Sample records for column gas chromatographic

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

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    Gevany Paulino de Pinho


    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.

  2. Gas Chromatograph Method Optimization Trade Study for RESOLVE: 20-meter Column v. 8-meter Column (United States)

    Huz, Kateryna


    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

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

    International Nuclear Information System (INIS)

    Kang Zhongrong; Li Biping; Zeng Yongchang


    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

  4. Ionic liquid functionalization of semi-packed columns for high-performance gas chromatographic separations. (United States)

    Regmi, Bishnu P; Chan, Ryan; Agah, Masoud


    Gas chromatography columns fabricated using microelectromechanical system (MEMS) technology provide a number of clear advantages. However, successful deposition of stationary phases having a wide application range remains an important technical challenge. In this paper, we report, for the first time, on the deposition of room temperature ionic liquids (RTILs)-a versatile class of stationary phases-inside the channels of semi-packed columns (SPCs) for high-performance gas chromatographic separation of complex chemical mixtures. A 1m long, 240μm deep, 190μm wide column comprising an array circular micropillars of 20μm in diameter and 40μm post spacing was fabricated using MEMS processes. Two RTILs were immobilized inside these columns using a dynamic coating method, and the columns were tested for separation of three different mixtures: a 15-component mixture of hazardous chemical pollutants, an 8-component mixture of fatty acid methyl esters, and a sample of gasoline. These columns displayed sharp and symmetrical peaks, significant selectivity variation between the two columns, and rapid separation times. The columns yielded high separation efficiencies measured by approximately 2300 plates/m under isothermal conditions. This work highlights the potential of RTILs to be used as excellent stationary phases for SPCs, thereby dramatically expanding the range of complex mixtures that could be analyzed using a micro gas chromatograph. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Cross-column prediction of gas-chromatographic retention of polybrominated diphenyl ethers. (United States)

    D'Archivio, Angelo Antonio; Giannitto, Andrea; Maggi, Maria Anna


    In this paper, we predict the retention of polybrominated diphenyl ethers (PBDEs) in capillary gas-chromatography (GC) within a useful range of separation conditions. In a first stage of this study, quantitative structure-retention relationships (QSRRs) of PBDEs in six stationary phases with different polarity are established. The single-column QSRR models are generated using the retention data of 126 PBDE congeners by multilinear regression (MLR) coupled to genetic algorithm variable selection applied to a large set of theoretical molecular descriptors of different classes. A quite accurate fitting of experimental retentions is obtained for each of the six GC columns adopting five molecular descriptors. In a further step of this work six molecular descriptors were extracted within the set of molecular descriptors (17 variables) involved in the various single-column QSRRs. The selected molecular descriptors are combined with observed retentions of ten representative PBDEs, adopted as descriptors of the GC system. These quantities are considered as the independent variables of a multiple-column retention model able to simultaneously relate GC retention to PBDE molecular structure and kind of column. The quantitative structure/column-retention relationship is established using a multi-layer artificial neural network (ANN) as regression tool. To optimise the ANN model, a validation set is generated by selecting two out of the six calibration columns. Splitting of columns between training and validation sets, as well as selection of PBDE congeners to be used as column descriptors, is performed with the help of a principal component analysis on the retention data. Cross-column predictive performance of the final model is tested on a large external set consisting of retention data of 180 PBDEs collected in four separation conditions different from those considered in model calibration (different columns and/or temperature program). Copyright © 2013 Elsevier B.V. All

  6. Evaluation of highly polar ionic liquid gas chromatographic column for the determination of the fatty acids in milk fat. (United States)

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


    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.

  7. Gas chromatographical detection of oxygenated compounds in gasoline with a switching capillary column system

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    Winskowski, J.


    In this paper the separation and identification of oxygenated compounds in gasoline is described. Using a two-dimensional column system swtiching from a high polar TCEP-capillary column (1,2,3-Tris(cyanoethoxy)propan) to a non-polar column with a greater filmthickness of DMS (dimethylpolysiloxane) acetone and alcohols as well as further ketones and esters were separated from the hydrocarbon matrix without any difficulties. The analysis of the ethers is more difficult, especially in presence of olefinic compounds, mainly occuring in crack and pyrolysis gasoline, and can only be carried out if highly efficient capillary columns are applied. A test mixture is proposed which can be used to find out whether column systems are suitable for this purpose. The total amount of oxygen can be calculated from the single components after identification. (orig.)

  8. New Liquid Phases for the Gas Chromatographic Separation of Strong Bases on Capillary Columns


    Grob, K.


    The current practice of pretreating the solid support with free alkali to increase separation efficiency for basic compounds proved to be unsuitable for capillary columns. Instead of this, homogenous organic materials of high base strength are required. We found polyethylene imine (PEI) and polypropylene imine (PPI) to be very efficient as liquid phases of capillary columns for the separation of bases. The preparation of polymers is mentioned. Silanization or acetylation of the free hydroxyl ...

  9. Exploring reverse shape selectivity and molecular sieving effect of metal-organic framework UIO-66 coated capillary column for gas chromatographic separation. (United States)

    Chang, Na; Yan, Xiu-Ping


    Metal-organic frameworks (MOFs) which offer a variety of topologies, porous networks and high surface areas are promising and have potential for the applications of specific adsorption, isomerization, catalysis and separation. UIO-66 is the first MOF that has been observed to have reverse shape selectivity. However, such reverse shape selectivity of MOFs has never been explored for capillary gas chromatographic separation. Here we report the fabrication of MOF UIO-66 coated capillary column and exploration of the reverse shape selectivity and molecular sieving effect of such column for capillary gas chromatographic separation of alkane isomers and benzene homologues with excellent selectivity and precision. The adsorption enthalpies and entropies on the interaction between hydrocarbons and UIO-66 were measured to illustrate the energy effect on the separation of alkane isomers and benzene homologues on the UIO-66 coated capillary column. UIO-66 coated capillary column gave preferential retention of branched alkane isomers over their linear isomer, showing reverse shape selectivity, making UIO-66 coated capillary column attractive for capillary gas chromatographic separation of alkane isomers. iso-Propylbenzene (branched) eluted after n-propylbenzene on the UIO-66 coated capillary column again shows reverse shape selectivity. However, much bulkier 1,3,5-trimethylbenzene eluted earlier than n-propylbenzene and iso-propylbenzene on the UIO-66 coated capillary column, exhibiting molecular sieving effect. The combination of reverse shape selectivity with molecular sieving effect makes the UIO-66 coated capillary column promising for the separation of structural isomers. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Monolithic column in gas chromatography. (United States)

    Kurganov, A


    Monolithic columns invented in chromatographic praxis almost 40 years ago gained nowadays a lot of popularity in separations by liquid chromatographic technique. At the same time, application of monolithic columns in gas chromatography is less common and only a single review published by Svec et al. covers this field of research. Since that time a lot of new findings on application and properties of monolithic columns in gas chromatography have been published in the literature deserving consideration and discussion. This review considers preparation of monolithic columns for GC, an impact of preparation conditions on column performance, optimization of separation conditions for GC analysis on monolithic columns and other important aspects of preparation and usage of monolithic capillary columns in GC. A final part of the review discusses the modern trends and possible applications in the future of capillary monolithic columns in GC. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Optimization of the gas chromatographic separations

    International Nuclear Information System (INIS)

    Gasco Sanchez, L.


    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

  12. Gas chromatographic separation of hydrogen isotopes on columns packed with alumina, modified alumina and sol-gel alumina. (United States)

    Naik, Y P; Gupta, N K; Pillai, K T; Rao, G A Rama; Venugopal, V


    The stationary phase of alumina adsorbents, prepared by different chemical processes, was used to study the separation behaviour of hydrogen isotopes. Three types of alumina, obtained by conventional hydroxide route alumina coated with silicon oxide and alumina prepared by internal gelation process (IGP), were used as packing material to study the separation of HT and T(2) in a mixture at various temperatures. The conventional alumina and silicon oxide coated alumina resolved HT and T(2) at 77K temperature with different retention times. The retention times on SiO(2) coated columns were found to be higher than those of other adsorbents. However, the column filled with IGP alumina was found to be ideal for the separation of HT and T(2) at 240 K. The peaks were well resolved in less than 5 min on this column. Copyright © 2011 Elsevier B.V. All rights reserved.

  13. Comparison of a jet separator and an open splitter as an interface between a multi-capillary gas chromatographic column and a time-of-flight mass spectrometer (United States)

    Pongpun; Mlynski; Crisp; Guilhaus


    A gas chromatographic/time-of-flight mass spectrometric (GC/TOFMS) interface is being developed for fast on-line analysis utilizing multi-capillary column technology. A variable gap-distance jet separator has been constructed and its performance compared with that of a commercially supplied post-column open splitter recommended for use between the multi-capillary column and a mass spectrometer. Both interfaces were found to be compatible with the GC/TOFMS system at high carrier gas flow-rates, facilitating high-speed and high-resolution separations. The systems were investigated and tested with a mixture of volatile organic compounds (VOCs) with molecular masses from 85 to 166: dichloromethane, toluene, m-dichlorobenzene, o-dichlorobenzene and tetrachloroethylene. The optimum tip-to-tip gap distance corresponding to the highest efficiency of the jet separator was found to be 0.030 mm for each compound at carrier gas flow-rates of 20, 40 and 60 ml min(-1) giving, in the ion source housing, ion gauge pressure readings of 1.6 x 10(-6), 5.0 x 10(-6) and 5.8 x 10(-6) mbar, respectively. The efficiency of the jet separator (10-30% yields) was significantly higher than that of the open splitter (6-9% yields). The observation that the open splitter did not provide a constant flow-rate to the ion source was not in agreement with the manufacturer's specifications. A method for measuring the gas flow-rates in all parts of the equipment is described. The correlation between yield in the jet separator and molecular mass for the heterogeneous set of compounds studied was found to be less linear than usually reported for homologous series of compounds in jet separator studies. The result suggests that the pressure conditions in the jet may be sufficient for the separation process to be partly controlled by diffusion rather than predominately by effusion. Copyright 2000 John Wiley & Sons, Ltd.

  14. Dual liquid and gas chromatograph system (United States)

    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.

  15. Fast gas chromatographic separation of biodiesel. (United States)

    Pauls, R E


    A high-speed gas chromatographic method has been developed to determine the FAME distribution of B100 biodiesel. The capillary column used in this work has dimensions of 20 m × 0.100 mm and is coated with a polyethylene glycol film. Analysis times are typically on the order of 4-5 min depending upon the composition of the B100. The application of this method to a variety of vegetable and animal derived B100 is demonstrated. Quantitative results obtained with this method were in close agreement with those obtained by a more conventional approach on a 100 m column. The method, coupled with solid-phase extraction, was also found suitable to determine the B100 content of biodiesel-diesel blends.

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

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    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: [Department of Forensic Medicine, Graduate School of Biomedical Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551 (Japan)


    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.

  17. Portable gas chromatograph-mass spectrometer (United States)

    Andresen, B.D.; Eckels, J.D.; Kimmons, J.F.; Myers, D.W.


    A gas chromatograph-mass spectrometer (GC-MS) is described for use as a field portable organic chemical analysis instrument. The GC-MS is designed to be contained in a standard size suitcase, weighs less than 70 pounds, and requires less than 600 watts of electrical power at peak power (all systems on). The GC-MS includes: a conduction heated, forced air cooled small bore capillary gas chromatograph, a small injector assembly, a self-contained ion/sorption pump vacuum system, a hydrogen supply, a dual computer system used to control the hardware and acquire spectrum data, and operational software used to control the pumping system and the gas chromatograph. This instrument incorporates a modified commercial quadrupole mass spectrometer to achieve the instrument sensitivity and mass resolution characteristic of laboratory bench top units. 4 figs.

  18. Suitability of selected chromatographic columns for analysis of fatty acids in dialyzed patients. (United States)

    Pazda, Magdalena; Stepnowski, Piotr; Sledzinski, Tomasz; Chmielewski, Michal; Mika, Adriana


    Gas chromatography-mass spectrometry is a preferred method for fatty acid (FA) analysis in biofluids from patients with metabolic diseases. Complex characteristics of FAs make their analysis particularly challenging. Selection of an appropriate chromatographic column is particularly important component of the process as it provides optimal separation and detection of possibly all FAs present in the sample. However, no accurate protocol for comparative evaluation of capillary columns for the analysis of whole serum FA profile in patients with chronic kidney disease (CKD) has been developed thus far. Therefore, in the present study four columns were examined to select the one providing optimal separation and determination of FA profiles in this group of patients. Moreover, serum FA profiles obtained with the selected column in CKD patients subjected to peritoneal dialysis and healthy controls were compared. Thirty-seven component FAME Mix and sera from CKD patients were used to optimize chromatographic conditions and to select the most appropriate column. The ZB-5 column turned out to be the most appropriate for the analysis of whole FA profile in CKD patients' sera. Then, this column was used to compare FA profiles in patients subjected to peritoneal dialysis and in healthy controls. The analysis demonstrated many abnormalities in the FA profile of CKD patients. Further studies involving larger groups of patients presenting with other stages of CKD are required to explain the impact of the disease progression on composition of serum FAs. Copyright © 2017 John Wiley & Sons, Ltd.

  19. A Gas Chromatographic System for the Detection of Ethylene Gas Using Ambient Air as a Carrier Gas. (United States)

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


    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.


    African Journals Online (AJOL)

    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 ...

  1. A Small-Scale Low-Cost Gas Chromatograph (United States)

    Gros, Natasa; Vrtacnik, Margareta


    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.

  2. Investigating the Effect of Column Geometry on Separation Efficiency using 3D Printed Liquid Chromatographic Columns Containing Polymer Monolithic Phases. (United States)

    Gupta, Vipul; Beirne, Stephen; Nesterenko, Pavel N; Paull, Brett


    Effect of column geometry on the liquid chromatographic separations using 3D printed liquid chromatographic columns with in-column polymerized monoliths has been studied. Three different liquid chromatographic columns were designed and 3D printed in titanium as 2D serpentine, 3D spiral, and 3D serpentine columns, of equal length and i.d. Successful in-column thermal polymerization of mechanically stable poly(BuMA-co-EDMA) monoliths was achieved within each design without any significant structural differences between phases. Van Deemter plots indicated higher efficiencies for the 3D serpentine chromatographic columns with higher aspect ratio turns at higher linear velocities and smaller analysis times as compared to their counterpart columns with lower aspect ratio turns. Computational fluid dynamic simulations of a basic monolithic structure indicated 44%, 90%, 100%, and 118% higher flow through narrow channels in the curved monolithic configuration as compared to the straight monolithic configuration at linear velocities of 1, 2.5, 5, and 10 mm s -1 , respectively. Isocratic RPLC separations with the 3D serpentine column resulted in an average 23% and 245% (8 solutes) increase in the number of theoretical plates as compared to the 3D spiral and 2D serpentine columns, respectively. Gradient RPLC separations with the 3D serpentine column resulted in an average 15% and 82% (8 solutes) increase in the peak capacity as compared to the 3D spiral and 2D serpentine columns, respectively. Use of the 3D serpentine column at a higher flow rate, as compared to the 3D spiral column, provided a 58% reduction in the analysis time and 74% increase in the peak capacity for the isocratic separations of the small molecules and the gradient separations of proteins, respectively.

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

    Energy Technology Data Exchange (ETDEWEB)

    Gasco Sanchez, L.


    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.

  4. Gas-liquid chromatography of bacterial fatty acids with a fused-silica capillary column.


    Moss, C W; Dees, S B; Guerrant, G O


    The use of flexible, fused-silica capillary column for gas-liquid chromatographic analysis of bacterial fatty acids is illustrated with Propionibacterium acnes, Propionibacterium shermanii, and a standard methyl ester mixture.

  5. FTIR gas chromatographic analysis of perfumes (United States)

    Diederich, H.; Stout, Phillip J.; Hill, Stephen L.; Krishnan, K.


    Perfumes, natural or synthetic, are complex mixtures consisting of numerous components. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques have been extensively utilized for the analysis of perfumes and essential oils. A limited number of perfume samples have also been analyzed by FT-IR gas chromatographic (GC-FTIR) techniques. Most of the latter studies have been performed using the conventional light pipe (LP) based GC-FTIR systems. In recent years, cold-trapping (in a matrix or neat) GC-FTIR systems have become available. The cold-trapping systems are capable of sub-nanogram sensitivities. In this paper, comparison data between the LP and the neat cold-trapping GC- FTIR systems is presented. The neat cold-trapping interface is known as Tracer. The results of GC-FTIR analysis of some commercial perfumes is also presented. For comparison of LP and Tracer GC-FTIR systems, a reference (synthetic) mixture containing 16 major and numerous minor constituents was used. The components of the mixture are the compounds commonly encountered in commercial perfumes. The GC-FTIR spectra of the reference mixture was obtained under identical chromatographic conditions from an LP and a Tracer system. A comparison of the two sets of data thus generated do indeed show the enhanced sensitivity level of the Tracer system. The comparison also shows that some of the major components detected by the Tracer system were absent from the LP data. Closer examination reveals that these compounds undergo thermal decomposition on contact with the hot gold surface that is part of the LP system. GC-FTIR data were obtained for three commercial perfume samples. The major components of these samples could easily be identified by spectra search against a digitized spectral library created using the Tracer data from the reference mixture.

  6. Gas-Chromatographic Determination Of Water In Freon PCA (United States)

    Melton, Donald M.


    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.

  7. [The gas chromatographic analysis of volatile compounds on the compact MKhP chromatograph]. (United States)

    Krasnova, R R; Ianovskiĭ, S M


    Methods of analysis of biological specimens, alcohol beverages, and technological liquids in columns with standard adsorbents carbopaque B and C with carbowax 20M, widely used abroad, are described and examples of analyses presented. A special portable chromatographer (MCP) with flame ionization detector has been designed. It is intended for analysis of volatile organic compounds (alcohols, carbohydrates, organochlorine compounds, glycols, esters, etc.) in columns of different polarity. The system of processing of chromatographic findings permits a quantitative analysis of complex chromatograms and automated identification of substances in biological samples by using the available database.

  8. Isolation and purification of plant secondary metabolites using column-chromatographic technique

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    Vivek K. Bajpai


    Full Text Available Chromatographic techniques have significant role in natural products chemistry as well as contribute dramatically in the discovery of novel and innovative compounds of pharmaceutical and biomedical importance. This study focused on step-by-step visual demonstration of fractionation and isolation of biologically active plant secondary metabolites using column-chromatographic techniques. Isolation of bioactive compounds using column-chromatographic involves: a Preparation of sample; b Packing of column; c Pouring of sample into the column; d Elution of fractions; and e Analysis of each fractions using thin layer chromatography. However, depending on nature of research, compounds can be further purified using high performance liquid chromatography (HPLC, and nuclear magnetic resonance (NMR spectral analyses.

  9. 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 (United States)

    Furlong, E.T.; Vaught, D.G.; Merten, L.M.; Foreman, W.T.; Gates, Paul M.


    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.

  10. Temperature programmable microfabricated gas chromatography column (United States)

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


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

  11. Use of laminar chromatographic methods for determination of separation conditions in column extraction chromatography

    International Nuclear Information System (INIS)

    Ghersini, G.; Cerrai, E.


    Possibilities of using laminar chromatographic methods (paper and thin-layer chromatography) to determine optimal separation conditions in column extraction chromatography are analysed. Most of the given laminar methods are presented as Rf-spectra, i.e. as dependences of Rf found experimentally on eluating solution component concentration. Interrelation between Rf and distribution coefficients of corresponding liquid extraction systems and retention volumes of chromatographic columns is considered. Literature data on extraction paper and thin-layer chromatography of elements with various immovable phases are presented

  12. Simple gas chromatographic system for analysis of microbial respiratory gases (United States)

    Carle, G. C.


    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.

  13. Approaches to characterise chromatographic column performance based on global parameters accounting for peak broadening and skewness. (United States)

    Baeza-Baeza, J J; Pous-Torres, S; Torres-Lapasió, J R; García-Alvarez-Coque, M C


    Peak broadening and skewness are fundamental parameters in chromatography, since they affect the resolution capability of a chromatographic column. A common practice to characterise chromatographic columns is to estimate the efficiency and asymmetry factor for the peaks of one or more solutes eluted at selected experimental conditions. This has the drawback that the extra-column contributions to the peak variance and skewness make the peak shape parameters depend on the retention time. We propose and discuss here the use of several approaches that allow the estimation of global parameters (non-dependent on the retention time) to describe the column performance. The global parameters arise from different linear relationships that can be established between the peak variance, standard deviation, or half-widths with the retention time. Some of them describe exclusively the column contribution to the peak broadening, whereas others consider the extra-column effects also. The estimation of peak skewness was also possible for the approaches based on the half-widths. The proposed approaches were applied to the characterisation of different columns (Spherisorb, Zorbax SB, Zorbax Eclipse, Kromasil, Chromolith, X-Terra and Inertsil), using the chromatographic data obtained for several diuretics and basic drugs (beta-blockers). Copyright (c) 2010 Elsevier B.V. All rights reserved.

  14. High Performance Liquid Chromatographic Analysis of Phytoplankton Pigments Using a C16-Amide Column (United States)

    A reverse-phase high performance liquid chromatographic (RP-HPLC) method was developed to analyze in a single run, most polar and non-polar chlorophylls and carotenoids from marine phytoplankton. The method is based on a RP-C16-Amide column and a ternary gradient system consistin...

  15. Comparing monolithic and fused core HPLC columns for fast chromatographic analysis of fat-soluble vitamins. (United States)

    Kurdi, Said El; Muaileq, Dina Abu; Alhazmi, Hassan A; Bratty, Mohammed Al; Deeb, Sami El


    HPLC stationary phases of monolithic and fused core type can be used to achieve fast chromatographic separation as an alternative to UPLC. In this study, monolithic and fused core stationary phases are compared for fast separation of four fat-soluble vitamins. Three new methods on the first and second generation monolithic silica RP-18e columns and a fused core pentafluoro-phenyl propyl column were developed. Application of three fused core columns offered comparable separations of retinyl palmitate, DL-α-tocopheryl acetate, cholecalciferol and menadione in terms of elution speed and separation efficiency. Separation was achieved in approx. 5 min with good resolution (Rs > 5) and precision (RSD ≤ 0.6 %). Monolithic columns showed, however, a higher number of theoretical plates, better precision and lower column backpressure than the fused core column. The three developed methods were successfully applied to separate and quantitate fat-soluble vitamins in commercial products.

  16. Comparing monolithic and fused core HPLC columns for fast chromatographic analysis of fat-soluble vitamins

    Directory of Open Access Journals (Sweden)

    Kurdi Said El


    Full Text Available HPLC stationary phases of monolithic and fused core type can be used to achieve fast chromatographic separation as an alternative to UPLC. In this study, monolithic and fused core stationary phases are compared for fast separation of four fat-soluble vitamins. Three new methods on the first and second generation monolithic silica RP-18e columns and a fused core pentafluoro-phenyl propyl column were developed. Application of three fused core columns offered comparable separations of retinyl palmitate, DL-α-tocopheryl acetate, cholecalciferol and menadione in terms of elution speed and separation efficiency. Separation was achieved in approx. 5 min with good resolution (Rs > 5 and precision (RSD ≤ 0.6 %. Monolithic columns showed, however, a higher number of theoretical plates, better precision and lower column backpressure than the fused core column. The three developed methods were successfully applied to separate and quantitate fat-soluble vitamins in commercial products.

  17. The employment of cellulose pressure columns for the chromatographic separation of radioactive nuclides

    International Nuclear Information System (INIS)

    Meier, H.; Zimmerhackl, E.; Unger, E.; Zeitler, G.; Albrecht, W.; Boesche, D.; Hecker, W.; Menge, P.


    A study was made of the separation properties of cellulose pressure columns operating at a slight over-pressure of around 1 atmosphere, with respect to the length of the column packing, the flow rate, and the load. The optimal separation stage heights of the columns are situated at H=0.16 mm. Since as a consequence of the favorable separation stage heights observed at column lengths of 3 to 7 cm, separation stage numbers of 200 to 400 are attained, and hence it is possible to attain separations within several minutes with flow rates of 1 ml/min. The choice of the mobile phase is made easier by the fact that paper chromatographic Rsub(f)-values can be transferred to the cellulose pressure column with the aid of a transfer function. (author)

  18. New portable micro gas chromatograph for environmental analysis

    Energy Technology Data Exchange (ETDEWEB)

    Overton, E.B.; Carney, K.R.; Dharmasena, H.P.; Mainga, A.M.; Ehrmann, U. [Louisiana State Univ., Baton Rouge, LA (United States). Inst. for Environmental Studies


    Efforts directed at developing a truly portable method for the analysis of semivolatile compounds have led to the construction and testing of a new generation of micro-GC instrumentation. Building on the successful application of microbore GC columns for in-field analysis of volatile organic compounds, the instrument development group at the LSU-Institute for Environmental Studies has developed a hand portable GC capable of analyzing samples containing compounds with retention indices (100% dimethylpolysiloxane column) up to at least 2,000 in less than 4 minutes, using less than 50 watts (peak) of electrical power. In addition to the ability to analyze semivolatile compounds, the chromatograph is capable of analyzing volatile organics competitively with the most sophisticated of the current commercial portable GCs. The presentation will evaluate chromatographic performance of the instrument at its latest stage of development and demonstrate some applications to environmental analysis using the prototype instrument.

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

    Indian Academy of Sciences (India)

    The lower detection limit was 10 ng/ml in 5 ml of urine. The conjugated steroids from urine were centrifuged to 2,430 for 10 min, the supernatant solution passed through Amberlite XAD-2 column and the steroids eluted fraction esterified by using MSTFA and TMSI. The rate of metabolism and urinary excretion seem to be ...

  20. Evaluation of chromatographic columns packed with semi- and fully porous particles for benzimidazoles separation. (United States)

    Gonzalo-Lumbreras, Raquel; Sanz-Landaluze, Jon; Cámara, Carmen


    The behavior of 15 benzimidazoles, including their main metabolites, using several C18 columns with standard or narrow-bore diameters and different particle size and type were evaluated. These commercial columns were selected because their differences could affect separation of benzimidazoles, and so they can be used as alternative columns. A simple screening method for the analysis of benzimidazole residues and their main metabolites was developed. First, the separation of benzimidazoles was optimized using a Kinetex C18 column; later, analytical performances of other columns using the above optimized conditions were compared and then individually re-optimized. Critical pairs resolution, analysis run time, column type and characteristics, and selectivity were considered for chromatographic columns comparison. Kinetex XB was selected because it provides the shortest analysis time and the best resolution of critical pairs. Using this column, the separation conditions were re-optimized using a factorial design. Separations obtained with the different columns tested can be applied to the analysis of specific benzimidazoles residues or other applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Influence of pressure on the properties of chromatographic columns. II. The column hold-up volume. (United States)

    Gritti, Fabrice; Martin, Michel; Guiochon, Georges


    The effect of the local pressure and of the average column pressure on the hold-up column volume was investigated between 1 and 400 bar, from a theoretical and an experimental point of view. Calculations based upon the elasticity of the solids involved (column wall and packing material) and the compressibility of the liquid phase show that the increase of the column hold-up volume with increasing pressure that is observed is correlated with (in order of decreasing importance): (1) the compressibility of the mobile phase (+1 to 5%); (2) in RPLC, the compressibility of the C18-bonded layer on the surface of the silica (+0.5 to 1%); and (3) the expansion of the column tube (columns packed with the pure Resolve silica (0% carbon), the derivatized Resolve-C18 (10% carbon) and the Symmetry-C18 (20% carbon) adsorbents, using water, methanol, or n-pentane as the mobile phase. These solvents have different compressibilities. However, 1% of the relative increase of the column hold-up volume that was observed when the pressure was raised is not accounted for by the compressibilities of either the solvent or the C18-bonded phase. It is due to the influence of the pressure on the retention behavior of thiourea, the compound used as tracer to measure the hold-up volume.

  2. Comparison of twin-cell centrifugal partition chromatographic columns with different cell volume. (United States)

    Goll, Johannes; Audo, Gregoire; Minceva, Mirjana


    Two twin-cell centrifugal partition chromatographic columns (SCPC 250 and SCPE-250-BIO, Armen Instrument, France) with the same column volume but different cell size and number were compared in terms of stationary phase retention and column efficiency. The columns were tested with two types of solvent systems: a commonly used organic solvent based biphasic system from the ARIZONA solvent system family and a polymer/salt based aqueous two phase system (ATPS). The efficiency of the columns was evaluated by pulse injection experiments of two benzenediols (pyrocatechol and hydroquinone) in the case of the ARIZONA system and a protein mixture (myoglobin and lysozyme) in the case of the ATPS. As result of high stationary phase retention, the column with the lower number of larger twin-cells (SCPE-250-BIO) is suitable for protein separations using ATPS. On the other hand, due to higher column efficiency, the column with the greater number of smaller cells (SCPC 250) is superior for batch elution separations performed with standard liquid-liquid chromatography organic solvent based biphasic systems. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Chemical characterization of Brickellia cavanillesii (Asteraceae) using gas chromatographic methods


    Eshiet, Etetor R; Zhu, Jinqiu; Anderson, Todd A; Smith, Ernest E


    A methanol extract of lyophilized Brickellia cavanillesii was quantitatively analyzed using gas chromatographic (GC) techniques. The chromatographic methods employed were (i) GC-flame ionization detector (GC-FID), (ii) GC-mass spectrometry (GC-MS), and (iii) purge and trap GC-MS (P&T GC-MS). Thirteen compounds were identified with a quality match of 90% and above using GC-MS. The compounds were (1) Cyclohexene, 6-ethenyl-6-methyl-1-(1-methylethyl)-3-(1-methylethylidene)-, (S)-; (2) Bicylo (2....

  4. Gas chromatographic sensing on an optical fiber by mode-filtered light detection. (United States)

    Bruckner, C A; Synovec, R E


    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.

  5. Gas chromatographic determination of calcium propionate added as preservative to bread. (United States)

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


    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%.

  6. Characterization of a chromatographic column for the production of 90Sr

    International Nuclear Information System (INIS)

    Fornaciari Iljadica, Maria C.; Furnari, Juan C.; Cohen, Isaac M.


    The experiments carried out with the objective of developing a method for 90 Sr production, associated to that of 99 Mo from 235 U fission, which is routinely performed at Centro Atomico Ezeiza, Comision Nacional de Energia Atomica, are described. The project consists of strontium separation from a nitric solution containing uranium and a variety of fission products, by retention and subsequent elution in selective chromatographic columns. Both these columns and the conditions for their use in a routine production process have been characterized. The experiments show good Sr-Ba separation, high concentration of activity for the obtained 90 Sr, and minimal losses; in addition, the non-existence of significant radiation damage, as a limiting factor of the separative capacity of the columns, has been verified. (author)

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

    International Nuclear Information System (INIS)

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


    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

  8. Graphitic carbon nitride nanofibers in seaweed-like architecture for gas chromatographic separations. (United States)

    Zheng, Yunzhong; Han, Qing; Qi, Meiling; Qu, Liangti


    Seaweed-like graphitic carbon nitride (g-C 3 N 4 ) has a unique porous architecture composed of interlocking g-C 3 N 4 nanofibers (NF-C 3 N 4 ) with much higher surface area than bulk g-C 3 N 4 and shows good potential in separation science. This work investigated the separation performance of NF-C 3 N 4 as stationary phase for capillary gas chromatographic (GC) separations. The NF-C 3 N 4 column exhibits weak polarity and high column efficiency of 4728 plates/m for n-dodecane. Importantly, it displays good separation performance for a wide range of analytes and shows different retention behaviors from the bulk g-C 3 N 4 column and commercial HP-5MS column with 5% phenylpolysiloxane. Particularly, it shows high resolving capability for both aliphatic and aromatic isomers. In addition, NF-C 3 N 4 column has high thermal stability up to 280°C and good separation repeatability with relative standard deviation (RSD) values in the range of 0.29-0.61% for intra-day, 0.56-1.1% for inter-day and 2.0-4.9% for between-column, respectively. Moreover, it was applied for the determination of isomer impurities in real samples, showing good potential in GC applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Comparison of thin layer chromatographic and gas chromatographic determination of propoxur residues in a cocoa ecosystem

    International Nuclear Information System (INIS)

    Yeboah, P.O.; Lowor, S.; Akpabli, C.K.


    The fate of propoxur in a cocoa ecosystem has been studied using thin layer chromatographic (TLC) and gas chromatographic (GC) methods. Residues of propoxur as determined by both TLC and GC were not significantly different. TLC analysis of propoxur residues in soil, cocoa leaves and pods did not require any rigorous cleanup since residues measured from cleaned extracts and without cleanup were not significantly different. The residue levels of propoxur in the soil were found to decrease rapidly and, by the 21st day, none was detected in the topsoil (0-15 cm). Evidence of leaching of propoxur residues in the soil has also been demonstrated. The amount left in the top soil after the first seven days were 27%, 23% and 24% of the initial one as determined by the TLC without cleanup, TLC with cleanup and GLC, respectively. No propoxur residue was detected in topsoil 21 days after spraying. About 38% of pesticides detected on the cocoa pod on the day of treatment remained on the pod seven days after treatment. The residue detected on the leaves on the day of treatment was higher than that in or on the soil. This decreased rapidly to 1.7% in 21 days compared to 16% for the soil and 23% for the pod. (author)

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

    African Journals Online (AJOL)



    Aug 27, 2010 ... Key words: Acetone-butanol-ethanol fermentation, column temperature programme, gas chromatography, sweet sorghum juice. ..... dehydration of aqueous butanol solutions: a comparison of flux vs. permeance, separation factor vs. selectivity. J. Membrane Sci. 245: 199-210. Wang F, Kashket S, Kashket ...

  11. Multiplex gas chromatography: an alternative concept for gas chromatographic analysis of planetary atmospheres (United States)

    Valentin, J. R.


    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

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

    International Nuclear Information System (INIS)

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


    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

  13. Evaluation of the phase ratio for three C18 high performance liquid chromatographic columns. (United States)

    Caiali, Edvin; David, Victor; Aboul-Enein, Hassan Y; Moldoveanu, Serban C


    For a chromatographic column, phase ratio Φ is defined as the ratio between the volume of the stationary phase Vst and the void volume of the column V0, and it is an important parameter characterizing the HPLC process. Although apparently simple, the evaluation of Φ presents difficulties because there is no sharp boundary between the mobile phase and the stationary phase. In addition, the boundary depends not only on the nature of the stationary phase, but also on the composition of the mobile phase. In spite of its importance, phase ratio is seldom reported for commercially available HPLC columns and the data typically provided by the vendors about the columns do not provide key information that would allow the calculation of Φ based on Vst and V0 values. A different procedure for the evaluation of Φ is based on the following formula: log k'j=a log Kow,j+log Φ, where k'j is the retention factor for a compound j that must be a hydrocarbon, Kow,j is the octanol/water partition coefficient, and a is a proportionality constant. Present study describes the experimental evaluation of Φ based on the measurement of k'j for the compounds in the homologous series between benzene and butylbenzene for three C18 columns: Gemini C18, Luna C18 both with 5 μm particles, and a Chromolith Performance RP-18. The evaluation was performed for two mobile phase systems at different proportions of methanol/water and acetonitrile/water. The octanol/water partition coefficients were obtained from the literature. The results obtained in the study provide further support for the new procedure for the evaluation of phase ratio. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Peak distortion in the column liquid chromatographic determination of omeprazole dissolved in borax buffer. (United States)

    Arvidsson, T; Collijn, E; Tivert, A M; Rosén, L


    Injection of a sample containing omeprazole dissolved in borax buffer (pH 9.2) into a reversed-phase liquid chromatographic system consisting of a mixture of acetonitrile and phosphate buffer (pH 7.6) as the mobile phase and a C18 surface-modified silica as the solid phase resulted under special conditions in split peaks of omeprazole. The degree of peak split and the retention time of omeprazole varied with the concentration of borax in the sample solution and the ionic strength of the mobile phase buffer as well as with the column used. Borax is eluted from the column in a broad zone starting from the void volume of the column. The retention is probably due to the presence of polyborate ions. The size of the zone varies with the concentration of borax in the sample injected. In the borax zone the pH is increased compared with the pH of the mobile phase, and when omeprazole (a weak acid) is co-eluting in the borax zone its retention is affected. In the front part and in the back part of the borax zone, pH gradients are formed, and these gradients can induce the peak splitting. When the dissolving medium is changed to a phosphate buffer or an ammonium buffer at pH 9 no peak distortion of omeprazole is observed.

  15. Ion chromatographic determination of fluoride and chloride in UO2 using microbore anion exchange columns

    International Nuclear Information System (INIS)

    Kelkar, Anoop; Meena, D.L.; Das, D.K.; Behere, P.G.; Mohd Afzal


    Chemical characterization of nuclear fuels is required to ensure that nuclear fuel meets the technical specifications of the fuel. Trace non- metallic impurities like Cl and F is important as they affect clad corrosion. Their effect is more severe in presence of moisture. Chlorine and Fluorine is routinely analysed by ion selective electrode or conventional ion chromatography after pyrohydrolyzing the sample in moist O 2 atmosphere at 950°. Both the technique generates large quantity of liquid waste. Generally 1 ml/min flow rate required for the separation of F - and Cl - in conventional ion-chromatographic separation of F - and Cl - on 4.6- 4.0 mm id analytical column. The waste produced per sample injection is ∼ 30-40 ml with suppressed conductivity detection in ion chromatography. There is a need to reduce this analytical waste in analyzing the radioactive samples for the determination of F - and Cl - . Waste generation could be effectively reduced by using microbore anion exchange analytical column. Present paper describe the use of Metrosep A Supp 16 - 100/2.0 column with Na 2 CO 3 +NaOH mobile phase for the determination of F - and Cl - in UO 2 samples using suppressed conductivity detection

  16. Analysis of linear two-dimensional general rate model for chromatographic columns of cylindrical geometry. (United States)

    Qamar, Shamsul; Uche, David U; Khan, Farman U; Seidel-Morgenstern, Andreas


    This work is concerned with the analytical solutions and moment analysis of a linear two-dimensional general rate model (2D-GRM) describing the transport of a solute through a chromatographic column of cylindrical geometry. Analytical solutions are derived through successive implementation of finite Hankel and Laplace transformations for two different sets of boundary conditions. The process is further analyzed by deriving analytical temporal moments from the Laplace domain solutions. Radial gradients are typically neglected in liquid chromatography studies which are particularly important in the case of non-perfect injections. Several test problems of single-solute transport are considered. The derived analytical results are validated against the numerical solutions of a high resolution finite volume scheme. The derived analytical results can play an important role in further development of liquid chromatography. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Mixture designs for exploring class diversity and metabolite fingerprinting: an efficient column chromatographic strategy. (United States)

    Soares, Daniely Xavier; Scarminio, Ieda S; Bruns, Roy Edward


    The effects of four solvents, hexane, dichloromethane, ethyl acetate, methanol, and their mixtures on the separation of metabolites in crude extracts of Erythrina speciosa Andrews leaves were investigated using two strategies for open column chromatography. The classical extraction procedure was compared with mobile phases prepared according to a mixture design in order to explore the effects of solvent interactions on metabolite separations. Principal component analysis was used to compare the UV spectra obtained from RP-HPLC-DAD and to estimate the number of independent factors contained in the chromatographic data of the extracts. The results showed that, in addition to solvent polarity, solvent mixtures play an important role in metabolite separation. When pure solvents are used, larger groups of similar spectra are observed in the factor analysis score graphs indicating the same or a limited number of metabolite classes. In contrast solvent mixtures produced score graphs with a larger number of clusters indicating greater metabolic diversity. Besides resulting in more peaks than the pure solvents the chromatographic data of the design mixtures resulted in larger numbers of significant principal components confirming the greater chemical diversity of their extracts. Thus, if the objective of an analysis is to obtain metabolites of the same class, one should use pure solvents. On the other hand, binary and ternary solvent mixtures are recommended for more efficient investigations of class diversity and richer metabolite fingerprints. Copyright © 2011 Elsevier B.V. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Xiao-Liang Wang


    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.

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

    International Nuclear Information System (INIS)

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


    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)

  20. [Retention behavior of solutes on liquid chromatographic column packed with dynamically modified zirconia]. (United States)

    Zhang, Q; Feng, Y; Yan, L; Da, S


    Zirconia was dynamically modified with stearic acid, beta-cyclodextrin and sodium dodecylsulfonate, separately, to form liquid chromatographic packings. The chromatographic behaviors of aromatic hydrocarbons, acidic compounds (phenol, nitrophenols and benzoic acids) and basic compounds (aniline, nitroanilines and toluidines) were investigated on these modified zirconia packings with a mixture of methanol/water as the mobile phase. On stearic acid modified zirconia, aromatic hydrocarbons and the basic compounds exhibit symmetrical peaks. The retention time of these solutes decreases with increasing the concentration of methanol in the mobile phase. When the mobile phases with stearic acid were used, the retention time of these solutes has a maximum with variation of stearic acid concentration (0-1.0 mmol/L) in the mobile phase. However, the acidic compounds such as nitrophenols and benzoic acids are strongly adsorbed and can not be eluted from the column with the mobile phases. No leaking of stearic acid on the modified zirconia was found after 3000 column volumes of the methanol/water mobile phase were used. The results showed that the stearic acid modified zirconia can be used as a stationary phase for reversed-phase liquid chromatography. On beta-cyclodextrin modified zirconia, aromatic hydrocarbons and basic compounds exhibit shorter retention time than those on the stearic acid modified zirconia under the same mobile phase composition, however, nitrophenols can be eluted but give unsymmetrical peaks. On sodium dodecylsulfonate modified zirconia packings, the basic compounds can not be retarded; Aromatic hydrocarbons and acidic compounds exhibit short retention time. The results can be ascribed to the weak adsorption of sodium dodecylsulfonate on the zirconia.

  1. A bubble-based microfluidic gas sensor for gas chromatographs. (United States)

    Bulbul, Ashrafuzzaman; Kim, Hanseup


    We report a new proof-of-concept bubble-based gas sensor for a gas chromatography system, which utilizes the unique relationship between the diameters of the produced bubbles with the gas types and mixture ratios as a sensing element. The bubble-based gas sensor consists of gas and liquid channels as well as a nozzle to produce gas bubbles through a micro-structure. It utilizes custom-developed software and an optical camera to statistically analyze the diameters of the produced bubbles in flow. The fabricated gas sensor showed that five types of gases (CO2, He, H2, N2, and CH4) produced (1) unique volumes of 0.44, 0.74, 1.03, 1.28, and 1.42 nL (0%, 68%, 134%, 191%, and 223% higher than that of CO2) and (2) characteristic linear expansion coefficients (slope) of 1.38, 2.93, 3.45, 5.06, and 5.44 nL/(kPa (μL s(-1))(-1)). The gas sensor also demonstrated that (3) different gas mixture ratios of CO2 : N2 (100 : 0, 80 : 20, 50 : 50, 20 : 80 and 0 : 100) generated characteristic bubble diameters of 48.95, 77.99, 71.00, 78.53 and 99.50 μm, resulting in a linear coefficient of 10.26 μm (μL s(-1))(-1). It (4) successfully identified an injection (0.01 μL) of pentane (C5) into a continuous carrier gas stream of helium (He) by monitoring bubble diameters and creating a chromatogram and demonstrated (5) the output stability within only 5.60% variation in 67 tests over a month.

  2. Graphitic carbon nitride as high-resolution stationary phase for gas chromatographic separations. (United States)

    Zheng, Yunzhong; Qi, Meiling; Fu, Ruonong


    This work presents the first example of utilization of graphitic carbon nitride (g-C3N4) as stationary phase for capillary gas chromatographic (GC) separations. The statically coated g-C3N4 column showed the column efficiencies of 3760 plates/m and weak polarity. Its resolving capability and retention behaviours were investigated by using the Grob test mixture, and mixtures of diverse types of analytes, and structural and positional isomers. The results showed superior separation performance of the g-C3N4 stationary phase for some critical analytes and preferential retention for aromatic analytes. Specifically, it exhibited high-resolution capability for aromatic and aliphatic isomers such as methylnaphthalenes and dimethylnaphthalenes, phenanthrene and anthracene and alkane isomers. In addition, g-C3N4 column showed excellent thermal stability up to 280°C and good repeatability with relative standard deviation (RSD) values less than 0.09% for intra-day, below 0.23% for inter-day and in the range of 1.9-8.4% for between-column, respectively. The advantageous separation performance shows the potential of g-C3N4 and related materials as stationary phase in GC and other separation technologies. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Gas chromatographic measurement in water-steam circuits

    International Nuclear Information System (INIS)

    Zschetke, J.; Nieder, R.


    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

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

    Energy Technology Data Exchange (ETDEWEB)

    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)


    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.


    Directory of Open Access Journals (Sweden)

    Dwi Retno Nurotul Wahidiyah


    Full Text Available Application of activated zeolite (ZAA as molecular sieve to separate compounds of coal tar from vaccum fractional distillation, have been done. The size of zeolite was 10-20 mesh and used as solid phase in column chromatography with length of 30 cm. The first step of the research was coal pyrolisis and the product (tar was distillated by fractional column and vaccum system at reduced pressure 44 cmHg and maximum temperature at 200 oC. The distillate from this procedure was flowed to the column chromatography of zeolite (ZAA. The compound absorbed by zeolite was eluted with varying solvents, i.e: CCl4, acetone and ethanol. Each fraction was then analyzed by gas chromatography. The results showed, zeolite have a capability to separate the compounds of tar and it tends to absorb medium hydrocarbon. The nonpolar eluent [CCl4] gives the better result in eluting tar compound than polar (ethanol or medium polar eluents (acetone.   Keywords: zeolite, coal tar, column chromatography

  6. [Preparation of divinylbenzene polymer monolithic columns and their applications in gas chromatography]. (United States)

    Tian, Hongxu; Li, Yun; Chen, Jiping


    The preparation of divinylbenzene polymer monolithic columns and their applications in gas chromatography (GC) are discussed. Based on liquid chromatographic (LC) monolithic columns, the high-permeable monolithic columns can be applied in GC through changing the ratio of toluene and dodecanol. It is shown that the monolithic columns possess fastness configuration and good mechanical intensity via the bonding of 3-(trimethoxysilyl) propyl methacrylate (TMP) to the capillary wall and the polymerization of the crosslinker itself. Compared with a commercial porous layer open tube (PLOT) column and a PEG-20M column, the monolithic columns demonstrate good performance in the analysis of low carbon alcohols in water, the analysis of mixed solvents and the standard liquor sample. In the mixed solvents, the peak symmetries of alcohols, ketones, esters and aromatics precede those on the PLOT column. The separation of methanol, acetaldehyde and ethyl acetate in the standard liquor sample on the monolithic column is much more convenient than that on PEG-20M columns.

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

    International Nuclear Information System (INIS)

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


    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.)

  8. Ion Chromatographic Method with Post-Column Fuchsin Reaction for Measurement of Bromate in Chlorinated Water

    Directory of Open Access Journals (Sweden)

    Homer C. Genuino


    Full Text Available An ion chromatographic method that employs a post-column reaction with fuchsin and spectrophotometric detection was optimized for measuring bromate (BrO3- in water. BrO3- is converted to Br2 by sodium metabisulfite and then reacted with acidic fuchsin to form a red-colored product that strongly absorbs at 530 nm. The reaction of BrO3- and fuchsin reagent is optimum at pH 3.5 and 65 oC. The method has a limit of quantitation of 4.5 µg L-1 and is linear up to 150 µg L-1 BrO3-. Recoveries from spiked samples were high ranging from 95 to 102 % using external standard calibration and 87 to 103 % using standard addition method. Intra-batch and inter-batch reproducibility studies of the method resulted to RSD values ranging from 0.62 to 2.01 % and percent relative error of 0.12 to 2.94 % for BrO3- concentrations of 10 µg L-1 and 50 µg L-1. This method is free of interferences from common inorganic anions at levels typically found in chlorinated tap drinking water without preconcentration. The optimized method can be applied to trace analysis of bromate in chlorinated tap drinking water samples.

  9. Chromatographic separations of stereoisomers

    Energy Technology Data Exchange (ETDEWEB)

    Souter, R.W.


    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.

  10. Liquid chromatographic determination of fumonisins B1 and B2 in corn samples after reusable immunoaffinity column clean-up

    Directory of Open Access Journals (Sweden)



    Full Text Available The possibility of the liquid chromatographic determination of fumonisins B1 (FB1 andB2 (FB2 in corn samples with a reused immunoaffinity column (IMA for the clean-up of the samples was investigated. After optimization of the chromatographic determination of FB1 and FB2 derivatized with o-phthaldialdehyde- 2-mercaptoethanol, the efficiency of the clean-up of spiked corn extracts with reuse of the IMA columns was studied, both with and without column regeneration. It was found that the IMAcolumn, designated for single-use only, can be used at least five times without regeneration and additional five times after regeneration. Regeneration consists of leaving the phosphate buffer saline solution on the column for one day at 4 ºC. The efficiency of the columns was tested by determining the recovery of FB1 and FB2, as well as the reproducibility of the determinations. The mean recoveries of FB1 and FB2 from corn spiked with FB1 at 1.0 mg/g and with FB2 at 0.5 mg/g (on the basis of 10 measurements were 88.7%(RSD 10.2% and 90.5%(RSD 6.1 %, respectively.

  11. Behavior of short silica monolithic columns in high pressure gas chromatography. (United States)

    Maniquet, Adrien; Bruyer, Nicolas; Raffin, Guy; Baco-Antoniali, Franck; Demesmay, Claire; Dugas, Vincent; Randon, Jérôme


    In order to analyze light hydrocarbons mixtures with silica monolithic columns, a conventional gas chromatograph was modified to work with carrier gas pressure as high as 60bar. To understand hydrodynamic flow and retention with short columns (less than 30cm), special attention was required due to the temperature difference between the oven area and the FID detector which contain a significant length of the column. Efficiency and selectivity using various carrier gases (helium, nitrogen and carbon dioxide) at different inlet pressure for different oven temperature were studied. Carrier gas nature was a very significant parameter: on one side, linked to adsorption mechanism for gases like nitrogen and carbon dioxide onto the stationary phase modifying retention and selectivity, on the other side in relation to the minimum theoretical plate height which was as low as 15μm (66 000 platem(-1)) using carbon dioxide as carrier gas. The chromatographic system was then used to separate methane, ethane, ethylene, acetylene, propane, cyclopropane, and butane in less than 30s. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Recent Advances in Water Analysis with Gas Chromatograph Mass Spectrometers (United States)

    MacAskill, John A.; Tsikata, Edem


    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. Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution. (United States)

    Musashi, Masaaki; Oi, Takao; Matsuo, Motoyuki; Nomura, Masao


    Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25 degrees C, using 0.1 mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at the atmospheric pressure at 25 degrees C with the boron concentration of 10mM, but were larger than the values under the same condition with much higher concentration of 100 and 501 mM. Calculations based on the theory of isotope distribution between two phases estimated that 21% (5 MPa) and 47% (17 MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)(3)-form, instead of in the four-coordinated B(OH)(4)-form, at high pressures even with a very diluted boric acid solution. We discussed the present results by introducing (1) hydration and (2) a partial molar volume difference between isotopic molecules. Borate may have been partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Instead, it may be possible that the difference in the isotopic partial molar volume difference between B(OH)(3) and B(OH)(4)(-) caused the S value to decrease with increasing pressure.

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

    Energy Technology Data Exchange (ETDEWEB)

    Read, Douglas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sillerud, Colin Halliday [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


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

  15. The counterintuitive role of extra-column volume in the determination of column efficiency and scaling of chromatographic processes

    NARCIS (Netherlands)

    Schultze-Jena, A.; Boon, M.A.; Bussmann, P.J.T.; Janssen, A.E.M.; Padt, A. van der


    In industrial liquid separation processes chromatography often has a key function in the optimization of yield and purity. For the design of an industrial system, chromatographic processes are generally simulated using mathematical models, tested and optimized at laboratory level, and then scaled up

  16. The counterintuitive role of extra-column volume in the determination of column efficiency and scaling of chromatographic processes

    NARCIS (Netherlands)

    Schultze-Jena, A.; Boon, M.A.; Bussmann, P.J.Th.; Janssen, A.E.M.; Padt, van der A.


    In industrial liquid separation processes chromatography often has a key function in the optimization of yield and purity. For the design of an industrial system, chromatographic processes are generally simulated using mathematical models, tested and optimized at laboratory level, and then scaled

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

    International Nuclear Information System (INIS)

    Mott, J.


    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

  18. Miniaturized MEMS-Based Gas Chromatograph for High Inertial Loads Associated with Planetary Missions, Phase I (United States)

    National Aeronautics and Space Administration — Thorleaf Research, Inc. proposes to develop a rugged, miniaturized, low power MEMS-based gas chromatograph (GC) capable of handling the high inertial loads...

  19. Design and Performance of a Gas Chromatograph for Automatic Monitoring of Pollutants in Ambient Air (United States)

    Villalobos, R.; Stevens, D.; LeBlanc, R.; Braun, L.


    In recent years, interest in air pollution constituents has focused on carbon monoxide and hydrocarbons as prime components of polluted air. Instrumental methods have been developed, and commercial instruments for continuous monitoring of these components have been available for a number of years. For the measurement of carbon monoxide, non-dispersive infrared spectroscopy has been the accepted tool, in spite of its marginal sensitivity at low parts-per-million levels. For continuously monitoring total hydrocarbons, the hydrogen flame ionization analyzer has been widely accepted as the preferred method. The inadequacy of this latter method became evident when it was concluded that methane is non-reactive and cannot be considered a contaminant even though present at over 1 ppm in the earth's atmosphere. Hence, the need for measuring methane separately became apparent as a means of measuring the reactive and potentially harmful non-methane hydrocarbons fraction. A gas chromatographic method for the measurement of methane and total hydrocarbons which met these requirements has been developed. In this technique, methane was separated on conventional gas chromatographic columns and detected by a hydrogen flame ionization detector (FID) while the total hydrocarbons were obtained by introducing a second sample directly into the FID without separating the various components. The reactive, or non-methane hydrocarbons, were determined by difference. Carbon monoxide was also measured after converting to methane over a heated catalyst to render it detectable by the FID. The development of this method made it possible to perform these measurements with a sensitivity of as much as 1 ppm full scale and a minimum detectability of 20 ppb. Incorporating this technique, criteria were developed by APCO for a second generation continuous automatic instrument for atmospheric monitoring stations.

  20. On-line gas chromatographic analysis of higher alcohol synthesis products from syngas. (United States)

    Andersson, Robert; Boutonnet, Magali; Järås, Sven


    An on-line gas chromatographic (GC) system has been developed for rapid and accurate product analysis in catalytic conversion of syngas (a mixture of H₂ and CO) to alcohols, so called "higher alcohol synthesis (HAS)". Conversion of syngas to higher alcohols is an interesting second step in the route of converting coal, natural gas and possibly biomass to liquid alcohol fuel and chemicals. The presented GC system and method are developed for analysis of the products formed from syngas using alkali promoted MoS₂ catalysts, however it is not limited to these types of catalysts. During higher alcohol synthesis not only the wanted short alcohols (∼C₂-C₅) are produced, but also a great number of other products in smaller or greater amounts, they are mainly short hydrocarbons (olefins, paraffins, branched, non-branched), aldehydes, esters and ketones as well as CO₂, H₂O. Trace amounts of sulfur-containing compounds can also be found in the product effluent when sulfur-containing catalysts are used and/or sulfur-containing syngas is feed. In the presented GC system, most of them can be separated and analyzed within 60 min without the use of cryogenic cooling. Previously, product analysis in "higher alcohol synthesis" has in most cases been carried out partly on-line and partly off-line, where the light gases (gases at room temp) are analyzed on-line and liquid products (liquid at room temp) are collected in a trap for later analysis off-line. This method suffers from many drawbacks compared to a complete on-line GC system. In this paper an on-line system using an Agilent 7890 gas chromatograph equipped with two flame ionization detectors (FID) and a thermal conductivity detector (TCD), together with an Agilent 6890 with sulfur chemiluminescence dual plasma detector (SCD) is presented. A two-dimensional GC system with Deans switch (heart-cut) and two capillary columns (HP-FFAP and HP-Al₂O₃) was used for analysis of the organic products on the FIDs. Light

  1. Axial and Radial Gas Holdup in Bubble Column Reactor

    International Nuclear Information System (INIS)

    Wagh, Sameer M.; Ansari, Mohashin E Alan; Kene, Pragati T.


    Bubble column reactors are considered the reactor of choice for numerous applications including oxidation, hydrogenation, waste water treatment, and Fischer-Tropsch (FT) synthesis. They are widely used in a variety of industrial applications for carrying out gas-liquid and gas-liquid-solid reactions. In this paper, the computational fluid dynamics (CFD) model is used for predicting the gas holdup and its distribution along radial and axial direction are presented. Gas holdup increases linearly with increase in gas velocity. Gas bubbles tends to concentrate more towards the center of the column and follows a wavy path

  2. Fabrication and chromatographic performance of porous-shell pillar-arry columns

    NARCIS (Netherlands)

    Detobel, Frederik; De Bruyne, Selm; de Bruyne, S.; Vangelooven, Joris; de Malsche, Wim; Aerts, Tim; Terryn, Herman; Gardeniers, Johannes G.E.; Eeltink, Sebastiaan; Desmet, Gert


    We report on a new approach to obtain highly homogeneous silica-monolithic columns, applying a sol−gel fabrication process inside a rectangular pillar-array column (1 mm in width, 29 μm in height and 33.75 mm in length) having a cross-sectional area comparable to that of a 200 μm diameter circular

  3. Separative analyses of a chromatographic column packed with a core-shell adsorbent for lithium isotope separation

    International Nuclear Information System (INIS)

    Sugiyama, T.; Sugura, K.; Enokida, Y.; Yamamoto, I.


    Lithium-6 is used as a blanket material for sufficient tritium production in DT fueled fusion reactors. A core-shell type adsorbent was proposed for lithium isotope separation by chromatography. The mass transfer model in a chromatographic column consisted of 4 steps, such as convection and dispersion in the column, transfer through liquid films, intra-particle diffusion and and adsorption or desorption at the local adsorption sites. A model was developed and concentration profiles and time variation in the column were numerically simulated. It became clear that core-shell type adsorbents with thin porous shell were saturated rapidly relatively to fully porous one and established a sharp edge of adsorption band. This is very important feature because lithium isotope separation requires long-distance development of adsorption band. The values of HETP (Height Equivalent of a Theoretical Plate) for core-shell adsorbent packed column were estimated by statistical moments of the step response curve. The value of HETP decreased with the thickness of the porous shell. A core-shell type adsorbent is, then, useful for lithium isotope separation. (authors)

  4. Comprehensive two-dimensional gas chromatographic separations with a microfabricated thermal modulator. (United States)

    Serrano, Gustavo; Paul, Dibyadeep; Kim, Sung-Jin; Kurabayashi, Katsuo; Zellers, Edward T


    Rapid, comprehensive two-dimensional gas chromatographic (GC × GC) separations by use of a microfabricated midpoint thermal modulator (μTM) are demonstrated, and the effects of various μTM design and operating parameters on performance are characterized. The two-stage μTM chip consists of two interconnected spiral etched-Si microchannels (4.2 and 2.8 cm long) with a cross section of 250 × 140 μm(2), an anodically bonded Pyrex cap, and a cross-linked wall coating of poly(dimethylsiloxane) (PDMS). Integrated heaters provide rapid, sequential heating of each μTM stage, while a proximate, underlying thermoelectric cooler provides continual cooling. The first-dimension column used for GC × GC separations was a 6 m long, 250 μm i.d. capillary with a PDMS stationary phase, and the second-dimension column was a 0.5 m long, 100 μm i.d. capillary with a poly(ethylene glycol) phase. Using sets of five to seven volatile test compounds (boiling point ≤174 °C), the effects of the minimum (T(min)) and maximum (T(max)) modulation temperature, stage heating lag/offset (O(s)), modulation period (P(M)), and volumetric flow rate (F) on the quality of the separations were evaluated with respect to several performance metrics. Best results were obtained with a T(min) = -20 °C, T(max) = 210 °C, O(s) = 600 ms, P(M) = 6 s, and F = 0.9 mL/min. Replicate modulated peak areas and retention times were reproducible to <5%. A structured nine-component GC × GC chromatogram was produced, and a 21 component separation was achieved in <3 min. The potential for creating portable μGC × μGC systems is discussed.

  5. Research on technology of online gas chromatograph for SF6 decomposition products (United States)

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


    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.

  6. Relating pressure tuned coupled column ensembles with the solvation parameter model for tunable selectivity in gas chromatography. (United States)

    Sharif, Khan M; Kulsing, Chadin; Chin, Sung-Tong; Marriott, Philip J


    The differential pressure drop of carrier gas by tuning the junction point pressure of a coupled column gas chromatographic system leads to a unique selectivity of the overall separation, which can be tested using a mixture of compounds with a wide range of polarity. This study demonstrates a pressure tuning (PT) GC system employing a microfluidic Deans switch located at the mid-point of the two capillary columns. This PT system allowed variations of inlet-outlet pressure differences of the two columns in a range of 52-17psi for the upstream column and 31-11psi for the downstream column. Peak shifting (differential migration) of compounds due to PT difference are related to a first order regression equation in a Plackett-Burman factorial study. Increased first (upstream) column pressure drop makes the second column characteristics more significant in the coupled column retention behavior, and conversely increased second (downstream) column pressure drop makes the first column characteristics more apparent; such variation can result in component swapping between polar and non-polar compounds. The coupled column system selectivity was evaluated in terms of linear solvation energy relationship (LSER) parameters, and their relation with different pressure drop effects has been constructed by applying multivariate principle component analysis (PCA). It has been found that the coupled column PT system descriptors provide a result that shows a clear clustering of different pressure settings, somewhat intermediate between those of the two commercial columns. This is equivalent to that obtained from a conventional single-column GC analysis where the interaction energy contributed from the stationary phases can be significantly adjusted by choice of midpoint PT. This result provides a foundation for pressure differentiation for selectivity enhancement. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Fluid dynamics of gas-liquid bubble columns

    NARCIS (Netherlands)

    Delnoij, E.


    Gas-liquid bubble columns are used extensively in the process industries. The gas-liquid twophase flow prevailing in this type of process equipment is extremely complex, inherently unsteady and dominated by phenomena with widely varying time- and length-scales. it is for this reason that many

  8. An inverse gas chromatographic methodology for studying gas-liquid mass transfer. (United States)

    Paloglou, A; Martakidis, K; Gavril, D


    A novel methodology of reversed flow inverse gas chromatography (RF-IGC) is presented. It permits the simultaneous determination of mass transfer coefficients across the gas liquid interface as well as the respective solubility parameters and thermodynamic functions of dissolution of gases into liquids. The standard deviation of the experimentally determined parameters is estimated for first time, which combined with the successful comparison of the values of the present parameters with other literature ones ascertain the reliability of the methodology. Another novelty of the present work is that the chromatographic sampling of the physicochemical phenomena is done without performing the usual flow reversals procedure. Vinyl chloride monomer's (VCM) interaction with various composition liquid foods: orange juice, milk and olive oil was used as model system. The present transfer rates are controlled by the gas film at lower temperatures, but at higher temperatures the resistances in both films tend to become equal. The found liquid diffusivity values express the total mass transfer from the gas phase into the liquid's bulk and they decrease with rising temperature, as the solubilities of gases in liquids do. Solubility, expressed by Henry's law constant and the mean values of interfacial thickness are of the same order of magnitude to literature ones. From the thermodynamic point of view, VCM dissolution in all liquids is accompanied by significant heat release and it is a slightly non-spontaneous process, near equilibrium, while the entropy change values are negative. Copyright © 2016 Elsevier B.V. All rights reserved.

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

    African Journals Online (AJOL)



    May 22, 2012 ... Whole flowers inflorescence was used for the estimation of nutrient elements. Chemicals and apparatus. All the chemicals used were of analytical grade. Refractive index of the oil was determined with Abbe Refractometer. Schimadzu Ge equipped with flame ionization detector (FID) and a glass column.

  10. A low thermal mass fast gas chromatograph and its implementation in fast gas chromatography mass spectrometry with supersonic molecular beams. (United States)

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


    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

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

    Energy Technology Data Exchange (ETDEWEB)

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


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

  12. Investigation of Gas Holdup in a Vibrating Bubble Column (United States)

    Mohagheghian, Shahrouz; Elbing, Brian


    Synthetic fuels are part of the solution to the world's energy crisis and climate change. Liquefaction of coal during the Fischer-Tropsch process in a bubble column reactor (BCR) is a key step in production of synthetic fuel. It is known from the 1960's that vibration improves mass transfer in bubble column. The current study experimentally investigates the effect that vibration frequency and amplitude has on gas holdup and bubble size distribution within a bubble column. Air (disperse phase) was injected into water (continuous phase) through a needle shape injector near the bottom of the column, which was open to atmospheric pressure. The air volumetric flow rate was measured with a variable area flow meter. Vibrations were generated with a custom-made shaker table, which oscillated the entire column with independently specified amplitude and frequency (0-30 Hz). Geometric dependencies can be investigated with four cast acrylic columns with aspect ratios ranging from 4.36 to 24, and injector needle internal diameters between 0.32 and 1.59 mm. The gas holdup within the column was measured with a flow visualization system, and a PIV system was used to measure phase velocities. Preliminary results for the non-vibrating and vibrating cases will be presented.

  13. Investigation of chromatographic behavior and porous properties of butyl methacrylate monolithic columns

    Czech Academy of Sciences Publication Activity Database

    Širc, Jakub; Bosáková, Z.; Coufal, P.; Michálek, Jiří; Guryča, Vilém


    Roč. 23, č. 6 (2008), s. 591-596 ISSN 1042-6914 R&D Projects: GA MŠk 1M0538 Institutional research plan: CEZ:AV0Z40500505 Keywords : capillary HPLC * monolithic columns * morphology Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.706, year: 2008

  14. Simple automated liquid chromatographic system for splitless nano column gradient separations

    Czech Academy of Sciences Publication Activity Database

    Šesták, Jozef; Duša, Filip; Moravcová, Dana; Kahle, Vladislav


    Roč. 1276, FEB (2013), s. 26-32 ISSN 0021-9673 R&D Projects: GA MV VG20112015021; GA MV VG20102015023 Institutional support: RVO:68081715 Keywords : liquid chromatography * automation * splitless gradient * nano columns * alkylphenones Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.258, year: 2013

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

    International Nuclear Information System (INIS)

    Sofronie, E.


    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)

  16. Mass spectrometric protein characterization in proteome analysis using GELoader tip micro-columns packed with various chromatographic material

    International Nuclear Information System (INIS)

    Larsen, M.R.


    In the early 90'ies mass spectrometry (MS) was introduced as a tool for identifying proteins in protein sequence databases. Since then it has become an integrated tool in protein characterization and is today routinely used to identify proteins separated by gel electrophoresis. A two-tiered mass spectrometric protein identification strategy has recently been proposed. In the first strategy peptide mass maps obtained from the protein of interest are compared with theoretically derived peptide mass maps from proteins in protein sequence databases. If the protein cannot be identified by this strategy, tandem mass spectrometric sequencing is used to generate enough sequence data to identify the protein in protein sequence databases or expressed sequence tag (EST) databases. However, the above strategies primarily identify a protein relatively to the DNA sequence, in which no information about e.g. post-translational modifications (PTMs) is stored. PTMs are known to modify the function, location, solubility and activity of proteins in the cell, and they are therefore very important for understanding living cells. More than 200 different PTMs are known, of which glycosylation, phosphorylation and proteolytic processing are the most common ones. Mass spectrometric analysis of PTMs on gel-separated proteins requires a higher amount of protein than for identification only. In addition, higher sequence coverage from the peptide mass maps or pre-purification of the modified peptides prior to MS analysis, is necessary for detection of putative modified peptides. In this study a multi-tiered strategy, in which GELoader tip micro-columns packed with increasingly more hydrophobic chromatographic material are used in combination with mass spectrometry, is described. The ultimate aim was to gain increased sequence coverage from peptide mixtures derived from gel-separated proteins, in order to locate modified peptides. Graphite powder is described as an alternative to traditional

  17. Gas chromatographic retention characteristics of different polysiloxane oligomers

    Energy Technology Data Exchange (ETDEWEB)

    Van Lenten, F. J.; Conaway, J. E.; Rogers, L. B.


    The effects on the Kovats and McReynolds indices for a modified set of Rohrschneider solutes have been examined using two different batches of a commercial polysiloxane stationary phase, Dow-Corning DC-710, and five pure oligomers isolated from the mixture. The significant differences that were found between batches appear to be due primarily to changes in the percentage of one oligomer, the cyclic pentamer. This finding emphasizes the desirability of using a pure stationary phase as well as carefully specifying the column temperature in order to improve intra- and inter- laboratory comparisons of retention indices.

  18. Chlorine and bromine isotope fractionation of halogenated organic pollutants on gas chromatography columns. (United States)

    Tang, Caiming; Tan, Jianhua; Xiong, Songsong; Liu, Jun; Fan, Yujuan; Peng, Xianzhi


    Compound-specific chlorine/bromine isotope analysis (CSIA-Cl/Br) has become a powerful approach to investigate degradation pathways and apportion sources of halogenated organic pollutants (HOPs) in the environment. CSIA-Cl/Br is usually conducted by gas chromatography-mass spectrometry (GC-MS), which could be negatively impacted by isotope fractionation on GC columns. In this study, on-column Cl/Br isotope fractionation of 31 organochlorines and 4 organobromines was explored using GC-double focus magnetic-sector high resolution MS (GC-DFS-HRMS). Twenty-nine HOPs exhibited inverse Cl/Br isotope fractionation for which the heavier isotopologues eluted faster than the lighter ones on GC columns, and two polychlorinated biphenyls (PCB-138 and PCB-153) showed normal isotope fractionation, whereas the rest four HOPs did not show observable isotope fractionation. The isotope fractionation extents varied from -13.0‰ to 73.1‰. Mechanisms of the on-column Cl/Br isotope fractionation were tentatively elucidated with a modified two-film model. The results demonstrate that integrating peak area as complete as possible for separable chromatographic peaks and integrating the middle retention-time segments for the inseparable peaks are helpful to improve precision and accuracy of the CSIA-Cl/Br data. The findings of this study will shed light on development of CSIA-Cl/Br methods with respect to improving precision and accuracy. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    Cheng, Hefa; Reinhard, Martin


    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. Estimation of Chromatographic Columns Performances using Computer Tomography and CFD Simulations

    DEFF Research Database (Denmark)

    Schmidt, Irma; Lottes, Florian; Minceva, Mirjana


    show, that spherical particles seem to be more efficient than irregular ones in terms of HETP, which has to be partly a result of the more homogeneous flow profile they induce. The prediction of column performance in dependence of the structure of the packed bed was simulated by CFD (Computational...... Fluid Dynamics), using a model which besides the hydrodynamics parameters attained by CT also includes adsorption isotherms and mass transfer parameters. The results of the CFD simulation shall help to establish rules for selecting the right adsorption material for a given separation task in advance....

  1. Comparison of column chromatographic and precipitation methods for the purification of a macrocyclic polyether extractant

    International Nuclear Information System (INIS)

    Dietz, M.L.; Felinto, C.; Rhoads, S.; Clapper, M.; Finch, J.W.; Hay, B.P.


    Column chromatography on aminopropyl-derivatized silica and precipitation of a complex with perchloric acid have been evaluated as methods for the purification of di-tert-butylcyclohexano-18-crown-6 (DtBuCH18C6), a compound frequently employed for the selective extraction of strontium from acidic nitrate media. Both methods are shown to provide a simple and effective means of eliminating inactive sample components (i.e., impurities or stereoisomers incapable of extracting strontium) from the crown ether and enriching the material in 4(z),4 prime(z) cis-syn-cis DtBuCH18C6, a stereoisomer capable of highly efficient strontium extraction

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

    African Journals Online (AJOL)

    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, ...

  3. Reversed phase partition chromatographic separation of Gd(III) on poly(Crown Ether) column

    International Nuclear Information System (INIS)

    Mahanwar, K.R.; Sabale, S.R.


    A simple method has been developed for the separation of Gd(III) in hippuric acid medium by using poly(dibenzo-18-crown-6) as stationary phase. The effect of hippuric acid concentration, different eluting agent, foreign ions etc was studied and the optimum conditions were established. Breakthrough capacity of poly(dibenzo-18-crown-6) for Gd(III) was found to be 0.572 ±0.01 mmolg -1 of crown polymer. The separation of Gd(III) from other elements in multicomponent mixtures has been achieved. The method was extended for determination of Gd(III) in real sample. The method is simple, rapid and selective with good reproducibility (approximately ± 2%). Crown ethers are widely used as complexing agent that can selectively capture metal cation in their cavity. This special feature shown by poly (dibenzo-18-crown-6) has been used in our laboratory for selective cation exchanger by column chromatography. No attempts were made for the separation of Gd(III) using hippuric acid media and column chromatography. The present communication describes a simple and sensitive method for the determination of Gd(III) using poly(dibenzo-18-crown-6) as stationary phase in hippuric acid medium. The proposed method affords an attractive feature as compared to the solvent extraction technique i.e. it is free from any organic diluents as an environmental concern

  4. Determination of gas-liquid partition coefficients of several organic solutes in trihexyl(tetradecyl)phosphonium bromide using capillary gas chromatography columns. (United States)

    Ronco, Nicolás R; Menestrina, Fiorella; Romero, Lílian M; Castells, Cecilia B


    In this paper, we report gas-liquid partition constants for thirty-five volatile organic solutes in the room temperature ionic liquid trihexyl(tetradecyl)phosphonium bromide measured by gas-liquid chromatography using capillary columns. The relative contribution of gas-liquid partition and interfacial adsorption to retention was evaluated through the use of columns with different the phase ratio. Four capillary columns with exactly known phase ratios were constructed and employed to measure the solute retention factors at four temperatures between 313.15 and 343.15K. The partition coefficients were calculated from the slopes of the linear regression between solute retention factors and the reciprocal of phase ratio at a given temperature according to the gas-liquid chromatographic theory. Gas-liquid interfacial adsorption was detected for a few solutes and it has been considered for the calculations of partition coefficient. Reliable solute's infinite dilution activity coefficients can be obtained when retention data are determined by a unique partitioning mechanism. The partial molar excess enthalpies at infinite dilution have been estimated from the dependence of experimental values of solute activity coefficients with the column temperature. A thorough discussion of the uncertainties of the experimental measurements and the main advantages of the use of capillary columns to acquire the aforementioned relevant thermodynamic information was performed. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Study on Detection and Identification of Gas Sensor Based on Chromatographic Separation

    Directory of Open Access Journals (Sweden)

    Xiao Wanfu


    Full Text Available This paper developed a chromatographic separation and sensor based on a combination of gas detector, the common precursor gases such as acetone, ether, chloroform and other gas detection. According to the obtained experimental data, proposed one kind based on the principal component analysis and support vector machine algorithm of gas chromatography identification sensor signal processing and recognition; the method used for detection and identification of the air in the precursor gases combine tester self-developed, obtained very good result. This paper designed and developed a chromatographic separation and sensor based on the combination of gas detection instruments, to multi gas detection instrument. On separation characteristics using chromatography, to solve the traditional single common precursor gas detection. The use of a pre processing based on domestication, principal component analysis for feature extraction method of all kinds of gas data. This effectively avoids the sensor substrate voltage fluctuation and gas concentration effects on body recognition, and reduces the gas sample feature vector dimension.

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

    International Nuclear Information System (INIS)

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


    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)

  7. Micro-fabricated semi-packed column for gas chromatography by using functionalized parylene as a stationary phase

    International Nuclear Information System (INIS)

    Nakai, T; Nishiyama, S; Shuzo, M; Delaunay, J-J; Yamada, I


    The conformal coating of effective stationary phases onto micro-fabricated columns having complex geometries such as semi-packed columns poses a real challenge. Here, we report for the first time the conformal coating of a semi-packed column with amino-functionalized parylene diX-AM (poly-aminomethyl-[2,2]-paracyclophane), which was found to be an effective stationary-phase material for the chromatography of short-retention-time compounds. A semi-packed column (consisting of a zigzag array of 30 µm square micro-pillars in a 1.0 m long, 180 µm wide and 230 µm deep channel) and an open tubular column (1.0 m long, 160 µm wide and 230 µm deep channel) used for comparison purposes were micro-fabricated on silicon that was subsequently coated with diX-AM parylene and thermally bonded. The chromatograms recorded on a commercial gas chromatograph demonstrated the usefulness of the conformal diX-AM coating as a stationary phase for semi-packed columns. The separation efficiency of the semi-packed column was found to be more than ten times that of the open tubular column

  8. Research on the separation properties of empty-column gas chromatography (EC-GC) and conditions for simulated distillation (SIMDIS). (United States)

    Boczkaj, Grzegorz; Kamiński, Marian


    Previous studies have revealed it is possible to separate a high-boiling mixture by gas chromatography in empty fused-silica capillary tubing rather than in columns coated with stationary phase. Chromatographic separation occurs solely on the basis of the different boiling points of the substances separated. The high similarity of such separations to those in classic distillation seems advantageous when gas chromatography is used for simulated distillation. This paper presents results from further research on the separation properties of empty fused silica tubing. The efficiency of this chromatographic system has been examined. The usefulness of such conditions has been studied for simulated distillation, i.e. to determine the boiling-point distribution of complex mixtures, mainly petroleum fractions and products, on the basis of their retention relative to reference substances. The results obtained by use of empty-column gas chromatography (EC-GC) and by use of classical simulated distillation columns have been compared for solutes of different polarity. Studies revealed boiling points determined by EC-GC were more accurate than those obtained by the standard method of simulated distillation.

  9. Gas chromatography for in situ analysis of a cometary nucleus V. Study of capillary columns' robustness submitted to long-term reduced environmental pressure conditions. (United States)

    Szopa, C; Sternberg, R; Coscia, D; Goesmann, F; Gomes, R; Legrand, S; Jerome, M; Meierhenrich, U J; Raulin, F


    With the European Space Agency's Rosetta space mission to comet 67P/Churyumov-Gerasimenko, a gas chromatograph, part of the COmetary Sampling And Composition (COSAC) experiment, travelled for about 10 years in the interplanetary medium before operating at the surface of the cometary nucleus in November 2014. During its journey in space, the instrument was exposed to the constraining conditions of the interplanetary medium, including reduced environmental pressures. In order to estimate the potential influence of this severe condition on the chromatographic capillary columns, their stationary phase and the subsequent separation capability, a set of flight spare columns were kept under reduced environmental pressure in the laboratory for the same duration as the probe sent to the comet. The columns' analytical performances were evaluated recently and compared to the original ones obtained just before the launch of the Rosetta probe. The results presented here show that the chromatographic performances of the spare chromatographic columns were not altered in time. From this result, it can be expected that the flight instrument will perform nominally for the analysis of the first cometary nucleus sample to be collected ever, and that the preparation of the interpretation of the data to be taken at the cometary surface nucleus can be done through calibration of these spare columns, and other spare components of the instrument. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Express analysis of explosives, chemical warfare agents and drugs with multicapillary column gas chromatography and ion mobility increment spectrometry. (United States)

    Buryakov, Igor A


    Description of a gas chromatograph designed for express analysis of explosives (2,4-dinitrotoluene, 2,4,6-trinitrotoluene, pentaerythritol tetranitrate), chemical warfare agents (mustard gas, lewisite, sarin) and drugs (heroin, cocaine hydrochloride, crack) is given. The devices comprises a multicapillary chromatographic column and an ion mobility increment spectrometer (MCC-IMIS). The main analytical characteristics of an IMIS (estimated detection limit (DL), linear dynamic range (LDR), speed of response) and a chromatographic column (separation power, degree of separation, a number of possible peaks at a chromatogram section, divided by analysis time) are determined. The maximum value of DL equal to 5 pg/ml was registered for cis-alpha-LW, and the lowest one of 0.001 pg/ml was for cocaine. The maximum value of LDR equal to 1000 was registered for sarin and the lowest one of 150 was for the ions of lewisite. Speed of response of one compound detection with the IMIS was 0.7 s.

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

    International Nuclear Information System (INIS)

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


    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

  12. Gas chromatographic determination of pesticide residues in white mustard. (United States)

    Słowik-Borowiec, Magdalena; Szpyrka, Ewa; Walorczyk, Stanisław


    A new analytical method employing gas chromatography coupled to electron capture and nitrogen phosphorus detection (GC-ECD/NPD) has been developed and validated for the screening and quantification of 51 pesticides in a matrix of high chlorophyll content - white mustard (Sinapis alba L.). For preparation of the sample extract, the citrate buffered QuEChERS procedure was followed. However certain changes were made to adapt the method to our needs and available laboratory resources. The sample size was reduced to 5 g, 10 mL water was added and exchange of solvent before GC analysis was done. The samples spiked with the target pesticides at the concentration level 0.01 mg/kg and a higher level (depending on the compound) yielded average recoveries in the range of 70-120% with relative standard deviations (RSDs) 0-19% except for HCB, S-metolachlor and teflubenzuron, and displayed very good linearity (R(2)>0.99) for nearly all the analytes. Limit of quantification was 0.01 mg/kg for the majority of the analytes. The expanded measurement uncertainties were estimated employing a "top-down" empirical model as being between 6% and 32% and yielding an average value of 18% (coverage factor k=2, confidence level 95%). Copyright © 2014 Elsevier Ltd. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Polužanski Vladimir


    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.

  14. Chemometrics-assisted high performance liquid chromatography-diode array detection strategy to solve varying interfering patterns from different chromatographic columns and sample matrices for beverage analysis. (United States)

    Yin, Xiao-Li; Wu, Hai-Long; Gu, Hui-Wen; Hu, Yong; Wang, Li; Xia, Hui; Xiang, Shou-Xia; Yu, Ru-Qin


    This work reports a chemometrics-assisted high performance liquid chromatography-diode array detection (HPLC-DAD) strategy to solve varying interfering patterns from different chromatographic columns and sample matrices for the rapid simultaneous determination of six synthetic colorants in five kinds of beverages with little sample pretreatment. The investigation was performed using two types of LC columns under the same elution conditions. Although analytes using different columns have different co-elution patterns that appear more seriously in complex backgrounds, all colorants were properly resolved by alternating trilinear decomposition (ATLD) method and accurate chromatographic elution profiles, spectral profiles as well as relative concentrations were obtained. The results were confirmed by those obtained from traditional HPLC-UV method at a particular wavelength and the results of both methods were consistent with each other. All results demonstrated that the proposed chemometrics-assisted HPLC-DAD method is accurate, economical and universal, and can be promisingly applied to solve varying interfering patterns from different chromatographic columns and sample matrices for the analysis of complex food samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Fast gas chromatographic residue analysis in animal feed using split injection and atmospheric pressure chemical ionisation tandem mass spectrometry. (United States)

    Tienstra, M; Portolés, T; Hernández, F; Mol, J G J


    Significant speed improvement for instrumental runtime would make GC–MS much more attractive for determination of pesticides and contaminants and as complementary technique to LC–MS. This was the trigger to develop a fast method (time between injections less than 10 min) for the determination of pesticides and PCBs that are not (or less) amenable to LC–MS. A key factor in achieving shorter analysis time was the use of split injection (1:10) which allowed the use of a much higher initial GC oven temperature. A shorter column (15 m), higher temperature ramp, and higher carrier gas flow rate (6 mL/min) further contributed to analysis-time reduction. Chromatographic resolution was slightly compromised but still well fit-for-purpose. Due to the high sensitivity of the technique used (GC–APCI-triple quadrupole MS/MS), quantification and identification were still possible down to the 10 μg/kg level, which was demonstrated by successful validation of the method for complex feed matrices according to EU guidelines. Other advantages of the method included a better compatibility of acetonitrile extracts (e.g. QuEChERS) with GC, and a reduced transfer of co-extractants into the GC column and mass spectrometer.

  16. Chromatographic fingerprint analysis of secondary metabolites in citrus fruits peels using gas chromatography-mass spectrometry combined with advanced chemometric methods. (United States)

    Parastar, Hadi; Jalali-Heravi, Mehdi; Sereshti, Hassan; Mani-Varnosfaderani, Ahmad


    Multivariate curve resolution (MCR) and multivariate clustering methods along with other chemometric methods are proposed to improve the analysis of gas chromatography-mass spectrometry (GC-MS) fingerprints of secondary metabolites in citrus fruits peels. In this way, chromatographic problems such as baseline/background contribution, low S/N peaks, asymmetric peaks, retention time shifts, and co-elution (overlapped and embedded peaks) occurred during GC-MS analysis of chromatographic fingerprints are solved using the proposed strategy. In this study, first, informative GC-MS fingerprints of citrus secondary metabolites are generated and then, whole data sets are segmented to some chromatographic regions. Each chromatographic segment for eighteen samples is column-wise augmented with m/z values as common mode to preserve bilinear model assumption needed for MCR analysis. Extended multivariate curve resolution alternating least squares (MCR-ALS) is used to obtain pure elution and mass spectral profiles for the components present in each chromatographic segment as well as their relative concentrations. After finding the best MCR-ALS model, the relative concentrations for resolved components are examined using principal component analysis (PCA) and k-nearest neighbor (KNN) clustering methods to explore similarities and dissimilarities among different citrus samples according to their secondary metabolites. In general, four clear-cut clusters are determined and the chemical markers (chemotypes) responsible to this differentiation are characterized by subsequent discriminate analysis using counter-propagation artificial neural network (CPANN) method. It is concluded that the use of proposed strategy is a more reliable and faster way for the analysis of large data sets like chromatographic fingerprints of natural products compared to conventional methods. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Chromatographic selectivity of poly(alkyl methacrylate-co-divinylbenzene) monolithic columns for polar aromatic compounds by pressure-driven capillary liquid chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Shu-Ling; Wang, Chih-Chieh; Fuh, Ming-Ren, E-mail:


    In this study, divinylbenzene (DVB) was used as the cross-linker to prepare alkyl methacrylate (AlMA) monoliths for incorporating π-π interactions between the aromatic analytes and AlMA-DVB monolithic stationary phases in capillary LC analysis. Various AlMA/DVB ratios were investigated to prepare a series of 30% AlMA-DVB monolithic stationary phases in fused-silica capillaries (250-μm i.d.). The physical properties (such as porosity, permeability, and column efficiency) of the synthesized AlMA-DVB monolithic columns were investigated for characterization. Isocratic elution of phenol derivatives was first employed to evaluate the suitability of the prepared AlMA-DVB columns for small molecule separation. The run-to-run (0.16–1.20%, RSD; n = 3) and column-to-column (0.26–2.95%, RSD; n = 3) repeatabilities on retention times were also examined using the selected AlMA-DVB monolithic columns. The π-π interactions between the aromatic ring and the DVB-based stationary phase offered better recognition on polar analytes with aromatic moieties, which resulted in better separation resolution of aromatic analytes on the AlMA-DVB monolithic columns. In order to demonstrate the capability of potential environmental and/or food safety applications, eight phenylurea herbicides with single benzene ring and seven sulfonamide antibiotics with polyaromatic moieties were analyzed using the selected AlMA-DVB monolithic columns. - Highlights: • First investigation on chromatographic selectivity of AlMA-DVB monolithic columns. • Good run-to-run/column-to-column repeatability (<3%) on AlMA-DVB monolithic columns. • Efficient separation of phenylurea herbicides and sulfonamides on AlMA-DVB columns.

  18. Superheated water as eluent in high-temperature high-performance liquid chromatographic separations of steroids on a polymer-coated zirconia column. (United States)

    Fields, S M; Ye, C Q; Zhang, D D; Branch, B R; Zhang, X J; Okafo, N


    High-temperature liquid chromatography (HTLC), with a superheated water mobile phase, has been shown to be a feasible replacement for medium-polarity acetonitrile-water mixtures as an eluent in reversed-phase HPLC. Instrumental parameters of flow-rate, injection volume and mobile phase preheating were shown to have significant effects on the quality of the chromatographic peaks. The selectivity and retention patterns of testosterone and several related compounds were investigated on a porous zirconia, polybutadiene-coated column at temperatures up to 200 degrees C and compared with that of a porous silica, octadecylsilane-coated column and the zirconia column under traditional reversed-phase conditions of an acetonitrile-water mobile phase at 40 degrees C. The selectivity differences observed for testosterone and related compounds show that the separation mechanisms are complementary and unique selectivity is obtained with the zirconia column under HTLC conditions.

  19. Metabolic modeling of synthesis gas fermentation in bubble column reactors. (United States)

    Chen, Jin; Gomez, Jose A; Höffner, Kai; Barton, Paul I; Henson, Michael A


    A promising route to renewable liquid fuels and chemicals is the fermentation of synthesis gas (syngas) streams to synthesize desired products such as ethanol and 2,3-butanediol. While commercial development of syngas fermentation technology is underway, an unmet need is the development of integrated metabolic and transport models for industrially relevant syngas bubble column reactors. We developed and evaluated a spatiotemporal metabolic model for bubble column reactors with the syngas fermenting bacterium Clostridium ljungdahlii as the microbial catalyst. Our modeling approach involved combining a genome-scale reconstruction of C. ljungdahlii metabolism with multiphase transport equations that govern convective and dispersive processes within the spatially varying column. The reactor model was spatially discretized to yield a large set of ordinary differential equations (ODEs) in time with embedded linear programs (LPs) and solved using the MATLAB based code DFBAlab. Simulations were performed to analyze the effects of important process and cellular parameters on key measures of reactor performance including ethanol titer, ethanol-to-acetate ratio, and CO and H2 conversions. Our computational study demonstrated that mathematical modeling provides a complementary tool to experimentation for understanding, predicting, and optimizing syngas fermentation reactors. These model predictions could guide future cellular and process engineering efforts aimed at alleviating bottlenecks to biochemical production in syngas bubble column reactors.

  20. Chromatographic column evaluation for the untargeted profiling of glucosinolates in cauliflower by means of ultra-high performance liquid chromatography coupled to high resolution mass spectrometry. (United States)

    Capriotti, Anna Laura; Cavaliere, Chiara; La Barbera, Giorgia; Montone, Carmela Maria; Piovesana, Susy; Zenezini Chiozzi, Riccardo; Laganà, Aldo


    The untargeted profiling is a promising approach for the characterization of secondary metabolites in biological matrices. Thanks to the recent rapid development of high-resolution mass spectrometry (HRMS) instrumentations, the number of applications by untargeted approaches for biological samples profiling has widely increased in the recent years. Despite the high potentialities of HRMS, however, a major issue in natural products analysis often arises in the upstream process of compounds separation. A separation technique is necessary to avoid phenomena such as signal suppression, and it is especially needed in the presence of isomeric metabolites, which are otherwise indistinguishable. Glucosinolates (GLSs), a group of secondary metabolites widely distributed among plants, resulted to be associated to the prevention of some serious diseases, such as cancer. This led to the development of several methods for the analysis of GLSs in vegetables tissues. The issue of GLSs chromatographic separation has been widely studied in the past because of the difficulty in the analysis of this highly polar and variable class of compounds. Several alternatives to reversed phase (RP) chromatography, sometimes not compatible with the coupling of liquid chromatography with mass spectrometry, have been tested for the analysis of intact GLSs. However, the availability of new stationary phases, in the last years, could allow the re-evaluation of RP chromatography for the analysis of intact GLSs. In this work, a thorough evaluation of four RP chromatographic columns for the analysis of GLSs in cauliflower (Brassica oleracea L. var. botrytis) extracts by an ultra-high performance liquid chromatographic system coupled via electrospray source to a hybrid quadrupole-Orbitrap mass spectrometer is presented. The columns tested were the following: one column Luna Omega polar C 18 , one column Kinetex Biphenyl, one column Kinetex core-shell XB-C 18 , two columns Kinetex core-shell XB-C 18

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

    International Nuclear Information System (INIS)

    Perez, M.; Gonzalez, D.


    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

  2. A Simple and Rapid Extraction for Gas Chromatographic Determination of Thiabendazole and Imazalil Residues in Lemons

    Directory of Open Access Journals (Sweden)

    Navickiene Sandro


    Full Text Available A rapid and efficient method is described for the determination of thiabendazole and imazalil residues in lemons (peel and pulp. The procedure is based on the extraction with an hexane:ethyl acetate mixture (1:1, v/v and gas chromatographic analysis using thermionic specific detection (TSD. The possibility of matrix effect was also studied. Mean recoveries from 8 replicates of fortified samples ranged from 79% to 109%, with relative standard deviation values between 2.4% to 12.8%. The detection and quantification limits of the method were 0.2 mg kg-1 and 0.5 mg kg-1, respectively.

  3. Gas chromatographic-mass spectrometric determination of levodropropizine plasma levels in healthy volunteers. (United States)

    Zaratin, P; De Angelis, L; Cattabeni, F


    A gas chromatographic-mass spectrometric method for the qualitative and quantitative analysis of levodropropizine (S(-)-3-(4-phenyl-piperazin-1-yl)-propane-1,2-diol, DF 526) in plasma is described. The method proved to be highly selective and sensitive. Drug concentrations as low as 5 ng/ml could be measured. Levodropropizine plasma levels were measured in 6 healthy volunteers after administration of an acute 60 mg dose. Peak concentrations were reached between 40 and 60 min and measurable amounts of drug were present till 8 h after administration.

  4. High performance liquid chromatographic separations of gas oil samples and their hydrotreated products using commercial normal phases. (United States)

    Oro, Nicole E; Lucy, Charles A


    Three commercially available high performance liquid chromatography columns are used in normal phase or quasi-normal phase mode for the separation of gas oil samples. The columns are tested with 20 analytical standards to determine their suitability for separations of petroleum samples and their ability to separate the nitrogen group-types (pyrrole and pyridine) found in petroleum. The columns studied are polymeric hypercrosslinked polystyrene (HGN), a biphenyl phase, and a Chromegabond "DNAP" column from ES Industries. The HGN column separates gas oils based on both ring structure and heteroatom, while the biphenyl phase has low retention of most compounds studied in quasi-normal phase mode. The "DNAP" column is selective for nitrogen-containing compounds, separating them from PAHs as well as oxygen and sulphur compounds. Retention data of standards on all three columns is shown, along with chromatograms of gas oil samples on the HGN and "DNAP" columns. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Interfacial areas and gas hold-ups in bubble columns and packed bubble columns at elevated pressures

    NARCIS (Netherlands)

    Oyevaar, M.H.; de la Rie, T.; van der Sluijs, C.L.; Westerterp, K.R.


    Interfacial areas and gas hold-ups have been determined at pressures up to 1.85 MPa in a bubble column with a diameter of 85.5 mm and for superficial gas velocities between 1 and 10 cm s−1. In some experiments the bubble column was packed with glass cylinders of length 5.0 mm and diameter 4.0 mm.

  6. Accurate measurements of infinite dilution activity coefficients using gas chromatography with static-wall-coated open-tubular columns. (United States)

    Xu, Qianqian; Su, Baogen; Luo, Xinyi; Xing, Huabin; Bao, Zongbi; Yang, Qiwei; Yang, Yiwen; Ren, Qilong


    Wall-coated open-tubular (WCOT) columns provide higher column efficiency and lower solute interfacial adsorption effect than packed columns. However, previous efforts used to measure the infinite dilution activity coefficient (γ(∞)) via a chromatographic technique have used packed columns, because the low carrier gas flow rate (U) and the small stationary phase amount (n(2)) in WCOT columns raise large errors. By rationally revising the γ(∞)-calculation equation for static-wall-coated open-tubular column, we observed that U and n(2) are not necessarily needed and the resulting error could be reduced, and WCOT column gas chromatography subsequently became a superior method for the accurate γ(∞) determination. In this study, we validate our revised γ(∞)-calculation equation by measuring γ(∞) in an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate system, in which 55 organic compounds covering a wide range of functional groups were used as probe solutes and their γ(∞) values in the ionic liquid were determined at 40.0, 50.0, and 60.0 °C. Experimental error analysis shows that our revised equation remarkably reduces the error compared to the common γ(∞)-calculation equation. Our data is consistent with previously reported values obtained via other techniques, which further proves the credibility of our revised equation. The accurately determined γ(∞) values can be directly used to calculate the partial molar excess enthalpy, selectivity, and capacity, which will benefit for the rapid screening of solvents (especially ionic liquids) in separation approaches.

  7. Rapid determination of lidocaine solutions with non-column chromatographic diode array UV spectroscopy and multivariate calibration. (United States)

    Wiberg, Kent; Hagman, Anders; Jacobsson, Sven P


    A new method for the rapid determination of pharmaceutical solutions is proposed. A conventional HPLC system with a Diode Array Detector (DAD) was used with no chromatographic column connected. As eluent, purified water (Milli Q) was used. The pump and autosampler of the HPLC system were mainly utilised as an automatic and convenient way of introducing the sample into the DAD. The method was tested on the local anaesthetic compound lidocaine. The UV spectrum (245-290 nm) from the samples analysed in the detector was used for multivariate calibration for the determination of lidocaine solutions. The content was determined with PLS regression. The effect on the predictive ability of three factors: flow, data-collection rate and rise time as well as two ways of exporting a representative UV spectrum from the DAD file collected was investigated by means of an experimental design comprising 11 experiments. For each experiment, 14 solutions containing a known content of lidocaine were analysed (0.02-0.2 mg ml(-1)). From these 14 samples two calibration sets and two test sets were made and as the response in the experimental design the Root Mean Square Error of Prediction (RMSEP) values from the predictions of the two test sets were used. When the factor setting giving the lowest RMSEP was found, this setting was used when analysing a new calibration set of 12 lidocaine samples (0.1-0.2 mg ml(-1)). This calibration model was validated by two external test sets, A and B, analysed on separate occasions for the evaluation of repeatability (test set A) and determination over time (test set B). For comparison, the reference method, liquid chromatography, was also used for analysis of the ten samples in test set B. This comparison of the two methods was done twice on different occasions. The results show that in respect of accuracy, precision and repeatability the new method is comparable to the reference method. The main advantages compared with liquid chromatography are the

  8. Gas chromatograph analysis on closed air and nitrogen oxide storage atmospheres of recalcitrant seeds of Quercus Alba (United States)

    Storage of recalcitrant seeds remains an unsolved problem. This study investigated the quantitative gas analysis of nitrous oxide (N2O) and air atmospheres on the recalcitrant seeds of Quercus alba by using gas chromatograph. Ten seeds were placed in each sealed atmospheric system of air and 98/2% N...

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

    Directory of Open Access Journals (Sweden)

    John H. Loughrin


    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.

  10. Gas Chromatographic Method: Tool for Rapid and Sensitive Analysis of Residual Solvents in Amoxicillin and Ampicillin Tablets

    Directory of Open Access Journals (Sweden)

    Sk Manirul Haque


    Full Text Available A simple and sensitive static head space gas chromatographic (SH-GC method equipped with FID has been developed and validated for simultaneous determination of residual solvents e.g.,  methanol, dichloromethane and toluene in two therapeutic drugs such as amoxicillin  and ampicillin. The separation was achieved with 30 m long Elite - 5 fused silica capillary column and 0.32 mm inner diameter. The developed SH-GC method offered symmetric peak shape, good resolution and reasonable retention time for all the solvents. Beer’s law was obeyed in the concentration ranges 100 – 1200, 50 – 1000 and 50 – 500 ppm for methanol, dichloromethane and toluene, respectively. The method was validated according to international conference on harmonization (ICH guidelines in terms of specificity, linearity, precision, accuracy, limit of detection, limit of quantitation, robustness and solution stability. The degrees of linearity of the calibration curves, the percent recoveries, relative standard deviation for the method were also determined. All the validation parameters were within the acceptable range. The developed SH-GC method could, therefore, be suitable for simple and rapid detection of trace levels residual solvents in other pharmaceutical products and thereby it could be used for routine analysis in any analytical laboratory.

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

    CERN Document Server

    De Asmundis, R


    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...

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

    Directory of Open Access Journals (Sweden)

    Y. Zhang


    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

  13. [Analysis of residues of organochlorine compounds in plant drugs. 3. Identification of residues of polychlorobiphenyl compounds by comparison of gas chromatography on packed and capillary columns and GCMS coupling]. (United States)

    Benecke, R; Brotka, J; Wijsbeek, J; Franke, J P; Bruins, A P; de Zeeuw, R A


    The identification of residues of polychlorinated biphenyls in a test sample of Flores Chamomillae could be achieved by the retention behavior at gas chromatographic analyses on packed and capillary columns compared with reference standard Clophen A 60, respectively as well as well by capillary GC/MS using single ion monitoring of substance-characteristic ion mass.

  14. A multiresidue method by high performance liquid chromatography-based fractionation and gas chromatographic determination of trace levels of pesticides in air and water. (United States)

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


    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.

  15. Preparation and characterization of micro-cell membrane chromatographic column with N-hydroxysuccinimide group-modified silica-based porous layer open tubular capillary. (United States)

    Xu, Liang; Xu, Bei; Zhao, Zhi-Yu; Yang, Hui-Ping; Tang, Cheng; Dong, Lin-Yi; Liu, Kun; Fu, Li; Wang, Xian-Hua


    Cell membrane chromatography (CMC) is an effective tool in screening active compounds from natural products and studying membrane protein interactions. Nevertheless, it always consumes a large amount of cells (e.g. 10 7 -10 8 ) for column preparation. To overcome this, micro-CMC (mCMC), that employs a silica capillary as membrane carrier, was developed. However, both CMC and mCMC suffer from short column life span (e.g. 3days), mainly due to the falling-off of cellular membranes (CMs). This has greatly limited further application of CMC and mCMC, especially when the cells are hard to obtain. To solve this, N-hydroxysuccinimide (NHS)-modified silica-based porous layer open tubular capillary was first prepared for mCMC. The NHS groups can easily react with amino groups on CMs to form a stable covalent bond under a mild condition. So, CMs immobilized on the NHS-modified capillary are less likely to fall off. To verify this, SKBR3/mCMC (Her2 positive) and BALL1/mCMC (CD20 positive) columns were prepared. Two monoclonal antibody drugs, trastuzumab (anti-Her2) and rituximab (anti-CD20), were selected as analytes to characterize the columns. As a result, NHS-modified column for mCMC can afford higher chromatographic retention than non-modified column. Besides, the column life span was significantly improved to more than 16days for SKBR3/mCMC and 14days for BALL1/mCMC, while the compared column showed a sharp decline in retention factor in first 3days. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. A rapid impregnation method for loading desired amounts of extractant on prepacked reversed-phase columns for high performance liquid chromatographic separation of metal ions. (United States)

    Ramzan, Muhammad; Kifle, Dejene; Wibetoe, Grethe


    A time-efficient impregnation method for loading extractant onto reversed-phase columns was developed, using di-(2-ethylhexyl) phosphoric acid (HDEHP) as a model extractant. The optimal loading conditions for the impregnation process of a standard analytical scale column was achieved by dissolving an appropriate amount of HDEHP (per void volume) in n-pentane, flushing the column with two void volumes (5mL) of impregnation solution and heating the column for a short time to remove the solvent. The process takes about one hour, a significant time reduction compared to commonly used impregnation methods (17-23h). The chromatographic traits for separation of the lighter lanthanides (La-Gd) using columns impregnated under different conditions were evaluated; heating for short period of time gave improved column performance most likely due to the presence of n-pentane in the pores of the support material. A linear relation was found (R 2 =0.9934) for the amount of HDEHP loaded as a function of HDEHP concentration in the impregnation solution. The coated amounts of HDEHP were in the range of 0.29-2.25mmol per column by flushing with 5mL of impregnation solution containing 0.3-5.0mmol of HDEHP per void volume. This 'flush-evaporate' impregnation method allowed for loading a pre-determined amount of extractant and produces very small amounts of organic waste. An overview of the various impregnation approaches previously used for extractant coating on prepacked columns and bulk support materials is also presented. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Breakthrough characteristics of gas absorption in a packed column

    International Nuclear Information System (INIS)

    Shitanda, Shoji; Fukada, Satoshi; Koto, Kenji; Mitsuishi, Nobuo


    In nuclear industries, the operations to collect or recover various radioactive and non-radioactive gases with a number of absorption or adsorption reagents are practically utilized or planned. Specifically in the operations of recovering hydrogen isotopes, the direct collecting method with active metals such as uranium, zirconium (Zr) and yttrium is watched with keen interest. In this study, the capability of recovering hydrogen by means of Zr was investigated through the estimation of rate-determining step, by flowing the gas mixture of hydrogen and argon after activating metallic Zr under the condition of high temperature and high vacuum, and by determining overall mass transfer coefficient from the absorption breakthrough curves. The details of a packed column and the flowsheet are also described, and the deterioration of Zr powder is considered. That is, the diffusion speed and absorbing reaction speed of hydrogen in Zr particles are supposed to be slow and dominant in mass transfer speed. Further, since gas mixture does not simply diffuse in Zr particles, but the reaction plane seems to move toward the center from the surface in the case of Zr, different from general adsorbents, the moving speed seems to give large effect on the rate-determining step. It is ensured that the hydrogen absorption with Zr powder is so active that hydrogen in gas flow can easily be recovered, and its separation from other gases can be effectively carried out by the desorption of hydrogen from Zr powder by heating it in vacuum. (Wakatsuki, Y.)

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

    International Nuclear Information System (INIS)

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


    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. Evaluation of liquid chromatographic behavior of lumazinic derivatives, from α-dicarbonyl compounds, in different C18 columns: application to wine samples using a fused-core column and fluorescence detection. (United States)

    Hurtado-Sánchez, María del Carmen; Espinosa-Mansilla, Anunciación; Rodríguez-Cáceres, María Isabel; Durán-Merás, Isabel


    Several C18 columns, packed with totally porous particles of different sizes and shell thicknesses, have been compared for simultaneous determination of α-dicarbonyl compounds, previous derivatization to lumazinic derivatives. Chromatographic conditions for the separation have been optimized for each column, and chromatographic parameters have been calculated and exhaustively compared. A core-shell C18 column provided the best results, and a HPLC method with fluorimetric detection has been proposed. The developed method has been validated in terms of linearity, precision, and sensitivity. Detection and quantification limits obtained were comprised between 0.02 and 0.30 and 0.07 and 1.0 ng mL(-1), respectively, while RSD values obtained were lower than 6% and 5% in intraday and interday repeatability studies, respectively. The method has been applied to analysis of the α-dicarbonyl compounds in different types of wines. The higher levels of the total α-dicarbonyl compounds were found in sweet wines and the lower levels in white wines.

  20. Validated gas chromatographic-negative ion chemical ionization mass spectrometric method for delta(9)-tetrahydrocannabinol in sweat patches. (United States)

    Saito, Takeshi; Wtsadik, Abraham; Scheidweiler, Karl B; Fortner, Neil; Takeichi, Sanae; Huestis, Marilyn A


    A sensitive gas chromatography-negative ion chemical ionization mass spectrometry (GC/MS-NICI) method was developed and validated for the measurement of Delta(9)-tetrahydrocannabinol (THC) in human sweat patches. THC-d(0) and THC-d(3) were added to worn blank sweat patches (PharmChek; PharmChem Incorporated) and extracted with 3 mL of methanol-0.2 mol/L sodium acetate buffer (pH 5.0, 3:1 by volume) on a reciprocating shaker at ambient temperature for 30 min. Extracted solution (2 mL) was diluted with 8 mL of 0.1 mol/L sodium acetate buffer (pH 4.5) and extracted by use of solid-phase extraction columns (CleanScreen; United Chemical Technologies). Dried extracts were derivatized with trifluoroacetic acid and analyzed with an Agilent 6890 gas chromatograph interfaced with an Agilent 5973 mass selective detector operated in NICI-selected ion-monitoring mode. The lower limits of detection and quantification for THC in human sweat were 0.2 and 0.4 ng/patch, respectively. The calibration curve was linear from 0.4 to 10 ng/patch (R(2) >0.995). Overall recovery of THC from blank worn patches to which 0.6, 4.0, and 8.0 ng of THC had been added was 44-46%. Assay imprecision, expressed as CV, was THC quantification. This GC/MS-NICI assay for THC in human sweat provides adequate sensitivity and performance characteristics for analyzing THC in sweat patches and meets the requirements of the proposed Substance Abuse and Mental Health Administration's guidelines for sweat testing.

  1. Chromatographic studies of unusual on-column degradations of aniline compounds on XBridge Shield RP18 column in high pH aqueous mobile phase. (United States)

    Wang, Fang; Liu, Xiao-Keng; Lai, Susanna; Fang, Jan; Semin, David


    This paper reports unusual on-column degradations of aniline compounds on Waters XBridge Shield RP18 column when ammonium hydroxide in water and acetonitrile were used as mobile phases in liquid chromatography. The change of the level of on-column degradation of a model compound (Compound 1) with time was observed in the first fifteen injections when started at 60 °C. During a subsequent cooling program from 60 °C to 10 °C with a 10 °C interval, the levels of the degradation products of Compound 1 changed with the change of temperature and reached a maximum at 40 °C. The on-column degradation of Compound 1 was observed when started at 10 °C in the first injection, however, the magnitude of the change of the level of on-column degradation of Compound 1 with time in the first fifteen injections was much smaller than that at 60 °C. During a subsequent heating program from 10 to 60 °C with a 10 °C interval, the levels of the degradation products of Compound 1 increased with the increase in temperature but without a maximum. The change of the degradation product levels of this model compound in the heating process is not super-imposable with that in the cooling process, which demonstrates the degree of the degradation also depends on the heating or cooling process. Column history studies demonstrated that the on-column degradation of Compound 1 changed dramatically on the used columns at both starting temperatures while the dependency of heating and cooling processes on on-column degradation still existed. The unusual on-column degradation of Compound 1 on the used columns can be regenerated in a very similar fashion with an acetic acid column-wash procedure, but is not identical to that on the new column. Similar degradations of other commercially available aniline compounds were also observed with this high pH aqueous mobile phase system. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Liquid chromatographic extraction medium (United States)

    Horwitz, E. Philip; Dietz, Mark L.


    A method and apparatus for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column is described. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water.

  3. Liquid chromatographic determination of aflatoxin M1 in milk powder using immunoaffinity columns for cleanup : interlaboratory study

    NARCIS (Netherlands)

    Tuinstra, L G; Roos, A H; van Trijp, J M


    A liquid chromatographic method for determining low aflatoxin M1 concentrations in milk was evaluated in an International Dairy Federation (IDF) interlaboratory study. The study involved 16 participants from 11 countries. The method, chosen after a comparison of several methods by a preparatory

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

    International Nuclear Information System (INIS)

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


    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

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

    Directory of Open Access Journals (Sweden)

    Milina R.


    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.

  6. Determination and discrimination of biodiesel fuels by gas chromatographic and chemometric methods (United States)

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


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

    International Nuclear Information System (INIS)

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


    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)

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

    Mills, G A; Walker, V


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

    International Nuclear Information System (INIS)

    Hellmuth, K.H.; Mirzai, H.


    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

  10. Coupling of column liquid chromatography and surface-enhanced resonance Raman spectroscopy via a thin-layer chromatographic plate.

    NARCIS (Netherlands)

    Coulter, S.K.; Gooijer, C.; Velthorst, N.H.; Brinkman, U.A.T.; Somsen, G.W.


    Surface-enhanced resonance Raman (SERR) spectroscopy was used to characterize compounds separated by column liquid chromatography (LC). Three percent of the effluent from a conventional-size LC column were immobilized on a moving thinlayer chromatography (TLC) plate using a spray-jet

  11. New gas chromatographic instrumentation for studying the action of sulfur dioxide on marbles. (United States)

    Bakaoukas, Nikolaos; Kapolos, John; Koliadima, Athanasia; Karaiskakis, George


    Reversed-flow gas chromatography, which is a sub-technique of inverse gas chromatography, is an experimental arrangement simulating a simple model for the action of air pollutants on buildings and monuments, in laboratory scale. By using a commercial gas chromatograph and an appropriate mathematical analysis, kinetic parameters such as rate constants for adsorption k1, adsorption/desorption kR and surface reaction k2, as well as surface diffusion coefficients Dgamma, deposition velocities Vd and reaction probabilities gamma of SO2 on marble surfaces at different temperatures (303.15-353.15 K) in the presence or in the absence of protective materials (an acrylic copolymer, Paraloid B-72 or a siloxane, CTS Silo 111) were calculated. From the above mentioned physicochemical quantities the ability of the examined materials to minimize the dry deposition of SO2 on marble is carrying out and a possible mechanism for the interaction between SO2 and Paraloid B-72 was suggested. Both materials (CTS SILO 111 and Paraloid B-72) are good enough for protecting marble against SO2 at low temperatures (303.15-323.15), while at high temperatures (333.15-353.15), siloxane seems to protect marble better than acrylic copolymer.


    NARCIS (Netherlands)



    A capillary gas chromatographic method with nitrogen-phosphorus detection for the determination of N-acetylisoputreanine-gamma-lactam (acisoga) in urine is described. The method was validated by comparing the results with those given by an isotope dilution mass fragmentographic method. Making use of

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

    DEFF Research Database (Denmark)

    Jensen, Niels; Jørgensen, Sten Bay


    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...

  14. Measurement of the eddy dispersion term in chromatographic columns: III. Application to new prototypes of 4.6 mm I.D. monolithic columns. (United States)

    Gritti, Fabrice; Guiochon, Georges


    We investigated the mass transfer mechanism in four research prototypes of silica monolithic columns of the second generation provided by their manufacturer (Merck KGaA, Darmstadt, Germany). The heights equivalent to a theoretical plate (HETP) of these columns were measured. The different contributions to the total HETP (longitudinal diffusion term B/u(S), skeleton/eluent mass transfer resistance term Cu(S), and eddy diffusion term A) were determined experimentally for a non-retained (uracil) and for a retained (naphthalene) compound. We used the peak parking method to determine the longitudinal diffusion term, a recently developed accurate model of effective diffusion in silica monolithic structures to determine the skeleton/eluent mass transfer resistance term, and an accurate method of measurement of the total column HETP to determine the eddy diffusion term. The results show that the minimum plate heights of these monolithic column prototypes range between 6 and 7 μm for retained analytes, three times lower than those observed for monolithic columns of the first generation. A detailed analysis of the eddy diffusion term demonstrates that the improvement observed in the column efficiency is explained in part by the 40% reduction of the domain size (which provides thinner half-height peak width) but mostly by a two-fold decrease of the radial velocity bias across the silica rods (which provides more symmetrical peaks). Yet, the rods in these columns exhibit a residual radial heterogeneity leading to a minimum HETP of only 10 μm for non-retained compounds. Copyright © 2011 Elsevier B.V. All rights reserved.

  15. Measurement of the eddy diffusion term in chromatographic columns. I. Application to the first generation of 4.6mm I.D. monolithic columns. (United States)

    Gritti, Fabrice; Guiochon, Georges


    The corrected heights equivalent to a theoretical plate (HETP) of three 4.6mm I.D. monolithic Onyx-C(18) columns (Onyx, Phenomenex, Torrance, CA) of different lengths (2.5, 5, and 10 cm) are reported for retained (toluene, naphthalene) and non-retained (uracil, caffeine) small molecules. The moments of the peak profiles were measured according to the accurate numerical integration method. Correction for the extra-column contributions was systematically applied. The peak parking method was used in order to measure the bulk diffusion coefficients of the sample molecules, their longitudinal diffusion terms, and the eddy diffusion term of the three monolithic columns. The experimental results demonstrate that the maximum efficiency was 60,000 plates/m for retained compounds. The column length has a large impact on the plate height of non-retained species. These observations were unambiguously explained by a large trans-column eddy diffusion term in the van Deemter HETP equation. This large trans-rod eddy diffusion term is due to the combination of a large trans-rod velocity bias (≃3%), a small radial dispersion coefficient in silica monolithic columns, and a poorly designed distribution and collection of the sample streamlets at the inlet and outlet of the monolithic rod. Improving the performance of large I.D. monolithic columns will require (1) a detailed knowledge of the actual flow distribution across and along these monolithic rod and (2) the design of appropriate inlet and outlet distributors designed to minimize the nefarious impact of the radial flow heterogeneity on band broadening. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. FORTRAN program for calculating liquid-phase and gas-phase thermal diffusion column coefficients

    International Nuclear Information System (INIS)

    Rutherford, W.M.


    A computer program (COLCO) was developed for calculating thermal diffusion column coefficients from theory. The program, which is written in FORTRAN IV, can be used for both liquid-phase and gas-phase thermal diffusion columns. Column coefficients for the gas phase can be based on gas properties calculated from kinetic theory using tables of omega integrals or on tables of compiled physical properties as functions of temperature. Column coefficients for the liquid phase can be based on compiled physical property tables. Program listings, test data, sample output, and users manual are supplied for appendices

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

    International Nuclear Information System (INIS)

    Kadkhodayan, B.


    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. Electronic Nose using Gas Chromatography Column and Quartz Crystal Microbalance

    Directory of Open Access Journals (Sweden)

    Hari Agus Sujono


    Full Text Available The conventional electronic nose usually consists of an array of dissimilar chemical sensors such as quartz crystal microbalance (QCM combined with pattern recognition algorithm such as Neural network. Because of parallel processing, the system needs a huge number of sensors and circuits which may emerge complexity and inter-channel crosstalk problems. In this research, a new type of odor identification which combines between gas chromatography (GC and electronic nose methods has been developed. The system consists of a GC column and a 10-MHz quartz crystal microbalance sensor producing a unique pattern for an odor in time domain. This method offers advantages of substantially reduced size, interferences and power consumption in comparison to existing odor identification system. Several odors of organic compounds were introduced to evaluate the selectivity of the system. Principle component analysis method was used to visualize the classification of each odor in two-dimensional space. This system could resolve common organic solvents, including molecules of different classes (aromatic from alcohols as well as those within a particular class (methanol from ethanol and also fuels (premium from pertamax. The neural network can be taught to recognize the odors tested in the experiment with identification rate of 85 %. It is therefore the system may take the place of human nose, especially for poisonous odor evaluations.

  19. Controlled ultraviolet (UV) photoinitiated fabrication of monolithic porous layer open tubular (monoPLOT) capillary columns for chromatographic applications. (United States)

    Collins, David A; Nesterenko, Ekaterina P; Brabazon, Dermot; Paull, Brett


    An automated column fabrication technique that is based on a ultraviolet (UV) light-emitting diode (LED) array oven, and provides precisely controlled "in-capillary" ultraviolet (UV) initiated polymerization at 365 nm, is presented for the production of open tubular monolithic porous polymer layer capillary (monoPLOT) columns of varying length, inner diameter (ID), and porous layer thickness. The developed approach allows the preparation of columns of varying length, because of an automated capillary delivery approach, with precisely controlled and uniform layer thickness and monolith morphology, from controlled UV power and exposure time. The relationships between direct exposure times, intensity, and layer thickness were determined, as were the effects of capillary delivery rate (indirect exposure rate), and multiple exposures on the layer thickness and axial distribution. Layer thickness measurements were taken by scanning electron microscopy (SEM), with the longitudinal homogeneity of the stationary phase confirmed using scanning capacitively coupled contactless conductivity detection (sC(4)D). The new automated UV polymerization technique presented in this work allows the fabrication of monoPLOT columns with a very high column-to-column production reproducibility, displaying a longitudinal phase thickness variation within ±0.8% RSD (relative standard deviation).

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

    International Nuclear Information System (INIS)

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


    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

  1. Development and validation of a stability-indicating gas chromatographic method for quality control of residual solvents in blonanserin: a novel atypical antipsychotic agent. (United States)

    Peng, Ming; Liu, Jin; Lu, Dan; Yang, Yong-Jian


    Blonanserin is a novel atypical antipsychotic agent for the treatment of schizophrenia. Ethyl alcohol, isopropyl alcohol and toluene are utilized in the synthesis route of this bulk drug. A new validated gas chromatographic (GC) method for the simultaneous determination of residual solvents in blonanserin is described in this paper. Blonanserin was dissolved in N, N-dimethylformamide to make a sample solution that was directly injected into a DB-624 column. A postrun oven temperature at 240°C for approximately 2 h after the analysis cycle was performed to wash out blonanserin residue in the GC column. Quantitation was performed by external standard analyses and the validation was carried out according to International Conference on Harmonization validation guidelines Q2A and Q2B. The method was shown to be specific (no interference in the blank solution), linear (correlation coefficients ≥0.99998, n = 10), accurate (average recoveries between 94.1 and 101.7%), precise (intra-day and inter-day precision ≤2.6%), sensitive (limit of detection ≤0.2 ng, and limit of quantitation ≤0.7 ng), robust (small variations of carrier gas flow, initial oven temperature, temperature ramping rate, injector and detector temperatures did not significantly affect the system suitability test parameters and peak areas) and stable (reference standard and sample solutions were stable over 48 h). This extensively validated method is ready to be used for the quality control of blonanserin.

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

    Directory of Open Access Journals (Sweden)

    E.O. Odebunmi


    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. Chiral high-performance liquid chromatographic analysis of fluoxetine and norfluoxetine in rabbit plasma, urine, and vitreous humor using an acetylated beta-cyclodextrin column. (United States)

    Yee, L; Wong, S H; Skrinska, V A


    Fluoxetine (Prozac) is a potent selective serotonin reuptake inhibitor used for the treatment of major depression. Both fluoxetine (F) and its demethylated metabolite, norfluoxetine (NF), are racemic. S-Fluoxetine (SF) and S-norfluoxetine (SNF) are more potent inhibitors of serotonin reuptake than R-fluoxetine (RF) and R-norfluoxetine (RNF). Quantitation of individual enantiomers may provide a greater understanding of pharmacokinetic properties. The objective of this study was to perform a limited chiral selectivity study using rabbit plasma, urine, and vitreous humor analyzed by a solid-phase extraction protocol and a newly developed chiral analysis with an acetylated beta-cyclodextrin (CD) column. Liquid chromatographic parameters for CD were as follows: a mobile phase composition of methanol/0.3% triethylamine buffer, pH 5.6, (30:70), a flow rate of 1 mL/min, detection at 214 nm, and a temperature of 40 degrees C. Elution order was SNF, SF, RNF, and RF with capacity factors of 6, 7, 8, and 9, respectively. The corresponding resolution factors were as follows: R1,2 = 0.8, R2,3 = 1.2, and R3,4 = 0.9. The conditions for solid-phase extraction were optimized for Varian Bond Elut Certify columns. Following sample application, the column was rinsed with water, acetic acid, and then with methanol. Drug enantiomers were eluted with methylene chloride, isopropanol, and ammonium hydroxide (78:20:2). After extract evaporation, the extract residue was reconstituted for high-performance liquid chromatographic analysis. To investigate chiral pharmacology, a biodistribution study was performed by administering 2 mg/kg of F to five rabbits. Blood, urine, and vitreous specimens were collected. Plasma samples collected 45 min postinjection showed nearly equal concentrations of RF and SE After 24 h, the only metabolite detected in plasma was RNF. Drugs were not detectable in vitreous humor. Urine concentrations of SNF, SF, RNF, and RF were 51, 76, 34, and 8 microg/L, respectively

  4. Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating. (United States)

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


    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.

  5. Gas Chromatographic Determination of Fatty Acids in Oils with Regard to the Assessment of Fire Hazard (United States)

    Bartošová, Alica; Štefko, Tomáš


    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.

  6. Novel gas holdup and regime transition correlation for two-phase bubble columns (United States)

    Besagni, G.; Inzoli, F.


    The gas holdup is dimensionless parameter of fundamental and practical importance in the operation, design and scale-up of bubble columns. Unfortunately, the many relationships between the bubble column fluid dynamic parameters and the various variables characterizing the system make it difficult to find general correlations for the precise estimation of the gas holdup. Wilkinson et al. (1992), in their pioneering paper, proposed a correlation to predict the gas holdup in industrial-scale bubble columns, based on the physical properties of the phases and the operating conditions. However, this correlation lacks in generality, as it does not take in account the bubble column design. In this paper, we propose a generalization of the Wilkinson et al. (1992) gas holdup correlation to take into also the bubble column design parameters. Starting from considerations concerning the flow regime transition, corrective parameters are included to account for the effects introduced by the gas sparger openings, the bubble column aspect ratio and the bubble column diameter. The proposed correlation has been found to predict fairly well previously published gas holdup and flow regime transition data.

  7. Influence of structured packing on gas holdup in a three-phase bubble column

    DEFF Research Database (Denmark)

    Monsalvo, Matias Alfonso; Böhm, Ursula


    In this work, the influence of structured packing on gas holdup in gas-liquid-solid dispersions has been studied. The experiments were carried out in an empty column and in column containing structured packing operating under identical conditions. Glass beads and silicon carbide particles were used...... as the solid material and the volumetric fraction of solids was varied from 0% to around 10%. The liquid viscosity was strongly modified using water, CMC solution and glycerol. The experimental results obtained with both columns were compared with previous results obtained in two-phase bubble columns...... the results obtained with glycerol, these correlations can predict the gas holdup of three-phase bubble columns with reasonable accuracy. (C) 2007 Elsevier Ltd. All rights reserved....

  8. Insights into Tikhonov regularization: application to trace gas column retrieval and the efficient calculation of total column averaging kernels

    Directory of Open Access Journals (Sweden)

    T. Borsdorff


    Full Text Available Insights are given into Tikhonov regularization and its application to the retrieval of vertical column densities of atmospheric trace gases from remote sensing measurements. The study builds upon the equivalence of the least-squares profile-scaling approach and Tikhonov regularization method of the first kind with an infinite regularization strength. Here, the vertical profile is expressed relative to a reference profile. On the basis of this, we propose a new algorithm as an extension of the least-squares profile scaling which permits the calculation of total column averaging kernels on arbitrary vertical grids using an analytic expression. Moreover, we discuss the effective null space of the retrieval, which comprises those parts of a vertical trace gas distribution which cannot be inferred from the measurements. Numerically the algorithm can be implemented in a robust and efficient manner. In particular for operational data processing with challenging demands on processing time, the proposed inversion method in combination with highly efficient forward models is an asset. For demonstration purposes, we apply the algorithm to CO column retrieval from simulated measurements in the 2.3 μm spectral region and to O3 column retrieval from the UV. These represent ideal measurements of a series of spaceborne spectrometers such as SCIAMACHY, TROPOMI, GOME, and GOME-2. For both spectral ranges, we consider clear-sky and cloudy scenes where clouds are modelled as an elevated Lambertian surface. Here, the smoothing error for the clear-sky and cloudy atmosphere is significant and reaches several percent, depending on the reference profile which is used for scaling. This underlines the importance of the column averaging kernel for a proper interpretation of retrieved column densities. Furthermore, we show that the smoothing due to regularization can be underestimated by calculating the column averaging kernel on a too coarse vertical grid. For both

  9. Gas chromatography for in situ analysis of a cometary nucleus. II. Analysis of permanent gases and light hydrocarbons with a carbon molecular sieve porous layer open tubular column. (United States)

    Szopa, C; Sternberg, R; Coscia, D; Raulin, F; Vidal-Madjar, C


    Considering the severe constraints of space instrumentation, a great improvement for the in situ gas chromatographic (GC) determination of permanent and noble gases in a cometary nucleus is the use of a new carbon molecular sieve porous layer open tubular (PLOT) column called Carbobond. No exhaustive data dealing with this column being available, studies were carried out to entirely characterize its analytical performances, especially when used under the operating conditions of the cometary sampling and composition (COSAC) experiment of the European Space Agency (ESA) Rosetta space mission to be launched in 2003 for a rendezvous with comet 46 P/Wirtanen in 2011. The high efficiency and speed of analysis of this column at both atmospheric and vacuum outlet column pressure is demonstrated, and the kinetic mass transfer contribution of this carbon molecular sieve adsorbent is calculated. Besides, differential adsorption enthalpies of several gases and light hydrocarbons were determined from the variation of retention volume with temperature. The data indicate close adsorption behaviors on the Carbobond porous layer adsorbent and on the carbon molecular sieve Carboxen support used to prepare the packed columns. Moreover, taking into account the in situ operating conditions of the experiment, a study of two columns with different porous layer thicknesses allowed one to optimize the separation of the target components and to select the column parameters compatible with the instrument constraints. Comparison with columns of similar selectivity shows that these capillary columns are the first ones able to perform the same work as the packed and micro-packed columns dedicated to the separation of this range of compounds in GC space exploration.

  10. One-step column chromatographic extraction with gradient elution followed by automatic separation of volatiles, flavonoids and polysaccharides from Citrus grandis. (United States)

    Han, Han-Bing; Li, Hui; Hao, Rui-Lin; Chen, Ya-Fei; Ni, He; Li, Hai-Hang


    Citrus grandis Tomentosa is widely used in traditional Chinese medicine and health foods. Its functional components include volatiles, flavonoids and polysaccharides which cannot be effectively extracted through traditional methods. A column chromatographic extraction with gradient elution was developed for one-step extraction of all bioactive substances from C. grandis. Dried material was loaded into a column with petroleum ether: ethanol (8:2, PE) and sequentially eluted with 2-fold PE, 3-fold ethanol: water (6:4) and 8-fold water. The elutes was separated into an ether fraction containing volatiles and an ethanol-water fraction containing flavonoids and polysaccharides. The later was separated into flavonoids and polysaccharides by 80% ethanol precipitation of polysaccharides. Through this procedure, volatiles, flavonoids and polysaccharides in C. grandis were simultaneously extracted at 98% extraction rates and simply separated at higher than 95% recovery rates. The method provides a simple and high-efficient extraction and separation of wide range bioactive substances. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Study on Gas-liquid Falling Film Flow in Internal Heat Integrated Distillation Column (United States)

    Liu, Chong


    Gas-liquid internally heat integrated distillation column falling film flow with nonlinear characteristics, study on gas liquid falling film flow regulation control law, can reduce emissions of the distillation column, and it can improve the quality of products. According to the distribution of gas-liquid mass balance internally heat integrated distillation column independent region, distribution model of heat transfer coefficient of building internal heat integrated distillation tower is obtained liquid distillation falling film flow in the saturated vapour pressure of liquid water balance, using heat transfer equation and energy equation to balance the relationship between the circulating iterative gas-liquid falling film flow area, flow parameter information, at a given temperature, pressure conditions, gas-liquid flow falling film theory makes the optimal parameters to achieve the best fitting value with the measured values. The results show that the geometric gas-liquid internally heat integrated distillation column falling film flow heat exchange area and import column thermostat, the average temperature has significant. The positive correlation between the heat exchanger tube entrance due to temperature difference between inside and outside, the heat flux is larger, with the increase of internal heat integrated distillation column temperature, the slope decreases its temperature rise, which accurately describes the internal gas-liquid heat integrated distillation tower falling film flow regularity, take appropriate measures to promote the enhancement of heat transfer. It can enhance the overall efficiency of the heat exchanger.

  12. Gas chromatographic determination of electron capture sensitive volatile industrial chemical residues in foods, using AOAC pesticide multiresidue extraction and cleanup procedures. (United States)

    Yurawecz, M P; Puma, B J


    Electron capture (EC) gas chromatographic (GC) parameters have been developed for determining some of the more volatile industrial chemicals that can be determined by the AOAC multiresidue method for organochlorine and organophosphorus pesticides with modified GC operating conditions. Retention times relative to pentachlorobenzene are reported for 143 industrial chemicals, pesticides, and related compounds on OV-101 GC columns at 130 degrees C. Also reported for most of the compounds are recoveries from fortified samples carried through the AOAC extraction and cleanup procedures for fatty and/or nonfatty foods, Florisil elution characteristics, and GC relative retention times on mixed OV-101 + OV-210 columns at 130 degrees C. Our laboratory has used the modified EC/GC parameters with the AOAC multiresidue extraction/cleanup procedures to determine many volatile halogenated industrial chemical contaminants in foods, chiefly in samples of fresh-water fish. Other modifications of the AOAC method are described to improve the tentative identification and quantitative measurement of these volatile residues.

  13. Miniature, Low Power Gas Chromatograph with Sample Pre-Processing Capability and Enhanced G-Force Survivability for Planetary Missions, Phase I (United States)

    National Aeronautics and Space Administration — Thorleaf Research, Inc. proposes to develop a miniaturized, low power gas chromatograph (GC) with sample pre-processing capability and enhanced capability for...

  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

    National Research Council Canada - National Science Library

    Longworth, Terri


    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. Two-dimensional chromatographic analysis using three second-dimension columns for continuous comprehensive analysis of intact proteins. (United States)

    Zhu, Zaifang; Chen, Huang; Ren, Jiangtao; Lu, Juan J; Gu, Congying; Lynch, Kyle B; Wu, Si; Wang, Zhe; Cao, Chengxi; Liu, Shaorong


    We develop a new two-dimensional (2D) high performance liquid chromatography (HPLC) approach for intact protein analysis. Development of 2D HPLC has a bottleneck problem - limited second-dimension (second-D) separation speed. We solve this problem by incorporating multiple second-D columns to allow several second-D separations to be proceeded in parallel. To demonstrate the feasibility of using this approach for comprehensive protein analysis, we select ion-exchange chromatography as the first-dimension and reverse-phase chromatography as the second-D. We incorporate three second-D columns in an innovative way so that three reverse-phase separations can be performed simultaneously. We test this system for separating both standard proteins and E. coli lysates and achieve baseline resolutions for eleven standard proteins and obtain more than 500 peaks for E. coli lysates. This is an indication that the sample complexities are greatly reduced. We see less than 10 bands when each fraction of the second-D effluents are analyzed by sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE), compared to hundreds of SDS-PAGE bands as the original sample is analyzed. This approach could potentially be an excellent and general tool for protein analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

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


    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)

  17. Relating gas chromatographic profiles to sensory measurements describing the end products of the Maillard reaction. (United States)

    Stanimirova, I; Boucon, C; Walczak, B


    Often in analytical practice, a set of samples is described by different types of measurements in the hope that a comprehensive characterisation of samples will provide a more complete picture and will help in determining the similarities among samples. The main focus is then on how to combine the information described by different measurement variables and how to analyse it simultaneously. In other words, the main goal is to find a common representation of samples that emphasises the individual and common properties of the different blocks of variables. Several methods can be adopted for the simultaneous analysis of multiblock data with a common object mode. These are: consensus principal component analysis (CPCA), SUM-PCA, multiple factor analysis (MFA) and structuration des tableaux à trois indices de la statistique (STATIS).In this article we present a comparison of the performances of these methods for data describing the chemistry and sensory profiles of the Maillard reaction products. The aroma compounds formed during the reaction of thermal heating between one or two selected amino acids and one or two reducing sugars have been analysed by head space gas chromatography and the intensity and nature of the odour of the resulting products has been evaluated according to selected descriptors by a panel of sensory experts.The results showed that using the information of the chromatographic and sensory data in conjunction enhanced the interpretability of the data. SUM-PCA and more specifically multiple factor analysis, MFA, allowed for a detailed study of the similarities of mixtures in terms of reaction products and sensory profiles. Copyright © 2010 Elsevier B.V. All rights reserved.

  18. Statistical modelling of measurement errors in gas chromatographic analyses of blood alcohol content. (United States)

    Moroni, Rossana; Blomstedt, Paul; Wilhelm, Lars; Reinikainen, Tapani; Sippola, Erkki; Corander, Jukka


    Headspace gas chromatographic measurements of ethanol content in blood specimens from suspect drunk drivers are routinely carried out in forensic laboratories. In the widely established standard statistical framework, measurement errors in such data are represented by Gaussian distributions for the population of blood specimens at any given level of ethanol content. It is known that the variance of measurement errors increases as a function of the level of ethanol content and the standard statistical approach addresses this issue by replacing the unknown population variances by estimates derived from large sample using a linear regression model. Appropriate statistical analysis of the systematic and random components in the measurement errors is necessary in order to guarantee legally sound security corrections reported to the police authority. Here we address this issue by developing a novel statistical approach that takes into account any potential non-linearity in the relationship between the level of ethanol content and the variability of measurement errors. Our method is based on standard non-parametric kernel techniques for density estimation using a large database of laboratory measurements for blood specimens. Furthermore, we address also the issue of systematic errors in the measurement process by a statistical model that incorporates the sign of the error term in the security correction calculations. Analysis of a set of certified reference materials (CRMs) blood samples demonstrates the importance of explicitly handling the direction of the systematic errors in establishing the statistical uncertainty about the true level of ethanol content. Use of our statistical framework to aid quality control in the laboratory is also discussed. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  19. Sub-to super-ambient temperature programmable microfabricated gas chromatography column (United States)

    Robinson, Alex L.; Anderson, Lawrence F.


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

  20. Fuzzy C-means clustering for chromatographic fingerprints analysis: A gas chromatography-mass spectrometry case study. (United States)

    Parastar, Hadi; Bazrafshan, Alisina


    Fuzzy C-means clustering (FCM) is proposed as a promising method for the clustering of chromatographic fingerprints of complex samples, such as essential oils. As an example, secondary metabolites of 14 citrus leaves samples are extracted and analyzed by gas chromatography-mass spectrometry (GC-MS). The obtained chromatographic fingerprints are divided to desired number of chromatographic regions. Owing to the fact that chromatographic problems, such as elution time shift and peak overlap can significantly affect the clustering results, therefore, each chromatographic region is analyzed using multivariate curve resolution-alternating least squares (MCR-ALS) to address these problems. Then, the resolved elution profiles are used to make a new data matrix based on peak areas of pure components to cluster by FCM. The FCM clustering parameters (i.e., fuzziness coefficient and number of cluster) are optimized by two different methods of partial least squares (PLS) as a conventional method and minimization of FCM objective function as our new idea. The results showed that minimization of FCM objective function is an easier and better way to optimize FCM clustering parameters. Then, the optimized FCM clustering algorithm is used to cluster samples and variables to figure out the similarities and dissimilarities among samples and to find discriminant secondary metabolites in each cluster (chemotype). Finally, the FCM clustering results are compared with those of principal component analysis (PCA), hierarchical cluster analysis (HCA) and Kohonon maps. The results confirmed the outperformance of FCM over the frequently used clustering algorithms. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. New and highly efficient column chromatographic extraction and simple purification of camptothecin from Camptotheca acuminata and Nothapodytes pittosporoides. (United States)

    Zeng, Xue-Hua; Li, Yue-Hong; Wu, Shan-Shan; Hao, Rui-Lin; Li, Hui; Ni, He; Han, Han-Bing; Li, Hai-Hang


    Camptothecin, a widely used natural anti-cancer drug, is difficult to extract and purify effectively from plants. To develop new and highly efficient extraction and purification methods for analysis and production of camptothecin from leaves and fruits of Camptotheca acuminata and Nothapodytes pittosporoides roots. Dried materials were loaded in empty columns with fivefold 60% ethanol for leaves or 70% ethanol for fruits of C. acumnata, and sixfold 70% ethanol for N. pittosporoides roots. The columns were eluted with the same solvents at room temperature. Eluent was collected as extraction solution. Extraction solution from leaves and fruits of C. acuminata was vacuum-evaporated to remove ethanol, precipitated at pH 8.0 to remove alkaline insolubles and fractionated with chloroform at pH 3.0, which yields a crude product with 70% purity. Extraction solution from N. pittosporoides roots was concentrated to 1/10 volume and precipitated at pH 3.0, which yields a crude product with 60% purity. All crude products were purified by crystallisation. All steps were monitored by HPLC. Camptothecin was extracted from the three plant materials at a 98% rate with 15- or 18-fold solvent for content analysis, or at a 97% rate with five- or sixfold solvent for production. All crude products were purified to 98%. The overall recovery rates of camptothecin from plant materials to purified products reached 92% or higher. The new procedures are simple and highly efficient, and have multiple advantages for quantitative analysis and large production of camptothecin from plants. Copyright © 2013 John Wiley & Sons, Ltd.

  2. Characterization of low-temperature cofired ceramic tiles as platforms for gas chromatographic separations. (United States)

    Darko, Ernest; Thurbide, Kevin B; Gerhardt, Geoff C; Michienzi, Joseph


    A gas chromatography (GC) column is fabricated within a low-temperature cofired ceramic (LTCC) tile, and its analytical properties are characterized. By using a dual-spiral design, a 100 μm wide square channel up to 15 m in length is produced within an 11 cm × 5.5 cm LTCC tile. The channel is dynamically coated with an OV-101 stationary phase that is cross-linked with dicumyl peroxide. While the uncoated LTCC tiles were able to separate a mixture of n-alkanes, the peak shapes were broad (base width of ~2 min) and tailing. In contrast to this, the coated LTCC tiles produced sharp (base width of ~8-10 s), symmetrical, well-resolved peaks for the same analytes. By using a 7.5 m long channel, about 15,000 plates were obtained for a dodecane test analyte. Further, the coated LTCC tiles were found to produce plate heights that were about 3-fold smaller than those obtained from a conventional capillary GC column of similar length, dimension, and coating operated under the same conditions. As a result, test analyte separations were slightly improved in the LTCC tiles, and their overall performance fared well. In terms of temperature programming, it was found that a series of n-alkanes separated on the LTCC tile provided a cumulative peak capacity of around 54 peaks when using C₈ to C₁₃ as analyte markers. Results indicate that LTCC tiles provide a viable and useful alternative platform for performing good quality GC separations.

  3. [Analysis of hydrogen isotopes by gas chromatography using a MnCl2 coated γ-Al2O3 capillary packed column]. (United States)

    Chen, Ping; Fu, Xiaolong; Hu, Peng; Xiao, Chengjian; Ren, Xingbi; Xia, Xiulong; Wang, Heyi


    The conventional packed column gas chromatographic analysis of hydrogen isotopes has low column efficiency, broad peak and long retention time. In this work, a γ -Al 2 O 3 with MnCl 2 coated capillary packed column was tested at cryogenic temperature. The systematic column efficiency analysis and the hydrogen isotopes analytical technique research had been carried out. The results showed that, the γ -Al 2 O 3 with MnCl 2 coating could greatly improve the surface degree of order, pore structure and adsorption properties. Also the o -H 2 peak and p -H 2 peak were eluted in a single area. The γ -Al 2 O 3 with MnCl 2 coating was packed into a 0.53 mm inner diameter and 1.0 m long fused silica capillary column. It had a good linear relationship used this column with thermal conductivity detector (TCD) to detect the volume concentrations of hydrogen isotopes from 1 to 10 mL/L, and the relative error was less than 5% for low concentration sample testing. For H 2 , HD and D 2 , the retention times can be shortened to 39, 46 and 60 s, respectively. The limits of detection were reduced to 0.046, 0.067 and 0.072 mL/L, respectively. Compared with conventional packed column, capillary packed column had sharper peak form, higher separation degree of adjacent components, shorter retention time and lower detection limits. The above results indicate that the capillary packed column with TCD detector can be used for fast detection of low concentration of hydrogen isotopes and their online analysis.

  4. Novel preconcentration technique for on-line coupling to high-speed narrow-bore capillary gas chromatography: sample enrichment by equilibrium (ab)sorption. II. Coupling to a portable micro gas chromatograph. (United States)

    Tuan, H P; Janssen, H G; Cramers, C A; Mussche, P; Lips, J; Wilson, N; Handley, A


    The technique of equilibrium (ab)sorption has been proven to be a powerful method for preconcentration of gaseous samples for high-speed narrow-bore capillary gas chromatography (GC) in general and field-portable GC instruments, often referred as micro GCs, in particular. Using a simple experimental set-up equipped with an open-tubular enrichment column it is possible to produce a homogeneously enriched sample plug, allowing reproducible injections of an enriched sample into the micro GC. Using a non-polar trapping column enrichment factors found for n-alkanes in the range of C7 to C10 ranged from 15 to 150 and agree well with calculated values. Using a highly retentive Thermocap column, the enrichment factor observed for heptane was above 500. As the use of this new preconcentration method requires only minimum modification of the micro GC, the chromatographic performance of the instrument was not compromised by direct coupling to the preconcentration device. Examples of on-line enrichment with portable micro GC analysis of VOCs from air are shown. These examples clearly demonstrate the potentials of the new method in field analysis.

  5. Behavior of macroporous vinyl silica and silica monolithic columns in high pressure gas chromatography. (United States)

    Maniquet, Adrien; Bruyer, Nicolas; Raffin, Guy; Baco-Antionali, Franck; Demesmay, Claire; Dugas, Vincent; Randon, Jérôme


    80% vinyltrimethoxysilane-based hybrid silica monoliths (80-VTMS), which have been initially developed for separation in reversed-phase liquid chromatography, have been investigated in high pressure gas chromatography separations (carrier gas pressure up to 60bar) and compared to silica monolithic columns. The behavior of both silica and 80-VTMS monolithic columns was investigated using helium, nitrogen and carbon dioxide as carrier gas. The efficiency of 80-VTMS monolithic columns was shown to vary differently than silica monolithic columns according to the temperature and the carrier gas used. Carrier gas nature was a significant parameter on the retention for both silica and vinyl columns in relation to its adsorption onto the stationary phase in such high pressure conditions. The comparison of retention and selectivity between 80-VTMS monoliths and silica was performed under helium using the logarithm of the retention factor according to the number of carbon atoms combined to Kovats indexes. The very good performances of these columns were demonstrated, allowing the separation of 8 compounds in less than 1min. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Bubble Column with Electrolytes: Gas Holdup and Flow Regimes

    Czech Academy of Sciences Publication Activity Database

    Orvalho, Sandra; Růžička, Marek; Drahoš, Jiří


    Roč. 48, č. 17 (2009), s. 8237-8243 ISSN 0888-5885 R&D Projects: GA ČR GA104/07/1110; GA ČR GP104/09/P255; GA AV ČR(CZ) IAA200720801; GA MŠk LA319 Institutional research plan: CEZ:AV0Z40720504 Keywords : bubble column * hydrodynamics * surfactants Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.758, year: 2009

  7. Evaluation of Gas Retention in Waste Simulants: Tall Column Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Schonewill, Philip P.; Gauglitz, Phillip A.; Shimskey, Rick W.; Denslow, Kayte M.; Powell, Michael R.; Boeringa, Gregory K.; Bontha, Jagannadha R.; Karri, Naveen K.; Fifield, Leonard S.; Tran, Diana N.; Sande, Susan; Heldebrant, David J.; Meacham, Joseph E.; Smet, Dave; Bryan, Wesley E.; Calmus, Ronald B.


    Gas generation in Hanford’s underground waste storage tanks can lead to gas accumulation within the layer of settled solids (sludge) at the tank bottom. The gas, which typically has hydrogen as the major component together with other flammable species, is formed principally by radiation-driven chemical reactions. Accumulation of these gases within the sludge in a waste tank is undesirable and limits the amount of tank volume for waste storage. Further, accumulation of large amounts of gas in the sludge may potentially result in an unacceptable release of the accumulated gas if the sludge-layer density is reduced to less than that of the overlying sludge or that of the supernatant liquid. Rapid release of large amounts of flammable gases could endanger personnel and equipment near the tank. For this reason, a thorough understanding of the circumstances that can lead to a potentially problematic gas accumulation in sludge layers is needed. To respond to this need, the Deep Sludge Gas Release Event Program (DSGREP) was commissioned to examine gas release behavior in sludges.

  8. Evaluation of gas chromatographic methods for the determination of trans fat. (United States)

    Delmonte, Pierluigi; Rader, Jeanne I


    Consumption of trans fat has been associated with increased risk of coronary heart disease. For nutrition labeling purposes, the US Food and Drug Administration (FDA) defines trans fat as the sum of all the fatty acids with at least one nonconjugated double bond in the trans configuration. The FDA regulation states that label declarations of trans fat are not required for products that contain less than 0.5 g of trans fat per serving if no claims are made about fat, fatty acids or cholesterol. While attenuated total reflection Fourier-transformed infrared spectroscopy (ATR-FT-IR) provides reproducible measurements for samples containing more than 5% trans fat, methods based on gas chromatography (GC) are needed to measure lower trans fat levels. Trans fat quantitation by GC has recently been updated by considering more fatty acids, focusing more attention on fatty acids present in low amounts, and by using 100-m high-polarity capillary columns for optimal separation. The consistently high interlaboratory relative standard deviations (RSD, e.g., 21% at 1% trans fatty acids (TFA), 60% at 0.17% TFA), and intralaboratory RSD values (e.g., 10% at 1% TFA, 16% at 0.17% TFA) for trans fat at 1% or less of total fat reported in the collaborative study data for American Oil Chemists Society Official Method Ce 1h-05 suggest the need to carefully define the parameters associated with GC analysis of fatty acids.

  9. Quantification of Biogenic and Anthropogenic Hydrocarbons using a Commercial Gas Chromatograph - Ion Trap Mass Spectrometer at a Ground Site near Fort McKay, AB (United States)

    Tokarek, T. W.; Osthoff, H. D.


    The extraction of fossil fuels from the Alberta oil sands has been the focus of considerable attention due to its association with sizeable emissions of a variety of atmospheric pollutants, the magnitude and impacts of which are currently poorly constrained by observations. In order to more reliably estimate the magnitude and impact of these emissions, an intensive air quality measurement campaign, called "Fort McMurray Oil Sands Strategic Investigation of Local Sources" (FOSSILS), was conducted in the summer of 2013 as part of the Alberta-Canada joint oil sands monitoring program (JOSM) to identify and quantify emissions and their transformations from the Alberta oil sands. The challenge is that the region is surrounded by boreal forest, which provides a substantial background of biogenic hydrocarbons during summer. In this presentation, measurements of volatile organic compounds (VOCs) at the AMS13 ground site near Fort McKay, Alberta, from Aug 17 to Sept 6, 2013 using a commercial Griffin 450 gas chromatograph equipped with ion trap mass spectrometric detection and Tenax preconcentration are described. The combination of retention information and electron impact mass spectral data allowed unambiguous identification and quantification of the major biogenic monoterpenes, e.g., α and β-pinene, limonene, camphene, and 3Δ-carene, and of many anthropogenically derived hydrocarbons. Mixing ratios of biogenic hydrocarbons varied with time of day, temperature, and solar radiation, with maxima typically occurring at night, rationalized by nocturnal mixing heights and low mixing ratios of the nocturnal oxidants ozone (O3) and the nitrate radical (NO3). In contrast, mixing ratios of anthropogenic VOCs, e.g., benzene, toluene, ethyl benzene, and o-, p-, and m-xylene (BTEX), strongly depended on meteorological conditions, i.e., local wind direction. During episodes with high BTEX abundance, many additional high molecular weight hydrocarbons were observed which were not

  10. Second dimension column ensemble pressure tuning in comprehensive two-dimensional gas chromatography. (United States)

    Sharif, Khan M; Kulsing, Chadin; Junior, Ademario I da Silva; Marriott, Philip J


    A pressure tunable (PT) coupled column ensemble has been implemented for the second dimension ( 2 D) separation in comprehensive two dimensional gas chromatography (GC×PTGC). This process requires two columns to be connected by a pressure junction, as a replacement for a single narrow bore, short column in 2 D. Various 2 D 1 and 2 D 2 columns may be selected to provide complementary selectivity (polarity) compared to the 1 D column. The tunable residence time arising from differential pressure drop in each 2 D column results in a tunable fractional contribution of each column in the 2 D separation. A sample mixture comprising different chemical classes, including alkanes and alcohols, is used to identify the feasibility and extent of selectivity tuning possible in GC×PTGC. The column length is also varied due to the imposed challenge of wraparound in the PT coupled column system as pressures are adjusted in the 2 D separation. Different experimental parameters, stationary phase materials and column lengths have been applied to investigate and understand the separation behaviour of the 2 D PT coupled column GC×GC system. Results are discussed considering analyte retention time, peak width, linear velocity and the contribution of each 2 D column. A specific and unexpected example of GC×GC separation was demonstrated where the peak positions of polar and apolar compounds could almost swap their 2 D retention position by application of PT. Kerosene was analysed as an example of complex sample analysis by GC×PTGC system. This process is shown to be a practical approach for altering different stationary phase selectivities in a single 2 D arrangement in GC×GC. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

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


    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

  12. In situ derivatization and hollow fiber membrane microextraction for gas chromatographic determination of haloacetic acids in water. (United States)

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


    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 degrees C for 60 min with 20% Na2SO4. The linear calibration curves were observed for the concentrations ranging from 1 to 300 microg L(-1) with the correlation coefficients (R2) being greater than 0.99. The method detection limits of most analytes were below 1 microg L(-1) except DCAA and MCAA that were 2 and 18 microg 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.

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

    International Nuclear Information System (INIS)

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


    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

  14. Gas-solid trickle flow hydrodynamics in a packed column

    NARCIS (Netherlands)

    Westerterp, K.R.; Kuczynski, M.


    The pressure gradient and the static and the dynamic hold-up have been measured for a system consisting of a Fluid Cracking Catalyst (FCC) of 30–150 × 10−6 m diameter, trickling over a packed bed and with a gas streaming in countercurrent flow. The experiments were carried out at ambient conditions

  15. High performance liquid chromatographic determination of ...

    African Journals Online (AJOL)



    sulphonate (synthesized). Instrumentation. The chromatographic apparatus consisted of a Cecil 1200 series. 1000 high performance liquid chromatograph. The analytical column was ODS hypersil C18,5 µm particle size in 250 mm ...

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

    NARCIS (Netherlands)

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


    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

  17. Gas Chromatographic-Selected Ion Monitoring-Mass Spectrometric Determination of Cigarette Mainstream Smoke Components with Sensory Attributes

    Directory of Open Access Journals (Sweden)

    Coleman WM


    Full Text Available A new method has been developed that detects significant quantitative differences in the amounts of pyrazines, pyridines, furfurals, carboxylic acids, b-damascenone, sclareolide, and megastigmatrienones in the mainstream smoke of a series of five commercial cigarettes. This new quantitative method is based on the gas chromatographic-selected ion monitoring-mass spectrometric (GC-SIM-MS determination of the selected smoke constituents. The accuracy and precision of the approach were well within acceptable parameters with the majority of cases relative standard deviation (RSD values consistently around 5%. Sample preparation was simple requiring only the dissolution of the trapped particulate material in a known volume of methanol followed by injection of this clear dark colored solution into the gas chromatograph. This approach represents an advance in the technology in terms of higher sample throughput and less sample workup. Certain products demonstrated consistent trends in concentration of specific chemical classes. The mainstream smoke from a University of Kentucky reference cigarette, 2R4F, was included for reference purposes. These results are applicable in the overall evaluation of the components responsible for the taste associated with cigarette products.

  18. Validated stability indicating liquid chromatographic determination of ebastine in pharmaceuticals after pre column derivatization: Application to tablets and content uniformity testing

    Directory of Open Access Journals (Sweden)

    Eid Manal


    Full Text Available Abstract An accurate, simple, sensitive and selective reversed phase liquid chromatographic method has been developed for the determination of ebastine in its pharmaceutical preparations. The proposed method depends on the complexation ability of the studied drug with Zn2+ ions. Reversed phase chromatography was conducted using an ODS C18 (150 × 4.6 mm id stainless steel column at ambient temperature with UV-detection at 260 nm. A mobile phase containing 0.025%w/v Zn2+ in a mixture of (acetonitril/methanol; 1/4 and Britton Robinson buffer (65:35, v/v adjusted to pH 4.2, has been used for the determination of ebastine at a flow rate of 1 ml/min. The calibration curve was rectilinear over the concentration range of 0.3 - 6.0 μg/ml with a detection limit (LOD of 0.13 μg/ml, and quantification limit (LOQ of 0.26 μg/ml. The proposed method was successfully applied for the analysis of ebastine in its dosage forms, the obtained results were favorably compared with those obtained by a comparison method. Furthermore, content uniformity testing of the studied pharmaceutical formulations was also conducted. The composition of the complex as well as its stability constant was also investigated. Moreover, the proposed method was found to be a stability indicating one and was utilized to investigate the kinetics of alkaline and ultraviolet induced degradation of the drug. The first-order rate constant and half life of the degradation products were calculated.

  19. 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

    Energy Technology Data Exchange (ETDEWEB)

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


    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)

  20. Hydrodynamics and axial mixing in a packed gas-liquid column

    Directory of Open Access Journals (Sweden)

    Barjaktarović Branislava G.


    Full Text Available The objective of this study was to investigate the pilot-plant gas absorption packed column hydrodynamics, as well as axial mixing in the system air-water. The pressure drop and the gas phase holdup data were determined in dependence on the flow rates of gas and liquid phases. The influence of superficial velocities of liquid and gas phases on the liquid axial dispersion in a gas-liquid packed bed column (ID 15 cm consisting of Raschig rings (15x15x2 mm were investigated. The pressure drop was measured with a U-type manometer, connected to the bottom and the top of the working part of the column. The gas phase holdup data in the air-water two-phase system was calculated as a ratio of the gas phase volume to the total volume of the two-phase system. Axial dispersion in the water phase has been determined by examining of the distribution of residence times of a salt tracer (NaCl in the packed bed. The tracer was injected in the liquid flow above the packed bed; samples of liquid were simultaneously taken from two sites at 1 m distance along the bed. Salt concentrations in the samples were determined by conductivity measurements. The mean residence time and the axial dispersion number were calculated by the moment method. The axial dispersion increases with an increase of liquid flow velocities and decrease of superficial air velocities.

  1. Chromatographic hydrogen isotope separation

    International Nuclear Information System (INIS)

    Aldridge, F.T.


    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

  2. Chromatographic hydrogen isotope separation (United States)

    Aldridge, F.T.

    Intermetallic compounds with the CaCu/sub 5/ type of crystal structure, particularly LaNiCo/sub 4/ and CaNi/sub 5/, 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 cn produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  3. Study of stationary phase stability from a column with chromatographic material for steady state treatment of an effluent and/or waste containing Th-232

    International Nuclear Information System (INIS)

    Felinto, Maria Claudia Franca da Cunha; Martinz, Daniel Ortiz


    This work relates the behavior of a new chromatographic material, AMBERCMPO I, that has been studied to remove actinide elements from the High Level Liquid Waste. It gives emphasis to the behavior of chromatographic materials to the extraction of Th 4+ and its performance after some operation cycle. (author)

  4. Selective gas-chromatographic detection using an ion-selective electrode-II Selective detection of fluorine compounds. (United States)

    Kojima, T; Ichise, M; Seo, Y


    Components in samples are separated on a gas chromatography column using hydrogen as carrier gas. The individual components from the column are passed through a platinum tube heated at 1000 degrees , where they undergo hydrogenolysis, and fluorine compounds are converted into hydrogen fluoride. The hydrogen fluoride is dissolved in a slow stream of an absorption solution, and the fluoride ion concentration in the resulting solution is monitored in a flow-cell with a fluoride ion electrode. The potentiometric output of the cell is converted into a signal, which is proportional to the concentration of fluoride ion, by an antilogarithmic converter, and recorded. The response of the detector to fluorine compounds was about 10,000 times that to an equal quantity of other organic compounds, and 5 x 10(-11) mole of fluorobenzene could be detected.

  5. Phase Equilibrium and Diffusion of Solvents in Polybutadiene: A Capillary-Column Inverse Gas Chromatography Study

    NARCIS (Netherlands)

    Cai, W.D.; Ramesh, N.; Tihminlioglu, F.; Danner, R.P.; Duda, J.L.; de Haan, A.B.


    The capillary-column inverse gas chromatography method was used to measure the diffusion and partition coefficients of ethylbenzene, styrene, and acrylonitrile in polybutadiene (PBD) at infinite dilution of the solvents. Experiments were performed over a temperature range of 50-125 °C. At

  6. The gas holdup in a multiphase reciprocating plate column filled with carboxymethylcellulose solutions

    Directory of Open Access Journals (Sweden)



    Full Text Available Gas holdup was investigated in a gas–liquid and gas–liquid-solid reciprocating plate column (RPC under various operation conditions. Aqueous carboxymethylcellulose (sodium salt, CMC solutions were used as the liquid phase, the solid phase was spheres placed into interplate spaces, and the gas plase was air. The gas holdup in the RPC was influenced by: the vibration intensity, i.e., the power consumption, the superficial gas velocity, the solids content and the rheological properties of the liquid phase. The gas holdup increased with increasing vibration intensity and superficial gas velocity in both the two- and three-phase system. With increasing concentration of the CMC PP 50 solution (Newtonian fluid, the gas holdup decreased, because the coalescence of the bubbles was favored by the higher liquid viscosity. In the case of the CMC PP 200 solutions (non-Newtonian liquids, the gas holdup depends on the combined influence of the rheological properties of the liquid phase, the vibration intensity and the superficial gas velocity. The gas holdup in the three-phase systems was greater than that in the two-phase ones under the same operating conditions. Increasing the solids content has little influence on the gas holdup. The gas holdup was correlated with the power consumption (either the time-averaged or total power consuption and the superficial gas velocity.

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

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

  8. Preparation and characterization of alkyl methacrylate-based monolithic columns for capillary gas chromatography applications. (United States)

    Yusuf, Kareem; Aqel, Ahmad; A L Othman, Zeid; Badjah-Hadj-Ahmed, Ahmed Yacine


    Gas chromatography (GC) is considered the least common application of both polymer and silica-based monolithic columns. This study describes the fabrication of alkyl methacrylate monolithic materials for use as stationary phases in capillary gas chromatography. Following the deactivation of the capillary surface with 3-(trimethoxysilyl)propyl methacrylate (TMSM), the monoliths were formed by the co-polymerization of either hexyl methacrylate (HMA) or lauryl methacrylate (LMA) with different percentage of ethylene glycol dimethacrylate (EDMA) in presence of an initiator (azobisisobutyronitrile, AIBN) and a mixture of porogens include 1-propanol, 1,4-butanediol and water. The monoliths were prepared in 500mm length capillaries possessing inner diameters of 250μm. The efficiencies of the monolithic columns for low molecular weight compounds significantly improved as the percentage of crosslinker was increased, because of the greater proportion of pores less than 50nm. The columns containing lower percentages of crosslinker were able to rapidly separate a series of 8 alkane members in 0.7min, but the separation was less efficient for the light alkanes. Columns prepared with the lauryl methacrylate monomer yielded a different morphology for the monolith-interconnected channels. The channels were more branched, which increased the separation time, and unlike the other columns, allowed for temperature programming. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Controllable preparation of copper phthalocyanine single crystal nano column and its chlorine gas sensing properties

    Directory of Open Access Journals (Sweden)

    Jianhong Zhao


    Full Text Available The unsubstituted copper phthalocyanine (CuPc single crystal nano columns were fabricated for the first time as chlorine (Cl2 gas sensors in this paper. The nano columns of CuPc have been prepared on different substrates via template-free physical vapor deposition (PVD approach. The growth mechanism of CuPc nano column on quartz was explored and the same condition used on other substrates including glass, sapphire (C-plane, M-plane, R-plane, Si and SiO2/Si came to a same conclusion, which confirmed that the aligned growth of CuPc nano column is not substrate-dependent. And then the CuPc nano column with special morphology was integrated as in-situ sensor device which exhibits high sensitivity and selectivity towards Cl2 at room temperature with a minimum detection limit as low as 0.08 ppm. The response of sensor was found to increase linearly (26∼659% with the increase for Cl2 within concentration range (0.08∼4.0ppm. These results clearly demonstrate the great potential of the nano column growth and device integration approach for sensor device.

  10. Gas-Liquid flow characterization in bubble columns with various gas-liquid using electrical resistance tomography (United States)

    Jin, Haibo; Yuhuan, Han; Suohe, Yang


    Electrical resistance tomography (ERT) is an advanced and new detecting technique that can measure and monitor the parameters of two-phase flow on line, such as gas-liquid bubble column. It is fit for the industrial process where the conductible medium serves as the disperse phase to present the key bubble flow characteristics in multi-phase medium. Radial variation of the gas holdup and mean holdups are investigated in a 0.160 m i. d. bubble column using ERT with two axial locations (Plane 1 and Plane 2). In all the experiments, air was used as the gas phase, tap water as liquid phase, and a series of experiments were done by adding KCl, ethanol, oil sodium, and glycerol to change liquid conductivity, liquid surface tension and viscosity. The superficial gas velocity was varied from 0.02 to 0.2 m/s. The effect of conductivity, surface tension, viscosity on the mean holdups and radial gas holdup distribution is discussed. The results showed that the gas holdup decrease with the increase of surface tension and increase with the increase of viscosity. Meanwhile, the settings of initial liquid conductivity slightly influence the gas holdup values, and the experimental data increases with the increase of the initial setting values in the same conditions.

  11. The influence of polymeric membrane gas spargers on hydrodynamics and mass transfer in bubble column bioreactors

    DEFF Research Database (Denmark)

    Tirunehe, Gossay; Norddahl, B.


    Gas sparging performances of a flat sheet and tubular polymeric membranes were investigated in 3.1 m bubble column bioreactor operated in a semi batch mode. Air–water and air–CMC (Carboxymethyl cellulose) solutions of 0.5, 0.75 and 1.0 % w/w were used as interacting gas–liquid mediums. CMC...... solutions were employed in the study to simulate rheological properties of bioreactor broth. Gas holdup, bubble size distribution, interfacial area and gas–liquid mass transfer were studied in the homogeneous bubbly flow hydrodynamic regime with superficial gas velocity (UG) range of 0.0004–0.0025 m...

  12. Bubble Column Bioreactors: Comparison with Stirred Fermenters Based on Local Gas Hold-up Distribution

    Czech Academy of Sciences Publication Activity Database

    Vlaev, S. D.; Fialová, Marie


    Roč. 81, 3-4 (2003), s. 535-542 ISSN 0008-4034. [International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering /6./. Vancouver,B.C., 17.08.2003-20.08.2003] Grant - others:INCO-COPERNICUS(XE) IC15/CT98/0502 Institutional research plan: CEZ:AV0Z4072921 Keywords : local gas hold-up * bubble column and impeller dispersion * viscous pseudoplastic liquids Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.330, year: 2003

  13. [Residues of organochlorine compounds in plant drugs. 1. Gas chromatographic determination of residues of organochlorine insecticides]. (United States)

    Benecke, R; Thieme, H; Brotka, J


    A method for the identification and determination of HCH-and DDT-isomers and their respective metabolites in vegetable drugs is presented. The plant material is extracted with hexane in a Soxhlet apparatus in the presence of silicagel and sodium sulfate. For removing interfering endogenous plant constituents a Celite oleum column cleanup and usually and acetonitrile partitioning to follow are necessary. A mixed stationary phase OV-17/QF-1 has proved effective for the gc separation on packed columns. 3H-ECD is used for detection. For the quantitative determination by using an external standard the peak height measurement is recommended. Recoveries of all insecticides were in the order of 70-105% with coefficients of variation between 6 and 20%. To ensure the results the alkaline treatment and oxidation of extracts are proposed.

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

    International Nuclear Information System (INIS)

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


    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)

  15. 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

    International Nuclear Information System (INIS)

    Lockrem, L.L.


    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

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

    Czech Academy of Sciences Publication Activity Database

    Šimek, Petr; Hušek, Petr; Zahradníčková, Helena


    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

  17. Aging and analytical performances evolution of a gas chromatographic system at Mars


    Bonnet, Jean-Yves; Szopa, Cyril; Millan, Maeva; Coscia, David; Cabane, Michel; Belmahdi, I.; Buch, A.; Dequaire, T.; Coll, Patrice; Teinturier, S.; Mahaffy, P.


    International audience; Health data from the gas chromatography (GC) module onboard the SAM instrument [1] will be presented to assess the analytical performances evolution of a GC device in Martian environment through 3 years.

  18. Gas Chromatographic Determination of Methyl Salicylate in Rubbing Alcohol: An Experiment Employing Standard Addition. (United States)

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


    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)

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

    Energy Technology Data Exchange (ETDEWEB)

    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:


    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.

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

    Araújo, Henrique Peres; Félix, Juliana Silva; Manzoli, José Eduardo; Padula, Marisa; Monteiro, Magali


    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.

  1. Interlaboratory study of a multiresidue gas chromatographic method for determination of organochlorine and pyrethroid pesticides and polychlorobiphenyls in milk, fish, eggs, and beef fat. (United States)

    Bordet, François; Inthavong, Dary; Fremy, Jean-Marc


    An interlaboratory study was conducted to validate a gas chromatographic (GC) method for determination of 21 organochlorine pesticides, 6 pyrethroid pesticides, and 7 polychlorobiphenyl (PCB) congeners in milk, beef fat, fish, and eggs. The method was performed at low contamination levels, which represent relevant contents in food, and is an extension of the European standard (method NF-EN-1528, Parts 1-4). It enlarges the applicable scope of the reference EN method to pyrethroid pesticides and proposes the use of solid-phase extraction (SPE) as a cleanup procedure. Cryogenic extraction was made, and SPE cleanup was performed with 2 successive SPE cartridges: C18 and Florisil. After injection of the purified extract onto a GC column, residues were measured by electron capture detection. Food samples (liquid milk, beef fat, mixed fish, and mixed eggs) were prepared, tested for homogeneity, and sent to 17 laboratories in France. Test portions were spiked with 27 pesticides and 7 PCBs at levels from 26 to 45, 4 to 27, 31 to 67, and 19 to 127 ng/g into milk, eggs, fish, and fat, respectively. Based on results for spiked samples, the relative standard deviation for repeatability ranged from 1.5 to 6.8% in milk, 3 to 39% in eggs, 4.5 to 12.2% in fish, and 7 to 13% in fat. The relative standard deviation for reproducibility ranged from 33 to 50% in milk, 29 to 59% in eggs, 31 to 57% in fish, and 30 to 62% in fat. This method showed acceptable intra- and interlaboratory precision data, as corroborated by HORRAT values at low levels of pesticide and PCB contamination. The statistical evaluation of the results was performed according to the International Organization for Standardization (ISO; ISO 3534 standard) and 5725-2 Guideline.

  2. Conservation of bubble size distribution during gas reactive absorption in bubble column reactors

    Directory of Open Access Journals (Sweden)

    P. L.C. LAGE


    Full Text Available Conservation of the bubble size distribution function was applied to the reactive absorption of carbon dioxide in a bubble column reactor. The model developed was solved by the method of characteristics and by a Monte Carlo method. Simulations were carried out using simplified models for the liquid phase and for the gas-liquid mass transfer. Predictions of gas holdup and outlet gas composition showed that the concept of a mean bubble diameter is not applicable when the bubble size distribution is reasonably polydispersed. In these cases, the mass mean velocity and the numerical mean velocity of the bubbles are very different. Therefore, quantification of the polydispersion of bubbles was shown to be essential to gas-phase hydrodynamics modeling.

  3. Gas chromatographic analysis of dimethyltryptamine and beta-carboline alkaloids in ayahuasca, an Amazonian psychoactive plant beverage. (United States)

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


    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.

  4. Rapid gas chromatographic method for the determination of famoxadone, trifloxystrobin and fenhexamid residues in tomato, grape and wine samples. (United States)

    Likas, D T; Tsiropoulos, N G; Miliadis, G E


    Trifloxystrobin, fenhexamid and famoxadone belong to the generation of fungicides acting against a broad spectrum of fungi and widely used in Integrated Pest Management strategies in different agricultural crops but mainly in viticulture. In the present work, a gas chromatographic (GC) method for their determination was developed and validated on tomato, grape and wine matrices. The method was based on a simple one step liquid-liquid microextraction with cyclohexane/dichloromethane (9+1, v/v) and determination of fungicides by gas chromatography with nitrogen phosphorous (NP-) and electron capture (EC-) detection, and ion trap mass spectrometry (ITMS) for confirmation. The method was validated by recovery experiments, assessment of matrix effect and calculation of the associated uncertainty. Recoveries for GC-NPD and GC-ECD were found in the range of 81-102% with RSD NPD, respectively, depending on the sensitivity of each compound with trifloxystrobin being the most sensitive. The expanded uncertainty, calculated for a sample concentration of 0.10 mg/kg, ranged from 4.8 to 13% for the GC-ECD and from 5.4 to 29% for the GC-NPD. The concentration levels for famoxadone residues found in tomato and grape samples from field experiments were clearly below the EU established MRL values, thus causing no problems in terms of food safety.

  5. Multivariate data analysis to characterize gas chromatography columns for dioxin analysis. (United States)

    Do, Lan; Geladi, Paul; Haglund, Peter


    dipolar moment. Finally, the PCA and PLS analyses were complemented with linear regression analysis to identify the most orthogonal column combinations, which could be used in comprehensive two-dimensional gas chromatography (GC×GC) to enhance PCDD/F separation and congener profiling. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Gas chromatographic-mass spectroscopic determination of benzene in indoor air during the use of biomass fuels in cooking time. (United States)

    Sinha, Sukesh Narayan; Kulkarni, P K; Desai, N M; Shah, S H; Patel, G M; Mansuri, M M; Parikh, D J; Saiyed, H N


    A gas chromatography-mass spectroscopic method in electron ionization (EI) mode with MS/MS ion preparation using helium at flow rate 1 ml min(-1) as carrier gas on DB-5 capillary column (30 m x 0.25 mm i.d. film thickness 0.25 microm) has been developed for the determination of benzene in indoor air. The detection limit for benzene was 0.002 microg ml(-1) with S/N: 4 (S: 66, N: 14). The benzene concentration for cooks during cooking time in indoor kitchen using dung fuel was 114.1 microg m(-3) while it was 6.6 microg m(-3) for open type kitchen. The benzene concentration was significantly higher (p analytical chemist dealing with GC-MS in confirmation and quantification of benzene in environmental samples with health risk exposure assessment.

  7. Detection of radiation-induced hydrocarbons in Camembert irradiated before and after the maturing process-comparison of florisil column chromatography and on-line coupled liquid chromatography-gas chromatography

    International Nuclear Information System (INIS)

    Schulzki, G.; Spiegelberg, A.; Bögl, K.W.; Schreiber, G.A.


    The influence of the maturing process on the detection of radiation-induced volatile hydrocarbons in the fat of Camembert has been investigated. Two analytical methods for separation of the hydrocarbon fraction from the lipid were applied: Florisil column chromatography with subsequent gas chromatographic-mass spectrometric (GC-MS) determination as well as on-line coupled liquid chromatography-GC-MS. The maturing process had no influence on the detection of radiation-induced volatiles. Comparable results were achieved with both analytical methods. However, preference is given to the more effective on-line coupled LC-GC method

  8. Gas Chromatographic Verification of a Mathematical Model: Product Distribution Following Methanolysis Reactions. (United States)

    Lam, R. B.; And Others


    Investigated application of binomial statistics to equilibrium distribution of ester systems by employing gas chromatography to verify the mathematical model used. Discusses model development and experimental techniques, indicating the model enables a straightforward extension to symmetrical polyfunctional esters and presents a mathematical basis…

  9. A water column study of methane around gas flares located at the West Spitsbergen continental margin

    DEFF Research Database (Denmark)

    Gentz, Torben; Damm, Ellen; von Deimling, Jens Schneider


    and ebullition of methane into the water column at more than 250 sites in an area of 665 km2. We conducted a detailed study of a subregion of this area, which covers an active gas ebullition area of 175 km2 characterized by 10 gas flares reaching from the seafloor at ∼245 m up to 50 m water depth to identify...... ebullition flare area revealed that the methane concentration gradient is strongly controlled by the pycnocline. While high methane concentrations of up to 524 nmol L1 were measured below the pycnocline, low methane concentrations of less than 20 nmol L1 were observed in the water column above. Variations...... in the δ13CCH4 values point to a 13C depleted methane source (∼ –60‰ VPDB) being mainly mixed with a background values of the ambient water (∼–37.5‰ VPDB). A gas bubble dissolution model indicates that ∼80% of the methane released from gas bubbles into the ambient water takes place below the pycnocline...

  10. A pyrolysis/gas chromatographic method for the determination of hydrogen in solid samples (United States)

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


    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.

  11. A reliable gas capillary chromatographic determination of lactulose in dairy samples


    Montilla, Antonia; Moreno, F. Javier; Olano, Agustín


    A gas capillary chromatography of silylated carbohydrates on SPB-17 phase (50% diphenyl/50% dimethylsiloxane) method for the determination of lactulose has been developed. The method has been evaluated for precision and accuracy using phenyl-β-D-glucoside as internal standard with satisfactory results and, then, applied to 27 commercial milk samples (pasteurized, UHT, sterilized, powder, condensed and chocolate-based milks). Results showed that it was suitable for the determination of lactulo...

  12. Gas holdup in a bubble column in the presence of coaxially placed string of spheres promoter as internal (United States)

    Rohinikumar, P.; Reddy, M. G. Muni; Venkateswarlu, P.; Ramesh, K. V.


    Gas holdup was obtained in a gas-liquid upflow bubble column using quick-closing valve technique. Coaxially placed string of spheres is the promoter internal. An electrolyte solution of ferri-ferro redox couple was the liquid phase and nitrogen was the gas phase. Using promoter the gas holdup obtained was about 22 percent more. The influence of liquid velocity and rod diameter on gas holdup was found to be negligible. The gas holdup increased with gas velocity, pitch and sphere diameter. A correlation equation is obtained for the prediction of gas holdup as a function of Reynolds number and Froude number.

  13. Application of partially diabatic divided wall column to floating liquefied natural gas plant

    International Nuclear Information System (INIS)

    Kim, Young Han


    The offshore operation of chemical plant requires the compactness of process equipments due to its harsh environment. A DWC (divided wall column), a compact ternary separator, is a good candidate for distillation process in the offshore operation. In this study the DWC is applied to the offshore FLNG (floating liquefied natural gas) plant, but high utility cost is required in the application because of the large difference of boiling points among feed components. A partially diabatic DWC is proposed for the reduction of the operating cost here, and its design procedure is presented along with performance and economic evaluations and the examination of thermodynamic efficiency as well. The heating duty of the proposed DWC including tray heat transfer is 35% less than that of the conventional system, and the cooling duty is 18% less. The evaluation indicates that some 16% less utility cost is used in the DWC compared with the conventional system, though 7% more investment is required. The exergy loss is reduced by 12%, and the thermodynamic efficiency is improved by 3.3 percentage point over the conventional system. - Highlights: • Diabatic divided wall column for FLNG (floating liquefied natural gas) plant. • Compact column for offshore operation. • 35% less heating duty required. • 16% lower utility necessary. • Exergy loss reduced by 12%

  14. Performance of a Novel Gas Separation Research Column at Sanford Laboratory (United States)

    Alanson Chiller, Angela; Chiller, Christopher; Mei, Dongming


    A world-wide rise in demand for ultrapure materials has necessitated innovation in the production of low impurity and isotopically separated materials that either has not been utilized in these new applications or relies on aging or energy intensive methods. These materials are sought after for large physics investigations, nuclear non-proliferation detection industries, medical imaging and new frontiers in electronic applications. Techniques in separating and purifying nuclear magnetic resonance isotopes of carbon, oxygen, xenon, krypton, and nitrogen are being developed at Sanford Laboratory, Lead, SD. A two-meter laboratory scale selective phase change column designed specifically for real-time sampling of the gas space at specific temperature and pressure is operated at gas/liquid and gas/solid equilibrium temperatures and pressures for selected gases. We report initial results and future applications. Research Funded by SD Governors 2010 Center.

  15. Gas chromatographic-mass spectrometric analysis of creosotes extracted from wooden sleepers installed in playgrounds

    Energy Technology Data Exchange (ETDEWEB)

    Rotard, W.; Mailahn, W.


    In order to evaluate their hygienic risk, wood samples from sleepers (railroad cross ties) impregnated with coal tar creosote were taken from playgrounds and investigated for hazardous compounds. The samples were extracted with ether, and acid-base-neutral separations were made on the creosote extracts. Water-soluble compounds were also isolated. All the fractions were investigated by capillary gas chromatography-mass spectrometry. Besides phenols in the acidic fractions and N-heterocyclic polynuclear aromatic hydrocarbons (PAH) in the basic fractions, high amounts of neutral PAH and also, in several samples high levels of carcinogenic and cocarcinogenic PAH were determined.

  16. Validation of a gas chromatographic method to quantify sesquiterpenes in copaiba oils. (United States)

    Sousa, João Paulo B; Brancalion, Ana P S; Souza, Ariana B; Turatti, Izabel C C; Ambrósio, Sérgio R; Furtado, Niege A J C; Lopes, Norberto P; Bastos, Jairo K


    Copaifera species (Leguminoseae) are popularly known as "copaiba" or "copaíva". The oleoresins obtained from the trunk of these species have been extensively used in folk medicine and are commercialized in Brazil as crude oil and in several pharmaceutical and cosmetic products. This work reports a complete validated method for the quantification of β-caryophyllene, α-copaene, and α-humulene in distinct copaiba oleoresins available commercially. Thus, essential oil samples (100μL) were dissolved in 20mL of hexanes containing internal standard (1,2,4,5-tetramethylbenzene, 3.0mM) in a 25mL glass flask. A 1μL aliquot was injected into the GC-FID system. A fused-silica capillary column HP-5, coated with 5% phenyl-methylsiloxane was used for this study. The developed method gave a good detection response with linearity in the range of 0.10-18.74mM. Limits of detection and quantitation variety ranged between 0.003 and 0.091mM. β-Caryophyllene, α-copaene, and α-humulene were recovered in a range from 74.71% to 88.31%, displaying RSD lower than 10% and relative errors between -11.69% and -25.30%. Therefore, this method could be considered as an analytical tool for the quality control of different Copaifera oil samples and its products in both cosmetic and pharmaceutical companies. Copyright © 2010 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

    Dennis, K.J.; Shibamoto, T.


    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

  18. Gas chromatographic determination of N-nitrosamines in beverages following automatic solid-phase extraction. (United States)

    Jurado-Sánchez, Beatriz; Ballesteros, Evaristo; Gallego, Mercedes


    A semiautomatic method for the determination of seven N-nitrosamines in beverages by gas chromatography with nitrogen-phosphorus detection is proposed. Beverage samples are aspirated into a solid-phase extraction module for preconcentration and cleanup. The influence of the experimental conditions was examined by using various sorbents among which LiChrolut EN was found to provide quantitative elution and the highest preconcentration factors of all. The proposed method is sensitive, with limits of detection between 7 and 33 ng/kg, and precise, with relative standard deviations from 4.3% to 6.0%. The recoveries of N-nitrosamines from beverage samples spiked with 0.5 or 1 microg/kg concentrations of these compounds ranged from 95% to 102%. The method was successfully applied to the determination of residues of the studied N-nitrosamines in beverages including beer, wine, liquor, whisky, cognac, rum, vodka, grape juice, cider, tonic water, and soft drinks. The analytes were only detected in beer samples, positives being confirmed by gas chromatography coupled with impact ionization mass spectrometry.

  19. Performance characteristics of methods of analysis used for regulatory purposes. I. Drug dosage forms. B. Gas chromatographic methods. (United States)

    Horwitz, W; Albert, R


    Gas chromatographic methods for the analysis of drug dosage forms consist of a simple extraction, dilution with an internal standard solution, and injection, or, even simpler, dilution with the internal standard solution and injection. These methods were used in 7 collaborative studies of the determination of 12 pharmaceuticals, published in the Journal of the AOAC during 1973-1983. A total of 43 individual materials consisting of various dosage forms were each analyzed, usually in duplicate, by an average of 8 laboratories, with a total of 582 reported determinations. The average within-laboratory coefficient of variation (CVo) was 1.25% and the average among-laboratories coefficient of variation (CVx) was 2.41%, for a CVo/CVx ratio of 0.52, at an average outlier rate of 1.4% of the reported values. The line of best fit for CVx plotted against concentration increases with decreasing concentration, extending from a CVx of approximately 1.8% at 100% concentration to a CVx of approximately 3.2% at 1% concentration. The change in CVx for a 10-fold decrease in concentration is approximately 0.7% CVx, independent of analyte and matrix.

  20. Gas chromatographic-thermal energy analysis method for N-nitrosodibutylamine in latex infant pacifiers: collaborative study

    Energy Technology Data Exchange (ETDEWEB)

    Each of 5 collaborating laboratories determined volatile N-nitrosamines in 3 blind quadruplicate sets of latex rubber infant pacifier samples, using a gas chromatographic-thermal energy analysis (GC-TEA) method. Volatile N-nitrosamines are extracted from cut-up pacifier nipples with CH/sub 2/Cl/sub 2/. The extract is concentrated and subjected to high temperature purge and trap, and the nitrosamines are eluted from the trap and determined by GC-TEA. N-Nitrosodibutylamine (NDBA) was the only nitrosamine found in sufficient concentration to allow analysis. NDBA concentrations of the 3 sets of samples were 82.6, 21.0, and 7.12 ng/g rubber. The repeatability relative standard deviations ranged from 7.46 to 24.0% and the reproducibility relative standard deviations from 7.46 to 29.2%. The minimum detectable level of NDBA by this method is 3.6 ng/g rubber. The method has been adopted official first action.

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

    International Nuclear Information System (INIS)

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


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

    Energy Technology Data Exchange (ETDEWEB)

    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)


    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).

  3. Integration and Ruggedization of a Commercially Available Gas Chromatograph and Mass Spectrometer (GCMS) for the Resource Prospector Mission (RPM) (United States)

    Loftin, Kathleen; Griffin, Timothy; Captain, Janine


    The Resource Prospector is a mission to prospect for lunar volatiles (primarily water) at one of the two lunar poles, as well as demonstrate In-Situ Resource Utilization (ISRU) on the Moon. The Resource Prospector consists of a lander, a rover, and a rover-borne scientific payload. The Regolith and Environment Science and Oxygen & Lunar Volatile Extraction (RESOLVE) payload, will be able to (1) locate near subsurface volatiles, (2) excavate and analyze samples of the volatile-bearing regolith, and (3) demonstrate the form, extractability and usefulness of the materials. The gas chromatograph mass spectrometer (GCMS) is the primary instrument in the RESOLVE instrumentation suite responsible for identification and quantification of the volatiles evolved from the lunar regolith. Specifically, this instrument must have: a low mass, a low power consumption, be able to perform fast analyses of samples ranging from less than one to greater than ninety nine percent water by mass, be autonomously controlled by the payload's software and avionics platform, and be able to operate in the harsh lunar environment. The RPM's short mission duration is the primary driver of the requirement for a very fast analysis time currently base lined at less than 2 minutes per sample. This presentation will discuss the requirements levied upon the GCMS design, lessons learned from a preliminary field demonstration deployment, the current design, and the path forward.

  4. Modeling gas formation and mineral precipitation in a granular iron column. (United States)

    Jeen, Sung-Wook; Amos, Richard T; Blowes, David W


    In granular iron permeable reactive barriers (PRBs), hydrogen gas formation, entrapment and release of gas bubbles, and secondary mineral precipitation have been known to affect the permeability and reactivity. The multicomponent reactive transport model MIN3P was enhanced to couple gas formation and release, secondary mineral precipitation, and the effects of these processes on hydraulic properties and iron reactivity. The enhanced model was applied to a granular iron column, which was studied for the treatment of trichloroethene (TCE) in the presence of dissolved CaCO(3). The simulation reasonably reproduced trends in gas formation, secondary mineral precipitation, permeability changes, and reactivity changes observed over time. The simulation showed that the accumulation of secondary minerals reduced the reactivity of the granular iron over time, which in turn decreased the rate of mineral accumulation, and also resulted in a gradual decrease in gas formation over time. This study provides a quantitative assessment of the evolving nature of geochemistry and permeability, resulting from coupled processes of gas formation and mineral precipitation, which leads to a better understanding of the processes controlling the granular iron reactivity, and represents an improved method for incorporating these factors into the design of granular iron PRBs.

  5. Gas chromatographic study of degradation phenomena concerning building and cultural heritage materials. (United States)

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


    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.

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

    International Nuclear Information System (INIS)

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


    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.

  7. Gas chromatographic study of the volatile products from co-pyrolysis of coal and polyethylene wastes. (United States)

    Domínguez, A; Blanco, C G; Barriocanal, C; Alvarez, R; Díez, M A


    The aim of this study was to determine the volatile products distribution of co-processing of coal with two plastic wastes, low-density polyethylene from agriculture greenhouses and high-density polyethylene from domestic uses, in order to explain the observed decrease in coal fluidity caused by polyethylene waste addition. Polymeric materials, although they are not volatile themselves, may be analysed by gas chromatography through the use of pyrolysis experiments. In this way, a series of pyrolysis tests were performed at 400 and 500 degrees C in a Gray-King oven with each of the two plastic wastes, one high-volatile bituminous coal and blends made up of coal and plastic waste (9:1, w/w, ratio). The pyrolysis temperatures, 400 and 500 degrees C, were selected on the basis of the beginning and the end of the coal plastic stage. The organic products evolved from the oven were collected, dissolved in pyridine and analysed by capillary gas chromatography using a flame ionization detector. The analysis of the primary tars indicated that the amount of n-alkanes is always higher than that of n-alkenes and the formation of the alkenes is favoured by increasing the pyrolysis temperature. However, this effect may be influenced by the size of the hydrocarbon. Thus, the fraction C17-C31 showed a higher increase of n-alkenes/n-alkanes ratio than other fractions. On the other hand, the difference between the experimental and estimated values from tars produced from single components was positive for n-alkanes and n-alkenes, indicating that co-pyrolysis of the two materials enhanced the chemical reactivity during pyrolysis and produced a higher conversion than that from individual components.

  8. Potential for Measurement of Trace Volatile Organic Compounds in Closed Environments Using Gas Chromatograph/Differential Mobility Spectrometer (United States)

    Limero, Thomas; Cheng, Patti


    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.

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

    Directory of Open Access Journals (Sweden)

    T. Hansen


    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.

  10. Gas chromatographic sulphur speciation in heavy crude oil using a modified standard D5623 method and microfluidic Deans switching. (United States)

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


    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.

  11. Simple, specific analysis of organophosphorus and carbamate pesticides in sediments using column extraction and gas chromatography (United States)

    Belisle, A.A.; Swineford, D.M.


    A simple, specific procedure was developed for the analysis of organophosphorus and carbamate pesticides in sediment. The wet soil was mixed with anhydrous sodium sulfate to bind water and the residues were column extracted in acetone:methylene chloride (1:l,v/v). Coextracted water was removed by additional sodium sulfate packed below the sample mixture. The eluate was concentrated and analyzed directly by capillary gas chromatography using phosphorus and nitrogen specific detectors. Recoveries averaged 93 % for sediments extracted shortly after spiking, but decreased significantly as the samples aged.

  12. Fast temperature programming in gas chromatography using resistive heating

    NARCIS (Netherlands)

    Dallüge, J.; Ou-Aissa, R.; Vreuls, J.J.; Brinkman, U.A.T.; Veraart, J.R.


    The features of a resistive-heated capillary column for fast temperature-programmed gas chromatography (GC) have been evaluated. Experiments were carried out using a commercial available EZ Flash GC, an assembly which can be used to upgrade existing gas chromatographs. The capillary column is placed

  13. Thermal desorption-Gas chromatographic methodology for the determination of residual solvents in mesoporous silica. (United States)

    Asfaw, Adissu Alemayehu; Wolfs, Kris; Schepdael, Ann Van; Adams, Erwin


    In this work, thermal desorption-gas chromatography-flame ionization detection (TD-GC-FID) was adapted to enable the determination of residual solvents (RS) in mesoporous silica (MPSi). MPSi is often utilized in various pharmaceutical formulations or drug delivery systems and the accurate determination of RS is an important part of pharmaceutical quality control. Seven commonly used solvents (methanol, ethanol, acetone, isopropanol, dichloromethane, tetrahydrofuran and hexafluoroisopropanol) were evaluated in combination with 3 types of MPSi having pore sizes of 2-3, 15 and 25nm. Validation results showed general recovery values >98% and good linearity over the concentration ranges studied. The limits of detection (LOD) and limits of quantification (LOQ) for the different solvents ranged from 0.03 to 0.08μg and from 0.1 to 0.2μg per tube, respectively. Verification of the accuracy of the TD method was investigated by using an alternative method based on complete dissolution of MPSi in hydrofluoric acid (HF) followed by full evaporation headspace-GC (HS-GC). The results obtained from both procedures were not statistically different (p>0.05) when applied to actual experimental drug samples consisting of itraconazole loaded on MPSi. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Gas chromatographic and electron spin resonance investigations of gamma-irradiated frog legs

    International Nuclear Information System (INIS)

    Morehouse, K.M.; Ku, Yuoh; Albrecht, H.L.; Yang, G.C.


    Several very sensitive techniques to measure radiation-induced products in frog legs were investigated. Presented here are results from the use of electron spin resonance (ESR) spectroscopy and capillary gas chromatography (GC) to measure radiolysis products in γ-irradiated frog legs. When bone is irradiated, a characteristic ESR signal develops and is easily measured. The intensity of the ESR signal is dose-dependent and stable for several months at room temperature. When triglycerides or fatty acids are irradiated, some of the major stable products formed are hydrocarbons with one less carbon than the precursor fatty acids. These hydrocarbons are formed as the result of the loss of CO 2 during various free radical reactions. A capillary GC procedure was developed to monitor the formation of these hydrocarbons in γ-irradiated frog legs. Since frog legs contain large amounts of palmitic, stearic, oleic, and linoleic acids, the formation of the hydrocarbons (pentadecane, heptadecane, 8-heptadecene, and 6,9-heptadecadiene, respectively) from the decarboxylation of these fatty acids was monitored. The yields of these hydrocarbons were found to be linear with applied dose. A sample from a lot of imported frog legs that were believed to have been treated with ionizing radiation was also analyzed. The ESR technique, in conjunction with the GC data on the hydrocarbons, appears to be a useful approach for identifying and monitoring frog legs that have been treated with ionizing radiation. (author)

  15. A gas chromatographic method for the identification of gamma-irradiated frog legs

    International Nuclear Information System (INIS)

    Morehouse, K.M.; Yuoh Ku


    When triglycerides or fatty acids are irradiated, some of the major stable products formed are hydrocarbons with one less carbon than the parent fatty acids. These hydrocarbons are formed as the result of the loss of CO 2 via various free radical reactions. A procedure has been developed utilizing capillary gas chromatography (GC) to monitor the formation of these hydrocarbons in gamma-irradiated frog legs. Since frog legs contain large amounts of palmitic, stearic, oleic, and linoleic acids, the formation of the hydrocarbons (pentadecane, heptadecane, 8-heptadecene, and 6,9-heptadecadiene, respectively) from the decarboxylation of these fatty acids was monitored. The yield of these hydrocarbons was found to be linear with applied dose. A sample from a lot of imported frog legs that were believed to have been irradiated was also analyzed. The results obtained from the GC determination of the hydrocarbons compared favorably with those obtained by using electron spin resonance to monitor the free radicals trapped in the frog leg bone after irradiation. (author)

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

    International Nuclear Information System (INIS)

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


    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

  17. Gas chromatographic-mass spectrometric urinary metabolome analysis to study mutations of inborn errors of metabolism. (United States)

    Kuhara, Tomiko


    Urine contains numerous metabolites, and can provide evidence for the screening or molecular diagnosis of many inborn errors of metabolism (IEMs). The metabolomic analysis of urine by the combined use of urease pretreatment, stable-isotope dilution, and capillary gas chromatography/mass spectrometry offers reliable and quantitative data for the simultaneous screening or molecular diagnosis of more than 130 IEMs. Those IEMs include hyperammonemias and lactic acidemias, and the IEMs of amino acids, pyrimidines, purines, carbohydrates, and others including primary hyperoxalurias, hereditary fructose intolerance, propionic acidemia, and methylmalonic acidemia. Metabolite analysis is comprehensive for mutant genotypes. Enzyme dysfunction-either by the abnormal structure of an enzyme/apoenzyme, the reduced quantity of a normal enzyme/apoenzyme, or the lack of a coenzyme-is involved. Enzyme dysfunction-either by an abnormal regulatory gene, abnormal sub-cellular localization, or by abnormal post-transcriptional or post-translational modification-is included. Mutations-either known or unknown, common or uncommon-are involved. If the urine metabolome approach can accurately observe quantitative abnormality for hundreds of metabolites, reflecting 100 different disease-causing reactions in a body, then it is possible to simultaneously detect different mutant genotypes of far more than tens of thousands. (c) 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:814-827, 2005.

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

    Directory of Open Access Journals (Sweden)

    Yohannes Alen


    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.



    Hattori, Hideki; Arinobu, Tetsuya; Iwai, Masae; Suzuki, Osamu; Seno, Hiroshi


    A new internal surface reversed phase column (Shim-pack MAYI-ODS) was used for analysis of morphine, codeine and cocaine in human sera by LC/MS/MS. The column enabled direct injection of crude biological samples without pretreatment realizing a rapid analytical procedure. Therecoveries of morphine, codeine and cocaine spiked into human sera were 50-60 %. The regression equations for morphine, codeine and cocaine in sera, using atropine as internal standard, showed good linearity in the ranges...

  20. Measurement of the eddy dispersion term in chromatographic columns. II. Application to new prototypes of 2.3 and 3.2 mm I.D. monolithic silica columns. (United States)

    Gritti, Fabrice; Guiochon, Georges


    The mass transfer mechanisms in silica monolithic columns of the second generation were investigated, using four research samples (two 2.3 mm × 50 mm and two 3.2 mm × 50 mm silica rods) provided by their manufacturer. The heights equivalent to a theoretical plate (HETP) of these columns were measured in a range of mobile phase velocities, following a meticulous experimental protocol. The coefficients of the van Deemter equation (longitudinal diffusion term B/u(S), skeleton/eluent mass transfer resistance term Cu(S), and eddy diffusion term A) were determined. The protocol includes using the peak parking method (to determine the longitudinal diffusion term), an accurate model of effective diffusion in silica monolithic structures (to determine the skeleton/eluent mass transfer resistance term), and an accurate method to measure the column HETP and determine the eddy diffusion term. The results show that the minimum plate heights of these new monolithic columns ranges between 4 and 5 μm, three to four times lower than those observed for monolithic columns of the first generation. A detailed analysis of the eddy diffusion term demonstrates that this improvement in column efficiency is partly explained by the reduction of the domain size (the sum of the skeleton and throughpore sizes, -40%) but mostly by an increase of the radial homogeneity of the monolithic rods. The columns of this second generation exhibit residual trans-column relative velocity biases as low a 1.4% (instead of 3% for previous columns), a value which is comparable to those observed in 4.6mm I.D. columns packed with sub-3 μm core-shell particles, with which they might become competitive. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Italian and Argentine olive oils: a NMR and gas chromatographic study

    Directory of Open Access Journals (Sweden)

    Segre, Annalaura


    Full Text Available High-field Nuclear Magnetic Resonance (NMR spectroscopy and Gas Chromatography (GC were used to analyze 16 monovarietal olive oils obtained from few matched Mediterranean cultivars grown in experimental fields located in Italy and in the Catamarca region of Argentina. The Catamarca region is characterized by extreme pedoclimatic conditions and by a wild spontaneous vegetation. The proposed sampling allows to study the effect of different pedoclimatic conditions on olive oil composition. GC gives the fatty acid profile of olive oil samples. 1H and 13C NMR techniques provide different information: the 1H NMR spectrum allows the measurement of minor components of olive oils such as b-sytosterol, hexanal, trans-2-hexenal, formaldehyde, squalene, cycloartenol and linolenic acid; the 1C NMR spectrum allows to obtain information about glycerol tri-esters of olive oils, i.e., about their acyl composition and positional distribution on glycerol moiety. All the NMR and GC results have been submitted to Linear Discriminant Analysis (LDA and Tree Cluster Analysis (TCA. A careful analysis of the statistical results allows to select the Mediterranean cultivars less affected by the climatic conditions present in the Catamarca region. The selected cultivars produce olive oils which keep their Mediterranean characteristics and which can be proposed as colonizing plants in this wild Argentine region.La espectroscopía de Resonancia Magnética Nuclear de alta resolución (RMN y Cromatografía Gaseosa (CG fueron utilizadas para analizar 16 monovariedades de aceites de oliva, obtenidas de algunos olivares Mediterráneos cultivados contemporáneamente en campos experimentales localizados en Italia y en la región de Catamarca en Argentina. Estas muestras permiten estudiar diferentes condiciones pedoclimáticas en la composición de los aceite de oliva. La CG proporciona el perfil en ácidos grasos de los aceites de oliva y las técnicas RMN 1H y RMN 13C suministran

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

    International Nuclear Information System (INIS)

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


    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)

  3. Wind driven vertical transport in a vegetated, wetland water column with air-water gas exchange (United States)

    Poindexter, C.; Variano, E. A.


    gas transfer coefficient, k, for both a vegetated condition and a control condition (no cylinders). The presence of cylinders in the tank substantially increased the rate of the gas transfer. For the highest wind speed, the gas transfer coefficient was several times higher when cylinders were present compared to when they were not. The gas transfer coefficient for the vegetated condition also proved sensitive to wind speed, increasing markedly with increasing mean wind speeds. Profiles of dissolved oxygen revealed well-mixed conditions in the bulk water column following prolonged air-flow above the water surface, suggesting application of the thin-film model is appropriate. The enhanced gas exchange observed might be explained by increased turbulent kinetic energy within the water column and the anisotropy of the cylinder array, which constrains horizontal motions more than vertical motions. Improved understanding of gas exchange in vegetated water columns may be of particularly use to investigations of carbon fluxes and soil accretion in wetlands. Reference: Nepf, H. (1999), Drag, turbulence, and diffusion in flow through emergent vegetation, Water Resour. Res., 35(2), 479-489.

  4. Large volume cold on-column injection for gas chromatography-negative chemical ionization-mass spectrometry analysis of selected pesticides in air samples. (United States)

    Bailey, Renata; Belzer, Wayne


    A new gas chromatographic method is described for the analysis of fungicides captan, captafol, and folpet from organic extracts of air samples using large volume injection (LVI) via a cold on-column (COC) inlet coupled with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). Although standard split/splitless injection due to high injection port temperatures (>225 degrees C) have been shown to degrade these thermally labile fungicides, COC injection minimizes degradation. Insecticides such as chlorpyrifos and diazinon were also examined to show added selectivity. By using a solvent vapor exit with the COC inlet, injection volumes of 10-100 microL can be made to lower detection levels. GC-NCI-MS was compared to GC-electron impact ionization-mass spectrometry for each pesticide using LVI-COC injections and was found to be 2-80 times more sensitive, depending on the pesticide. Method detection limit (MDL) values with 100 microL injections were 2.5 microg L-1 for captan, folpet, and diazinon, 5.0 microg L-1 captafol, and 1.0 microg L-1 for chlorpyrifos, with the normal working range examined for sample analysis from MDL to 100 microg L-1. Detection of all pesticides except captafol, used only in the United States but not Canada, was demonstrated from air samples taken from Abbotsford, British Columbia, Canada.

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

    Directory of Open Access Journals (Sweden)

    V. Sinha


    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

  6. Technical Note: Detection of gas bubble leakage via correlation of water column multibeam images

    Directory of Open Access Journals (Sweden)

    J. Schneider von Deimling


    Full Text Available Hydroacoustic detection of natural gas release from the seafloor has been conducted in the past by using singlebeam echosounders. In contrast, modern multibeam swath mapping systems allow much wider coverage, higher resolution, and offer 3-D spatial correlation. Up to the present, the extremely high data rate hampers water column backscatter investigations and more sophisticated visualization and processing techniques are needed. Here, we present water column backscatter data acquired with a 50 kHz prototype multibeam system over a period of 75 seconds. Display types are of swath-images as well as of a "re-sorted" singlebeam presentation. Thus, individual and/or groups of gas bubbles rising from the 24 m deep seafloor clearly emerge in the acoustic images, making it possible to estimate rise velocities. A sophisticated processing scheme is introduced to identify those rising gas bubbles in the hydroacoustic data. We apply a cross-correlation technique adapted from particle imaging velocimetry (PIV to the acoustic backscatter images. Temporal and spatial drift patterns of the bubbles are assessed and are shown to match very well to measured and theoretical rise patterns. The application of this processing to our field data gives clear results with respect to unambiguous bubble detection and remote bubble rise velocimetry. The method can identify and exclude the main source of misinterpretations, i.e. fish-mediated echoes. Although image-based cross-correlation techniques are well known in the field of fluid mechanics for high resolution and non-inversive current flow field analysis, we present the first application of this technique as an acoustic bubble detector.

  7. 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; E.A. Ogunsakin; P.E.P. Ilukhor


    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 r...

  8. Automated column liquid chromatographic determination of amoxicillin and cefadroxil in bovine serum and muscle tissue using on-line dialysis for sample preparation

    NARCIS (Netherlands)

    Snippe, N; van de Merbel, N C; Ruiter, F P; Steijger, O M; Lingeman, H; Brinkman, U A


    A fully automated method is described for the determination of amoxicillin and cefadroxil in bovine serum and muscle tissue. The method is based on the on-line combination of dialysis and solid-phase extraction for sample preparation, and column liquid chromatography with ultraviolet detection. In

  9. Evaluation of the performance of thermal diffusion column separating binary gas mixtures with continuous draw-off

    International Nuclear Information System (INIS)

    Kitamoto, Asashi; Shimizu, Masami; Takashima, Yoichi


    Advanced transport relations involving three column constants, H sup(σ), K sub(c)sup(σ) and K sub(d)sup(σ), are developed to describe the separation performance of a thermal diffusion column with continuous draw-off. These constants were related to some integral functions of velocity profile, temperature distribution, density of gas mixture and characteristic values of transport coefficients. The separation of binary gas mixture by this technique was so effective that three reasonable factors had to be introduced into the column constants in the theory. They are a circulation constant of natural convection, a definition of characteristic mean temperature and a definition of mean composition over the column. The separation performance and the column constants also varied with the distortion of velocity profile due to continuous draw-off from the top or the bottom of column. However, its effect was not large, compared with the other factors mentioned above. The theory presented here makes possible to estimate the separation performance of hot-wire type thermal diffusion column with high accuracy. (auth.)

  10. Maximum Potential Hydrogen Gas Retention in the sRF Resin Ion Exchange Column for the LAWPS Process

    Energy Technology Data Exchange (ETDEWEB)

    Gauglitz, Phillip A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wells, Beric E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bottenus, Courtney LH [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Schonewill, Philip P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)


    The Low-Activity Waste Pretreatment System (LAWPS) is being developed to provide treated supernatant liquid from the Hanford tank farms directly to the Low-Activity Waste (LAW) Vitrification Facility at the Hanford Tank Waste Treatment and Immobilization Plant. The design and development of the LAWPS is being conducted by Washington River Protection Solutions, LLC. A key process in LAWPS is the removal of radioactive Cs in ion exchange (IX) columns filled with spherical resorcinol-formaldehyde (sRF) resin. One accident scenario being evaluated is the loss of liquid flow through the sRF resin bed after it has been loaded with radioactive Cs and hydrogen gas is being generated by radiolysis. In normal operations, the generated hydrogen is expected to remain dissolved in the liquid and be continuously removed by liquid flow. For an accident scenario with a loss of flow, hydrogen gas can be retained within the IX column both in the sRF resin and below the bottom screen that supports the resin within the column. The purpose of this report is to summarize calculations that estimate the upper-bound volume of hydrogen gas that can be retained in the column and potentially be released to the headspace of the IX column or to process equipment connected to the IX column and, thus, pose a flammability hazard.

  11. [Determination of ethylene glycol in workplace air by capillary column gas chromatography]. (United States)

    Li, Tiandi; Lin, Yiran; Zhang, Wen; He, Juntao


    To establish the method of capillary column gas chromatography for determination of ethylene glycol in workplace air. Ethylene glycol in workplace air was collected with silicone tube, desorbed with methanol, separated with FFAP (nitroterephthalic acid-modified polyethylene glycol)capillary column, and measured with flame ionization detector. The detection limit of ethylene glycol was 0.41 mg/L, the lower limit of quantification was 1.4 mg/L, the range of measurement was 1.4~163.9 mg/L, and the minimum detectable concentration was 0.3 mg/m3 (1.5 L of air was collected as the sample). This method had a good repeatability, the relative standard deviation was 1.4%~5.2%, the average desorption efficiency was 94.4%~101.7%, and the sampling efficiency was 99.2%~100%. The penetrating capacity of 200 mg silicone was higher than 6.9 mg, and the samples could be preserved for 14 days at room temperature. The method has a low detection limit, high accuracy, and good precision, which is feasible for determination of ethylene glycol in workplace air.

  12. Balloon-Borne Full-Column Greenhouse Gas Profiling Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Marc L [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)


    The vertical distributions of CO2, CH4, and other gases provide important constraints for the determination of terrestrial and ocean sources and sinks of carbon and other biogeochemical processes in the Earth system. The DOE Biological and Environmental Research Program (DOE-BER) and the NOAA Earth System Research Laboratory (NOAA-ESRL) collaborate to quantify the vertically resolved distribution of atmospheric carbon-cycle gases (CO2, and CH4) within approximately 99% of the atmospheric column at the DOE ARM Southern Great Plains Facility in Oklahoma. In 2015, flights were delayed while research at NOAA focused on evaluating sources of systematic errors in the gas collection and analysis system and modifying the sampling system to provide duplicate air samples in a single flight package. In 2017, we look forward to proposing additional sampling and analysis at ARM-SGP (and other sites) that characterize the vertical distribution of CO2 and CH4 over time and space.

  13. Highly efficient high-performance liquid chromatographic separation of xylene isomers and phthalate acid esters on a homemade DUT-67(Zr) packed column. (United States)

    Chen, Sha; Li, Xiao-Xin; Feng, Fan; Li, Sumei; Han, Jia-Hui; Jia, Zi-Yi; Shu, Lun; Somsundaran, P; Li, Jian-Rong


    In this study, the baseline separations of xylene isomers and phthalate acid esters on a homemade DUT-67(Zr) packed column were achieved, respectively. The high selectivity for xylene isomers and phthalate acid esters was obtained with the increase of temperature and decrease of the retention time. The hydrophobicity of xylene isomers and phthalate acid esters caused the different separation time on the DUT-67(Zr) packed column. The relative standard deviation values of retention time, peak area, peak height and half peak width for five repeat separation of the xylene isomers were 0.26-0.35, 2.11-2.26, 1.51-2.03, and 0.29-0.77%, and the values of the phthalate acid esters on DUT-67(Zr) column were 0.1-0.4, 4.4-5.2, 3.9-6.3, and 0.6-2.1%, respectively. The thermodynamic properties indicated that the separation of xylene isomers was controlled by ΔH and ΔS, but the separation of phthalate acid esters was mainly controlled by ΔS. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  14. Simultaneous spectrophotometric determination of phosphate and silicate ions in river water by using ion-exclusion chromatographic separation and post-column derivatization

    International Nuclear Information System (INIS)

    Nakatani, Nobutake; Kozaki, Daisuke; Masuda, Wakako; Nakagoshi, Nobukazu; Hasebe, Kiyoshi; Mori, Masanobu; Tanaka, Kazuhiko


    The simultaneous spectrophotometric determination of phosphate and silicate ions in river water was examined by using ion-exclusion chromatography and post-column derivatization. Phosphate and silicate ions were separated by the ion-exclusion column packed with a polymethacrylate-based weakly acidic cation-exchange resin in the H + -form (TSKgel Super IC-A/C) by using ultra pure water as an eluent. After the post-column derivatization with molybdate and ascorbic acid, so-called molybdenum-blue, both ions were determined simultaneously by spectrophotometry. The effects of sulfuric acid, sodium molybdate and ascorbic acid concentrations and reaction coil length, which have relation to form the reduced complexes of molybdate and ions, on the detector response for phosphate and silicate ions were investigated. Under the optimized conditions (color-forming reactant, 50 mM sulfuric acid-10 mM sodium molybdate; reducing agent, 50 mM ascorbic acid; reaction coil length, 6 m), the calibration curves of phosphate and silicate ions were linear in the range of 50-2000 μg L -1 as P and 250-10,000 μg L -1 as Si. This method was successfully applied to water quality monitoring of Kurose-river watershed and it suggested that the effluent from a biological sewage treatment plant was significant source of phosphate ion in Kurose-river water

  15. Use of pressure drop profiles to assess the accuracy of Total Pore Blocking measurements of the external porosity of chromatographic columns. (United States)

    Liekens, Anuschka; Denayer, Joeri; Desmet, Gert


    By comparing the pressure drop in a column where the meso-pores of the particles have been blocked using the Total Pore Blocking (TPB) method to measure the interstitial volume of the column with that in the same column when the particle meso-pores are fully open, it could be demonstrated in a very sensitive way that the interstitial volume is completely devoid of any significant amount of remaining pore blocking agent in the final phase of a TPB experiment. Monitoring the pressure signal until it returns to its original value can hence be used as a reliable indicator that all blocking agent has been removed from the interstitial void at the end of the flushing period. As a consequence, any small molecular weight dead volume marker that is employed in this phase can explore the full interstitial volume, so that the value of the latter can be measured without being underestimated by the fact that some fractions of the interstitial void would still be occupied by the blocking agent. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. Validated column high-performance liquid chromatographic method for determination of aspirin and clopidogrel in combined tablets in the presence of degradation products formed under ICH-recommended stress conditions. (United States)

    Kachhadia, Pankaj K; Doshi, Ashish S; Joshi, Hitendra S


    The development and validation of a column high-performance liquid chromatographic assay method for the determination of aspirin and clopidogrel in tablet formulation are described. The combination formulation was subjected to International Conference on Harmonization-recommended stress conditions. Separation of the drugs from the degradation products formed under stress conditions was achieved on an octasilyl (C8) column using 0.3% orthophosphoric acid-acetonitrile (65 + 35, v/v) mobile phase. The method was validated for specificity, linearity, limits of detection and quantification, precision, accuracy, and robustness. The method was found to be specific against placebo interference and during the forced degradation. The response was linear in the concentration range of 30.0-120.0 microg/mL for aspirin and 15.0-60.0 microg/mL for clopidogrel, with a correlation coefficient of 0.9999 for both. The relative standard deviation values for intra- and interday precision were aspirin and 98.20 and 100.35% for clopidogrel. Stress testing showed degradation products that were well-separated from the parent compound, confirming the stability-indicating capacity of the method.

  17. Nitrogen transformations and greenhouse gas emissions from a riparian wetland soil: An undisturbed soil column study

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Leoz, Borja [Department of Chemical and Environmental Engineering, University of the Basque Country, UPV/EHU, E-48013 Bilbao (Spain); Antigueedad, Inaki [Department of Geodynamic, University of the Basque Country, UPV/EHU, E-48940 Leioa (Spain); Garbisu, Carlos [Department of Ecosystems, NEIKER-Tecnalia, E-48160 Derio (Spain); Ruiz-Romera, Estilita, E-mail: [Department of Chemical and Environmental Engineering, University of the Basque Country, UPV/EHU, E-48013 Bilbao (Spain)


    Riparian wetlands bordering intensively managed agricultural fields can act as biological filters that retain and transform agrochemicals such as nitrate and pesticides. Nitrate removal in wetlands has usually been attributed to denitrification processes which in turn imply the production of greenhouse gases (CO{sub 2} and N{sub 2}O). Denitrification processes were studied in the Salburua wetland (northern Spain) by using undisturbed soil columns which were subsequently divided into three sections corresponding to A-, Bg- and B2g-soil horizons. Soil horizons were subjected to leaching with a 200 mg NO{sub 3}{sup -} L{sup -1} solution (rate: 90 mL day{sup -1}) for 125 days at two different temperatures (10 and 20 {sup o}C), using a new experimental design for leaching assays which enabled not only to evaluate leachate composition but also to measure gas emissions during the leaching process. Column leachate samples were analyzed for NO{sub 3}{sup -} concentration, NH{sub 4}{sup +} concentration, and dissolved organic carbon. Emissions of greenhouse gases (CO{sub 2} and N{sub 2}O) were determined in the undisturbed soil columns. The A horizon at 20 {sup o}C showed the highest rates of NO{sub 3}{sup -} removal (1.56 mg N-NO{sub 3}{sup -} kg{sup -1} DW soil day{sup -1}) and CO{sub 2} and N{sub 2}O production (5.89 mg CO{sub 2} kg{sup -1} DW soil day{sup -1} and 55.71 {mu}g N-N{sub 2}O kg{sup -1} DW soil day{sup -1}). For the Salburua wetland riparian soil, we estimated a potential nitrate removal capacity of 1012 kg N-NO{sub 3}{sup -} ha{sup -1} year{sup -1}, and potential greenhouse gas emissions of 5620 kg CO{sub 2} ha{sup -1} year{sup -1} and 240 kg N-N{sub 2}O ha{sup -1} year{sup -1}. - Research Highlights: {yields}A new experimental design is proposed for leaching assays to simulate nitrogen transformations in riparian wetland soil. {yields}Denitrification is the main process responsible for nitrate removal in the riparian zone of Salburua wetland. {yields

  18. Evaluation of complexing agents and column temperature in ion chromatographic separation of alkali metals, alkaline earth metals and transition metals ion

    International Nuclear Information System (INIS)

    Kelkar, Anoop; Pandey, Ashish; Name, Anil B.; Das, D.K.; Behere, P.G.; Mohd Afzal


    The aim of ion chromatography method development is the resolution of all metal ions of interests. Resolution can be improved by changing the selectivity. Selectivity in chromatography can be altered by changes in mobile phase (eg eluent type, eluent strength) or through changes in stationary phase. Temperature has been used in altering the selectivity of particularly in reversed phase liquid chromatography and ion exchange chromatography. Present paper describe the retention behaviour of alkali metals, alkaline earth metals and transition metal ions on a silica based carboxylate function group containing analyte column. Alkali metals, alkaline earth metals and transition metal ions were detected by ion conductivity and UV-VIS detectors respectively

  19. Evaluation of a subsurface oxygenation technique using colloidal gas aphron injections into packed column reactors

    International Nuclear Information System (INIS)

    Wills, R.A.; Coles, P.


    Bioremediation may be a remedial technology capable of decontaminating subsurface environments. The objective of this research was to evaluate the use of colloidal gas aphron (CGA) injection, which is the injection of micrometer-size air bubbles in an aqueous surfactant solution, as a subsurface oxygenation technique to create optimal growth conditions for aerobic bacteria. Along with this, the capability of CGAs to act as a soil-washing agent and free organic components from a coal tar-contaminated matrix was examined. Injection of CGAs may be useful for remediation of underground coal gasification (UCG) sites. Because of this, bacteria and solid material from a UCG site located in northeastern Wyoming were used in this research. Colloidal gas aphrons were generated and pumped through packed column reactors (PCRS) containing post-burn core materials. For comparison, PCRs containing sand were also studied. Bacteria from this site were tested for their capability to degrade phenol, a major contaminant at the UCG site, and were also used to bioaugment the PCR systems. In this study we examined: (1) the effect of CGA injection on dissolved oxygen concentrations in the PCR effluents, (2) the effect of CGA, H 2 O 2 , and phenol injections on bacterial populations, (3) the stability and transport of CGAs over distance, and (4) CGA injection versus H 2 O 2 injection as an oxygenation technique

  20. Determination of triazine and chloroacetanilide herbicides in soils by microwave-assisted extraction (MAE) coupled to gas chromatographic analysis with either GC-NPD or GC-MS. (United States)

    Vryzas, Zisis; Papadopoulou-Mourkidou, Euphemia


    A simple and rapid method based on microwave-assisted extraction (MAE) coupled to gas chromatographic analysis was developed for the analysis of triazine (atrazine, cyanazine, metribuzine, simazine and deethylatrazine, and deisopropylatrazine) and chloroacetanilide (acetochlor, alachlor, and metolachlor) herbicide residues in soils. Soil samples are processed by MAE for 5 min at 80 degrees C in the presence of acetonitrile (20 mL/sample). Mean recovery values of most solutes are >80% in the 10 to 500 microg/kg fortification range with respective RSDs (relative standard deviations) NPD) or a mass spectrometric detector (GC-MS).

  1. Analysis of polycyclic aromatic hydrocarbons I. Determination by gas chromatography with glass and fused silica capillary columns

    International Nuclear Information System (INIS)

    Perez, M. M.; Gonzalez, D.


    A study of the analysis by gas chromatography of aromatic polycyclic hydrocarbons is presented. The separation has been carried out by glass and fused silica capillary column. The limitations and the advantages of the procedure are discussed in terms of separation efficiency, sensitivity and precision. (Author) 17 refs

  2. Analysis of polycyclic aromatic hydrocarbons. I. Determination by gas chromatography with glass and fused solica capillary columns

    International Nuclear Information System (INIS)

    Perez Garcia, M.; Gonzalez, D.


    A study of the analysis by gas chromatography of aromatic polycyclic hydrocarbons is presented. The separation has been carried out by glass and fused silice capillary column. The limitations and the advantages of the procedure are discussed in terms of separation efficiency, sensitivity and precision. (author). 3 figs., 17 refs

  3. High-performance liquid chromatographic separations of stereoisomers of chiral basic agrochemicals with polysaccharide-based chiral columns and polar organic mobile phases. (United States)

    Matarashvili, Iza; Shvangiradze, Iamze; Chankvetadze, Lali; Sidamonidze, Shota; Takaishvili, Nino; Farkas, Tivadar; Chankvetadze, Bezhan


    The separation of the stereoisomers of 23 chiral basic agrochemicals was studied on six different polysaccharide-based chiral columns in high-performance liquid chromatography with various polar organic mobile phases. Along with the successful separation of analyte stereoisomers, emphasis was placed on the effect of the chiral selector and mobile phase composition on the elution order of stereoisomers. The interesting phenomenon of reversal of enantiomer/stereoisomer elution order function of the polysaccharide backbone (cellulose or amylose), type of derivative (carbamate or benzoate), nature, and position of the substituent(s) in the phenylcarbamate moiety (methyl or chloro) and the nature of the mobile phase was observed. For several of the analytes containing two chiral centers all four stereoisomers were resolved with at least one chiral selector/mobile phase combination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. An integrated methodological approach to the computer-assisted gas chromatographic screening of basic drugs in biological fluids using nitrogen selective detection. (United States)

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


    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.

  5. Evidence of Cr(VI) formation during analysis of leather Proposal of an alternative method of analysis through the ion-chromatographic approach and post-column reaction. (United States)

    Pastore, Paolo; Favaro, Gabriella; Ballardin, Alberto; Danieletto, Daniele


    The formation of Cr(VI) in Cr(III) tanned leather, in neutral and alkaline solution, has been demonstrated by means of crossed experiments using different pH buffers, ethylenediaminetetraacetic acid as Cr(III) complexing agent and NaCl solutions. According to the found results the composition of the extracting solution suitable to extract Cr(VI) amount present in leather was pH 4.4 (which is also the tanned leather natural pH) and 5% NaCl (w/v). Interferences coming from coloured compounds have been eliminated with suitable SPE cartridges. A new protocol for the analysis of Cr(VI) based on ion chromatography and a diphenylcarbazide post-column reaction has been implemented. The use of a large volume injection loop (500mul) allowed to obtain a very low quantification limit (0.15mgkg(-1)) despite the low amount of leather extracted (0.2g with respect to 2.0g used by the IUC 18 official method). Evidence of the transient nature of Cr(VI) in leather requires using the external calibration procedure for the correct quantification of the species.

  6. Capillary gas chromatographic detection of invert sugar in heated, adulterated, and adulterated and heated apple juice concentrates employing the equilibrium method. (United States)

    Low, N H; McLaughlin, M; Hofsommer, H J; Hammond, D A


    The equilibrium method is introduced for the detection of invert sugar addition to apple juice. The method consists of a pre-equilibration of the sample with dry pyridine at 50 degrees C for 20 min followed by the addition of trimethylsilylimidazole and heating at 75 degrees C for 40 min. The resulting derivatized carbohydrates are then analyzed by capillary gas chromatography. This method was successfully used by independent laboratories to distinguish heated pure, intentionally adulterated (with invert sugar), and intentionally adulterated and then heated apple juice concentrates. The equilibrium method was shown to give significantly lower coefficients of variation for this sample set when compared to the original capillary gas chromatographic method. In addition, these results indicate that it may also be an effective method for the detection of medium invert sugar, depending on the level of the fingerprint oligosaccharides in this sweetener.

  7. Unfolding and aggregation of a glycosylated monoclonal antibody on a cation exchange column. Part I. Chromatographic elution and batch adsorption behavior. (United States)

    Guo, Jing; Zhang, Shaojie; Carta, Giorgio


    A glycosylated IgG2 monoclonal antibody exhibits a two-peak elution behavior when loaded on a strong cation exchange column and eluted with either a linear salt gradient or two salt steps at increasing salt concentrations. The two-peak behavior is more pronounced for conditions where the initial antibody binding is stronger, i.e. at lower pH and buffer concentration, where the hold time prior to elution is longer, where the protein mass load is lower, and where the load flow rate is higher. The effect is also dependent on the resin type, being prominent for the polymer-functionalized resin Fractogel EMD SO₃(-) and virtually absent for a macroporous resin with similar backbone but no grafted polymers. Size exclusion chromatography and dynamic light scattering show that the early eluting peak consists exclusively of the native monomeric species while the late eluting peak is a mixture of monomeric and aggregated species. Batch adsorption/desorption experiments show that the bound protein can be desorbed in two steps, with a fraction desorbed in 0.33 M NaCl, corresponding to native monomer, and a second fraction desorbed in 1M NaCl. The latter fraction decreases with protein mass load and becomes almost negligible when the resin is initially completely saturated with protein. Confocal laser scanning microscopy showed that the two-peak elution/desorption behavior is related to the unique kinetics of protein binding in the Fractogel resin. Following partial loading of the resin, the bound protein migrates toward the center of the particles during a hold step and is redistributed across the particle volume attaining low local bound protein concentrations. For these conditions the protein is apparently destabilized forming a strongly-bound unfolded intermediate that, in turn, generates aggregates upon elution in high salt. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. CARVE: L2 Column Gas and Uncertainty from Airborne FTS, Alaska, 2012-2015 (United States)

    National Aeronautics and Space Administration — This data set provides total vertical column O2, CO2, CH4, CO, and H2O, as well as dry-air columns of CO2, CH4, CO, and H2O from airborne campaigns over the Alaskan...

  9. Determination of valproic acid (DI-N-propyl acetic acid) in plasma by gas-liquid chromatography with pre-column butylation

    NARCIS (Netherlands)

    Hulshoff, A.; Roseboom, H.


    A gas-liquid chromatographic procedure for the determination of the anticonvulsant drug valproic acid in plasma or serum is described. Valproic acid is extracted from acidified plasma (or serum) into toluene containing octanoic acid as the internal standard. The toluene layer is back extracted with

  10. Characteristic chromatographic fingerprint study of short-chain fatty acids in human milk, infant formula, pure milk and fermented milk by gas chromatography-mass spectrometry. (United States)

    Jiang, Zhenzuo; Liu, Yanan; Zhu, Yan; Yang, Jing; Sun, Lili; Chai, Xin; Wang, Yuefei


    Human milk, infant formula, pure milk and fermented milk as food products or dietary supplements provide a range of nutrients required to both infants and adults. Recently, a growing body of evidence has revealed the beneficial roles of short-chain fatty acids (SCFAs), a subset of fatty acids produced from the fermentation of dietary fibers by gut microbiota. The objective of this study was to establish a chromatographic fingerprint technique to investigate SCFAs in human milk and dairy products by gas chromatography coupled with mass spectrometry. The multivariate method for principal component analysis assessed differences between milk types. Human milk, infant formula, pure milk and fermented milk were grouped independently, mainly because of differences in formic acid, acetic acid, propionic acid and hexanoic acid levels. This method will be important for the assessment of SCFAs in human milk and various dairy products.

  11. Gas chromatographic determination of pesticides in vegetable samples by sequential positive and negative chemical ionization and tandem mass spectrometric fragmentation using an ion trap analyser. (United States)

    Hernando, M D; Agüera, A; Fernández-Alba, A R; Piedra, L; Contreras, M


    A selective and sensitive chromatographic method is described for the determination of nine organochlorine and organophosphorus pesticides in vegetable samples by gas chromatography-mass spectrometry. The proposed method combines the use of positive and negative chemical ionisation and tandem mass spectrometric fragmentation, resulting in a significant increase in selectivity and allowing the simultaneous confirmation and quantification of trace levels of pesticides in complex vegetable matrices. Parameters relative to ionisation and fragmentation processes were optimised to obtain maximum sensitivity. Repeatability and reproducibility studies yielded relative standard deviations lower than 25% in all cases. Identification criteria, such as retention time and relative abundance of characteristic product ions, were also evaluated in order to guarantee the correct identification of the target compounds. The method was applied to real vegetable samples to demonstrate its use in routine analysis.

  12. Chemometrics-enhanced one-dimensional/comprehensive two-dimensional gas chromatographic analysis for bioactive terpenoids and phthalides in Chaihu Shugan San essential oils. (United States)

    He, Min; Yang, Zhi-Yu; Yang, Tian-Biao; Ye, Ying; Nie, Juan; Hu, Yong; Yan, Pan


    Chemometrics-enhanced one-dimensional/comprehensive two-dimensional gas chromatographic (GC/GC×GC) technologies, were used to explore the compositions of Chaihu Shugan San essential oils, that were extracted from the herbal formulae by different schemes. We have shown that chemometric resolution using gas chromatographic- mass spectrometry (GC-MS) could be used for the qualitative and quantitative analysis of the majority of Terpenoids or Phthalides from herb formulae and single herbs. A GC×GC system was further optimized to achieve the increased peak capacity and the enhanced signal of the hydro-distillation sample (CSSh). When hardware bottleneck resulted from very complex sample, chemometric tools were once again applied to recover the stained information in the second dimension ( 2 D) matrix data. Heuristic evolving latent projections (HELP) could be used for two dimensional (2D) sub-matrixes Xi at n spectral detection channels, after three dimensional (3D) data splitting. For a real 3D data matrix, alternating trilinear decomposition (ATLD) algorithm could conduct regularization for an iterative trilinear decomposition procedure, by Moore-Penrose pseudoinverse computations based on singular value decomposition. After retention indices (RI) confirmation, 216 target analytes (terpenoids or phthalides) could be elucidated both in CSSh and in supercritical fluid extract (CSSs). Based on the obtained data, some potential quality markers (Q-markers) were identified which may affect the quality of the products. Finally, a "connectivity map" was plotted to describe the unique mechanisms of tradition Chinese medicine (TCM). Copyright © 2017 Elsevier B.V. All rights reserved.

  13. On-site monitoring of biogenic emissions from Eucalyptus dunnii leaves using membrane extraction with sorbent interface combined with a portable gas chromatograph system. (United States)

    Liu, Xinyu; Pawliszyn, Richard; Wang, Limei; Pawliszyn, Janusz


    Membrane extraction with sorbent interface, combined with a portable gas chromatograph system (MESI-Portable GC) for continuous on-line monitoring of biogenic volatile organic compounds (BVOCs) emissions (from leaves of Eucalytus dunnii in a greenhouse), is presented herein. A sampling chamber was designed to facilitate the extraction and identification of the BVOCs emitted by the Eucalytus dunnii leaves. Preliminary experiments, including; enrichment times, microtrap temperatures, stripping gas flow rates, and desorption temperatures were investigated to optimize experimental parameters. The main components of BVOCs released by the Eucalytus dunnii leaves were identified by comparing the retention times of peaks with those of authentic standard solutions. They were then confirmed with solid phase microextraction coupled with gas chromatography and mass spectrometry (SPME-GC-MS). BVOC emission profiles of [small alpha]-pinene, eucalyptol, and [gamma]-terpinene emitted by intact and damaged Eucalytus dunnii leaves were obtained. The findings suggest that the MESI-Portable GC system is a simple and useful tool for field monitoring changes in plant emissions as a function of time.

  14. Analysis of underivatised low volatility compounds by comprehensive two-dimensional gas chromatography with a short primary column. (United States)

    Novaes, Fábio Junior Moreira; Kulsing, Chadin; Bizzo, Humberto Ribeiro; de Aquino Neto, Francisco Radler; Rezende, Claudia Moraes; Marriott, Philip John


    Comprehensive two-dimensional gas chromatography (GC×GC) approaches with cryogenic modulation were developed for the qualitative analysis of selected low volatility compounds in raw coffee bean extracts, without derivatisation. The approaches employed short first ( 1 D) and second ( 2 D) dimension columns, specifically a 1 D 65% phenyl methyl siloxane column (11m) and a 2 D 5% phenyl methyl siloxane column (1m), which allowed elution of high molar mass compounds (e.g.>600Da). Solutes included hydrocarbons, fatty acids, diterpenes, tocopherols, sterols, diterpene esters, and di- and triacylglycerides. An oven temperature program up to 370°C was employed. The effects of experimental conditions were investigated, revealing that the GC×GC results strongly depended on the cryogenic trap T, and oven T program. An appropriate condition was selected and further applied for group type analysis of low volatility compounds in green Arabica coffee beans. Retention indices were compiled for 1D GC analysis and were similar for the composite column data in GC×GC. The elution of some compounds was confirmed by use of authentic standards. The approach allowed direct analysis of coffee extract in ethyl acetate solution, with improved analyte peak capacity (approximately 200 compounds were detected) without prior fractionation or pre-treatment of the sample. This avoided potential hydrolysis of high molar mass conjugate esters as well as degradation of thermally labile compounds such as the derivatives of the diterpenes cafestol and kahweol. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Chromatographic methods of the measurements of the chloride compounds in troposphere and stratosphere

    International Nuclear Information System (INIS)

    Lasa, J.; Rosiek, J.


    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

  16. On-line Automated Sample Preparation-Capillary Gas Chromatography for the Analysis of Plasma Samples.

    NARCIS (Netherlands)

    Louter, A.J.H.; van der Wagt, R.A.C.A.; Brinkman, U.A.T.


    An automated sample preparation module, (the automated sample preparation with extraction columns, ASPEC), was interfaced with a capillary gas chromatograph (GC) by means of an on-column interface. The system was optimised for the determination of the antidepressant trazodone in plasma. The clean-up

  17. Gas chromatography-mass spectrometry and high-performance liquid chromatographic analyses of thermal degradation products of common plastics. (United States)

    Pacáková, V; Leclercq, P A


    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 products.

  18. Global and Local Hydrodynamics of Bubble Columns – Effect of Gas Distributor.

    Czech Academy of Sciences Publication Activity Database

    Sharaf, S.; Zedníková, Mária; Růžička, Marek; Azzopardi, B.J.


    Roč. 288, MAR 15 (2016), s. 489-504 ISSN 1385-8947 R&D Projects: GA MŠk(CZ) LD13018 Grant - others:EPSRC(GB) EP/F016050/1 Institutional support: RVO:67985858 Keywords : bubble columns * wire mesh sensor * void fraction Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 6.216, year: 2016

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

    International Nuclear Information System (INIS)

    Perez Garcia, M.


    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

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

    NARCIS (Netherlands)

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


    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

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

    NARCIS (Netherlands)

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


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

    NARCIS (Netherlands)

    Roseboom, H.; Hulshoff, A.


    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,

  3. Fully automated system for the gas chromatographic characterization of polar biopolymers based on thermally assisted hydrolysis and methylation

    NARCIS (Netherlands)

    Kaal, E.; de Koning, S.; Brudin, S.; Janssen, H.-G.


    Pyrolysis-gas chromatography (Py-GC) is a powerful tool for the detailed compositional analysis of polymers. A major problem of Py-GC is that polar (bio)polymers yield polar pyrolyzates which are not easily accessible to further GC characterization. In the present work, a newly developed fully

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


    Luquin, M; Lopez, F; Ausina, V


    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.

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

    International Nuclear Information System (INIS)

    Khalisanni Khalid; Rashid Atta Khan; Sharifuddin Mohd Zain


    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)

  6. Heat transfer in hybrid fibre reinforced concrete-steel composite column exposed to a gas-fired radiant heater (United States)

    Štefan, R.; Procházka, J.; Novák, J.; Fládr, J.; Wald, F.; Kohoutková, A.; Scheinherrová, L.; Čáchová, M.


    In the paper, a gas-fired radiant heater system for testing of structural elements and materials at elevated temperatures is described. The applicability of the system is illustrated on an example of the heat transfer experiment on a hybrid fibre reinforced concrete-steel composite column specimen. The results obtained during the test are closely analysed by common data visualization techniques. The experiment is simulated by a mathematical model of heat transfer, assuming the material data of the concrete determined by in-house measurements. The measured and calculated data are compared and discussed.

  7. Mass spectral identification and gas-liquid chromatographic determination of methyl 4-chloroindolyl-3-acetate in canned and frozen peas. (United States)

    Heikes, D L


    Methyl 4-chloroindolyl-3-acetate (MCIA), a naturally occurring auxin, has been identified in canned and frozen peas by gas-liquid chromatography (GLC)/mass spectrometry. Eight samples were analyzed for MCIA using slightly modified official AOAC multiple pesticide residue procedures employing GLC with microcoulometric detection. Levels of MCIA averaged 0.20 ppm for canned peas and 0.16 ppm for frozen peas. Recovery of MCIA from a fortified sample was 40%.

  8. Contamination of the operating room by anesthetic gases and vapors. II. Gas chromatographic analysis of nitrous oxide

    Energy Technology Data Exchange (ETDEWEB)

    Cattaneo, A.D.; Ferraiolo, G.; Rovatti, M.; Zattoni, J.; Donato, A.


    The contamination by nitrous oxide of an operating room atmosphere was studied in a number of experiments, in the absence of personnel and using a gaschromatographic method. The evacuating device of the anesthesia machine proved to be ineffective to overcome the hazard of leaks in the breathing system, whereas the air conditioning flow rates (12 outside air changes per hour) minimized waste anesthetic gas concentrations.

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

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

  10. Gas absorption experiments in a pilot plant column with the sulzer structured packing mellapack


    Brito, Marcelo Henriques de


    Data for the volumetric mass transfer coefficient, kLa, and the effective area, of structured packings have rarely been reported in the literature. This is despite the ever-increasing importance of structured packings in industrial separation columns for absorption and distillation processes. This work verified that the CO2-NaOH reaction is suitable for the determination of effective mass transfer area. The kinetic parameter of this reaction which governs the absorption flux, was evaluated wi...

  11. Gas absorption experiments in a pilot plant column with the sulzer structured packing mellapack


    Brito, Marcelo Henriques de; Stockar, Urs von


    Data for the volumetric mass transfer coefficient, kLa, and the effective area, of structured packings have rarely been reported in the literature. This is despite the ever-increasing importance of structured packings in industrial separation columns for absorption and distillation processes. This work verified that the CO2-NaOH reaction is suitable for the determination of effective mass transfer area. The kinetic parameter of this reaction which governs the absorption flux, was evaluated wi...

  12. Dynamical and Radiative Properties of X-Ray Pulsar Accretion Columns: Effects of Gas and Radiation Pressure (United States)

    West, Brent Frederick

    Previous research to investigate the dynamics of luminous X-ray pulsars and the observed spectra has largely been confined to the single-fluid model in which the higher luminosity permits the accreting flow to be regarded as a radiation-dominated ideal fluid. In this regime, the inflowing ionized gas held no special significance when investigating the dynamics of accretion column formation and the associated radiation-dominated standing shock through which the fluid must pass. This PhD research examines the dynamical importance of gas pressure in both low-luminosity and high-luminosity X-ray pulsars in which the pressure of the ionized gas may play a significant role in column formation and its associated dynamics. The "two-fluid" model is implemented by coupling radiation and gas as interacting fluids. The fluids pass through a radiation sonic point located in a shock wave where the radiation sound speed equals the bulk fluid speed. The precise location of the sonic point largely depends upon the details of the upstream boundary conditions for the incident radiation and gas sound speeds. The parameter space for the incident sound speeds is mapped and the associated temperature, pressure, and density distributions are calculated as functions of the altitude in the column. The complete dynamical problem is fully modeled by defining five fundamental free parameters, namely: (1) the polar cap size, (2) the altitude at the top of the accretion column, (3) the incident radiation Mach number, (4) the parallel scattering cross-section, and (5) the angle-averaged scattering cross-section. All of the other model parameters are derived from these fundamental free parameters. The resulting X-ray spectral formation is investigated through numerical computation based on the transport equation developed by Becker & Wolff (2007) which accounts for the bulk and thermal Comptonization inside the accreting gas. The Becker & Wolff (2007) model generally gives good agreement with the

  13. Extending the upper temperature range of gas chromatography with all-silicon microchip columns using a heater/clamp assembly. (United States)

    Ghosh, Abhijit; Johnson, Jacob E; Nuss, Johnathan G; Stark, Brittany A; Hawkins, Aaron R; Tolley, Luke T; Iverson, Brian D; Tolley, H Dennis; Lee, Milton L


    Miniaturization of gas chromatography (GC) instrumentation is of interest because it addresses current and future issues relating to compactness, portability and field application. While incremental advancements continue to be reported in GC with columns fabricated in microchips (referred to in this paper as "microchip columns"), the current performance is far from acceptable. This lower performance compared to conventional GC is due to factors such as pooling of the stationary phase in corners of non-cylindrical channels, adsorption of sensitive compounds on incompletely deactivated surfaces, shorter column lengths and less than optimum interfacing to injector and detector. In this work, a GC system utilizing microchip columns was developed that solves the latter challenge, i.e., microchip interfacing to injector and detector. A microchip compression clamp was constructed to heat the microchip (i.e., primary heater), and seal the injector and detector fused silica interface tubing to the inlet and outlet ports of the microchip channels with minimum extra-column dead volume. This clamp allowed occasional operation up to 375°C and routine operation up to 300°C. The compression clamp was constructed of a low expansion alloy, Kovar™, to minimize leaking due to thermal expansion mismatch at the interface during repeated thermal cycling, and it was tested over several months for more than one hundred injections without forming leaks. A 5.9m long microcolumn with rectangular cross section of 158μm×80μm, which approximately matches a 100μm i.d. cylindrical fused silica column, was fabricated in a silicon wafer using deep reactive ion etching (DRIE) and high temperature fusion bonding; finally, the channel was coated statically with a 1% vinyl, 5% phenyl, 94% methylpolysiloxane stationary phase. High temperature separations of C10-C40 n-alkanes and a commercial diesel sample were demonstrated using the system under both temperature programmed GC (TPGC) and thermal

  14. Gas chromatographic-mass spectrometric determination of aromatic hydrocarbon metabolites from livers of fish exposed to fuel oil. (United States)

    Krahn, M M; Malins, D C


    Metabolites of several two- and three-ring aromatic hydrocarbons (AHs) have been found in livers of English sole exposed to No. 2 fuel oil. Four metabolites of the C2H5-naphthalenes, six of the C3H7-naphthalenes and one each of fluorene, phenanthrene and anthracene have been partially characterized and their concentrations, which ranged from 50 to 1100 ng/g, were determined. Metabolites were separated from the liver matrix using an automated extractor/concentrator. The resulting extract was then purified by high-performance liquid chromatography, and the metabolites were characterized and quantitated by gas chromatography-mass spectrometry.

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

    Laakso, Päivi H


    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.

  16. 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. (United States)

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


    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.

  17. Radiolytic degradation of TBP-HNO3 system: gas chromatographic determination of radiation chemical yields of n-butanol and nitrobutane

    International Nuclear Information System (INIS)

    Krishnamurthy, M.V.; Sipahimalani, A.T.


    Radiolytic degradation of the TBP-HNO 3 system has been studied for the radiation dose range of 19.8 to 262 kGy by the gas chromatographic method. n-Butanol and nitrobutane formed due to irradiation have been identified and estimated in pure TBP, TBP-3M HNO 3 extract and TBP-5M HNO 3 extract. The G-values (radiation chemical yields) of n-butanol are determined to be 0.28, 0.77 and 0.47 for a pure TBP, TBP-3M HNO 3 extract and TBP-5M HNO 3 extract, respectively. The G-values of nitrobutane (1-nitrobutane) are 0.55 and 1.09 for TBP-3M HNO 3 extract and TBP-5M HNO 3 extract. It is found that G(n-butanol) is less for TBP-5M HNO 3 extract than for TBP-3M HNO 3 extract, while G(nitrobutane) is grater for TBP-5M HNO 3 extract than for TBP-3M HNO 3 extract. This is explained on the basis of the formation of TBP.HNO 3 species and the role played by nitric acid in the TBP phase. (author) 12 refs.; 2 figs

  18. Detection of clenbuterol at trace levels in doping analysis using different gas chromatographic-mass spectrometric techniques. (United States)

    Yang, Sheng; Liu, Xin; Xing, Yanyi; Zhang, Dapeng; Wang, Shan; Wang, Xiaobing; Xu, Youxuan; Wu, Moutian; He, Zhenwen; Zhao, Jian


    This study demonstrates the development of a gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS-MS) assay to detect clenbuterol in human urine and the comparison of this method with GC-MS techniques and gas chromatography-high resolution mass spectrometry (GC-HRMS) techniques. Urine samples were hydrolyzed with β-glucuronidase, extracted with methyl tert-butyl ether and dried under nitrogen. The derivative reagent was N-methyl-N-(trimethylsilyl)-trifluoroacetamide with NH4I and was analyzed by GC-MS, GC-MS-MS and GC-HRMS. A validation study was conducted by GC-MS-MS. The analyses of clenbuterol using different mass spectrometric techniques were compared. The limit of detection (LOD) for clenbuterol in human urine was 2 ng/mL by GC-MS (selected ion monitoring mode: SIM mode), 0.06 ng/mL by GC-HRMS and 0.03 ng/mL by GC-MS-MS, respectively, while the LOD by GC-HRMS was 0.06. With GC-MS-MS, the intra-assay and inter-assay precisions were less than 15%, the recoveries were 86 to 112% and the linear range was 0.06 to 8.0 ng/mL. The GC-MS under SIM mode can be used as a screening tool to detect clenbuterol at trace levels in human urine. The GC-MS-MS and GC-HRMS methods can confirm clenbuterol when its concentration is below 2 ng/mL. The results demonstrate that the GC-MS-MS method is quite sensitive, specific and reliable for the detection of clenbuterol in doping analysis.

  19. A Compact Trace Gas Lidar for Simultaneous Measurements of Methane and Water Vapor Column Abundance (United States)

    National Aeronautics and Space Administration — Methane is the second most important anthropogenic greenhouse gas. Understanding current global methane trends is a difficult challenge that cannot be resolved by...

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

    Directory of Open Access Journals (Sweden)

    H. A. J. Meijer


    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.

  1. Comparison of Dairy Manure Anaerobic Digestion Performance in Gas-lift and Bubble Column Digesters


    Tang, Jing


    Anaerobic digestion is one of the most promising management options for dairy manure treatment. Manure wastewater from dairy farms has been used for methane production for decades. However, performance failure due to inadequate mixing is routine. In general, the mixng of anaerobic digester is achived throguh mechnical stirring, liquid circulation, and gas circulation, among which the gas circulation proves to be the most effcient way. In this work, we studied the liquid flow pattern of tw...

  2. Effects of chromatographic fractions of Euphorbia hirta on the rat ...

    African Journals Online (AJOL)

    The ethanolic extract of this plant was subjected to chromatographic separation using the vacuum liquid chromatographic technique, a modified form of classical column chromatography. With the aid of thin layer chromatography, six fractions of this plant were obtained and were administered to rats in graded doses of ...

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

    Directory of Open Access Journals (Sweden)

    Behrouz Akbari-adergani


    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.

  4. Antioxidant Activity and Gas Chromatographic-Mass Spectrometric Analysis of Extracts of the Marine Algae, Caulerpa peltata and Padina Gymnospora. (United States)

    Murugan, Kavitha; Iyer, Vidhya V


    The results of our previous investigations on extracts of selected marine algae showed that Caulerpa peltata and Padina gymnospora had more promising antiproliferative and antioxidant activities than Gelidiella acerosa and Sargassum wightii. Based on these results, the more active chloroform extract of C. peltata and ethyl acetate extract of P. gymnospora were further analyzed for their constituents by using gas chromatography in tandem with mass spectrometry. The GC-MS analysis (GC % peak area given in parentheses) showed that fucosterol (12.45%) and L-(+)-ascorbic acid 2, 6-dihexadecanoate (8.13%) were the major compounds present in P. gymnospora ethyl acetate extract. On the other hand, C. peltata chloroform extract had 1-heptacosanol (10.52%), hexacosanol acetate (9.28%), tetradecyl ester of chloroacetic acid (7.22%), Z,Z-6, 28-heptatriactontadien-2-one (6.77%) and 10, 13-dimethyl-methyl ester of tetradecanoic acid (5.34%) as major compounds. Also described in the report are the beta-carotene bleaching inhibitory and total reducing activities of the chloroform and ethyl acetate extracts of C. peltata and P. gymnospora, respectively, relative to the other three extracts (aqueous, methanol, chloroform or ethyl acetate) of the two algae.

  5. Solid-phase microextraction for gas chromatographic/mass spectrometric analysis of dimethoate in human biological samples. (United States)

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


    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.

  6. Characterization of odorous contaminants in post-consumer plastic packaging waste using multidimensional gas chromatographic separation coupled with olfactometric resolution. (United States)

    Strangl, Miriam; Fell, Tanja; Schlummer, Martin; Maeurer, Andreas; Buettner, Andrea


    The increasing world population with their growing consumption of goods escalates the issue of sustainability concepts with increasing demands in recycling technologies. Recovery of post-consumer packaging waste is a major topic in this respect. However, contamination with odorous constituents currently curtails the production of recycling products that meet the high expectations of both consumers and industry. To guarantee odor-free recyclates, the main prerequisite is to characterize the molecular composition of the causative odorants in post-consumer plastic packaging waste. However, targeted characterization of odorous trace contaminants among an abundance of volatiles is a major challenge and requires specialized and high-resolution analytical approaches. For this aim, post-consumer packaging waste was characterized by sensory analysis and two-dimensional high resolution gas chromatography coupled with mass spectrometry and olfactometry. The 33 identified odorants represent various structural classes as well as a great diversity of smell impressions with some of the compounds being identified in plastics for the first time. Substances unraveled within this study provide insights into sources of odorous contamination that will require specific attention in the future in terms of screening and prevention in recycling products. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Comprehensive two-dimensional gas chromatographic profiling and chemometric interpretation of the volatile profiles of sweat in knit fabrics. (United States)

    de la Mata, A Paulina; McQueen, Rachel H; Nam, Seo Lin; Harynuk, James J


    Human axillary sweat is a poorly explored biofluid within the context of metabolomics when compared to other fluids such as blood and urine. In this paper, we explore the volatile organic compounds emitted from two different types of fabric samples (cotton and polyester) which had been worn repeatedly during exercise by participants. Headspace solid-phase microextraction (SPME) and comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) were employed to profile the (semi)volatile compounds on the fabric. Principal component analysis models were applied to the data to aid in visualizing differences between types of fabrics, wash treatment, and the gender of the subject who had worn the fabric. Statistical tools included with commercial chromatography software (ChromaTOF) and a simple Fisher ratio threshold-based feature selection for model optimization are compared with a custom-written algorithm that uses cluster resolution as an objective function to maximize in a hybrid backward-elimination forward-selection approach for optimizing the chemometric models in an effort to identify some compounds that correlate to differences between fabric types. The custom algorithm is shown to generate better models than the simple Fisher ratio approach. Graphical Abstract A route from samples and questions to data and then answers.

  8. Fluid dynamics of packed columns principles of the fluid dynamic design of columns for gas/liquid and liquid/liquid systems

    CERN Document Server

    Mackowiak, Jerzy


    This book describes the basic design principles of columns equipped with modern lattice packings and structured packed beds, as generally used in industry. It provides support to engineers as well as graduate students in their daily design work.

  9. Development and single-laboratory validation of a new gas chromatographic multi-pesticide method of analysis of commercial emulsifiable concentrate formulations containing alachlor, chlorpyrifos methyl, fenthion and trifluralin as active ingredients. (United States)

    Karasali, Helen; Balayannis, George; Hourdakis, Adamantia; Ambrus, Arpad


    A multi-pesticide (MP) method was developed and single-laboratory validated for the quality control of commercial pesticide products containing alachlor, chlorpyrifos methyl, fenthion and trifluralin as active ingredients (a.i.). A capillary gas chromatographic system with flame ionization detection (FID) and a programmable temperature vaporising split injector was used. The performance characteristics (specificity, linearity, precision and repeatability) of the method satisfied international acceptability criteria.

  10. Study on atmospheric hydrogen enrichment by cryopump method and isotope separation by gas chromatography

    International Nuclear Information System (INIS)

    Taniyama, Yuki; Momoshima, Noriyuki


    To obtain the information of source of atmospheric hydrogen tritium an analysis of tritium isotopes is thought to be effective. So an atmospheric hydrogen enrichment apparatus and a cryogenic gas chromatographic column were made. Experiments were carried out to study the performance of cryopump to enrich atmospheric hydrogen and the column to separate hydrogen isotopes that obtained by cryopump method. The cryopump was able to process about 1000 1 atmosphere and the column was able to separate hydrogen isotopes with good resolution. (author)

  11. Development of a gas-liquid chromatographic method for the analysis of fatty acid tryptamides in cocoa products. (United States)

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


    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.

  12. An analytical method for trifluoroacetic Acid in water and air samples using headspace gas chromatographic determination of the methyl ester. (United States)

    Zehavi, D; Seiber, J N


    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.

  13. Gas-liquid mass transfer coefficient of methane in bubble column reactor

    International Nuclear Information System (INIS)

    Lee, Jaewon; Ha, Kyoung-Su; Lee, Jinwon; Kim, Choongik; Yasin, Muhammad; Park, Shinyoung; Chang, In Seop; Lee, Eun Yeol


    Biological conversion of methane gas has been attracting considerable recent interest. However, methanotropic bioreactor is limited by low solubility of methane gas in aqueous solution. Although a large mass transfer coefficient of methane in water could possibly overcome this limitation, no dissolved methane probe in aqueous environment is commercially available. We have developed a reactor enabling the measurement of aqueous phase methane concentration and mass transfer coefficient (k L a). The feasibility of the new reactor was demonstrated by measuring k L a values as a function of spinning rate of impeller and flow rate of methane gas. Especially, at spinning rate of 300 rpm and flow rate of 3.0 L/min, a large k L a value of 102.9 h -1 was obtained

  14. Evaluation and application of static headspace-multicapillary column-gas chromatography-ion mobility spectrometry for complex sample analysis. (United States)

    Denawaka, Chamila J; Fowlis, Ian A; Dean, John R


    An evaluation of static headspace-multicapillary column-gas chromatography-ion mobility spectrometry (SHS-MCC-GC-IMS) has been undertaken to assess its applicability for the determination of 32 volatile compounds (VCs). The key experimental variables of sample incubation time and temperature have been evaluated alongside the MCC-GC variables of column polarity, syringe temperature, injection temperature, injection volume, column temperature and carrier gas flow rate coupled with the IMS variables of temperature and drift gas flow rate. This evaluation resulted in six sets of experimental variables being required to separate the 32 VCs. The optimum experimental variables for SHS-MCC-GC-IMS, the retention time and drift time operating parameters were determined; to normalise the operating parameters, the relative drift time and normalised reduced ion mobility for each VC were determined. In addition, a full theoretical explanation is provided on the formation of the monomer, dimer and trimer of a VC. The optimum operating condition for each VC calibration data was obtained alongside limit of detection (LOD) and limit of quantitation (LOQ) values. Typical detection limits ranged from 0.1ng bis(methylthio)methane, ethylbutanoate and (E)-2-nonenal to 472ng isovaleric acid with correlation coefficient (R(2)) data ranging from 0.9793 (for the dimer of octanal) through to 0.9990 (for isobutyric acid). Finally, the developed protocols were applied to the analysis of malodour in sock samples. Initial work involved spiking an inert matrix and sock samples with appropriate concentrations of eight VCs. The average recovery from the inert matrix was 101±18% (n=8), while recoveries from the sock samples were lower, that is, 54±30% (n=8) for sock type 1 and 78±24% (n=6) for sock type 2. Finally, SHS-MCC-GC-IMS was applied to sock malodour in a field trial based on 11 volunteers (mixed gender) over a 3-week period. By applying the SHS-MCC-GC-IMS database, four VCs were

  15. A Miniaturized Laser Heterodyne Radiometer for Greenhouse Gas Measurements in the Atmospheric Column (United States)

    Steel, Emily Wilson


    Laser Heterodyne Radiometry is a technique adapted from radio receiver technology has been used to measure trace gases in the atmosphere since the 1960s.By leveraging advances in the telecommunications industry, it has been possible to miniaturize this technology.The mini-LHR (Miniaturized Laser Heterodyne Radiometer) has been under development at NASA Goddard Space flight Center since 2009. This sun-viewing instrument measures carbon dioxide and methane in the atmospheric column and operates in tandem with an AERONET sun photometer producing a simultaneous measure of aerosols. The mini-LHR has been extensively field tested in a range of locations ranging in the continental US as well as Alaska and Hawaii and now operates autonomously with sensitivities of approximately 0.2 ppmv and approximately10 ppbv, for carbon dioxide and methane respectively, for 10 averaged scans under clear sky conditions.

  16. Antidiarrhoeal Activity of Chromatographic Fractions of ...

    African Journals Online (AJOL)


    Purpose: The present study was undertaken in order to evaluate the antidiarrhoeal activity of three chromatographic fractions (L, S and Y) of Stereospermum kunthianum stem bark in mice. Methods: Vacuum liquid/column chromatography (VLC/ CC) were used to obtain three fractions (L,S and Y) of Stereospermum ...

  17. Liquid chromatographic determination of pyrethroid insecticide ...

    African Journals Online (AJOL)

    A new high performance liquid chromatography (HPLC) method for the quantitative analysis of cypermethrin in vegetable samples has been described. The determination of cypermethrin was carried out on Kromosil C18 analytical column (250 mm × 4.6 mm I.D., 5 μm particle size), under reversed phase chromatographic ...

  18. Liquid chromatographic analysis of phenobarbitone, ethosuximide ...

    African Journals Online (AJOL)

    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 ...

  19. Improved Thermal Modulator for Gas Chromatography (United States)

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


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

  20. A water column study of methane around gas flares located at the West Spitsbergen continental margin

    DEFF Research Database (Denmark)

    Gentz, Torben; Damm, Ellen; von Deimling, Jens Schneider


    L1. Our results suggest that the methane dissolved from gas bubbles is efficiently trapped below the pycnocline and thus limits the methane concentration in surface water and the air–sea exchange during summer stratification. During winter the lateral stratification breaks down and fractions...

  1. Green Ocean Amazon (GoAmazon) 2014/15. Semi-Volatile Thermal Desorption Aerosol Gas Chromatograph (SVTAG) Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Goldstein, A. H. [Univ. of California, Berkeley, CA (United States); Yee, L. D. [Univ. of California, Berkeley, CA (United States); Issacman-VanWertz, G. [Univ. of California, Berkeley, CA (United States); Wernis, R. A. [Univ. of California, Berkeley, CA (United States)


    In areas where biogenic emissions are oxidized in the presence of anthropogenic pollutants such as SO2, NOx, and black carbon, it has become increasingly apparent that secondary organic aerosol (SOA) formation from biogenic volatile organic compounds (VOCs) is substantially enhanced. Research is urgently needed to elucidate fundamental processes of natural and anthropogenically influenced VOC oxidation and the contribution of these processes to SOA formation. GoAmazon 2014/15 afforded study of the chemical transformations in the region downwind of Manaus, Brazil, where local biogenic VOC emissions are high, and their chemical oxidation can be studied both inside and outside of the urban plume to differentiate the role of anthropogenic influence on secondary aerosol formation during oxidation of these natural VOC emissions. To understand the connection between primary biogenic VOC emissions and their secondary products that form aerosols, we made time-resolved molecular level measurements by deploying a Semi-Volatile Thermal Desorption Aerosol Gas Chromatograph (SV-TAG) and a sequential filter sampler during two intensive operational periods (IOPs) of the GoAmazon 2014/15 field campaign. The SV-TAG measured semi-volatile organic compounds in both the gas and particle phases and the sequential filter sampler collected aerosols on quartz fiber filters in four-hour increments used for offline analysis. SV-TAG employed novel online derivatization that provided chemical speciation of highly oxygenated or functionalized compounds that comprise a substantial fraction of secondary organic aerosols, yet are poorly characterized. It also provided partitioning of these compounds between the vapor and particle phases at sufficient time resolution to define the importance of competing atmospheric processes. These measurements were supported by offline analysis of the filters using two-dimensional gas chromatography (GC x GC) with high-resolution time-of-flight mass spectrometry

  2. Simultaneous determination of metoprolol and metabolites in urine by capillary column gas chromatography as oxazolidineone and trimethylsilyl derivatives. (United States)

    Gyllenhaal, O; Hoffmann, K J


    A method for the determination of metoprolol and its main metabolites in urine is presented. The method comprises derivatization of the aminopropanol side-chain with phosgene at alkaline pH and isolation in an organic phase at acidic pH. After trimethylsilylation, separation and quantification are performed by capillary column gas chromatography with flame ionization detection. The reaction is performed at pH 12 with 60 microliters of 2 M phosgene in toluene added in three portions. Diethyl ether--dichloromethane is used as extraction medium and bis(trimethylsilyl) acetamide as silylating agent. With spiked samples linear standard curves were obtained for metoprolol and three of its main metabolites with a detection limit varying between 4 and 20 mumol/l of urine. The method was applied to urine samples from a normal individual who had taken 292 mumol of metoprolol as tartrate.

  3. Determination of Odor Release in Hydrocolloid Model Systems Containing Original or Carboxylated Cellulose at Different pH Values Using Static Headspace Gas Chromatographic (SHS-GC Analysis

    Directory of Open Access Journals (Sweden)

    Pahn-Shick Chang


    Full Text Available Static headspace gas chromatographic (SHS-GC analysis was performed to determine the release of 13 odorants in hydrocolloid model systems containing original or regio-selectively carboxylated cellulose at different pH values. The release of most odor compounds was decreased in the hydrocolloid solutions compared to control, with the amounts of 2-propanol, 3-methyl-1-butanol, and 2,3-butanedione released into the headspace being less than those of any other odor compound in the hydrocolloid model systems. However, there was no considerable difference between original cellulose-containing and carboxylated-cellulose containing systems in the release of most compounds, except for relatively long-chain esters such as ethyl caprylate and ethyl nonanoate. The release from the original and carboxylated cellulose solutions controlled to pH 10 was significantly higher than that from solutions adjusted to pH 4 and 7 in the case of some esters (ethyl acetate, methyl propionate, ethyl propionate, ethyl butyrate, butyl propionate, ethyl caproate and alcohols (2-propanol, 3-methyl-1-butanol, in particular, ethyl butyrate and 3-methyl-1-butanol. In contrast, the release of 2,3-butanedione from both the original and carboxylated cellulose solutions was increased at pH 4 and 7 compared to that at pH 10 by about 70% and 130%, respectively. Our study demonstrated that the release of some odorants could be changed significantly by addition of both original and carboxylated cellulose in hydrocolloid model systems, but only minor effect was observed in pH of the solution.

  4. The gas chromatographic determination of volatile fatty acids in wastewater samples: evaluation of experimental biases in direct injection method against thermal desorption method. (United States)

    Ullah, Md Ahsan; Kim, Ki-Hyun; Szulejko, Jan E; Cho, Jinwoo


    The production of short-chained volatile fatty acids (VFAs) by the anaerobic bacterial digestion of sewage (wastewater) affords an excellent opportunity to alternative greener viable bio-energy fuels (i.e., microbial fuel cell). VFAs in wastewater (sewage) samples are commonly quantified through direct injection (DI) into a gas chromatograph with a flame ionization detector (GC-FID). In this study, the reliability of VFA analysis by the DI-GC method has been examined against a thermal desorption (TD-GC) method. The results indicate that the VFA concentrations determined from an aliquot from each wastewater sample by the DI-GC method were generally underestimated, e.g., reductions of 7% (acetic acid) to 93.4% (hexanoic acid) relative to the TD-GC method. The observed differences between the two methods suggest the possibly important role of the matrix effect to give rise to the negative biases in DI-GC analysis. To further explore this possibility, an ancillary experiment was performed to examine bias patterns of three DI-GC approaches. For instance, the results of the standard addition (SA) method confirm the definite role of matrix effect when analyzing wastewater samples by DI-GC. More importantly, their biases tend to increase systematically with increasing molecular weight and decreasing VFA concentrations. As such, the use of DI-GC method, if applied for the analysis of samples with a complicated matrix, needs a thorough validation to improve the reliability in data acquisition. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Microfluidic Columns with Nanotechnology-Enabled Stationary Phases for Gas Chromatography


    Shakeel, Hamza


    Advances in micro-electro-mechanical-systems (MEMS) along with nanotechnology based methods have enabled the miniaturization of analytical chemistry instrumentation. The broader aim is to provide a portable, low-cost, and low-power platform for the real-time detection and identification of organic compounds in a wide variety of applications. A benchtop gas chromatography (GC) system is considered a gold standard for chemical analysis by analytical chemists. Similarly, miniaturization of key G...

  6. Assembly for connecting the column ends of two capillary columns

    International Nuclear Information System (INIS)

    Kolb, B.; Auer, M.; Pospisil, P.


    In gas chromatography, the column ends of two capillary columns are inserted into a straight capillary from both sides forming annular gaps. The capillary is located in a tee out of which the capillary columns are sealingly guided, and to which carrier gas is supplied by means of a flushing flow conduit. A ''straight-forward operation'' having capillary columns connected in series and a ''flush-back operation'' are possible. The dead volume between the capillary columns can be kept small

  7. Removal of elemental mercury from flue gas by thermally activated ammonium persulfate in a bubble column reactor. (United States)

    Liu, Yangxian; Wang, Qian


    In this article, a novel technique on removal of elemental mercury (Hg(0)) from flue gas by thermally activated ammonium persulfate ((NH4)(2)S(2)O(8)) has been developed for the first time. Some experiments were carried out in a bubble column reactor to evaluate the effects of process parameters on Hg(0) removal. The mechanism and kinetics of Hg(0) removal are also studied. The results show that the parameters, (NH4)(2)S(2)O(8) concentration, activation temperature and solution pH, have significant impacts on Hg(0) removal. The parameters, Hg(0), SO2 and NO concentration, only have small effects on Hg(0) removal. Hg(0) is removed by oxidations of (NH4)(2)S(2)O(8), sulfate and hydroxyl free radicals. When (NH4)(2)S(2)O(8) concentration is more than 0.1 mol/L and solution pH is lower than 9.71, Hg(0) removal by thermally activated (NH4)(2)S(2)O(8) meets a pseudo-first-order fast reaction with respect to Hg(0). However, when (NH4)(2)S(2)O(8) concentration is less than 0.1 mol/L or solution pH is higher than 9.71, the removal process meets a moderate speed reaction with respect to Hg(0). The above results indicate that this technique is a feasible method for emission control of Hg(0) from flue gas.

  8. 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. (United States)

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


    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.

  9. Supercritical Fluid Chromatographic Separation of Dimethylpolysiloxane Polymer

    Energy Technology Data Exchange (ETDEWEB)

    Pyo, Dong Jin; Lim, Chang Hyun [Kangwon National University, Chuncheon (Korea, Republic of)


    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.

  10. Joint approximate diagonalization of eigenmatrices as a high-throughput approach for analysis of hyphenated and comprehensive two-dimensional gas chromatographic data. (United States)

    Zarghani, Maryam; Parastar, Hadi


    The objective of the present work is development of joint approximate diagonalization of eigenmatrices (JADE) as a member of independent component analysis (ICA) family, for the analysis of gas chromatography-mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) data to address incomplete separation problem occurred during the analysis of complex sample matrices. In this regard, simulated GC-MS and GC×GC-MS data sets with different number of components, different degree of overlap and noise were evaluated. In the case of simultaneous analysis of multiple samples, column-wise augmentation for GC-MS and column-wise super-augmentation for GC×GC-MS was used before JADE analysis. The performance of JADE was evaluated in terms of statistical parameters of lack of fit (LOF), mutual information (MI) and Amari index as well as analytical figures of merit (AFOMs) obtained from calibration curves. In addition, the area of feasible solutions (AFSs) was calculated by two different approaches of MCR-BANDs and polygon inflation algorithm (FACPACK). Furthermore, JADE performance was compared with multivariate curve resolution-alternating least squares (MCR-ALS) and other ICA algorithms of mean-field ICA (MFICA) and mutual information least dependent component analysis (MILCA). In all cases, JADE could successfully resolve the elution and spectral profiles in GC-MS and GC×GC-MS data with acceptable statistical and calibration parameters and their solutions were in AFSs. To check the applicability of JADE in real cases, JADE was used for resolution and quantification of phenanthrene and anthracene in aromatic fraction of heavy fuel oil (HFO) analyzed by GC×GC-MS. Surprisingly, pure elution and spectral profiles of target compounds were properly resolved in the presence of baseline and interferences using JADE. Once more, the performance of JADE was compared with MCR-ALS in real case. On this matter, the mutual information

  11. Influence of gas conditions on electron temperature inside a pinch column of plasma-focus discharge (United States)

    Zaloga, D. R.; Sadowski, M. J.; Skladnik-Sadowska, E.; Paduch, M.; Zielinska, E.; Tomaszewski, K.


    The paper reports on soft x-ray emission from high-current discharges in PF-1000U facility operated at 170 kJ. The discharges at static conditions were performed with pure deuterium (D2) and a mixture of D2 and neon (Ne). In shots with the gas-puffing 1 cm3 of D2 or a (D2+Ne) mixture was injected 2 ms before the discharge initiation. Time-integrated x-ray images from a Be-filtered pinhole camera showed that the pinch microstructure depends strongly on gas conditions. In shots with the D2-, (D2+Ne)- or He-puffing distinct “filaments” and “hot-spots” were observed. Time-resolved x-ray pulses were recorded with 4 filtered PIN-diodes which recorded signals from 2 regions of 3 cm in diameter (at z = 3 cm and 6 cm from the anode). From a ratio of x-ray pulses, measured behind different filters, it was estimated that at the static D2-filling electron temperatures (Te ) were from 90 eV to 200 eV. At the D2-filling and -puffing additional x-ray spikes were emitted from “hot-spots” with Te twice higher. In shots at the (D2+10%Ne)-filling Te was 4 keV. In shots with the (D2+Ne)-mixture puffing intense “hot-spots” were formed, and Te reached 2.2-7.5 keV. At the same conditions “filaments” were reproducible macroscopically, but “hot-spots” were irreproducible.

  12. CFD-PBM Approach with Different Inlet Locations for the Gas-Liquid Flow in a Laboratory-Scale Bubble Column with Activated Sludge/Water

    Directory of Open Access Journals (Sweden)

    Le Wang


    Full Text Available A novel computational fluid dynamics-population balance model (CFD-PBM for the simulation of gas mixing in activated sludge (i.e., an opaque non-Newtonian liquid in a bubble column is developed and described to solve the problem of measuring the hydrodynamic behavior of opaque non-Newtonian liquid-gas two-phase flow. We study the effects of the inlet position and liquid-phase properties (water/activated sludge on various characteristics, such as liquid flow field, gas hold-up, liquid dynamic viscosity, and volume-averaged bubble diameter. As the inlet position changed, two symmetric vortices gradually became a single main vortex in the flow field in the bubble column. In the simulations, when water was in the liquid phase, the global gas hold-up was higher than when activated sludge was in the liquid phase in the bubble column, and a flow field that was dynamic with time was observed in the bubble column. Additionally, when activated sludge was used as the liquid phase, no periodic velocity changes were found. When the inlet position was varied, the non-Newtonian liquid phase had different peak values and distributions of (dynamic liquid viscosity in the bubble column, which were related to the gas hold-up. The high gas hold-up zone corresponded to the low dynamic viscosity zone. Finally, when activated sludge was in the liquid phase, the volume-averaged bubble diameter was much larger than when water was in the liquid phase.


    NARCIS (Netherlands)



    The application of Bond-Elut Certify solid-phase extraction columns to the systematic toxicological analysis of whole blood was evaluated. The reproducibility of the extraction was tested with thirteen drugs varying in physico-chemical properties. Analysis was performed with capillary gas


    NARCIS (Netherlands)


    The main problems with complete analysis of the components of fuel methanol, or in Fischer-Tropsch studies, are the several classes of compound present in the sample (permanent gases, water, alcohols, hydrocarbons), its wide range of components, its boiling point range, and the wide range of

  15. [Determination of pesticide residues in fugu, eel and prawn using gas chromatography-mass spectrometry with gel permeation chromatographic clean-up]. (United States)

    Zheng, Feng; Pang, Guofang; Li, Yan; Wang, Minglin; Fan, Chunlin


    A multiresidue analytical method was developed for the determination of 191 pesticides in fugu, eel and prawn using gas chromatography-mass spectrometry (GC-MS). The samples were extracted with ethyl acetate and cyclohexane (1:1, v/v), and cleaned-up by gel permeation chromatography (GPC). The GPC eluant collected from 26 min to 44 min was concentrated to 1 mL, then analyzed using GC-MS. A DB-1701 column was used for the separation. The MS detection was performed in selected ion monitoring mode. The recoveries were determined at the two spiked levels of I LOQ and 4 LOQ (LOQ: limit of quantification). The overall recoveries were from 50.2% to 120%, and in which the recoveries of 89.5% pesticides were from 70% to 120%. The relative standard deviations (RSDs) of the recoveries were from 0.6% to 21.6%. The calibration curves of all pesticides showed good linearities in the respective ranges with the correlation coefficient above 0.97. The limits of detection and the limits of quantification were 0.002-0.3 mg/kg and 0.007-1.2 mg/kg, respectively. The sensitivity and accuracy of the method met the requirements of the multiple pesticide residues. This method was applicable to determine 191 multiple pesticide residues in fugu, eel, prawn and other fishes.

  16. Quantification of Delta9-tetrahydrocannabinol and its major metabolites in meconium by gas chromatographic-mass spectrometric assay: assay validation and preliminary results of the "meconium project". (United States)

    Marchei, Emilia; Pellegrini, Manuela; Pacifici, Roberta; Palmi, Ilaria; Lozano, Jaime; García-Algar, Oscar; Pichini, Simona


    A rapid and simple procedure based on gas chromatography-mass spectrometry (GC-MS) is described for determination of Delta-tetrahydrocannabinol (THC), 11-hydroxy-Delta-tetrahydrocannabinol (THC-OH) and 11-nor-Delta-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) in meconium using Delta-tetrahydrocannabinol (Delta-THC) and deuterated THC-COOH as internal standards. The biological matrix was subjected to liquid-liquid extraction after enzyme hydrolysis for conjugated analytes.Chromatography was performed on a fused silica capillary column and analytes were determined in the selected-ion-monitoring (SIM) mode. The method was validated in the range 20 to 500 microg/g using 1g of meconium per assay. The method was applied to the analysis of meconium in a cohort of newborns to assess eventual fetal exposure to cannabis. Within positive samples, THC-COOH and THC-OH (range: 33.7 to 182.1 and 20.7 to 493.3 microg/g, respectively) were both present in the majority of cases with only 1 specimen with THC-OH as the most abundant metabolite and 2 with THC only.

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

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


    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

  18. 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. (United States)

    Jalbert, J; Gilbert, R; Tétreault, P


    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

  19. Chromatographic Separation of Vitamin E Enantiomers

    Directory of Open Access Journals (Sweden)

    Ju-Yen Fu


    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.

  20. Ion chromatographic determination of Di-n-butyl phosphate in degraded organic solvent

    International Nuclear Information System (INIS)

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


    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)

  1. 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

    Energy Technology Data Exchange (ETDEWEB)

    Perez, M.; Gonzalez, D.


    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.

  2. Chelate-modified polymers for atmospheric gas chromatography (United States)

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


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

  3. On-line sample enrichment-capillary gas chromatography of aqueous samples using geometrically deformed open-tubular extraction columns.

    NARCIS (Netherlands)

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


    The effect of geometrical deformation of open‐tubular extraction columns on peak dispersion of retained solutes is evaluated. By coiling or stitching of the columns peak dispersion is decreased, with a factor of two and more than five, respectively, due to secondary flow enhanced radial dispersion.

  4. Optimization of gas chromatography using short glass capillary column with mass spectrometry for identification and evaluation of commercial heavy alkylbenzene structures. (United States)

    Ghoreishi, S M; Beiggy, M; Mazloum Ardekani, M


    Heavy alkylbenzene (HAB) is one of the by-products when producing linear alkylbenzene (LAB). Identification of the fine structures of HAB is difficult because of its complex structure and high boiling point. The gas chromatography/mass spectrometry (GC/MS) technique with a short glass capillary column is the best method applicable to analysis of high-boiling and thermally labile compounds. The column efficiency is evaluated on the basis of Van Deemter curves. The experimental results show that the reduction in the optimum column efficiency for a short glass capillary column occurs along with a reduction in effective theoretical plates. A second important result is that the shift in the value of the flow velocity is related to the optimum point in height equivalent theoretical plate (HETP). The flow velocity is higher than that of conventional gas chromatography(GC). The optimized conditions were used to analyse HAB produced through the hydrogen fluoride (HF) alkylation process. The results show acceptable relative separation of a product in an extended boiling point range. The optimized conditions were also used to analyse three other special samples supplied by BASF company's AlCl(3 )alkylation process and to approve the previous structures. The results also show that HAB from Iran Chemical Industries Investment Company (ICIIC) produced through LAB complex consists of an additional part and has more linearity than the other three samples of HAB obtained from BASF.

  5. Conventional and enantioselective gas chromatography with microfabricated planar columns for analysis of real-world samples of plant volatile fraction. (United States)

    Cagliero, C; Galli, S; Galli, M; Elmi, I; Belluce, M; Zampolli, S; Sgorbini, B; Rubiolo, P; Bicchi, C


    Within a project exploring the application of lab-on-chip GC to in-field analysis of the plant volatile fraction, this study evaluated the performance of a set of planar columns (also known as microchannels, MEMS columns, or microfabricated columns) of different dimensions installed in a conventional GC unit. Circular double-spiral-shaped-channel planar columns with different square/rectangular sections up to 2m long were applied to the analysis of both essential oils and headspace samples of a group of medicinal and aromatic plants (chamomile, peppermint, sage, rosemary, lavender and bergamot) and of standard mixtures of related compounds; the results were compared to those obtained with reference narrow-bore columns (l:5m, dc:0.1mm, df:0.1 μm). The above essential oils and headspaces were first analyzed quali-and quantitatively with planar columns statically coated with conventional stationary phases (5%-phenyl-polymethylsiloxane and auto-bondable nitroterephthalic-acid-modified polyethylene glycol), and then submitted to chiral recognition of their diagnostic markers, by enantioselective GC with a planar columns coated with a cyclodextrin derivative (30% 6(I-VII)-O-TBDMS-3(I-VII)-O-ethyl-2(I-VII)-O-ethyl-β-cyclodextrin in PS-086). Column characteristics and analysis conditions were first optimized to obtain suitable retention and efficiency for the samples investigated. The planar columns tested showed performances close to the reference conventional narrow-bore columns, with theoretical plate numbers per meter (N/m) ranging from 6100 to 7200 for those coated with the conventional stationary phases, and above 5600 for those with the chiral selector. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Evolved gas composition monitoring by repetitive injection gas chromatography. (United States)

    White, Robert L


    Performance characteristics and applications of a small volume gas chromatograph oven are described. Heating and cooling properties of the apparatus are evaluated and examples are given illustrating the advantages of greatly reducing the air bath volume surrounding fused silica columns. Fast heating and cooling of the oven permit it to be employed for repetitive injection analyses. By using fast gas chromatography separations to achieve short assay cycle times, the apparatus can be employed for on-line species-specific gas stream composition monitoring when volatile species concentrations vary on time scales of a few minutes or longer. This capability facilitates repeated sampling and fast gas chromatographic separations of volatile product mixtures produced during thermal analyses. Applications of repetitive injection gas chromatography-mass spectrometry evolved gas analyses to monitoring purge gas effluent streams containing volatile acid catalyzed polymer cracking products are described. The influence of thermal analysis and chromatographic experimental parameters on effluent sampling frequency are delineated. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Gas chromatographic determination and mechanism of formation of D-amino acids occurring in fermented and roasted cocoa beans, cocoa powder, chocolate and cocoa shell. (United States)

    Pätzold, R; Brückner, H


    Fermented cocoa beans of various countries of origin (Ivory Coast, Ghana, Sulawesi), cocoa beans roasted under defined conditions (100-150 degrees C; 30-120 min), low and high fat cocoa powder, various brands of chocolate, and cocoa shells were analyzed for their contents of free L-and D-amino acids. Amino acids were isolated from defatted products using a cation exchanger and converted into volatile N(O)-pentafluoropropionyl amino acid 2-propyl esters which were analyzed by enantioselective gas chromatography mass spectrometry on a Chirasil-L-Val capillary column. Besides common protein L-amino acids low amounts of D-amino acids were detected in fermented cocoa beans. Quantities of D-amino acids increased on heating. On roasting cocoa beans of the Forastero type from the Ivory Coast at 150 degrees C for 2 h, relative quantities of D-amino acids approached 17.0% D-Ala, 11.7% D-Ile, 11.1% D-Asx (Asp + Asn), 7.9% D-Tyr, 5.8% D-Ser, 4.8% D-Leu, 4.3% D-Phe, 37.0% D-Pro, and 1.2% D-Val. In cocoa powder and chocolate relative quantities amounted to 14.5% D-Ala, 10.6% D-Tyr, 9.8% D-Phe, 8.1% L-Asx, and 7.2% D-Ile. Lower quantities of other D-amino acids were also detected. In order to corroborate our hypothesis that D-amino acids are generated from Amadori compounds (fructose amino acids) formed in the course of the Maillard reaction, fructose-L-phenylalanine and fructose-D-phenylalanine were synthesized and heated at 200 degrees C for 5-60 min. Already after 5 min release of 11.7% D-Phe and 11.8% L-Phe in the free form could be analyzed. Based on the data a racemization mechanism is presented founded on the intermediate and reversible formation of an amino acid carbanion in the Amadori compounds.

  8. High gas temperature furnace for species determination of organometallic compounds with a high pressure liquid chromatograph and a Zeeman atomic absorption spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Koizumi, H.; McLaughlin, R.D.; Hadeishi, T.


    A new furnace has been constructed that allows atomic absorption detection of volatile organometallic compounds. The operation of this furnace is demonstrated by analyzing the eluent of a high pressure liquid chromatograph utilizing Zeeman atomic absorption spectrometry. The content of tetraethyllead in National Bureau of Standards gasoline standards was determined. Data are presented on the ability of this furnace to suppress interference with cadmium and lead determinations by MgCl/sub 2/, CuCl/sub 2/, and CaCl/sub 2/. It was found that two orders of magnitude more interferent can be tolerated. The determination of lead in automotive exhaust is also described. 7 figures, 4 tables.

  9. Ion-exclusion chromatographic behavior of aliphatic carboxylic acids and benzenecarboxylic acids on a sulfonated styrene--divinylbenzene co-polymer resin column with sulfuric acid containing various alcohols as eluent. (United States)

    Ohta, Kazutoku; Towata, Atsuya; Ohashi, Masayoshi


    The addition of C1-C7 alcohols (methanol, ethanol, propanol, butanol, heptanol, hexanol and heptanol) to dilute sulfuric acid as eluent in ion-exclusion chromatography using a highly sulfonated styrene-divinylbenzene co-polymer resin (TSKgel SCX) in the H+ form as the stationary phase was carried out for the simultaneous separations of both (a) C1-C7 aliphatic carboxylic acids (formic, acetic, propionic, isobutyric, butyric, isovaleric, valeric, 2-methylvaleric, isocaproic, caproic, 2,2-dimethyl-n-valeric, 2-methylhexanoic, 5-methylhexanoic and heptanoic acids) and (b) benzenecarboxylic acids (pyromellitic, hemimellitic, trimellitic, o-phthalic, m-phthalic, p-phthalic, benzoic and salicylic acids and phenol). Heptanol was the most effective modifier in ion-exclusion chromatography for the improvement of peak shapes and a reduction in retention volumes for higher aliphatic carboxylic acids and benzenecarboxylic acids. Excellent simultaneous separation and relatively highly sensitive conductimetric detection for these C1-C7 aliphatic carboxylic acids were achieved on the TSKgel SCX column (150 x 6 mm I.D.) in 30 min using 0.5 mM sulfuric acid containing 0.025% heptanol as eluent. Excellent simultaneous separation and highly sensitive UV detection at 200 nm for these benzenecarboxylic acids were also achieved on the TSKgel SCX column in 30 min using 5 mM sulfuric acid containing 0.075% heptanol as eluent.

  10. Headspace solid-phase microextraction and gas chromatographic analysis of low-molecular-weight sulfur volatiles with pulsed flame photometric detection and quantification by a stable isotope dilution assay. (United States)

    Ullrich, Sebastian; Neef, Sylvia K; Schmarr, Hans-Georg


    Low-molecular-weight volatile sulfur compounds such as thiols, sulfides, disulfides as well as thioacetates cause a sulfidic off-flavor in wines even at low concentration levels. The proposed analytical method for quantification of these compounds in wine is based on headspace solid-phase microextraction, followed by gas chromatographic analysis with sulfur-specific detection using a pulsed flame photometric detector. Robust quantification was achieved via a stable isotope dilution assay using commercial and synthesized deuterated isotopic standards. The necessary chromatographic separation of analytes and isotopic standards benefits from the inverse isotope effect realized on an apolar polydimethylsiloxane stationary phase of increased film thickness. Interferences with sulfur-specific detection in wine caused by sulfur dioxide were minimized by addition of propanal. The method provides adequate validation data, with good repeatability and limits of detection and quantification. It suits the requirements of wine quality management, allowing the control of oenological treatments to counteract an eventual formation of excessively high concentration of such malodorous compounds. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Recovery of deuterium from H-D gas mixture by thermal diffusion in a multi-concentric-tube column device of fixed total sum of column heights with transverse sampling streams

    International Nuclear Information System (INIS)

    Yeh, H.-M.


    The effect of the increment in the number of concentric-tube thermal diffusion columns on the recovery of deuterium from H 2 -HD-D 2 system with fixed total sum of column heights, has been investigated. The equations for predicting the degrees of separation in single-column, double-column and triple-column devices have been derived. Considerable improvement in recovery can be achieved if a multi-column device with larger number of column is employed, instead of a single-column device with column height equal to the same total sum of column heights, especially for the case of higher flow-rate operation and larger total sum of column heights.

  12. Operational O3M-SAF trace gas column products: GOME-2 ozone, NO2, BrO, SO2 and CH2O (United States)

    Hao, Nan; Valks, Pieter; Loyola, Diego; de Smedt, Isabelle; van Roozendael, Michel; Theys, Nicolas; Rix, Meike; Koukouli, Mariliza; Balis, Dimitris; Lambert, Jean-Christopher; Pinardi, Gaia; Zimmer, Walter; Emmadi, Sunil

    This contribution focuses on the operational GOME-2 trace gas column products developed at the German Aerospace Centre, in the framework of EUMETSAT's Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M-SAF). We present an overview of the retrieval algorithms and exemplary results for ozone, NO2, BrO, SO2 and CH2O. These trace gas column products are retrieved with the GOME Data Processor (GDP) version 4.x algorithm and the UPAS system. Total ozone and NO2 are retrieved with the Differential Optical Absorption Spectroscopy (DOAS) method using the UV wavelength region around 330 nm and 435 nm respectively. An additional algorithm is applied to retrieve the tropospheric NO2 column for polluted con-ditions. The operational ozone and NO2 products are available for the users in near real time, i.e. within two hours after sensing. SO2 emissions from volcanic and anthropogenic sources can be measured by GOME-2 around 320 nm. For BrO and CH2O, optimal DOAS fitting windows have been determined for GOME-2 in the UV wavelength region. The GOME-2 ozone, total and tropospheric NO2, SO2, BrO, CH2O and cloud products from DLR have reached the operational EUMETSAT O3M-SAF status. All these products are routinely available to the users via EUMETCast, WMO/GTS and FTP in HDF5 and BUFR format. We present initial validation results for GOME-2 products using ground-based measurements, as well as comparisons with other satellite products, such as those from SCIAMACHY and OMI. The use of tropospheric NO2, SO2 and CH2O columns for air quality applications will be presented, including temporal evolution analyses for China. Furthermore, we will show examples of BrO under polar winter conditions.

  13. An improved back-flush-to-vent gas chromatographic method for determination of trace permanent gases and carbon dioxide in ultra-high purity ammonia. (United States)

    Trubyanov, Maxim M; Mochalov, Georgy M; Vorotyntsev, Ilya V; Vorotyntsev, Andrey V; Suvorov, Sergey S; Smirnov, Konstantin Y; Vorotyntsev, Vladimir M


    A novel method for rapid, quantitative determination of trace permanent gases and carbon dioxide in ultra-high purity ammonia by dual-channel two-dimensional GC-PDHID is presented. An improved matrix back-flush-to-vent approach combining back-flush column switching technique with auxiliary NaHSO4 ammonia trap is described. The NaHSO4 trap prevents traces of ammonia from entering the analytical column and is shown not to affect the impurity content of the sample. The approach allows shortening the analysis time and increasing the amount of measurements without extensive maintenance of the GC-system. The performance of the configuration has been evaluated utilizing ammonia- and helium-based calibration standards. The method has been applied for the analysis of 99.9999+% ammonia purified by high-pressure distillation at the production site. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Liquid chromatographic-tandem mass spectrometric assay for ...

    African Journals Online (AJOL)

    Methods: Blood and urine samples were obtained from healthy volunteers who admitted to not being on any medications. The investigated analytes were chromatographically separated on a C18 column (Luna®-PFP 100Å column, 50 mm × 2.0 mm i.d., 3.0 μm) with the aid of a mobile phase containing A; acetonitrile (ACN) ...

  15. Development of a transportable gas analyzer: thermal desorber / micro gas chromatograph / mass spectrometer coupling (m-TD / m-GC / MS). Application to on-line analysis of volatile organic compounds at traces level; Developpement d'un analyseur de gaz transportable: couplage thermodesorbeur / micro-chromatographe / spectrometre de masse (m-TD / m-CG / SM). Application a l'analyse en ligne des composes organiques volatils a l'etat de traces

    Energy Technology Data Exchange (ETDEWEB)

    Cozic, R.


    Volatile organic compounds (VOC) play a central part in the photochemical pollution of the atmosphere. Monitoring of these products in air became a need, because of their toxicity. Currently, traditional analytical methods of air have drawbacks. Instruments are too specific or the technique consists in trapping pollutants and then to turn over the sample to the laboratory for analysis. The subject of the thesis is the development of an on-site analytical technique, offering new prospects for air analysis. The developed transportable analyzer results from the coupling of a thermal desorber (m-TD), a micro gas chromatograph (m-GC) and a mass spectrometer (MS). The instrument makes it possible, in a few minutes, to perform qualitative and quantitative analysis of a very broad range of VOC at traces level. An example of on-site application of the analyzer relates to the monitoring of working atmospheres. (author)


    High-performance liquid chromatographic separation of the individual enantiomers of 12 organophosphorus pesticides (OPs) was obtained on polysaccharide enantioselective HPLC columns using alkane-alcohol mobile phase. The OP pesticides were crotoxyphos, dialifor, fonofos, fenamiph...


    African Journals Online (AJOL)


    MICROSCOPIC, PHYSICOCHEMICAL AND CHROMATOGRAPHIC. FINGERPRINTS OF LEAVES OF NIGERIAN CASSIA TORA LINN. Fatokun Omolola T1*., EsievoKevwe B2., Ugbabe Grace E3. and Kunle Oluyemisi F4. Department of Medicinal Plant Research and Traditional Medicine, National Institute for.


    African Journals Online (AJOL)

    The spectro-analytical techniques used for characterization included energy dispersive X-ray fluorescence (EDXRF), X-ray diffractometry (XRD), Optical microscopy, infrared (IR) and UV-VIS spectroscopy. Four different fractions having colours yellow, grey, orange and purple were obtained from the chromatographic ...

  19. Power to Fuels: Dynamic Modeling of a Slurry Bubble Column Reactor in Lab-Scale for Fischer Tropsch Synthesis under Variable Load of Synthesis Gas

    Directory of Open Access Journals (Sweden)

    Siavash Seyednejadian


    Full Text Available This research developed a comprehensive computer model for a lab-scale Slurry Bubble Column Reactor (SBCR (0.1 m Dt and 2.5 m height for Fischer–Tropsch (FT synthesis under flexible operation of synthesis gas load flow rates. The variable loads of synthesis gas are set at 3.5, 5, 7.5 m3/h based on laboratory adjustments at three different operating temperatures (483, 493 and 503 K. A set of Partial Differential Equations (PDEs in the form of mass transfer and chemical reaction are successfully coupled to predict the behavior of all the FT components in two phases (gas and liquid over the reactor bed. In the gas phase, a single-bubble-class-diameter (SBCD is adopted and the reduction of superficial gas velocity through the reactor length is incorporated into the model by the overall mass balance. Anderson Schulz Flory distribution is employed for reaction kinetics. The modeling results are in good agreement with experimental data. The results of dynamic modeling show that the steady state condition is attained within 10 min from start-up. Furthermore, they show that step-wise syngas flow rate does not have a detrimental influence on FT product selectivity and the dynamic modeling of the slurry reactor responds quite well to the load change conditions.

  20. Development and Validation of a Liquid Chromatographic Method ...

    African Journals Online (AJOL)

    A liquid chromatographic method for the simultaneous determination of six human immunodeficiency virus (HIV) protease inhibitors, indinavir, saquinavir, ritonavir, amprenavir, nelfinavir and lopinavir, was developed and validated. Optimal separation was achieved on a PLRP-S 100 Å, 250 x 4.6 mm I.D. column maintained ...

  1. Transport Characteristics of Porous Solids Derived from Chromatographic Measurements

    Czech Academy of Sciences Publication Activity Database

    Šolcová, Olga; Schneider, Petr


    Roč. 144, - (2002), s. 475-482 ISSN 0167-2991 R&D Projects: GA ČR GA104/01/0546; GA AV ČR IAA4072915 Keywords : transport parameters * diffusion coefficients * chromatographic column Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.468, year: 2002

  2. PNNL Report on the Development of Bench-scale CFD Simulations for Gas Absorption across a Wetted Wall Column

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chao; Xu, Zhijie; Lai, Canhai; Whyatt, Greg A.; Marcy, Peter; Gattiker, J. R.; Sun, Xin


    This report is prepared for the demonstration of hierarchical prediction of carbon capture efficiency of a solvent-based absorption column. A computational fluid dynamics (CFD) model is first developed to simulate the core phenomena of solvent-based carbon capture, i.e., the CO2 physical absorption and chemical reaction, on a simplified geometry of wetted wall column (WWC) at bench scale. Aqueous solutions of ethanolamine (MEA) are commonly selected as a CO2 stream scrubbing liquid. CO2 is captured by both physical and chemical absorption using highly CO2 soluble and reactive solvent, MEA, during the scrubbing process. In order to provide confidence bound on the computational predictions of this complex engineering system, a hierarchical calibration and validation framework is proposed. The overall goal of this effort is to provide a mechanism-based predictive framework with confidence bound for overall mass transfer coefficient of the wetted wall column (WWC) with statistical analyses of the corresponding WWC experiments with increasing physical complexity.

  3. Modeling and simulation of a pseudo-two-phase gas-liquid column reactor for thermal hydrocracking of petroleum heavy fractions

    Directory of Open Access Journals (Sweden)

    E.M. Matos


    Full Text Available This work presents a model to predict the behavior of velocity, gas holdup and local concentration fields in a pseudo-two-phase gas-liquid column reactor applied for thermal hydrocracking of petroleum heavy fractions. The model is based on the momentum and mass balances for the system, using an Eulerian-Eulerian approach. Using the k-epsilon model,fluid dynamics accounts for both laminar and turbulent flows, with discrete small bubbles (hydrogen flowing in a continuous pseudohomogeneous liquid phase (oil and catalyst particles. The petroleum is assumed to be a mixture of pseudocomponents, grouped by similar chemical structural properties, and the thermal hydrocracking is taken into account using a kinetic network based on these pseudocomponents.

  4. From slant column densities to trace gas profiles: Post processing data from the new MAX-DOAS network in Mexico City (United States)

    Friedrich, M. M.; Stremme, W.; Rivera, C. I.; Arellano, E. J.; Grutter, M.


    The new MAX-DOAS network in Mexico City provides results of O4, HCHO and NO2 slant column densities (SCD). Here, we present a new numerical code developed to retrieve gas profiles of NO2 and HCHO using radiative transfer simulations. We present first results of such profiles from the MAX-DOAS station located at UNAM campus. The code works in two steps: First, the O4 slant column density information is used to retrieve an aerosol profile. As an a-priori aerosol profile, we use averaged ceilometer data measured at UNAM and scaled to the total optical depth provided by the Aeronet data base. In the second step, the retrieved aerosol profile information is used together with the trace gas (HCHO or NO2) SCDs to retrieve the trace gas profiles. The inversion is based on a gauss-newton iteration scheme and uses constrained least square fitting with either optimal estimation or Tihkonov regularization. For the latter, the regulation matrix is currently constructed from the discrete first derivative operator. The forward model uses the radiative transfer code VLIDORT. The inputs to VLIDORT are calculated using temperature and pressure information from daily radiosounde measurements and aerosol single scattering optical depths and asymmetry factors from the Aeronet data base for Mexico City. For the gas absorption cross sections we use the same values as were used for the SCD calculation from the recorded spectra using QDOAS. Besides demonstrating the functionality of the algorithm showing profile retrievals of simulated SCDs with added random noise, we present HCHO and NO2 profiles retrieved from SCDs calculated from the MAX-DOAS measurements at UNAM campus at selected days.

  5. Evaluation of Gas Retention in Waste Simulants: Intermediate-Scale Column and Open-Channel-Depth Tests

    Energy Technology Data Exchange (ETDEWEB)

    Powell, Michael R.; Gauglitz, Phillip A.; Denslow, Kayte M.; Fischer, Christopher M.; Heldebrant, David J.; Prowant, Matthew S.; Sande, Susan; Davis, James M.; Telander, Monty R.


    Gas generation in Hanford’s radioactive waste storage tanks can lead to gas accumulation within the layer of settled solids (sludge) at the tank bottom. The gas, which may be hazardous and/or flammable, is formed principally by radiation-driven chemical reactions. Accumulation of these gases within the sludge increases the sludge-layer volume, which decreases the available tank volume for waste storage. Further, accumulation of large amounts of gas in the sludge can potentially result in a relatively rapid release of the accumulated gas if the sludge-layer density is reduced to less than that of the overlying sludge or that of the supernatant liquid. The potential for rapid release of large amounts of hazardous and/or flammable gases is a safety hazard that needs to be managed. Accordingly, a thorough understanding is needed of the circumstances that can lead to problematic gas accumulation in sludge layers. The Deep-Sludge Gas Release Event Project (DSGREP) is tasked with developing an improved understanding of these gas release events.

  6. Comparison of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography for the separation of synthetic cathinones. (United States)

    Carnes, Stephanie; O'Brien, Stacey; Szewczak, Angelica; Tremeau-Cayel, Lauriane; Rowe, Walter F; McCord, Bruce; Lurie, Ira S


    A comparison of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography for the separation of synthetic cathinones has been conducted. Nine different mixtures of bath salts were analyzed in this study. The three different chromatographic techniques were examined using a general set of controlled synthetic cathinones as well as a variety of other synthetic cathinones that exist as positional isomers. Overall 35 different synthetic cathinones were analyzed. A variety of column types and chromatographic modes were examined for developing each separation. For the ultra high performance supercritical fluid chromatography separations, analyses were performed using a series of Torus and Trefoil columns with either ammonium formate or ammonium hydroxide as additives, and methanol, ethanol or isopropanol organic solvents as modifiers. Ultra high performance liquid chromatographic separations were performed in both reversed phase and hydrophilic interaction chromatographic modes using SPP C18 and SPP HILIC columns. Gas chromatography separations were performed using an Elite-5MS capillary column. The orthogonality of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography was examined using principal component analysis. For the best overall separation of synthetic cathinones, the use of ultra high performance supercritical fluid chromatography in combination with gas chromatography is recommended. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Design of a compressed air modulator to be used in comprehensive multidimensional gas chromatography and its application in the determination of pesticide residues in grapes

    NARCIS (Netherlands)

    Pizzutti, I.R.; Vreuls, J.J.; Kok, A; Roehrs, R.; Martel, S.; Friggi, C.A.; Zanella, R.


    In this study, a new modulator that is simple, robust and presents low operation costs, was developed. This modulator uses compressed air to cool two small portions in the first centimeters of the second chromatographic column of a comprehensive multidimensional gas chromatography (GC × GC) system.

  8. An analytical study by gas liquid chromatography and radiochromatography of tritium labelled lebaycid

    International Nuclear Information System (INIS)

    Perez Garcia, M. M.


    The stability and purity of the syntheses products of Lebaycid: 0,0 dime thylfosfochlorothionate and 4 methyl-thio-m-cresol were investigated by gas liquid chromatography. The study on (CH 3 O) 2 PSC1 was made in a column of Silicone SE-30, Reoplex 400 using a thermal conductivity detector. The 99,4% pure product obtained from the preparative gas chromatograph was found to be stable within the duration of the experiment: seven months. (Author) 23 refs

  9. Separating methane emissions from agricultural sources and natural gas: direct measurements of excess columns of CH4, C2H6 and NH3 in the Colorado Front Range (United States)

    Kille, N.; Chiu, R.; Frey, M.; Hase, F.; Kumar Sha, M.; Blumenstock, T.; Hannigan, J. W.; Volkamer, R. M.


    Methane (CH4) is a major greenhouse gas emitted from biogenic, thermogenic, and pyrogenic sources. Here we demonstrate a novel approach to separate sources of CH4 emissions based on a network of small portable sensors performing column measurements in the Northern Colorado Front Range (NCFR). In the study area CH4 is emitted from biogenic sources such as concentrated animal feeding operations (CAFOs) and natural gas production and storage. In March 2015 we deployed a network of five Fourier Transform Spectrometers (FTS) to characterize the regional scale methane dome in Colorado's Denver-Julesburg Basin based on excess vertical column measurements (the column enhancement inside the dome over background). Three EM27sun FTS measured CH4, oxygen (O2) and water vapor (H2O) columns at Eaton, CO (inside the dome) and at two boundary sites; the CU mobile SOF (Solar Occultation Flux) measured ethane (C2H6), ammonia (NH3), and H2O at Eaton, CO. The column averaged dry air mole fractions XCH4, XC2H6, and XNH3 were determined using O2 columns for air mass factor normalization, and background column was subtracted to derive excess vertical columns of DXCH4, DXC2H6, DXNH3 at Eaton, CO. Eaton is located both near CAFOs and at the northern edge of oil and natural gas production wells. Our approach for source apportioning methane employs a linear regression analysis that explains DXCH4 in terms of DXC2H6 as tracer for natural gas sources, and DXNH3 as tracer for CAFO emissions. The results of the source apportionment are compared with literature values of the NH3/CH4 and C2H6/CH4 ratio to evaluate the method of excess columns, which is independent of boundary layer height.

  10. Widespread gas emissions in the Sea of Marmara in relation with the tectonic and sedimentary environments: Results from shipborne multibeam echosounder water column imagery (MARMESONET expedition, 2009) (United States)

    Dupré, Stéphanie; Scalabrin, Carla; Géli, Louis; Henry, Pierre; Grall, Céline; Tary, Jean-Baptiste; Ćaǧatay, Namık.; Imren, Caner


    Acoustic systems in marine geosciences are mainly used to explore the seabed and image sub-bottom sedimentary units. However, side-scan sonars and echosounders can detect gas emissions from the seabed into the water column. Recently, advances in technology and computer processing allow carrying out large-scale 3D surveys of the entire water column with multibeam systems, so far dedicated to seabed imagery. A shipborne multibeam survey of the water column in the Sea of Marmara was performed with the R/V Le Suroit during the MARMESONET expedition (4-25 November 2009), that is part of the ESONET (European Seas Observatory NETwork) demonstration mission MarmaraDM. Data were acquired with a Simrad EM302 multibeam echosounder (27-33 kHz, 288 beams, 1°x2°, 2 or 5 ms pulse length) with automatic swath width control and equidistant sounding pattern over water depths varying from 300 to 1300 m. Volume backscattering coefficients were stored with m depth bins along more than 2000 nm acoustic tracks. Gas bubble echoes were very well detected by the EM302 system within the water depth range of the Sea of Marmara, mostly with the central beams but also with the outer beams for the flares with strong backscatter intensity and large imprint. Geo-referenced gas flare 3D visualization is performed with Movies3D software developed for fish school echo description and biomass assessment (Trenkel et al., 2009). The distribution of water column acoustic echoes in the Sea of Marmara reveals that free gas emissions from the seabed are more widespread than expected from previous studies using ROVs, submersibles as well as acoustic methods (Géli et al., 2008; Zitter et al., 2008). Numerous acoustic gas flares were detected in association with the North Anatolian fault system and some appear to be localized on known active fault traces. However, gas emissions also spread around the edges of the sedimentary basins (e.g. Cinarcik and Tekirdag basins) and on structural highs (e.g. Western

  11. Trans fat labeling and levels in U.S. foods: assessment of gas chromatographic and infrared spectroscopic techniques for regulatory compliance. (United States)

    Mossoba, Magdi M; Moss, Julie; Kramer, John K G


    Trans fatty acids are found in a variety of foods like dairy and meat products, but the major dietary sources are products that contain commercially hydrogenated fats. There has been a renewed need for accurate analytical methods for the quantitation of total trans fat since mandatory requirements to declare the amount of trans fat present in food products and dietary supplements were issued in many countries. Official capillary GC and IR methodologies are the two most common validated methods used to identify and quantify trans fatty acids for regulatory compliance. The present article provides a comprehensive discussion of the GC and IR techniques, including the latest attenuated total reflection (ATR)-FTIR methodology called the negative second derivative ATR-FTIR procedure, which is currently being validated in an international collaborative study. The identification and quantitation of trans fatty acid isomers by GC is reviewed and an alternative GC method is proposed using two temperature programs and combining their results; this proposed method deals more effectively with the resolution of large numbers of geometric and positional monoene, diene, and triene fatty acid isomers present in ruminant fats. In addition, the different methylation procedures that affect quantitative conversion to fatty acid methyl esters are reviewed. There is also a lack of commercial chromatographic standards for many trans fatty acid isomers. This review points to potential sources of interferences in the FTIR determination that may lead to inaccurate results, particularly at low trans levels. The presence of high levels of saturated fats may lead to interferences in the FTIR spectra observed for trans triacylglycerols (TAGs). TAGs require no derivatization, but have to be melted prior to IR measurement. While GC is currently the method of choice, ATR-FTIR spectroscopy is a viable, rapid alternative, and a complementary method to GC for a more rapid determination of total trans

  12. Role of substituents in cyclodextrin derivatives for enantioselective gas chromatographic separation of chiral terpenoids in the essential oils of Mentha spicata. (United States)

    Pragadheesh, V S; Yadav, Anju; Chanotiya, Chandan Singh


    Enantioselective GC-FID and enantioselective GC-MS have been utilized under temperature gradient mode with differently substituted heptakis- and octakis-cyclodextrins to achieve the resolution of chiral terpenoids in the essential oil of indigenously grown cultivars of Mentha spicata. Modified cyclodextrins were derivatized in GC column for the separation of chiral terpenoids. A 2,3-diethyl-6-tert-butyldimethylsilyl-β-cyclodextrin doped into 14% cyanopropylphenyl/86%dimethylpolysiloxane (TBDE-β-CD) showed good enantioselectivity for all the studied chiral compounds excluding carvone. Carvone enantiomers were well resolved in 2,3-diacetoxy-6-tert-butyldimethylsilyl-β-cyclodextrin column (TBDA-β-CD) with enantioseparation (Es) of 1.006. A TBDE-β-CD provides maximum enantiomeric separation for β-pinene (Es 1.038), sabinene (Es 1.051), limonene (Es 1.045), isomenthone (Es 1.029) and α-terpineol (Es 1.014). Furthermore, enantiomer elution order reversal was observed for sabinene, menthone, terpinen-4-ol and menthol while changing from β- to γ-cyclodextrin phase. Carvone exhibits enantiomer elution order reversal by changing substituents i.e., methyl to acetyl at 2- & 3- position of the cyclodextrin derivative. Chiral constituents such as (+)-isomenthone, (-)-menthone, (1R,2S,5R)-(-)-menthol and (4S)-(+)-piperitone exist as a single enantiomer with >99% excess. Existence of (R)-(+)-limonene and (S)-(+)-carvone enantiomers has been proven first time in M. spicata essential oils and can be used as the marker for Indian origin. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Smooth esterification of Di-and Tricarboxylic acids with methyl and ethyl chloroformates in gas chromatographic profiling of urinary acidic metabolites

    Czech Academy of Sciences Publication Activity Database

    Hušek, Petr; Šimek, Petr; Matucha, P.


    Roč. 58, - (2003), s. 623-630 ISSN 0009-5893 R&D Projects: GA AV ČR IPP1050128; GA ČR GA203/01/1586 Institutional research plan: CEZ:AV0Z5007907 Keywords : gas chromatography * esterification with chloroformates Subject RIV: CC - Organic Chemistry Impact factor: 1.145, year: 2003

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

    NARCIS (Netherlands)

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


    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

  15. How to select equivalent and complimentary reversed phase liquid chromatography columns from column characterization databases. (United States)

    Borges, Endler M


    Three RP-LC column characterization protocols [Tanaka et al. (1989), Snyder et al. (PQRI, 2002), and NIST SRM 870 (2000)] were evaluated using both Euclidian distance and Principal Components Analysis to evaluate effectiveness at identifying equivalent columns. These databases utilize specific chromatographic properties such as hydrophobicity, hydrogen bonding, shape/steric selectivity, and ion exchange capacity of stationary phases. The chromatographic parameters of each test were shown to be uncorrelated. Despite this, the three protocols were equally successful in identifying similar and/or dissimilar stationary phases. The veracity of the results has been supported by some real life pharmaceutical separations. The use of Principal Component Analysis to identify similar/dissimilar phases appears to have some limitations in terms of loss of information. In contrast, the use of Euclidian distances is a much more convenient and reliable approach. The use of auto scaled data is favoured over the use of weighted factors as the former data transformation is less affected by the addition or removal of columns from the database. The use of these free databases and their corresponding software tools shown to be valid for identifying similar columns with equivalent chromatographic selectivity and retention as a "backup column". In addition, dissimilar columns with complimentary chromatographic selectivity can be identified for method development screening strategies. Copyright © 2013 Elsevier B.V. All rights reserved.

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

    Directory of Open Access Journals (Sweden)



    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.

  17. Influence of the gas-liquid flow configuration in the absorption column on photosynthetic biogas upgrading in algal-bacterial photobioreactors. (United States)

    Toledo-Cervantes, Alma; Madrid-Chirinos, Cindy; Cantera, Sara; Lebrero, Raquel; Muñoz, Raúl


    The potential of an algal-bacterial system consisting of a high rate algal pond (HRAP) interconnected to an absorption column (AC) via recirculation of the cultivation broth for the upgrading of biogas and digestate was investigated. The influence of the gas-liquid flow configuration in the AC on the photosynthetic biogas upgrading process was assessed. AC operation in a co-current configuration enabled to maintain a biomass productivity of 15gm -2 d -1 , while during counter-current operation biomass productivity decreased to 8.7±0.5gm -2 d -1 as a result of trace metal limitation. A bio-methane composition complying with most international regulatory limits for injection into natural gas grids was obtained regardless of the gas-liquid flow configuration. Furthermore, the influence of the recycling liquid to biogas flowrate (L/G) ratio on bio-methane quality was assessed under both operational configurations obtaining the best composition at an L/G ratio of 0.5 and co-current flow operation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. A Hollow-Waveguide Gas Correlation Radiometer for Ultra-Precise Column Measurements of Formaldehyde on Mars (United States)

    Wilson, Emily L.; Neveu, Marc; Riris, Haris; Georgieva, Elena M.; Heaps, William S.


    We present preliminary results in the development of a miniaturized gas correlation radiometer that implements a hollow-core optical fiber (hollow waveguide) gas correlation cell. The substantial reduction in mass and volume of the gas correlation cell makes this technology appropriate for an orbital mission -- capable of pinpointing sources of trace gases in the Martian atmosphere. Here we demonstrate a formaldehyde (H2CO) sensor and report a detection limit equivalent to approximately 30 ppb in the Martian atmosphere. The relative simplicity of the technique allows it to be expanded to measure a range of atmospheric trace gases of interest on Mars such as methane (CH4), water vapour (H2O), deuterated water vapour (HDO), and methanol (CH3OH). Performance of a formaldehyde instrument in a Mars orbit has been simulated assuming a 3 meter long, 1000 micron inner diameter hollow-core fiber gas correlation cell, a 92.8 degree sun-synchronous orbit from 400 km with a horizontal sampling scale of 10 km x 10 km. Initial results indicate that for one second of averaging, a detection limit of 1 ppb is possible.

  19. Analysis of s-triazine herbicides in model systems and samples of groundwater by gas and liquid chromatography

    Directory of Open Access Journals (Sweden)

    Kostadinović Ljiljana


    Full Text Available In this paper, residues of s-triazine herbicides (Simazine, Atrazine, Amethrine, Promethrine and Azyprothrine have been determined in samples of model systems and real groundwater samples by gas-chromatography and high performance liquid chromatography. S-triazine herbicides were isolated from water samples by chloroform-methanol mixture (1:1, followed by purification of extract on the Al2O3 column. Gas-chromatographic determination the residues of s-triazines is performed on parallel capilar columns ULTRA I and ULTRA II, using specific NP detector. Liquid-chromatographic determination the s-triazines was performed on the column TSK ODS-120 A 5 mm 'LKB', using the mobile phase methanol-water (60:40. Total concentration of s-triazines in samples of Danube water was 3.54 mg dm-3. .

  20. [Determination of pyrethroid pesticides in tea by series two-solid phase extraction-columns cleanup and gas chromatography-tandem mass spectrometry]. (United States)

    Liu, Li; Zhang, Qi; Wang, Haiyan; Feng, Feng; Cao, Hairong; Yang, Zhen; Ke, Zhijun; Chen, Xiyao


    A rapid determination method of three pyrethroid pesticides (cyfluthrin, cypermethrin and fenvalerate) in tea was developed by series two-solid phase extraction-column cleanup and external standard method coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) in 30 min. The pesticide residues in tea were extracted with acetonitrile, and cleaned up by Carb/NH 2 and SLH solid-phase extraction columns. After filtration, the target compounds were analyzed by GC-MS and quantified by the external standard method. Under the optimized conditions, good linear ranges of 0.05-2.00 mg/kg were obtained. The limits of detection varied from 0.3 to 1.0 μ g/kg. The linear correlation coefficients were greater than 0.999. At three spiked levels (0.10, 0.50 and 2.00 mg/L), the average recoveries were determined between 80.6% and 116.3% in the four matrices. The inter-day relative standard deviations were between 1.3%-12.6%, and the intra-day relative standard deviations were between 2.7% and 12.1%. This method is simple, fast, and has a good reproducibility, which can meet the requirements of the rapid detection of pyrethroid pesticides in tea.

  1. Validation of a method for simultaneous determination of menthol and methyl salicylate in pharmaceuticals by capillary gas chromatography with cool on-column injection. (United States)

    Krzek, Jan; Czekaj, Janusz Sławomir; Rzeszutko, Włodzimierz


    The conditions for the identification and quantitative determination of menthol and methyl salicylate in ointment Balsamum Mentholi Compositum on a hydrocarbon-ester base (vaseline-lanolin), have been established by using capillary gas chromatography with cool on-column injection and flame ionization detection (FID). The good separation of menthol (tR = 7.2 min), methyl salicylate (tR = 8.7 min) and thymol (tR = 12.3 min) and camphor (tR = 6.0 min), used as alternative internal standards, beside vehiculum constituents (peak of tR = 15.8 min) was obtained. The method features a high sensitivity - detection limit for menthol and methyl salicylate was 0.1 ng and 5.0 ng, respectively, high accuracy, precision and recovery for active substances: 100.0% +/- 2.2%, when camphor was used as an internal standard.

  2. High-pressure liquid chromatography with direct injection of gas sample. (United States)

    Astanin, Anton I; Baram, Grigory I


    The conventional method of using liquid chromatography to determine the composition of a gaseous mixture entails dissolving vapors in a suitable solvent, then obtaining a chromatograph of the resulting solution. We studied the direct introduction of a gaseous sample into a C18 reversed-phase column, followed by separation of the components by HPLC with UV detection. Since the chromatography was performed at high pressure, vapors readily dissolved in the eluent and the substances separated in the column as effectively as in liquid samples. Samples were injected into the column in two ways: a) through the valve without a flow stop; b) after stopping the flow and relieving all pressure. We showed that an injectable gas volume could reach 70% of column dead volume. When an injected gaseous sample volume was less than 10% of the column dead volume, the resulting peaks were symmetrical and the column efficiency was high. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Practical and theoretical aspects of designing a flame-ionization detector/mass spectrometer Deans' switch. Pressure-flow relations in gas chromatography-detector interfaces using vacuum-outlet conditions.

    NARCIS (Netherlands)

    Blomberg, J.; Brinkman, U.A.T.


    In gas chromatographic (GC) practice, straightforward splitting of the column effluent over a mass spectrometry (MS) system and a flame-ionization detection (FID) system leads to unpredictable split ratios and, thus, to poor quantification. We therefore decided to implement a Deans' switch, which

  4. 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)

    International Nuclear Information System (INIS)

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


    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.

  5. Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of chlorinated pesticides in aquatic tissue by capillary-column gas chromatography with electron-capture detection (United States)

    Leiker, Thomas J.; Madsen, J.E.; Deacon, J.R.; Foreman, W.T.


    A method for the determination of chlorinated organic compounds in aquatic tissue by dual capillary-column gas chromatography with electron-capture detection is described. Whole-body-fish or corbicula tissue is homogenized, Soxhlet extracted, lipid removed by gel permeation chromatography, and fractionated using alumina/silica adsorption chromatography. The extracts are analyzed by dissimilar capillary-column gas chromatography with electron-capture detection. The method reporting limits are 5 micrograms per kilogram (μg/kg) for chlorinated compounds, 50 μg/kg for polychlorinated biphenyls, and 200 μg/kg for toxaphene.

  6. Application of ethyl esters and d3-methyl esters as internal standards for the gas chromatographic quantification of transesterified fatty acid methyl esters in food. (United States)

    Thurnhofer, Saskia; Vetter, Walter


    Ethyl esters (FAEE) and trideuterium-labeled methyl esters (d3-FAME) of fatty acids were prepared and investigated regarding their suitability as internal standards (IS) for the determination of fatty acids as methyl esters (FAME). On CP-Sil 88, ethyl esters of odd-numbered fatty acids eluted approximately 0.5 min after the respective FAME, and only coelutions with minor FAME were observed. Depending on the problem, one or even many FAEE can be added as IS for the quantification of FAME by both GC-FID and GC-MS. By contrast, d3-FAME coeluted with FAME on the polar GC column, and the use of the former as IS requires application of GC-MS. In the SIM mode, m/z 77 and 90 are suggested for d3-methyl esters of saturated fatty acids, whereas m/z 88 and 101 are recommended for ethyl esters of saturated fatty acids. These m/z values give either no or very low response for FAME and can thus be used for the analysis of FAME in food by GC-MS in the SIM mode. Fatty acids in sunflower oil and mozzarella cheese were quantified using five saturated FAEE as IS. Gravimetric studies showed that the transesterification procedure could be carried out without of loss of fatty acids. GC-EI/MS full scan analysis was suitable for the quantitative determination of all unsaturated fatty acids in both food samples, whereas GC-EI/MS in the SIM mode was particularly valuable for quantifying minor fatty acids. The novel GC-EI/MS/SIM method using fatty acid ethyl esters as internal standards can be used to quantify individual fatty acids only, that is, without determination of all fatty acids (the common 100% method), although this is present. This was demonstrated by the exclusive quantification of selected fatty acids including methyl-branched fatty acids, erucic acid (18:1n-9trans), and polyunsaturated fatty acids in cod liver oil and goat's milk fat.

  7. A new headspace gas chromatographic method for the determination of methanol content in paper materials used for food and drink packaging. (United States)

    Hu, Hui-Chao; Tian, Ying-Xin; Jin, Hui-Jun; Chai, Xin-Sheng; Barnes, Donald G


    This study reports on a method for determination of methanol in paper products by headspace gas chromatography (HS-GC). The method is based on the hydrolysis of the pulp or paper matrix, using a phosphoric acid solution (42.5%) as the medium at 120 °C in 5 h (excluding air contact) in order to release matrix-entrapped methanol, which is then determined by HS-GC. Data show that, under the given conditions of hydrolysis, no methanol was formed from the methoxyl groups in the material. Reproducibility tests of the method generated a relative standard deviation of methanol content in paper-related materials. The method can play an important role in addressing food safety concerns that may be raised regarding the use of paper materials in food and beverage packaging.

  8. Gas chromatographic determination of N-nitrosamines, aromatic amines, and melamine in milk and dairy products using an automatic solid-phase extraction system. (United States)

    Jurado-Sanchez, Beatriz; Ballesteros, Evaristo; Gallego, Mercedes


    A reliable analytical method was presented for the simultaneous determination of six N-nitrosamines, nine aromatic amines, and melamine in milk and dairy products using gas chromatography coupled with mass spectrometry. The sample treatment includes the precipitation of proteins with acetonitrile, centrifugation, solvent changeover by evaporation, and continuous solid-phase extraction for cleanup and preconcentration purposes. Samples (5 g) containing 0.15-500 ng of each amine were analyzed, and low detection limits (15-130 ng/kg) were achieved. Recoveries for milk and dairy products samples spiked with 1, 10, and 50 μg/kg ranged from 92% to 101%, with intraday and interday relative standard deviation values below 7.5%. The method was successfully applied to determine amine residues in several milk types (human breast, cow, and goat) and dairy products.

  9. Total cholesterol in serum determined by isotope dilution/mass spectrometry, with liquid-chromatographic separation

    International Nuclear Information System (INIS)

    Takatsu, Akiko; Nishi, Sueo


    We describe an accurate, precise method for determination of total serum cholesterol by isotope dilution/mass spectrometry (IDMS) with liquid chromatographic separation. After adding [3,4- 13 C] cholesterol to serum and hydrolyzing the cholesterol esters, we extract the total cholesterol. High-performance liquid chromatography (HPLC) is used to separate the extracted cholesterol for measurement by electron-impact mass spectrometry with use of a direct-insertion device. To evaluate the specificity and the accuracy of this method, we also studied the conventional IDMS method, which involves converting cholesterol to the trimethylsilyl ether and assay by gas chromatography-mass spectrometry with use of a capillary column. The coefficient of variation for the HPLC method was a little larger than for the conventional method, but mean values by each method agreed within 1% for all sera tested. (author)

  10. CO2 Absorption from Biogas by Glycerol: Conducted in Semi-Batch Bubble Column (United States)

    puji lestari, Pratiwi; Mindaryani, Aswati; Wirawan, S. K.


    Biogas is a renewable energy source that has been developed recently. The main contents of Biogas itself are Methane and carbon dioxide (CO2) where Methane is the main component of biogas with CO2 as the highest impurities. The quality of biogas depends on the CO2 content, the lower CO2 levels, the higher biogas quality. Absorption is one of the methods to reduce CO2 level. The selections of absorbent and appropriate operating parameters are important factors in the CO2 absorption from biogas. This study aimed to find out the design parameters for CO2 absorption using glycerol that represented by the overall mass transfer coefficient (KLa) and Henry’s constant (H). This study was conducted in semi-batch bubble column. Mixed gas was contacted with glycerol in a bubble column. The concentration of CO2 in the feed gas inlet and outlet columns were analysed by Gas Chromatograph. The variables observed in this study were superficial gas velocity and temperatures. The results showed that higher superficial gas velocity and lower temperature increased the rate of absorption process and the amount of CO2 absorbed.

  11. Determinação espectrofotométrica e cromatográfica em fase gasosa de ácido tricloracético em urina Spectrophotometric and gas chromatographic determination of trichloroacetic acid in urine

    Directory of Open Access Journals (Sweden)

    Maria de Fatima M. Pedrozo


    Full Text Available Solventes halogenados -- 1,1,1-tricloretano, tricloretileno, percloretileno -- apresentam o ácido tricloracético (TCA como produto de biotransformação comum, o qual pode ser utilizado como indicador biológico de dose interna na exposição a estes compostos. Foi realizado estudo de métodos espectrofotométrico e cromatográfico em fase gasosa para a determinação do TCA, bem como da aplicação destes métodos à sua determinação em urina de indivíduos expostos ao 1,1,1-tricloretano. Os resultados mostram a boa precisão à determinação do TCA em urina de indivíduos expostos ao 1,1,1-tricloretano e nenhuma diferença significativa foi observada entre os métodos, ainda que o cromatográfico em fase gasosa apresentasse menor limite de detecção.Some chlorinated hydrocarbon solvents -- 1,1,1-trichloroethane, tricloroethylene and perchloroethylene -- have a common biotransformation product, trichloroacetic acid, which can be used as their biological exposure index. The spectrophotometric and gas chromatographic methods for the determination of trichloroacetic acid were studied and used as well as in its determination in the urine of workers exposed to 1,1,1-trichloroethane . Both methods showed good precision and no statistically significant difference was found although the gas cromatographic method presented a lower detection limit.

  12. A dual-channel gas chromatography method for the quantitation of low and high concentrations of NF3 and CF4 to study membrane separation of the two compounds


    Branken, D.J.; Le Roux, J.P.; Krieg, H.M.; Lachmann, G.


    A dual-channel gas chromatographic method is described in this paper that can be conveniently used for quantitation of NF3/CF4 mixtures with a thermal conductivity detector (TCD) on one channel for the quantitation of high-concentrations, and a pulsed discharge helium ionization detector (PDHID) on a second channel for the quantitation of low concentrations. It is shown that adequate separation is achieved on both channels with this dual single-column setup in which column switchi...

  13. Combination of electromembrane extraction with dispersive liquid-liquid microextraction followed by gas chromatographic analysis as a fast and sensitive technique for determination of tricyclic antidepressants. (United States)

    Seidi, Shahram; Yamini, Yadollah; Rezazadeh, Maryam


    For the first time, combination of electromembrane extraction (EME) and dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography-flame ionization detection (GC/FID) was developed for determination of tricyclic antidepressants (TCAs) in untreated human plasma and urine samples. Response surface methodology (RSM) was used for optimization of experimental parameters, so that extraction time of 14min, voltage of 240V, donor phase of 64mM HCl and acceptor phase of 100mM HCl were obtained as optimal extraction conditions. Matrix effect and carry-over were investigated in this work. The results indicated matrix effect for urine and plasma samples in comparison with neat solutions, so match matrix method was used for drawing working calibration curves. However, no carry-over was appeared at the retention time of investigated TCAs (S/N86.5%. The results showed that EME-DLLME-GC/FID is a promising combination for analysis of TCAs present at low concentrations in biological matrices. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Gas chromatographic quantification of aliphatic aldehydes in freshly distilled Calvados and Cognac using 3-methylbenzothiazolin-2-one hydrazone as derivative agent. (United States)

    Ledauphin, Jérôme; Barillier, Daniel; Beljean-Leymarie, Martine


    A new precise and sensitive method was used for the quantification of aliphatic aldehydes from C5 to C11 in highly ethanolic beverages such as freshly distilled spirits. Carbonyl compounds were derivatized using 3-methylbenzothiazolin-2-one hydrazone (MBTH) and then separated and detected by gas chromatography-mass spectrometry (GC-MS). Selective mass spectrometric detection of molecular ions of derivatives was performed to obtain a good sensibility (0.2-1.2 microg l(-1)) and a good selectivity. For a concentration of 20 microg l(-1), relative standard deviations were lower than 10% except for heaviest compounds (decanal and undecanal) where RSD were between 11 and 13%. The concentrations of aliphatic aldehydes were determined in nine samples of freshly distilled Calvados and two samples of freshly distilled Cognac with highest concentrations reported for 3-methylbutanal (from 170 to 1220 microg l(-1) in Calvados and from 1540 to 5500 microg l(-1) in Cognac). 3-Methylbutanal and hexanal, due to their low detection thresholds, could be important olfactive markers of these two products. Less than 1h30 is required to quantify the nine studied aliphatic aldehydes in freshly distilled spirits.

  15. Effects of GC temperature and carrier gas flow rate on on-line oxygen isotope measurement as studied by on-column CO injection. (United States)

    Chen, Zhi-Gang; Yin, Xi-Jie; Zhou, Youping


    Although deemed important to δ 18 O measurement by on-line high-temperature conversion techniques, how the GC conditions affect δ 18 O measurement is rarely examined adequately. We therefore directly injected different volumes of CO or CO-N 2 mix onto the GC column by a six-port valve and examined the CO yield, CO peak shape, CO-N 2 separation, and δ 18 O value under different GC temperatures and carrier gas flow rates. The results show the CO peak area decreases when the carrier gas flow rate increases. The GC temperature has no effect on peak area. The peak width increases with the increase of CO injection volume but decreases with the increase of GC temperature and carrier gas flow rate. The peak intensity increases with the increase of GC temperature and CO injection volume but decreases with the increase of carrier gas flow rate. The peak separation time between N 2 and CO decreases with an increase of GC temperature and carrier gas flow rate. δ 18 O value decreases with the increase of CO injection volume (when half m/z 28 intensity is rate. On average, the δ 18 O value of the injected CO is about 1‰ higher than that of identical reference CO. The δ 18 O distribution pattern of the injected CO is probably a combined result of ion source nonlinearity and preferential loss of C 16 O or oxygen isotopic exchange between zeolite and CO. For practical application, a lower carrier gas flow rate is therefore recommended as it has the combined advantages of higher CO yield, better N 2 -CO separation, lower He consumption, and insignificant effect on δ 18 O value, while a higher-than-60 °C GC temperature and a larger-than-100 µl CO volume is also recommended. When no N 2 peak is expected, a higher GC temperature is recommended, and vice versa. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  16. Application of acetone acetals as water scavengers and derivatization agents prior to the gas chromatographic analysis of polar residual solvents in aqueous samples. (United States)

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


    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.

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

    International Nuclear Information System (INIS)

    Risticevic, Sanja; Carasek, Eduardo; Pawliszyn, Janusz


    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

  18. Analysis of polycyclic aromatic hydrocarbons I. Determination by gas chromatography with glass and fused silica capillary columns; Analisis de Hidrocarburos aromaticos policiclicos. I. Determinacion por cromatografia de gases con columnas capilares de vidrio de silice fundida

    Energy Technology Data Exchange (ETDEWEB)

    Perez, M. M.; Gonzalez, D.


    A study of the analysis by gas chromatography of aromatic polycyclic hydrocarbons is presented. The separation has been carried out by glass and fused silica capillary column. The limitations and the advantages of the procedure are discussed in terms of separation efficiency, sensitivity and precision. (Author) 17 refs.

  19. A Laboratory Experiment To Measure Henry's Law Constants of Volatile Organic Compounds with a Bubble Column and a Gas Chromatography Flame Ionization Detector (GC-FID) (United States)

    Lee, Shan-Hu; Mukherjee, Souptik; Brewer, Brittany; Ryan, Raphael; Yu, Huan; Gangoda, Mahinda


    An undergraduate laboratory experiment is described to measure Henry's law constants of organic compounds using a bubble column and gas chromatography flame ionization detector (GC-FID). This experiment is designed for upper-division undergraduate laboratory courses and can be implemented in conjunction with physical chemistry, analytical…

  20. Contribution of oil and natural gas production to renewed increase in atmospheric methane (2007–2014: top–down estimate from ethane and methane column observations

    Directory of Open Access Journals (Sweden)

    P. Hausmann


    Full Text Available Harmonized time series of column-averaged mole fractions of atmospheric methane and ethane over the period 1999–2014 are derived from solar Fourier transform infrared (FTIR measurements at the Zugspitze summit (47° N, 11° E; 2964 m a.s.l. and at Lauder (45° S, 170° E; 370 m a.s.l.. Long-term trend analysis reveals a consistent renewed methane increase since 2007 of 6.2 [5.6, 6.9] ppb yr−1 (parts-per-billion per year at the Zugspitze and 6.0 [5.3, 6.7] ppb yr−1 at Lauder (95 % confidence intervals. Several recent studies provide pieces of evidence that the renewed methane increase is most likely driven by two main factors: (i increased methane emissions from tropical wetlands, followed by (ii increased thermogenic methane emissions due to growing oil and natural gas production. Here, we quantify the magnitude of the second class of sources, using long-term measurements of atmospheric ethane as a tracer for thermogenic methane emissions. In 2007, after years of weak decline, the Zugspitze ethane time series shows the sudden onset of a significant positive trend (2.3 [1.8, 2.8]  ×  10−2 ppb yr−1 for 2007–2014, while a negative trend persists at Lauder after 2007 (−0.4 [−0.6, −0.1]  ×  10−2 ppb yr−1. Zugspitze methane and ethane time series are significantly correlated for the period 2007–2014 and can be assigned to thermogenic methane emissions with an ethane-to-methane ratio (EMR of 12–19 %. We present optimized emission scenarios for 2007–2014 derived from an atmospheric two-box model. From our trend observations we infer a total ethane emission increase over the period 2007–2014 from oil and natural gas sources of 1–11 Tg yr−1 along with an overall methane emission increase of 24–45 Tg yr−1. Based on these results, the oil and natural gas emission contribution (C to the renewed methane increase is deduced using three different emission scenarios with dedicated EMR ranges

  1. Large scale chromatographic separations using continuous displacement chromatography (CDC)

    International Nuclear Information System (INIS)

    Taniguchi, V.T.; Doty, A.W.; Byers, C.H.


    A process for large scale chromatographic separations using a continuous chromatography technique is described. The process combines the advantages of large scale batch fixed column displacement chromatography with conventional analytical or elution continuous annular chromatography (CAC) to enable large scale displacement chromatography to be performed on a continuous basis (CDC). Such large scale, continuous displacement chromatography separations have not been reported in the literature. The process is demonstrated with the ion exchange separation of a binary lanthanide (Nd/Pr) mixture. The process is, however, applicable to any displacement chromatography separation that can be performed using conventional batch, fixed column chromatography

  2. PULSE COLUMN (United States)

    Grimmett, E.S.


    This patent covers a continuous countercurrent liquidsolids contactor column having a number of contactor states each comprising a perforated plate, a layer of balls, and a downcomer tube; a liquid-pulsing piston; and a solids discharger formed of a conical section at the bottom of the column, and a tubular extension on the lowest downcomer terminating in the conical section. Between the conical section and the downcomer extension is formed a small annular opening, through which solids fall coming through the perforated plate of the lowest contactor stage. This annular opening is small enough that the pressure drop thereacross is greater than the pressure drop upward through the lowest contactor stage. (AEC)

  3. Interface for liquid chromatograph-mass spectrometer (United States)

    Andresen, Brian D.; Fought, Eric R.


    A moving belt interface for real-time, high-performance liquid chromatograph (HPLC)/mass spectrometer (MS) analysis which strips away the HPLC solvent as it emerges from the end of the HPLC column and leaves a residue suitable for mass-spectral analysis. The interface includes a portable, stand-alone apparatus having a plural stage vacuum station, a continuous ribbon or belt, a drive train magnetically coupled to an external drive motor, a calibrated HPLC delivery system, a heated probe tip and means located adjacent the probe tip for direct ionization of the residue on the belt. The interface is also capable of being readily adapted to fit any mass spectrometer.

  4. Fully automated dynamic in-syringe liquid-phase microextraction and on-column derivatization of carbamate pesticides with gas chromatography/mass spectrometric analysis. (United States)

    Lee, Jingyi; Lee, Hian Kee


    A new fully automated dynamic in-syringe liquid-phase microextraction (LPME) and on-column derivatization approach, with gas chromatography/mass spectrometric (GC/MS) analysis, was developed to determine carbamate pesticides from water samples. With the use of a CTC CombiPal autosampler and its associated Cycle Composer software, a sample preparation-GC/MS method was enabled that allowed sample extraction, extract injection, and analyte derivatization to be carried out completely automatically. Optimization of extraction parameters was carried out by orthogonal array design which required a minimum of 16 experiments; the entire set of experiments was performed completely automatically and consecutively without any human intervention. Low limits of detection ranging from 0.05 to 0.1 μg/L were achieved for the carbamates. Effective enrichment of the analytes at a low concentration of 0.01 mg/L was also achieved (enrichment factors of between 57 and 138). The precision of the optimized method was satisfactory, with relative standard deviations of <6.0% (n = 6). High relative recoveries of between 81 and 125% were obtained when the method was applied to the analysis of real water samples, indicating that the sample matrix had little effect on the developed method. This automated dynamic in-syringe LPME approach demonstrated the feasibility of a complete analytical system comprising sample preparation and GC/MS that might be operated onsite, fully automatically without human intervention.

  5. Determination of Wastewater Compounds in Whole Water by Continuous Liquid-Liquid Extraction and Capillary-Column Gas Chromatography/Mass Spectrometry (United States)

    Zaugg, Steven D.; Smith, Steven G.; Schroeder, Michael P.


    A method for the determination of 69 compounds typically found in domestic and industrial wastewater is described. The method was developed in response to increasing concern over the impact of endocrine-disrupting chemicals on aquatic organisms in wastewater. This method also is useful for evaluating the effects of combined sanitary and storm-sewer overflow on the water quality of urban streams. The method focuses on the determination of compounds that are indicators of wastewater or have endocrine-disrupting potential. These compounds include the alkylphenol ethoxylate nonionic surfactants, food additives, fragrances, antioxidants, flame retardants, plasticizers, industrial solvents, disinfectants, fecal sterols, polycyclic aromatic hydrocarbons, and high-use domestic pesticides. Wastewater compounds in whole-water samples were extracted using continuous liquid-liquid extractors and methylene chloride solvent, and then determined by capillary-column gas chromatography/mass spectrometry. Recoveries in reagent-water samples fortified at 0.5 microgram per liter averaged 72 percent ? 8 percent relative standard deviation. The concentration of 21 compounds is always reported as estimated because method recovery was less than 60 percent, variability was greater than 25 percent relative standard deviation, or standard reference compounds were prepared from technical mixtures. Initial method detection limits averaged 0.18 microgram per liter. Samples were preserved by adding 60 grams of sodium chloride and stored at 4 degrees Celsius. The laboratory established a sample holding-time limit prior to sample extraction of 14 days from the date of collection.

  6. Analysis of alkyl phosphates in petroleum samples by comprehensive two-dimensional gas chromatography with nitrogen phosphorus detection and post-column Deans switching. (United States)

    Nizio, Katie D; Harynuk, James J


    Alkyl phosphate based gellants used as viscosity builders for fracturing fluids used in the process of hydraulic fracturing have been implicated in numerous refinery-fouling incidents in North America. In response, industry developed an inductively coupled plasma optical emission spectroscopy (ICP-OES) based method for the analysis of total volatile phosphorus in distillate fractions of crude oil; however, this method is plagued by poor precision and a high limit of detection (0.5±1μg phosphorus mL(-1)). Furthermore this method cannot provide speciation information, which is critical for developing an understanding of the challenge of alkyl phosphates at a molecular level. An approach using comprehensive two-dimensional gas chromatography with nitrogen phosphorus detection (GC×GC-NPD) and post-column Deans switching is presented. This method provides qualitative and quantitative profiles of alkyl phosphates in industrial petroleum samples with increased precision and at levels comparable to or below those achievable by ICP-OES. A recovery study in a fracturing fluid sample and a profiling study of alkyl phosphates in four recovered fracturing fluid/crude oil mixtures (flowback) are also presented. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Verification of hydrogen isotope separation by pressure swing adsorption process: Successive volume reduction of isotopic gas mixture using SZ-5A column

    Energy Technology Data Exchange (ETDEWEB)

    Kotoh, K., E-mail: [Dept. of Applied Quantum Phys. and Nucl. Eng., Faculty of Eng., Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Tanaka, M. [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Takashima, S.; Tsuge, T. [Dept. of Applied Quantum Phys. and Nucl. Eng., Faculty of Eng., Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Asakura, Y.; Uda, T. [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Sugiyama, T. [Faculty of Eng., Nagoya University, Furo-cho, Chigusa-ku, Nagoya 464-8601 (Japan)


    For the purpose of verifying the applicability of pressure swing adsorption (PSA) process to such as volume reduction of tritiated waste storage, an experimental series was carried out by a PSA apparatus having a zeolite packed column operated at the liquefied nitrogen temperature, where synthetic zeolite 5A was used as a candidate of adsorbents. Experimental results are shown here which were obtained from cyclic operation of isolating a volume of hydrogen decontaminated with its heaver isotope from a mixture of H{sub 2} and D{sub 2} while reducing a volume of this mixture storage. Successive reduction during six cycles is observed in the inventory of this hydrogen mixture in a gas holder. Experimental data are analyzed in order to evaluate the performance of this PSA process operating the hydrogen isotope separation, where several factors are introduced defining efficiencies of decontamination, volumetric reduction, and so on. These factors suggest that the PSA process is available for successive reduction of a tritiated hydrogen storage inventory. A tritium waste management system of PSA process combined with electrolysis is considerable which is aiming at reducing the inventory of tritiated water in storage.

  8. Gas chromatographic analysis of plant sterols (United States)

    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 ...

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

    Indian Academy of Sciences (India)


    prevent this abuse and the side effects of these drugs in various countries, the urine and fluids are analysed ... samples in fishes and animals (Wright and Hunt 1982;. Young et al 1983; Kagawa et al 1984; McFarilane ... and metabolism of anabolic steroids in man or animal, although a knowledge of metabolism is necessary ...

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

    Indian Academy of Sciences (India)


    over sodium sulphate, evaporated at room temperature under nitrogen and the residues dissolved in 30–50 µl of methanol and injected. 2.4 Urine collection ... with potassium bicarbonate and extracted with 5 ml of diethylether. The residue, after evaporation of the diethyl- ether, was derivatized with 50 µl of a solution of.

  11. Column properties and flow profiles of a flat, wide column for high-pressure liquid chromatography. (United States)

    Mriziq, Khaled S; Guiochon, Georges


    The design and the construction of a pressurized, flat, wide column for high-performance liquid chromatography (HPLC) are described. This apparatus, which is derived from instruments that implement over-pressured thin layer chromatography, can carry out only uni-dimensional chromatographic separations. However, it is intended to be the first step in the development of more powerful instruments that will be able to carry out two-dimensional chromatographic separations, in which case, the first separation would be a space-based separation, LC(x), taking place along one side of the bed and the second separation would be a time-based separation, LC(t), as in classical HPLC but proceeding along the flat column, not along a tube. The apparatus described consists of a pressurization chamber made of a Plexiglas block and a column chamber made of stainless steel. These two chambers are separated by a thin Mylar membrane. The column chamber is a cavity which is filled with a thick layer (ca. 1mm) of the stationary phase. Suitable solvent inlet and outlet ports are located on two opposite sides of the sorbent layer. The design allows the preparation of a homogenous sorbent layer suitable to be used as a chromatographic column, the achievement of effective seals of the stationary phase layer against the chamber edges, and the homogenous flow of the mobile phase along the chamber. The entire width of the sorbent layer area can be used to develop separations or elute samples. The reproducible performance of the apparatus is demonstrated by the chromatographic separations of different dyes. This instrument is essentially designed for testing detector arrays to be used in a two-dimensional LC(x) x LC(t) instrument. The further development of two-dimension separation chromatographs based on the apparatus described is sketched.

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

    International Nuclear Information System (INIS)

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


    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. Determination of solute descriptors by chromatographic methods. (United States)

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


    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.

  14. Determination of solute descriptors by chromatographic methods

    International Nuclear Information System (INIS)

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


    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 Wastewater Compounds in Sediment and Soil by Pressurized Solvent Extraction, Solid-Phase Extraction, and Capillary-Column Gas Chromatography/Mass Spectrometry (United States)

    Burkhardt, Mark R.; Zaugg, Steven D.; Smith, Steven G.; ReVello, Rhiannon C.


    A method for the determination of 61 compounds in environmental sediment and soil samples is described. The method was developed in response to increasing concern over the effects of endocrine-disrupting chemicals in wastewater and wastewater-impacted sediment on aquatic organisms. This method also may be used to evaluate the effects of combined sanitary and storm-sewer overflow on the water and sediment quality of urban streams. Method development focused on the determination of compounds that were chosen on the basis of their endocrine-disrupting potential or toxicity. These compounds include the alkylphenol ethoxylate nonionic surfactants and their degradates, food additives, fragrances, antioxidants, flame retardants, plasticizers, industrial solvents, disinfectants, fecal sterols, polycyclic aromatic hydrocarbons, and high-use domestic pesticides. Sediment and soil samples are extracted using a pressurized solvent extraction system. The compounds of interest are extracted from interfering matrix components by high-pressure water/isopropyl alcohol extraction. The compounds were isolated using disposable solid-phase extraction (SPE) cartridges containing chemically modified polystyrene-divinylbenzene resin. The cartridges were dried with nitrogen gas, and then sorbed compounds were eluted with methylene chloride (80 percent)-diethyl ether (20 percent) through Florisil/sodium sulfate SPE cartridge, and then determined by capillary-column gas chromatography/mass spectrometry. Recoveries in reagent-sand samples fortified at 4 to 72 micrograms averaged 76 percent ?13 percent relative standard deviation for all method compounds. Initial method reporting levels for single-component compounds ranged from 50 to 500 micrograms per kilogram. The concentrations of 20 out of 61 compounds initially will be reported as estimated with the 'E' remark code for one of three reasons: (1) unacceptably low-biased recovery (less than 60 percent) or highly variable method performance

  16. Determination of low concentrations of pyridine in piperidine by gas chromatography and infrared spectroscopy

    International Nuclear Information System (INIS)

    Perez Garcia, M. M.; Parellada Bellod, R.


    This paper describes the determination of low amounts of piperidine in pyridine in the concentration range of 0-5%. After an exhausting review of the bibliography on the column selection, the chromatographic separation and determination are made on the following column: 27% Pennwalt- 223; 4% KOH on Gas-Chrom R; 80-100 mesh with flame ionization detector. The retention indexes of both compounds and tho Rohrschneider constants of the phase used are calculated. The minimum detection limit achieved for piperidine is 0,25%. (Author) 25 refs

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

    NARCIS (Netherlands)

    Hulshoff, A.; Lingeman, H.


    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

  18. Retention Study of Flavonoids Under Different Chromatographic Modes. (United States)

    Sentkowska, Aleksandra; Biesaga, Magdalena; Pyrzynska, Krystyna


    The goal of this study was to investigate the chromatographic behavior of selected flavonoids from their different subgroups (flavonols, flavanones, flavones and isoflavones) in hydrophilic interaction liquid chromatography (HILIC). Chromatographic measurements were made on two different HILIC columns: cross-linked DIOL (Luna HILIC) and zwitterionic sulfoalkylbetaine (SeQuant ZIC-HILIC). Separation parameters such as the content of acetonitrile and pH of an eluent were studied. On the ZIC column, the retention factors of flavonoids increased with decreasing water content in the mobile phase. The increase in pH of the aqueous component mainly affects the polarity of the analytes. DIOL stationary phase shows more or less apparent dual retention mechanism, HILIC at the acetonitrile (ACN) content ≥75% and reversed phase (RP) with lower content of organic modifier. In the presence of ammonium acetate in the mobile phase, the retention of flavonoids onto the DIOL column increases without change in the selectivity of the separations. The similar effect, but considerably smaller was observed for aglycones on the ZIC column. The retention of studied glycosides (hesperidin, rutin) decreases in the presence of salt in the mobile phase. The significantly higher mass spectrometry sensitivity was observed under HILIC conditions in comparison with the most often used RP LC due to much higher content of ACN in the mobile phase. Finally, under optimal chromatographic conditions, the method was validated and applied for the determination of flavonoids in chamomile (Matricaria chamomilla L.) infusion. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email:

  19. nduced hyperlipidemic rats. Methods: Column chromatographic fractionation of butanol fraction of total methanol extract of leaves of Bauhinia variegata (Linn. yields four sub-fractions (sub-fraction A-D. All sub-fractions tested for their anti-hyperlipidemic activity. Sub-fractions administered at a dose of 65 mg/kg (oral to the Triton WR-1339 induced hyperlipidemic rats and total cholesterol, triglycerides, HDL, LDL and VLDL

    Directory of Open Access Journals (Sweden)

    Deepak Kumar


    Full Text Available Objective: To investigate the effect and evaluation of Anti-hyperlipidemic activity guided subfraction isolated from total methanolic extract of Bauhinia variegata (Linn. leaves on Triton WR-1339 induced hyperlipidemic rats. Methods: Column chromatographic fractionation of butanol fraction of total methanol extract of leaves of Bauhinia variegata (Linn. yields four subfractions (sub-fraction A-D. All sub-fractions tested for their anti-hyperlipidemic activity. Subfractions administered at a dose of 65 mg/kg (oral to the Triton WR-1339 induced hyperlipidemic rats and total cholesterol, triglycerides, HDL, LDL and VLDL level in the blood were checked. Results: Sub-fraction D showed significant reduction (P<0.05 among four sub-fraction in comparison with standard drug fenofibrate. Conclusions: From the above study it could be concluded that butanol sub-fraction D of Bauhinia variegata (Linn. not only have resulted in significant reduction in cholesterol, triglyceride, LDL, VLDL level but also increases the HDL level at a reduced dose level.

  20. Studies on the separation of hydrogen isotopes and spin isomers by gas chromatography

    International Nuclear Information System (INIS)

    Pushpa, K.K.; Annaji Rao, K.


    Separation and analysis of mixture of hydrogen isotopes has gained considerable importance because of various applications needing different isotopes in lasers, nuclear reactions and tracer or labelled compounds. In the literature gas chromatographic methods are reported using columns packed with partly dehydrated or thoroughly dehydrated alumina/molecular sieve stationary phase at 77 deg K with helium, neon and even hydrogen or deuterium as carrier gas. In the present study an attempt is made to compare the chromatographic behaviour of these two stationary phases using virgin and Fe doped form in partly dehydrated and thoroughly dehydrated state, using helium, neon, hydrogen and deuterium as carrier gas. The results of this study show that helium or neon carrier gas behave similarly broad peaks with some tailing. Sharp symmetric peaks are obtained with hydrogen or deuterium carrier gas. This is attributed to large hold up capacity for H 2 or D 2 at 77 deg K in these materials as compared to helium or neon. Spin isomers of H 2 or D 2 are separated on Fe free stationary phases, though ortho H 2 and HD are not resolved. Using a combination of Fe doped short column and plain alumina column, both maintained in dehydrated form, the effect of Fe doping on thermal equilibrium of ortho/para forms at 77 deg K is clearly demonstrated. (author)

  1. Column: Every Last Byte

    Directory of Open Access Journals (Sweden)

    Simson Garfinkel


    Full Text Available Inheritance powder is the name that was given to poisons, especially arsenic, that were commonly used in the 17th and early 18th centuries to hasten the death of the elderly. For most of the 17th century, arsenic was deadly but undetectable, making it nearly impossible to prove that someone had been poisoned. The first arsenic test produced a gas—hardly something that a scientist could show to a judge. Faced with a growing epidemic of poisonings, doctors and chemists spent decades searching for something better.(see PDF for full column

  2. Chromatographic Separations of Enantiomers and Underivatized Oligosaccharides

    International Nuclear Information System (INIS)

    Ying Liu


    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

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ying [Iowa State Univ., Ames, IA (United States)


    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. Column Selection for Biomedical Analysis Supported by Column Classification Based on Four Test Parameters. (United States)

    Plenis, Alina; Rekowska, Natalia; Bączek, Tomasz


    This article focuses on correlating the column classification obtained from the method created at the Katholieke Universiteit Leuven (KUL), with the chromatographic resolution attained in biomedical separation. In the KUL system, each column is described with four parameters, which enables estimation of the FKUL value characterising similarity of those parameters to the selected reference stationary phase. Thus, a ranking list based on the FKUL value can be calculated for the chosen reference column, then correlated with the results of the column performance test. In this study, the column performance test was based on analysis of moclobemide and its two metabolites in human plasma by liquid chromatography (LC), using 18 columns. The comparative study was performed using traditional correlation of the FKUL values with the retention parameters of the analytes describing the column performance test. In order to deepen the comparative assessment of both data sets, factor analysis (FA) was also used. The obtained results indicated that the stationary phase classes, closely related according to the KUL method, yielded comparable separation for the target substances. Therefore, the column ranking system based on the FKUL-values could be considered supportive in the choice of the appropriate column for biomedical analysis.

  5. Application of gas-liquid chromatography and high-performance liquid chromatography to the analysis of trace amounts of salicylic acid, acetylsalicylic anhydride and acetylsalicylsalicylic acid in aspirin samples and aspirin formulations. (United States)

    Ali, S L


    The gas-liquid chromatographic (GLC) determination of salicylic acid (SA) in 12 commercial acetylsalicylic acid (aspirin, ASA) samples and 12 ASA formulations is reported. The GLC determination of SA as an impurity in ASA, utilising methylation with methyl iodide in the presence of potassium carbonate, requires a column chromatographic separation of SA prior to derivatization. Trace amounts of SA in ASA have also been determined by high-performance liquid chromatography (HPLC) on a Sil-X-I adsorption column using light petroleum-ethyl acetate-acetic acid as the mobile phase. Acetylsalicylic anhydride (ASN) and acetylsalicylsalicylic acid (ASSA) were determined by HPLC on a reversed-phase C18 column with water-methanol mixtures as the mobile phase. GLC was also applied to the determination of ASN as an impurity in ASA formulations.

  6. Iterative trapping of gaseous volatile organic compounds in a capillary column. (United States)

    Ghosh, Abhijit; Seeley, Stacy K; Seeley, John V


    The iterative trapping method has been developed for concentrating gaseous volatile organic compounds (VOCs) prior to gas chromatographic analysis. VOCs are trapped in a 50 cm × 0.53 mm metal capillary column coated with a 7 μm thick film of polydimethylsiloxane (PDMS). Iterative trapping does not employ the two-step thermal desorption approach used by most VOC concentrating techniques. Instead, a four-step cycle involving synchronized changes in flow direction and temperature is repeated throughout the sampling process. This iterative process causes VOCs to accumulate within the capillary well past the level where a standard two-step method reaches its saturation limit. Iterative trapping is capable of sampling and desorbing C5 through C11 n-alkanes with uniform efficiency. This new technique, in its current form, is most appropriate for focusing VOCs from gas volumes on the order of 10 mL. Iterative trapping increases the focusing power of a weak sorbent like PDMS and allows narrow chromatographic peaks to be generated without the use of high desorption temperatures or a secondary focusing stage.

  7. Applications of monolithic silica capillary columns in proteomics

    NARCIS (Netherlands)

    Barroso, B.; Lubda, D; Bischoff, Rainer


    The use and applicability of silica based capillary monolithic reversed-phase columns in proteomic analysis has been evaluated by liquid chromatography-mass spectrometry (LC-MS). Chromatographic performance of the monolithic capillaries was evaluated with a tryptic digest of cytochrome C showing

  8. Monolithic and Small Particle Column Materials for Application in Proteomics

    NARCIS (Netherlands)

    Rozenbrand, J.


    In this thesis the influence of the capillary liquid chromatography separation on the identification of protein digests is studied. In the first part the chromatographic parameters for silica monolithic columns are optimized to obtain a high throughput or a high separation performance. in the second

  9. Chemical stability of enalapril maleate drug substance and tablets by a stability-indicating liquid chromatographic method


    Diego,Marta de; Godoy,Gloria; Mennickent,Sigrid; Godoy,Ricardo


    The chemical stability of enalapril drug substance and tablets was studied by a stability-indicating liquid chromatographic method. Stress testing was performed on drug substance under various conditions. Accelerated stability testing was carried out for different formulations of enalapril tablets. Chromatographic separation was achieved on a RP-18 column, using a mobile phase of methanol phosphate buffer at 1.0 mL min"1 and UV detection. Degradation of the drug substance was greater under hy...

  10. Revising Reverse-Phase Chromatographic Behavior for Efficient Differentiation of Both Positional and Geometrical Isomers of Dicaffeoylquinic Acids

    Directory of Open Access Journals (Sweden)

    Keabetswe Masike


    Full Text Available Dicaffeoylquinic acids (diCQAs are plant metabolites and undergo trans-cis-isomerization when exposed to UV irradiation. As such, diCQAs exist in both trans- and cis-configurations and amplify the already complex plant metabolome. However, analytical differentiation of these geometrical isomers using mass spectrometry (MS approaches has proven to be extremely challenging. Exploring the chromatographic space to develop possible conditions that would aid in differentially separating and determining the elution order of these isomers is therefore imperative. In this study, simple chromatographic parameters, such as column chemistry (phenyl versus alkyl, mobile phase composition (methanol or acetonitrile, and column temperature, were investigated to aid in the separation of diCQA geometrical isomers. The high-performance liquid chromatography photodiode array (HPLC-PDA chromatograms revealed four isomers post UV irradiation of diCQA authentic standards. The elution profile/order was seen to vary on different reverse-phase column chemistries (phenyl versus alkyl using different mobile phase composition. Here, the elution profile/order on the phenyl-derived column matrices (with methanol as the mobile phase composition was observed to be relatively reproducible as compared to the alkyl (C18 columns. Chromatographic resolution of diCQA geometrical isomers can be enhanced with an increase in column temperature. Lastly, the study highlights that chromatographic elution order/profile cannot be relied upon to fathom the complexity of isomeric plant metabolites.

  11. [Application of gas chromatography in the identification of Enterobacter cloacae, Enterobacter aerogenes, and Enterobacter agglomerans]. (United States)

    Robles Valderrama, E; Ramírez García, P; González Arreaga, M E; Sáinz Morales, M G; Martínez Rodríguez, B; Durán Díaz, A; Chávez Ramírez, D


    Enterobacter cloacae, Enterobacter aerogenes and Enterobacter agglomerans were identified using gas chromatography as a substitution of the traditional techniques. Their acid methyl esters profiles were determined using a gas chromatograph Hewlett Packard 5890A and a RSL-150 heliflex capillary column. A total of 120 samples were analyzed from reference strains (ATCC 13047, 13048, 27155) and environmental isolations, eleven fatty acids were included in the profiles from which cis-9, 10-methyleneoctadecanoic acid (peak 24), cis-9-hexadecenoic acid (peak 14), octadecanoic acid (peak 23) and dodecanoic acid (peak 3), were the most important for the differentiation of the three species analyzed.

  12. Liquid chromatographic determination of tetracycline residues in animal feeds. (United States)

    Martinez, E E; Shimoda, W


    A liquid chromatographic method for the multiresidue determination of tetracyclines (TCs) in feeds is described. The levels of quantitation were 10 ppm each for tetracycline-HCl (TC), oxytetracycline (OTC), and chlortetracycline-HCl (CTC); the detection limit was 40 ppb for each. The calibration curves were linear between 2.5 and 100 ppm. The procedure involved double extraction with pH 2.0 and pH 4.5 McIlvain buffers, cleanup on a Sephadex LH-20 column, separation on a Nova-Pak C18 column, and detection at 370 nm. Recoveries of 10 micrograms/g of each TC in multiresidue feed samples ranged from 55.8 to 75.5% for OTC, 71.6 to 100% for TC, and 22.4 to 60.6% for CTC. The identities of the TCs were confirmed by thin layer chromatography.

  13. Characterization of cis- and trans-octadecenoic acid positional isomers in edible fat and oil using gas chromatography-flame ionisation detector equipped with highly polar ionic liquid capillary column. (United States)

    Yoshinaga, Kazuaki; Asanuma, Masaharu; Mizobe, Hoyo; Kojima, Koichi; Nagai, Toshiharu; Beppu, Fumiaki; Gotoh, Naohiro


    In this study, the characterisation of all cis- and trans-octadecenoic acid (C18:1) positional isomers in partially hydrogenated vegetable oil (PHVO) and milk fat, which contain several cis- and trans-C18:1 positional isomers, was achieved by gas chromatography-flame ionisation detector equipped with a highly polar ionic liquid capillary column (SLB-IL111). Prior to analysis, the cis- and trans-C18:1 fractions in PHVO and milk fat were separated using a silver-ion cartridge. The resolution of all cis-C18:1 positional isomers was successfully accomplished at the optimal isothermal column temperature of 120 °C. Similarly, the positional isomers of trans-C18:1, except for trans-6-C18:1 and trans-7-C18:1, were separated at 120 °C. The resolution of trans-6-C18:1 and trans-7-C18:1 isomers was made possible by increasing the column temperature to 160 °C. This analytical method is suitable for determining the cis- and trans-C18:1 positional isomers in edible fats and oils. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. 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

    DEFF Research Database (Denmark)

    Mistarz, Ulrik Hvid; Brown, Jeffery M; Haselmann, Kim F


    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...... 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...

  15. The setup of an extraction system coupled to a hydrogen isotopes distillation column

    International Nuclear Information System (INIS)

    Zamfirache, M.; Bornea, A.; Stefanescu, I.; Bidica, N.; Balteanu, O.; Bucur, C.


    Among the most difficult problems of cryogenic distillation one stands apart: the extraction of the heavy fraction. By an optimal design of the cycle scheme, this problem could be avoided. A 'worst case scenario' is usually occurring when the extracted fraction consists of one prevalent isotope such as hydrogen and small amounts of the other two hydrogen isotopes (deuterium and/or tritium). This situation is further complicated by two parameters of the distillation column: the extraction flow rate and the hold-up. The present work proposes the conceptual design of an extraction system associated to the cryogenic distillation column used in hydrogen separation processes. During this process, the heavy fraction (DT, T 2 ) is separated, its concentration being the highest at the bottom of the distillation column. From this place the extraction of the gaseous phase can now begin. Being filled with adsorbent, the extraction system is used to temporarily store the heavy fraction. Also the extraction system provides samples for the gas Chromatograph. The research work is focused on the existent pilot plant for tritium and deuterium separation from our institute to validate the experiments carried out until now. (authors)

  16. Towards point of care testing for C. difficile infection by volatile profiling, using the combination of a short multi-capillary gas chromatography column with metal oxide sensor detection

    International Nuclear Information System (INIS)

    McGuire, N D; Ewen, R J; De Lacy Costello, B; Garner, C E; Vaughan, K; Ratcliffe, N M; Probert, C S J


    Rapid volatile profiling of stool sample headspace was achieved using a combination of short multi-capillary chromatography column (SMCC), highly sensitive heated metal oxide semiconductor sensor and artificial neural network software. For direct analysis of biological samples this prototype offers alternatives to conventional gas chromatography (GC) detectors and electronic nose technology. The performance was compared to an identical instrument incorporating a long single capillary column (LSCC). The ability of the prototypes to separate complex mixtures was assessed using gas standards and homogenized in house ‘standard’ stool samples, with both capable of detecting more than 24 peaks per sample. The elution time was considerably faster with the SMCC resulting in a run time of 10 min compared to 30 min for the LSCC. The diagnostic potential of the prototypes was assessed using 50 C. difficile positive and 50 negative samples. The prototypes demonstrated similar capability of discriminating between positive and negative samples with sensitivity and specificity of 85% and 80% respectively. C. difficile is an important cause of hospital acquired diarrhoea, with significant morbidity and mortality around the world. A device capable of rapidly diagnosing the disease at the point of care would reduce cases, deaths and financial burden. (paper)

  17. Vibrational Spectroscopy of Chromatographic Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jeanne E. Pemberton


    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.

  18. Spatial and Temporal Variability of Trace Gas Columns Derived from WRF/Chem Regional Model Output: Planning for Geostationary Observations of Atmospheric Composition (United States)

    Follette-Cook, M. B.; Pickering, K.; Crawford, J.; Duncan, B.; Loughner, C.; Diskin, G.; Fried, A.; Weinheimer, A.


    We quantify both the spatial and temporal variability of column integrated O3, NO2, CO, SO2, and HCHO over the Baltimore / Washington, DC area using output from the Weather Research and Forecasting model with on-line chemistry (WRF/Chem) for the entire month of July 2011, coinciding with the first deployment of the NASA Earth Venture program mission Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ). Using structure function analyses, we find that the model reproduces the spatial variability observed during the campaign reasonably well, especially for O3. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument will be the first NASA mission to make atmospheric composition observations from geostationary orbit and partially fulfills the goals of the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission. We relate the simulated variability to the precision requirements defined by the science traceability matrices of these space-borne missions. Results for O3 from 0- 2 km altitude indicate that the TEMPO instrument would be able to observe O3 air quality events over the Mid-Atlantic area, even on days when the violations of the air quality standard are not widespread. The results further indicated that horizontal gradients in CO from 0-2 km would be observable over moderate distances (= 20 km). The spatial and temporal results for tropospheric column NO2 indicate that TEMPO would be able to observe not only the large urban plumes at times of peak production, but also the weaker gradients between rush hours. This suggests that the proposed spatial and temporal resolutions for these satellites as well as their prospective precision requirements are sufficient to answer the science questions they are tasked to address.

  19. Thermally stable dexsil-400 glass capillary columns

    International Nuclear Information System (INIS)

    Maskarinec, M.P.; Olerich, G.


    The factors affecting efficiency, thermal stability, and reproducibility of Dexsil-400 glass capillary columns for gas chromatography in general, and for polycyclic aromatic hydrocarbons (PAHs) in particular were investigated. Columns were drawn from Kimble KG-6 (soda-lime) glass or Kimox (borosilicate) glass. All silylation was carried out at 200 0 C. Columns were coated according to the static method. Freshly prepared, degassed solutions of Dexsil-400 in pentane or methylene chloride were used. Thermal stability of the Dexsil 400 columns with respect to gas chromatography/mass spectrometry (GC/MS) were tested. Column-to-column variability is a function of each step in the fabrication of the columns. The degree of etching, extent of silylation, and stationary phase film thickness must be carefully controlled. The variability in two Dexsil-400 capillary column prepared by etching, silylation with solution of hexa methyl disilazone (HMDS), and static coating is shown and also indicates the excellent selectivity of Dexsil-400 for the separation of alkylated aromatic compounds. The wide temperature range of Dexsil-400 and the high efficiency of the capillary columns also allow the analysis of complex mixtures with minimal prefractionation. Direct injection of a coal liquefaction product is given. Analysis by GC/MS indicated the presence of parent PAHs, alkylated PAHs, nitrogen and sulfur heterocycles, and their alkylated derivatives. 4 figures

  20. P61-S Multidimensional Liquid Chromatography of Proteins Using Monolithic Weak Anion Exchange and Reversed-Phase Columns


    Sneekes, E.; van Ling, R.; de Haan, B.; Dolman, B.; Swart, R.; van Gils, M.


    Recent developments in monolithic column technology have yielded significant improvements in the biopolymer analysis field. Monolithic columns offer several advantages over particulate columns due to their macroporous structure, which provides fast mass transfer, low back pressure and high resolution. Polystyrene divinylbenzene (PS-DVB) monolithic columns are chemically inert; they offer high pH stability and excellent chromatographic performance in reversed-phase LC. While the application of...

  1. Research into the group composition of tar using the gas liquid chromatography method

    Energy Technology Data Exchange (ETDEWEB)

    Lisin, S.N.; Stepanov, Yu.V.; Lisina, L.A.; Chistyakov, A.N.


    This paper first gives a brief review of current methods used for determining chemical composition of tars, then describes experiments using gas liquid chromatography (GLC) to determine the chemical composition of delta/sub 1/, delta/sub 2/, delta, and delta fractions of medium temperature tars obtained during normal solvent processing (isooctane, toluene, quinoline). For delta and delta fractions, a Tsvet-104 chromatograph was used with a flame-ionization detector under the following conditions: column height 3 m, diameter 3 mm, AW-HMDS filler, 0.25-0.36 mm fractions with 5% SE-30, linear column temperature increase from 50-310/sup 0/C, velocity 6 C/min, condenser temperature 350/sup 0/C, velocity of carrier gas (helium) and hydrogen 100 ml/min, air consumption 1.5 l/min. delta/sub 1/ and delta/sub 2/ fractions were determined using a GC-IC chromatograph (manufactured by Shimatsu) under conditions analogous to those given above. Conclusion is that the yield of chromatographable compounds from tar by the GLC method with temperature programming is practically constant for each tar and can be characterized by the delta fraction content and its chemical composition. A method of determining the group composition of tars and the chemical composition of the delta fraction using GLC is proposed. 13 refs.

  2. An analytical study by gas liquid chromatography and radiochromatography of tritium labelled lebaycid; Estudio Analitico del proceso de sistesis del lebaycid marcado contritio por cromatogria gas liquido y radiocromatografia

    Energy Technology Data Exchange (ETDEWEB)

    Perez Garcia, M. M.


    The stability and purity of the syntheses products of Lebaycid: 0,0 dime thylfosfochlorothionate and 4 methyl-thio-m-cresol were investigated by gas liquid chromatography. The study on (CH{sub 3}O){sub 2} PSC1 was made in a column of Silicone SE-30, Reoplex 400 using a thermal conductivity detector. The 99,4% pure product obtained from the preparative gas chromatograph was found to be stable within the duration of the experiment: seven months. (Author) 23 refs.

  3. Preparation of fused-silica columns with phases immobilized by cobalt-60 gamma radiation; application to essential oil analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hubball, J.A.


    Cobalt-60 gamma-radiation was used to immobilize polymeric stationary phases in fused silica capillary columns for gas chromatography. Surface studies of the uncoated fused silica tubing by optical and scanning electron microscopy indicated some irregularities, but overall the tubing maintained its strength and flexibility at dosages up to 25 MRads. A polydimethylsiloxane phase (OV-1) and a polyethylene glycol phase (Carbowax 20 M) were effectively immobilized on the inner surface of fused silica capillary tubing without altering the properties of the phases. The optimum radiation dosage for OV-1 was 7 MRads, while Carbowax 20 M required 25 MRads to immobilize 33% of the coated layer. Fused silica capillary columns prepared with both phases were evaluated for deactivation, efficiency, and thermal stability. Immobilization of Carbowax 20 M extended the low and high temperature limits by 30 C in each direction. Columns prepared in this study were used to analyze the essential oil of Siparuna guianensis. Several key components of the oil were identified by GC/MS and gas chromatographic techniques.

  4. Procedures for the production of poly-zirconium-compound (PZC) based chromatographic 99mTc generator to be available for clinical application

    International Nuclear Information System (INIS)

    Le Van So


    Two procedures - Column post-loading and Column pre-loading procedures - for the preparation of PZC based chromatographic Tc-99m generators were described in detail. In-process documentation, flow-chart of process for the individual procedures, specific Tc-99m generator designs and pictorially illustrative description of Tc-99m generator production process were systematically reported. The column pre-loading procedure was highly evaluated as a competent technology for the preparation of PZC based Tc-99m chromatographic generator of high performance using (n, γ) 99 Mo of low specific radioactivity produced on low power research reactors. (author)

  5. Programmed temperature vaporizing injector to filter off disturbing high boiling and involatile material for on-line high performance liquid chromatography gas chromatography with on-column transfer. (United States)

    Biedermann, Maurus; Grob, Koni


    Insertion of a programmed temperature vaporizing (PTV) injector under conditions of concurrent solvent recondensation (CSR) into the on-line HPLC-GC interface for on-column transfer (such as the retention gap technique with partially concurrent eluent evaporation) enables filtering off high boiling or involatile sample constituents by a desorption temperature adjusted to the required cut-off. Details of this technique were investigated and optimized. Memory effects, observed when transferred liquid was sucked backwards between the transfer line and the wall of the injector liner, can be kept low by a small purge flow rate through the transfer line at the end of the transfer and the release of the liquid through a narrow bore capillary kept away from the liner wall. The column entrance should be within the well heated zone of the injector to prevent losses of solute material retained on the liner wall during the splitless period. The desorption temperature must be maintained until an elevated oven temperature is reached to prevent peak broadening resulting of a cool inlet section in the bottom part of the injector. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Applications of silica-based monolithic HPLC columns. (United States)

    Cabrera, Karin


    The recent invention and successive commercial introduction of monolithic silica columns has motivated many scientists from both academia and industry to study their use in HPLC. The first paper on monolithic silica columns appeared in 1996. Currently about 200 papers have been published relating to applications and characterization of monolithic silica columns, including monolithic capillaries. This review attempts to give an overview covering various aspects of this new column type in the field of high throughput analysis of drugs and metabolites, chiral separations, analysis of pollutants and food-relevant compounds, as well as in bioanalytical separations such as in proteomics. Some of the applications are described in greater detail. The numerous publications dealing with the physicochemical and chromatographic characterization of monolithic silica columns are briefly summarized.

  7. Chromatographic 188W →188Re generator

    International Nuclear Information System (INIS)

    Khujaev, S.


    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

  8. Mechanistic model for dispersion coefficients in bubble column

    CSIR Research Space (South Africa)

    Skosana, PJ


    Full Text Available A mechanistic model describing the mass and momentum exchange in bubble columns is proposed that is based on the observations that the gas distribution in a bubble column is not uniform across the column and that as a consequence large liquid...


    NARCIS (Netherlands)



    A column-switching high-performance liquid chromatographic method was developed for the determination of vincristine in serum. Sample preparation was carried out by means of on-line column-extraction, using a C18 reversed-phase preconcentration column. This technique is simple (minimizing manual

  10. Improved separation and quantification of dioxin and furan congeners using novel low-bleed capillary gas chromatography columns and mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Dorman, F. [Restek Corporation, Bellefonte, PA (United States); Reese, S. [Folsom Lake College, Folsom, CA (United States); Reiner, E.; MacPherson, K. [Ontario Ministry of the Environment, Ottawa, Ontario (Canada); Focant, J. [Liege Univ. (Belgium); Cochran, J. [LECO Corporation, St. Josephs, MI (United States)


    This presentation will address the development of two new stationary phase chemistries that allow for improved separation of the toxic dioxin and furan congeners. Using conventional high-resolution mass spectrometry, it is possible to separate all of the congeners of interest in a single analysis on one column. Quantitation values from standard reference materials, fly ash, and previously characterized samples will be shown as evidence of how this separation is faster and more accurate than has previously been available. Finally results from comprehensive two-dimensional GC coupled to time-of-flight MS will be shown to demonstrate how this technique can rival the high-resolution method in terms of quality of information.

  11. On the use of ionic liquid capillary columns for analysis of aromatic hydrocarbons in low-boiling petrochemical products by one-dimensional and comprehensive two-dimensional gas chromatography. (United States)

    Krupčík, Ján; Gorovenko, Roman; Špánik, Ivan; Bočková, Ingrid; Sandra, Pat; Armstrong, Daniel W


    One-dimensional and comprehensive two-dimensional flow modulated gas chromatography with simultaneous flame ionization and mass spectrometric detection were applied for the identification and quantification of benzene, toluene, ethyl benzene and xylenes (BTEX) as well as of all C9-C11 aromatic hydrocarbons in the low-boiling petroleum products gasoline, reformate and fluid catalytic cracking (FCC) samples. GC×GC experiments were performed on two reversed phase polarity column sets namely SLB-IL100 (25m×250μm i.d.×0.2μm df)+HP-5MS (5m×250μm i.d.×0.25μm df) and SLB-IL111 (30m×250μm i.d.×0.2μm df)+HP-5MS (5m×250μm i.d.×0.25μm df). The one-dimensional GC experiments were carried out on the same ionic liquid columns. The most powerful method is GC×GC on the SLB-111+HP-5MS column combination. Quantitative analysis of individual aromatic hydrocarbons (C6-C11) present in gasoline, reformate and fluid catalytic cracking (FCC) samples was performed by GC×GC-FID using the internal normalization method. Mass spectra obtained by GC×GC-qMSD were used for identification of the aromatic hydrocarbons in these samples. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Determination of low concentrations of pyridine in piperidine by gas chromatography and infrared spectroscopy; Determinacion de bajas concentraciones de piperidina en piridina por cromatografia de gases y espectroscopia infrarroja

    Energy Technology Data Exchange (ETDEWEB)

    Perez Garcia, M. M.; Parellada Bellod, R.


    This paper describes the determination of low amounts of piperidine in pyridine in the concentration range of 0-5%. After an exhausting review of the bibliography on the column selection, the chromatographic separation and determination are made on the following column: 27% Pennwalt- 223; 4% KOH on Gas-Chrom R; 80-100 mesh with flame ionization detector. The retention indexes of both compounds and tho Rohrschneider constants of the phase used are calculated. The minimum detection limit achieved for piperidine is 0,25%. (Author) 25 refs.

  13. Determination of Low Concentrations of Acetochlor in Water by Automated Solid-Phase Extraction and Gas Chromatography with Mass-Selective Detection (United States)

    Lindley, C.E.; Stewart, J.T.; Sandstrom, M.W.


    A sensitive and reliable gas chromatographic/mass spectrometric (GC/MS) method for determining acetochlor in environmental water samples was developed. The method involves automated extraction of the herbicide from a filtered 1 L water sample through a C18 solid-phase extraction column, elution from the column with hexane-isopropyl alcohol (3 + 1), and concentration of the extract with nitrogen gas. The herbicide is quantitated by capillary/column GC/MS with selected-ion monitoring of 3 characteristic ions. The single-operator method detection limit for reagent water samples is 0.0015 ??g/L. Mean recoveries ranged from about 92 to 115% for 3 water matrixes fortified at 0.05 and 0.5 ??g/L. Average single-operator precision, over the course of 1 week, was better than 5%.

  14. Chromatographic Techniques for Rare Earth Elements Analysis (United States)

    Chen, Beibei; He, Man; Zhang, Huashan; Jiang, Zucheng; Hu, Bin


    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.

  15. Modeling Stone Columns. (United States)

    Castro, Jorge


    This paper reviews the main modeling techniques for stone columns, both ordinary stone columns and geosynthetic-encased stone columns. The paper tries to encompass the more recent advances and recommendations in the topic. Regarding the geometrical model, the main options are the "unit cell", longitudinal gravel trenches in plane strain conditions, cylindrical rings of gravel in axial symmetry conditions, equivalent homogeneous soil with improved properties and three-dimensional models, either a full three-dimensional model or just a three-dimensional row or slice of columns. Some guidelines for obtaining these simplified geometrical models are provided and the particular case of groups of columns under footings is also analyzed. For the latter case, there is a column critical length that is around twice the footing width for non-encased columns in a homogeneous soft soil. In the literature, the column critical length is sometimes given as a function of the column length, which leads to some disparities in its value. Here it is shown that the column critical length mainly depends on the footing dimensions. Some other features related with column modeling are also briefly presented, such as the influence of column installation. Finally, some guidance and recommendations are provided on parameter selection for the study of stone columns.


    This paper summarizes the key points of a joint study between the EPA and Metrohm-Peak, Inc., on the use of polyvinyl alcohol [PVA] columns for the ion chromatographic determination of percholorate in aqueous leachates or solutions of fertilizers. A series of fertilizer samples ...

  17. Equipment for automatic measurement of gamma activity distribution in a column

    International Nuclear Information System (INIS)

    Kalincak, M.; Machan, V.; Vilcek, S.; Balkovsky, K.


    The design of a device for stepwise scanning of gamma activity distributions along chromatographic columns is described. In connection with a single-channel gamma spectrometer and a counting ratemeter with a recorder this device permits the resolution of a number of gamma emitters on the column, the determination of the gamma nuclide content in different chemical forms in the sample by means of column separation methods - Gel Chromatography Columns Scanning Method - and the determination of gamma nuclide distribution along the columns. The device permits the scanning of columns of up to 20 mm in diameter and 700 mm in length and continual scanning over a 450 mm column length with one clamping. With minor adaptations it is possible to scan columns up to 30 mm in diameter. The length of the scanned sections is 5 or 10 mm, the scanning time setting is arbitrary and variable activity levels and radiation energies may be measured. (author)

  18. ( Anogeissus leiocarpus ) timber columns

    African Journals Online (AJOL)

    A procedure for designing axially loaded Ayin (Anogeissus leiocarpus) wood column or strut has been investigated. Instead of the usual categorization of columns into short, intermediate and slender according to the value of slenderness ratio, a continuous column formula representing the three categories was derived.

  19. Gas

    International Nuclear Information System (INIS)


    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

  20. Determination of D- and L-Amino Acids in Biological Samples by Two Dimensional Column Liquid Chromatography.

    NARCIS (Netherlands)

    van de Merbel, N.C.; Lingeman, H.; Brinkman, U.A.T.; Stenberg, M.; Oste, R.; Marko-Varga, G.; Gorton, L.


    A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citrate-sodium chloride buffer. Enantioseparation is

  1. Modeling Aquatic Toxicity through Chromatographic Systems. (United States)

    Fernández-Pumarega, Alejandro; Amézqueta, Susana; Farré, Sandra; Muñoz-Pascual, Laura; Abraham, Michael H; Fuguet, Elisabet; Rosés, Martí


    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. Determination of hexavalent chromium concentration in industrial waste incinerator stack gas by using a modified ion chromatography with post-column derivatization method. (United States)

    Miyake, Yuichi; Tokumura, Masahiro; Iwazaki, Yuta; Wang, Qi; Amagai, Takashi; Horii, Yuichi; Otsuka, Hideyuki; Tanikawa, Noboru; Kobayashi, Takeshi; Oguchi, Masahiro


    An ion chromatography with post-column derivatization with 1,5-diphenylcarbazide (IC-DPC) analytical method was modified to enable measurement of trace-level hexavalent chromium (Cr(VI)) in air. One of the difficulties in determining trace levels of Cr(VI) in air with conventional IC-DPC methods is co-elution of the solvent and ion peaks due to high concentrations of ionic compounds in the extract. However, by using gradient elution rather than isocratic elution we were able to fully resolve the Cr(VI) ion peak from the solvent peak without the need for diluting the extract, which would have reduced the minimum quantifiable level of the method. With this method, we were able to detect Cr(VI) in air at concentrations of 5.3ng/m 3 (assuming a sampling volume of 1m 3 and a final solution volume of 10mL). Recovery tests at three different concentrations of Cr(VI) (50, 250, 1000ng) were performed with or without fly ash; recovery rates at all the concentrations of Cr(VI), with or without fly ash, ranged from 68% to 110% (mean±relative standard deviation, 96%±11%), and there were no differences in recovery rates with respect to the presence or absence of fly ash. Finally, we used the developed method to determine the concentration of Cr(VI) in stack gases collected from eight industrial waste incinerators located in Japan. The concentration of Cr(VI) in the stack gases ranged from below the method quantification limit to 3100ng/m 3 . The highest concentrations of Cr(VI) detected in the stack gases were two to three orders of magnitude higher than that in ambient air in Japan. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Changes in the basic experimental parameters of capillary gas chromatography in the 20th century. (United States)

    Berezkin, V G; Viktorova, E N


    Studies of qualitative changes in capillary gas chromatography are of significant practical and scientific interest. This paper analyzes the evolution of the most important experimental chromatographic parameters over the last three decades and is based on the use of a new approach to scientometrical research that is referred to as applied scientometry. One essential feature of this approach is that it looks at the entire contents of each paper rather than only taking account its title, abstract. and references (as is typical for conventional scientometry). In this paper, we monitor how the most important chromatographic parameters, such as column length and diameter, layer thickness, stationary liquid phases, separation temperature mode. etc., have been evolving over the period 1970-2000. We used data from the following journals: Chromatographia, Journal of Chromatography, and Journal of High Resolution Chromatography and Chromatography Communications.

  4. High-performance liquid chromatographic method for guanylhydrazone compounds. (United States)

    Cerami, C; Zhang, X; Ulrich, P; Bianchi, M; Tracey, K J; Berger, B J


    A high-performance liquid chromatographic method has been developed for a series of aromatic guanylhydrazones that have demonstrated therapeutic potential as anti-inflammatory agents. The compounds were separated using octadecyl or diisopropyloctyl reversed-phase columns, with an acetonitrile gradient in water containing heptane sulfonate, tetramethylammonium chloride, and phosphoric acid. The method was used to reliably quantify levels of analyte as low as 785 ng/ml, and the detector response was linear to at least 50 micrograms/ml using a 100 microliters injection volume. The assay system was used to determine the basic pharmacokinetics of a lead compound, CNI-1493, from serum concentrations following a single intravenous injection in rats.

  5. Experimental studies of uncertainties associated with chromatographic techniques. (United States)

    Barwick, V J; Ellison, S L; Lucking, C L; Burn, M J


    The paper describes experiments for the evaluation of uncertainties associated with a number of chromatographic parameters. Studies of the analysis of vitamins by HPLC illustrate the estimation of the uncertainties associated with experimental "input" parameters such as the detector wavelength, column temperature and mobile phase flow-rate. Experimental design techniques, which allow the efficient study a number of parameters simultaneously, are described. Multiple linear regression was used to fit response surfaces to the data. The resulting equations were used in the estimation of the uncertainties. Three approaches to uncertainty calculation were compared--Kragten's spreadsheet, symmetric spreadsheet and algebraic differentiation. In cases where non-linearity in the model was significant, agreement between the uncertainty estimates was poor as the spreadsheet approaches do not include second-order uncertainty terms.

  6. Standard Format for Chromatographic-polarimetric System small samples assessment

    International Nuclear Information System (INIS)

    Naranjo, S.; Fajer, V.; Fonfria, C.; Patinno, R.


    The treatment of samples containing optically active substances to be evaluated as part of quality control of raw material entering industrial process, and also during the modifications exerted on it to obtain the desired final composition is still and unsolved problem for many industries. That is the case of sugarcane industry. Sometimes the troubles implied are enlarged because samples to be evaluated are not bigger than one milliliter. Reduction of gel beds in G-10 and G-50 chromatographic columns having an inner diameter of 16 mm, instead of 25, and bed heights adjustable to requirements by means of sliding stoppers to increase analytical power were evaluated with glucose and sucrose standards in concentrations from 1 to 10 g/dL, using aliquots of 1 ml without undesirable dilutions that could affect either detection or chromatographic profile. Assays with seaweed extracts gave good results that are shown. It is established the advantage to know concentration of a separated substance by the height of its peak and the savings in time and reagents resulting . Sample expanded uncertainty in both systems is compared. It is also presented several programs for data acquisition, storing and processing. (Author)

  7. Determination of cyclodextrins in biological fluids by high-performance liquid chromatography with negative colorimetric detection using post-column complexation with phenolphthalein

    NARCIS (Netherlands)

    Frijlink, H.W.; Visser, J.; Drenth, B.F.H.


    A rapid and sensitive high-performance liquid chromatographic method for the analysis of beta- and gamma-cyclodextrin in aqueous biological fluids such as plasma, urine, or tissue homogenate is described. The chromatographic system consists of a microBondapak Phenyl column as stationary phase and a

  8. Analysis of Listeria using exogenous volatile organic compound metabolites and their detection by static headspace-multi-capillary column-gas chromatography-ion mobility spectrometry (SHS-MCC-GC-IMS). (United States)

    Taylor, Carl; Lough, Fraser; Stanforth, Stephen P; Schwalbe, Edward C; Fowlis, Ian A; Dean, John R


    Listeria monocytogenes is a Gram-positive bacterium and an opportunistic food-borne pathogen which poses significant risk to the immune-compromised and pregnant due to the increased likelihood of acquiring infection and potential transmission of infection to the unborn child. Conventional methods of analysis suffer from either long turn-around times or lack the ability to discriminate between Listeria spp. reliably. This paper investigates an alternative method of detecting Listeria spp. using two novel enzyme substrates that liberate exogenous volatile organic compounds in the presence of α-mannosidase and D-alanyl aminopeptidase. The discriminating capabilities of this approach for identifying L. monocytogenes from other species of Listeria are investigated. The liberated volatile organic compounds (VOCs) are detected using an automated analytical technique based on static headspace-multi-capillary column-gas chromatography-ion mobility spectrometry (SHS-MCC-GC-IMS). The results obtained by SHS-MCC-GC-IMS are compared with those obtained by the more conventional analytical technique of headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results found that it was possible to differentiate between L. monocytogenes and L. ivanovii, based on their VOC response from α-mannosidase activity.

  9. Chromatographic analysis of tryptophan metabolites. (United States)

    Sadok, Ilona; Gamian, Andrzej; Staniszewska, Magdalena Maria


    The kynurenine pathway generates multiple tryptophan metabolites called collectively kynurenines and leads to formation of the enzyme cofactor nicotinamide adenine dinucleotide. The first step in this pathway is tryptophan degradation, initiated by the rate-limiting enzymes indoleamine 2,3-dioxygenase, or tryptophan 2,3-dioxygenase, depending on the tissue. The balanced kynurenine metabolism, which has been a subject of multiple studies in last decades, plays an important role in several physiological and pathological conditions such as infections, autoimmunity, neurological disorders, cancer, cataracts, as well as pregnancy. Understanding the regulation of tryptophan depletion provide novel diagnostic and treatment opportunities, however it requires reliable methods for quantification of kynurenines in biological samples with complex composition (body fluids, tissues, or cells). Trace concentrations, interference of sample components, and instability of some tryptophan metabolites need to be addressed using analytical methods. The novel separation approaches and optimized extraction protocols help to overcome difficulties in analyzing kynurenines within the complex tissue material. Recent developments in chromatography coupled with mass spectrometry provide new opportunity for quantification of tryptophan and its degradation products in various biological samples. In this review, we present current accomplishments in the chromatographic methodologies proposed for detection of tryptophan metabolites and provide a guide for choosing the optimal approach. © 2017 The Authors. Journal of Separation Science published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Liquid chromatographic determination of water (United States)

    Fortier, N.E.; Fritz, J.S.


    A sensitive method for the determination of water in the presence of common interferences is presented. The detection system is based on the effect of water on the equilibrium which results from the reaction aryl aldehydes, such as cinnamaldehyde and methanol in the eluent to form cinnamaldehyde dimethylacetal, plus water. This equilibrium is shifted in a catalytic atmosphere of a hydrogen ion form past column reactor. The extent of the shift and the resulting change in absorbance are proportional to the amount of water present. 1 fig.

  11. Measurement of trace impurities in ultra pure hydrogen and deuterium at the parts-per-billion level using gas chromatography (United States)

    Ganzha, V.; Ivshin, K.; Kammel, P.; Kravchenko, P.; Kravtsov, P.; Petitjean, C.; Trofimov, V.; Vasilyev, A.; Vorobyov, A.; Vznuzdaev, M.; Wauters, F.


    A series of muon experiments at the Paul Scherrer Institute in Switzerland deploy ultra-pure hydrogen active targets. A new gas impurity analysis technique was developed, based on conventional gas chromatography, with the capability to measure part-per-billion (ppb) traces of nitrogen and oxygen in hydrogen and deuterium. Key ingredients are a cryogenic admixture accumulation, a directly connected sampling system and a dedicated calibration setup. The dependence of the measured concentration on the sample volume was investigated, confirming that all impurities from the sample gas are collected in the accumulation column and measured with the gas chromatograph. The system was calibrated utilizing dynamic dilution of admixtures into the gas flow down to sub-ppb level concentrations. The total amount of impurities accumulated in the purification system during a three month long experimental run was measured and agreed well with the calculated amount based on the measured concentrations in the flow.

  12. Evaluating two process scale chromatography column header designs using CFD. (United States)

    Johnson, Chris; Natarajan, Venkatesh; Antoniou, Chris


    Chromatography is an indispensable unit operation in the downstream processing of biomolecules. Scaling of chromatographic operations typically involves a significant increase in the column diameter. At this scale, the flow distribution within a packed bed could be severely affected by the distributor design in process scale columns. Different vendors offer process scale columns with varying design features. The effect of these design features on the flow distribution in packed beds and the resultant effect on column efficiency and cleanability needs to be properly understood in order to prevent unpleasant surprises on scale-up. Computational Fluid Dynamics (CFD) provides a cost-effective means to explore the effect of various distributor designs on process scale performance. In this work, we present a CFD tool that was developed and validated against experimental dye traces and tracer injections. Subsequently, the tool was employed to compare and contrast two commercially available header designs. © 2014 American Institute of Chemical Engineers.

  13. Modeling of column apparatus processes

    CERN Document Server

    Boyadjiev, Christo; Boyadjiev, Boyan; Popova-Krumova, Petya


    This book presents a new approach for the modeling of chemical and interphase mass transfer processes in industrial column apparatuses, using convection-diffusion and average-concentration models. The convection-diffusion type models are used for a qualitative analysis of the processes and to assess the main, small and slight physical effects, and then reject the slight effects. As a result, the process mechanism can be identified. It also introduces average concentration models for quantitative analysis, which use the average values of the velocity and concentration over the cross-sectional area of the column. The new models are used to analyze different processes (simple and complex chemical reactions, absorption, adsorption and catalytic reactions), and make it possible to model the processes of gas purification with sulfur dioxide, which form the basis of several patents.

  14. Maximizing Chromatographic Information from Environmental Extracts by GCxGC-ToF-MS

    NARCIS (Netherlands)

    Skoczynska, E.M.; Korytar, P.; Boer, de J.


    Comprehensive two-dimensional gas chromatography (GCxGC) coupled with a time-of-flight (ToF) detector allows the separation of many constituents of previously unresolved complex mixtures (UCM) of contaminants in sediment samples. In addition to the powerful chromatographic resolution, automated mass

  15. 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

    Energy Technology Data Exchange (ETDEWEB)

    Bhowmik, S.; Schuster, A.; Filser, J.G.


    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.)

  16. Evaluation of coverage, retention patterns, and selectivity of seven liquid chromatographic methods for metabolomics. (United States)

    Wernisch, Stefanie; Pennathur, Subramaniam


    Liquid chromatography-mass spectrometry-based metabolomics studies require highly selective and efficient chromatographic techniques. Typically employed reversed-phase (RP) methods fail to target polar metabolites, but the introduction of hydrophilic interaction liquid chromatography (HILIC) is slow due to perceived issues of reproducibility and ruggedness and a limited understanding of the complex retention mechanisms. In this study, we present a comparison of the chromatographic performance of a traditional RP-C18 column with zwitterionic, amide-, alkyl diol-, and aminoalkyl-based HILIC and mixed-mode columns. Our metabolite library represents one of the largest analyte sets available and consists of 764 authentic metabolite standards, including amino acids, nucleotides, sugars, and other metabolites, representing all major biological pathways and commonly observed exogenous metabolites (drugs). The coverage, retention patterns, and selectivity of the individual methods are highly diverse even between conceptually related HILIC methods. Furthermore, we show that HILIC sorbents having highly orthogonal selectivity and specificity enhance the coverage of major metabolite groups in (semi-) targeted applications compared to RP. Finally, we discuss issues encountered in the analysis of biological samples based on the results obtained with human plasma extracts. Our results demonstrate that fast and highly reproducible separations on zwitterionic columns are feasible, but knowledge of analyte properties is essential to avoid chromatographic bias and exclusion of key analytes in metabolomics studies. Graphical Abstract The chromatographic parameters of 764 authentic metabolite standards provide the basis for a comparison of coverage, selectivity and orthogonality of 7 reversed-phase (RP), mixed-mode (MM) and hydrophilic interaction liquid chromatography (HILIC) methods.

  17. Evaluation of composition of natural gas used as a fuel in pickups in motor racing; Avaliacao da composicao do gas natural utilizado como combustivel em pickups em corridas automobilisticas

    Energy Technology Data Exchange (ETDEWEB)

    Faria, Fatima D.; Silva, Haroldo F. da; Leal, Glaucia P.; Freire, Luiz Gustavo de M. [PETROBRAS, Rio de Janeiro, RJ (Brazil); Balthar, Alcides R.; Bayer, Marcilio de M. [Centro de Tecnologias do Gas (CTGAS), Natal, RN (Brazil)


    Concerned with the quality of their products, PETROBRAS could not have a different attitude in relation to the natural gas vehicular (NGV). For this, the compositions of natural gases used in the pickup of PETROBRAS Pickup Racing have been determined. In the tests accomplished in the race tracks, after the trainings and after the races, a portable Micro gas chromatograph, model Agilent 3000A have been used. This equipment have tree thermal conductivity detectors, columns appropriate to determine the components of the natural gas (N{sub 2}, CO{sub 2}, CH{sub 4}, C{sub 2}H{sub 6}, C{sub 3}H{sub 8}, C{sub 4}H{sub 10} and C{sub 5+}, at 70 deg C) and also the presence of O{sub 2}, at 110 deg C. The gas chromatograph is controlled by a laptop that calculates the final composition of the NGV and the calorific value. The tests proved that the composition of NGV was similar of a standard natural gas. This proved that the performance of the pickups, in the race, is related to the quality of the natural gas used. This project was developed by PETROBRAS/CENPES, CTGAS and RedeGasEnergia (author)

  18. Multiresidue pesticide analysis of botanical dietary supplements using salt-out acetonitrile extraction, solid-phase extraction cleanup column, and gas chromatography-triple quadrupole mass spectrometry. (United States)

    Hayward, Douglas G; Wong, Jon W; Shi, Feng; Zhang, Kai; Lee, Nathaniel S; DiBenedetto, Alex L; Hengel, Mathew J


    Dietary supplements form an increasing part of the American diet, yet broadly applicable multiresidue pesticide methods have not been evaluated for many of these supplements. A method for the analysis of 310 pesticides, isomers, and pesticide metabolites in dried botanical dietary supplements has been developed and validated. Sample preparation involved acetonitrile:water added to the botanical along with anhydrous magnesium sulfate and sodium chloride for extraction, followed by cleanup with solid-phase extraction using a tandem cartridge consisting of graphitized carbon black (GCB) and primary-secondary amine sorbent (PSA). Pesticides were measured by gas chromatography-tandem mass spectrometry. Accuracy and precision were evaluated through fortifications of 24 botanicals at 10, 25, 100, and 500 μg/kg. Mean pesticide recoveries and relative standard deviations (RSDs) for all botanicals were 97%, 91%, 90%, and 90% and 15%, 10%, 8%, and 6% at 10, 25, 100, and 500 μg/kg, respectively. The method was applied to 21 incurred botanicals. Quinoxyfen was measured in hops (100-620 μg/kg). Tetraconazole (48 μg/kg), tetramethrin (15 μg/kg), methamidophos (50 μg/kg), and chlorpyrifos (93 μg/kg) were measured in licorice, mallow, tea, and tribulus, respectively. Quintozene, its metabolites and contaminants (pentachloroaniline, pentachlorobenzene, pentachloroanisole, and pentachlorothioanisole and hexachlorobenzene and tecnazene, respectively), with hexachlorocyclohexanes and DDT were identified in ginseng sources along with azoxystrobin, diazinon, and dimethomorph between 0.7 and 2800 μg/kg. Validation with these botanicals demonstrated the extent of this method's applicability for screening 310 pesticides in a wide array of botanical dietary supplements.

  19. Small Column Ion Exchange

    International Nuclear Information System (INIS)

    Huff, Thomas


    Small Column Ion Exchange (SCIX) leverages a suite of technologies developed by DOE across the complex to achieve lifecycle savings. Technologies are applicable to multiple sites. Early testing supported multiple sites. Balance of SRS SCIX testing supports SRS deployment. A forma Systems Engineering Evaluation (SEE) was performed and selected Small Column Ion Exchange columns containing Crystalline Silicotitanate (CST) in a 2-column lead/lag configuration. SEE considered use of Spherical Resorcinol-Formaldehyde (sRF). Advantages of approach at SRS include: (1) no new buildings, (2) low volume of Cs waste in solid form compared to aqueous strip effluent; and availability of downstream processing facilities for immediate processing of spent resin.

  20. The use of phospholipid modified column for the determination of lipophilic properties in high performance liquid chromatography. (United States)

    Godard, Tal; Grushka, Eli


    A new chromatographic stationary phase obtained by coating a reversed phase amide column with phosphatidylcholine based liposomes solution to yield a phospholipid modified column (PLM). The modification is achieved by the dynamic coating method which recycles the coating solution through the column in a closed loop for a period of 24 h. The chromatographic properties of the new column have changed significantly as compared to the original amide column due to the phospholipid coating. A good correlation was observed between n-octanol/water logP values and the logarithm of the retention factor obtained on the PLM column for a large number of solutes. In addition the PLM column was characterized using the linear solvation energy relationship (LSER). The values of the LSER system constants for the PLM column were calculated and were found to be very close to those of the n-octanol/water extraction system thus suggesting that the PLM column can be used for the estimation of n-octanol/water partition coefficient and serve as a possible alternative to the shake-flask method for lipophilicity determination. In addition, the results suggest that the PLM column can provide an alternative to other phospholipid-based column such as the IAM and the DPC columns. Copyright © 2011 Elsevier B.V. All rights reserved.