10-20s multicomponent mixtures of substances belonging to different classes of chemical compounds. The sample amount not overloading the column is 0.03-1μg and depends on the features of a porous layer. Examples of separations on some of the studied columns are considered. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Gas exchange recovery following natural drought is rapid unless limited by loss of leaf hydraulic conductance: evidence from an evergreen woodland.

    Skelton, Robert P; Brodribb, Timothy J; McAdam, Scott A M; Mitchell, Patrick J

    2017-09-01

    Drought can cause major damage to plant communities, but species damage thresholds and postdrought recovery of forest productivity are not yet predictable. We used an El Niño drought event as a natural experiment to test whether postdrought recovery of gas exchange could be predicted by properties of the water transport system, or if metabolism, primarily high abscisic acid concentration, might delay recovery. We monitored detailed physiological responses, including shoot sapflow, leaf gas exchange, leaf water potential and foliar abscisic acid (ABA), during drought and through the subsequent rehydration period for a sample of eight canopy and understory species. Severe drought caused major declines in leaf water potential, elevated foliar ABA concentrations and reduced stomatal conductance and assimilation rates in our eight sample species. Leaf water potential surpassed levels associated with incipient loss of leaf hydraulic conductance in four species. Following heavy rainfall gas exchange in all species, except those trees predicted to have suffered hydraulic impairment, recovered to prestressed rates within 1 d. Recovery of plant gas exchange was rapid and could be predicted by the hydraulic safety margin, providing strong support for leaf vulnerability to water deficit as an index of damage under natural drought conditions. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  4. Simultaneous multi-laser, multi-species trace-level sensing of gas mixtures by rapidly swept continuous-wave cavity-ringdown spectroscopy.

    He, Yabai; Kan, Ruifeng; Englich, Florian V; Liu, Wenqing; Orr, Brian J

    2010-09-13

    The greenhouse-gas molecules CO(2), CH(4), and H(2)O are detected in air within a few ms by a novel cavity-ringdown laser-absorption spectroscopy technique using a rapidly swept optical cavity and multi-wavelength coherent radiation from a set of pre-tuned near-infrared diode lasers. The performance of various types of tunable diode laser, on which this technique depends, is evaluated. Our instrument is both sensitive and compact, as needed for reliable environmental monitoring with high absolute accuracy to detect trace concentrations of greenhouse gases in outdoor air.

  5. Rapid and sensitive trace gas detection with continuous wave Optical Parametric Oscillator-based Wavelength Modulation Spectroscopy

    Arslanov, D.D.; Spunei, M.; Ngai, A.K.Y.; Cristescu, S.M.; Lindsay, I.D.; Lindsay, I.D.; Boller, Klaus J.; Persijn, S.T.; Harren, F.J.M.

    2011-01-01

    A fiber-amplified Distributed Bragg Reflector diode laser is used to pump a continuous wave, singly resonant Optical Parametric Oscillator (OPO). The output radiation covers the 3–4 μm with ability of rapid (100 THz/s) and broad mode-hop-free tuning (5 cm−1). Wavelength Modulation Spectroscopy is

  6. Determinação de efedrinas em urina por cromatografia em fase gasosa (CG/DNP para o controle da dopagem no esporte Gas chromatographic method for the determination of ephedrines in urine for doping control purposes

    Paula Rodrigues Garcia

    2005-09-01

    included in the prohibited list of substances by the International Olympic Committee (IOC. Urinary threshold concentrations were established (ephedrine and methylephedrine >10 µg/mL. The aim of this work was to develop and validate a method for the simultaneous determination of ephedrines present in urine samples for doping purposes by gas chromatography with nitrogenous-phosphorous detector (GC/NPD. The method was based on a liquid-liquid extraction of alkalinized urine and further derivatization with trifluoroacetic anhydride (TFA. The validated method showed to be simple, practical and linear at the studied concentrations range. Urine samples collected from volunteers, who reported the use of ephedrines, were submitted to the proposed method.

  7. Warping methods for spectroscopic and chromatographic signal alignment: A tutorial

    Bloemberg, Tom G., E-mail: T.Bloemberg@science.ru.nl [Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands); Radboud University Nijmegen, Education Institute for Molecular Sciences, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands); Gerretzen, Jan; Lunshof, Anton [Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands); Wehrens, Ron [Centre for Research and Innovation, Fondazione Edmund Mach, Via E. Mach, 1, 38010 San Michele all’Adige, TN (Italy); Buydens, Lutgarde M.C. [Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands)

    2013-06-05

    Highlights: •The concepts of warping and alignment are introduced. •The most important warping methods are critically reviewed and explained. •Reference selection, evaluation and place of warping in preprocessing are discussed. •Some pitfalls, especially for LC–MS and similar data, are addressed. •Examples are provided, together with programming scripts to rework and extend them. -- Abstract: Warping methods are an important class of methods that can correct for misalignments in (a.o.) chemical measurements. Their use in preprocessing of chromatographic, spectroscopic and spectrometric data has grown rapidly over the last decade. This tutorial review aims to give a critical introduction to the most important warping methods, the place of warping in preprocessing and current views on the related matters of reference selection, optimization, and evaluation. Some pitfalls in warping, notably for liquid chromatography–mass spectrometry (LC–MS) data and similar, will be discussed. Examples will be given of the application of a number of freely available warping methods to a nuclear magnetic resonance (NMR) spectroscopic dataset and a chromatographic dataset. As part of the Supporting Information, we provide a number of programming scripts in Matlab and R, allowing the reader to work the extended examples in detail and to reproduce the figures in this paper.

  8. Technical artifacts in chromatographic analysis of Tc-99m radiopharmaceuticals

    Kowalsky, R.J.; Creekmore, J.R.

    1982-01-01

    Technical artifacts produced during chromatographic analysis of technetium radiopharmaceuticals were investigated. Such artifacts are, we found, caused by improper spotting and drying techniques; these in turn produce spuriously high impurities in Tc-99m complexes of DTPA, MDP, PPi, and GH. The ITLC-SG/acetone system produces considerable streaking of Tc-complex if the applied spot is large and not dried before development. This results in activity in the solvent front portion of the chromatographic strip indicating falsely high levels of pertechnetate impurity. Proper drying of the applied spot eliminates the artifact. The ITLC-SG/saline system yields falsely high, hydrolyzed-reduced technetium impurities if the spot is allowed to enter the solvent during development. Correct spot placement and size eliminate this problem. Strips that are allowed to dry in room air for several minutes may indicate considerable pertechnetate impurity on the chromatogram; yet this may not actually be present in the radiopharmaceutical vial. Drying spots rapidly with hot air or in a nitrogen atmosphere before development eliminates this problem

  9. Ion Chromatographic Analyses of Sea Waters, Brines and Related Samples

    Nataša Gros

    2013-06-01

    Full Text Available This review focuses on the ion chromatographic methods for the analyses of natural waters with high ionic strength. At the beginning a natural diversity in ionic composition of waters is highlighted and terminology clarified. In continuation a brief overview of other review articles of potential interest is given. A review of ion chromatographic methods is organized in four sections. The first section comprises articles focused on the determination of ionic composition of water samples as completely as possible. The sections—Selected Anions, Selected Cations and Metals—follow. The most essential experimental conditions used in different methods are summarized in tables for a rapid comparison. Techniques encountered in the reviewed articles comprise: direct determinations of ions in untreated samples with ion- or ion-exclusion chromatography, or electrostatic ion chromatography; matrix elimination with column-switching; pre-concentration with a chelation ion chromatography and purge-and-trap pre-concentration. Different detection methods were used: non-suppressed conductometric or suppressed conductometric, direct spectrometric or spectrometric after a post-column derivetization, and inductively coupled plasma in combination with optical emission or mass spectrometry.

  10. Fiber-optic sensors for rapid, inexpensive characterization of soil and ground water contamination

    Milanovich, F.P.; Yow, J.L. Jr.

    1994-08-01

    The extent and complexity of worldwide environmental contamination are great enough that characterization, remediation, and performance monitoring will be extremely costly and lengthy. Characterization techniques that are rapid, inexpensive, and simple and that do not generate waste are urgently needed. Towards this end LLNL is developing a fiber-optic chemical sensor technology for use in groundwater and vadose-zone monitoring. We use a colorimetric detection technique, based on an irreversible chemical reaction between a specific reagent and the target compound. The accuracy and sensitivity of the sensor (<5 ppb by weight in water, determined by comparison with gas chromatographic standard measurements) are sufficient for environmental monitoring of trichloroethylene (TCE) and chloroform

  11. Chromatographic, Spectroscopic and Mass Spectrometric Approaches for Exploring the Habitability of Mars in 2012 and Beyond with the Curiosity Rover

    Mahaffy, Paul

    2012-01-01

    The Sample Analysis at Mars (SAM) suite of instruments on the Curiosity Rover of Mars Science Laboratory Mission is designed to provide chemical and isotopic analysis of organic and inorganic volatiles for both atmospheric and solid samples. The goals of the science investigation enabled by the gas chromatograph mass spectrometer and tunable laser spectrometer instruments of SAM are to work together with the other MSL investigations is to quantitatively assess habitability through a series of chemical and geological measurements. We describe the multi-column gas chromatograph system employed on SAM and the approach to extraction and analysis of organic compounds that might be preserved in ancient martian rocks.

  12. Rapid synthesis and characterization of hybrid ZnO@Au core–shell nanorods for high performance, low temperature NO{sub 2} gas sensor applications

    Ponnuvelu, Dinesh Veeran [Nanosensor Laboratory, PSG Institute of Advanced Studies, Coimbatore 641 004 (India); Pullithadathil, Biji, E-mail: bijuja123@yahoo.co.in [Nanosensor Laboratory, PSG Institute of Advanced Studies, Coimbatore 641 004 (India); Prasad, Arun K.; Dhara, Sandip [Surface and Nanoscience Division, Indira Gandhi Center for Atomic Research, Kalpakkam (India); Ashok, Anuradha [Nanosensor Laboratory, PSG Institute of Advanced Studies, Coimbatore 641 004 (India); Mohamed, Kamruddin; Tyagi, Ashok Kumar [Surface and Nanoscience Division, Indira Gandhi Center for Atomic Research, Kalpakkam (India); Raj, Baldev [Nanosensor Laboratory, PSG Institute of Advanced Studies, Coimbatore 641 004 (India)

    2015-11-15

    Graphical abstract: - Highlights: • Hybrid ZnO@Au core–shell nanorods were developed using rapid chemical method that can be used as a high performance, low temperature NO{sub 2} gas sensor. • Surface defect analysis (PL and XPS) clearly illustrates the presence of surface oxygen species and Zn interstitials involved in charge transport properties in-turn affecting gas sensing properties. • Hybrid ZnO@Au core–shell nanorods establish enhanced gas sensing performance at 150 °C compared to ZnO (300 °C) with a lower detection limit of 500 ppb using conventional electrodes. • The enhanced performance of ZnO@Au core–shell nanorods based sensor was owing to the presence of Au nanoclusters on the surface of ZnO nanorods which is attributed to the formation of Schottky contacts at the interfaces leading to sensitization effects. • The hybrid material found to be selective toward NO{sub 2} gas and highly stable in nature. - Abstract: A rapid synthesis route for hybrid ZnO@Au core–shell nanorods has been realized for ultrasensitive, trace-level NO{sub 2} gas sensor applications. ZnO nanorods and hybrid ZnO@Au core–shell nanorods are structurally analyzed using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Optical characterization using UV–visible (UV–vis), photoluminescence (PL) and Raman spectroscopies elucidate alteration in the percentage of defect and charge transport properties of ZnO@Au core–shell nanorods. The study reveals the accumulation of electrons at metal–semiconductor junctions leading to upward band bending for ZnO and thus favors direct electron transfer from ZnO to Au nanoclusters, which mitigates charge carrier recombination process. The operating temperature of ZnO@Au core–shell nanorods based sensor significantly decreased to 150 °C compared to alternate NO{sub 2} sensors (300 °C). Moreover, a linear sensor response in the range of 0.5–5

  13. Liquid chromatographic-mass spectrometric method for ...

    Tropical Journal of Pharmaceutical Research ... Purpose: To develop and validate a simple, efficient and reliable Liquid chromatographic-mass spectrometric (LC-MS/MS) method for the quantitative determination of two dermatological drugs, ... By Country · List All Titles · Free To Read Titles This Journal is Open Access.

  14. Liquid chromatographic analysis of phenobarbitone, ethosuximide ...

    A liquid chromatographic method for the simultaneous assay of four anticonvulsant drugs, phenobarbitone, ethosuximide, phenytoin and carbamazepine on a polystyrene-divinyl benzene column is described. The method was developed by the systematic study of different types of co-polymer materials, type and ...

  15. Validated high performance liquid chromatographic (HPLC) method ...

    STORAGESEVER

    2010-02-22

    Feb 22, 2010 ... specific and accurate high performance liquid chromatographic method for determination of ZER in micro-volumes ... tional medicine as a cure for swelling, sores, loss of appetite and ... Receptor Activator for Nuclear Factor κ B Ligand .... The effect of ... be suitable for preclinical pharmacokinetic studies. The.

  16. Chromatographic characterisation, in vitro antioxidant and free ...

    Chromatographic fractionation and spectroscopic analysis of the ME4 fraction revealed the presence of four compounds namely garcinia biflavonoids GB1 and GB2, garcinal and garcinoic acid. These findings show that these four compounds are partly responsible for the great antioxidant potential of G. kola seeds.

  17. Identificação de compostos orgânicos e farmacêuticos em esgoto hospitalar utilizando cromatografia gasosa acoplada a espectrometria de massa Identification of organic and pharmaceutical compositions in hospital wastewater using a gas chromatograph coupled to mass spectrometry

    Francisco Vieira Paiva

    2011-03-01

    Full Text Available Os resíduos líquidos provenientes dos estabelecimentos assistenciais de saúde são mais complexos do que os esgotos domésticos. Sua composição contém inúmeros compostos farmacêuticos, saneantes, elementos radiativos e de laboratórios. O conhecimento desses compostos pode auxiliar na escolha do tratamento adequado para esses esgotos e diminuir os impactos ambientais nos corpos receptores. A pesquisa foi realizada utilizando um sistema combinado (UASB e lodos ativados para tratar a água residuária de um hospital. Neste trabalho, foram realizadas análises físico-químicas para caracterização do esgoto e cromatografia gasosa acoplada à espectrometria de massa para identificação de compostos químicos farmacêuticos, podendo-se constatar a presença de inúmeros elementos residuais dos fármacos usados no hospital.Liquid waste residues from health care establishments are more complex than those from residential sewage. Their composition contains several pharmaceutical chemical composites, sanitizers, radioactive, and laboratorial elements. Knowing about these composites may aid in choosing the proper treatment for these sewages, and diminish the environmental impact in receptors. The study was carried out in a combined system (UASB and activated sludge to treat a hospital wastewater. In this experiment, material and chemical analyses were employed to trace sewage characteristics and gas chromatography associated with mass spectrometry to identify pharmacologic chemical composites, where innumerous residual elements were found in chromatographs.

  18. Effects of chromatographic fractions of Euphorbia hirta on the rat ...

    The effects of the chromatographic fractions of Euphorbia hirta Linn on the serum biochemical parameters in rats were investigated. The ethanolic extract of this plant was subjected to chromatographic separation using the vacuum liquid chromatographic technique, a modified form of classical column chromatography.

  19. Chromatographic assay of degradation products of tributyl phosphate

    Tripathi, S.C.; Ramanujam, A.; Nadkarni, M.N.; Rao, K.A.; Bandyopadhyay, C.

    1985-01-01

    Gas-liquid chromatography (GLC) and thin-layer chromatographic (TLC) procedures have been developed for the estimation of monobutyl phosphoric acid (H 2 MBP) and dibutyl phosphoric acid (HDBP) present in tributyl phosphate (TBP). Less than one microgram of H 2 MBP and HDBP is visually detected on TLC plate made of silicagel-cellulose (1:1). HDBP as separated by TLC has been quantitatively estimated in the range of 40-260 μg using an indirect spectrophotometric method. GLC method using 10 percent (W/W) XE-60 column can be effectively used for the simultaneous determination of 0.25 percent W/V H 2 MBP and HDBP present in 30 percent TBP-n-dodecane. The sensitivity may be enhanced 100 fold by careful column conditioning and judicious control of operational parameters. (author)

  20. Chromatographic separation of radioactive noble gases from xenon

    Akerib, D. S.; Araújo, H. M.; Bai, X.; Bailey, A. J.; Balajthy, J.; Beltrame, P.; Bernard, E. P.; Bernstein, A.; Biesiadzinski, T. P.; Boulton, E. M.; Bramante, R.; Cahn, S. B.; Carmona-Benitez, M. C.; Chan, C.; Chiller, A. A.; Chiller, C.; Coffey, T.; Currie, A.; Cutter, J. E.; Davison, T. J. R.; Dobi, A.; Dobson, J. E. Y.; Druszkiewicz, E.; Edwards, B. N.; Faham, C. H.; Fiorucci, S.; Gaitskell, R. J.; Gehman, V. M.; Ghag, C.; Gibson, K. R.; Gilchriese, M. G. D.; Hall, C. R.; Hanhardt, M.; Haselschwardt, S. J.; Hertel, S. A.; Hogan, D. P.; Horn, M.; Huang, D. Q.; Ignarra, C. M.; Ihm, M.; Jacobsen, R. G.; Ji, W.; Kamdin, K.; Kazkaz, K.; Khaitan, D.; Knoche, R.; Larsen, N. A.; Lee, C.; Lenardo, B. G.; Lesko, K. T.; Lindote, A.; Lopes, M. I.; Manalaysay, A.; Mannino, R. L.; Marzioni, M. F.; McKinsey, D. N.; Mei, D.-M.; Mock, J.; Moongweluwan, M.; Morad, J. A.; Murphy, A. St. J.; Nehrkorn, C.; Nelson, H. N.; Neves, F.; O'Sullivan, K.; Oliver-Mallory, K. C.; Palladino, K. J.; Pease, E. K.; Pech, K.; Phelps, P.; Reichhart, L.; Rhyne, C.; Shaw, S.; Shutt, T. A.; Silva, C.; Solovov, V. N.; Sorensen, P.; Stephenson, S.; Sumner, T. J.; Szydagis, M.; Taylor, D. J.; Taylor, W.; Tennyson, B. P.; Terman, P. A.; Tiedt, D. R.; To, W. H.; Tripathi, M.; Tvrznikova, L.; Uvarov, S.; Verbus, J. R.; Webb, R. C.; White, J. T.; Whitis, T. J.; Witherell, M. S.; Wolfs, F. L. H.; Yazdani, K.; Young, S. K.; Zhang, C.

    2018-01-01

    The Large Underground Xenon (LUX) experiment operates at the Sanford Underground Research Facility to detect nuclear recoils from the hypothetical Weakly Interacting Massive Particles (WIMPs) on a liquid xenon target. Liquid xenon typically contains trace amounts of the noble radioactive isotopes 85Kr and 39Ar that are not removed by the in situ gas purification system. The decays of these isotopes at concentrations typical of research-grade xenon would be a dominant background for a WIMP search experiment. To remove these impurities from the liquid xenon, a chromatographic separation system based on adsorption on activated charcoal was built. 400 kg of xenon was processed, reducing the average concentration of krypton from 130 ppb to 3.5 ppt as measured by a cold-trap assisted mass spectroscopy system. A 50 kg batch spiked to 0.001 g/g of krypton was processed twice and reduced to an upper limit of 0.2 ppt.

  1. Hydraulics and gas exchange recover more rapidly from severe drought stress in small pot-grown grapevines than in field-grown plants.

    Romero, Pascual; Botía, Pablo; Keller, Markus

    2017-09-01

    Modifications of plant hydraulics and shoot resistances (R shoot ) induced by water withholding followed by rewatering, and their relationships with plant water status, leaf gas exchange and water use efficiency at the leaf level, were investigated in pot-grown and field-grown, own-rooted Syrah grapevines in an arid climate. Water stress induced anisohydric behavior, gradually reducing stomatal conductance (g s ) and leaf photosynthesis (A) in response to decreasing midday stem water potential (Ψ s ). Water stress also rapidly increased intrinsic water-use efficiency (A/g s ); this effect persisted for many days after rewatering. Whole-plant (K plant ), canopy (K canopy ), shoot (K shoot ) and leaf (K leaf ) hydraulic conductances decreased during water stress, in tune with the gradual decrease in Ψ s , leaf gas exchange and whole plant water use. Water-stressed vines also had a lower Ψ gradient between stem and leaf (ΔΨ l ), which was correlated with lower leaf transpiration rate (E). E and ΔΨ l increased with increasing vapour pressure deficit (VPD) in non-stressed control vines but not in stressed vines. Perfusion of xylem-mobile dye showed that water flow to petioles and leaves was substantially reduced or even stopped under moderate and severe drought stress. Leaf blade hydraulic resistance accounted for most of the total shoot resistance. However, hydraulic conductance of the whole root system (K root ) was not significantly reduced until water stress became very severe in pot-grown vines. Significant correlations between K plant , K canopy and Ψ s , K canopy and leaf gas exchange, K leaf and Ψ s , and K leaf and A support a link between water supply, leaf water status and gas exchange. Upon re-watering, Ψ s recovered faster than gas exchange and leaf-shoot hydraulics. A gradual recovery of hydraulic functionality of plant organs was also observed, the leaves being the last to recover after rewatering. In pot-grown vines, K canopy recovered rather

  2. Rapid and long-term effects of water deficit on gas exchange and hydraulic conductance of silver birch trees grown under varying atmospheric humidity.

    Sellin, Arne; Niglas, Aigar; Õunapuu-Pikas, Eele; Kupper, Priit

    2014-03-24

    Effects of water deficit on plant water status, gas exchange and hydraulic conductance were investigated in Betula pendula under artificially manipulated air humidity in Eastern Estonia. The study was aimed to broaden an understanding of the ability of trees to acclimate with the increasing atmospheric humidity predicted for northern Europe. Rapidly-induced water deficit was imposed by dehydrating cut branches in open-air conditions; long-term water deficit was generated by seasonal drought. The rapid water deficit quantified by leaf (ΨL) and branch water potentials (ΨB) had a significant (P gas exchange parameters, while inclusion of ΨB in models resulted in a considerably better fit than those including ΨL, which supports the idea that stomatal openness is regulated to prevent stem rather than leaf xylem dysfunction. Under moderate water deficit (ΨL≥-1.55 MPa), leaf conductance to water vapour (gL), transpiration rate and leaf hydraulic conductance (KL) were higher (P water deficit (ΨLwater availability, i.e. due to higher soil water potential in H treatment. Two functional characteristics (gL, KL) exhibited higher (P water deficit in trees grown under increased air humidity. The experiment supported the hypothesis that physiological traits in trees acclimated to higher air humidity exhibit higher sensitivity to rapid water deficit with respect to two characteristics - leaf conductance to water vapour and leaf hydraulic conductance. Disproportionate changes in sensitivity of stomatal versus leaf hydraulic conductance to water deficit will impose greater risk of desiccation-induced hydraulic dysfunction on the plants, grown under high atmospheric humidity, in case of sudden weather fluctuations, and might represent a potential threat in hemiboreal forest ecosystems. There is no trade-off between plant hydraulic capacity and photosynthetic water-use efficiency on short time scale.

  3. Characterization of Mycobacterium paratuberculosis by gas-liquid and thin-layer chromatography and rapid demonstration of mycobactin dependence using radiometric methods

    Damato, J.J.; Knisley, C.; Collins, M.T.

    1987-01-01

    Thirty-six Mycobacterium paratuberculosis isolates of bovine, caprine, and ovine origins were evaluated by using gas-liquid chromatography (GLC), thin-layer chromatography (TLC), and BACTEC 7H12 Middlebrook TB medium in an effort to more rapidly differentiate this group of organisms from other mycobacteria. Bacterial suspensions (0.1 ml) were inoculated by syringe into 7H12 broth containing 2 micrograms of mycobactin P per ml and control broth without mycobactin P. Cultures were incubated at 37 0 C and read daily with a BACTEC Model 301. After 8 days of incubation, the growth index readings for the test broths containing mycobactin P were twice those of the control broths without mycobactin P. Sixty-five isolates of mycobacteria other than M. paratuberculosis were also examined. No difference was noted between the growth index readings of control and mycobactin-containing broths. Except for Mycobacterium avium-Mycobacterium intracellulare, TLC studies differentiated M. paratuberculosis from the other mycobacterial species tested. The GLC data reveal that all M. paratuberculosis isolates had a distinctive peak (14A) which was not found among M. avium-M. intracellulare complex organisms. These data indicate that 7H12 radiometric broth was able to rapidly demonstrate the mycobactin dependence of M. paratuberculosis and GLC and TLC procedures were capable of rapidly differentiating this organism from the other mycobacteria studied

  4. Principles of qualitative analysis in the chromatographic context.

    Valcárcel, M; Cárdenas, S; Simonet, B M; Carrillo-Carrión, C

    2007-07-27

    This article presents the state of the art of qualitative analysis in the framework of the chromatographic analysis. After establishing the differences between two main classes of qualitative analysis (analyte identification and sample classification/qualification) the particularities of instrumental qualitative analysis are commented on. Qualitative chromatographic analysis for sample classification/qualification through the so-called chromatographic fingerprint (for complex samples) or the volatiles profile (through the direct coupling headspace-mass spectrometry using the chromatograph as interface) is discussed. Next, more technical exposition of the qualitative chromatographic information is presented supported by a variety of representative examples.

  5. Rapid identification of pork for halal authentication using the electronic nose and gas chromatography mass spectrometer with headspace analyzer.

    Nurjuliana, M; Che Man, Y B; Mat Hashim, D; Mohamed, A K S

    2011-08-01

    The volatile compounds of pork, other meats and meat products were studied using an electronic nose and gas chromatography mass spectrometer with headspace analyzer (GCMS-HS) for halal verification. The zNose™ was successfully employed for identification and differentiation of pork and pork sausages from beef, mutton and chicken meats and sausages which were achieved using a visual odor pattern called VaporPrint™, derived from the frequency of the surface acoustic wave (SAW) detector of the electronic nose. GCMS-HS was employed to separate and analyze the headspace gasses from samples into peaks corresponding to individual compounds for the purpose of identification. Principal component analysis (PCA) was applied for data interpretation. Analysis by PCA was able to cluster and discriminate pork from other types of meats and sausages. It was shown that PCA could provide a good separation of the samples with 67% of the total variance accounted by PC1. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Rapid determination of quetiapine in blood by gas chromatography-mass spectrometry. Application to post-mortem cases.

    López-Guarnido, Olga; Tabernero, María Jesús; Hernández, Antonio F; Rodrigo, Lourdes; Bermejo, Ana M

    2014-10-01

    A simple, fast and sensitive method for the determination of quetiapine in human blood has been developed and validated. The method involved a basic liquid-liquid extraction procedure and subsequent analysis by gas chromatography-mass spectrometry, previous derivatization with bis(trimethylsilyl)-trifluoro-acetamide and chorotrimethylsilane (99 : 1). The methods of validation included linearity with a correlation coefficient > 0.99 over the range 0.02-1 µg ml(-1), intra- and interday precision (always < 12%) and accuracy (mean relative error always < 12%) to meet the bioanalytical acceptance criteria. The limit of detection was 0.005 µg ml(-1). The procedure was further applied to post mortems from the Institute of Legal Medicine, University of Santiago de Compostela. Copyright © 2013 John Wiley & Sons, Ltd.

  7. Comparison of chromatographic methods for the determination of bound glycerol in biodiesel

    Foglia, T.A.; Jones, K.C.; Nunez, A.; Phillips, J.G. [U.S. Dept. of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Wyndmoor, PA (United States); Mittelbach, M. [Inst. for Chemistry, Univ. of Graz, Graz (Austria)

    2004-09-01

    An important fuel criterion for biodiesel is bound glycerol, which is a function of the residual amount of triglycerides and partial glycerides in the biodiesel. Either high-temperature gas chromatography or high performance liquid chromatography can be used for determining these minor but important components in biodiesel. In this paper we have conducted a statistical study on the accuracy of the two methods for ascertaining the bound glycerol in biodiesel fuels obtained from different feedstocks. Analysis of variance showed that with one exception, namely diacylglycerols in some soy oil based biodiesel, there was no statistical difference in bound glycerol for the biodiesel samples analyzed or a difference between methods. Operationally, the high performance liquid chromatographic method is superior to the high temperature gas chromatographic method in that it requires no sample derivatization, has shorter analysis times, and is directly applicable to most biodiesel fuels. (orig.)

  8. Rapid assessment of pulmonary gas transport with hyperpolarized 129Xe MRI using a 3D radial double golden-means acquisition with variable flip angles.

    Ruppert, Kai; Amzajerdian, Faraz; Hamedani, Hooman; Xin, Yi; Loza, Luis; Achekzai, Tahmina; Duncan, Ian F; Profka, Harrilla; Siddiqui, Sarmad; Pourfathi, Mehrdad; Cereda, Maurizio F; Kadlecek, Stephen; Rizi, Rahim R

    2018-04-22

    To demonstrate the feasibility of using a 3D radial double golden-means acquisition with variable flip angles to monitor pulmonary gas transport in a single breath hold with hyperpolarized xenon-129 MRI. Hyperpolarized xenon-129 MRI scans with interleaved gas-phase and dissolved-phase excitations were performed using a 3D radial double golden-means acquisition in mechanically ventilated rabbits. The flip angle was either held fixed at 15 ° or 5 °, or it was varied linearly in ascending or descending order between 5 ° and 15 ° over a sampling interval of 1000 spokes. Dissolved-phase and gas-phase images were reconstructed at high resolution (32 × 32 × 32 matrix size) using all 1000 spokes, or at low resolution (22 × 22 × 22 matrix size) using 400 spokes at a time in a sliding-window fashion. Based on these sliding-window images, relative change maps were obtained using the highest mean flip angle as the reference, and aggregated pixel-based changes were tracked. Although the signal intensities in the dissolve-phase maps were mostly constant in the fixed flip-angle acquisitions, they varied significantly as a function of average flip angle in the variable flip-angle acquisitions. The latter trend reflects the underlying changes in observed dissolve-phase magnetization distribution due to pulmonary gas uptake and transport. 3D radial double golden-means acquisitions with variable flip angles provide a robust means for rapidly assessing lung function during a single breath hold, thereby constituting a particularly valuable tool for imaging uncooperative or pediatric patient populations. © 2018 International Society for Magnetic Resonance in Medicine.

  9. Gas Chromatographic-Mass Spectrometric Analysis of Essential Oil ...

    hepatitis, dysmenorrhea, stomatitis, duodenitis and depression in south China [1]. There are few reports about its chemical constituents and pharmacological properties, such as the hydroalcoholic extract from the buds of. Jasminum grandiflorum showing preferable antiviral efficacy against HBV replication in. HepG2 2.2.15 ...

  10. Gas Chromatographic Analysis of Sulfur Mustard in Diethyl Phthalate

    Lancaster, Paul

    1998-01-01

    ...) that had been trapped in the solvent, diethyl phthalate (DEP) is described. The method utilises the improved sensitivity and selectivity offered by the new Pulsed Flame Photometric Detector to detect routinely samples containing...

  11. Gas chromatographic measurement of the radiolytic products of irradiated pork

    Zhou Yingcai; Wang Xiuying; Xu Peishu; Yuan Bihuai

    1988-01-01

    The radiolytic products of irradiated pork were isolated, analyzed and identified by the techniques of vacuum distillation, GC-MS. The higher boiling point compounds in fat were collected by cold-finger and its lower boiling point compounds were recovered on a short precolumn packed with alumina, and the volatiles of lean pork were collected on a short column packed with TCEP/Chromosovb. Some experimental conditions were studied. 49 compounds were identified. These compounds include hydrocarbons and sulphides etc. (author)

  12. Fluoroalkyl chloroformates in treating amino acids for gas chromatographic analysis

    Hušek, Petr; Šimek, Petr; Hartvich, Petr; Zahradníčková, Helena

    2008-01-01

    Roč. 1186, 1/2 (2008), s. 391-400 ISSN 0021-9673 R&D Projects: GA ČR GA203/04/0192; GA ČR GA303/06/1674 Institutional research plan: CEZ:AV0Z50070508 Keywords : amino acids * derivatization * pentafluoropropyl- and heptafluorobutyl chloroformates Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.756, year: 2008

  13. Improvement of gas chromatographic analysis for organic acids and ...

    Yomi

    2010-08-27

    Aug 27, 2010 ... and ethanol fermentation by using the anaerobic bacterium. Clostridium ... GC analysis. Standard solution for GC analysis consisted of acetic acid (Sigma-. Aldrich ... Microorganism and inoculum preparation. C. beijerinckii ...

  14. Amalgam-chromatographic separation of magnesium isotopes

    Klinskij, G.D.; Levkin, A.V.; Ivanov, S.A.

    1990-01-01

    Separation of magnesium isotopes within Mg(Hg)-MgI 2 system (in dimethylformamide) is conducted under amalgam-chromatographic conditions. Separation maximal degree, that is (1.09), for 24 Mg and 26 Mg and separation coefficient (α = 1.0089±0.006) are determined. Light isotopes are found to concentrate in the amalgam. Technique of thermal conversion of flows within amalgam-dimethylformamide system is suggested on the basis of reversible reaction of Ca-Mg element exchange

  15. Validation for chromatographic and electrophoretic methods

    Ribani, Marcelo; Bottoli, Carla Beatriz Grespan; Collins, Carol H.; Jardim, Isabel Cristina Sales Fontes; Melo, Lúcio Flávio Costa

    2004-01-01

    The validation of an analytical method is fundamental to implementing a quality control system in any analytical laboratory. As the separation techniques, GC, HPLC and CE, are often the principal tools used in such determinations, procedure validation is a necessity. The objective of this review is to describe the main aspects of validation in chromatographic and electrophoretic analysis, showing, in a general way, the similarities and differences between the guidelines established by the dif...

  16. Chromatographic Methods for the Analysis of Polyphenols in Wines

    Medić-Šarić, M.

    2009-03-01

    Full Text Available Wine is an excellent source of various classes of polyphenols, including phenolic acids, flavonoids, and trihydroxystilbene resveratrol (Fig.1. Polyphenols play a major role in wine quality since they contribute to the sensory characteristics of wine, particularly color and astringency. A recent interest in these substances has been stimulated by abundant evidence of their beneficial effects on human health, such as anticarcinogenic, antiinflamatory and antimicrobial activities. Therefore, numerous studies have been performed in the attempt to analyze polyphenols in wine. This paper reviews the current advances in the determination of polyphenols in wine by the major chromatographic techniques such as thin-layer chromatography (TLC and high-performance liquid chromatography (HPLC.The great complexity of the polyphenolic content of wine and the difficulty in obtaining some of the standards usually require sample preparation before analysis. Two methods for sample preparation, liquid-liquid extraction and solid-phase extraction, are most commonly applied. Hydrolysis is applied frequently, but not exclusively, to remove the sugar moieties from glycosides.TLC on silica gel plates is useful for the rapid and low-cost separation and identification of the polyphenols present in wine (Fig. 2. Densitometric quantitative analysis of polyphenols in wine extracts is usually performed by scanning the TLC plates with UV light at wavelengths of 350–365 nm or 250–260 nm (Fig. 3. For the evaluation of the most efficient mobile phase and an optimal choice of the combination of two or more mobile phases, two methods may be applied: information theory and numerical taxonomy. HPLC currently represents the most popular technique for the analysis of polyphenols in wine. For this purpose, a reversed-phase HPLC method that uses gradient elution with binary elution system is usually employed. Routine detection is based on measurement of UV-Vis absorption with a diode

  17. Analyzing chromatographic data using multilevel modeling.

    Wiczling, Paweł

    2018-06-01

    It is relatively easy to collect chromatographic measurements for a large number of analytes, especially with gradient chromatographic methods coupled with mass spectrometry detection. Such data often have a hierarchical or clustered structure. For example, analytes with similar hydrophobicity and dissociation constant tend to be more alike in their retention than a randomly chosen set of analytes. Multilevel models recognize the existence of such data structures by assigning a model for each parameter, with its parameters also estimated from data. In this work, a multilevel model is proposed to describe retention time data obtained from a series of wide linear organic modifier gradients of different gradient duration and different mobile phase pH for a large set of acids and bases. The multilevel model consists of (1) the same deterministic equation describing the relationship between retention time and analyte-specific and instrument-specific parameters, (2) covariance relationships relating various physicochemical properties of the analyte to chromatographically specific parameters through quantitative structure-retention relationship based equations, and (3) stochastic components of intra-analyte and interanalyte variability. The model was implemented in Stan, which provides full Bayesian inference for continuous-variable models through Markov chain Monte Carlo methods. Graphical abstract Relationships between log k and MeOH content for acidic, basic, and neutral compounds with different log P. CI credible interval, PSA polar surface area.

  18. Rapid Quantification of Major Volatile Metabolites in Fermented Food and Beverages Using Gas Chromatography-Mass Spectrometry

    Farhana R. Pinu

    2017-07-01

    Full Text Available Here we present a method for the accurate quantification of major volatile metabolites found in different food and beverages, including ethanol, acetic acid and other aroma compounds, using gas chromatography coupled to mass spectrometry (GC-MS. The method is combined with a simple sample preparation procedure using sodium chloride and anhydrous ethyl acetate. The GC-MS analysis was accomplished within 4.75 min, and over 80 features were detected, of which 40 were positively identified using an in-house and a commercialmass spectrometry (MS library. We determined different analytical parameters of these metabolites including the limit of detection (LOD, limit of quantitation (LOQ and range of quantification. In order to validate the method, we also determined detailed analytical characteristics of five major fermentation end products including ethanol, acetic acid, isoamyl alcohol, ethyl-L-lactate and, acetoin. The method showed very low technical variability for the measurements of these metabolites in different matrices (<3% with an excellent accuracy (100% ± 5%, recovery (100% ± 10%, reproducibility and repeatability [Coefficient of variation (CV 1–10%]. To demonstrate the applicability of the method, we analysed different fermented products including balsamic vinegars, sourdough, distilled (whisky and non-distilled beverages (wine and beer.

  19. Rapid Quantification of Major Volatile Metabolites in Fermented Food and Beverages Using Gas Chromatography-Mass Spectrometry.

    Pinu, Farhana R; Villas-Boas, Silas G

    2017-07-26

    Here we present a method for the accurate quantification of major volatile metabolites found in different food and beverages, including ethanol, acetic acid and other aroma compounds, using gas chromatography coupled to mass spectrometry (GC-MS). The method is combined with a simple sample preparation procedure using sodium chloride and anhydrous ethyl acetate. The GC-MS analysis was accomplished within 4.75 min, and over 80 features were detected, of which 40 were positively identified using an in-house and a commercialmass spectrometry (MS) library. We determined different analytical parameters of these metabolites including the limit of detection (LOD), limit of quantitation (LOQ) and range of quantification. In order to validate the method, we also determined detailed analytical characteristics of five major fermentation end products including ethanol, acetic acid, isoamyl alcohol, ethyl-L-lactate and, acetoin. The method showed very low technical variability for the measurements of these metabolites in different matrices (<3%) with an excellent accuracy (100% ± 5%), recovery (100% ± 10%), reproducibility and repeatability [Coefficient of variation (CV) 1-10%)]. To demonstrate the applicability of the method, we analysed different fermented products including balsamic vinegars, sourdough, distilled (whisky) and non-distilled beverages (wine and beer).

  20. Rapid determination of floral aroma compounds of lilac blossom by fast gas chromatography combined with surface acoustic wave sensor.

    Oh, Se Yeon; Shin, Hyun Du; Kim, Sung Jean; Hong, Jongki

    2008-03-07

    A novel analytical method using fast gas chromatography combined with surface acoustic wave sensor (GC/SAW) has been developed for the detection of volatile aroma compounds emanated from lilac blossom (Syringa species: Syringa vulgaris variginata and Syringa dilatata). GC/SAW could detect and quantify various fragrance emitted from lilac blossom, enabling to provide fragrance pattern analysis results. The fragrance pattern analysis could easily characterize the delicate differences in aromas caused by the substantial difference of chemical composition according to different color and shape of petals. Moreover, the method validation of GC/SAW was performed for the purpose of volatile floral actual aroma analysis, achieving a high reproducibility and excellent sensitivity. From the validation results, GC/SAW could serve as an alternative analytical technique for the analysis of volatile floral actual aroma of lilac. In addition, headspace solid-phase microextraction (HS-SPME) GC-MS was employed to further confirm the identification of fragrances emitted from lilac blossom and compared to GC/SAW.

  1. Development of a ROV Deployed Video Analysis Tool for Rapid Measurement of Submerged Oil/Gas Leaks

    Savas, Omer [Univ. of California, Berkeley, CA (United States)

    2017-04-03

    Expanded deep sea drilling around the globe makes it necessary to have readily available tools to quickly and accurately measure discharge rates from accidental submerged oil/gas leak jets for the first responders to deploy adequate resources for containment. We have developed and tested a field deployable video analysis software package which is able to provide in the field sufficiently accurate flow rate estimates for initial responders in accidental oil discharges in submarine operations. The essence of our approach is based on tracking coherent features at the interface in the near field of immiscible turbulent jets. The software package, UCB_Plume, is ready to be used by the first responders for field implementation. We have tested the tool on submerged water and oil jets which are made visible using fluorescent dyes. We have been able to estimate the discharge rate within 20% accuracy. A high end WINDOWS laptop computer is suggested as the operating platform and a USB connected high speed, high resolution monochrome camera as the imaging device are sufficient for acquiring flow images under continuous unidirectional illumination and running the software in the field. Results are obtained over a matter of minutes.

  2. Rapid ammonia gas transport accounts for futile transmembrane cycling under NH3/NH4+ toxicity in plant roots.

    Coskun, Devrim; Britto, Dev T; Li, Mingyuan; Becker, Alexander; Kronzucker, Herbert J

    2013-12-01

    Futile transmembrane NH3/NH4(+) cycling in plant root cells, characterized by extremely rapid fluxes and high efflux to influx ratios, has been successfully linked to NH3/NH4(+) toxicity. Surprisingly, the fundamental question of which species of the conjugate pair (NH3 or NH4(+)) participates in such fluxes is unresolved. Using flux analyses with the short-lived radioisotope (13)N and electrophysiological, respiratory, and histochemical measurements, we show that futile cycling in roots of barley (Hordeum vulgare) seedlings is predominately of the gaseous NH3 species, rather than the NH4(+) ion. Influx of (13)NH3/(13)NH4(+), which exceeded 200 µmol g(-1) h(-1), was not commensurate with membrane depolarization or increases in root respiration, suggesting electroneutral NH3 transport. Influx followed Michaelis-Menten kinetics for NH3 (but not NH4(+)), as a function of external concentration (Km = 152 µm, Vmax = 205 µmol g(-1) h(-1)). Efflux of (13)NH3/(13)NH4(+) responded with a nearly identical Km. Pharmacological characterization of influx and efflux suggests mediation by aquaporins. Our study fundamentally revises the futile-cycling model by demonstrating that NH3 is the major permeating species across both plasmalemma and tonoplast of root cells under toxicity conditions.

  3. Rapid analysis of ethanol and water in commercial products using ionic liquid capillary gas chromatography with thermal conductivity detection and/or barrier discharge ionization detection.

    Weatherly, Choyce A; Woods, Ross M; Armstrong, Daniel W

    2014-02-26

    Analysis of ethanol and water in consumer products is important in a variety of processes and often is mandated by regulating agencies. A method for the simultaneous quantitation of ethanol and water that is simple, accurate, precise, rapid, and cost-effective is demonstrated. This approach requires no internal standard for the quantitation of both ethanol and water at any/all levels in commercial products. Ionic liquid based gas chromatography (GC) capillary columns are used to obtain a fast analysis with high selectivity and resolution of water and ethanol. Typical run times are just over 3 min. Examination of the response range of water and ethanol with GC, thermal conductivity detection (TCD), and barrier ionization detection (BID) is performed. Quantitation of both ethanol and water in consumer products is accomplished with both TCD and BID GC detectors using a nonlinear calibration. Validation of method accuracy is accomplished by using standard reference materials.

  4. Enhanced mechanical properties of tungsten inert gas welded AZ31 magnesium alloy joint using two-pass friction stir processing with rapid cooling

    Xu, Nan, E-mail: xunan@hhu.edu.cn; Bao, Yefeng

    2016-02-08

    In this study, tungsten inert gas (TIG) welded AZ31 magnesium alloy joint was subjected to two-pass rapid cooling friction stir processing (RC-FSP). The main results show that, two-pass RC-FSP causes the significant dissolution of the coarse eutectic β-Mg{sub 17}Al{sub 12} phase into the magnesium matrix and the remarkable grain refinement in the stir zone. The low-hardness region which frequently located at heat-affected zone was eliminated. The stir zone showed ultrafine grains of 3.1 μm, and exhibited a good combination of ultrahigh tensile strength of 284 MPa and large elongation of 7.1%. This work provides an effective strategy to enhance the strength of TIG welded magnesium alloy joint without ductility loss.

  5. Rapid screening of selective serotonin re-uptake inhibitors in urine samples using solid-phase microextraction gas chromatography-mass spectrometry.

    Salgado-Petinal, Carmen; Lamas, J Pablo; Garcia-Jares, Carmen; Llompart, Maria; Cela, Rafael

    2005-07-01

    In this paper a solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) method is proposed for a rapid analysis of some frequently prescribed selective serotonin re-uptake inhibitors (SSRI)-venlafaxine, fluvoxamine, mirtazapine, fluoxetine, citalopram, and sertraline-in urine samples. The SPME-based method enables simultaneous determination of the target SSRI after simple in-situ derivatization of some of the target compounds. Calibration curves in water and in urine were validated and statistically compared. This revealed the absence of matrix effect and, in consequence, the possibility of quantifying SSRI in urine samples by external water calibration. Intra-day and inter-day precision was satisfactory for all the target compounds (relative standard deviation, RSD, detection limits achieved were detected and tentatively identified.

  6. Enhanced mechanical properties of tungsten inert gas welded AZ31 magnesium alloy joint using two-pass friction stir processing with rapid cooling

    Xu, Nan; Bao, Yefeng

    2016-01-01

    In this study, tungsten inert gas (TIG) welded AZ31 magnesium alloy joint was subjected to two-pass rapid cooling friction stir processing (RC-FSP). The main results show that, two-pass RC-FSP causes the significant dissolution of the coarse eutectic β-Mg_1_7Al_1_2 phase into the magnesium matrix and the remarkable grain refinement in the stir zone. The low-hardness region which frequently located at heat-affected zone was eliminated. The stir zone showed ultrafine grains of 3.1 μm, and exhibited a good combination of ultrahigh tensile strength of 284 MPa and large elongation of 7.1%. This work provides an effective strategy to enhance the strength of TIG welded magnesium alloy joint without ductility loss.

  7. Coalbed gas desorption in canisters: Consumption of trapped atmospheric oxygen and implications for measured gas quality

    Jin, Hui; Schimmelmann, Arndt; Mastalerz, Maria; Pope, James; Moore, Tim A.

    2010-01-01

    Desorption canisters are routinely employed to quantify coalbed gas contents in coals. If purging with inert gas or water flooding is not used, entrapment of air with ∝ 78.08 vol.% nitrogen (N 2 ) in canisters during the loading of coal results in contamination by air and subsequent overestimates of N 2 in desorbed coalbed gas. Pure coalbed gas does not contain any elemental oxygen (O 2 ), whereas air contamination originally includes ∝ 20.95 vol.% O 2 and has a N 2 /O 2 volume ratio of ∝ 3.73. A correction for atmospheric N 2 is often attempted by quantifying O 2 in headspace gas and then proportionally subtracting atmospheric N 2 . However, this study shows that O 2 is not a conservative proxy for air contamination in desorption canisters. Time-series of gas chromatographic (GC) compositional data from several desorption experiments using high volatile bituminous coals from the Illinois Basin and a New Zealand subbituminous coal document that atmospheric O 2 was rapidly consumed, especially during the first 24 h. After about 2 weeks of desorption, the concentration of O 2 declined to near or below GC detection limits. Irreversible loss of O 2 in desorption canisters is caused by biological, chemical, and physical mechanisms. The use of O 2 as a proxy for air contamination is justified only immediately after loading of desorption canisters, but such rapid measurements preclude meaningful assessment of coalbed gas concentrations. With increasing time and progressive loss of O 2 , the use of O 2 content as a proxy for atmospheric N 2 results in overestimates of N 2 in desorbed coalbed gas. The indicated errors for nitrogen often range in hundreds of %. Such large analytical errors have a profound influence on market choices for CBM gas. An erroneously calculated N 2 content in CBM would not meet specifications for most pipeline-quality gas. (author)

  8. Amino-Functionalized Luminescent Metal-Organic Framework Test Paper for Rapid and Selective Sensing of SO2 Gas and Its Derivatives by Luminescence Turn-On Effect.

    Wang, Meng; Guo, Lin; Cao, Dapeng

    2018-03-06

    Rapid and selective sensing of sulfur dioxide (SO 2 ) gas has attracted more and more attention because SO 2 not only causes environmental pollution but also severely affects the health of human beings. Here we report an amino-functionalized luminescent metal-organic framework (MOF) material (i.e., MOF-5-NH 2 ) and further investigate its sensing property for SO 2 gas and its derivatives as a luminescent probe. The results indicate that the MOF-5-NH 2 probe can selectively and sensitively sense SO 2 derivatives (i.e., SO 3 2- ) in real time by a luminescence turn-on effect with a lower detection limit of 0.168 ppm and a response time of less than 15 s. Importantly, the luminescence turn-on phenomenon can be observed by the naked eye. We also assembled MOF-5-NH 2 into a test paper to achieve the aim of portable detection, and the lower-limit concentration of the test paper for sensing SO 2 in real time was found to be about 0.05 ppm. Moreover, MOF-5-NH 2 also shows good anti-interference ability, strong luminescence stability, and reusability, which means that this material is an excellent sensing candidate. The amino functionalization may also provide a modification strategy to design luminescent sensors for other atmospheric pollutants.

  9. Rapid actinide analysis method coupling liquid chromatography/ICP-MS and "9"0Sr gas proportional counter in post-accidental situation environmental samples

    Habibi, Azza

    2015-01-01

    The present study follows the Fukushima power plant accident and aimed to develop an analytical method to achieve, during an emergency situation, a rapid identification and quantification of alpha and beta emitters in environmental samples. The first step of this study allowed us to list the alpha and beta emitters which can be released in the environment in case of a nuclear accident. The second step aimed towards the development of a rapid analysis method to quantify 17 radionuclides of U, Th, Pu, Am, Np and Sr. The main objective was the automation of the radiochemical separation step and its coupling for the measurement. The separation is performed using columns containing extraction resins, namely TEVA, TRU and Sr. The measurement is performed using an ICP-MS (inductively coupled plasma mass spectrometry) and in some cases a gas proportional counter to quantify radiostrontium ("8"9Sr and "9"0Sr). Excellent figures of merit were obtained, off line, with water (tap, river and sea water) and solid matrices (soil and aerosol filters), after a micro-wave digestion or an alkaline fusion dissolution followed by a Ca_3(PO_4)_2 coprecipitation. The proposed analytical strategy showed yields between 70 % and 100 % and standard deviations between 5 % and 10 %. The newly developed separation method was then automated and coupled on-line to ICP-MS. The operating parameters were optimized using a design of experiments and the results were processed with Minitab. The optimized automated separation coupled on-line to the ICP-MS allows the rapid quantification, in 1.5 h per sample, of U, Th, Pu, Am, Np and Sr with detection limits gain as high as 20 times for artificial radionuclide. (author)

  10. The Separation of Hydrogen Tritium and Tritium Hydride by Gas Chromatography; Separation de l'hydrogene, du tritium et de l'hydrure de tritium par chromatographic en phase gazeuse; Razdelenie vodoroda, tritiya i gidrida tritiya posredstvom gazovoj khromatografii; Separacion del hidrogeno, tritio e hidruro de tritio por cromatografia de gases

    Smith, H A; Carter, Jr, E H [University of Tennessee, Knoxville, TN (United States)

    1962-01-15

    Now that successful separation of hydrogen, deuterium and hydrogen deuteride has been achieved by gas chromatography, similar studies are being made dealing with mixtures of hydrogen, tritium and tritium hydride. Since tritium is used in tracer quantities the usual katharometer cannot be employed for its detection. This difficulty has been overcome by providing immediately following the katharometer a vibrating reed electrometer equipped with a high resistance leak which allows continuous monitoring of the activity of any tritium or tritium hydride emerging from the column by means of synchronized recorders. Separation of such mixtures has been tested with columns packed with palladium on silica, silica, alumina, and alumina coated with chromium oxide or ferric oxide. No effective separation was obtained with the palladium on silica column. Good separation was achieved with the plain silica column where hydrogen was employed as the carrier gas, but helium failed to elute the isotopes. Satisfactory results were obtained with the coated, partially deactivated alumina packing when helium or neon was the carrier gas, but the best separation was found with a column packing of uncoated activated alumina. Calibration with helium-tritium mixtures of known activity plus equilibrated hydrogen-tritium mixtures also of known activity allows quantitative estimation of tritium and tritium hydride. (author) [French] La separation de l'hydrogene, du deuterium et du deuterure d'hydrogene par chromatographic en phase gazeuse ayant ete realisee, on procede maintenant a des etudes semblables sur des melanges d'hydrogene de tritium et d'hydrure de tritium. Comme le tritium n'est present qu'en quantites infimes, on ne peut utiliser le catharometre ordinaire pour le detecter. On a surmonte cette difficulte en faisant suivre le catharometre d'un electrometre a lame vibrante, muni d'une fuite haute resistance, qui permet de mesurer, a l'aide d'enregistreurs synchronises, l'activite de

  11. Recent advances in metal-organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis.

    Wang, Xuan; Ye, Nengsheng

    2017-12-01

    In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF- or COF-based solid-phase extraction (SPE), solid-phase microextraction (SPME), gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Supercritical Fluid Chromatographic Separation of Dimethylpolysiloxane Polymer

    Pyo, Dong Jin; Lim, Chang Hyun [Kangwon National University, Chuncheon (Korea, Republic of)

    2005-02-15

    Water was used as a polar modifier and a μ-porasil column as a saturator column. The μ-porasil column was inserted between the pump outlet and the injection valve. During the passage of the supercritical fluid mobile phase through the silica column, a polar modifier (water) can be dissolved in the pressurized supercritical fluid. Dimethylpolysiloxane polymer has been known as more polar polymer than polystyrene polymer. Dimethylpolysiloxane polymer has never been separated using water modified mobile phase. In this paper, using a μ-porasil column as a saturator column, excellent supercritical fluid chromatograms of dimethylpolysiloxane oligomers were obtained. The use of compressed (dense) gases and supercritical fluids as chromatographic mobile phases in conjunction with liquid chromatographic (LC)-type packed columns was first reported by Klesper et al. in 1962. During its relatively short history, supercritical fluid chromatography (SFC) has become an attractive alternative to GC and LC in certain industrially important applications. SFC gives the advantage of high efficiency and allows the analysis of nonvolatile or thermally labile mixtures.

  13. Supercritical Fluid Chromatographic Separation of Dimethylpolysiloxane Polymer

    Pyo, Dong Jin; Lim, Chang Hyun

    2005-01-01

    Water was used as a polar modifier and a μ-porasil column as a saturator column. The μ-porasil column was inserted between the pump outlet and the injection valve. During the passage of the supercritical fluid mobile phase through the silica column, a polar modifier (water) can be dissolved in the pressurized supercritical fluid. Dimethylpolysiloxane polymer has been known as more polar polymer than polystyrene polymer. Dimethylpolysiloxane polymer has never been separated using water modified mobile phase. In this paper, using a μ-porasil column as a saturator column, excellent supercritical fluid chromatograms of dimethylpolysiloxane oligomers were obtained. The use of compressed (dense) gases and supercritical fluids as chromatographic mobile phases in conjunction with liquid chromatographic (LC)-type packed columns was first reported by Klesper et al. in 1962. During its relatively short history, supercritical fluid chromatography (SFC) has become an attractive alternative to GC and LC in certain industrially important applications. SFC gives the advantage of high efficiency and allows the analysis of nonvolatile or thermally labile mixtures

  14. Ion chromatographic determination of Di-n-butyl phosphate in degraded organic solvent

    Velavendan, P.; Pandey, N.K.; Kamachi Mudali, U.; Natarajan, R.

    2011-01-01

    In the present work a method for the determination of Di-n-butyl phosphate in organic streams using Ion Chromatography technique is developed and described here. The method involves the separation of Di-n-butyl phosphate (DBP) from 30% TBP-NPH (Tri-n-butylphosphate diluted in Normal Paraffin Hydrocarbon) and uranium/nitric acid matrix by an extraction of DBP in alkaline medium and subsequent ion-exchange separation in ion chromatography column followed by suppressed conductivity detection. Direct determination of DBP in lean/loaded organic solvent will lead to in accurate determination of DBP due to organic interference. DBP is quantified to lower limit of 1 ppm with 3% RSD. The results obtained with ion chromatographic technique are compared with those obtained by standard gas chromatographic technique. The developed method is much faster and total analysis can be completed within two hours. (author)

  15. Chromatographic Determination of Toluene and its Metabolites in Urine for Toluene Exposure - A Review

    Mohamad Raizul Zinalibdin; Abdul Rahim Yacob; Mohd Marsin Sanagi

    2016-01-01

    The determinations of toluene and their metabolites in biological samples such as urine and blood allow the estimation of the degree of exposure to this chemical. Chromatographic methods and preliminary methods are now universally employed for this purpose. Preliminary color test methods are well established for qualitative determination of toluene and its metabolites. Mobile test kits using color test methods are a vast tool for screening urine samples but chromatographic methods are still needed for confirmation and quantitative analysis. Gas chromatography (GC) methods are well-adapted for the determination of toluene metabolite in urine, but these methods often require several pretreatment steps. Meanwhile, high performance liquid chromatography (HPLC) is becoming a powerful tool for the accurate and easy determination of toluene metabolites considering its decisive advantages for routine monitoring. Furthermore, recent development in HPLC could widen the usefulness of this method to solve the most complex analytical problems that could be encountered during the measurement. (author)

  16. Rapid gas chromatography with flame photometric detection of multiple organophosphorus pesticides in Salvia miltiorrhizae after ultrasonication assisted one-step extraction.

    Zhang, Shanshan; Liu, Xiaofei; Qin, Jia'an; Yang, Meihua; Zhao, Hongzheng; Wang, Yong; Guo, Weiying; Ma, Zhijie; Kong, Weijun

    2017-11-15

    A simple and rapid gas chromatography-flame photometric detection (GC-FPD) method was developed for the determination of 12 organophosphorus pesticides (OPPs) in Salvia miltiorrhizae by using ultrasonication assisted one-step extraction (USAE) without any clean-up steps. Some crucial parameters such as type of extraction solvent were optimized to improve the method performance for trace analysis. Any clean-up steps were negligent as no interferences were detected in the GC-FPD chromatograms for sensitive detection. Under the optimized conditions, limits of detection (LODs) and quantitation (LOQs) for all pesticides were in the range of 0.001-0.002mg/kg and 0.002-0.01mg/kg and 0.002-0.01mg/kg, respectively, which were all below the regulatory maximum residue limits suggested. RSDs for method precision (intra- and inter-day variations) were lower than 6.8% in approval with international regulations. Average recovery rates for all pesticides at three fortification levels (0.5, 1.0 and 5.0mg/kg) were in the range of 71.2-101.0% with relative standard deviations (RSDs) pesticide (dimethoate) out of the 12 targets was simultaneously detected in four samples at concentrations of 0.016-0.02mg/kg. Dichlorvos and omethoate were found in the same sample from Sichuan province at 0.004 and 0.027mg/kg, respectively. Malathion and monocrotophos were determined in the other two samples at 0.014 and 0.028mg/kg, respectively. All the positive samples were confirmed by LC-MS/MS. The simple, reliable and rapid USAE-GC-FPD method with many advantages over traditional techniques would be preferred for trace analysis of multiple pesticides in more complex matrices. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Radio Column Chromatographic Assay of H3-Labelled Substances

    Scharpenseel, H.W.; Menke, K.H.

    1962-01-01

    Combined radio-chromatographic investigations of H 3 -labelled substances are an integral part of the majority of biochemical experiments with H 3 -labelled compounds. H 3 -radio paper chromatography yields, in a scanner with a windowless flow counter, a counting efficiency of 0,5 -1,5%, depending largely on the thickness of the paper and the self-absorption of the labelled compound. The radio gas chromatography of tritiated compounds presents no major problem. Successful use is being made of a combination of a gas chromatograph with a flow ionization chamber and vibrating reed electrometer, a system originated by K. E. Wilzbach and P. Riessz, and improved by H. Dutton, L. Mason and L. Blair. Through the use of ''Teflon'' and silicone-rubber for the insulating parts of the flow ion chamber, it can be operated at close to 300 o C. Radio column chromatography with tritium holds little promise, when the column effluent is spread out as a shallow layer and slowly passes under a windowless flow counter or a scintillation counter, as was successfully tried with C 14 . Liquid scintillation spectrometry is likely to be the chosen method. Essentially, there are two different approaches feasible. These have been compared: 1. The column effluent is passed through a coil of plastic scintillator tubing, which is wound around a ''Plexiglas'' cylinder and placed in a bath of silicone oil in a light pipe with TiO 2 -reflector. Similarly, the HP-containing effluent can be directed through a test vial, filled - very much as in Steinberg's method - with plastic scintillator beads. These two approaches, that operate highly satisfactorily in the case of C 14 , offer low counting efficiencies of less than 1% for H 3 due to the unfavourable surface to volume ratio. 2. The column effluent is combined 1:30 with a mixture of 3:2 toluene/ethanol by the action of a magnet-vibrator before being assayed while passing through a K 40 -free glass - coiled between the analyser- and monitor

  18. Determination of insecticides malathion and lambda-cyhalothrin residues in zucchini by gas chromatography

    Lofty, Hayam M.; Abd El-Aleem, Abd El-Aziz A.; Monir, Hany H.

    2013-01-01

    A sensitive gas chromatographic method has been developed for the determination of malathion and lambda-cyhalothrin (λ-cyhalothrin) insecticide residues in zucchini. The developed method consists of extraction with acetone, purification and partitioning with methylene chloride, column chromatographic clean-up, and finally capillary gas chromatographic determination of the insecticides. The recoveries of method were greater than 90% and limit of determination was 0.001 ppm for both insecticide...

  19. An automatic injection system for rapid radiochemistry

    Nurmia, M.J.; Kreek, S.A.; Kadkhodayan, B.; Gregorich, K.E.; Lee, D.M.; Hoffman, D.C.

    1992-01-01

    A description is given of the Automated Injection System (AIS), a pneumatically actuated device for automated collection of nuclear reaction products from a He/KCl gas jet transport system. The AIS is used with the Automated Chemical Chromatographic Element Separation System; together these two devices facilitate completely automated separation procedures with improved speed and reproducibility

  20. Gas analysis during the chemical vapor deposition of carbon

    Lieberman, M.L.; Noles, G.T.

    1973-01-01

    Gas chromatographic analyses were performed during the chemical vapor deposition of carbon in both isothermal and thermal gradient systems. Such data offer insight into the gas phase processes which occur during deposition and the interrelations which exist between gas composition, deposition rate, and resultant structure of the deposit. The results support a carbon CVD model presented previously. The application of chromatographic analysis to research, development, and full-scale facilities is shown. (U.S.)

  1. Arsenic speciation in sulfidic waters: reconciling contradictory spectroscopic and chromatographic evidence.

    Planer-Friedrich, Britta; Suess, Elke; Scheinost, Andreas C; Wallschläger, Dirk

    2010-12-15

    In recent years, analytical methods have been developed that have demonstrated that soluble arsenic-sulfur species constitute a major fraction of dissolved arsenic in sulfidic waters. However, an intense debate is going on about the exact chemical nature of these compounds, since X-ray absorption spectroscopy (XAS) data generated at higher (mmol/L) concentrations suggest the presence of (oxy)thioarsenites in such waters, while ion chromatographic (IC) and mass spectroscopic data at lower (μmol/L to nmol/L) concentrations indicate the presence of (oxy)thioarsenates. In this contribution, we connect and explain these two apparently different types of results. We show by XAS that thioarsenites are the primary reaction products of arsenite and sulfide in geochemical model experiments in the complete absence of oxygen. However, thioarsenites are extremely unstable toward oxidation, and convert rapidly into thioarsenates when exposed to atmospheric oxygen, e.g., while waiting for analysis on the chromatographic autosampler. This problem can only be eliminated when the entire chromatographic process is conducted inside a glovebox. We also show that thioarsenites are unstable toward sample dilution, which is commonly employed prior to chromatographic analysis when ultrasensitive detectors like ICP-MS are used. This instability has two main reasons: if pH changes during dilution, then equilibria between individual arsenic-sulfur species rearrange rapidly due to their different stability regions within the pH range, and if pH is kept constant during dilution, then this changes the ratio between OH(-) and SH(-) in solution, which in turn shifts the underlying speciation equilibria. This problem is avoided by analyzing samples undiluted. Our studies show that thioarsenites appear as thioarsenates in IC analyses if oxygen is not excluded completely, and as arsenite if samples are diluted in alkaline anoxic medium. This also points out that thioarsenites are necessary

  2. Determination of insecticides malathion and lambda-cyhalothrin residues in zucchini by gas chromatography

    Hayam M. Lofty

    2013-12-01

    Full Text Available A sensitive gas chromatographic method has been developed for the determination of malathion and lambda-cyhalothrin (λ-cyhalothrin insecticide residues in zucchini. The developed method consists of extraction with acetone, purification and partitioning with methylene chloride, column chromatographic clean-up, and finally capillary gas chromatographic determination of the insecticides. The recoveries of method were greater than 90% and limit of determination was 0.001 ppm for both insecticides. The method was applied to determine residues and the rate of disappearance of malathion and λ-cyhalothrin from fruits of zucchini (open field treatment, 50 cc of Malason/Cormandel 57% EC (emulsifiable concentrate for 100 L of water, 20 cc of LAMBDA SUPER FOG 5% liquid for 100 L of water. The insecticide incorporated into the plants decreased rapidly with a half-life time around 0.77 day (18.5h for malathion and 4 days for λ-cyhalothrin. It is not recommended to use zucchini before 12 h of malathion application. For λ-cyhalothrin, the preharvest interval is 5 days. Four market samples were chosen from different regions from A.R.E. and all of them showed no residues of malathion or λ-cyhalothrin.

  3. A rapid assay for the simultaneous determination of nicotine, cocaine and metabolites in meconium using disposable pipette extraction and gas chromatography-mass spectrometry (GC-MS).

    Mozaner Bordin, Dayanne C; Alves, Marcela N R; Cabrices, Oscar G; de Campos, Eduardo G; De Martinis, Bruno Spinosa

    2014-01-01

    Drug abuse by pregnant women is considered a serious public health problem worldwide. Meconium is the first excretion in newborns and has been used as an alternative matrix to evaluate in utero drug exposure. Solid phase extraction (SPE) is widely employed to prepare and clean up samples in the field of forensic analysis. Most SPE products require large volumes of solvent, which culminates in longer sample processing times and increased cost per sample. Disposable pipette extraction (DPX) tips have been used as an alternative to traditional SPE cartridges. They combine efficient and rapid extraction with reduced solvent consumption. The purpose of this study was to develop and validate a method to determine nicotine, cotinine, cocaine, benzoylecgonine, cocaethylene and methyl ester anhydroecgonine in meconium using DPX and gas chromatography-mass spectrometry (GC-MS). Validation results indicated that extraction efficiency ranged 50-98%, accuracy 92-106%, intra-assay precision 4-12% and inter-assay precision 6-12%. Linear calibration curves resulted in R(2) values >0.99, limits of detection ranged from 2.5 to 15 ng/g and the limit of quantitation from 10 to 20 ng/g. The DPX-GC-MS method was shown to selectively analyze trace concentrations of drugs in meconium samples. Finally, the developed and validated method was applied to 50 meconium samples.

  4. Gas loop - continuous measurement of thermal and fast neutron fluxes; Boucle a gaz - mesure continue de flux de neutrons thermiques et rapides

    Droulers, Y; Pleyber, G; Sciers, P; Maurin, G [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1964-07-01

    The measurement method described in this report can be applied both to thermal and fast neutron fluxes. A description is given of two practical applications in each of these two domains. This method is particularly suitable for measurements carried out on 'loop' type equipment. The measurement of the relative flux variations are carried out with an accuracy of 5 per cent. The choice of the shape of the gas circuit leaves a considerable amount of liberty for the adaptation of the measurement circuit to the experimental conditions. (authors) [French] La methode de mesure defrite dans ce rapport s1 applique aussi bien au flux de neutrons thermiques, qu'au flux de neutrons rapides. On donne la description de deux realisations pratiques dans chacun de ces domaines. Cette methode est particulierement adaptee a des mesures effectuees sur des dispositifs du type 'boucle'. La mesure des variations relatives de flux se fait avec une precision de 5 pour cent. Le choix de la configuration du circuit gazeux donne une grande souplesse dans l'adaptation du circuit de mesure aux conditions experimentales. (auteurs)

  5. Rapid determination of caffeine in one drop of beverages and foods using drop-to-drop solvent microextraction with gas chromatography/mass spectrometry.

    Shrivas, Kamlesh; Wu, Hui-Fen

    2007-11-02

    A simple and rapid sample cleanup and preconcentration method for the quantitative determination of caffeine in one drop of beverages and foods by gas chromatography/mass spectrometry (GC/MS) has been proposed using drop-to-drop solvent microextraction (DDSME). The best optimum experimental conditions for DDSME were: chloroform as the extraction solvent, 5 min extraction time, 0.5 microL exposure volume of the extraction phase and no salt addition at room temperature. The optimized methodology exhibited good linearity between 0.05 and 5.0 microg/mL with correlation coefficient of 0.980. The relative standard deviation (RSD) and limits of detection (LOD) of the DDSME/GC/MS method were 4.4% and 4.0 ng/mL, respectively. Relative recovery of caffeine in beverages and foods were found to be 96.6-101%, which showing good reliability of this method. This DDSME excludes the major disadvantages of conventional method of caffeine extraction, like large amount of organic solvent and sample consumption and long sample pre-treatment process. So, this approach proves that the DDSME/GC/MS technique can be applied as a simple, fast and feasible diagnosis tool for environmental, food and biological application for extremely small amount of real sample analysis.

  6. Rapid and selective determination of free chlorine in aqueous solution using electrophilic addition to styrene by gas chromatography/mass spectrometry.

    Wakigawa, Kengo; Gohda, Akinaga; Fukushima, Sunao; Mori, Takeshi; Niidome, Takuro; Katayama, Yoshiki

    2013-01-15

    We developed a rapid and selective method for determination of free chlorine in aqueous solution by gas chromatography/mass spectrometry for the first time. Free chlorine was converted to styrene chlorohydrin using electrophilic addition to styrene in sodium acetate buffer solution (pH 5). The chlorine derivative obtained was extracted with chloroform, and then analyzed by GC/MS. The calibration curve showed good linearity from 0.2-100 μg/mL (as available chlorine). The detection limit was 0.1 μg/mL, and the intra- and interday accuracy were measured at concentrations of 10, 50, and 75 μg/mL to be -1.3 to 6.9% (intraday) and 3.8-8.0% (interday) as % Bias. The precision was between 1.4 and 4.5% as % RSD. These results indicate that this method is a superior technique for the identification of free chlorine. This method was successfully applied to quantification in commercial samples and in samples of a criminal case. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. (E-2-Nonenal determination in brazilian beers using headspace solid-phase microextraction and gas chromatographic coupled mass spectrometry (HS-SPME-GC-MS Determinação de (E-2-nonenal em cervejas brasileiras utilizando microextração em fase sólida do headspace e cromatografia gasosa acoplada a espectrometria de massas

    Rodrigo Scherer

    2010-05-01

    Full Text Available (E-2-nonenal is considered an important off-flavor of beer, related to the flavor of beer staling. In this study, a new method for determination of (E-2-nonenal in beer using headspace solid-phase microextraction and gas chromatographic coupled mass spectrometry (HS-SPME-GC-MS was developed and applied in Brazilian beer samples. The extractions were carried out in CAR-PDMS (carboxen-polydimethylsiloxane fiber and the best results were found with 15 minutes of equilibrium and 90 minutes of extraction at 50 °C. The method was linear in the range from 0.02 to 4.0 μg.L-1 with correlation coefficient of 0.9994. The limits of detection and quantification were 0.01 and 0.02 μg.L-1, respectively. 96.5% of recovery and 4% precision (RSD were obtained in the fortification of beer samples with 2.0 μg.L-1 of (E-2-nonenal. The developed method proved to be simple, efficient and highly sensitive to the determination of this analyte being easily applied in the quality control of the brewery. (E-2-nonenal was found in all beer samples analyzed with levels between 0.17 and 0.42 μg.L-1.O (E-2-nonenal é considerado um importante off-flavor da cerveja, sendo relacionado ao sabor de cerveja envelhecida. Neste estudo, um novo método para determinação de (E-2-nonenal em cerveja usando microextração em fase sólida do headspace e cromatografia a gás acoplada à espectrometria de massa (HS-SPME-GC-MS foi desenvolvido e aplicado em amostras de cerveja brasileira. As extrações foram realizadas utilizando a fibra CAR/PDMS (carboxen/polidimetilsiloxano, com 15 minutos de tempo de equilíbrio e 90 minutos de exposição da fibra a 50 °C. O método foi linear na faixa de 0,02 e 4,0 μg.L-1, com coeficiente de correlação de 0,9994. Os limites de detecção e quantificação foram 0,01 e 0,02 μg.L-1, respectivamente. Foram obtidos 96,5% de recuperação e 4% de variação entre replicatas de amostras de cerveja fortificadas com 2,0 μg.L-1 de (E-2-nonenal. O m

  8. Probabilistic peak detection for first-order chromatographic data

    Lopatka, M.; Vivó-Truyols, G.; Sjerps, M.J.

    2014-01-01

    We present a novel algorithm for probabilistic peak detection in first-order chromatographic data. Unlike conventional methods that deliver a binary answer pertaining to the expected presence or absence of a chromatographic peak, our method calculates the probability of a point being affected by

  9. Rapid determination of benzene derivatives in water samples by trace volume solvent DLLME prior to GC-FID

    Diao, Chun Peng; Wei, Chao Hai; Feng, Chun Hua [South China Univ. of Technology, Guangzhou Higher Education Mega Center (China). College of Environmental Science and Engineering; Guangdong Regular Higher Education Institutions, Guangzhou (China). Key Lab. of Environmental Protection and Eco-Remediation

    2012-05-15

    An inexpensive, simple and environmentally friendly method based on dispersive liquid liquid microextraction (DLLME) for rapid determination of benzene derivatives in water samples was proposed. A significant improvement of DLLME procedure was achieved. Trace volume ethyl acetate (60 {mu}L) was exploited as dispersion solvent instead of common ones such as methanol and acetone, the volume of which was more than 0.5 mL, and the organic solvent required in DLLME was reduced to a great extent. Only 83-{mu}L organic solvent was consumed in the whole analytic process and the preconcentration procedure was less than 10 min. The advantageous approach coupled with gas chromatograph-flame ionization detector was proposed for the rapid determination of benzene, toluene, ethylbenzene and xylene isomers in water samples. Results showed that the proposed approach was an efficient method for rapid determination of benzene derivatives in aqueous samples. (orig.)

  10. New extraction chromatographic material for rhenium separation

    Lucanikova, M.; Czech Technical University, Prague; Kucera, J.; Czech Technical University, Prague; Sebesta, F.

    2008-01-01

    Three types of the extraction chromatographic materials, composed from Aliquat R 336 deposited in the polyacrylonitrile (PAN) beads and prepared by different procedures, were compared for extraction of rhenium. The best properties were exhibited when the solid extractant was prepared by impregnation of the ready-made PAN beads. Solid extractant prepared by direct coagulation of the beads from the suspension of Aliquat R 336 in solution of PAN in nitric acid differs only by lower capacity in dynamic conditions. Material prepared from the PAN solution in dimethylsulfoxide was the worst because Aliquat R 336 was washed out from the beads during coagulation of the polymer and the extraction capacity was low. As it is shown, the first two solid extractants are fully comparable with the commercial TEVA Resin. (author)

  11. Aligning of single and multiple wavelength chromatographic

    Nielsen, Niels-Peter Vest; Carstensen, Jens Michael; Smedsgaard, Jørn

    1998-01-01

    optimised warping (COW) using two input parameters which can be estimated from the observed peak width. COW is demonstrated on constructed single trace chromatograms and on single and multiple wavelength chromatograms obtained from HPLC diode detection analyses of fungal extractsA copy of the C program......The use of chemometric data processing is becoming an important part of modern chromatography. Most chemometric analyses are performed on reduced data sets using areas of selected peaks detected in the chromatograms, which means a loss of data and introduces the problem of extracting peak data from...... to utilise the entire data matrix or rely on peak detection, thus having the same limitations as the commonly used chemometric procedures. The method presented uses the entire chromatographic data matrices and does not require any preprocessing e.g., peak detection. It relies on piecewise linear correlation...

  12. Brazilian organic sugarcane spirits: Physicochemical and chromatographic profile

    Felipe Cimino Duarte

    Full Text Available ABSTRACT There has been a growing demand for products from organic agriculture for the food market. Brazil leads the production of sugarcane spirits and produces about 1.6 billion liters/year. New technologies have been sought throughout the supply chain to improve production, and organic raw material has been used in the production of sugar cane for the production of beverages. This study aimed to define the physicochemical and chromatographic profiles of eleven organic sugarcane spirits samples from various Brazilian states. The secondary components and contaminants were identified and quantified through physicochemical analyses, HPLC and gas chromatography (GC. A significant percentage of the organic sugarcane spirits samples contained concentrations of components that were above the limits required by the Ministry of Agriculture, Livestock and Provisioning (MAPA, specifically the esters (18.20%, copper and dry extract (9.10%. This contamination is caused by bad conditions employed during the production process, which are not in compliance with the good manufacturing practices determined and legislated by Brazilian law.

  13. Liquid chromatographic determination of sennosides in Cassia angustifolia leaves.

    Srivastava, Alpuna; Pandey, Richa; Verma, Ram K; Gupta, Madan M

    2006-01-01

    A simple liquid chromatographic method was developed for the determination of sennosides B and A in leaves of Cassia angustifolia. These compounds were extracted from leaves with a mixture of methanol-water (70 + 30, v/v) after defatting with hexane. Analyte separation and quantitation were achieved by gradient reversed-phase liquid chromatography and UV absorbance at 270 nm using a photodiode array detector. The method involves the use of an RP-18 Lichrocart reversed-phase column (5 microm, 125 x 4.0 mm id) and a binary gradient mobile-phase profile. The various other aspects of analysis, namely, peak purity, similarity, recovery, repeatability, and robustness, were validated. Average recoveries of 98.5 and 98.6%, with a coefficient of variation of 0.8 and 0.3%, were obtained by spiking sample solution with 3 different concentration solutions of standards (60, 100, and 200 microg/mL). Detection limits were 10 microg/mL for sennoside B and 35 microg/mL for sennoside A, present in the sample solution. The quantitation limits were 28 and 100 microg/mL. The analytical method was applied to a large number of senna leaf samples. The new method provides a reliable tool for rapid screening of C. angustifolia samples in large numbers, which is needed in breeding/genetic engineering and genetic mapping experiments.

  14. A Novel UAS Rapid Deployment Platform for Targeted Gas Sampling and Meteorological Soundings at Altitudes up to 2,700 masl

    Thomas, Rick M.; Greatwood, Colin; Richardson, Tom; Freer, Jim; MacKenzie, Rob; Brownlow, Rebecca; Lowry, David; Fisher, Rebecca E.; France, James; Nisbet, Euan G.

    2015-04-01

    This research project has developed Unmanned Aerial System (UAS) technologies for intelligent targeting and collection of atmospheric gas samples to investigate the so-called Southern Tropical Methane Anomaly, for which it is necessary to sample air below and above the trade-wind inversion. Air parcels above and below the South Atlantic trade-wind inversion can have markedly different trajectories and, hence, encounter very different methane source regions. The system is intelligent in that high resolution temperature and humidity sensors linked to the ground station characterise the atmospheric profile on the upward flight to ensure the platform targets the appropriate sample elevations on the downward trajectory. This capability has been proven to an altitude of 2,700 metres above sea level (masl; ca. 700 mb) at Ascension Island in the South Atlantic and shown that rapid and repeat deployment and sample collection is achievable. Three novel eight motor multirotor UAS (or octocopter) platforms were developed at Bristol Robotics Laboratory (BRL) using primarily off -the-shelf components with a custom-built main fuselage. Gas sampling and atmospheric sensor systems were designed by the University of Birmingham. Our paper explores the capability of this UAS and provides some initial results from the air sampling campaign conducted in September 2014. Thirty-eight sampling flights were conducted over 12 days and the resulting 47 samples analysed for their CH4 concentration using the high-precision Picarro Cavity Ring Down Spectrometer already installed at Ascension Island. A subset of samples were sent for δ13CCH4 analysis in Egham, UK. The flights were conducted up to an altitude of 2,700m with 2,000m being typical. There were no major incidents although variable zero and high wind situations above the trade wind inversion (typically at 1,800m) both presented unique challenges and required careful flight planning strategies and in flight trajectory changes. As a

  15. Gas chromatography at the Tritium Laboratory Karlsruhe

    Laesser, R.; Gruenhagen, S.

    2003-08-01

    Among the analytical techniques (mass spectrometry, laser Raman spectroscopy, gas chromatography, use of ionisation chambers) employed at the Tritium Laboratory Karlsruhe (TLK), gas chromatography plays a prominent role. The main reasons for that are the simplicity of the gas chromatographic separation process, the small space required for the equipment, the low investment costs in comparison to other methods, the robustness of the equipment, the simple and straightforward analysis and the fact that all gas species of interest (with the exception of water) can easily be detected by gas chromatographic means. The conventional gas chromatographs GC1 and GC2 used in the Tritium Measurement Techniques (TMT) System of the TLK and the gas chromatograph GC3 of the experiment CAPER are presented in detail, by discussing their flow diagrams, their major components, the chromatograms measured by means of various detectors, shortcomings and possible improvements. One of the main disadvantages of the conventional gas chromatography is the long retention times required for the analysis of hydrogen gas mixtures. To overcome this disadvantage, micro gas chromatography for hydrogen analysis was developed. Reduction of the retention times by one order of magnitude was achieved. (orig.)

  16. Rapid analysis of Fructus forsythiae essential oil by ionic liquids-assisted microwave distillation coupled with headspace single-drop microextraction followed by gas chromatography–mass spectrometry

    Jiao, Jiao; Ma, Dan-Hui; Gai, Qing-Yan; Wang, Wei; Luo, Meng; Fu, Yu-Jie; Ma, Wei

    2013-01-01

    Graphical abstract: -- Highlights: •A new ILAMD-HS-SDME method is developed for the microextraction of essential oil. •ILs used as destruction agent of plant cell walls and microwave absorption medium. •Parameters affecting the extraction efficiency are optimized by Box–Behnken design. •Procedure benefits: similar constituents, shorter duration and smaller sample amount. •ILAMD-HS-SDME followed by GC–MS is a promising technique in analytical fields. -- Abstract: A rapid, green and effective miniaturized sample preparation and analytical technique, i.e. ionic liquids-assisted microwave distillation coupled with headspace single-drop microextraction (ILAMD-HS-SDME) followed by gas chromatography–mass spectrometry (GC–MS) was developed for the analysis of essential oil (EO) in Fructus forsythiae. In this work, ionic liquids (ILs) were not only used as the absorption medium of microwave irradiation but also as the destruction agent of plant cell walls. 1-Ethyl-3-methylimidazolium acetate ([C 2 mim]OAc) was chosen as the optimal ILs. Moreover, n-heptadecane (2.0 μL) was selected as the appropriate suspended solvent for the extraction and concentration of EO. Extraction conditions of the proposed method were optimized using the relative peak area of EO constituents as the index, and the optimal operational parameters were obtained as follows: irradiation power (300 W), sample mass (0.7 g), mass ratio of ILs to sample (2.4), temperature (78 °C) and time (3.4 min). In comparison to previous reports, the proposed method was faster and required smaller sample amount but could equally monitor all EO constituents with no significant differences

  17. Magnetic covalent triazine framework for rapid extraction of phthalate esters in plastic packaging materials followed by gas chromatography-flame ionization detection.

    Yan, Zijun; He, Man; Chen, Beibei; Gui, Bo; Wang, Cheng; Hu, Bin

    2017-11-24

    Covalent triazine frameworks (CTFs), featuring with high surface area, good thermal, chemical and mechanical stability, are good adsorbents in sample pretreatment. Herein, magnetic CTFs/Ni composite was prepared by in situ reduction of nickel ions on CTFs matrix with a solvothermal method. The prepared CTFs/Ni composite exhibited good preparation reproducibility, high chemical stability, and high extraction efficiency for targeted phthalate esters (PAEs) due to π-π interaction and hydrophobic effect. The porous structure of CTFs/Ni composite benefited the fast transfer of target PAEs from aqueous solution to the adsorbents, and the integrated magnetism contributed to the rapid separation of adsorbents from sample and elution solution. Based on it, a novel method of magnetic solid phase extraction (MSPE) combined with gas chromatography-flame ionization detector (GC-FID) was developed for the analysis of PAEs including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), benzyl butyl phthalate (BBP), di-2-ethylhexl phthalate (DEHP), and di-n-octyl phthalate (DNOP) in plastic packaging materials. Under the optimal experimental conditions, the limits of detection (LODs, S/N=3) for six PAEs were found to be in the range of 0.024-0.085mg/kg. The linear range was 0.32-16mg/kg for DMP, DEP, 0.08-80mg/kg for DBP, 0.16-32mg/kg for BBP, DEHP, and 0.32-32mg/kg for DNOP, respectively. The enrichment factors ranged from 59 to 88-fold (theoretical enrichment factor was 133-fold). The proposed method was successfully applied to the analysis of PAEs in various plastic packaging materials with recoveries in the range of 70.6-119% for the spiked samples. This method is characterized with short operation time, high sensitivity, low consumption of harmful organic solvents and can be extended to the analysis of other trace aromatic compounds. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Rapid analysis of Fructus forsythiae essential oil by ionic liquids-assisted microwave distillation coupled with headspace single-drop microextraction followed by gas chromatography–mass spectrometry

    Jiao, Jiao [State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin 150040 (China); Ma, Dan-Hui [College of Life Sciences, Northeast Forestry University, Harbin 150040 (China); Gai, Qing-Yan; Wang, Wei; Luo, Meng [State Engineering Laboratory of Bio-Resource Eco-Utilization, Northeast Forestry University, Harbin 150040 (China); Fu, Yu-Jie, E-mail: yujie_fu2002@yahoo.com [State Engineering Laboratory of Bio-Resource Eco-Utilization, Northeast Forestry University, Harbin 150040 (China); Ma, Wei, E-mail: mawei@hljucm.net [State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin 150040 (China); School of Pharmaceutical, Heilongjiang University of Chinese Medicine, Harbin 150040 (China)

    2013-12-04

    Graphical abstract: -- Highlights: •A new ILAMD-HS-SDME method is developed for the microextraction of essential oil. •ILs used as destruction agent of plant cell walls and microwave absorption medium. •Parameters affecting the extraction efficiency are optimized by Box–Behnken design. •Procedure benefits: similar constituents, shorter duration and smaller sample amount. •ILAMD-HS-SDME followed by GC–MS is a promising technique in analytical fields. -- Abstract: A rapid, green and effective miniaturized sample preparation and analytical technique, i.e. ionic liquids-assisted microwave distillation coupled with headspace single-drop microextraction (ILAMD-HS-SDME) followed by gas chromatography–mass spectrometry (GC–MS) was developed for the analysis of essential oil (EO) in Fructus forsythiae. In this work, ionic liquids (ILs) were not only used as the absorption medium of microwave irradiation but also as the destruction agent of plant cell walls. 1-Ethyl-3-methylimidazolium acetate ([C{sub 2}mim]OAc) was chosen as the optimal ILs. Moreover, n-heptadecane (2.0 μL) was selected as the appropriate suspended solvent for the extraction and concentration of EO. Extraction conditions of the proposed method were optimized using the relative peak area of EO constituents as the index, and the optimal operational parameters were obtained as follows: irradiation power (300 W), sample mass (0.7 g), mass ratio of ILs to sample (2.4), temperature (78 °C) and time (3.4 min). In comparison to previous reports, the proposed method was faster and required smaller sample amount but could equally monitor all EO constituents with no significant differences.

  19. Study of gas-solid contact in an ultra-rapid reactor for cumene catalytic cracking; Etude du contact gaz-solide dans un reacteur a co-courant descendant par la mise en oeuvre du craquage catalytique du cumene

    Bayle, J

    1996-11-05

    Few studies have been carried out on the notion of gas-solid contact in ultra-rapid reactors. Both gas and solid move in the reactor and the contact can be directly estimated when using a chemical reaction such as cumene cracking. It`s a pure and light feedstock whose kinetics can be determined in a fixed bed. The study was carried out on a downflow ultra-rapid reactor (ID = 20 mm, length = 1 m) at the University of Western Ontario. It proved that the quench and the ultra-rapid separation of gas and solid must be carefully designed in the pilot plant. Cumene conversion dropped when reducing gas-solid contact, which led to push the temperature over 550 deg. C and increase the cat/oil ratio at 25 working at solid mass fluxes below 85 kg/m{sup 2}.s. Change of selectivity at very short residence time were also observed due to deactivation effects. Experiments made by Roques (1994) with phosphorescent pigments on the Residence Time Distribution of solids gave Hydrodynamic data on a cold flow copy of the pilot plant. Experiments made on packed bed gave kinetic data on the cracking of cumene. These data were combined to optimize a mono dimensional plug flow model for cumene cracking. (author)

  20. Infrared spectrophotometry, a rapid and effective tool for characterization of direct distillation naphthas

    Baldrich Ferrer, Carlos A; Novoa Mantilla, Luz Angela

    2005-01-01

    The characterization of naphtha obtained by direct distillation of medium and heavy crude oils is often limited by the low yield of these fractions. Gas chromatography is a technique that allows a complete determination of the chemical composition of this fraction. However, the prediction of properties such as octane rating and RVP from chromatographic data is a difficult task because there are not adequate models to predict the interaction of the different components, and particularly in the case of heavier fractions, there are some problems for the complete separation of components under the gas chromatographic conditions. The IR technology constitutes a rapid and effective tool to predict several properties of naphtha from the correlation of the spectrum in the infrared area and the properties. In this study, prediction models were developed in a Petrospec Cetane 2000 analyzer, in order to predict in a fast and simple way, the density, the antiknock index and the aromatic content of straight run naphtha obtained in a standard crude oil distillation unit. The equipment used was designed in the factory for the exclusive characterization of medium distillation and not for lighter fractions therefore this work constitutes an innovation given the extensive applications of this type of analyzers

  1. Chemometric approach for development, optimization, and validation of different chromatographic methods for separation of opium alkaloids.

    Acevska, J; Stefkov, G; Petkovska, R; Kulevanova, S; Dimitrovska, A

    2012-05-01

    The excessive and continuously growing interest in the simultaneous determination of poppy alkaloids imposes the development and optimization of convenient high-throughput methods for the assessment of the qualitative and quantitative profile of alkaloids in poppy straw. Systematic optimization of two chromatographic methods (gas chromatography (GC)/flame ionization detector (FID)/mass spectrometry (MS) and reversed-phase (RP)-high-performance liquid chromatography (HPLC)/diode array detector (DAD)) for the separation of alkaloids from Papaver somniferum L. (Papaveraceae) was carried out. The effects of various conditions on the predefined chromatographic descriptors were investigated using chemometrics. A full factorial linear design of experiments for determining the relationship between chromatographic conditions and the retention behavior of the analytes was used. Central composite circumscribed design was utilized for the final method optimization. By conducting the optimization of the methods in very rational manner, a great deal of excessive and unproductive laboratory research work was avoided. The developed chromatographic methods were validated and compared in line with the resolving power, sensitivity, accuracy, speed, cost, ecological aspects, and compatibility with the poppy straw extraction procedure. The separation of the opium alkaloids using the GC/FID/MS method was achieved within 10 min, avoiding any derivatization step. This method has a stronger resolving power, shorter analysis time, better cost/effectiveness factor than the RP-HPLC/DAD method and is in line with the "green trend" of the analysis. The RP-HPLC/DAD method on the other hand displayed better sensitivity for all tested alkaloids. The proposed methods provide both fast screening and an accurate content assessment of the six alkaloids in the poppy samples obtained from the selection program of Papaver strains.

  2. Chromatographic Separations of Enantiomers and Underivatized Oligosaccharides

    Liu, Ying [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    My graduate research has focused on separation science and bioanalytical analysis, which emphasized in method development. It includes three major areas: enantiomeric separations using high performance liquid chromatography (HPLC), Super/subcritical fluid chromatography (SFC), and capillary electrophoresis (CE); drug-protein binding behavior studies using CE; and carbohydrate analysis using liquid chromatograph-electrospray ionization mass spectrometry (LC-ESI-MS). Enantiomeric separations continue to be extremely important in the pharmaceutical industry. An in-depth evaluation of the enantiomeric separation capabilities of macrocyclic glycopeptides CSPs with SFC mobile phases was investigated using a set of over 100 chiral compounds. It was found that the macrocyclic based CSPs were able to separate enantiomers of various compounds with different polarities and functionalities. Seventy percent of all separations were achieved in less than 4 min due to the high flow rate (4.0 ml/min) that can be used in SFC. Drug-protein binding is an important process in determining the activity and fate of a drug once it enters the body. Two drug/protein systems have been studied using frontal analysis CE method. More sensitive fluorescence detection was introduced in this assay, which overcame the problem of low sensitivity that is common when using UV detection for drug-protein studies. In addition, the first usage of an argon ion laser with 257 nm beam coupled with CCD camera as a frontal analysis detection method enabled the simultaneous observation of drug fluorescence as well as the protein fluorescence. LC-ESI-MS was used for the separation and characterization of underivatized oligosaccharide mixtures. With the limits of detection as low as 50 picograms, all individual components of oligosaccharide mixtures (up to 11 glucose-units long) were baseline resolved on a Cyclobond I 2000 column and detected using ESI-MS. This system is characterized by high chromatographic

  3. Chromatographic Separations of Enantiomers and Underivatized Oligosaccharides

    Ying Liu

    2004-01-01

    My graduate research has focused on separation science and bioanalytical analysis, which emphasized in method development. It includes three major areas: enantiomeric separations using high performance liquid chromatography (HPLC), Super/subcritical fluid chromatography (SFC), and capillary electrophoresis (CE); drug-protein binding behavior studies using CE; and carbohydrate analysis using liquid chromatograph-electrospray ionization mass spectrometry (LC-ESI-MS). Enantiomeric separations continue to be extremely important in the pharmaceutical industry. An in-depth evaluation of the enantiomeric separation capabilities of macrocyclic glycopeptides CSPs with SFC mobile phases was investigated using a set of over 100 chiral compounds. It was found that the macrocyclic based CSPs were able to separate enantiomers of various compounds with different polarities and functionalities. Seventy percent of all separations were achieved in less than 4 min due to the high flow rate (4.0 ml/min) that can be used in SFC. Drug-protein binding is an important process in determining the activity and fate of a drug once it enters the body. Two drug/protein systems have been studied using frontal analysis CE method. More sensitive fluorescence detection was introduced in this assay, which overcame the problem of low sensitivity that is common when using UV detection for drug-protein studies. In addition, the first usage of an argon ion laser with 257 nm beam coupled with CCD camera as a frontal analysis detection method enabled the simultaneous observation of drug fluorescence as well as the protein fluorescence. LC-ESI-MS was used for the separation and characterization of underivatized oligosaccharide mixtures. With the limits of detection as low as 50 picograms, all individual components of oligosaccharide mixtures (up to 11 glucose-units long) were baseline resolved on a Cyclobond I 2000 column and detected using ESI-MS. This system is characterized by high chromatographic

  4. Chromatographic air analyser microsystem for the selective and sensitive detection of atmospheric pollutants

    Sanchez, Jean-Baptiste; Lahlou, Houda; Mohsen, Yehya; Berger, Franck; Vilanova, Xavier; Correig, Xavier

    2011-01-01

    The development of industry and automotive trafic produces Volatile Organic Compounds (VOCs) whose toxicity can affect seriously human health and environment. The level of those contaminants in air must be as low as possible. In this context, there is a need for in situ systems that could monitor selectively the concentration of these compounds. The aim of this study is to demonstrate the efficiency of a system build with a pre-concentrator, a chromatographic micro-column and a tin oxide-based gas sensor for the selective and sensitive detection of atmospheric pollutants. In particular, this study is focused on the selective detection of benzene and 1,3 butadiene.

  5. Chromatographic methods of the measurements of the chloride compounds in troposphere and stratosphere

    Lasa, J.; Rosiek, J.

    1992-01-01

    The paper contains a description of various chromatographic techniques used for the analysis of the tropospheric techniques used for the analysis of the tropospheric and stratospheric halogenated compounds. The types of the column packings used for separation of halogenated compounds are described. Model chromatograms illustrating the separation of halogenated compounds are presented. The methods of the air sampling and injection for the packed and capillary columns were described. The methods of the preparation of gas calibration mixtures are presented. Operational conditions for electron capture detector used by the authors of quoted paper are also given. (author). 66 refs, 29 figs, 13 tabs

  6. Possibilities of gas-phase radio-chromatography application to permanent-gas analysis

    Dupuis, M.C.; Charrier, G.; Alba, C.; Massimino, D.

    1970-01-01

    The gas-phase radio-chromatography technique has been applied to the rapid analysis of permanent gases (H 2 , O 2 , N 2 , A, Kr, Xe, CO, CH 4 ) labelled with radioactive indicators ( 3 H, 37 A, 85 Kr, 133 Xe). After calibration, the components of such a mixture can be identified and their concentrations measured in less than two hours, using a sample volume of from 0.1 to 10 cm 3 . The minimum detectable activity is of the order of 10 -4 μC for each radioactive isotope. The measurements are reproducible to about 2 to 3 per cent. This work has been mainly concerned with the influence of parameters affecting the response of the radioactivity detector (ionization chamber or gas flow proportional counter). The method has very numerous applications both theoretically, for the study of chromatographic phenomena under ideal conditions (infinitesimal concentrations made possible by the use of radioactive tracers), and practically, for rapid and accurate radiochemical analysis of radioactive gas mixtures. (authors) [fr

  7. Single-column extraction chromatographic separation of U, Pu, Np and Am

    Morgenstern, A.; Apostolidis, C.; Carlos-Marquez, R.; Mayer, K.; Molinet, R. [Commission of the European Communities, Karlsruhe (Germany). European Inst. for Transuranium Elements

    2002-07-01

    A rapid, single-column extraction chromatographic method using commercially available UTEVA resin has been developed for the separation of uranium, plutonium, neptunium and americium. The method yields recoveries superior to 90% and allows direct loading of separated fractions on filaments for subsequent analysis by thermal ionization mass spectrometry. The use of reagents compatible with robotized equipment allows automation of the separation process for routine analysis of nuclear materials. The redox reactions between plutonium, neptunium and hydrogen peroxide involved in the separation process were studied by UV/Vis/NIR absorption spectroscopy. (orig.)

  8. Chromatographic quality control procedures for /sup 99m/Tc-diagnostic agents

    Marinelli, M.; Pozzato, R.; Garuti, P.; Zucchini, G.L.

    1986-01-01

    The purpose of this work was to experiment simple and rapid chromatographic systems, based on paper and thin-layer techniques, to test the radiochemical purity of some common /sup 99m/Tc diagnostic agents, and select those systems able to prevent the anomalies due to oxidation and artifact production. The agents were examined under conditions which usually bring about the above mentioned anomalies, then the results were compared with those obtained under controlled conditions. Quali- and quantitative detection of the activity present on the chromatograms was carried out using the equipment available in nuclear medicine departments

  9. High-pressure liquid chromatographic analysis of pramoxine hydrochloride in high lipoid aerosol foam dosage form.

    Weinberger, R; Mann, B; Posluszny, J

    1980-04-01

    A rapid and quantitative method for the determination of pramoxine hydrochloride by high-pressure liquid chromatography is presented. The drug is extracted as the salt from a preparation with a high lipoid composition by partitioning it to the aqueous phase of an ether-methanol-water-acetic acid system. The extract is chromatographed on an octadecylsilane bonded packing with a methanol-water-acetic acid-methanesulfonic acid mobile phase. The time required for each separation is approximately 6 min. Analytical recoveries of 100.4 +/- 1.5% were obtained.

  10. Method for chromatographically recovering scandium and yttrium

    Snyder, T.S.; Stoltz, R.A.

    1991-01-01

    This paper describes a method for chromatographically recovering scandium and yttrium from the residue of a sand chlorinator. It comprises: providing a residue from a sand chlorinator, the residue containing scandium, yttrium, sodium, calcium and at least one radioactive metal of the group consisting of radium, thorium and uranium; digesting the residue with an acid to produce an aqueous liquid containing scandium, yttrium, sodium, calcium and at least one radioactive metal of the group consisting of radium, thorium and uranium; feeding the metal containing liquid through a cation exchanger; eluding the cation exchanger with an acid eluant to to produce: a first eluate containing at least half of the total weight of the calcium and sodium in the feed liquid; a second eluate containing at least half of the total weight of the one or more radioactive metals in the feed liquid; a third eluate containing at least half of the yttrium in the feed liquid, and a fourth eluate containing at least half of the weight of the scandium in the feed liquid

  11. Chromatographic separation of low-temperature tar. Part II

    Terres, E; Gebert, F; Huelsemann, H; Petereit, H; Toepsch, H; Ruppert, W

    1955-01-01

    Chromatographic methods and apparatus are discussed. The Folin-Denis reagent (Na tungstate molybdate in H/sub 3/PO/sub 4/) is used for developing paper chromatograms of phenol mixtures. Other reagents are given.

  12. Long-term optimization of the transport sector to address greenhouse gas reduction targets under rapid growth. Application of an energy system model for Gauteng province, South Africa

    Tomaschek, Jan

    2013-12-11

    The transport sector is seen as one of the key factors for driving future energy consumption and greenhouse gas (GHG) emissions. Especially in developing countries, significant growth in transport demand is expected. Gauteng province, as the economic centre of South Africa and transport hub for the whole of southern Africa, is one emerging urban region that faces rapid growth. However, the province is on its way to playing a leading role for supporting ways to adapt to climate change and mitigate GHG emissions. Conversely, there is a lack of scientific research on the promising measures for GHG mitigation in the transport sector. For the rapidly growing transport sector of the province in particular, research is focused primarily on extending and structuring the road infrastructure. Moreover, it is important that the transport sector is considered as part of the whole energy system, as significant contributions to GHG emissions and the associated costs arise from energy supply, provision and conversion. This research is the first application of an integrated energy system model (i.e. the TIMES-GEECO model) for the optimization of the transport sector of Gauteng. Optimizing energy system models allows finding least-cost measures for various scenarios, by considering dependencies and interlinkages in the energy system as well as environmental constraints. To do so, the transport sector and the energy supply sector had to be incorporated into the model application in terms of the characteristics of a developing urban region, which includes all relevant transport modes, vehicle technologies, fuel options, vehicle-to-grid energy storage, the consideration of road types as well as explicit expansions of the public transport system and income-dependent travel demand modelling. Additionally, GHG mitigation options outside the provincial boundaries were incorporated to allow for mitigation at least cost and to consider regional resource availability. Moreover, in TIMES

  13. Long-term optimization of the transport sector to address greenhouse gas reduction targets under rapid growth. Application of an energy system model for Gauteng province, South Africa

    Tomaschek, Jan

    2013-01-01

    The transport sector is seen as one of the key factors for driving future energy consumption and greenhouse gas (GHG) emissions. Especially in developing countries, significant growth in transport demand is expected. Gauteng province, as the economic centre of South Africa and transport hub for the whole of southern Africa, is one emerging urban region that faces rapid growth. However, the province is on its way to playing a leading role for supporting ways to adapt to climate change and mitigate GHG emissions. Conversely, there is a lack of scientific research on the promising measures for GHG mitigation in the transport sector. For the rapidly growing transport sector of the province in particular, research is focused primarily on extending and structuring the road infrastructure. Moreover, it is important that the transport sector is considered as part of the whole energy system, as significant contributions to GHG emissions and the associated costs arise from energy supply, provision and conversion. This research is the first application of an integrated energy system model (i.e. the TIMES-GEECO model) for the optimization of the transport sector of Gauteng. Optimizing energy system models allows finding least-cost measures for various scenarios, by considering dependencies and interlinkages in the energy system as well as environmental constraints. To do so, the transport sector and the energy supply sector had to be incorporated into the model application in terms of the characteristics of a developing urban region, which includes all relevant transport modes, vehicle technologies, fuel options, vehicle-to-grid energy storage, the consideration of road types as well as explicit expansions of the public transport system and income-dependent travel demand modelling. Additionally, GHG mitigation options outside the provincial boundaries were incorporated to allow for mitigation at least cost and to consider regional resource availability. Moreover, in TIMES

  14. A rapid novel derivatization of amphetamine and methamphetamine using 2,2,2-trichloroethyl chloroformate for gas chromatography electron ionization and chemical ionization mass spectrometric analysis.

    Dasgupta, A; Spies, J

    1998-05-01

    Amphetamine and methamphetamine are commonly abused central nervous system stimulants. We describe a rapid new derivatization of amphetamine and methamphetamine using 2,2,2-trichloroethyl chloroformate for gas chromatography-mass spectrometric analysis. Amphetamine and methamphetamine, along with N-propyl amphetamine (internal standard), were extracted from urine using 1-chlorobutane. The derivatization with 2,2,2-trichloroethyl chloroformate can be achieved at room temperature in 10 minutes. The electron ionization mass spectrum of amphetamine 2,2,2-trichloroethyl carbamate showed two weak molecular ions at m/z 309 and 311, but showed diagnostic strong peaks at m/z 218, 220, and 222. In contrast, chemical ionization of the mass spectrum of amphetamine 2,2,2-trichloroethyl carbamate showed strong (M + 1) ions at m/z 310 and 312 and other strong diagnostic peaks at m/z 274 and 276. The major advantages of this derivative are the presence of a diagnostic cluster of peaks due to the isotopic effect of three chlorine atoms (isotopes 35 and 37) in the derivatized molecule and the relative ease of its preparation. We also observed strong molecular ions for derivatized methamphetamine in the chemical ionization mass spectrum, but the molecular ions were very weak in the electron ionization mass spectrum. We used the scan mode of mass spectrometry in all analyses. When using a urine standard containing 1,000 ng/mL of amphetamine (a 7.4-micromol/L concentration) and methamphetamine (a 6.7-micromol/L concentration), the within-run precisions were 4.8% for amphetamine and 3.6% for methamphetamine. The corresponding between-run precisions were 5.3% for amphetamine and 6.7% for methamphetamine. The assay was linear for amphetamine and methamphetamine concentrations of 250 to 5,000 ng/mL (amphetamine, 1.9-37.0 micromol/L; methamphetamine, 1.7-33.6 micromol/L). The detection limit was 100 ng/mL (amphetamine, 0.74 micromol/L; methamphetamine, 0.67 micromol/L) using the scan mode

  15. Ion Chromatographic Analyses of Sea Waters, Brines and Related Samples

    Nataša Gros

    2013-01-01

    This review focuses on the ion chromatographic methods for the analyses of natural waters with high ionic strength. At the beginning a natural diversity in ionic composition of waters is highlighted and terminology clarified. In continuation a brief overview of other review articles of potential interest is given. A review of ion chromatographic methods is organized in four sections. The first section comprises articles focused on the determination of ionic composition of water samples as com...

  16. Reverse-Phase High-Performance Liquid Chromatographic Separation of Methylated and Non-Methylated Nucleic Acid Bases

    Madyastha, Prema; Rao, Pratima; Deobagkar, DN; Madyastha, KM

    1983-01-01

    A high-performance liquid chromatographic sepration method is described for the detection of 5-methylcytosine and 6-methyladenine in nucleic acid ext. The bases were sepd. on a Waters $C18 \\mu$ Bondapak column with a water: methanol acetic acid system. Effluents were monitored by UV absorption at 254 nm. The bases were estd. by peak heights which are proportional to the amts. of the individual bases. The method is rapid, sensitive, easy to perform and reproducible.

  17. Measurements of potato tubers gamma-ray irradiated in nitrogen gas or carbondioxide gas

    Katayama, Tadashi; Ohnishi, Tokuhiro; Dohmaru, Takaaki; Kanazawa, Tamotsu; Hiraoka, Eiichi; Furuta, Jun-ichiro.

    1984-01-01

    In this report the respiration of the potato tubers irradiated in nitrogen gas or carbondioxide gas was studied. Potato tubers of common Japanese variety, ''Danshaku'' were used for the examination. Potato tubers of about 2kg were put into each of Triple-Nylon bags and the bags were sealed after replacement of air in bags with nitrogen or carbondioxide gases. More than 16 hours after sealing of bags, the γ-dose ( 60 Co) of 150 Gy or 250 Gy were given to the potato tubers in bags at the dose rate of 10 4 R/h. After irradiation, all bags were opened in air and amounts of CO 2 released by respiration of tubers were measured with Hitachi gas chromatograph analyser Type 023. The amounts of CO 2 released from the potato tubers irradiated in open air is shown in Fig. 2. The results show that there is an initial lag period of several hours, followed by a rapid increase in the respiration, after which the CO 2 release was gradually decreased. Potato tubers irradiated in nitrogen gas show a similar release of CO 2 on time scale to the potato tubers irradiated in open air, but the total amounts of CO 2 are approximately half of those of the potato tubers irradiated in open air (Figs. 3 and 4). (J.P.N.)

  18. Chromatographic separation of fructose from date syrup.

    Al Eid, Salah M

    2006-01-01

    The objective of this study is to provide a process for separating fructose from a mixture of sugars containing essentially fructose and glucose, obtained from date palm fruits. The extraction procedure of date syrup from fresh dates gave a yield of 86.5% solids after vacuum drying. A process for separating fructose from an aqueous solution of date syrup involved adding the date syrup solutions (20, 30 and 40% by weight) to a chromatographic column filled with Dowex polystyrene strong cation exchange gel matrix resin Ca2 + and divinylbenzene, a functional group, sulfonic acid, particle size 320 microm, with a flow rate of 0.025 and 0.05 bed volume/min, under 30 and 70 degrees C column temperature. After the date sugar solution batch, a calculated quantity of water was added to the column. Glucose was retained by the resin more weakly than fructose and proceeded faster into the water batch flowing ahead. Three fractions were collected: a glucose-rich fraction, a return fraction, and a fructose-rich fraction. The return fraction is based on when the peaks of fructose and glucose were reached, which could be determined by means of an analyzer (polarimeter) based on the property of glucose and fructose solutions to turn the polarization level of polarized light. A high yield of fructose is obtained at 70 degrees C column temperature with a flow rate of 0.025 bed volume/min and date syrup solution containing 40% sugar concentration. The low recovery by weight obtained using date syrup solutions having a sugar concentration of 20 and 30%, encourages the use of a concentration of 40%. However, with the 40% date syrup supply the average concentrations of glucose and fructose in the return fractions were more than 40%, which can be used for diluting the thick date syrup solution extracted from dates.

  19. Exploring Blueberry Aroma Complexity by Chromatographic and Direct-Injection Spectrometric Techniques

    Farneti, Brian; Khomenko, Iuliia; Grisenti, Marcella; Ajelli, Matteo; Betta, Emanuela; Algarra, Alberto Alarcon; Cappellin, Luca; Aprea, Eugenio; Gasperi, Flavia; Biasioli, Franco; Giongo, Lara

    2017-01-01

    , for the most aldehydes, alcohols, terpenoids, and esters that can be used as putative biomarkers to rapidly evaluate the blueberry aroma variations related to ripening and/or senescence as well as to genetic background differences. Moreover, the obtained results demonstrated the complementarity between chromatographic and direct-injection mass spectrometric techniques to study the blueberry aroma. PMID:28491071

  20. Exploring Blueberry Aroma Complexity by Chromatographic and Direct-Injection Spectrometric Techniques

    Brian Farneti

    2017-04-01

    pull of VOCs, for the most aldehydes, alcohols, terpenoids, and esters that can be used as putative biomarkers to rapidly evaluate the blueberry aroma variations related to ripening and/or senescence as well as to genetic background differences. Moreover, the obtained results demonstrated the complementarity between chromatographic and direct-injection mass spectrometric techniques to study the blueberry aroma.

  1. Exploring Blueberry Aroma Complexity by Chromatographic and Direct-Injection Spectrometric Techniques.

    Farneti, Brian; Khomenko, Iuliia; Grisenti, Marcella; Ajelli, Matteo; Betta, Emanuela; Algarra, Alberto Alarcon; Cappellin, Luca; Aprea, Eugenio; Gasperi, Flavia; Biasioli, Franco; Giongo, Lara

    2017-01-01

    , and esters that can be used as putative biomarkers to rapidly evaluate the blueberry aroma variations related to ripening and/or senescence as well as to genetic background differences. Moreover, the obtained results demonstrated the complementarity between chromatographic and direct-injection mass spectrometric techniques to study the blueberry aroma.

  2. Chromatographic method of measurement of helium concentration in underground waters for dating in hydrological questions

    Najman, J.

    2008-04-01

    Research methods which use natural environmental indicators are widely applied in hydrology. Different concentrations of indicators and their isotopic components in ground waters allow to determine the genesis of waters and are valuable source of information about the water flow dynamics. One of the significant indicator is helium. The concentration of 4 He (helium) in ground water is a fine indicator in water dating in a range from a hundreds to millions of years (Aeschbach-Hertig i in., 1999; Andrews i in., 1989; Castro i in., 2000; Zuber i in., 2007). 4 He is also used for dating young waters of age about 10 years (Solomon i in., 1996). Thesis consist the description of elaborated in IFJ PAN in Krakow chromatographic measurement method of helium concentration in ground waters in aim of dating. Chapter 1 contain short introduction about ground water dating and chapter 2 description of helium property and chosen applications of helium for example in technology and earthquake predictions. Helium sources in ground waters are described in chapter 3. Helium concentration in water after infiltration (originated from atmosphere) to the ground water system depends mainly on the helium concentration coming from the equilibration with the atmosphere increased by additional concentration from '' excess air ''. With the increasing resistance time of ground water during the flow, radiogenic, non-atmospheric component of helium dissolves also in water. In chapter 4 two measurement methods of helium concentration in ground waters were introduced: mass spectrometric and gas chromatographic method. Detailed description of elaborated chromatographic measurement method of helium concentration in ground water contain chapter 5. To verify developed method the concentration of helium in ground waters from the regions of Krakow and Busko Zdroj were measured. For this waters the concentrations of helium are known from the earlier mass spectrometric measurements. The results of

  3. Chromatographic 188W →188Re generator

    Khujaev, S.

    2005-01-01

    Full text: The main purpose of the generator - reception of daughter radioisotope Rhenium-188 from it by periodic elution for a long period of time (more than half-year). It is generally known that Rhenium-188, in the form of its complex connections, is applied in nuclear medicine in treatment and removal of painful syndromes. The generator possesses convenient nuclear-physical characteristics of a daughter radioisotope Rhenium-188. It is a source of (Irradiation with energy 2.12 MeV (98 %) with small contribution soft γ-radiation with energy 0.155 MeV (15 %). The Period of half-life destruction of radioisotope is 17 hours. The 188 W parent radioisotope for the generator is formed by irradiation of 186 W neutrons based on the following reaction: 186 W (n,γ) 187 W (n,γ) 188 W (69 days) → 188 Re (17 hours) + β The following were used as targets for irradiation: 1) Metal Tungsten (powder) of natural structure; 2) Metal Tungsten (plate) of natural structure; 3) Metal Tungsten (wire) of natural structure, d = 12 mm; 4) Metal Tungsten (powder) with enrichment on isotope 186 W - 99.79 %. The irradiated material was exposed to chemical processing with reception of radioactive solution of tungsten-188, from which sorption Tungsten was carried out onto sorbent as poly-wolframate-ions. It is established that Tungsten sorption depends on many factors as there are various chemical forms of Tungsten (VI) in water solutions, ratio of which depends on pH of the solution, concentration of Tungsten in the solution and presence of foreign ions. Tungsten sorption was carried out in static and in dynamic regimes. At dynamic regime the sorbent was placed directly in the generating column. The generator consisted of chromatographic columns with sorbent and radioisotope 188 W, eluting system and radiation protection. Rhenium-188 was taken from the generator as perrhenate sodium by elution of 0.9 % solution of chloride sodium in 10 ml. Technical characteristics of the generator

  4. Recent developments on field gas extraction and sample preparation methods for radiokrypton dating of groundwater

    Yokochi, Reika

    2016-09-01

    Current and foreseen population growths will lead to an increased demand in freshwater, large quantities of which is stored as groundwater. The ventilation age is crucial to the assessment of groundwater resources, complementing the hydrological model approach based on hydrogeological parameters. Ultra-trace radioactive isotopes of Kr (81 Kr and 85 Kr) possess the ideal physical and chemical properties for groundwater dating. The recent advent of atom trap trace analyses (ATTA) has enabled determination of ultra-trace noble gas radioisotope abundances using 5-10 μ L of pure Kr. Anticipated developments will enable ATTA to analyze radiokrypton isotope abundances at high sample throughput, which necessitates simple and efficient sample preparation techniques that are adaptable to various sample chemistries. Recent developments of field gas extraction devices and simple and rapid Kr separation method at the University of Chicago are presented herein. Two field gas extraction devices optimized for different sampling conditions were recently designed and constructed, aiming at operational simplicity and portability. A newly developed Kr purification system enriches Kr by flowing a sample gas through a moderately cooled (138 K) activated charcoal column, followed by a gentle fractionating desorption. This simple process uses a single adsorbent and separates 99% of the bulk atmospheric gases from Kr without significant loss. The subsequent two stages of gas chromatographic separation and a hot Ti sponge getter further purify the Kr-enriched gas. Abundant CH4 necessitates multiple passages through one of the gas chromatographic separation columns. The presented Kr separation system has a demonstrated capability of extracting Kr with > 90% yield and 99% purity within 75 min from 1.2 to 26.8 L STP of atmospheric air with various concentrations of CH4. The apparatuses have successfully been deployed for sampling in the field and purification of groundwater samples.

  5. The development of a high performance liquid chromatograph with a sensitive on-stream radioactivity monitor for the analysis of 3H- and 14C-labelled gibberellins

    Reeve, D.R.; Yokota, T.; Nash, L.; Crozier, A.

    1976-01-01

    The development of a high performance liquid chromatograph for the separation of gibberellins is described. The system combines high efficiency, peak capacity, and sample capacity with rapid speed of analysis. In addition, the construction details of a sensitive on-stream radioactivity monitor are outlined. The overall versatility of the chromatograph has been demonstrated by the separation of a range of 3 H- and 14 C-labelled gibberellins and gibberellin precursors. The system also has considerable potential for the analysis of abscisic acid and acidic and neutral indoles. (author)

  6. Overlapping Patterns of Rapid Evolution in the Nucleic Acid Sensors cGAS and OAS1 Suggest a Common Mechanism of Pathogen Antagonism and Escape.

    Hancks, Dustin C; Hartley, Melissa K; Hagan, Celia; Clark, Nathan L; Elde, Nels C

    2015-05-01

    A diverse subset of pattern recognition receptors (PRRs) detects pathogen-associated nucleic acids to initiate crucial innate immune responses in host organisms. Reflecting their importance for host defense, pathogens encode various countermeasures to evade or inhibit these immune effectors. PRRs directly engaged by pathogen inhibitors often evolve under recurrent bouts of positive selection that have been described as molecular 'arms races.' Cyclic GMP-AMP synthase (cGAS) was recently identified as a key PRR. Upon binding cytoplasmic double-stranded DNA (dsDNA) from various viruses, cGAS generates the small nucleotide secondary messenger cGAMP to signal activation of innate defenses. Here we report an evolutionary history of cGAS with recurrent positive selection in the primate lineage. Recent studies indicate a high degree of structural similarity between cGAS and 2'-5'-oligoadenylate synthase 1 (OAS1), a PRR that detects double-stranded RNA (dsRNA), despite low sequence identity between the respective genes. We present comprehensive comparative evolutionary analysis of cGAS and OAS1 primate sequences and observe positive selection at nucleic acid binding interfaces and distributed throughout both genes. Our data revealed homologous regions with strong signatures of positive selection, suggesting common mechanisms employed by unknown pathogen encoded inhibitors and similar modes of evasion from antagonism. Our analysis of cGAS diversification also identified alternately spliced forms missing multiple sites under positive selection. Further analysis of selection on the OAS family in primates, which comprises OAS1, OAS2, OAS3 and OASL, suggests a hypothesis where gene duplications and domain fusion events result in paralogs that provide another means of escaping pathogen inhibitors. Together our comparative evolutionary analysis of cGAS and OAS provides new insights into distinct mechanisms by which key molecular sentinels of the innate immune system have adapted

  7. Overlapping Patterns of Rapid Evolution in the Nucleic Acid Sensors cGAS and OAS1 Suggest a Common Mechanism of Pathogen Antagonism and Escape.

    Dustin C Hancks

    2015-05-01

    Full Text Available A diverse subset of pattern recognition receptors (PRRs detects pathogen-associated nucleic acids to initiate crucial innate immune responses in host organisms. Reflecting their importance for host defense, pathogens encode various countermeasures to evade or inhibit these immune effectors. PRRs directly engaged by pathogen inhibitors often evolve under recurrent bouts of positive selection that have been described as molecular 'arms races.' Cyclic GMP-AMP synthase (cGAS was recently identified as a key PRR. Upon binding cytoplasmic double-stranded DNA (dsDNA from various viruses, cGAS generates the small nucleotide secondary messenger cGAMP to signal activation of innate defenses. Here we report an evolutionary history of cGAS with recurrent positive selection in the primate lineage. Recent studies indicate a high degree of structural similarity between cGAS and 2'-5'-oligoadenylate synthase 1 (OAS1, a PRR that detects double-stranded RNA (dsRNA, despite low sequence identity between the respective genes. We present comprehensive comparative evolutionary analysis of cGAS and OAS1 primate sequences and observe positive selection at nucleic acid binding interfaces and distributed throughout both genes. Our data revealed homologous regions with strong signatures of positive selection, suggesting common mechanisms employed by unknown pathogen encoded inhibitors and similar modes of evasion from antagonism. Our analysis of cGAS diversification also identified alternately spliced forms missing multiple sites under positive selection. Further analysis of selection on the OAS family in primates, which comprises OAS1, OAS2, OAS3 and OASL, suggests a hypothesis where gene duplications and domain fusion events result in paralogs that provide another means of escaping pathogen inhibitors. Together our comparative evolutionary analysis of cGAS and OAS provides new insights into distinct mechanisms by which key molecular sentinels of the innate immune system

  8. Probabilistic peak detection for first-order chromatographic data.

    Lopatka, M; Vivó-Truyols, G; Sjerps, M J

    2014-03-19

    We present a novel algorithm for probabilistic peak detection in first-order chromatographic data. Unlike conventional methods that deliver a binary answer pertaining to the expected presence or absence of a chromatographic peak, our method calculates the probability of a point being affected by such a peak. The algorithm makes use of chromatographic information (i.e. the expected width of a single peak and the standard deviation of baseline noise). As prior information of the existence of a peak in a chromatographic run, we make use of the statistical overlap theory. We formulate an exhaustive set of mutually exclusive hypotheses concerning presence or absence of different peak configurations. These models are evaluated by fitting a segment of chromatographic data by least-squares. The evaluation of these competing hypotheses can be performed as a Bayesian inferential task. We outline the potential advantages of adopting this approach for peak detection and provide several examples of both improved performance and increased flexibility afforded by our approach. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. A new fiber-optic sensor technology for rapid and inexpensive characterization of soil contamination

    Milanovich, F.P.; Brown, S.B.; Colston, B.W. Jr.; Daley, P.F.; Rossabi, J.

    1993-04-01

    The extent and complexity of worldwide environmental contamination are great enough that remediation will be extremely costly and lengthy. There is an urgent need for characterization techniques that are rapid, inexpensive, and simple and that do not generate waste. Towards this end LLNL is developing a fiber-optic chemical sensor technology for use in groundwater and vadose-zone monitoring. We use a colorimetric detection technique, based on an irreversible chemical reaction between a specific reagent and the target compound. The accuracy and sensitivity of the sensor (<5 ppb by weight in water, determined by comparison with gas chromatographic standard measurements) are sufficient for environmental monitoring of at least trichloroethylene (TCE) and chloroform

  10. Gas Chromatic Mass Spectrometer

    Wey, Chowen

    1995-01-01

    Gas chromatograph/mass spectrometer (GC/MS) used to measure and identify combustion species present in trace concentration. Advanced extractive diagnostic method measures to parts per billion (PPB), as well as differentiates between different types of hydrocarbons. Applicable for petrochemical, waste incinerator, diesel transporation, and electric utility companies in accurately monitoring types of hydrocarbon emissions generated by fuel combustion, in order to meet stricter environmental requirements. Other potential applications include manufacturing processes requiring precise detection of toxic gaseous chemicals, biomedical applications requiring precise identification of accumulative gaseous species, and gas utility operations requiring high-sensitivity leak detection.

  11. Coalbed gas desorption in canisters: Consumption of trapped atmospheric oxygen and implications for measured gas quality

    Jin, Hui; Schimmelmann, Arndt [Indiana University, Dept. of Geological Sciences, Bloomington, IN 47405-1405 (United States); Mastalerz, Maria [Indiana University, Indiana Geological Survey, Bloomington, IN 47405-2208 (United States); Pope, James [CRL Energy Ltd., 123 Blenheim Road, Christchurch (New Zealand); University of Canterbury, Dept. of Geological Sciences, Christchurch (New Zealand); Moore, Tim A. [University of Canterbury, Dept. of Geological Sciences, Christchurch (New Zealand); P.T. Arrow Energy Indonesia, Wisma Anugraha, Jl. Taman Kemang No. 32B, Jakarta Selatan (Indonesia)

    2010-01-07

    Desorption canisters are routinely employed to quantify coalbed gas contents in coals. If purging with inert gas or water flooding is not used, entrapment of air with {proportional_to} 78.08 vol.% nitrogen (N{sub 2}) in canisters during the loading of coal results in contamination by air and subsequent overestimates of N{sub 2} in desorbed coalbed gas. Pure coalbed gas does not contain any elemental oxygen (O{sub 2}), whereas air contamination originally includes {proportional_to} 20.95 vol.% O{sub 2} and has a N{sub 2}/O{sub 2} volume ratio of {proportional_to} 3.73. A correction for atmospheric N{sub 2} is often attempted by quantifying O{sub 2} in headspace gas and then proportionally subtracting atmospheric N{sub 2}. However, this study shows that O{sub 2} is not a conservative proxy for air contamination in desorption canisters. Time-series of gas chromatographic (GC) compositional data from several desorption experiments using high volatile bituminous coals from the Illinois Basin and a New Zealand subbituminous coal document that atmospheric O{sub 2} was rapidly consumed, especially during the first 24 h. After about 2 weeks of desorption, the concentration of O{sub 2} declined to near or below GC detection limits. Irreversible loss of O{sub 2} in desorption canisters is caused by biological, chemical, and physical mechanisms. The use of O{sub 2} as a proxy for air contamination is justified only immediately after loading of desorption canisters, but such rapid measurements preclude meaningful assessment of coalbed gas concentrations. With increasing time and progressive loss of O{sub 2}, the use of O{sub 2} content as a proxy for atmospheric N{sub 2} results in overestimates of N{sub 2} in desorbed coalbed gas. The indicated errors for nitrogen often range in hundreds of %. Such large analytical errors have a profound influence on market choices for CBM gas. An erroneously calculated N{sub 2} content in CBM would not meet specifications for most pipeline

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

    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.

  13. Developing a Natural Gas-Powered Bus Rapid Transit Service: A Case Study on Leadership: Roaring Fork Transportation Authority (Presentation); NREL (National Renewable Energy Laboratory)

    Schroeder, A.

    2015-03-01

    The Roaring Fork Transportation Authority (RFTA) represents a series of unique successes in alternative fuel deployment by pushing the envelope with innovative solutions. In the last year, RFTA demonstrated the ability to utilize compressed natural gas buses at a range of altitudes, across long distances, in extreme weather conditions and in a modern indoor fueling and maintenance facility - allwhile saving money and providing high-quality customer service. This case study will highlight how the leadership of organizations and communities that are implementing advances in natural gas vehicle technology is paving the way for broader participation.

  14. Development of Direct Reversed-Phase High Performance liquid chromatographic method for quantitative determination of gabapentin in pharmaceutical dosage

    Hassan, W.; Zaman, B.; Rahman, S.; Rahman, A.U.; Ali, N.; Mohammadzai, I.U.

    2012-01-01

    The objective of the present work was to develop and validate a rapid analytical method for quantitative determination of Gabapentin in pharmaceutical dosage tablets and capsules. An accurate, simple, and sensitive reversed-phase high performance liquid chromatographic (HPLC) method, UV detection at 215 nm and flow rate at 1.0 ml/min has been developed. Isocratic elution was used instead of gradient elution to reduce the time and cost of serial analysis. The mobile phase was a mixture of water and methanol (HPLC grade). The retention time (Rt) of Gabapentin was 4.681 +- 0.013 minutes. Recovery, Precision, accuracy, and linearity were determined for the stated method. The calibration curve was linear and the correlation coefficient was 0.9996. There was no chromatographic interference from other excipients present in dosage form. The method was validated appropriately and successfully used for determination of Gabapentin in Pharmaceutical formulations. (author)

  15. Performance characteristics of bioassay, radioenzymatic assay, homogeneous enzyme immunoassay, and high-performance liquid chromatographic determination of serum gentamicin

    Delaney, C.J.; Opheim, K.E.; Smith, A.L.; Plorde, J.J.

    1982-01-01

    We compared the accuracy, precision, and between-method error of the microbiological assay, the radioenzymatic assay, the homogeneous enzyme immunoassay, and the high-performance liquid chromatographic assay for the quantitation of gentamicin in serum. Precision and accuracy were evaluated by reference samples prepared to contain 0.0 to 32.7 micrograms of gentamicin per ml. Correlations between the methods utilized patient sera with gentamicin concentrations ranging from 0.6 to 13.3 micrograms/ml. All methods were reliable within acceptable limits for routine clinical use; intermethod correlation coefficients exceeded 0.96. Relative to the microbiological assay, the alternative methods offer the advantage of rapid analysis. The elapsed times for acquiring data on a set of 10 specimens under routine operating conditions were 0.5 h by the enzyme immunoassay, 4 h by the radioenzymatic assay, 5 h by the high-performance liquid chromatographic assay, and 10 h by the microbiological assay

  16. Gas chromatography of adducts of rare earth dipivaloylmethanates with triphenylphosphine oxide

    Magazeeva, N.V.; Martynenko, L.I.; Murav'eva, I.A.; Spitsyn, V.I.

    1987-01-01

    A gas chromatographic method for determination of stability provisional constants of dipivaloylmethanates of REE with triphenylphosphine oxide is suggested, and ML 3 xTPPO adduct stability is shown to decrease in Ho-Lu series. ML 3 chromatographing at the presence of TPPO is stated to increase the coefficients of REE separation

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

    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

  18. Determinação simultânea dos ácidos hipúrico e metil-hipúrico urinários por métodos cromatográficos: comparação entre cromatografia líquida de alta eficiência e cromatografia gasosa capilar Simultaneous determination of urinary hyppuric and methylhyppuric acids through chromatographic methods: comparation between high performance liquid chromatography and capilary gas chromatography

    Zelaine Lima Silva

    2002-06-01

    Full Text Available O presente trabalho foi realizado objetivando-se comparar a eficiência de dois métodos analíticos, um por cromatografia líquida de alta eficiência (CLAE e outro por cromatografia em fase gasosa com coluna capilar (CG, na determinação conjunta do ácido hipúrico (AH e ácido metil-hipúrico (AMH em urina de indivíduos expostos ocupacionalmente ao tolueno e xileno. Após a validação analítica foi observado que o método CLAE apresentou melhores precisão intra e interensaio, porcentagem de recuperação e sensibilidade. Amostras de urina de trabalhadores expostos aos dois solventes em fábrica de tintas-látex foram analisadas pelos dois métodos validados e os resultados avaliados estatisticamente. Não se encontrou diferença significativa entre os valores de AH superiores a 1,0 g/g de creatinina, quando determinados pelos dois métodos cromatográficos. Esta similaridade não foi repetida quando os níveis de AH eram inferiores a 1,0 g/g de creatinina. Os valores de AMH nas amostras analisadas estavam, na maioria das vezes, abaixo do limite de deteção, razão pela qual não foi realizada a comparação estatística entre os mesmos.High performance liquid chromatography and capillary gas chromatography were compared for simultaneous measurement of hyppuric and methyl hyppuric acids in urine of workers co-exposed to toluene and xilene. Quantitative advantages offered by HPLC over capillary GC method are observed: better average recovery, wider dynamic interval in calibration curve and lower detection and quantification limits mainly when MHA measurement was performed. No significant difference was found between the values of HA higher than 1.0 g/g creatinine measured by the two chromatographic procedures. Regarding to MHA concentration the methods gave similar results and there was no significant difference between the values.

  19. Chromatographic fingerprinting through chemometric techniques for herbal slimming pills: A way of adulterant identification.

    Shekari, Nafiseh; Vosough, Maryam; Tabar Heidar, Kourosh

    2018-05-01

    In the current study, gas chromatography-mass spectrometry (GC-MS) fingerprinting of herbal slimming pills assisted by chemometric methods has been presented. Deconvolution of two-way chromatographic signals of nine herbal slimming pills into pure chromatographic and spectral patterns was performed. The peak clusters were resolved using multivariate curve resolution-alternating least squares (MCR-ALS) by employing appropriate constraints. It was revealed that more useful chemical information about the composition of the slimming pills can be obtained by employing sophisticated GC-MS method coupled with proper chemometric tools yielding the extended number of identified constituents. The thorough fingerprinting of the complex mixtures proved the presence of some toxic or carcinogen components, such as toluene, furfural, furfuryl alcohol, styrene, itaconic anhydride, citraconic anhydride, trimethyl phosphate, phenol, pyrocatechol, p-propenylanisole and pyrogallol. In addition, some samples were shown to be adulterated with undeclared ingredients, including stimulants, anorexiant and laxatives such as phenolphthalein, amfepramone, caffeine and sibutramine. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Chromatographic enrichment of isotopes in hydrogen and water samples on palladium

    Andreev, B.M.; Polevoi, A.S.; Perevezentsev, A.N.

    1987-01-01

    Data on the isotopic enrichment of hydrogen and water samples by chromatography on palladium have been analyzed. Experimental data on the effect of temperature, hydrogen flow, volume of the enriched fraction, and length of the chromatographic column on the degree of separation attainable in the column have been obtained. It has been shown that the maximum separation achievable (regardless of the type of the isotope mixture) at 273 K falls with increase of hydrogen flow and volume of the enriched gas fraction recoverable from the column. A separation degree of ∼ 1040 has been achieved for a mixture of protium and deuterium in a 10-mm wide and 0.6-m long chromatographic column packed with palladium black with a grain size of 0.2-0.5 mm at 273 K and a specific hydrogen flow of 1.22 mole/m 2 x sec. For a protium-tritium mixture a separation degree of ∼ 90 has been reached in a similar column at 273 K and a specific hydrogen flow of 0.4 mole/m 2 x sec