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Sample records for 6-column gas chromatograph

  1. Gas Chromatograph.

    DTIC Science & Technology

    Patents, * Gas chromotography , *Hydrocarbons, *Carbon monoxide, *Carbon dioxide, *Water, Field equipment, Portable equipment, Sensitivity, Halogenated hydrocarbons, Test methods, Gases, Liquids, Purity

  2. Gas chromatograph injection system

    NASA Technical Reports Server (NTRS)

    Pollock, G. E.; Henderson, M. E.; Donaldson, R. W., Jr. (Inventor)

    1975-01-01

    An injection system for a gas chromatograph is described which uses a small injector chamber (available in various configurations). The sample is placed in the chamber while the chamber is not under pressure and is not heated, and there is no chance of leakage caused by either pressure or heat. It is injected into the apparatus by changing the position of a valve and heating the chamber, and is volatilized and swept by a carrier gas into the analysis apparatus.

  3. Microminiature gas chromatograph

    DOEpatents

    Yu, C.M.

    1996-12-10

    A microminiature gas chromatograph ({mu}GC) comprising a least one silicon wafer, a gas injector, a column, and a detector. The gas injector has a normally closed valve for introducing a mobile phase including a sample gas in a carrier gas. The valve is fully disposed in the silicon wafer(s). The column is a microcapillary in silicon crystal with a stationary phase and is mechanically connected to receive the mobile phase from the gas injector for the molecular separation of compounds in the sample gas. The detector is mechanically connected to the column for the analysis of the separated compounds of sample gas with electronic means, e.g., ion cell, field emitter and PIN diode. 7 figs.

  4. Microminiature gas chromatograph

    DOEpatents

    Yu, Conrad M.

    1996-01-01

    A microminiature gas chromatograph (.mu.GC) comprising a least one silicon wafer, a gas injector, a column, and a detector. The gas injector has a normally closed valve for introducing a mobile phase including a sample gas in a carrier gas. The valve is fully disposed in the silicon wafer(s). The column is a microcapillary in silicon crystal with a stationary phase and is mechanically connected to receive the mobile phase from the gas injector for the molecular separation of compounds in the sample gas. The detector is mechanically connected to the column for the analysis of the separated compounds of sample gas with electronic means, e.g., ion cell, field emitter and PIN diode.

  5. Deconvolution of gas chromatographic data

    NASA Technical Reports Server (NTRS)

    Howard, S.; Rayborn, G. H.

    1980-01-01

    The use of deconvolution methods on gas chromatographic data to obtain an accurate determination of the relative amounts of each material present by mathematically separating the merged peaks is discussed. Data were obtained on a gas chromatograph with a flame ionization detector. Chromatograms of five xylenes with differing degrees of separation were generated by varying the column temperature at selected rates. The merged peaks were then successfully separated by deconvolution. The concept of function continuation in the frequency domain was introduced in striving to reach the theoretical limit of accuracy, but proved to be only partially successful.

  6. Dual liquid and gas chromatograph system

    DOEpatents

    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.

  7. Dual liquid and gas chromatograph system

    DOEpatents

    Gay, Don D.

    1985-01-01

    A chromatographic system 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 non-transparent 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) extremely 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.

  8. A Quantitative Gas Chromatographic Ethanol Determination.

    ERIC Educational Resources Information Center

    Leary, James J.

    1983-01-01

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

  9. 40 CFR 1065.267 - Gas chromatograph.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Gas chromatograph. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon Measurements § 1065.267 Gas...

  10. 40 CFR 1065.267 - Gas chromatograph.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Gas chromatograph. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon Measurements § 1065.267 Gas...

  11. Portable gas chromatograph-mass spectrometer

    DOEpatents

    Andresen, Brian D.; Eckels, Joel D.; Kimmons, James F.; Myers, David W.

    1996-01-01

    A gas chromatograph-mass spectrometer (GC-MS) 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.

  12. Portable gas chromatograph-mass spectrometer

    DOEpatents

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

    1996-06-11

    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.

  13. Portable gas chromatograph-mass spectrometer

    SciTech Connect

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

    1994-12-31

    A gas chromatograph-mass spectrometer (GC-MS) 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.

  14. Hand-held multiple system gas chromatograph

    DOEpatents

    Yu, Conrad M.

    2001-01-01

    A multiple parallel hand-held gas chromatograph (GC) system which includes several independent GCs. Each independent GC has its own injector, separation column, detector and oven and the GCs are mounted in a light weight hand-held assembly. Each GC operates independently and simultaneously. Because of different coatings in different separation columns, different retention times for the same gas will be measured. Thus, for a GC system with multiple parallel GCs, the system can measure, in a short period, different retention times and provide a cross-reference in the determination of the measured gas and to become a two-dimensional system for direct field use.

  15. A Small-Scale Low-Cost Gas Chromatograph

    ERIC Educational Resources Information Center

    Gros, Natasa; Vrtacnik, Margareta

    2005-01-01

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

  16. Versatile gas/particle ion chromatograph.

    PubMed

    Ullah, S M Rahmat; Takeuchi, Masaki; Dasgupta, Purnendu K

    2006-02-01

    A new, compact gas/particle ion chromatograph has been developed for measuring ionic constituents in PM2.5 (particulate matter of aerodynamic diameter < or = 2.5 microm) and water-soluble ionogenic gases. The instrument has separate sampling channels for gases and particles. In one, a membrane denuder collects soluble gases for preconcentration and analysis. In the other, a cyclone removes larger particles, a membrane denuder removes soluble gases, and a continuously wetted hydrophilic filter collects particles. A single, multiport, syringe pump handles liquid transport, and one conductivity detector measures anions and ammonium for both channels. Electrodialytically generated gradient hydroxide eluent permits 20 min chromatographic runs. Gas/particle samples are each collected for 40 min, butthe sampling intervals are staggered by 20 min. Liquid samples from the gas denuder and particle collector are aspirated and preconcentrated on sequential cation and anion concentrators and transferred respectively to an ammonia transfer device and an anion separation column. The flow configuration results in an ammonium peak before anion peaks in the chromatogram. The system measures ammonia, organic acids (such as acetic, formic, and oxalic acids), HCl, HONO, SO2, HNO3, and the corresponding ions in the aerosol phase. Low ng/m3 to sub-ng/m3 limits of detection (LODs) are attained for most common gases and particulate constituents, the LODs for gaseous SO2 to NH3 range, for example, from sub parts per trillion by volume (sub-pptv) to approximately 5 pptv.

  17. High performance hand-held gas chromatograph

    SciTech Connect

    Yu, C.M.

    1998-04-28

    The Microtechnology Center of Lawrence Livermore National Laboratory has developed a high performance hand-held, real time detection gas chromatograph (HHGC) by Micro-Electro-Mechanical-System (MEMS) technology. The total weight of this hand-held gas chromatograph is about five lbs., with a physical size of 8{close_quotes} x 5{close_quotes} x 3{close_quotes} including carrier gas and battery. It consumes about 12 watts of electrical power with a response time on the order of one to two minutes. This HHGC has an average effective theoretical plate of about 40k. Presently, its sensitivity is limited by its thermal sensitive detector at PPM. Like a conventional G.C., this HHGC consists mainly of three major components: (1) the sample injector, (2) the column, and (3) the detector with related electronics. The present HHGC injector is a modified version of the conventional injector. Its separation column is fabricated completely on silicon wafers by means of MEMS technology. This separation column has a circular cross section with a diameter of 100 pm. The detector developed for this hand-held GC is a thermal conductivity detector fabricated on a silicon nitride window by MEMS technology. A normal Wheatstone bridge is used. The signal is fed into a PC and displayed through LabView software.

  18. Detection system for a gas chromatograph

    DOEpatents

    Hayes, John M.; Small, Gerald J.

    1984-01-01

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

  19. FTIR gas chromatographic analysis of perfumes

    NASA Astrophysics Data System (ADS)

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

    1992-03-01

    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.

  20. Fast gas chromatographic separation of biodiesel.

    SciTech Connect

    Pauls, R. E.

    2011-05-01

    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 x 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.

  1. Gas Chromatographic Detectors for Exobiology Flight Experiments

    NASA Technical Reports Server (NTRS)

    Kojiro, Daniel R.; Humphry, Donald E.; Takeuchi, Nori; Chang, Sherwood (Technical Monitor)

    1997-01-01

    Exobiology flight experiments require highly sensitive instrumentation for in situ chemical analysis of the volatile chemical species that occur in the atmospheres and surfaces of various bodies within the solar system. The complex mixtures encountered place a heavy burden on the analytical instrumentation to detect and identify all species present. Future missions to Mars', comets, or planetary moons such as Europa, will perform experiments with complex analyses. In addition, instrumentation for such missions must perform under severely restricted conditions with limited resources. To meet these analytical requirements, improved methods and highly sensitive yet smaller instruments must continually be developed with increasingly greater capabilities. We describe here efforts to achieve this objective, for past and future missions, through the development of new or the improvement of existing sensitive, miniaturized gas chromatographic detectors.

  2. Gas chromatographic analysis of trace gas impurities in tungsten hexafluoride.

    PubMed

    Laurens, J B; de Coning, J P; Swinley, J M

    2001-03-09

    Highly reactive fluorinated gaseous matrices require special equipment and techniques for the gas chromatographic analysis of trace impurities in these gases. The impurities that were analysed at the low-microg/l levels included oxygen, nitrogen, carbon dioxide, carbon monoxide, sulfur hexafluoride and hydrogen. This paper describes the use of a system utilising backflush column switching to protect the columns and detectors in the analysis of trace gas impurities in tungsten hexafluoride. Two separate channels were used for the analysis of H2, O2, N2, CO, CO2 and SF6 impurities with pulsed discharge helium ionisation detection.

  3. On-line gas chromatographic analysis of airborne particles

    DOEpatents

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

    2012-01-03

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

  4. Gas Chromatographic Determination of Enrivonmentally Significant Pesticides.

    ERIC Educational Resources Information Center

    Rudzinski, Walter E.; Beu, Steve

    1982-01-01

    A chromatographic procedure for analyzing organophosphorus pesticides (such as PCB's, nitrosamines, and phthalate esters) in orange juice is described, including a summary of the method, instrumentation, methodology, results/discussion, and calculations. (JN)

  5. [The gas chromatographic detection of acetylene in cadaveric material].

    PubMed

    Iablochkin, V D

    1999-01-01

    Acetylene traces were detected by gas chromatography in the cadaveric right crural muscle of a 30-year-old man dead from an explosion of an acetylene reservoir at a plant. Acetylene was identified using the absolute calibration method on 3 standard gas chromatographic columns, reaction gas chromatography, and acetylene "deduction" by silver sulfate on silicagel.

  6. Gas chromatographic determination of sulphur compounds in town gas.

    PubMed

    Hoshika, Y; Iida, Y

    1977-04-11

    The gas chromatographic (GC) determination of the sulphur compounds in town gas (in the Nagoya area) was studied by using a flame-photometric detector (FPD) and the cold-trap method with liquid oxygen. The column packings used were 25% TCEP on Shimalite (AW, DMCS), 25% TCP on Shimalite (AW, DMCS), 10% PPE on Shimalite TPA, Porapak Q and silica gel. The major components identified were carbonyl sulphide, hydrogen sulphide, carbon disulphide, thiophene and tetrahydrothiophene (THT). The identities of thiophene and THT were also confirmed by GC combined with the use of a quadrupole mass spectrometer. The average concentrations and standard deviations of thiophene and THT were 8.8 +/- 1.8and 124 +/- 35 ng per 0.051, respectively. The latter value corresponds to 0.7 ppm, which is relatively high for the concentration of an odorant.

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

    USGS Publications Warehouse

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

    1984-01-01

    Most geological samples and some synthetic materials contain fluid inclusions. These inclusions preserve for us tiny samples of the liquid and/or the gas phase that was present during formation, although in some cases they may have undergone significant changes from the original material. Studies of the current composition of the inclusions provide data on both the original composition and the change since trapping. These inclusions are seldom larger than 1 millimeter in diameter. The composition varies from a single major compound (e.g., water) in a single phase to a very complex mixture in one or more phases. The concentration of some of the compounds present may be at trace levels. We present here some analyses of inclusions in a variety of geological samples, including diamonds. We used a sample crusher and a gas chromatography-mass spectrometry (GC-MS) system to analyze for organic and inorganic volatiles present as major to trace constituents in inclusions. The crusher is a hardened stainless-steel piston cylinder apparatus with tungsten carbide crusing surfaces, and is operated in a pure helium atmosphere at a controlled temperature. Samples ranging from 1 mg to 1 g were crushed and the released volatiles were analyzed using multi-chromatographic columns and detectors, including the sensitive helium ionization detector. Identification of the GC peaks was carried out by GC-MS. This combination of procedures has been shown to provide geochemically useful information on the process involved in the history of the samples analyzed. ?? 1984.

  8. [Derivative gas chromatographic analysis of fructooligosaccharide in fermented sucrose].

    PubMed

    Cai, W M; Liu, H; Sun, X J

    2000-01-01

    As a new sweetener, fructooligosaccharide is paid more and more attention for its health improvement property. It includes trisaccharide, tetrasaccharide and pentasaccharide, and can be produced from sucrose by the fermentation of microorganism. In order to analyze the content of fructooligosaccharide in fermented sugar by gas chromatography, fructooligosaccharide was transformed into trimethylsilyl derivatives. Based on the modified gas chromatograph SP2308, and under the chosen chromatographic conditions with 0.53 mm capillary column of OV-101, the contents of fructose, glucose, sucrose and fructooligosaccharide were determined by programmed temperature chromatography. The recovery of fructooligosaccharide was satisfactory.

  9. Catalytically-Promoted Analyte Derivatization Inside a Gas Chromatographic Inlet

    PubMed Central

    Fowler, William K.; Gamble, Kelly J.; Wright, Amber R.

    2010-01-01

    Reported here is a preliminary assessment of the feasibility of catalyzing on-line derivatization reactions inside the inlet (i.e., the injection port) of a gas chromatograph (GC) with solid heterogeneous catalysts. The experiments described here entail the installation of candidate catalysts inside the GC inlet liner and the subsequent injection of analyte/reagent mixtures onto the catalyst beds. Two catalysts are identified, each of which clearly catalyzes one of the chosen model derivatization reactions in the inlet of a GC. This result supports our hypothesis that on-line derivatizations can, in principle, be reproducibly catalyzed inside the GC inlet by solid heterogeneous catalysts and that the presence of such catalysts in the inlet do not necessarily cause a serious loss of instrument performance or chromatographic efficiency. PMID:20822662

  10. Evaluation of Gas Chromatographic Methods for Analysis of Gasoline/Oxygenate Blends.

    DTIC Science & Technology

    1981-12-01

    determination of various oxygenated compounds in gasoline by gas chromotography have been developed.(3-6) These include gas chromatographic (GC) analysis of the...ID-Ai33 0i6 EVALUATION OF GAS CHROMATOGRAPHIC METHODS FOR ANALYSIS i/t OF GASOLINE/OXYGEN.. (U) SOUTHWEST RESEARCH INST SAN ANTONIO TX ARMY FUELS...0 EVALUATION OF GAS -CHROMATOGRAPHIC METHODS FOR ANALYSIS OF GASOLINE/OXYGENATE BLENDS INTERIM REPORT

  11. Preliminary numerical analysis of improved gas chromatograph model

    NASA Technical Reports Server (NTRS)

    Woodrow, P. T.

    1973-01-01

    A mathematical model for the gas chromatograph was developed which incorporates the heretofore neglected transport mechanisms of intraparticle diffusion and rates of adsorption. Because a closed-form analytical solution to the model does not appear realizable, techniques for the numerical solution of the model equations are being investigated. Criteria were developed for using a finite terminal boundary condition in place of an infinite boundary condition used in analytical solution techniques. The class of weighted residual methods known as orthogonal collocation is presently being investigated and appears promising.

  12. Gas chromatographic retention characteristics of phenols with Superox-20M

    SciTech Connect

    White, C.M.; Li, N.C.

    1982-08-01

    The gas chromatographic retention characteristics of a variety of underivatized phenols have been studied by using Superox-20M coated on fused silica. The relative retention times of thes compounds were measured at 160, 150, and 140/sup 0/C in order to determine the effect of operating temperature on relative retention. This information is used to predict relative retention times of phenols for which we had no standards. The linear temperature-programmed retention indexes of the solutes were measured. The retention of phenols on this phase is a function of the compounds vapor pressure, its ability to hydrogen bond with the stationary phase, and the strengths of those hydrogen bonds. These properties are in turn governed by steric, inductive, and resonance effects of the substituents. Linear free-energy relations between the logarithm of the ratio of the activity coefficients of phenol to substituted phenol (calculated from relative retention data) and the chromatographic substituent constant, sigma/sub c/, have been determined for some phenols on Superox-20M. Lastly, it was shown by nuclear magnetic resonance experiments that Superox-20M is apparently a poly(ethylene glycol) (also called a polyoxiran or poly(ethylene oxide)). 5 figures, 3 tables.

  13. The gas chromatographic resolution of DL-isovaline

    NASA Technical Reports Server (NTRS)

    Flores, J. J.; Bonner, W. A.; Van Dort, M. A.

    1977-01-01

    Isovaline is of cosmological interest because it is one of the 12 non-protein amino acids which have been isolated from the Murchison meteorite, and unlike the other chiral amino acids in this meteorite, it has no alpha-hydrogen at its asymmetric center and hence cannot racemize by the customary alpha-hydrogen-dependent mechanisms which engender racemization in ordinary amino acids. Experiments were conducted in which a .01 M solution of N-TFA-DL-isovalyl-L-leucine isopropyl ester in nitromethane was injected into the capillary column of a gas chromatograph coupled to a digital electronic integrator-recorder. Efflux times and integrated peak area percents are shown next to each diastereometer peak.

  14. Gas chromatographic determination of oxalic acid in foods.

    PubMed

    Ohkawa, H

    1985-01-01

    A new quantitative gas chromatographic (GC) method has been developed for the determination of oxalic acid in foods. Solid sample is extracted with water (soluble oxalic acid) or 2N hydrochloric acid (total oxalic acid) at room temperature. An aliquot of sample extract is evaporated to dryness, and the oxalic acid in the residue is methylated with 7% hydrochloric acid-methanol. The reaction mixture is extracted with chloroform, and dimethyl oxalate is quantitated by GC. Recovery of oxalic acid added to liquid samples averaged 100.6%; recoveries from extracts of solid samples were 96.2-99.5 and 97.2-100.1% for water and hydrochloric acid extractions, respectively. Results are shown for determination of oxalic acid in spinach and beverages. The technique is simple, rapid, and accurate, and small samples may be used. The limit of determination is 20 micrograms.

  15. Fatty acids determination in Bronte pistachios by gas chromatographic method.

    PubMed

    Pantano, Licia; Lo Cascio, Giovanni; Alongi, Angelina; Cammilleri, Gaetano; Vella, Antonio; Macaluso, Andrea; Cicero, Nicola; Migliazzo, Aldo; Ferrantelli, Vincenzo

    2016-10-01

    A gas chromatographic with flame ionization detector (GC-MS FID) method for the identification and quantification of fatty acids based on the extraction of lipids and derivatisation of free acids to form methyl esters was developed and validated. The proposed method was evaluated to a number of standard FAs, and Bronte pistachios samples were used for that purpose and to demonstrate the applicability of the proposed method. In this regard, repeatability, mean and standard deviation of the analytical procedure were calculated. The results obtained have demonstrated oleic acid as the main component of Bronte pistachios (72.2%) followed by linoleic acid (13.4%) and showed some differences in composition with respect to Tunisian, Turkish and Iranian pistachios.

  16. Doxylamine: a cause for false-positive gas chromatographic assay for phencyclidine.

    PubMed

    Schaldenbrand, J D; McClatchey, K D; Patel, J A; Muilenberg, M J

    1981-01-01

    A 25-year-old white woman ingested an unknown quantity of doxylamine succinate and flurazepam. Urine immunoassay screen (EMIT-dau) was positive for benzodiazopine and negative for phencyclidine. Subsequent gas chromatographic assay of the urine revealed a markedly positive assay for phencyclidine. Doxylamine was ultimately found to be the cause for the false-positive gas chromatographic assay for phencyclidine.

  17. Gas chromatograph-mass spectrometer (GC/MS) system for quantitative analysis of reactive chemical compounds

    DOEpatents

    Grindstaff, Quirinus G.

    1992-01-01

    Described is a new gas chromatograph-mass spectrometer (GC/MS) system and method for quantitative analysis of reactive chemical compounds. All components of such a GC/MS system external to the oven of the gas chromatograph are programmably temperature controlled to operate at a volatilization temperature specific to the compound(s) sought to be separated and measured.

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

    PubMed

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

    2014-03-01

    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 (2.2.1) heptan-2-one, 1, 7, 7-trimethyl-(1S, 4S)-; (3) Phenol, 2-methoxy-4-(1-propenyl)-; (4) Benzene, 1-(1, 5-dimethyl-4-hexenyl)-4-methyl-; (5) Naphthalene, 1, 2, 3, 5, 6, 8a-hexahydro4, 7-dimethyl-1-1-(1-methylethyl)-, (1S-cis)-; (6) Phenol, 2-methoxy-; (7) Benzaldehyde, 3-hydroxy-4-methoxy-; (8) 11, 13-Eicosadienoic acid, methyl ester; (9) 2-Furancarboxaldehyde, 5-methyl-; (10) Maltol; (11) Phenol; (12) Hydroquinone; (13) 1H-Indene, 1-ethylideneoctahydro-7a-methyl-, (1E, 3a.alpha, 7a.beta.). Other compounds (14) 3-methyl butanal; (15) (D)-Limonene; (16) 1-methyl-4-(1-methyl ethyl) benzene; (17) Butanoic acid methyl ester; (18) 2-methyl propanal; (19) 2-butanone; (20) 2-pentanone; and (21) 2-methyl butane were also identified when P&T GC-MS was performed. Of the 21 compounds identified, 12 were validated using chemical standards. The identified compounds were found to be terpenes, derivatives of terpenes, esters, ketones, aldehydes, and phenol-derived aromatic compounds; these are the primary constituents of the essential oils of many plants and flowers.

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

    PubMed Central

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

    2014-01-01

    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 (2.2.1) heptan-2-one, 1, 7, 7-trimethyl-(1S, 4S)-; (3) Phenol, 2-methoxy-4-(1-propenyl)-; (4) Benzene, 1-(1, 5-dimethyl-4-hexenyl)-4-methyl-; (5) Naphthalene, 1, 2, 3, 5, 6, 8a-hexahydro4, 7-dimethyl-1-1-(1-methylethyl)-, (1S-cis)-; (6) Phenol, 2-methoxy-; (7) Benzaldehyde, 3-hydroxy-4-methoxy-; (8) 11, 13-Eicosadienoic acid, methyl ester; (9) 2-Furancarboxaldehyde, 5-methyl-; (10) Maltol; (11) Phenol; (12) Hydroquinone; (13) 1H-Indene, 1-ethylideneoctahydro-7a-methyl-, (1E, 3a.alpha, 7a.beta.). Other compounds (14) 3-methyl butanal; (15) (D)-Limonene; (16) 1-methyl-4-(1-methyl ethyl) benzene; (17) Butanoic acid methyl ester; (18) 2-methyl propanal; (19) 2-butanone; (20) 2-pentanone; and (21) 2-methyl butane were also identified when P&T GC-MS was performed. Of the 21 compounds identified, 12 were validated using chemical standards. The identified compounds were found to be terpenes, derivatives of terpenes, esters, ketones, aldehydes, and phenol-derived aromatic compounds; these are the primary constituents of the essential oils of many plants and flowers. PMID:24804069

  20. The Huygens Gas Chromatograph Mass Spectrometer Investigation Of Titan

    NASA Astrophysics Data System (ADS)

    Atreya, Sushil; Harpold, Dan; Owen, Tobias

    2015-04-01

    A decade ago, on 14 January 2005, the Huygens probe of the Cassini-Huygens mission descended through the smog filled atmosphere of Titan and landed on the surface, revealing for the first time the extraordinary nature of Saturn's largest moon. One of the six payload instruments, the gas chromatograph mass spectrometer (GCMS), was crucial for measuring the composition of the atmosphere and the surface of Titan [1,2]. Most of the GCMS findings were "firsts", including the first direct identification of molecular nitrogen as the bulk constituent of the atmosphere, first vertical profile of Titan's second most abundant volatile, methane, first determination of primordial and radiogenic argon, first quantification of a number of stable gas isotopes, and the first measurements of the make-up of Titan's surface. These data are key to understanding why Titan is so unique amongst planetary moons in possessing a massive atmosphere [3], how Titan maintains a cycle of methane complete with surface reservoirs, evaporation and condensation like the hydrological cycle on earth [3,4,5], and what is responsible for the photochemical smog on Titan that plays a central role in the very existence of an atmosphere on Titan [3]. This presentation will discuss the GCMS investigation and how it helped shape our current view of Titan. [website for downloading pdf's of relevant papers: www.umich.edu/~atreya] [1] Niemann, H. B. et al., The abundances of constituents of Titan's atmosphere from the GCMS instrument on the Huygens probe, Nature 438, 779-784, 2005. [2] Niemann, H. B. et al., The composition of Titan's lower atmosphere and simple surface volatiles as measured by the Cassini-Huygens probe gas chromatograph mass spectrometer experiment, J. Geophys. Res. (Planets) 115, 12006, 2010. [3] Atreya S. K., R. D. Lorenz and J. H. Waite, Volatile origin and cycles: Nitrogen and methane, in Titan from Cassini-Huygens, R. H. Brown, J. P. Lebreton and J. Waite, (eds.), Springer Dordrecht

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

    DTIC Science & Technology

    1985-08-01

    Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy . 15. B. Welton, Column Switching and Backflush Techniques with Open Tubular and...Packed Columns in Gas Chromatography, Paper presented at 1978 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy . 16. R. Miller... Applied Spectroscopy . 33. J. F. Pankow and L. M. Isabelle, Interface of the Direct Coupling of a Second Gas Chromatograph to a Gas Chromatograph/ Mass

  2. Micro-miniature gas chromatograph column disposed in silicon wafers

    DOEpatents

    Yu, Conrad M.

    2000-01-01

    A micro-miniature gas chromatograph column is fabricated by forming matching halves of a circular cross-section spiral microcapillary in two silicon wafers and then bonding the two wafers together using visual or physical alignment methods. Heating wires are deposited on the outside surfaces of each wafer in a spiral or serpentine pattern large enough in area to cover the whole microcapillary area inside the joined wafers. The visual alignment method includes etching through an alignment window in one wafer and a precision-matching alignment target in the other wafer. The two wafers are then bonded together using the window and target. The physical alignment methods include etching through vertical alignment holes in both wafers and then using pins or posts through corresponding vertical alignment holes to force precision alignment during bonding. The pins or posts may be withdrawn after curing of the bond. Once the wafers are bonded together, a solid phase of very pure silicone is injected in a solution of very pure chloroform into one end of the microcapillary. The chloroform lowers the viscosity of the silicone enough that a high pressure hypodermic needle with a thumbscrew plunger can force the solution into the whole length of the spiral microcapillary. The chloroform is then evaporated out slowly to leave the silicone behind in a deposit.

  3. Capillary gas chromatographic analysis of pans with luminol chemilumnescent detection

    SciTech Connect

    Gaffney, J.; Bornick, R.; Chen, Yu-Harn; Marley, N.

    1996-12-31

    Peroxyacyl nitrates (PANs) are important air pollutants in tropospheric chemistry. PANs are known to be potent phytotoxins at low ppb concentrations and are lachrymators. They can also transport the more reactive nitrogen dioxide long distances, because they are in equilibrium with that NO{sub x} species. Since PANs are trapped peroxyradicals, they are a direct measure of the peroxyradical levels and the of {open_quotes}photochemical age{close_quotes} of an air parcel. The PANs are typically measured in the atmosphere by using electron capture detection methods. These methods suffer from large background signals and detector responses to oxygen and water vapor. This paper describes the combination of a capillary gas chromatographic column with a modified luminol chemiluminescent nitrogen dioxide detector (Scintrex, Luminox) for rapid and sensitive detection of nitrogen dioxide, peroxyacetyl nitrate, peroxypropionyl nitrate, and peroxybutyryl nitrate. Detection limits for this approach in the low tens of parts per trillion have been observed with total analysis times of less than three minutes. We will discuss the potential application of this method to other compounds, particularly, organonitrates, in a pyrolysis system and/or with ozone addition to the sampling streams.

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

    NASA Technical Reports Server (NTRS)

    MacAskill, John A.; Tsikata, Edem

    2014-01-01

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

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

    PubMed

    Regert, M; Langlois, J; Colinart, S

    2005-10-14

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

  6. Oxygen carrier for gas chromatographic analysis of inert gases in propellants

    NASA Technical Reports Server (NTRS)

    Cannon, W. A.

    1972-01-01

    Gas chromatographic determination of small quantities of inert gases in reactive propellants is discussed. Operating conditions used for specific analyses of helium in diborane and nitrogen in oxygen difluoride are presented in tabular form.

  7. A Miniature Gas Chromatograph Mass Spectrometer (GCMS) for Planetary Atmospheres Studies

    NASA Astrophysics Data System (ADS)

    Simcic, J.; Madzunkov, S. M.; Bae, B.; Nikolic, D.; Darrach, M.

    2016-10-01

    Presented herein are the latest achievements in developing an instrument with the same analytical performance of commercial Gas Chromatograph Mass Spectrometer systems but approximately an order of magnitude smaller and optimized for space missions.

  8. Sensitive gas chromatographic detection of acetaldehyde and acetone using a reduction gas detector

    NASA Technical Reports Server (NTRS)

    O'Hara, Dean; Singh, Hanwant B.

    1988-01-01

    The response of a newly available mercuric oxide Reduction Gas Detector (RGD-2) to subpicomole and larger quantities of acetaldehyde and acetone is tested. The RGD-2 is found to be capable of subpicomole detection for these carbonyls and is more sensitive than an FID (Flame Ionization Detector) by an order of magnitude. Operating parameters can be further optimized to make the RGD-2 some 20-40 times more sensitive than an FID. The detector is linear over a wide range and is easily adapted to a conventional gas chromatograph (GC). Such a GC-RGD-2 system should be suitable for atmospheric carbonyl measurements in clean as well as polluted environments.

  9. Gas chromatographic separation of hydrogen isotopes using metal hydrides

    SciTech Connect

    Aldridge, F.T.

    1984-05-09

    A study was made of the properties of metal hydrides which may be suitable for use in chromatographic separation of hydrogen isotopes. Sixty-five alloys were measured, with the best having a hydrogen-deuterium separation factor of 1.35 at 60/sup 0/C. Chromatographic columns using these alloys produced deuterium enrichments of up to 3.6 in a single pass, using natural abundance hydrogen as starting material. 25 references, 16 figures, 4 tables.

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

    PubMed

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

    1995-01-01

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

  11. Gas chromatographic method for measuring nitrogen dioxide and peroxyacetyl nitrate in air without compressed gas cylinders

    SciTech Connect

    Burkhardt, M.R.; Maniga, N.I.; Stedman, D.H.; Paur, R.J.

    1988-04-15

    A gas chromatographic technique that measures atmospheric concentrations of peroxyacetyl nitrate (PAN) and NO/sub 2/ has been developed that uses luminol-based chemiluminescence for detection. The carrier gas is air that has been scrubbed by passing it over FeSO/sub 4/, which eliminates the need for any compressed gas cylinders. A novel gas sampling system and time enable variable sample volumes of contaminated air to be injected. Ambient PAN and NO/sub 2/ measurements can be made every 40 s with detection limits of 0.12 ppb for PAN and 0.2 ppb for NO/sub 2/. Seven other atmospheric species, including ozone, gave no interference. Linear response was observed for NO/sub 2/ from 0.2 to 170 ppb and for PAN from 1 to 70 ppb.

  12. Considerations on the temperature dependence of the gas-liquid chromatographic retention.

    PubMed

    González, Francisco Rex

    2002-01-04

    A discussion on the temperature dependence of the partition coefficient K is developed. This discussion embraces topics such as the limitations of conventional thermodynamic approaches followed in the chromatographic literature, qualitative theoretical notions arising from molecular thermodynamics and the experimental information that is accessible through modern capillary gas chromatography. It is shown that the heat capacity difference of solute transfer for flexible molecules has at least one maximum in the chromatographic range of temperature. As a consequence, a great amount of experimental data is required for a correct thermodynamic interpretation of the chromatographic retention.

  13. High-resolution gas chromatographic profiles of volatile organic compounds produced by microorganisms at refrigerated temperatures.

    PubMed Central

    Lee, M L; Smith, D L; Freeman, L R

    1979-01-01

    Three different strains of bacteria isolated from spoiled, uncooked chicken were grown in pure culture on Trypticase soy agar supplemented with yeast extract. The volatile organic compounds produced by each culture were concentrated on a porous polymer precolumn and analyzed by high-resolution gas chromatographic mass spectrometry. Twenty different compounds were identified. Both qualitative and quantitative differences in the chromatographic profiles from each culture were found. PMID:104660

  14. New Method for Evaluating Irreversible Adsorption and Stationary Phase Bleed in Gas Chromatographic Capillary Columns

    SciTech Connect

    Wright, Bob W.; Wright, Cherylyn W.

    2012-10-26

    A novel method for the evaluation of gas chromatographic (GC) column inertness has been developed using a tandem GC approach. Typically column inertness is measured by analyte peak shape evaluation. In general, silica, glass, and metal surfaces are chemically reactive and can cause analyte adsorption, which typically is observed as chromatographic peak tailing. Adsorption processes produce broad, short chromatographic peaks that confound peak area determinations because a significant portion can reside in the noise. In addition, chromatographic surfaces and stationary phases can irreversibly adsorb certain analytes without obvious degradation of peak shape. The inertness measurements described in this work specifically determine the degree of irreversible adsorption behavior of specific target compounds at levels ranging from approximately 50 picograms to 1 nanogram on selected gas chromatographic columns. Chromatographic columns with 5% phenylmethylsiloxane, polyethylene glycol (wax), trifluoropropylsiloxane, and 78% cyanopropylsiloxane stationary phases were evaluated with a variety of phosphorus- and sulfur- containing compounds selected as test compounds due to their ease of adsorption and importance in trace analytical detection. In addition, the method was shown effective for characterizing column bleed.

  15. Comparison of physicochemical and gas chromatographic polarity measures for simple organic compounds.

    PubMed

    Héberger, Károly; Zenkevich, Igor G

    2010-04-23

    The comparison of different polarity measures (parameters, descriptors, variables, scales, etc.) indicates that evaluation of interrelations between these measures is important for better understanding and interpretation of chemical and/or analytical data, especially for chromatographic separation. The best linear correlation between gas chromatographic and non-chromatographic polarity descriptors is revealed for the first time: this pair of variables is the difference of gas chromatographic retention indices on standard polar and non-polar phases as well as the difference between non-dimensional indices of boiling points (known in chromatography since mid-1980s as dispersion indices) and indices of molar refractions. The correlation helps chromatographers to find preferable chemical variables (features) to understand better the separation phenomena and to find better correlations in QSRR models. Principal component analysis (PCA) of ten frequently applied polarity measures shows their similarity and, at the same time, it shows the absence of anomalies within the set of simple organic molecules. A novel ranking method for ten polarity parameters points out that the two most informative polarity measures are (i) the non-dimensional index for boiling point and (ii) the difference in chromatographic retention indices on standard polar and non-polar stationary phases. On the other hand, the hydrophobicity parameter, log P, sometimes considered as polarity parameter in HPLC seems to be the worst one in description of "polarity" in gas chromatography. Surprisingly, such polarity measures like dipole moment and permittivity used often in organic chemistry does not provide the best correlation with gas chromatographic polarity measures.

  16. Gas chromatograph-combustion system for 14C-accelerator mass spectrometry.

    PubMed

    McIntyre, Cameron P; Sylva, Sean P; Roberts, Mark L

    2009-08-01

    A gas chromatograph-combustion (GC-C) system is described for the introduction of samples as CO(2) gas into a (14)C accelerator mass spectrometry (AMS) system with a microwave-plasma gas ion source. Samples are injected into a gas chromatograph fitted with a megabore capillary column that uses H(2) as the carrier gas. The gas stream from the outlet of the column is mixed with O(2) and Ar gas and passed through a combustion furnace where the H(2) carrier gas and separated components are quantitatively oxidized to CO(2) and H(2)O. Water vapor is removed using a heated nafion dryer. The Ar carries the CO(2) to the ion source. The system is able to separate and oxidize up to 10 microg of compound and transfer the products from 7.6 mL/min of H(2) carrier gas into 0.2-1.0 mL/min of Ar carrier gas. Chromatographic performance and isotopic fidelity satisfy the requirements of the (14)C-AMS system for natural abundance measurements. The system is a significant technical advance for GC-AMS and may be capable of providing an increase in sensitivity for other analytical systems such as an isotope-ratio-monitoring GC/MS.

  17. Gas-chromatographic characterization of physicochemical properties of astatine compounds

    SciTech Connect

    Norseev, Yu.V.

    1995-07-01

    The organoastatine compounds obtained were identified by gas-liquid chromatography on a specially designed gas radiochromatograph with detection of eluted compounds both by their radioactivity and by thermal conductivity. Gas-liquid chromatography is the most efficient method for separation and identification of volatile organoastatine compounds.

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

    PubMed

    Valentin, J R

    1989-03-01

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

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

    NASA Technical Reports Server (NTRS)

    Valentin, J. R.

    1989-01-01

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

  20. Gas chromatographic-mass spectrometric analysis of volatile amines produced by several strains of Clostridium.

    PubMed

    Pons, J L; Rimbault, A; Darbord, J C; Leluan, G

    1985-02-08

    A gas chromatographic--mass spectrometric technique is proposed for the analysis of volatile amines which were isolated from Clostridium cultures by vacuum distillation and concentrated as hydrochloride salts. Headspace sampling after alkalinization of the salts under vacuum was the most suitable for subsequent gas chromatographic analysis. With ammonia-loaded helium as carrier gas, methylamines were separated on 4.8% PEG 2OM + 0.3% potassium hydroxide on Carbopack B, and other volatile amines on 28% Pennwalt 223 + 4% potassium hydroxide on Gas-Chrom R. Bacterial volatile amines (dimethylamine, trimethylamine, isobutylamine, 3-methylbutylamine, etc.) were detected with a flame-ionization detector and identified by gas chromatography--mass spectrometry in electron-impact and chemical ionization modes.

  1. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT, EXPLOSIVES DETECTION TECHNOLOGY, SRI INSTRUMENTS, MODEL 8610C, GAS CHROMATOGRAPH/THERMIONIC IONIZATION DETECTION

    EPA Science Inventory

    The SRI Model 86 1 OC gas chromatograph (GC) is a transportable instrument that can provide on-site analysis of soils for explosives. Coupling this transportable gas chromatograph with a thermionic ionization detector (TID) allows for the determination of explosives in soil matri...

  2. Characterization of Gas Chromatographic Liquid Phases Using McReynolds Constants. An Experiment for Instrumental Analysis Laboratory.

    ERIC Educational Resources Information Center

    Erskine, Steven R.; And Others

    1986-01-01

    Describes a laboratory experiment that is designed to aid in the understanding of the fundamental process involved in gas chromatographic separations. Introduces the Kovats retention index system for use by chemistry students to establish criteria for the optimal selection of gas chromatographic stationary phases. (TW)

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

    NASA Technical Reports Server (NTRS)

    Carle, G. C.

    1972-01-01

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

  4. NEAR-CONTINUOUS MEASUREMENT OF HYDROGEN SULFIDE AND CARBONYL SULFIDE BY AN AUTOMATIC GAS CHROMATOGRAPH

    EPA Science Inventory

    An automatic gas chromatograph with a flame photometric detector that samples and analyzes hydrogen sulfide and carbonyl sulfide at 30-s intervals is described. Temperature programming was used to elute trace amounts of carbon disulfide present in each injection from a Supelpak-S...

  5. 40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon...

  6. 40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon...

  7. 40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon...

  8. Chiral porous organic frameworks for asymmetric heterogeneous catalysis and gas chromatographic separation.

    PubMed

    Dong, Jinqiao; Liu, Yan; Cui, Yong

    2014-12-11

    Three chiral robust diene-based porous organic frameworks (POFs) are prepared. POF- is shown to be an efficient heterogeneous catalyst after metallation for asymmetric conjugation addition with up to 93% ee, and it can also function as a new chiral stationary phase for gas chromatographic separation of racemates.

  9. Development of and fabrication of high resolution gas chromatographic capillary columns

    NASA Technical Reports Server (NTRS)

    Zlatkis, A.

    1982-01-01

    Gas chromatographic columns which are used in the trace gas analyzer (TGA) for the space shuttle are coated with a polyoxyethylene lauryl ether. This stationary phase is of medium polarity and has a temperature limit of 160 C. A polymer for this application which has an improved thermal stability is investigated. The use of fused silica capillary columns with specially bonded phases as well as an introduction system (on column) was also studied.

  10. Derivatization in gas chromatographic determination of phenol and aniline traces in aqueous media

    NASA Astrophysics Data System (ADS)

    Gruzdev, I. V.; Zenkevich, I. G.; Kondratenok, B. M.

    2015-06-01

    Substituted anilines and phenols are the most common hydrophilic organic environmental toxicants. The principles of gas chromatographic determination of trace amounts of these compounds in aqueous media at concentrations <=0.1 μg litre-1 based on synthesis of their derivatives (derivatization) directly in the aqueous phase are considered. Conversion of relatively hydrophilic analytes into more hydrophobic derivatives makes it possible to achieve such low detection limits and optimize the protocols of extractive preconcentration and selective chromatographic detection. Among the known reactions, this condition is best met by electrophilic halogenation of compounds at the aromatic moiety. The bibliography includes 177 references.

  11. Indirect gas chromatographic measurement of water for process streams

    SciTech Connect

    Barbour, F.A.

    1993-05-01

    This project was conducted to develop a moisture measurement method for process gas streams of fossil fuels. Objective was to from pyrolysis to measure the molar concentration of water in a gas stream without flow measurements. The method developed has been incorporated into the hydrocarbon gas analysis method currently used at Western Research Institute. A literature search of types of direct measuring moisture sensors was conducted, and a list of sensors available is given; most of them could not survive in the environment of the process streams. Indirect methods of measuring water involve changing the water via reaction to a compound that can be more readily measured. These methods react water with various reagents to form hydrogen, acetylene, and acetone. The method chose for this study uses a calcium carbide reaction column to convert the water present in the gas stream to acetylene for analysis. Relative deviation for the daily determination of water varied from 0.5 to 3.4%. The method chosen was tested for linearity over a wide range of gas stream water content. Response over 2 to 15 mole % water appears to be linear with a correlation coefficient of 0.991.

  12. The Construction of a Simple Pyrolysis Gas Chromatograph.

    ERIC Educational Resources Information Center

    Hedrick, Jack L.

    1982-01-01

    Describes a simple and inexpensive pyrolysis gas chromatography (PGC) system constructed from items available in undergraduate institutions. The system is limited, accepting only liquid samples and pyrolyzing "on the fly" rather than statically and not allowing for reductive pyrolysis. Applications, experiments, and typical results are included.…

  13. Development of gas chromatographic system for dissolved organic carbon analysis in seawater

    SciTech Connect

    Chipman, D.W.; Takahashi, T.

    1992-12-01

    During the first six months of this two-year grant, we have completed the construction of the analytical portion of a prototype gas chromatograph-based system for the analysis of dissolved organic carbon in seawater. We also have begun testing the procedures to be used to cryogenically concentrate and transfer carbon dioxide from the oxidizing atmosphere of the high-temperature furnace into the reducing hydrogen carrier gas of the gas chromatograph. During the second half of the first year, we will construct the high-temperature catalytic oxidation furnace and test the entire system on laboratory-prepared aqueous solutions of various organic compounds. Also during this period, we will take part in an initial scoping study within the Cape Hatteras field area on board the R/V Gyre. This study will involve both the collection of samples of seawater for organic and inorganic carbon analysis and the measurement of surface-water pCO[sub 2].

  14. Development of gas chromatographic system for dissolved organic carbon analysis in seawater. Annual progress report

    SciTech Connect

    Chipman, D.W.; Takahashi, T.

    1992-12-01

    During the first six months of this two-year grant, we have completed the construction of the analytical portion of a prototype gas chromatograph-based system for the analysis of dissolved organic carbon in seawater. We also have begun testing the procedures to be used to cryogenically concentrate and transfer carbon dioxide from the oxidizing atmosphere of the high-temperature furnace into the reducing hydrogen carrier gas of the gas chromatograph. During the second half of the first year, we will construct the high-temperature catalytic oxidation furnace and test the entire system on laboratory-prepared aqueous solutions of various organic compounds. Also during this period, we will take part in an initial scoping study within the Cape Hatteras field area on board the R/V Gyre. This study will involve both the collection of samples of seawater for organic and inorganic carbon analysis and the measurement of surface-water pCO{sub 2}.

  15. Estimation of the vapor pressure of petroleum distillate fractions from gas chromatographic data

    SciTech Connect

    Eggertsen, F.T.; Nygard, N.R.; Nickoley, L.D.

    1980-11-01

    The vapor pressure of petroleum distillate fractions is estimated conveniently by applying ideal gas and solution laws to gas chromatographic data. The vapor pressure is computed as a summation of the partial pressures for carbon number groups in the chromatogram, each partial pressure being derived as the product of mole fraction, determined from the chromatogram, and saturation pressure, calculated using the Antoine equation. A rapid method of computation with a programmable calculator was used. The method assumes approximate conformance to Raoult's and Dalton's laws relating to partial pressures from a solution. The results generally agree well with values obtained manometrically. Advantages of the method are the general availability of suitable gas chromatographic equipment, convenience and speed of the procedure and calculations, applicability over a wide range of volatility, freedom from temperature equilibration problems, and small sample requirement. 4 figures, 6 tables.

  16. HAPSITE(Trademark) Gas Chromatograph/Mass Spectrometer Variability Assessment

    DTIC Science & Technology

    2005-07-27

    in an uncharacterized chemical environment that involves chemical warfare agents (CWA) or toxic industrial chemicals ( TIC ). Gas Chromatography/Mass...Research Institute (MRI) in Kansas City, Missouri conducted a study to optimize the use of a tri-bed concentrator with TIC . The tni-bed concentrator...The remaining 81 TIC were added based on a Navy threat assessment of chemicals that could be used in a terrorist attack or potentially hazardous

  17. Gas Chromatographic Analysis of Acidic Indole Auxins in Nicotiana1

    PubMed Central

    Bayer, Margret H.

    1969-01-01

    Acidic indole auxins have been extracted from N. glauca, N. langsdorffii and their 2 tumor-prone 4n- and 2n-hybrids. After purification of the extracts and thin-layer chromatography, acidic indoles were subjected to esterification and gas chromatography. The esters of 4 indole acids were detected and determined: indole-3-acetic acid, indole-3-carboxylic acid, indole-3-propionic acid and indole-3-butyric acid. The indolic nature of fractionated samples was confirmed by spectrophotofluorometry and the physiological significance of the indole esters proven in a biotest. A substantial increase in extractable indole-3-butyric acid in the tumor-prone hybrids suggests an additional pathway of auxin synthesis in these tissues. PMID:5774173

  18. Gas chromatographic technologies for the analysis of essential oils.

    PubMed

    Marriot, P J; Shellie, R; Cornwell, C

    2001-11-30

    Essential oil analysis has basically had one technical goal: to achieve the best possible separation performance by using the most effective, available technology of the day. The result achieved from this may then be used to answer the research or industrial analysis questions which necessitated the analysis. This may be for comparative purposes, where one oil is contrasted with other(s) for quality control or investigation of adulteration, to discover new components, or to characterise the chemical classes of compounds present. Clearly, today the analyst turns to chromatography as the provider of separation and then may supplement that with mass spectrometry to aid identification. The power of GC-MS means that advances in both the separation technique, and improvements in mass spectrometry detection - along with improved data handling tools - will immediately be relevant to the essential oil area. This present review outlines the developmental nature of instrumental approaches to essential oil analysis using gas chromatography. Mass spectrometry will be included to the extent that it represents the hyphenation of choice for most analysts when analysing essential oils. Thus single-column and multi-dimensional analysis will be covered, as will sample handling or introduction techniques prior to the analysis step, where these techniques provide some measure of separation. The recent demonstration of comprehensive gas chromatography will be discussed as the potentially most powerful separation method for essential oils. This brief review is not intended to be a comprehensive dissertation on the field of essential oil analysis since that would require sufficient space to occupy a book in its own right. Rather, it will outline selected considerations and developments, to help explain where new technology has been applied to advantage in this field.

  19. Highly sensitive gas chromatographic determination of ethanol in human urine samples.

    PubMed

    Zilly, Michael; Langmann, Peter; Lenker, Ulrike; Satzinger, Verena; Schirmer, Diana; Klinker, Hartwig

    2003-12-25

    In order to evaluate recent alcohol consumption, a very sensitive and specific gas chromatographic method for ethanol determination in human urine samples was developed. The non-invasive method was performed without any pretreatment and carried out on a Stabilwax capillary column, 30 m x 0.53 mm x 1.0 microm film thickness. Helium was used as carrier gas with a constant inlet pressure of 27.72 kPa (0.277 bar) and a flame ionization detector (FID). Quantification was performed with the use of acetonitrile as an internal standard (IS). The calibration curve was linear throughout the concentration range from 0.5 to 500 mg/l. The calculated intra- and inter-day coefficients of variation were below 8%. A clear chromatographic separation of ethanol from methanol, acetone, 1-propanol and 2-propanol was achieved.

  20. Gas chromatographic analysis of polyhydroxybutyrate in activated sludge: a round-robin test.

    PubMed

    Baetens, D; Aurola, A M; Foglia, A; Dionisi, D; van Loosdrecht, M C M

    2002-01-01

    Polyhydroxyalkanoates (PHA) and poly-beta-hydroxybutyrate (PHB) in particular have become compounds which is routinely investigated in wastewater research. The PHB analysis method has only recently been applied to activated sludge samples where PHA contents might be relatively low. This urges the need to investigate the reproducibility of the gas chromatographic method for PHB analysis. This was evaluated in a round-robin test in 5 European laboratories with samples from lab-scale and full-scale enhanced biological phosphorus removal systems. It was shown that the standard deviation of measurements in each lab and the reproducibility between the labs was very good. Experimental results obtained by different laboratories using this analysis method can be compared. Sludge samples with PHB contents varying between 0.3 and 22.5 mg PHB/mg sludge were analysed. The gas chromatographic method allows for PHV, PH2MB and PH2MV analysis as well.

  1. Portable gas chromatograph mass spectrometer for on-site chemical analyses

    DOEpatents

    Haas, Jeffrey S.; Bushman, John F.; Howard, Douglas E.; Wong, James L.; Eckels, Joel D.

    2002-01-01

    A portable, lightweight (approximately 25 kg) gas chromatograph mass spectrometer, including the entire vacuum system, can perform qualitative and quantitative analyses of all sample types in the field. The GC/MS has a conveniently configured layout of components for ease of serviceability and maintenance. The GC/MS system can be transported under operating or near-operating conditions (i.e., under vacuum and at elevated temperature) to reduce the downtime before samples can be analyzed on-site.

  2. Gas chromatographic determination of pesticide residues in white mustard.

    PubMed

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

    2015-04-15

    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%).

  3. Gas chromatographic column for the storage of sample profiles

    NASA Technical Reports Server (NTRS)

    Dimandja, J. M.; Valentin, J. R.; Phillips, J. B.

    1994-01-01

    The concept of a sample retention column that preserves the true time profile of an analyte of interest is studied. This storage system allows for the detection to be done at convenient times, as opposed to the nearly continuous monitoring that is required by other systems to preserve a sample time profile. The sample storage column is essentially a gas chromatography column, although its use is not the separation of sample components. The functions of the storage column are the selective isolation of the component of interest from the rest of the components present in the sample and the storage of this component as a function of time. Using octane as a test substance, the sample storage system was optimized with respect to such parameters as storage and readout temperature, flow rate through the storage column, column efficiency and storage time. A 3-h sample profile was collected and stored at 30 degrees C for 20 h. The profile was then retrieved, essentially intact, in 5 min at 130 degrees C.

  4. Comparison of gas chromatographic hyphenated techniques for mercury speciation analysis.

    PubMed

    Nevado, J J Berzas; Martín-Doimeadios, R C Rodríguez; Krupp, E M; Bernardo, F J Guzmán; Fariñas, N Rodríguez; Moreno, M Jiménez; Wallace, D; Ropero, M J Patiño

    2011-07-15

    In this study, we evaluate advantages and disadvantages of three hyphenated techniques for mercury speciation analysis in different sample matrices using gas chromatography (GC) with mass spectrometry (GC-MS), inductively coupled plasma mass spectrometry (GC-ICP-MS) and pyrolysis atomic fluorescence (GC-pyro-AFS) detection. Aqueous ethylation with NaBEt(4) was required in all cases. All systems were validated with respect to precision, with repeatability and reproducibility <5% RSD, confirmed by the Snedecor F-test. All methods proved to be robust according to a Plackett-Burnham design for 7 factors and 15 experiments, and calculations were carried out using the procedures described by Youden and Steiner. In order to evaluate accuracy, certified reference materials (DORM-2 and DOLT-3) were analyzed after closed-vessel microwave extraction with tetramethylammonium hydroxide (TMAH). No statistically significant differences were found to the certified values (p=0.05). The suitability for water samples analysis with different organic matter and chloride contents was evaluated by recovery experiments in synthetic spiked waters. Absolute detection and quantification limits were in the range of 2-6 pg for GC-pyro-AFS, 1-4 pg for GC-MS, with 0.05-0.21 pg for GC-ICP-MS showing the best limits of detection for the three systems employed. However, all systems are sufficiently sensitive for mercury speciation in environmental samples, with GC-MS and GC-ICP-MS offering isotope analysis capabilities for the use of species-specific isotope dilution analysis, and GC-pyro-AFS being the most cost effective alternative.

  5. A Gas Chromatograph/Mass Spectrometer System for UltraLow-Emission Combustor Exhaust Studies

    NASA Technical Reports Server (NTRS)

    Brabbs, Theodore A.; Wey, Chowen Chou

    1996-01-01

    A gas chromatograph (GC)/mass spectrometer (MS) system that allows the speciation of unburnt hydrocarbons in the combustor exhaust has been developed at the NASA Lewis Research Center. Combustion gas samples are withdrawn through a water-cooled sampling probe which, when not in use, is protected from contamination by a high-pressure nitrogen purge. The sample line and its connecting lines, filters, and valves are all ultraclean and are heated to avoid condensation. The system has resolution to the parts-per-billion (ppb) level.

  6. Optimization of the Finnigan MAT 5100 Capillary Gas Chromatograph-Mass Spectrometer for the Analysis of Polychlorinated Biphenyls.

    DTIC Science & Technology

    1986-11-01

    FINNIGAN MAT 5100 CAPILLARY GAS CHROMATOGRAPH-MASS SPECTROMETER FOR THE ANALYSIS OF POLYCHLORINATED BIPHENYLS J.A. Hiltz - J. Power ,¢., DJ : .,:.JAN 1 4...CAPILLARY GAS CHROMATOGRAPH-MASS SPECTROMETER FOR THE ANALYSIS OF POLYCHLORINATED BIPHENYLS J.A. Hiltz - J.J. Power November 1986 Approved by B.F. Peters A...INTRODUCTION The use of polychlorinated biphenyls (PCBs) as dielectric fluids in electrical transformers and capacitors has been commomplace over the

  7. Solid-phase microextraction-gas chromatographic determination of volatile monoaromatic hydrocarbons in soil.

    PubMed

    Zygmunt, B; Namiesnik, J

    2001-08-01

    Benzene, toluene, ethylbenzene, three isomers of xylene, and cumene have been isolated and enriched from soil samples by a combination of water extraction at room and elevated temperature and headspace-solid-phase microextraction before their gas chromatographic-mass spectrometric (GC-MS) determination. The conditions used for all stages of sample preparation and chromatographic analysis were optimized. Analytes sampled on a polydimethylsiloxane-coated solid-phase microextraction fiber were thermally desorbed in the split/splitless injector of a gas chromatograph (GC) coupled with a mass spectrometer (MS). The desorption temperature was optimized. The GC separation was performed in a capillary column. Detection limits were found to be of the order of ca. 1 ng g(-1). Relative recoveries of the analytes from soils were found to be highly dependent on soil organic-matter content and on compound identity; they ranged from ca 92 to 96% for sandy soil (extraction at room temperature) and from ca 27 to 55% for peaty soil (extraction at elevated temperature). A few real-world soil samples were analyzed; the individual monoaromatic hydrocarbon content ranged from below detection limits to 6.4 ng g(-1) for benzene and 8.1 for the total of p- + m-xylene.

  8. First Results From the Gas Chromatograph Mass Spectrometer (GCMS) Experiment on the Cassini-Huygens Probe

    NASA Technical Reports Server (NTRS)

    Niemann, Hasso B.; Demick, J.; Haberman, J.; Harpold, D.; Kasprzak, W.; Raaen, E.; Way, S.; Atreya, S.; Carignan, G.; Bauer, S.

    2005-01-01

    The Huygens Probe of the Cassini Huygens Mission entered the atmosphere of the moon Titan on January 14,2005. The GCMS was part of the instrument complement on the Probe to measure in situ the chemical composition of the atmosphere during the probe descent and to support the Aerosol Collector Pyrolyser (ACP) experiment by serving as detector for the pyrolization products. The GCMS employed a quadrupole mass filter with a secondary electron multiplier detection system and a gas sampling system providing continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic (GC) columns. The mass spectrometer employed five electron impact ion sources with available electron energies of either 70 or 25 eV. Three ion sources served as detectors for the GC columns and two were dedicated to direct atmosphere sampling and ACP gas sampling, respectively. The GCMS gas inlet was heated to prevent condensation, and served to evaporate surface constituents after impact.

  9. Screening of ground water samples for volatile organic compounds using a portable gas chromatograph

    USGS Publications Warehouse

    Buchmiller, R.C.

    1989-01-01

    A portable gas chromatograph was used to screen 32 ground water samples for volatile organic compounds. Seven screened samples were positive; four of the seven samples had volatile organic substances identified by second-column confirmation. Four of the seven positive, screened samples also tested positive in laboratory analyses of duplicate samples. No volatile organic compounds were detected in laboratory analyses of samples that headspace screening indicated to be negative. Samples that contained volatile organic compounds, as identified by laboratory analysis, and that contained a volatile organic compound present in a standard of selected compounds were correctly identified by using the portable gas chromatography. Comparisons of screened-sample data with laboratory data indicate the ability to detect selected volatile organic compounds at concentrations of about 1 microgram per liter in the headspace of water samples by use of a portable gas chromatography. -Author

  10. Structure, gas chromatographic measurement, and function of suberin synthesized by potato tuber tissue slices.

    PubMed

    Kolattukudy, P E; Dean, B B

    1974-07-01

    The polymeric material (suberin) of the wound periderm of potato tuber slices was analyzed after depolymerization with LiAIH(4) in tetrahydrofuran or BF(3) in methanol with the use of thin layer chromatography, chemical modification, and combined gas-liquid chromatography and mass spectrometry. Fatty acids (C(16) to C(26)), fatty alcohols (C(16) to C(26)), octadec-9-ene-1, 18-dioic acid, and 18-hydroxy-octadec-9-enoic acid were identified to be the major components. Based on the structural information that the two bifunctional C(18) molecules constituted a major portion of suberin, a gas chromatographic method of measuring suberization was developed. This method consisted of hydrogenolysis of powdered tissue followed by thin layer chromatography and gas chromatographic measurement of octadecene-1, 18-diol as the trimethylsilyl ether. With this assay it was shown that the development of resistance to water loss by the tissue slices was directly proportional to the quantity of the bifunctional C(18) molecules, thus providing evidence that a function of suberin is prevention of water loss.

  11. Gas chromatographic determination of propionates as paranitrobenzyl ester in bakery products.

    PubMed

    Takatsuki, K; Sakai, K

    1982-07-01

    A procedure was developed to determine propionates used as mold inhibitors and preservatives in bakery products. Propionates were extracted from the sample with water alkalinized by potassium carbonate. Water was evaporated, and the residue was reacted with paranitrobenzyl bromide in dimethyl-formamide-water (90 + 10) at room temperature to convert propionates to paranitrobenzyl ester, which was determined with a gas chromatograph equipped with a flame ionization detector. Bakery products, such as bread, sponge cake, cookies, and biscuits, were analyzed by this procedure. Recoveries from samples fortified with propionates ranged from 94 to 101%, with a standard deviation of 3.32. The concentrations determined were 50 to 2500 micrograms/g sample.

  12. Miniature triaxial metastable ionization detector for gas chromatographic trace analysis of extraterrestrial volatiles

    NASA Technical Reports Server (NTRS)

    Woeller, F. H.; Kojiro, D. R.; Carle, G. C.

    1984-01-01

    The present investigation is concerned with a miniature metastable ionization detector featuring an unconventional electrode configuration, whose performance characteristics parallel those of traditional design. The ionization detector is to be incorporated in a flight gas chromatograph (GC) for use in the Space Shuttle. The design of the detector is discussed, taking into account studies which verified the sensitivity of the detector. The triaxial design of the detector is compared with a flat-plate style. The obtained results show that the principal goal of developing a miniature, highly sensitive ionization detector for flight applications was achieved. Improved fabrication techniques will utilize glass-to-metal seals and brazing procedures.

  13. [Gas chromatographic analysis of methyl methacrylate and methanol in its esterification mixture].

    PubMed

    Wu, C; Zeng, C

    1997-09-01

    A fast, simple and accurate gas chromatographic method is established for determining the content of methyl methacrylate (MMA) and methanol in the esterification mixture of methacrylic acid with methanol in the presence of sulfuric acid. In the measurement, polyethylene glycol-20M/sodium hydroxide was adopted as liquid phase, coated on the acid-washed 201 pink support. n-Heptane was used as the internal standard and the correction factors of MMA and methanol obtained were 1.65 and 4.10, respectively. It is significant for this method to be used to control MMA production by acetone cyanohydrin method and to improve the production technology.

  14. Gas chromatograph analysis on closed air and nitrogen oxide storage atmospheres of recalcitrant seeds of Quercus Alba

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  15. Headspace gas chromatographic method for determination of methyl bromide in food ingredients

    SciTech Connect

    DeVries, J.W.; Broge, J.M.; Schroeder, J.P.; Bowers, R.H.; Larson, P.A.; Burns, N.M.

    1985-11-01

    A headspace gas chromatographic (GC) method, which can be automated, has been developed for determination of methyl bromide. This method has been applied to wheat, flour, cocoa, and peanuts. Samples to be analyzed are placed in headspace sample vials, water is added, and the vials are sealed with Teflon-lined septa. After an appropriate equilibration time at 32 degrees C, the samples are analyzed within 10 h. A sample of the headspace is withdrawn and analyzed on a gas chromatograph equipped with an electron capture detector (ECD). Methyl bromide levels were quantitated by comparison of peak area with a standard. The standard was generated by adding a known amount of methyl bromide to a portion of the matrix being analyzed and which was known to be methyl bromide free. The detection limit of the method was 0.4 ppb. The coefficient of variation (CV) was 6.5% for wheat, 8.3% for flour, 3.3% for cocoa, and 11.6% for peanuts.

  16. Gas chromatographic investigation of volatile nitrogen containing bases of Antarctic krill Euphausia superba Dana.

    PubMed

    Svetlova, N I; Golovnya, R V; Zhuravleva, I L; Grigorieva, D N; Samusenko, A L

    1985-01-01

    The composition of the volatile nitrogen-containing bases of fresh-caught Antarctic krill E. superba has been investigated by gas chromatography. The analysis was carried out on three packed columns with Apiezon L, Triton X-305, PEG-1000 and one glass capillary column with Triton X-305. The components were identified by standardless gas chromatographic method with a special computer program. No less than 63 compounds have been found and 54 compounds have been identified, among these primary, secondary and tertiary aliphatic amines as well as heterocyclic bases. The presence of 5 compounds has been confirmed by GC/MS technique. Analysis with the help of a specific flame-photometric detector has shown the presence of 9 bi-functional nitrogen- and sulfur-containing compounds.

  17. Gas chromatographic determination of polysaccharide gums in foods after hydrolysis and derivatization.

    PubMed

    Lawrence, J F; Iyengar, J R

    1985-12-20

    A gas chromatographic method was evaluated for the determination of food grade gums in dairy products, salad dressings and meat sauces. The gums studied were tragacanth, karaya, ghatti, carob, guar, arabic and xanthan gum. The extraction method included removal of fat followed by starch degradation then precipitation of protein. The isolated gums were hydrolysed with trifluoroacetic acid and the resulting neutral monosaccharides converted to their aldonitrile acetate derivatives for determination by gas chromatography. Recoveries from thirteen different commodities averaged 85%. However, the recovery of guar gum from ice cream and cold pack cheese was 42 and 50%, respectively. In a comparison of enzyme hydrolysis and iodine complexation for the removal of starch the former was simpler and provided cleaner extracts than the iodine treatment. Both gave similar results.

  18. Quantitative gas chromatographic analysis of volatile fatty acids in spent culture media and body fluids.

    PubMed Central

    van den Bogaard, A E; Hazen, M J; Van Boven, C P

    1986-01-01

    Gas chromatographic analysis of volatile fatty acids for identification of obligately anaerobic bacteria and for presumptive diagnosis of anaerobic infections is now widely practiced. However, it is difficult to compare data because only a qualitative analysis is done or only chromatograms are presented instead of quantitative data on volatile fatty acid production. We compared three stationary phases for volatile fatty acid analysis of aqueous solutions and four methods of pretreating samples for gas chromatography. Quantitative analysis could be done accurately by using Carbowax as the stationary phase after pretreatment of spent culture media with Dowex columns. If only qualitative analysis is required (e.g., for presumptive diagnosis of anaerobic infections), ether extraction and headspace analysis are equally suitable. The overall variation coefficient for volatile fatty acid production by four reference strains of obligately anaerobic bacteria after 24 h of incubation was approximately 10%. PMID:3958144

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

    DOEpatents

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

    1982-04-26

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

  20. Gas chromatographic separation of diastereomeric isoprenoids as molecular markers of oil pollution.

    PubMed

    Berthou, F; Friovourt, M P

    1981-12-18

    By means of high-performance glass capillary gas chromatography (GC), diastereomeric isoprenoids were resolved into double peaks. The retention indices on three liquid phases and the mass spectra of the diastereoisomers were almost similar. The leading GC peaks represent the isoprenoids of fossil origin, while the rear peaks correspond to those of recent origin. Computerized gas chromatography-mass spectrometry was used for fingerprinting isoprenoids in different samples. The mass fragmentation patterns were characteristic of the branched alkanes. Hydrocarbon mixtures from four crude oil spills in the sea and from polluted and oil-free oyster tissues were investigated. The relative ratios of n-alkanes/pristane or phytane were shown to be strongly dependent on the chromatographic resolution of the isoprenoid peaks. It is suggested that the double GC peaks in the isoprenoid series are an unmistakable sign of oil pollution.

  1. Interfacing a robotic station with a gas chromatograph for the full automation of the determination of organochlorine pesticides in vegetables

    SciTech Connect

    Torres, P.; Luque de Castro, M.D.

    1996-12-31

    A fully automated method for the determination of organochlorine pesticides in vegetables is proposed. The overall system acts as an {open_quotes}analytical black box{close_quotes} because a robotic station performs the prelimninary operations, from weighing to capping the leached analytes and location in an autosampler of an automated gas chromatograph with electron capture detection. The method has been applied to the determination of lindane, heptachlor, captan, chlordane and metoxcychlor in tea, marjoram, cinnamon, pennyroyal, and mint with good results in most cases. A gas chromatograph has been interfaced to a robotic station for the determination of pesticides in vegetables. 15 refs., 4 figs., 2 tabs.

  2. Simultaneous gas chromatographic determination of four toxic gases generally present in combustion atmospheres.

    PubMed

    Endecott, B R; Sanders, D C; Chaturvedi, A K

    1996-01-01

    The measurement of combustion gases produced by burning aircraft cabin materials poses a continuing limitation for smoke toxicity research. Because toxic effects of gases depend on both their concentrations and the duration of exposure, frequent atmosphere sampling is necessary to define the gas concentration-exposure time curve. A gas chromatographic (GC) method was developed for the simultaneous analyses of carbon monoxide (CO), hydrogen sulfide (H2S), sulfur dioxide (SO2), and hydrogen cyanide (HCN). The method used an MTI M200 dual-column gas chromatograph equipped with 4-m molecular sieve-5A and 8-m PoraPlot-U wall-coated capillary columns and two low-volume, high-sensitivity thermal conductivity detectors. Detectability (in parts per million [ppm]) and retention times (in seconds) for the gases were as follows: CO, 100 ppm, 28 s; H2S, 50 ppm, 26 s; SO2, 125 ppm, 76 s; and HCN, 60 ppm, 108 s. The method was effective for determining these gases in mixtures and in the combustion atmospheres generated by burning wool (CO, HCN, and H2S) and modacrylic fabrics (CO and HCN). Common atmospheric gaseous or combustion products (oxygen, carbon dioxide, nitrogen, water vapor, and other volatiles) did not interfere with the analyses. However, filtration of the combustion atmospheres was necessary to prevent restriction of the GC sampling inlet by smoke particulates. The speed, sensitivity, and selectivity of this method make it suitable for smoke toxicity research and for evaluating performance of passenger protective breathing equipment. Also, this method can potentially be modified to analyze these gases when they are liberated from biosamples.

  3. Gas chromatographic determination of volatile congeners in spirit drinks: interlaboratory study.

    PubMed

    Kelly, J; Chapman, S; Brereton, P; Bertrand, A; Guillou, C; Wittkowski, R

    1999-01-01

    An interlaboratory study of a gas chromatographic (GC) method for the determination of volatile congeners in spirit drinks was conducted; 31 laboratories from 8 countries took part in the study. The method uses GC with flame ionization detection and incorporates several quality control measures which permit the choice of chromatographic system and conditions to be selected by the user. Spirit drink samples were prepared and sent to participants as 10 blind duplicate or split-level test materials for the determination of 1,1-diethoxyethane (acetal), 2-methylbutan-1-ol (active amyl alcohol), 3-methylbutan-1-ol (isoamyl alcohol), methanol (methyl alcohol), ethyl ethanoate (ethyl acetate), butan-1-ol (n-butanol), butan-2-ol (sec-butanol), 2-methylpropan-1-ol (isobutyl alcohol), propan-1-ol (n-propanol), and ethanal (acetaldehyde). The precision of the method for 9 of the 10 analytes was well within the range predicted by the Horwitz equation. The precision of the most volatile analyte, ethanal, was just above statistically predicted levels. This method is recommended for official regulatory purposes.

  4. Gas-chromatographic measurement of carboxyhemoglobin in blood from mothers and newborns.

    PubMed

    Fogh-Andersen, N; Eriksen, P S; Grinsted, J; Siggaard-Andersen, O

    1988-01-01

    HbCO in blood sampled from 20 mothers and newborns immediately after birth was measured with a new, simple gas-chromatographic method for CO. The mean ratio of HbCO to total hemoglobin for 13 non-smoking mothers did not differ significantly from that for their infants (mean 0.38%, SD 0.26% vs 0.38%, SD 0.13%), but the HbCO ratio varied more in the mothers than in the infants (P less than 0.05). The infants of seven cigarette-smoking mothers, tobacco-abstinent for 7 h during labor, had higher HbCO ratios than their mothers (mean 1.88% vs 1.28%, P less than 0.05). The results are in harmony with the concept of equal affinities of fetal and adult hemoglobin for CO and a long time for passage of CO across the placenta.

  5. Correlation of the "EMIT" antiepileptic drug assay with a gas liquid chromatographic method.

    PubMed

    Legaz, M; Raisys, V A

    1976-02-01

    Many methodologies have been developed for determining anticonvulsant drug levels in human serum. Unfortunately, most procedures are either time consuming or subject to a variety of interferring substances. The "Enzyme Multiplied Immunoassay Technique" (EMIT) system has been evaluated for its speed, sensitivity, accuracy, and precision. When compared with a gas-liquid chromatographic procedure, the EMIT assay appeared to yield results which were statistically comparable for the drugs diphenylhydantoin, phenobarbital, and primidone. The EMIT assay also demonstrated no significant interference when challenged with extraordinarily high levels of potentially cross reacting drugs. Results obtained with the EMIT assay correlated well with GLC data and rank it as an attractive alternative to many of the existing procedures now being used.

  6. The current practice in the application of chemometrics for correlation of sensory and gas chromatographic data.

    PubMed

    Seisonen, Sirli; Vene, Kristel; Koppel, Kadri

    2016-11-01

    A lot of research has been conducted in correlating the sensory properties of food with different analytical measurements in recent years. Various statistical methods have been used in order to get the most reliable results and to create prediction models with high statistical performance. The current review summarises the latest practices in the field of correlating attributes from sensory analysis with volatile data obtained by gas chromatographic analysis. The review includes the origin of the data, different pre-processing and variable selection methods and finally statistical methods of analysis and validation. Partial least squares regression analysis appears as the most commonly used statistical method in the area. The main shortcomings were identified in the steps of pre-processing, variable selection and also validation of models that have not gained enough attention. As the association between volatiles and sensory perception is often nonlinear, future studies should test the application of different nonlinear techniques.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  8. Bio-sample preparation and gas chromatographic determination of benzodiazepines--a review.

    PubMed

    Uddin, Mohammad Nasir; Samanidou, Victoria F; Papadoyannis, Ioannis N

    2013-08-01

    Benzodiazepines have become commonly prescribed medicines worldwide in the therapy of anxiety, sleep disorders and convulsive attacks because they are relatively safe, with mild side effects. The availability of rapid, sensitive and selective analytical methods is essential for the determination of these drugs in clinical and forensic cases. Benzodiazepines are usually present at trace levels (μg/mL or ng/mL) in a complex biological matrix, and the potentially interfering compounds need to be removed before analysis. Therefore, a sample preparation technique is often mandatory, both to extract the drugs of interest from the matrices and to increase their concentration. An extended and comprehensive review is presented herein, focusing on bio-sample preparation (pretreatment, extraction and derivatization) and gas chromatographic methods applied for the quantification of 1,4-benzodiazepines.

  9. Thermal Modulation Methods To Improve the Efficiency of a Gas Chromatograph

    NASA Technical Reports Server (NTRS)

    Valentin, J. R.; Dimandja, J. D.; Do, M. T.; Kaljurand, M.; Chang, Sherwood (Technical Monitor)

    1995-01-01

    Thermal modulation techniques can be used to improve capacity, resolution, and time of analysis of a gas chromatograph. Two of-the techniques developed in our laboratories include using a GC column to store a sample (sample storage system) and applying temperature programming directly onto the wall of a capillary column. The storage system developed allowed the continuous collection of a sample profile for about 3 hours and storing it for as long as 20 hours. Thereafter, the samples were eluted maintaining the individual characteristics of the components present in it. Moreover, temperature programming was done directly on a capillary column improving the time of analysis and resolution of a mixture containing light hydrocarbons.

  10. Linear solvation energy relationships as classifiers in non-target analysis - a gas chromatographic approach.

    PubMed

    Ulrich, Nadin; Mühlenberg, Jana; Retzbach, Heiko; Schüürmann, Gerrit; Brack, Werner

    2012-11-16

    Linear solvation energy relationships (LSERs) are applied as classifiers to predict the logarithmic retention factors logk from the structures of candidate compounds in non-target analysis. By comparison of the predicted value with the experimentally determined logk, progressive exclusion of candidates is done. The approach is based on the determination of stationary phase parameters to describe ten different gas chromatographic columns under four isothermal conditions. To demonstrate retention prediction and the application of the classifier model, twelve compounds with the molecular formula C(12)H(10)O(2) were selected, while experimental logk values were compared to the predicted values and exclusion of potential candidate compounds was performed. The analytical power of the approach was demonstrated on the basis of experimentally determined compound descriptors achieved from gas chromatographic measurements. The prediction got less accurate when calculated compound descriptors were employed. For the time being insufficient precision in estimating the descriptors limits the possibility to exclude candidate compounds in non-target analysis. It is expected that new approaches to estimate compound descriptors, will improve this situation. At present, the insufficient accuracy of descriptor estimates can be dealt with larger prognosis intervals. Furthermore, the combination of two stationary phases with corresponding retention prediction further advanced the exclusion of potential candidates. The most appropriate pair of stationary phases was selected by the application of four different orthogonal strategies. In addition, the classifier was applied for a validation set with different molecular composition, where column selection was considered on the basis of the differences in the compound descriptors of the corresponding candidate compounds.

  11. Convenient headspace gas chromatographic determination of azide in blood and plasma.

    PubMed

    Meatherall, Robert; Palatnick, Wes

    2009-10-01

    Azide in human blood and plasma samples was derivatized with propionic anhydride in a headspace vial without prior sample preparation. The reaction proceeds quickly at room temperature to form propionyl azide. A portion of the headspace was assayed by gas chromatography with a nitrogen-phosphorus detector. In the heated injector of the gas chromatograph, the propionyl azide undergoes thermal rearrangement, forming ethyl isocyanate, which is subsequently chromatographed and detected. Propionitrile was used as the internal standard. The method is linear to at least 20 microg/mL. Limit of quantitation was 0.04 microg/mL, and the within-run coefficient of variation was 5.6% at 1 microg/mL. There was no interference from cyanide. A fatality report in which blood and plasma azide concentrations from a 59-year-old man were monitored for 24 h following the ingestion of an unknown amount of sodium azide is presented. The patient became critically ill after his self-inflicted sodium azide ingestion. He was intubated and treated with vasopressors and aggressive supportive care, including extracorporeal membrane oxygenation therapy, in the intensive care facility but died from neurological brain damage secondary to anoxia. On admission, 1.4 h after ingestion, his azide level was 5.6 microg/mL (blood); shortly thereafter, it had risen to 13.7 microg/mL (plasma) and, subsequently, was projected to have been eliminated by 16.7 h. No azide was detected in the postmortem blood and vitreous humor.

  12. Development of micromachined preconcentrators and gas chromatographic separation columns by an electroless gold plating technology

    NASA Astrophysics Data System (ADS)

    Kuo, C.-Y.; Chen, P.-S.; Chen, H.-T.; Lu, C.-J.; Tian, W.-C.

    2017-03-01

    In this study, a simple process for fabricating a novel micromachined preconcentrator (μPCT) and a gas chromatographic separation column (μSC) for use in a micro gas chromatograph (μGC) using one photomask is described. By electroless gold plating, a high-surface-area gold layer was deposited on the surface of channels inside the μPCT and μSC. For this process, (3-aminopropyl) trimethoxysilane (APTMS) was used as a promoter for attaching gold nanoparticles on a silicon substrate to create a seed layer. For this purpose, a gold sodium sulfite solution was used as reagent for depositing gold to form heating structures. The microchannels of the μPCT and μSC were coated with the adsorbent and stationary phase, Tenax-TA and polydimethylsiloxane (DB-1), respectively. μPCTs were heated at temperatures greater than 280 °C under an applied electrical power of 24 W and a heating rate of 75 °C s‑1. Repeatable thermal heating responses for μPCTs were achieved; good linearity (R 2  >  0.9997) was attained at three heating rates for the temperature programme for the μSC (0.2, 0.5 and 1 °C s‑1). The volatile organic compounds (VOCs) toluene and m-xylene were concentrated over the μPCT by rapid thermal desorption (peak width of half height (PWHH)  <1.5 s) preconcentration factors for both VOCs are  >7900. The VOCs acetone, benzene, toluene, m-xylene and 1,3,5-trimethylbenzene were also separated on the μSC as evidenced by their different retention times (47–184 s).

  13. Design and Performance of a Gas Chromatograph for Automatic Monitoring of Pollutants in Ambient Air

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

    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.

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

    SciTech Connect

    Mott, J.

    1995-12-31

    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{sub 2}) operation, and detection to the part-per billion levels.

  15. Screening Brazilian C gasoline quality: application of the SIMCA chemometric method to gas chromatographic data.

    PubMed

    Flumignan, Danilo Luiz; Tininis, Aristeu G; Ferreira, Fabrício de O; de Oliveira, José Eduardo

    2007-07-09

    A total of 2400 samples of commercial Brazilian C gasoline were collected over a 6-month period from different gas stations in the São Paulo state, Brazil, and analysed with respect to 12 physicochemical parameters according to regulation 309 of the Brazilian Government Petroleum, Natural Gas and Biofuels Agency (ANP). The percentages (v/v) of hydrocarbons (olefins, aromatics and saturated) were also determined. Hierarchical cluster analysis (HCA) was employed to select 150 representative samples that exhibited least similarity on the basis of their physicochemical parameters and hydrocarbon compositions. The chromatographic profiles of the selected samples were measured by gas chromatography with flame ionisation detection and analysed using soft independent modelling of class analogy (SIMCA) method in order to create a classification scheme to identify conform gasolines according to ANP 309 regulation. Following the optimisation of the SIMCA algorithm, it was possible to classify correctly 96% of the commercial gasoline samples present in the training set of 100. In order to check the quality of the model, an external group of 50 gasoline samples (the prediction set) were analysed and the developed SIMCA model classified 94% of these correctly. The developed chemometric method is recommended for screening commercial gasoline quality and detection of potential adulteration.

  16. [Pyrolysis-gas chromatographic fingerprints with hierarchical cluster analysis for Dendrobium candidum Wall. ex Lindl].

    PubMed

    Wang, Lili; Wang, Cong; Pan, Zaifa; Sun, Fa

    2008-09-01

    The pyrogram fingerprints of Dendrobium candidum Wall. ex Lindl. from different regions were studied by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and compared with hierarchical cluster analysis. The effect of pyrolysis temperature on the fingerprint was examined by evolved gas analysis, and then 450 degrees C was selected as the optimized pyrolysis temperature. An amount of 0.4 mg of raw drug powder was pyrolysed in a vertical microfurnace pyrolyzer, and the products were directly introduced into a gas chromatograph equipped with a flame ionization detector (FID) and a fused-silica capillary column (30 m x 0.25 mm x 0.25 microm). The pyrogram fingerprints of 10 samples from different regions showed a high similarity and a good reproducibility with the relative standard deviations (RSDs) of the retention times less than 0.33% and the RSDs of the relative peak areas less than 4.8%. Therefore, each sample was characterized by the peak area of 31 peaks in each pyrogram and these peaks were employed for hierarchical cluster analysis. Furthermore, the discrimination of the sample from different regions was achieved by hierarchical cluster analysis via recognizing the 10 x 31 data matrix. Thus, the results proved it is a simple, rapid and accurate method suitable for the quality control of the traditional Chinese medicines.

  17. Gas Chromatographic Separation of an Acetylene Vinyl Fluoride-Difluoroethane Mixture on Triethylene Glycol and Silicone Oil,

    DTIC Science & Technology

    The purpose of the research was to study gas-chromatographic separation of impurities of acetylene and difluoroethane in vinyl fluoride obtained by...and difluoroethane . All the components are separated, and the criteria of separation of acetylene-vinyl fluoride and vinyl fluoride- difluoroethane

  18. Gas purge microsyringe extraction for quantitative direct gas chromatographic-mass spectrometric analysis of volatile and semivolatile chemicals.

    PubMed

    Yang, Cui; Piao, Xiangfan; Qiu, Jinxue; Wang, Xiaoping; Ren, Chunyan; Li, Donghao

    2011-03-25

    Sample pretreatment before chromatographic analysis is the most time consuming and error prone part of analytical procedures, yet it is a key factor in the final success of the analysis. A quantitative and fast liquid phase microextraction technique termed as gas purge microsyringe extraction (GP-MSE) has been developed for simultaneous direct gas chromatography-mass spectrometry (GC-MS) analysis of volatile and semivolatile chemicals without cleanup process. Use of a gas flowing system, temperature control and a conventional microsyringe greatly increased the surface area of the liquid phase micro solvent, and led to quantitative recoveries of both volatile and semivolatile chemicals within short extraction time of only 2 min. Recoveries of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and alkylphenols (APs) determined were 85-107%, and reproducibility was between 2.8% and 8.5%. In particular, the technique shows high sensitivity for semivolatile chemicals which is difficult to achieve in other sample pretreatment techniques such as headspace-liquid phase microextraction. The variables affecting extraction efficiency such as gas flow rate, extraction time, extracting solvent type, temperature of sample and extracting solvent were investigated. Finally, the technique was evaluated to determine PAHs, APs and OCPs from plant and soil samples. The experimental results demonstrated that the technique is economic, sensitive to both volatile and semivolatile chemicals, is fast, simple to operate, and allows quantitative extraction. On-site monitoring of volatile and semivolatile chemicals is now possible using this technique due to the simplification and speed of sample treatment.

  19. Results from the Gas Chromatograph Mass Spectrometer (GCMS) Experiment on the Cassini-Huygens Probe

    NASA Technical Reports Server (NTRS)

    Niemann, H.; Atreya, S.; Demick-Montelara, J.; Haberman, J.; Harpold, D.; Kasprzak, W.; Owen, T.; Raaen, E.; Way, S.

    2006-01-01

    The Gas Chromatograph Mass Spectrometer was one of six instruments on the Cassini-Huygens Probe mission to Titan. The GCMS measured in situ the chemical composition of the atmosphere during the probe descent and served as the detector for the pyrolization products for the Aerosol Collector Pyrolyser (ACP) experiment to determine the composition of the aerosol particles. The GCMS collected data from an altitude of 146 km to ground impact. The Probe and the GCMS survived impact and collected data for 1 hour and 9 minutes on the surface. Mass spectra were collected during descent and on the ground over a range of m/z from 2 to 141. The major constituents of the lower atmosphere were confirmed to be N2 and CH4. The methane mole fraction was uniform in the stratosphere. It increased below the tropopause, at about 32 km altitude, monotonically toward the surface, reaching a plateau at about 8 km at a level near saturation. After surface impact a steep increase of the methane signal was observed, suggesting evaporation of surface condensed methane due to heating by the GCMS sample inlet heater. The measured mole fraction of Ar-40 is 4.3x10(exp -5) and of Ar-36 is 2.8x10(exp -7). The other primordial noble gases were below 10(exp -8) mole fraction. The isotope ratios of C-12/C-13 determined from methane measurements are 82.3 and of N-14/N-15 determined from molecular nitrogen are 183. The D/H isotope ratio determined from the H2 and HD measurements is 2.3x10(exp -4). Carbon dioxide, methane, acetylene and cyanogen were detected evaporating from the surface in addition to methane. The GCMS employed a quadrupole mass filter with a secondary electron multiplier detection system and a gas sampling system providing continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic (GC) columns, a chemical scrubber and a hydrocarbon enrichment cell. The GCMS gas inlet was heated to prevent condensation, and to evaporate volatiles from the

  20. Results from the Gas Chromatograph Mass Spectrometer (GCMS) Experiment on the Cassini-Huygens Probe

    NASA Technical Reports Server (NTRS)

    Niemann, Hasso; Atreya, S.; Demick-Monelara, J.; Haberman, J.; Harpold, D.; Kasprzak, W.; Owen, T.; Raaen, E.; Way, S.

    2006-01-01

    The Gas Chromatograph Mass Spectrometer was one of six instruments on the Cassini-Huygens Probe mission to Titan. The GCMS measured in situ the chemical composition of the atmosphere during the probe descent and served as the detector for the pyrolization products for the Aerosol Collector Pyrolyser (ACP) experiment to determine the composition of the aerosol particles. The GCMS collected data from an altitude of 146 km to ground impact. The Probe and the GCMS survived impact and collected data for 1 hour and 9 minutes on the surface. Mass spectra were collected during descent and on the ground over a range of mlz from 2 to 141. The major constituents of the lower atmosphere were confirmed to be N2 and CH4. The methane mole fraction was uniform in the stratosphere. It increased below the tropopause, at about 32 km altitude, monotonically toward the surface, reaching a plateau at about 8 km at a level near saturation. After surface impact a steep increase of the methane signal was observed, suggesting evaporation of surface condensed methane due to heating by the GCMS sample inlet heater. The measured mole fraction of Ar-40 is 4.3x10(exp -5) and of Ar-36 is 2.8x10(exp -7). The other primordial noble gases were below 10(exp -8) mole fraction. The isotope ratios of C-12/C-13 determined from methane measurements are 82.3 and of N-14/N-15 determined from molecular nitrogen are 183. The D/H isotope ratio determined from the H2 and HD measurements is 2.3x10(exp -4). Carbon dioxide, ethane, acetylene and cyanogen were detected evaporating from the surface in addition to methane. The GCMS employed a quadrupole mass filter with a secondary electron multiplier detection system and a gas sampling system providing continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic (GC) columns, a chemical scrubber and a hydrocarbon enrichment cell. The GCMS gas inlet was heated to prevent condensation, and to evaporate volatiles from the

  1. Quantitative structure-retention relationships of polycyclic aromatic hydrocarbons gas-chromatographic retention indices.

    PubMed

    Drosos, Juan Carlos; Viola-Rhenals, Maricela; Vivas-Reyes, Ricardo

    2010-06-25

    Polycyclic aromatic compounds (PAHs) are of concern in environmental chemistry and toxicology. In the present work, a QSRR study was performed for 209 previously reported PAHs using quantum mechanics and other sources descriptors estimated by different approaches. The B3LYP/6-31G* level of theory was used for geometrical optimization and quantum mechanics related variables. A good linear relationship between gas-chromatographic retention index and electronic or topologic descriptors was found by stepwise linear regression analysis. The molecular polarizability (alpha) and the second order molecular connectivity Kier and Hall index ((2)chi) showed evidence of significant correlation with retention index by means of important squared coefficient of determination, (R(2)), values (R(2)=0.950 and 0.962, respectively). A one variable QSRR model is presented for each descriptor and both models demonstrates a significant predictive capacity established using the leave-many-out LMO (excluding 25% of rows) cross validation method's q(2) cross-validation coefficients q(2)(CV-LMO25%), (obtained q(2)(CV-LMO25%) 0.947 and 0.960, respectively). Furthermore, the physicochemical interpretation of selected descriptors allowed detailed explanation of the source of the observed statistical correlation. The model analysis suggests that only one descriptor is sufficient to establish a consistent retention index-structure relationship. Moderate or non-significant improve was observed for quantitative results or statistical validation parameters when introducing more terms in predictive equation. The one parameter QSRR proposed model offers a consistent scheme to predict chromatographic properties of PAHs compounds.

  2. On-line gas chromatographic analysis of higher alcohol synthesis products from syngas.

    PubMed

    Andersson, Robert; Boutonnet, Magali; Järås, Sven

    2012-07-20

    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

  3. Establishing high temperature gas chromatographic profiles of non-polar metabolites for quality assessment of African traditional herbal medicinal products.

    PubMed

    Bony, Nicaise F; Libong, Danielle; Solgadi, Audrey; Bleton, Jean; Champy, Pierre; Malan, Anglade K; Chaminade, Pierre

    2014-01-01

    The quality assessment of African traditional herbal medicinal products is a difficult challenge since they are complex mixtures of several herbal drug or herbal drug preparations. The plant source is also often unknown and/or highly variable. Plant metabolites chromatographic profiling is therefore an important tool for quality control of such herbal products. The objective of this work is to propose a protocol for sample preparation and gas chromatographic profiling of non-polar metabolites for quality control of African traditional herbal medicinal products. The methodology is based on the chemometric assessment of chromatographic profiles of non-polar metabolites issued from several batches of leaves of Combretum micranthum and Mitracarpus scaber by high temperature gas chromatography coupled to mass spectrometry, performed on extracts obtained in refluxed dichloromethane, after removal of chlorophyll pigments. The method using high temperature gas chromatography after dichloromethane extraction allows detection of most non-polar bioactive and non-bioactive metabolites already identified in leaves of both species. Chemometric data analysis using Principal Component Analysis and Partial Least Squares after Orthogonal Signal Correction applied to chromatographic profiles of leaves of Combretum micranthum and Mitracarpus scaber showed slight batch to batch differences, and allowed clear differentiation of the two herbal extracts.

  4. Rapid detection of bacteria with miniaturized pyrolysis-gas chromatographic analysis

    NASA Astrophysics Data System (ADS)

    Mowry, Curtis; Morgan, Catherine H.; Baca, Quentin; Manginell, Ronald P.; Kottenstette, Richard J.; Lewis, Patrick; Frye-Mason, Gregory C.

    2002-02-01

    Rapid detection and identification of bacteria and other pathogens is important for many civilian and military applications. The profiles of biological markers such as fatty acids can be used to characterize biological samples or to distinguish bacteria at the gram-type, genera, and even species level. Common methods for whole cell bacterial analysis are neither portable nor rapid, requiring lengthy, labor intensive sample preparation and bench-scale instrumentation. These methods chemically derivatize fatty acids to produce more volatile fatty acid methyl esters (FAMEs) that can be separated and analyzed by a gas chromatograph (GC)/mass spectrometer. More recent publications demonstrate decreased sample preparation time with in situ derivatization of whole bacterial samples using pyrolysis/derivatization. Ongoing development of miniaturized pyrolysis/GC instrumentation by this department capitalizes on Sandia advances in the field of microfabricated chemical analysis systems ((mu) ChemLab). Microdevices include rapidly heated stages capable of pyrolysis or sample concentration, gas chromatography columns, and surface acoustic wave (SAW) sensor arrays. We will present results demonstrating the capabilities of these devices toward fulfilling the goal of portable, rapid detection and early warning of the presence of pathogens in air or water.

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

    SciTech Connect

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

    1996-09-01

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

  6. Gas chromatographic and mass spectrometric analysis of polychlorinated biphenyls in human placenta and cord blood

    SciTech Connect

    Ando, M.; Saito, H.; Wakisaka, I.

    1986-10-01

    Gas chromatographic and mass spectrometric analyses of polychlorinated biphenyls (PCBs) in placenta, maternal blood, cord blood, and milk were carried out. Trichlorobiphenyl, tetrachlorobiphenyl, pentachlorobiphenyls, and hexachlorobiphenyls were identified by the mass chromatogram and the mass spectra. Some minor peaks of PCBs were identified by gas chromatography. The relationship between the PCB concentration in placenta and that in milk is different in each PCB congener. The higher the chlorine content of the PCB congener, the more significant the correlation. No significant but a low negative correlation exists between the concentration of some PCB congeners in the placenta and that in cord blood. On the other hand, a significant linear correlation exists between the concentration of hexachlorobenzene in the placenta and that in cord blood. The transplacental transport of each PCB congener varied depending upon its chemical nature. Trichlorobiphenyl and tetrachlorobiphenyl were more transferable than hexachlorobiphenyls. The results show that the placenta and cord blood are useful human samples to analyze the body burden of environmental pollutants and to estimate their transfer from mother to fetus.

  7. Capillary gas chromatographic analysis of nitrogen dioxide and pans with luminol chemiluminescent detection.

    SciTech Connect

    Gaffney, J. S.; Bornick, R. M.; Chen, Y.-H.; Marley, N. A.; Environmental Research

    1998-01-01

    Peroxyacyl nitrates (PANs) and nitrogen dioxide are important atmospheric air pollutants in the troposphere. These atmospheric nitrogen species are strongly coupled chemically by a clearly temperature-dependent equilibrium in the troposphere. A chemical method that can measure both nitrogen dioxide and PANs rapidly and with sub-part-per-billion detection is described that is based upon a modified luminol detection system coupled to a capillary gas chromatographic column by using helium as a carrier. The system can readily separate and detect nitrogen dioxide, peroxyacetyl nitrate, peroxyproprionyl nitrate, and peroxybutyrl nitrate with detection limits in the low tens of parts per trillion with total analysis time of less than 1 min. Calibration of PAN by thermal decomposition to nitrogen dioxide is demonstrated with PAN detection sensitivities approximately 75% of the sensitivities observed for NO2 luminol detection by using helium as a carrier gas. The advantages of this method for simultaneous measurement of nitrogen dioxide and PANs over ozone chemiluminescent detection and electron capture detection are discussed, as well as potential applications of this method for heterogeneous surface chemistry studies of PANs and nitrogen dioxide and for tropospheric measurements.

  8. Application of a Modified Gas Chromatograph to Analyze Space Experiment Combustion Gases on Space Shuttle Mission STS-94

    NASA Technical Reports Server (NTRS)

    Coho, William K.; Weiland, Karen J.; VanZandt, David M.

    1998-01-01

    A space experiment designed to study the behavior of combustion without the gravitational effects of buoyancy was launched aboard the Space Shuttle Columbia on July 1, 1997. The space experiment, designated as Combustion Module-1 (CM-1), was one of several manifested on the Microgravity Sciences Laboratory - 1 (MSL-1) mission. The launch, designated STS-94, had the Spacelab Module as the payload, in which the MSL-1 experiments were conducted by the Shuttle crewmembers. CM-1 was designed to accommodate two different combustion experiments during MSL-1. One experiment, the Structure of Flame Balls at Low Lewis-number experiment (SOFBALL), required gas chromatography analysis to verify the composition of the known, premixed gases prior to combustion, and to determine the remaining reactant and the products resulting from the combustion process in microgravity. A commercial, off-the-shelf, dual-channel micro gas chromatograph was procured and modified to interface with the CM-1 Fluids Supply Package and the CM-1 Combustion Chamber, to accommodate two different carrier gases, each flowing through its own independent column module, to withstand the launch environment of the Space Shuttle, to accept Spacelab electrical power, and to meet the Spacelab flight requirements for electromagnetic interference (EMI) and offgassing. The GC data was down linked to the Marshall Space Flight Center for near-real time analysis, and stored on-orbit for post-flight analysis. The gas chromatograph operated successfully during the entire SOFBALL experiment and collected 309 runs. Because of the constraints imposed upon the gas chromatograph by the CM-1 hardware, system and operations, it was unable to measure the gases to the required accuracy. Future improvements to the system for a re-flight of the SOFBALL experiment are expected to enable the gas chromatograph to meet all the requirements.

  9. Graphitic carbon nitride as high-resolution stationary phase for gas chromatographic separations.

    PubMed

    Zheng, Yunzhong; Qi, Meiling; Fu, Ruonong

    2016-07-08

    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.

  10. Modified gas chromatographic/mass spectrometric method for determination of daminozide in high protein food products.

    PubMed

    Faughnan, K T; Woodruff, M A

    1991-01-01

    A modified version of the Conditt and Baumgardner gas chromatographic/mass spectroscopic (GC/MS) method for determination of daminozide in peanut butter and raw peanuts is described. Daminozide in the food product is hydrolyzed to unsymmetrical dimethylhydrazine (UDMH) by sodium hydroxide digestion. The generated UDMH is distilled from the food matrix and captured by reaction with salicylaldehyde in a condensation trap. Resulting high pH distillates generated by peanuts and peanut products are adjusted back to a pH of 5-6 through addition of glacial acetic acid. After thermal incubation and extraction into methylene chloride, salicylaldehyde dimethylhydrazone is separated from interferences by capillary GC and quantitated by MS using the selective ion monitoring (SIM) mode. Quantitation of daminozide is based on the ratio of the salicylaldehyde dimethylhydrazone molecular ion (m/z 164) to the molecular ion (m/z 153) of the internal standard, 4-nitroanisole. Confirmation of daminozide identity is determined by relative intensity of the m/z 164 ion to the m/z 120 (C7H4ON) ion. Improved m/z 164 ion intensity and reduction of neighboring interferences due to acetic acid treatment permitted a daminozide detection limit of 0.005 ppm in a 50 g sample and an associated 0.02 ppm limit of quantitation. This modification is specific for high protein samples that generate high pH distillates such as peanuts and peanut products and is not specifically intended for analysis of low protein samples.

  11. Gas chromatographic/mass spectrometric determination of daminozide in high protein food products.

    PubMed

    Conditt, M K; Baumgardner, J R; Hellmann, L M

    1988-01-01

    A gas chromatographic/mass spectrometric (GC/MS) method for determining daminozide in high protein products has been developed. Daminozide is hydrolyzed in the presence of a strong base to form unsymmetrical dimethylhydrazine (UDMH) which is then distilled from the food matrix. A stable derivative is formed by reacting UDMH with salicyladehyde to form salicyaldehyde dimethylhydrazone. This derivative is separated and quantitated by GC/MS using selected ion monitoring (SIM) of key ions in the fragmentation pattern: m/z 164 (molecular ion of hydrazone) and m/z 120 (C7H6ON). An internal standard, 4-nitroanisole, is monitored at m/z 153 (molecular ion) and m/z 123 (C6H5O2N). The limit of detection is 0.01 ppm daminozide in a 50 g sample; however, because of variation at low levels, the limit of quantitation is 0.1 ppm. Recoveries are 90% or greater from peanuts and peanut butter spiked at the 0.1-2 ppm level. Reproducibility of the method depends on the food matrix and is 26% RSD in the worst case. Data are compared for the GC/MS method and the official EPA colorimetric procedure. Results showed a high bias in the colorimetric method, especially when roasted peanut products were analyzed.

  12. Determination of vapor pressures for nonpolar and semipolar organic compounds from gas chromatographic retention data

    USGS Publications Warehouse

    Hinckley, D.A.; Bidleman, T.F.; Foreman, W.T.; Tuschall, J.R.

    1990-01-01

    Vapor pressures for nonpolar and moderately polar organochlorine, pyrethroid, and organophosphate insecticides, phthalate esters, and organophosphate flame retardants were determined by capillary gas chromatography (GC). Organochlorines and polycyclic aromatic hydrocarbons with known liquid-phase vapor pressures (P??L) (standard compounds) were chromatographed along with two reference compounds n-C20 (elcosane) and p,p???-DDT on a 1.0-m-long poly(dimethylsiloxane) bonded-phase (BP-1) column to determine their vapor pressures by GC (P??GC). A plot of log P??L vs log P??GC for standard compounds was made to establish a correlation between measured and literature values, and this correlation was then used to compute P??L of test compounds from their measured P??GC. P??L of seven major components of technical chlordane, endosulfan and its metabolites, ??-hexachlorocyclohexane, mirex, and two components of technical toxaphene were determined by GC. This method provides vapor pressures within a factor of 2 of average literature values for nonpolar compounds, similar to reported interlaboratory precisions of vapor pressure determinations. GC tends to overestimate vapor pressures of moderately polar compounds. ?? 1990 American Chemical Society.

  13. Cross-column prediction of gas-chromatographic retention indices of saturated esters.

    PubMed

    D'Archivio, Angelo Antonio; Maggi, Maria Anna; Ruggieri, Fabrizio

    2014-08-15

    We combine computational molecular descriptors and variables related with the gas-chromatographic stationary phase into a comprehensive model able to predict the retention of solutes in external columns. To explore the quality of various approaches based on alternative column descriptors, we analyse the Kováts retention indices (RIs) of 90 saturated esters collected with seven columns of different polarity (SE-30, OV-7, DC-710, OV-25, XE-60, OV-225 and Silar-5CP). Cross-column retention prediction is evaluated on an internal validation set consisting of data of 40 selected esters collected with each of the seven columns, sequentially excluded from calibration. The molecular descriptors are identified by a genetic algorithm variable selection method applied to a large set of non-empirical structural quantities aimed at finding the best multi-linear quantitative structure-retention relationship (QSRR) for the column OV-25 having intermediate polarity. To describe the columns, we consider the sum of the first five McReynolds phase constants and, alternatively, the coefficients of the corresponding QSRRs. Moreover, the mean RI value for the subset of esters used in QSRR calibration or RIs of a few selected compounds are used as column descriptors. For each combination of solute and column descriptors, the retention model is generated both by multi-linear regression and artificial neural network regression.

  14. Enantiospecific gas chromatographic-mass spectrometric analysis of urinary methylphenidate: implications for phenotyping.

    PubMed

    LeVasseur, Natalie L; Zhu, Hao-Jie; Markowitz, John S; DeVane, C Lindsay; Patrick, Kennerly S

    2008-02-01

    A chiral derivatization gas chromatographic-mass spectrometric (GC-MS) method for urine methylphenidate (MPH) analysis was developed and validated to investigate preliminary findings regarding a novel MPH poor metabolizer (PM). Detection was by electron impact (EI) ionization-selected ion monitoring of the N-trifluoroacetylprolylpiperidinium fragments from MPH and the piperidine-deuterated MPH internal standard. The PM eliminated approximately 70 times more l-MPH in urine (9% of the dose over 0-10h), and approximately 5 times more of the d-isomer (10% of the dose), than the mean values determined from 10 normal metabolizers of MPH. Only minor amounts of the metabolite p-hydroxy-MPH were found in the urine of both the PM and normal metabolizers, while the concentration of MPH lactam was not high enough to be detectable. The described method indirectly gauges the functional carboxylesterase-1 status of patients receiving MPH based on the evaluation of relative urine concentrations of d-MPH:l-MPH. Clinical implications concerning rational drug selection for an identified or suspected MPH PM are discussed.

  15. Gas chromatographic quantitative analysis of methanol in wine: operative conditions, optimization and calibration model choice.

    PubMed

    Caruso, Rosario; Gambino, Grazia Laura; Scordino, Monica; Sabatino, Leonardo; Traulo, Pasqualino; Gagliano, Giacomo

    2011-12-01

    The influence of the wine distillation process on methanol content has been determined by quantitative analysis using gas chromatographic flame ionization (GC-FID) detection. A comparative study between direct injection of diluted wine and injection of distilled wine was performed. The distillation process does not affect methanol quantification in wines in proportions higher than 10%. While quantification performed on distilled samples gives more reliable results, a screening method for wine injection after a 1:5 water dilution could be employed. The proposed technique was found to be a compromise between the time consuming distillation process and direct wine injection. In the studied calibration range, the stability of the volatile compounds in the reference solution is concentration-dependent. The stability is higher in the less concentrated reference solution. To shorten the operation time, a stronger temperature ramp and carrier flow rate was employed. With these conditions, helium consumption and column thermal stress were increased. However, detection limits, calibration limits, and analytical method performances are not affected substantially by changing from normal to forced GC conditions. Statistical data evaluation were made using both ordinary (OLS) and bivariate least squares (BLS) calibration models. Further confirmation was obtained that limit of detection (LOD) values, calculated according to the 3sigma approach, are lower than the respective Hubaux-Vos (H-V) calculation method. H-V LOD depends upon background noise, calibration parameters and the number of reference standard solutions employed in producing the calibration curve. These remarks are confirmed by both calibration models used.

  16. Anion exchange chromatographic separation of inositol phosphates and their quantification by gas chromatography.

    PubMed

    Heathers, G P; Juehne, T; Rubin, L J; Corr, P B; Evers, A S

    1989-01-01

    The direct measurement of mass of inositol trisphosphate from biologic samples is described. Separation of inositol monophosphate, bisphosphate, trisphosphate, and inositol tetrakisphosphate was achieved using anion exchange chromatography with a sodium sulfate gradient. In addition, separation of the isomers of each inositol phosphate was performed using HPLC procedures. The individual inositol phosphate fractions were subsequently dephosphorylated and desalted. The myo-inositol from each fraction was then derivatized to the hexatrimethylsilyl derivative and the myo-inositol derivatives were quantified by a novel gas chromatographic analysis using the hexatrimethylsilyl derivative of chiro-inositol as an internal concentration reference. This method is a reproducible and relatively rapid procedure for the direct quantification of inositol phosphate mass which overcomes many of the problems associated with the use of radiolabeled precursors. The method is a significant improvement over existing procedures for the quantitative determination of the mass of inositol phosphate by virtue of improved recovery, sensitivity, and technical simplicity. The applicability of this method is illustrated by the quantitative determination of inositol trisphosphate in response to norepinephrine stimulation of adult canine myocytes and cerebral cortical brain slices and by measurement of the isomers of inositol trisphosphate in isolated myocytes.

  17. Analytical bias among different gas chromatographic approaches using standard BTX gases and exhaust samples.

    PubMed

    Kim, Ki-Hyun; Pandey, Sudhir Kumar; Pal, Raktim

    2009-02-01

    In this study, the analytical compatibility of the gas chromatographic (GC) approach was evaluated through a cross-calibration exercise. To this end, three aromatic volatile organic compounds (VOCs: benzene, toluene, and p-xylene (BTX)) were simultaneously analyzed with four individual instrumental setups (type I = GC with MS plus solid phase microextraction (SPME) method, II = GC with flame ionization detection (FID) plus SPME, III = fast GC-FID plus SPME, and IV = GC-FID plus air server/thermal desorption (AS/TD) method). A comparison of basic quality assurance (QA) data revealed considerable differences in DL values among the methods with moderate variabilities in the intercompound sensitivity. In light of the differences in detection properties, the analytical bias involved for each methodological approach was assessed by the relative relationship between analytes and basic operating conditions. The results suggest that the analysis of environmental samples at ultra-low concentration levels (at or below ppb level) can be subject to diverse sources of bias. Although detection properties of target compounds seem to be affected by the combined effects of various factors, changes in the sample concentration levels were seen to be the most consistent under the experimental setups analyzed in this study.

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

    PubMed

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

    2008-03-01

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

  19. Gas chromatographic mass analysis and further pharmacological actions of Cymbopogon proximus essential oil.

    PubMed

    Al-Taweel, A M; Fawzy, G A; Perveen, S; El Tahir, K E H

    2013-09-01

    The present study reports Gas chromatographic mass analysis (GC-MS) as well as important biological activities of Cymbopogon proximus essential oil. The chemical composition of the essential oil of Cymbopogon proximus was investigated by GC-MS. Furthermore, the effects of Cymbopogon proximus essential oil on the cardiac parasympathetic ganglia in rats, the intra-tracheal pressure in guinea-pigs and on carrageenan-induced inflammation in the rats paw, were studied. The GC-MS study led to the identification of 22 components with Piperitone representing (73.81%), Elemol (9.32%), alpha-Eudesmol (5.21%) and alpha-Terpineol (3.01%) of the oils composition. The percentage protective effect of the oil on the vagus-induced bradycardia in rats was 90.1±3.1%, which represents a significant protection. As for the effect of Cymbopogon oil on bronchoconstrictors-induced increase in intra-tracheal pressure in guinea-pigs, the oil antagonized the actions of 5-HT and histamine by 80±3.7 and 93±8.3%, respectively. Pharmacological investigations using Cymbopogon oil revealed its inherent ability to possess a bronchodilator activity mediated via blockade of both histamine and serotonin receptors. It possessed a significant ganglionic blocking action and a limited anti-inflammatory activity that seemed to involve blockade of histamine and serotonin receptors in the rats' paws.

  20. Purge and trap with monolithic sorbent for gas chromatographic analysis of pesticides in honey.

    PubMed

    Chienthavorn, Orapin; Dararuang, Kanittha; Sasook, Anupop; Ramnut, Narumol

    2012-01-01

    Polydivinylbenzene (P-DVB) and silica monolithic materials were synthesised in capillaries and then used to adsorb nine organonitrogen pesticides extracted from honey. After adsorption, each monolith-capillary was connected to a gas chromatograph (GC) with nitrogen-phosphorous detector (NPD). The silica monolith gave better peak shape and intensity than the P-DVB monolith. Formulation of silica monolith with tetramethoxysilane (TMOS) as a sole initiator provided better separation and higher peak intensity, compared to those with methyltrimethoxysilane (MTMS) and (3:1) TMOS/MTMS initiators. The optimum internal diameter and length of silica monolith-capillary were 0.25 mm and 5 cm, respectively. The purge and trap conditions were optimised by purging with nitrogen and heating the honey sample solution at 100 °C for 60 min. Recovery of the method was in a range of 84.95-99.71% and the detection limits of the pesticides determined by using GC-NPD and GC-mass spectrometric detector (MSD) ranged between 0.36-1.75 and 0.13-0.25 ng g(-1), respectively.

  1. Optimisation of temperature-programmed gas chromatographic separation of organochloride pesticides by response surface methodology.

    PubMed

    D'Archivio, Angelo Antonio; Maggi, Maria Anna; Marinelli, Cristina; Ruggieri, Fabrizio; Stecca, Fabrizio

    2015-12-04

    A response surface methodology (RSM) approach is applied to optimise the temperature-programme gas-chromatographic separation of 16 organochloride pesticides, including 12 compounds identified as highly toxic chemicals by the Stockholm Convention on Persistent Organic Pollutants. A three-parameter relationship describing both linear and curve temperature programmes is derived adapting a model previously used in literature to describe concentration gradients in liquid chromatography with binary eluents. To investigate the influence of the three temperature profile descriptors (the starting temperature, the gradient duration and a shape parameter), a three-level full-factorial design of experiments is used to identify suitable combinations of the above variables spanning over a useful domain. Resolutions of adjacent peaks are the responses modelled by RSM using two alternative methods: a multi-layer artificial network (ANN) and usual polynomial regression. The proposed ANN-based approach permits to model simultaneously the resolutions of all the consecutive analyte pairs as a function of the temperature profile descriptors. Four critical pairs giving partially overlapped peaks are identified and multiresponse optimisation is carried out by analysing the surface plot of a global resolution defined as the average of the resolutions of the critical pairs. Descriptive/predictive performance and applicability of the ANN and polynomial RSM methods are compared and discussed.

  2. Performance of the MOMA Gas Chromatograph-Mass Spectrometer onboard the 2018 ExoMars Mission

    NASA Astrophysics Data System (ADS)

    Buch, Arnaud; Pinnick, Veronica; Szopa, Cyril; Grand, Noël; Freissinet, Caroline; Danell, Ryan; van Ameron, Friso; Arevalo, Ricardo; Brinckerhoff, William; Raulin, François; Mahaffy, Paul; Goesmann, Fred

    2015-04-01

    The Mars Organic Molecule Analyzer (MOMA) is a dual ion source linear ion trap mass spectrometer that was designed for the 2018 joint ESA-Roscosmos mission to Mars. The main scientific aim of the mission is to search for signs of extant or extinct life in the near subsurface of Mars by acquir-ing samples from as deep as 2 m below the surface. MOMA will be a key analytical tool in providing chemical (molecular) information from the solid samples, with particular focus on the characterization of organic content. The MOMA instrument, itself, is a joint venture for NASA and ESA to develop a mass spectrometer capable of analyzing samples from pyrolysis gas chromatograph (GC) as well as ambient pressure laser desorption ionization (LDI). The combination of the two analytical techniques allows for the chemical characterization of a broad range of compounds, including volatile and non-volatile species. Generally, MOMA can provide in-formation on elemental and molecular makeup, po-larity, chirality and isotopic patterns of analyte spe-cies. Here we report on the current performance of the MOMA prototype instruments, specifically the demonstration of the gas chromatography-mass spec-trometry (GC-MS) mode of operation. Both instruments have been tested separately first and have been coupled in order to test the efficiency of the future MOMA GC-MS instrument. The main objective of the second step has been to test the quantitative response of both instruments while they are coupled and to characterize the combined instrument detection limit for several compounds. A final experiment has been done in order to test the feasibility of the separation and detection of a mixture contained in a soil sample introduced in the MOMA oven.

  3. Capillary gas chromatographic assay of residual methenamine hippurate in equipment cleaning validation swabs.

    PubMed

    Mirza, T; George, R C; Bodenmiller, J R; Belanich, S A

    1998-02-01

    A capillary gas chromatographic method is described for the determination of methenamine hippurate residue in swabs collected from manufacturing equipment surfaces. Any residual methenamine hippurate remaining on process equipment after cleaning is removed by swabbing with one wet polyester Absorbond swab (4" x 4") pre-moistened with water followed by a dry Absorbond swab. The residual methenamine hippurate is chromatographed on a 30 x 0.32 mm (i.d.) Supelcowax-10 capillary column of 0.25-micron film thickness. The amount of residual methenamine hippurate is determined by comparing the ratio of methenamine hippurate peak area response to that of p-cresol (internal standard) obtained for the sample to a linear calibration curve obtained for a series of standard solutions. The method is demonstrated to be sufficiently linear, accurate, precise, sensitive and rugged for the determination of low levels of methenamine hippurate on equipment surfaces. Using this method, the mean recovery of methenamine hippurate from spiked Absorbond swab samples contained in high density polyethylene bottles was 105.2%, with a relative standard deviation (RSD) of +/- 7.1% (n = 25). The mean recoveries of methenamine hippurate from spiked test plates for '180 Grit' Stainless Steel, Teflon and WARCO White (neoprene and PVC) gasket material were 77.2, 96.1 and 50.6%, with RSDs of +/- 9.4 (n = 25), +/- 4.3 (n = 25) and +/- 36% (n = 20), respectively. Recovery correction factors have been incorporated into the method. The method was successfully applied to the assay of actual equipment cleaning validation swab samples. Stability studies demonstrate that methenamine hippurate is not very stable on the equipment surfaces or in the swabs. It is recommended that the surfaces be swabbed immediately after cleaning and the swabs analyzed within 24 h after sample collection. The results demonstrate that in order to fully validate the cleaning procedures, it is not only necessary to investigate the

  4. A novel derivatization procedure and chiral gas chromatographic method for enantiomeric purity screening of L-carnitine.

    PubMed

    Albreht, Alen; Zupančič, Borut; Vovk, Irena

    2014-01-01

    L-Carnitine is used extensively in functional foods and food supplements; consequently, the control of its enantiomeric purity is of paramount importance. A new derivatization procedure and chiral gas chromatographic method with flame ionization detection, using a cyclodextrin based stationary phase, enables prompt, simple, and inexpensive screening of the enantiomeric ratio of L- and D-carnitine in samples with different matrices. Conversion of carnitine to beta-acetoxy-gama-butyrolactone was optimized for maximum conversion (98% of the desired product lactone was formed and 2% of the side product gama-crotonolactone) and minimum racemization (no changes at the chiral center were detected) and time consumption. As it is shown in this study, a fast gas chromatographic method, with total run time of 7 min, together with the new derivatization procedure enables an effective enantiomeric purity screening of L-carnitine in real samples such as food supplements and L-carnitine raw ingredient.

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

    PubMed

    Roussis; Fitzgerald

    2000-04-01

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

  6. Gas chromatographic ion trap mass spectrometry determination of zoxamide residues in grape, grape processing, and in the fermentation process.

    PubMed

    Angioni, Alberto; Garau, Anna; Caboni, Pierluigi; Russo, Maria Teresa; Farris, Giovanni Antonio; Zara, Severino; Cabras, Paolo

    2005-12-02

    A gas chromatographic ion-trap mass spectrometry (GC-ITMS) method was developed for the determination of the fungicide zoxamide in grape, must, wine, and spirits. Samples were extracted with hexane and analyzed without any clean up. The gas chromatograph was fitted with a carbofrit inserted into the glass liner to allow large volume injections. Analyses were carried out both in EI and CI mode. Recoveries from fortified samples ranged between 86 and 114% at four different fortification levels (n=6 each), ranging between 0.05 and 2.00 mg/kg. The relative standard deviation was below 19%. Both in EI and CI mode the calculated limit of detection (LOD) and quantification (LOQ) were 0.01 and 0.05 mg/kg (0.08 mg/kg in CI), respectively. Moreover the influence of yeasts and bacteria fermentation was evaluated.

  7. Field-portable Gas Chromatograph Mass Spectrometer (GC-MS) Unit for Semi-volatile Compound Analysis in Groundwater

    DTIC Science & Technology

    2011-09-01

    Program ERDC TR-11-11 September 2011 Field-portable Gas Chromatograph Mass Spectrometer (GC-MS) Unit for Semi-volatile Compound Analysis in...fixed laboratories that perform regulatory-approved analytical methods . The typical analysis and data reporting time at most analytical laboratories...USEPA method 8330. Technology description Mass spectrometry (MS) analysis systems can provide valuable chemical information on almost any type of

  8. Fitting formula for the injection volume of a gas chromatograph for radio-xenon sampling in the lower troposphere.

    PubMed

    Shu-jiang, Liu; Zhan-ying, Chen; Shi-lian, Wang; Yin-zhong, Chang; Qi, Li; Yuan-qing, Fan; Yun-gang, Zhao; Huai-mao, Jia; Xin-jun, Zhang; Jun, Wang

    2014-06-01

    GC is usually used for xenon concentration and radon removal in the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty. In a gas chromatograph, the injection volume is defined to calculate the column capacity. In this paper, the injection volume was investigated and a fitting formula for the injection volume was derived and discussed subsequently. As a consequence, the xenon injection volume exponentially decreased with the column temperature increased, but exponentially increased as the flow rate increased.

  9. Development of an Exhaled Breath Monitoring System with Semiconductive Gas Sensors, a Gas Condenser Unit, and Gas Chromatograph Columns

    PubMed Central

    Itoh, Toshio; Miwa, Toshio; Tsuruta, Akihiro; Akamatsu, Takafumi; Izu, Noriya; Shin, Woosuck; Park, Jangchul; Hida, Toyoaki; Eda, Takeshi; Setoguchi, Yasuhiro

    2016-01-01

    Various volatile organic compounds (VOCs) in breath exhaled by patients with lung cancer, healthy controls, and patients with lung cancer who underwent surgery for resection of cancer were analyzed by gas condenser-equipped gas chromatography-mass spectrometry (GC/MS) for development of an exhaled breath monitoring prototype system involving metal oxide gas sensors, a gas condenser, and gas chromatography columns. The gas condenser-GC/MS analysis identified concentrations of 56 VOCs in the breath exhaled by the test population of 136 volunteers (107 patients with lung cancer and 29 controls), and selected four target VOCs, nonanal, acetoin, acetic acid, and propanoic acid, for use with the condenser, GC, and sensor-type prototype system. The prototype system analyzed exhaled breath samples from 101 volunteers (74 patients with lung cancer and 27 controls). The prototype system exhibited a level of performance similar to that of the gas condenser-GC/MS system for breath analysis. PMID:27834896

  10. Development of an Exhaled Breath Monitoring System with Semiconductive Gas Sensors, a Gas Condenser Unit, and Gas Chromatograph Columns.

    PubMed

    Itoh, Toshio; Miwa, Toshio; Tsuruta, Akihiro; Akamatsu, Takafumi; Izu, Noriya; Shin, Woosuck; Park, Jangchul; Hida, Toyoaki; Eda, Takeshi; Setoguchi, Yasuhiro

    2016-11-10

    Various volatile organic compounds (VOCs) in breath exhaled by patients with lung cancer, healthy controls, and patients with lung cancer who underwent surgery for resection of cancer were analyzed by gas condenser-equipped gas chromatography-mass spectrometry (GC/MS) for development of an exhaled breath monitoring prototype system involving metal oxide gas sensors, a gas condenser, and gas chromatography columns. The gas condenser-GC/MS analysis identified concentrations of 56 VOCs in the breath exhaled by the test population of 136 volunteers (107 patients with lung cancer and 29 controls), and selected four target VOCs, nonanal, acetoin, acetic acid, and propanoic acid, for use with the condenser, GC, and sensor-type prototype system. The prototype system analyzed exhaled breath samples from 101 volunteers (74 patients with lung cancer and 27 controls). The prototype system exhibited a level of performance similar to that of the gas condenser-GC/MS system for breath analysis.

  11. Results from the Gas Chromatograph Mass Spectrometer (GCMS) Experiment on the Cassini-Huygens Probe

    NASA Technical Reports Server (NTRS)

    Niemann, Hasso B.

    2006-01-01

    The GCMS was part of the instrument complement on the Cassini-Huygens Probe to measure in situ the chemical composition of the atmosphere during the probe descent and coupled with the Aerosol Collector Pyrolyser (ACP) experiment by serving as detector for the pyrolization products to determine the composition of the aerosol particles. The GCMS employed a quadrupole mass filter with a secondary electron multiplier detection system and a gas sampling system providing continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic (GC) columns, a chemical scrubber and a hydrocarbon enrichment cell. The GCMS gas inlet was heated to prevent condensation, and to evaporate volatiles from the surface after impact. The GCMS collected data from an altitude of 146 km to ground impact. The Probe and the GCMS survived impact and collected data for 1 hour and 9 minutes on the surface. Mass spectra were collected during descent and on the ground over a range of m/z from 2 to 141. The major constituents of the lower atmosphere were confirmed to be NP and CH4. The methane mole fraction was uniform in the stratosphere. It increased below the tropopause, at about 32 km altitude, monotonically toward the surface, reaching a plateau at about 8 km at a level near saturation. After surface impact a steep increase of the methane signal was observed, suggesting evaporation of surface condensed methane due to heating by the GCMS sample inlet heater. The measured mole fraction of Ar-40 is 4.3 x 10(exp-5) and of Ar-36 is 2.8 x 10(exp -7). The other primordial noble gases were below mole fraction. The isotope ratios of C-12/C-13 determined from methane measurements are 82.3 and of N-14/N-15 determined from molecular nitrogen are 183. The D/H isotope ratio determined from the H2 and HD measurements is 2.3 x l0(exp -4). Carbon dioxide, ethane, acetylene and cyanogen were detected evaporating from the surface in addition to methane.

  12. A method for the analysis of tabun in multisol using gas chromatographic flame photometric detection.

    PubMed

    Logan, Thomas P; Allen, Edward D; Way, Mark R; Swift, Austin T; Soni, Sunil-Datta; Koplovitz, Irwin

    2006-01-01

    Preparation and analysis of tabun (GA) solutions are necessary for the continued development of countermeasures to this nerve agent. GA solutions must be stable and compatible for use in the test systems chosen for study; however, GA is very unstable in saline solutions. In the past we have found GA in saline at 2 mg/mL to be stable for a month or less at -70 degrees C, whereas saline solutions of sarin (GB), soman (GD), and cyclosarin (GF) were stable for many months. Previous studies have shown that Multisol (48.5% H(2)O, 40% propylene glycol, 10% ethanol, and 1.5% benzyl alcohol) provides stable solutions of GA. We confirmed the stability of GA in Multisol with phosphorus nuclear magnetic resonance (P horizontal line NMR) and developed a method for the analysis of GA in Multisol using gas chromatographic flame photometric detection (GCFPD) in the phosphorus mode. The GC method used acetonitrile (CH(3)CN) for a dilution solvent because of its miscibility with GA in chloroform (CHCl(3)) standards and GA in Multisol samples at 1% (v/v). Furthermore, the dilutions with CH(3)CN made the phosphorus mode interference peak present in CHCl(3) analytically manageable, reduced the interferences of Multisol in the GC separation, and contributed to a safe and reliable analysis of GA at 20 mug/mL. We demonstrated the stability of GA in Multisol stored for more than a year at 70 degrees C. This method contributes a suitable technique for the preparation and analysis of reliable solutions of GA in nerve agent medical research and demonstrates the extended stability of GA in Multisol.

  13. Stable hydrogen isotopic analysis of nanomolar molecular hydrogen by automatic multi-step gas chromatographic separation.

    PubMed

    Komatsu, Daisuke D; Tsunogai, Urumu; Kamimura, Kanae; Konno, Uta; Ishimura, Toyoho; Nakagawa, Fumiko

    2011-11-15

    We have developed a new automated analytical system that employs a continuous flow isotope ratio mass spectrometer to determine the stable hydrogen isotopic composition (δD) of nanomolar quantities of molecular hydrogen (H(2)) in an air sample. This method improves previous methods to attain simpler and lower-cost analyses, especially by avoiding the use of expensive or special devices, such as a Toepler pump, a cryogenic refrigerator, and a special evacuation system to keep the temperature of a coolant under reduced pressure. Instead, the system allows H(2) purification from the air matrix via automatic multi-step gas chromatographic separation using the coolants of both liquid nitrogen (77 K) and liquid nitrogen + ethanol (158 K) under 1 atm pressure. The analytical precision of the δD determination using the developed method was better than 4‰ for >5 nmol injections (250 mL STP for 500 ppbv air sample) and better than 15‰ for 1 nmol injections, regardless of the δD value, within 1 h for one sample analysis. Using the developed system, the δD values of H(2) can be quantified for atmospheric samples as well as samples of representative sources and sinks including those containing small quantities of H(2) , such as H(2) in soil pores or aqueous environments, for which there is currently little δD data available. As an example of such trace H(2) analyses, we report here the isotope fractionations during H(2) uptake by soils in a static chamber. The δD values of H(2) in these H(2)-depleted environments can be useful in constraining the budgets of atmospheric H(2) by applying an isotope mass balance model.

  14. Measurement of Ethanol in Gaseous Breath Using a Miniature Gas Chromatograph

    PubMed Central

    Morey, Timothy E.; Booth, Matthew M.; Prather, Robert A.; Nixon, Sara J.; Boissoneault, Jeff; Melker, Richard J.; Goldberger, Bruce A.; Wohltjen, Hank; Dennis, Donn M.

    2011-01-01

    We designed and built a novel, miniature gas chromatograph (mGC) to use exhaled breath to estimate blood ethanol concentrations that may offer GC quality sensitivity and specificity, but with portability, reduced size, and decreased cost. We hypothesized that the mGC would accurately estimate the serum ethanol concentration using exhaled breath. Human subjects (n = 8) were dosed with ethanol employing the Widmark criteria, targeting a blood concentration of 0.08 g/dL. Serum and breath samples were collected concurrently over an hour. Ethanol concentrations in serum were measured using a CLIA-approved laboratory. Ethanol concentrations in conventional breath were assayed using a calibrated mGC or Intoxilyzer 400PA. Data were analyzed using Bland-Altman analysis using serum concentrations as a “gold standard”. For the mGC, the regression line (correlation coefficient), bias, and 95% limits of agreement were y = 1.013x − 0.009 (r = 0.91), −0.008 g/dL, and −0.031 to 0.016 g/dL, respectively, for 30 specimens. For the Intoxilyzer 400PA, the regression line (correlation coefficient), bias, and 95% limits of agreement were y = 0.599x + 0.008 (r = 0.86), −0.024 g/dL, and −0.049 to 0.002 g/dL, respectively, for 71 specimens with a large magnitude effect. We concluded that the mGC, using exhaled breath, performed well to estimate the serum ethanol concentrations. PMID:21439148

  15. The Gas Chromatograph Mass Spectrometer (GCMS) Experiment on the Cassini-Huygens Probe: First Results

    NASA Technical Reports Server (NTRS)

    Niemann, H.; Demick, J.; Haberman, J.; Harpold, D.; Kasprzak, W.; Raaen, E.; Way, S.; Atreya, S.; Carignan, G.; Bauer, S.

    2005-01-01

    The Huygens Probe of the Cassini Huygens Mission entered the atmosphere of the moon Titan on January 14, 2005. The GCMS was part of the instrument complement on the Probe to measure in situ the chemical composition of the atmosphere during the probe descent and to support the Aerosol Collector Pyrolyzer (ACP) experiment by serving as detector for the pyrolization products. The GCMS collected data from an altitude of 146 km to ground impact for a time interval of 2 hours and 37 minutes. The Probe and the GCMS survived the ground impact and collected data for 1 hour and 9 minutes on the surface in the near surface environment until signal loss by the orbiter. The instrument collected 5634 mass spectra during descent and 2692 spectra on the ground over a range of m/z from 2 to 141. Eight gas chromatograph samples were taken during the descent and two on the ground. This is a report on work in progress. The major constituents of the lower atmosphere were found to be N2 and CH4. The methane-mixing ratio was found to increase below the turbopause, about 35 km altitude, monotonically toward the surface to levels near saturation. After surface impact a steep increase of the mixing ratio was observed suggesting evaporation of surface condensed methane due to heating by the GCMS sample inlet heater. Other constituents were found to be in very low concentrations, below ppm levels. The presence of Argon 40 was confirmed. The results for the other noble gases are still being evaluated. Other hydrocarbons and nitriles were also observed and quantitative evaluation is in progress. Preliminary ratios for the major carbon and nitrogen isotopes were computed from methane and molecular nitrogen measurements.

  16. Cassini-Huygens Probe Gas Chromatograph Mass Spectrometer (GCMS) Experiment: First Results

    NASA Technical Reports Server (NTRS)

    Niemann, H.; Demick, J.; Haberman, J.; Harpold, D.; Kasprzak, W.; Raaen, E.; Way, S.; Atreya, S.; Carignan, G.; Bauer, S.

    2005-01-01

    The Huygens Probe of the Cassini Huygens Mission entered the atmosphere of the moon Titan on January 14, 2005. The GCMS was part of the instrument complement on the probe to measure in situ the chemical composition of the atmosphere during the probe descent and to support the Aerosol Collector Pyrolyzer (ACP) experiment by serving as detector for the pyrolization products. The GCMS collected data from an altitude of 146 km to ground impact for a time interval of 2hours and 37minutes. The Probe and the GCMS survived the ground impact and collected data for 1hour and 9 minutes on the surface in the near surface environment until signal loss by the orbiter. The major constituents of the lower atmosphere were found to be N2 and CH4. The methane-mixing ratio was found to increase below the turbopause, about 35 km altitude, monotonically toward the surface to levels near saturation. After surface impact a steep increase of the mixing ratio was observed suggesting evaporation of surface condensed methane due to heating by the GCMS sample inlet heater. Other constituents were found to be in very low concentrations, below ppm levels. The presence of Argon 40 was confirmed. The results for the other noble gases are still being evaluated. Other hydrocarbons and nitriles were also observed and quantitative evaluation is in progress. Preliminary ratios for the major carbon and nitrogen isotopes were computed from methane and molecular nitrogen measurements. The instrument collected 5634 mass spectra during descent and 2692 spectra on the ground over a range of m/z from 2 to 141. Eight gas chromatograph samples were taken during the descent and two on the ground.

  17. Toward a microfabricated preconcentrator-focuser for a wearable micro-scale gas chromatograph.

    PubMed

    Bryant-Genevier, Jonathan; Zellers, Edward T

    2015-11-27

    This article describes work leading to a microfabricated preconcentrator-focuser (μPCF) designed for integration into a wearable microfabricated gas chromatograph (μGC) for monitoring workplace exposures to volatile organic compounds (VOCs) ranging in vapor pressure from ∼0.03 to 13kPa at concentrations near their respective Threshold Limit Values. Testing was performed on both single- and dual-cavity, etched-Si μPCF devices with Pyrex caps and integrated resistive heaters, packed with the graphitized carbons Carbopack X (C-X) and/or Carbopack B (C-B). Performance was assessed by measuring the 10% breakthrough volumes and injection bandwidths of a series of VOCs, individually and in mixtures, as a function of the VOC air concentrations, mixture complexity, sampling and desorption flow rates, adsorbent masses, temperature, and the injection split ratio. A dual-cavity device containing 1.4mg of C-X and 2.0mg of C-B was capable of selectively and quantitatively capturing a mixture of 14 VOCs at low-ppm concentrations in a few minutes from sample volumes sufficiently large to permit detection at relevant concentrations for workplace applications with the μGC detector that we ultimately plan to use. Thermal desorption at 225°C for 40s yielded ≥99% desorption of all analytes, and injected bandwidths as narrow as 0.6s facilitated efficient separation on a downstream 6-m GC column in <3min. A preconcentration factor of 620 was achieved for benzene from a sample of just 31mL. Increasing the mass of C-X to 2.3mg would be required for exhaustive capture of the more volatile target VOCs at high-ppm concentrations.

  18. Comprehensive two-dimensional gas chromatographic separations with a microfabricated thermal modulator.

    PubMed

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

    2012-08-21

    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.

  19. Gas chromatographic and mass spectrometric investigations of organic residues from Roman glass unguentaria.

    PubMed

    Ribechini, Erika; Modugno, Francesca; Colombini, Maria Perla; Evershed, Richard P

    2008-03-07

    A combination of gas chromatographic (GC) and mass spectrometric (MS) techniques, including direct exposure-MS (DE-MS), high-temperature GC-MS (HTGC-MS) and GC-MS of neutral and acid fractions, was employed to study the composition and recognise origin of the organic materials used to manufacture balm residues surviving in a series of glass unguentaria recovered from excavations of a Roman villa (Villa B) in the ancient town of Oplontis (Naples, Italy). DE-MS provided comprehensive 'fingerprint' information on the solvent soluble components of the contents of the unguentaria, while GC-MS analyses provided detailed molecular compositions, highlighting the presence of a wide range of compound classes including mid- and long-chain fatty acids, long-chain hydroxy-acids, n-alkanols, alkandiols, n-alkanes, long-chain monoesters, phytosterols and diterpenoid acids. Characteristic biomarkers and their distributions indicate the presence of beeswax, Pinaceae resin and another wax, as the main organic constituents of all of the preparations examined. In particular, the occurrence of phytosterols and long-chain monoesters, in which the acyl moiety was not exclusively palmitic acid, suggested the presence of a second waxy-lipid constituent of plant origin. The results are consistent with beeswax being used in the preparation of the cosmetics preserved in the unguentaria, while the other lipids are most likely the residue of some as yet unidentified plant extract(s), possibly deriving from the cuticular waxes of flowers and/or leaves. The composition of the extracts are consistent with the ancient practices of maceration and/or "enfleurage", in which lipid-based materials, such as beeswax, animal fat or vegetables oils, were used to extract aromatic and fragrant substances from resin, flowers, spices and scented wood, in order to produce unguents and balms.

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

    USGS Publications Warehouse

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

    1984-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Huz, Kateryna

    2014-01-01

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

  2. Comparison of two gas-liquid chromatograph columns for the analysis of fatty acids in ruminant meat.

    PubMed

    Alves, Susana P; Bessa, Rui J B

    2009-06-26

    Two gas-liquid chromatograph capillary columns for the analysis of fatty acids (FA) in ruminant fat are compared. Those columns are the CP-Sil 88 of 100 m long with a highly polar stationary phase and the Omegawax 250 of 30 m long with a stationary phase of intermediate polarity. Fatty acid methyl ester (FAME) patterns of branched-chain, cis and trans octadecenoate isomers, as well as conjugated and non-conjugated 18:2 and 18:3 isomers are fairly different between columns, even though most of the FAME could be separated on either column. However, the CP-Sil 88 showed better resolution of 18:1 isomers than Omegawax 250. The analysis of 96 samples of ruminant meat fat in both chromatographic systems showed that averages obtained for total FA content and for most of the individual FA did not differ between columns. Moreover, regression analysis of Omegawax and CP-Sil 88 data is highly correlated. Quantitative differences between chromatographic systems were detected for samples containing more than 66 mg fatty acids per gram of muscle dry matter.

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

    PubMed

    Larson, Tuula; Östman, Conny; Colmsjö, Anders

    2011-04-01

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

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

    PubMed

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

    2007-08-13

    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.

  5. Gas chromatographic determination of water in organic compounds and of organic compounds in water after steam distillations

    SciTech Connect

    Dix, K.D.

    1990-01-01

    A gas chromatograph (GC) with a flame ionization detector (FID) is shown to be effective in the determination of water in organic compounds. Since the FID gives little response for water, a reaction is needed to convert water into a detectable species. The ketal, 2,2-dimethoxypropane (DMP), reacts quantitatively with water to yield the products methanol and acetone when an acid catalyst is present. Acetone is easily determined with a GC equipped with a capillary column and FID. A solid acid catalyst, Nafion, has been effective and is easily separated before sample introduction into the GC.

  6. Preliminary results of investigations into the use of artificial neural networks for discriminating gas chromatograph mass spectra of remote samples

    NASA Technical Reports Server (NTRS)

    Geller, Harold A.; Norris, Eugene; Warnock, Archibald, III

    1991-01-01

    Neural networks trained using mass spectra data from the National Institute of Standards and Technology (NIST) are studied. The investigations also included sample data from the gas chromatograph mass spectrometer (GCMS) instrument aboard the Viking Lander, obtained from the National Space Science Data Center. The work performed to data and the preliminary results from the training and testing of neural networks are described. These preliminary results are presented for the purpose of determining the viability of applying artificial neural networks in discriminating mass spectra samples from remote instrumentation such as the Mars Rover Sample Return Mission and the Cassini Probe.

  7. Multiresidue method for the gas chromatographic determination of pesticides in honey after solid-phase extraction cleanup.

    PubMed

    Jansson, C

    2000-01-01

    A new multiresidue method is described for the determination of pesticides in honey. The method involves dissolution of the honey in a methanol-water mixture, followed by solid-phase extraction cleanup and gas chromatographic determination. Twenty-six pesticides used on flowering field crops, on flowering fruit and vegetables, or as acaricides to control Varroa jacobsoni in beehives are determined by the method. Recoveries from honey, spiked at 0.02-1.6 mg/kg, ranged from 85 to 127% with a relative standard deviation (RSD) of 2-16%, except for the RSD of 27% for captan at 0.05 mg/kg.

  8. Gas chromatographic/mass spectrometric analyses of unknown analytical response in imported Fava beans: 4-chloro-6-methoxyindole.

    PubMed

    Petzinger, G; Barry, T L; Roach, J A; Musser, S M; Sphon, J

    1995-01-01

    A halogenated unidentified analytical response (UAR) was encountered in a number of imported Fava bean samples during the Food and Drug Administration's routine pesticide-monitoring program. Gas chromatographic/mass spectrometric (GC/MS) analyses identified the halogenated component as 4-chloro-6-methoxyindole, a naturally occurring promutagen in Fava beans that has been linked to incidents of gastric cancer. Data from electron impact, positive and negative chemical ionization, collision-induced dissociation, and deuteration studies of this compound are presented, along with GC retention time data.

  9. Classification of gasoline by octane number and light gas condensate fractions by origin with using dielectric or gas-chromatographic data and chemometrics tools.

    PubMed

    Rudnev, Vasiliy A; Boichenko, Alexander P; Karnozhytskiy, Pavel V

    2011-05-15

    The approach for classification of gasoline by octane number and light gas condensate fractions by origin with using dielectric permeability data has been proposed and compared with classification of same samples on the basis of gas-chromatographic data. The precision of dielectric permeability measurements was investigated by using ANOVA. The relative standard deviation of dielectric permeability was in the range from 0.3 to 0.5% for the range of dielectric permeability from 1.8 to 4.4. The application of exploratory chemometrics tools (cluster analysis and principal component analysis) allow to explicitly differentiate the gasoline and light gas condensate fractions into groups of samples related to specific octane number or origin. The neural networks allow to perfectly classifying the gasoline and light gas condensate fractions.

  10. Measurement of dissolved H2, O2, and CO2 in groundwater using passive samplers for gas chromatographic analyses.

    PubMed

    Spalding, B P; Watson, D B

    2006-12-15

    A simple in-situ passive dissolved gas groundwater sampler, comprised of a short length of silicone tubing attached to a gastight or other syringe, was adapted and tested for in-situ collection of equilibrium gas samples. Sampler retrieval after several days of immersion in groundwater allowed the direct injection of the sample onto a gas chromatograph (GC), simplifying field collection and sample handling over the commonly used "bubble stripping" method for H2 analyses. A GC was modified by sequencing a thermal conductivity (TC) detector followed by a reductive gas (RG) detector so that linear calibration of H2 over the range 0.2-200,000 ppmv was attained using a 0.5-mL gas sample; inclusion of the TC detector allowed the simultaneous quantification of other fixed gases (O2, CO2, He, and Ne) to which the RG detector was not responsive. Uptake kinetics for H2 and He indicated that the passive sampler reached equilibrium within 12 h of immersion in water. Field testing of these passive samplers revealed unusually large equilibrium gas-phase H2 concentrations in groundwater, ranging from 0.1 to 13.9%, by volume, in 11 monitoring wells surrounding four former radiological wastewater disposal ponds at the Y-12 plant in Oak Ridge, Tennessee.

  11. Solid phase micro extraction - A new technique coupled with gas chromatograph for chloroethene analysis from aqueous samples

    SciTech Connect

    Xu, N.; Sewell, G.W.

    1996-10-01

    Once the chloroethenes (tetrachloroethene and trichloroethene) contamination occurs in the subsurface environment, they tend to retain and form a Pollution plum in the aquifer because of their recalcitrance to aerobic oxidation. Currently, the most promising bioremediation method for chlorinated compounds is through anaerobic reductive biotransformation, in which each chlorine is replaced by a hydrogen. To study the biodegradation process, it is essential to monitor tetrachloroethene and its degradation daughter products frequently. An analytical method has been modified for chloroethene analysis by gas chromatography. Solid Phase Micro Extraction technique has been used to extract aqueous sample onto a fiber and then to desorb the sample directly into a gas chromatograph injection port. The total run time is less than 17 minutes.

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

    PubMed

    Byers, John A

    2004-05-30

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

  13. Gas chromatographic-mass spectrometric determination of brain levels of alpha-cholest-8-en-3beta-ol (lathosterol).

    PubMed

    Luzón-Toro, Berta; Zafra-Gómez, Alberto; Ballesteros, Oscar

    2007-05-01

    A gas chromatographic-mass spectrometric (GC-MS) method is proposed for the detection and quantification of lathosterol in rabbit brain. This compound is one of the most important precursors of the cholesterol synthesis. The interest in brain cholesterol metabolism is growing nowadays since it was described to play an important role in some neurodegenerative disorders such as Alzheimer's disease and Multiple Sclerosis. The analytical methodology proposed involves a liquid-liquid extraction procedure (LLE) followed by a silylation step previous to the GC-MS analysis. The chromatographic separation was performed by using a low bleed HP5-MS fused silica capillary column. A clean up is not necessary when using single-ion monitoring (SIM) mode. The molecular ion appears at 458 m/z; being as well the base peak. Alpha-naphtol was used as an internal standard. The detection limit obtained was 0.09 microg mL(-1). The method was applied to the determination of brain lathosterol levels in rabbits fed with different types of diets (control and atherogenic, supplemented or not with natural polyphenolic antioxidants). The quantification of the compound in samples showed a reduction, after 1 month, of this precursor of cholesterol synthesis in groups fed with antioxidant supplemented diets.

  14. Determination of volatile organic compounds in ambient air with gas chromatograph-flame ionization and ion trap detection

    SciTech Connect

    Liu, S.; Carley, R.J.; Kang, J.; Chen, J.; Stuart, J.D.

    1994-12-31

    Two new techniques are utilized to integrate the following three equipments: an Entech 2000 automated air concentrator, a Hewlett Packard gas chromatograph (GC) with flame ionization detector (FID) and an ion trap mass spectrometer detector (ITD). This combined analytical system is used to determine low ppb level volatile organic compounds (VOC) in ambient air. The first technique is to configure the inlet system of the GC, so that the pressure regulated flow control system of the GC injection port is used to control the flow of both the desorb gas of the automated air concentrator and the carrier gas of the GC column. The injection port still can be used to inject gas and liquid samples directly. The second technique is to split the effluent of GC column at a 1:1 ratio to the ITD and the FID. In this way, both FID and ITD data can be obtained for each analysis. For ambient air non-methane hydrocarbons monitoring, the FID detector is widely used. Oxygen containing and halogenated organic compounds cannot be differentiated by FID detector and would be quantified as coeluting hydrocarbons. However, volatile organic compounds other than target hydrocarbons can be identified by ITD. This analytical system is very valuable research tool for non-methane hydrocarbons and urban air toxic monitoring. The performances of this developed system have been presented.

  15. Cyclotriveratrylene as a new-type stationary phase for gas chromatographic separations of halogenated compounds and isomers.

    PubMed

    Lv, Qing; Zhang, Qing; Qi, Meiling; Bai, Hua; Ma, Qiang; Meng, Xianshuang; Fu, Ruonong

    2015-07-24

    Cyclotriveratrylene (CTV) is reported here for the first time as stationary phase for capillary gas chromatographic (GC) separations. CTV stationary phase showed weak polarity comparable to the conventional 5% phenyl polysiloxane stationary phase but exhibited different retention behaviours and higher resolution for some of the indicated analytes. Most importantly, CTV stationary phase exhibited preferential selectivity for halogenated compounds, positional and geometrical isomers. Effect of column temperature on retention and thermal stability of CTV column were also investigated. Moreover, CTV capillary column showed good repeatability in terms of run-to-run, day-to-day and column-to-column. The unique physicochemical features and efficient separation ability for analytes of close properties show the potential of CTV as a new-type stationary phase in GC as well as separation science.

  16. Ambient Atmospheric Hydrocarbon Content as Determined by Gas Chromatographic Techniques from Rural Tidewater Virginia in Late Spring 1974

    NASA Technical Reports Server (NTRS)

    Copeland, G. E.; Davis, R.; Maroulis, P.; Bandy, A. R.; Denyszyn, R.; Kindle, E. C.

    1975-01-01

    In an attempt to ascertain the naturally generated hydrocarbon contribution to the air quality of the Hampton Roads region of Tidewater Virginia, a series of 27 air samples was obtained in two rural locations during late spring of 1974. These samples were analyzed for their hydrocarbon content (carbon number range C5 to C10) using gas chromatographic techniques. The thirty different hydrocarbon species were identified and monitored in the experiment. Preliminary analysis of the data indicates an average concentration of 397 parts per billion by weight (carbon) for the total non-methane hydrocarbon loading for C5 to C10 during the experiment. This value exceeds the National Primary Air Quality Standards as set by the Environmental Protection Agency.

  17. Microfabricated gas chromatograph for on-site determination of trichloroethylene in indoor air arising from vapor intrusion. 1. Field evaluation.

    PubMed

    Kim, Sun Kyu; Burris, David R; Chang, Hungwei; Bryant-Genevier, Jonathan; Zellers, Edward T

    2012-06-05

    Results are presented of inaugural field tests of two identical prototype microfabricated gas chromatographs (μGC) adapted for the in situ determination of trichloroethylene (TCE) in indoor air in support of vapor intrusion (VI) investigations. Each μGC prototype has a pretrap and partially selective high-volume sampler of conventional design, a micromachined-Si focuser for injection, dual micromachined-Si columns for separation, and an integrated array of four microscale chemiresistors with functionalized gold nanoparticle interface films for multichannel detection. Scrubbed ambient air is used as the carrier gas. Field-generated calibration curves were linear for injected TCE masses of 26-414 ng (4.8-77 ppb·L; r(2) > 0.98) and the projected single-sensor detection limit was 0.052 ppb for an 8-L air sample collected and analyzed in 20 min. Consistent performance between the prototypes and good medium-term stability were shown. Above the mitigation action level (MAL) of 2.3 ppb for the field-test site, μGC TCE determinations fell within ±25% of those from the reference method for 21 of 26 measurements, in the presence of up to 37 documented background VOCs. Below the MAL, positive biases were consistently observed, which are attributable to background VOCs that were unresolvable chromatographically or by analysis of the sensor-array response patterns. Results demonstrate that this type of μGC instrument could serve the need for routine TCE determinations in VI-related assessment and mitigation efforts.

  18. Fast low-pressure microwave assisted extraction and gas chromatographic determination of polychlorinated biphenyls in soil samples.

    PubMed

    Bruzzoniti, M C; Maina, R; Tumiatti, V; Sarzanini, C; Rivoira, L; De Carlo, R M

    2012-11-23

    A new technology equipment for low-pressure microwave assisted extraction (usually employed for organic chemistry reactions), recently launched in the market, is used for the first time in environmental analysis for the extraction of commercial technical Aroclor mixtures from soil. Certified reference materials of Aroclor 1260, Aroclor 1254 and Aroclor 1242 in transformer oils were used to contaminate the soil samples and to optimize the extraction method as well as the subsequent gas chromatographic electron capture detection (GC-ECD) analytical method. The study was performed optimizing the extraction, the purification and the gas chromatographic separation conditions to enhance the resolution of difficult pairs of congeners (C28/31 and C141/179). After optimization, the recovery yields were included within the range 79-84%. The detection limits, evaluated for two different commercial polychlorinated biphenyl (PCB) mixtures (Aroclor 1260 and Aroclor 1242) were 0.056 ± 0.001 mg/kg and 0.290 ± 0.006 mg/kg, respectively. The method, validated with certified soil samples, was used to analyze a soil sample after an event of failure of a pole-mounted transformer which caused the dumping of PCB contaminated oil in soil. Moreover, the method provides simple sample handling, fast extraction with reduced amount of sample and solvents than usually required, and simple purification step involving the use of solvent (cyclohexane) volumes as low as 5 mL. Reliability and reproducibility of extraction conditions are ensured by direct and continuous monitoring of temperature and pressure conditions.

  19. Gas chromatographic/mass spectrometric analysis of morphine and codeine in human urine of poppy seed eaters.

    PubMed

    elSohly, H N; Stanford, D F; Jones, A B; elSohly, M A; Snyder, H; Pedersen, C

    1988-03-01

    In this study, poppy seeds were examined for a natural constituent that might serve as a maker for the seeds' ingestion as opposed to opiate abuse. Thebaine was selected as possible marker, since it was found to be a component of all poppy seeds examined and was not a natural component of different heroin samples. During the course of this investigation, a new extraction and cleanup procedure was developed for the gas chromatographic/nitrogen phosphorus detection (GC/NPD) and gas chromatographic/mass spectrometric (GC/MS) analysis of morphine and codeine in urine. A linear response, over a concentration range of 25 to 600 ng/mL, was obtained for codeine and morphine (r = 0.9982 and 0.9947, respectively). The minimum detectable level (LOD) and limit of quantitation (LOQ) for morphine were 10 and 30 ng/mL, respectively; whereas LOD and LOQ for codeine were 2 and 8 ng/mL, respectively. The coefficients of variance (CV, n = 6) for morphine and codeine analyses at the 100-ng/mL level were 13.3 and 4.6%, respectively. This procedure was used for the analysis of urine samples from five poppy seed eaters who each ingested 200 g of poppy seed cake. Results indicated that significant amounts of morphine and codeine are excreted in urine and that in all subjects, at least at one point in time, the apparent morphine concentration as determined by radioimmunoassay (RIA) analysis exceeded the cutoff value (300 ng/mL) established for screening. Thebaine was not detected in urine specimens collected following poppy seeds ingestion and thus could not be used as a marker.

  20. 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

    SciTech Connect

    Lockrem, L.L.

    1998-01-12

    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.

  1. Integration of gas chromatographs into the Federal Highway Administration/Environmental Protection Agency near road MSAT study in Las Vegas, NV

    EPA Science Inventory

    This paper documents the technical evaluation of a semi-continuous gas chromatograph (GC) for the measurement of benzene and 1,33butadiene in the near road environment. This paper will also consider the some of the non-technical implications associated with the operation of a GC ...

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

    ERIC Educational Resources Information Center

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

    1980-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Bonnet, J.-Y.; Szopa, C.; Millan, M.; Coscia, D.; Cabane, M.; Belmahdi, I.; Buch, A.; Dequaire, T.; Coll, P.; Teinturier, S.; Mahaffy, P.

    2015-10-01

    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.

  4. Use of a modified Tenax GC column packing for the direct gas chromatographic analysis of phenols in water at the ppm level.

    PubMed

    Bartle, K D; Elstub, J; Novotny, M; Robinson, R J

    1977-05-21

    Dilute solutions of phenols in water at the ppm level may be analysed gas chromatographically by direct injection onto a column with a packing similar to that used in the Viking 1975 spacecraft: Tenax GC (2,6-diphenyl-p-phenylene oxide polymer) modified with polymetaphenyl ether liquid phase to eradicate irreversible adsorption. Symmetrical peaks were observed for injections of less than 1 ng of phenol and some of its alkylated derivatives. Chromatographic properties of modified Tenax GC columns are reported along with their application to the analysis of some industrial effluents with previous work-up.

  5. Miniature radio-frequency mobility analyzer as a gas chromatographic detector for oxygen-containing volatile organic compounds, pheromones and other insect attractants.

    PubMed

    Eiceman, G A; Tadjikov, B; Krylov, E; Nazarov, E G; Miller, R A; Westbrook, J; Funk, P

    2001-05-11

    A high electric field, radio-frequency ion mobility spectrometry (RF-IMS) analyzer was used as a small detector in gas chromatographic separations of mixtures of volatile organic compounds including alcohols, aldehydes, esters, ethers, pheromones, and other chemical attractants for insects. The detector was equipped with a 2 mCi 63Ni ion source and the drift region for ion characterization was 5 mm wide, 15 mm long and 0.5 mm high. The rate of scanning for the compensation voltages was 60 V s(-1) and permitted four to six scans to be obtained across a capillary chromatographic elution profile for each component. The RF-IMS scans were characteristic of a compound and provided a second dimension of chemical identity to chromatographic retention adding specificity in instances of co-elution. Limits of detection were 1.6-55 x 10(-11) g with an average detection limit for all chemicals of 9.4 x 10(-11) g. Response to mass was linear from 2-50 x 10(-10) g with an average sensitivity of 4 pA ng(-1). Separations of pheromones and chemical attractants for insects illustrated the distinct patterns obtained from gas chromatography with RF-IMS scans in real time and suggest an analytical utility of the RF-IMS as a small, advanced detector for on-site gas chromatographs.

  6. On-line gas chromatographic analysis of Fischer-Tropsch synthesis products formed in a supercritical reaction medium

    SciTech Connect

    Snavely, K.; Subramaniam, B.

    1997-10-01

    C{sub 1}-C{sub 30} products from Fischer-Tropsch synthesis, conducted in a supercritical n-hexane medium over an Fe catalyst in a fixed-bed reactor, are analyzed using on-line gas chromatography. A Hewlett-Packard 5890 Series II gas chromatograph (GC) is modified to minimize the effects of condensation of the on-line sample in the transfer lines. The GC is configured with a Supelco Petrocol DH capillary column connected to a flame ionization detector (FID) and two 1.83 m {times} 3.18 mm stainless steel columns placed in series, packed with 80/100 mesh HayeSep D, connected to a thermal conductivity detector (TCD). It is shown that pressure and temperature affect the elution order of oxygenates relative to hydrocarbons in the nonpolar capillary column. This phenomenon is exploited for obtaining improved resolution; several distinct methods produce similar elution orders. Ar, added to the syngas feed, is used to calculate syngas conversion. All compounds eluting before hexane (C{sub 1}-C{sub 5}, other than 2-methylpropene/1-butene and propanal/propanone) and nearly all the major peaks eluting after hexane are resolved in the capillary column. H{sub 2}, Ar, CO, CH{sub 4}, CO{sub 2}, and H{sub 2}O are resolved in the packed columns. The method provides excellent quantitative measurement of component mole fractions that are within the range of calibration.

  7. Development of High Precision Metal Micro-Electro-Mechanical-Systems Column for Portable Surface Acoustic Wave Gas Chromatograph

    NASA Astrophysics Data System (ADS)

    Iwaya, Takamitsu; Akao, Shingo; Sakamoto, Toshihiro; Tsuji, Toshihiro; Nakaso, Noritaka; Yamanaka, Kazushi

    2012-07-01

    In the field of environmental measurement and security, a portable gas chromatograph (GC) is required for the on-site analysis of multiple hazardous gases. Although the gas separation column has been downsized using micro-electro-mechanical-systems (MEMS) technology, an MEMS column made of silicon and glass still does not have sufficient robustness and a sufficiently low fabrication cost for a portable GC. In this study, we fabricated a robust and inexpensive high-precision metal MEMS column by combining diffusion-bonded etched stainless-steel plates with alignment evaluation using acoustic microscopy. The separation performance was evaluated using a desktop GC with a flame ionization detector and we achieved the high separation performance comparable to the best silicon MEMS column fabricated using a dynamic coating method. As an application, we fabricated a palm-size surface acoustic wave (SAW) GC combining this column with a ball SAW sensor and succeeded in separating and detecting a mixture of volatile organic compounds.

  8. Single-walled carbon nanotubes as stationary phase in gas chromatographic separation and determination of argon, carbon dioxide and hydrogen.

    PubMed

    Safavi, Afsaneh; Maleki, Norooz; Doroodmand, Mohammad Mahdi

    2010-08-24

    A chromatographic technique is introduced based on single-walled carbon nanotubes (SWCNTs) as stationary phase for separation of Ar, CO(2) and H(2) at parts per million (ppm) levels. The efficiency of SWCNTs was compared with solid materials such as molecular sieve, charcoal, multi-walled carbon nanotubes and carbon nanofibers. The morphology of SWCNTs was optimized for maximum adsorption of H(2), CO(2) and Ar and minimum adsorption of gases such as N(2), O(2), CO and H(2)O vapour. To control temperature of the gas chromatography column, peltier cooler was used. Mixtures of Ar, CO(2) and H(2) were separated according to column temperature program. Relative standard deviation for nine replicate analyses of 0.2 mL H(2) containing 10 microL of each Ar or CO(2) was 2.5% for Ar, 2.8% for CO(2) and 3.6% for H(2). The interfering effects of CO, and O(2) were investigated. Working ranges were evaluated as 40-600 ppm for Ar, 30-850 ppm for CO(2) and 10-1200 ppm for H(2). Significant sensitivity, small relative standard deviation (RSD) and acceptable limit of detection (LOD) were obtained for each analyte, showing capability of SWCNTs for gas separation and determination processes. Finally, the method was used to evaluate the contents of CO(2) in air sample.

  9. Investigation of porous polymer gas chromatographic packings for atmospheric analysis of extraterrestrial bodies

    NASA Technical Reports Server (NTRS)

    Pollock, G. E.

    1986-01-01

    Measurement of the permanent gases in the atmospheres of mission targets is a major objective. A 16 meter long Porapak N column was used on the Venus probe and required a rather high carrier gas flow rate. The researchers have, therefore, surveyed commercial porous polymer types which had some ability to resolve nitrogen, oxygen, argon and carbon monoxide gases. Porapaks N and Q appeared superior to most. Batch to batch variation, however, was quite wide, so the researchers learned how to synthesize porous polymer and investigated some of the factors affecting the separations. A polymer was synthesized which was superior to all commercial products and allowed at least a 50% reduction in length and flow rate of carrier gas. Similar studies were made concerning the separation of hydrocarbons and new porous polymers have been synthesized which represent significant improvements in time of analysis, column, and carrier gas flow rate.

  10. Ammonia Analysis by Gas Chromatograph/Infrared Detector (GC/IRD)

    NASA Technical Reports Server (NTRS)

    Scott, Joseph P.; Whitfield, Steve W.

    2003-01-01

    Methods are being developed at Marshall Space Flight Center's Toxicity Lab on a CG/IRD System that will be used to detect ammonia in low part per million (ppm) levels. These methods will allow analysis of gas samples by syringe injections. The GC is equipped with a unique cryogenic-cooled inlet system that will enable our lab to make large injections of a gas sample. Although the initial focus of the work will be analysis of ammonia, this instrument could identify other compounds on a molecular level. If proper methods can be developed, the IRD could work as a powerful addition to our offgassing capabilities.

  11. A specific gas chromatographic detector for carbonyl compounds, based on polarography.

    PubMed

    Fleet, B; Risby, T H

    1969-07-01

    The evaluation of a specific gas Chromatographie detector for carbonyl compounds is described. This is based on the polarographic reduction of the Girard T hydrazone derivative which is formed when the carbonyl compound is absorbed in a buffered supporting electrolyte containing the carbonyl reagent. The detector was used to monitor the separation of a homologous series of alkanals.

  12. Gas Chromatographic Verification of a Mathematical Model: Product Distribution Following Methanolysis Reactions.

    ERIC Educational Resources Information Center

    Lam, R. B.; And Others

    1983-01-01

    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…

  13. Current Developments in Analyzing Food Volatiles by Multidimensional Gas Chromatographic Techniques.

    PubMed

    Cordero, Chiara; Schmarr, Hans-Georg; Reichenbach, Stephen E; Bicchi, Carlo

    2017-02-02

    This paper presents current developments and future perspectives on the spread of advanced analytical tasks in the field of food volatile analysis. The topics outlined comprise (a) recent advances on miniaturized sampling techniques; (b) the potential and challenges of multidimensional gas chromatography coupled with mass spectrometric detection for volatile identification and quantitation in samples with complex matrices;

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

    NASA Astrophysics Data System (ADS)

    Zhang, Yaping; Williams, Brent J.; Goldstein, Allen H.; Docherty, Kenneth S.; Jimenez, Jose L.

    2016-11-01

    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 resolution on

  15. Gas chromatographic/mass spectrometric determination of lysergic acid diethylamide (LSD) in serum samples.

    PubMed

    Musshoff, F; Daldrup, T

    1997-08-04

    A sensitive method for the detection and quantification of lysergic acid diethylamide (LSD) in serum samples is described. After liquid-liquid extraction the trimethylsilyl derivative of LSD is detected by gas chromatography-mass spectrometry. Experiments with spiked samples resulted in a recovery of 76%, the coefficient of variation was 9.3%. Excellent linearity was obtained over the range 0.1-10 ng ml-1. Additionally experiments demonstrating the light sensitivity of LSD are presented together with casuistics.

  16. Simultaneous gas chromatographic determination of dibutyltin and tributyltin compounds in biological and sediment samples

    SciTech Connect

    Tsuda, T.; Nakanishi, H.; Morita, T.; Takebayashi, J.

    1986-11-01

    A method is described for the simultaneous determination of nanogram amounts of dibutyltin and tributyltin compounds in biological and sediment samples. These compounds are converted to the corresponding chlorides with HCl, extracted with ethyl acetate-hexane (3 + 2) for biological samples and with hexane for sediment samples, and hydrogenated with sodium borohydride. The corresponding hydrides, Bu2SnH2 and Bu3SnH, are detected by electron-capture gas chromatography after cleanup by silica gel column chromatography. Detection limits are 1.0-2.0 and 0.5-1.0 ng/g, respectively, for biological and sediment samples.

  17. Development of gas chromatographic methods for the analyses of organic carbonate-based electrolytes

    NASA Astrophysics Data System (ADS)

    Terborg, Lydia; Weber, Sascha; Passerini, Stefano; Winter, Martin; Karst, Uwe; Nowak, Sascha

    2014-01-01

    In this work, novel methods based on gas chromatography (GC) for the investigation of common organic carbonate-based electrolyte systems are presented, which are used in lithium ion batteries. The methods were developed for flame ionization detection (FID), mass spectrometric detection (MS). Further, headspace (HS) sampling for the investigation of solid samples like electrodes is reported. Limits of detection are reported for FID. Finally, the developed methods were applied to the electrolyte system of commercially available lithium ion batteries as well as on in-house assembled cells.

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

    SciTech Connect

    Rotard, W.; Mailahn, W.

    1987-01-01

    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.

  19. Gas-liquid chromatographic determination of 3-trifluoromethyl-4-nitrophenol residues in fish

    USGS Publications Warehouse

    Allen, J.L.; Sills, J.B.

    1974-01-01

    A procedure for the determination of 3-mftuormethyl-4-nitrophenol (TFM) in fish tissues is described. Homogenized tissues are extracted with hexane-ethyl ether; the extract is cleaned up by partitioning the TFM from the extracting solvent into O.IN NaOB, acidifying the aqueous solution, and partitioning again with hexaneethyl ether. The TFM is methylated with diazomethane and analyzed by gas-liquid chromatography, using electron capture detection. Recoveries ranged from 75 to 1000/., from fish muscles that were spiked with 0.01-2.00 JA#g TFM/g.

  20. Gas chromatographic-mass spectrometric assay for 6-hydroxymelatonin sulfate and 6-hydroxymelatonin glucuronide in urine

    SciTech Connect

    Francis, P.L.; Leone, A.M.; Young, I.M.; Stovell, P.; Silman, R.E.

    1987-04-01

    Circulating melatonin is hydroxylated to 6-hydroxymelatonin and excreted in urine as the sulfate and glucuronide conjugates. We extracted these two compounds from urine by using octadecylsilane-bonded silica cartridges to eliminate most of the urea and electrolytes, and silica cartridges to separate the sulfate and glucuronide conjugates. After hydrolyzing the separated conjugates enzymically, we determined the free hydroxymelatonin by gas chromatography-mass spectrometry. Though recoveries were low and variable, we were able to quantify the analyte in the original sample by adding deuterated sulfate and glucuronide conjugates to the urines before extraction.

  1. MOMA Gas Chromatograph-Mass Spectrometer onboard the 2018 ExoMars Mission: results and performance

    NASA Astrophysics Data System (ADS)

    Buch, A.; Pinnick, V. T.; Szopa, C.; Grand, N.; Humeau, O.; van Amerom, F. H.; Danell, R.; Freissinet, C.; Brinckerhoff, W.; Gonnsen, Z.; Mahaffy, P. R.; Coll, P.; Raulin, F.; Goesmann, F.

    2015-10-01

    The Mars Organic Molecule Analyzer (MOMA) is a dual ion source linear ion trap mass spectrometer that was designed for the 2018 joint ESA-Roscosmos mission to Mars. The main scientific aim of the mission is to search for signs of extant or extinct life in the near subsurface of Mars by acquiring samples from as deep as 2 m below the surface. MOMA will be a key analytical tool in providing chemical (molecular and chiral) information from the solid samples, with particular focus on the characterization of organic content. The MOMA instrument, itself, is a joint venture for NASA and ESA to develop a mass spectrometer capable of analyzing samples from pyrolysis/chemical derivatization gas chromatography (GC) as well as ambient pressure laser desorption ionization (LDI). The combination of the two analytical techniques allows for the chemical characterization of a broad range of compounds, including volatile and non-volatile species. Generally, MOMA can provide information on elemental and molecular makeup, polarity, chirality and isotopic patterns of analyte species. Here we report on the current performance of the MOMA prototype instruments, specifically the demonstration of the gas chromatographymass spectrometry (GC-MS) mode of operation.

  2. Miniaturized system of a gas chromatograph coupled with a Paul ion trap mass spectrometer

    NASA Technical Reports Server (NTRS)

    Shortt, B. J.; Darrach, M. R.; Holland, Paul M.; Chutjian, A.

    2005-01-01

    Miniature gas chromatography (GC) and miniature mass spectrometry (MS) instrumentation has been developed to identify and quantify the chemical compounds present in complex mixtures of gases. The design approach utilizes micro-GC components coupled with a Paul quadrupole ion trap (QIT) mass spectrometer. Inherent to the system are high sensitivity, good dynamic range, good QIT resolution, low GC flow-rates to minimize vacuum requirements and the need for consumables; and the use of a modular approach to adapt to volatile organic compounds dissolved in water or present in sediment. Measurements are reported on system response to gaseous species at concentrations varying over four orders of magnitude. The ability of the system to deal with complicated mixtures is demonstrated, and future improvements are discussed. The GC/QIT system described herein has a mass, volume and power that are, conservatively, one-twentieth of those of commercial off-the-shelf systems. Potential applications are to spacecraft cabin-air monitoring, robotic planetary exploration and trace-species detection for residual gas analysis and environmental monitoring.

  3. Gas chromatographic/thermal energy analyzer method for N-nitrosodibenzylamine in hams processed in elastic rubber netting.

    PubMed

    Pensabene, J W; Fiddler, W

    1994-01-01

    We previously described a solid-phase extraction (SPE) procedure for determining volatile nitrosamines in hams processed in elastic rubber nettings. This same procedure was found to successfully isolate N-nitrosodibenzylamine (NDBzA), a semivolatile nitrosamine. This nitrosamine may form as a result of the reformulated rubber now used in nettings. Reformulation became necessary because of the reported presence of N-nitrosodibutylamine in both the old nettings and on the exterior portion of commercial hams. After SPE, NDBzA was quantitated by using a gas chromatographic (GC) system interfaced to a nitrosamine-specific chemiluminescence detector [thermal energy analyzer (TEA)]. The GC system was equipped with a heated interface external to the TEA furnace to facilitate quantitation of NDBzA. With separation on a packed column, the method can be used to analyze 10 volatile nitrosamines and NDBzA. Repeatability of the method for NDBzA was found to be 2.1 ppb, and the coefficient of variation (CV) was 10.6%. Analysis of 18 commercial hams from 9 different producers, purchased from local retailers, indicated that 12 were positive for NDBzA (range, 2.6-128.5 ppb). NDBzA was confirmed by GC/mass spectrometry.

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

    NASA Technical Reports Server (NTRS)

    Loftin, Kathleen; Griffin, Timothy; Captain, Janine

    2013-01-01

    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.

  5. Inverse gas chromatographic method for measurement of interactions between soy protein isolate and selected flavor compounds under controlled relative humidity.

    PubMed

    Zhou, Qiaoxuan; Cadwallader, Keith R

    2004-10-06

    An inverse gas chromatographic (IGC) method was developed to study the binding interactions between selected volatile flavor compounds and soy protein isolate (SPI) under controlled relative humidity (RH). Three volatile probes (hexane, 1-hexanol, and hexanal) at very low levels were used to evaluate and validate system performance. On the basis of the thermodynamic data and the isotherms measured at 0% RH, 1-hexanol and hexanal had higher binding affinities than hexane, which could be attributed to hydrogen-bonding interactions with SPI. At 30% RH, 1-hexanol and hexanal were retained less than at 0% RH, indicating possible competition for binding sites on the SPI surface between water and volatile probe molecules. Results showed that the thermodynamic data determined were comparable to the available literature values. Use of IGC allowed for the rapid and precise generation of sorption isotherms. Repeatability between replicate injections and reproducibility across columns were very good. IGC is a potentially high-throughput method for the sensitive, precise, and accurate measurement of flavor-ingredient interactions in low-moisture food systems.

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

    SciTech Connect

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

    2006-10-01

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

  7. Gas chromatographic separation of stereoisomers of non-protein amino acids on modified γ-cyclodextrin stationary phase.

    PubMed

    Fox, Stefan; Strasdeit, Henry; Haasmann, Stephan; Brückner, Hans

    2015-09-11

    Stereoisomers (enantiomers and diastereoisomers) of synthetic, non-protein amino acids comprising α-, β-, and γ-amino acids, including α,α-dialkyl amino acids, were converted into the respective N-trifluoroacetyl-O-methyl esters and analyzed and resolved by gas chromatography (GC) on a commercial fused silica capillary column coated with the chiral stationary phase octakis(3-O-butyryl-2,6-di-O-pentyl)-γ-cyclodextrin. This column is marketed under the trade name Lipodex(®) E. Chromatograms, retention times, and a chart displaying the retention times of approximately 40 stereoisomers of amino acids are presented. With few exceptions, baseline or almost baseline resolution was achieved for enantiomers and diastereoisomers. The chromatographic method presented is considered to be highly suitable for the elucidation of the stereochemistry of non-protein amino acids, for example in natural products, and for evaluating the enantiopurity of genetically non-coded amino acids used for the synthesis and design of conformationally tailored peptides. The method is applicable to extraterrestrial materials or can be used in experimental work related to abiotic syntheses or enantioselective destruction and amplification of amino acids.

  8. [Correlation between octanol-air partition coefficients and retention parameters of polychlorinated biphenyls on gas chromatographic columns].

    PubMed

    Zhang, Qing; Zhao, Hongxia; Chen, Jiping; Liang, Xinmiao

    2005-09-01

    Octanol-air partition coefficient (Koa) is a key descriptor for describing the partitioning of organic pollutants, especially persistent organic pollutants (POPs), between air and environmental organic phases. Thus it is necessary to determine or predict the Koa values of these compounds. A novel method was introduced to describe the quantitive relationship between the octanol-air partition coefficients and gas chromatographic (GC) retention parameters A, B values of polychlorinated diphenyls (PCBs) which are typical persistent organic pollutants. By the correlation analysis between GC retention parameters A, B values of PCBs on DB-1, DB-5 and DB-1701 columns, and their octanol-air partition coefficients, a good linear relationship was found. The stepwise multiple linear regression was used to derive binary equations with the correlation coefficients greater than 0.99, and the standard deviations are less than 0.11. In addition, based on the 153 experimental A, B values and 56 predicted A, B values, the Koa values of the remaining 190 PCBs were predicted.

  9. Development of a miniaturized diffusive sampler for true breathing-zone sampling and thermal desorption gas chromatographic analysis.

    PubMed

    Lindahl, Roger; Levin, Jan-Olof; Sundgren, Margit

    2009-07-01

    Exposure measurements should be performed as close as possible to the nose and mouth for a more correct assessment of exposure. User-friendly sampling equipment, with a minimum of handling before, during and after measurement, should not affect ordinary work. In diffusive (passive) sampling, no extra equipment as sampling pumps is needed, making the measurements more acceptable to the user. The diffusive samplers are normally attached on a shoulder, on a breast-pocket or on the lapel. There are, however, difficulties if true breathing-zone sampling is to be performed, since available diffusive samplers normally cannot be arranged close to the nose/mouth. The purpose of this work was to study the performance of a miniaturized tube type diffusive sampler attached to a headset for true breathing-zone sampling. The basis for this miniaturization was the Perkin Elmer ATD tube. Both the size of the tube and the amount of adsorbent was decreased for the miniaturized sampler. A special tube holder to be used with a headset was designed for the mini tube. The mini tube is thermally desorbed inside a standard PE tube. The new sampler was evaluated for the determination of styrene, both in laboratory experiments and in field measurements. As reference method, diffusive sampling with standard Perkin Elmer tubes, thermal desorption and gas chromatographic (GC) analysis was used. The sampling rate was determined to 0.356 mL min(-1) (CV 9.6%) and was not significantly affected by concentration, sampling time or relative humidity.

  10. Gas chromatographic fingerprinting of crude oil from Idu-Ekpeye oil spillage site in Niger-delta, Nigeria.

    PubMed

    Udoetok, Inimfon A; Osuji, Leo C

    2008-06-01

    Samples were collected from an oil polluted site in Niger-delta, Nigeria. Gas chromatographic analyses carried out on the samples revealed an abundance of n-alkanes within the n-C8-n-C23 region. The pristane/phytane ratio of 5.70 obtained for the samples depicted a plant/terrestrial source input and a possible oxic depositional environment. The n-C17/pristane and n-C18/phytane ratios of 2.80 and 2.77, respectively, suggested that the spilled oil was only slightly weathered, as corroborated by the presence of peaks in the aromatic hydrocarbon fingerprints. The polycyclic aromatic hydrocarbon (PAH) fractions showed that the hydrocarbon fractions might have undergone combustion and/or that there was bush burning at the site prior to the oil spill incidence. This is supported by the abundance of high-molecular-weight PAHs which are pyrogenic in nature. High molecular weight PAHs are products of the combustion of petroleum or its products. The phenanthrene/anthracene ratio of 0.95, fluorathene/pyrene ratio of 2.23 and the summation operator (other three to six ringed PAHs)/ summation operator (five alkylated PAHs) ratio far greater than unity (4.10) also affirm this. On the other hand, the benzo (a) anthracene to chrysene ratio of 0.24 confirms the petrogenic origin of the spilled oil because chrysene which is highly abundant is a fossil PAH.

  11. Gas-solid chromatographic analysis of automobile tailpipe emissions as a function of different engine and exhaust system modifications

    SciTech Connect

    Kang, L.; Armstrong, D.W.

    1994-12-31

    The authors developed a single, relatively short gas-solid chromatographic PLOT column and used it to separate aliphatic hydrocarbons, aromatic hydrocarbons and some inorganic gases (O{sub 2}, N{sub 2}, CO and CO{sub 2}) found in automobile exhaust. In the case of hydrocarbons, both aliphatic and aromatic components (up through alkylated-benzenes) were done in one run. Subambient temperature was needed for the oxygen-nitrogen separation, but they were easily resolved from each other and the other compounds present. The effects of different engine and exhaust system modifications on the level of compounds in the exhaust were tested. The concentrations of the emission gases varied considerably with changes in air/fuel ratio, coil voltage, use of catalytic converters and so forth. The results showed that the use of catalytic converter and a higher voltage coil tended to produce the most pronounced decreases in emissions of hydrocarbons and the catalytic converter produced the significant decrease in carbon monoxide concentrations. The results of the GSC analyses were compared to those of a commercial emission analyzer (i.e., sniffer). They showed similar trends and relative concentrations but somewhat different absolute concentrations. This may have been due to differences in the calibration of these methods.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  13. Gas chromatographic-mass spectrometric determination of adipate-based polymeric plasticizers in foods.

    PubMed

    Castle, L; Mercer, A J; Gilbert, J

    1988-01-01

    A method for the quantitative determination of adipate-based polymeric plasticizers in foods is described. The procedure involves extraction from the food and transmethylation of the polymeric plasticizer to form dimethyladipate (DMA). The derivative is cleaned up by size-exclusion chromatography and determined by capillary gas chromatography-mass spectrometry with selected ion monitoring. The use of a deuterated internal standard at the extraction stage enables quantitation by stable isotope dilution. A detection limit of 0.1 mg/kg of the polymeric plasticizer in foods and a relative standard deviation of 4% have been achieved routinely. The method has been applied successfully to the analysis of cheese, sandwiches, meat, biscuits, and cake that have been in contact with polymeric plasticized poly(vinyl chloride) films.

  14. Inverse gas chromatographic study of the oxidation stability of lubricating base oils via solubility parameter calculations.

    PubMed

    Moustafa, Nagy Emam; Eissa, Elham Ahmed

    2007-11-01

    The Flory-Huggins interaction parameter (chi1, 2(infinity)) and solubility parameter (delta2) and its hydrogen bonding sensing component (delta(h)) were determined using inverse gas chromatography (IGC). These parameters were successfully used in the probes of chemical changes that occur during the oxidation of naphthenic and paraffinic base oils in a GC column. Changes in chi1, 2(infinity) values reflect the different types of intermolecular interactions (dispersive, polar, hydrogen bonding) of the given lubricating base oil during oxidation. The obtained results showed that delta(h) component of solubility parameter is the most important parameter for probing the oxidative-chemical changes during the oxidation of given lubricating oils.

  15. Gas-liquid chromatographic determination of kepone in field-collected avian tissues and eggs

    USGS Publications Warehouse

    Stafford, C.J.; Reichel, W.L.; Swineford, D.M.; Prouty, R.M.; Gay, M.L.

    1978-01-01

    A procedure is described for determining Kepone (decachlorooctahydro-1,3,4-metheno-2H-cyclobuta [cd] pentalene-2-one) residues in avian egg, liver, and tissue. Samples were extracted with benzene-isopropanol, and the extract was cleaned up with fuming H2SO4-concentrated H2SO4. Kepone was separated from organochlorine pesticides and polychlorinated biphenyls on a Florisil column and analyzed by electron capture gas-liquid chromatography (GLC). The average recovery from spiked tissues was 86%. The analyses performed on 14 bald eagle carcasses and livers, 3 bald eagle eggs, and 14 osprey eggs show measurable levels which indicate that Kepone accumulates in the tissues of fish-eating birds. Residues were confirmed by GLC-mass spectrometry.

  16. Radioimmunological screening and gas chromatographic determination of morphine and related narcotic analgesics in post mortem blood.

    PubMed

    Cimbura, G; Koves, E

    1981-01-01

    A sensitive, reproducible, and relatively specific procedure is presented for the screening, identification, and quantitation of morphine, hydromorphone, codeine, oxycodone, and hydrocodone in autopsy blood. The drugs are isolated from whole blood by adsorption on an XAD-2 resin slurry and subsequent elution with an organic solvent mixture. Part of the resin extract is screened for morphine and related cross-reacting compounds by a commercially available radioimmunoassay (RIA) and the remainder of the same extract is analyzed by gas chromatography using a nitrogen/phosphorus detector (GC/NP). The procedure has been used frequently in forensic toxicological casework. Since toxic blood concentrations of hydrocodone have not been well documented, the results of toxicological examination of two fatalities involving this drug are presented.

  17. Gas chromatographic-mass spectrometric method for polycyclic aromatic hydrocarbon analysis in plant biota.

    PubMed

    Meudec, A; Dussauze, J; Jourdin, M; Deslandes, E; Poupart, N

    2006-03-10

    Using gas chromatography-mass spectrometry, a new method was developed for the identification and the quantification of polycyclic aromatic hydrocarbons (PAHs) in plants. This method was particularly optimised for PAH analyses in marine plants such as the halophytic species, Salicornia fragilis Ball et Tutin. The saponification of samples and their clean up by Florisil solid-phase extraction succeeded in eliminating pigments and natural compounds, which may interfere with GC-MS analysis. Moreover, a good recovery of the PAHs studied was obtained with percentages ranging from 88 to 116%. Application to the determination of PAH in a wide range of coastal halophytic plants is presented and validated the efficiency, the accuracy and the reproducibility of this method.

  18. Development of a switchable multidimensional/comprehensive two-dimensional gas chromatographic analytical system.

    PubMed

    Maikhunthod, Bussayarat; Morrison, Paul D; Small, Darryl M; Marriott, Philip J

    2010-02-26

    In this study, a new system for analysis using a dual comprehensive two-dimensional gas chromatography/targeted multidimensional gas chromatography (switchable GC x GC/targeted MDGC) analysis was developed. The configuration of this system not only permits the independent operation of GC, GC x GC and targeted MDGC analyses in separate analyses, but also allows the mode to be switched from GC x GC to targeted MDGC any number of times through a single analysis. By incorporating a Deans switch microfluidics transfer module prior to a cryotrapping device, the flow stream from the first dimension column can be directed to either one of two second dimension columns in a classical heart-cutting operation. Both second columns pass through the cryotrap to allow solute bands to be focused and then rapidly remobilized to the respective second columns. A short second column enables GC x GC operation, whilst a longer column is used for targeted MDGC. Validation of the system was performed using a standard mixture of compounds relevant to essential oil analysis, and then using compounds present at different abundances in lavender essential oil. Reproducibility of retention times and peak area responses demonstrated that there was negligible variation in the system over the course of multiple heart-cuts, and proved the reliable operation of the system. An application of the system to lavender oil, as a more complex sample, was carried out to affirm system feasibility, and demonstrate the ability of the system to target multiple components in the oil. The system was proposed to be useful for study of aroma-impact compounds where GC x GC can be incorporated with MDGC to permit precise identification of aroma-active compounds, where heart-cut multidimensional GC-olfactometry detection (MDGC-O) is a more appropriate technology for odour assessment.

  19. Gas chromatographic study of the volatile products from co-pyrolysis of coal and polyethylene wastes.

    PubMed

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

    2001-05-18

    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.

  20. Gas chromatographic separation of fatty acid esters of cholesterol and phytosterols on an ionic liquid capillary column.

    PubMed

    Hammann, Simon; Vetter, Walter

    2015-12-15

    Steryl esters are high molecular weight compounds (600-700g/mol) regularly present as a minor lipid class in animal and plant lipids. Different sterol backbones (e.g., cholesterol, β-sitosterol and brassicasterol) which can be esterified with various fatty acids can result in highly complex steryl ester patterns in food samples. The gas chromatographic (GC) analysis of intact steryl esters is challenging, since high elution temperatures are required for their elution. On nonpolar GC phases, steryl esters with fatty acids with differing degree of unsaturation (e.g., oleate and linoleate) cannot be separated and there are only few polar columns available with sufficient temperature stability. In this study, we used gas chromatography with mass spectrometry (GC/MS) and analyzed intact steryl esters on a commercial room temperature ionic liquid (RTIL) column which was shortened to a length of 12m. The column separated the steryl esters both by total carbon number and by degree of unsaturation of the fatty acid. For instance, cholesteryl esters with stearic acid (18:0), oleic acid (18:1n-9), linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3) could be resolved (R≥1.3) from each other. By analysis of synthesized standard substances, the elution orders for different steryl backbones and different fatty acids on a given sterol backbone could be determined. Analysis of spreads and plant oils allowed to determine retention times for 37 steryl esters, although a few co-elutions were observed. The ionic liquid column proved to be well-suited for the analysis of intact steryl esters.

  1. Characterization of thermal desorption with the Deans-switch technique in gas chromatographic analysis of volatile organic compounds.

    PubMed

    Ou-Yang, Chang-Feng; Huang, Ying-Xue; Huang, Ting-Jyun; Chen, Yong-Shen; Wang, Chieh-Heng; Wang, Jia-Lin

    2016-09-02

    This study presents a novel application based on the Deans-switch cutting technique to characterize the thermal-desorption (TD) properties for gas chromatographic (GC) analysis of ambient volatile organic compounds (VOCs). Flash-heating of the sorbent bed at high temperatures to desorb trapped VOCs to GC may easily produce severe asymmetric or tailing GC peaks affecting resolution and sensitivity if care is not taken to optimize the TD conditions. The TD peak without GC separation was first examined for the quality of the TD peak by analyzing a standard gas mixture from C2 to C12 at ppb level. The Deans switch was later applied in two different stages. First, it was used to cut the trailing tail of the TD peak, which, although significantly improved the GC peak symmetry, led to more loss of the higher boiling compounds than the low boiling ones, thus suggesting compound discrimination. Subsequently, the Deans switch was used to dissect the TD peak into six 30s slices in series, and an uneven distribution in composition between the slices were found. A progressive decrease in low boiling compounds and increase in higher boiling ones across the slices indicated severe inhomogeneity in the TD profile. This finding provided a clear evidence to answer the discrimination problem found with the tail cutting approach to improve peak symmetry. Through the use of the innovated slicing method based on the Deans-switch cutting technique, optimization of TD injection for highly resolved, symmetric and non-discriminated GC peaks can now be more quantitatively assessed and guided.

  2. A Gas Chromatographic Method for the Determination of Aldose and Uronic Acid Constituents of Plant Cell Wall Polysaccharides 1

    PubMed Central

    Jones, Thomas M.; Albersheim, Peter

    1972-01-01

    A major problem in determining the composition of plant cell wall polysaccharides has been the lack of a suitable method for accurately determining the amounts of galacturonic and glucuronic acids in such polymers. A gas chromatographic method for aldose analysis has been extended to include uronic acids. Cell wall polysaccharides are depolymerized by acid hydrolysis followed by treatment with a mixture of fungal polysaccharide-degrading enzymes. The aldoses and uronic acids released by this treatment are then reduced with NaBH4 to alditols and aldonic acids, respectively. The aldonic acids are separated from the alditols with Dowex-1 (acetate form) ion exchange resin, which binds the aldonic acids. The alditols, which do not bind, are washed from the resin and then acetylated with acetic anhydride to form the alditol acetate derivatives. The aldonic acids are eluted from the resin with HCl. After the resin has been removed, the HCl solution of the aldonic acids is evaporated to dryness, converting the aldonic acids to aldonolactones. The aldonolactones are reduced with NaBH4 to the corresponding alditols, dried and acetylated. The resulting alditol acetate mixtures produced from the aldoses and those from the uronic acids are analyzed separately by gas chromatography. This technique has been used to determine the changes in composition of Red Kidney bean (Phaseolus vulgaris) hypocotyl cell walls during growth, and to compare the cell wall polysaccharide compositions of several parts of bean plants. Galacturonic acid is found to be a major component of all the cell wall polysaccharides examined. PMID:16658086

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

    NASA Technical Reports Server (NTRS)

    Limero, Thomas; Cheng, Patti

    2007-01-01

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

  4. [Investigation of a gas chromatographic column system for the on-line analysis of gaseous components in de-propane tower of pyrolysis equipment].

    PubMed

    Cai, H; Liu, L J; Yan, J; Lu, X; Ye, F; Xu, G W

    2000-03-01

    Multi-dimensional gas chromatograph has become an important process analyzer due to the advantages of high resolution and fast speed. According to the production requirement, a gas chromatographic column switching system has been investigated for the on-line analysis of gaseous components from high-pressure and lower-pressure de-propane towers of pyrolysis equipment. By using two different injection times on three injectors, and fore-flush and back-flush techniques, C2-hydrocarbons, propane, propene, methylacetylene, propadiene and C4-hydrocarbons can be separated on 7 columns in 7 minutes. The practical application showed the developed column system is suitable for the on-line monitoring of the production process.

  5. Modified ion source triple quadrupole mass spectrometer gas chromatograph for polycyclic aromatic hydrocarbon analyses

    PubMed Central

    Anderson, Kim A.; Szelewski, Michael J.; Wilson, Glenn; Quimby, Bruce D.; Hoffman, Peter D.

    2015-01-01

    We describe modified gas chromatography electron-impact/triple-quadrupole mass spectrometry (GC–EI/MS/MS) utilizing a newly developed hydrogen-injected self-cleaning ion source and modified 9 mm extractor lens. This instrument, with optimized parameters, achieves quantitative separation of 62 polycyclic aromatic hydrocarbons (PAHs). Existing methods historically limited rigorous identification and quantification to a small subset, such as the 16 PAHs the US EPA has defined as priority pollutants. Without the critical source and extractor lens modifications, the off-the-shelf GC–EI/MS/MS system was unsuitable for complex PAH analysis. Separations were enhanced by increased gas flow, a complex GC temperature profile incorporating multiple isothermal periods, specific ramp rates, and a PAH-optimized column. Typical determinations with our refined GC–EI/MS/MS have a large linear range of 1–10,000 pg μl−1 and detection limits of <2 pg μl−1. Included in the 62 PAHs, multiple-reaction-monitoring (MRM) mode enabled GC-EI/MS/MS identification and quantitation of several constituents of the MW 302 PAHs isomers. Using calibration standards, values determined were within 5% of true values over many months. Standard curve r2 values were typically >0.998, exceptional for compounds which are archetypally difficult. With this method benzo[a]fluorene, benzo[b]fluorene, benzo[c]fluorene were fully separated as was benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo[j]fluoranthene. Chrysene and triphenylene, were sufficiently separated to allow accurate quantitation. Mean limits of detection (LODs) across all PAHs were 1.02 ± 0.84 pg μl−1 with indeno[1,2,3-c,d] pyrene having the lowest LOD at 0.26 pg μl−1 and only two analytes above 2.0 pg μl−1; acenaphthalene (2.33 pg μl−1) and dibenzo[a,e]pyrene (6.44 pg μl−1). PMID:26454790

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

    PubMed

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

    2015-09-09

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

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

    SciTech Connect

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

    1996-03-01

    This paper describes the application of a novel, practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This is achieved through the use of automated pereparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of individual target compounds for {sup 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 {sup 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 {Delta}{sup 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 (<5% for {delta}{sup 13}C), provided the entire peak was collected during PCGC. Trapping of partially coeluting peaks did cause errors, and these results highlight the importance of conducting stable carbon isotopic measurements of each trapped compound in concert with AMS for reliable radiocarbon measurements. 29 refs., 9 figs., 2 tabs.

  8. Gas chromatographic analysis of histamine in mahi-mahi (Coryphaena hippurus).

    PubMed

    Antoine, Francis R; Wei, Cheng-I; Otwell, W Steve; Sims, Charlie A; Littell, Ramon C; Hogle, Amanda D; Marshall, Maurice R

    2002-08-14

    Several authors have studied histamine using gas chromatography (GC) as a tool for quantitation, but the methods used were not always suitable depending on the kind of food. Problems frequently cited include incomplete histamine elution from the columns and peak tailing. Histamine is of interest because it is the factor common to all cases of scombroid poisoning, it has physiological and biological activity, and it is a chemical indicator of fish quality. In this study a modified GC method was used to quantify histamine in mahi-mahi (Coryphaena hippurus). Mean recovery was 67% for the GC method, compared with 90% for the AOAC fluorometric method. There was a 0.96 correlation of the GC histamine values with those of the AOAC fluorometric method. A temperature program, splitless/split injection, and analyte cleanup were essential for GC properties. Histamine retention time was 8.2 min. The method allowed peak height to be used for quantitation and simultaneous analysis of cadaverine and putrescine.

  9. Gas chromatographic retention index as a basis for predicting evaporation rates of complex mixtures.

    PubMed

    Mcllroy, John W; Jones, A Daniel; McGuffin, Victoria L

    2014-12-10

    Models that predict the fate of petroleum fuels in the environment are often required for effective remediation of fuel-contaminated sites. In this research, an environmental fuel spill was simulated by means of a diesel/water microcosm, in which the temporal changes in composition were assessed during evaporation by gas chromatography-mass spectrometry (GC-MS). First-order kinetic rate constants were calculated for 51 selected compounds and utilized to develop predictive models for evaporation rate constants, using GC retention indices on a nonpolar stationary phase. Models were initially developed to predict rates of evaporation of compounds from individual classes (normal alkane, branched alkane, alkyl benzene, and polycyclic hydrocarbon) and then expanded to include all compounds (comprehensive model). Using the comprehensive model, the rate constants were predicted with a mean absolute percent error (MAPE) of 10%, whereas the class-specific models resulted in less error (4-8%). These models were employed to predict the fraction remaining of the total fuel (6% error) as well as the fraction remaining of individual compounds (13% MAPE). Accurate models such as these will facilitate remediation of environmental releases of petroleum products.

  10. Determination of Milk Fat Adulteration with Vegetable Oils and Animal Fats by Gas Chromatographic Analysis.

    PubMed

    Kim, Jin-Man; Kim, Ha-Jung; Park, Jung-Min

    2015-09-01

    This study assessed the potential application of gas chromatography (GC) in detecting milk fat (MF) adulteration with vegetable oils and animal fats and of characterizing samples by fat source. One hundred percent pure MF was adulterated with different vegetable oils and animal fats at various concentrations (0%, 10%, 30%, 50%, 70%, and 90%). GC was used to obtain the fatty acid (FA) profiles, triacylglycerol (TG) contents, and cholesterol contents. The pure MF and the adulterated MF samples were discriminated based on the total concentrations of saturated FAs and on the 2 major FAs (oleic acid [C18:1n9c] and linoleic acid [C18:2n6c], TGs [C52 and C54], and cholesterol contents using statistical analysis to compared difference. These bio-markers enabled the detection of as low as 10% adulteration of non-MF into 100% pure MF. The study demonstrated the high potential of GC to rapidly detect MF adulteration with vegetable and animal fats, and discriminate among commercial butter and milk products according to the fat source. These data can be potentially useful in detecting foreign fats in these butter products. Furthermore, it is important to consider that several individual samples should be analyzed before coming to a conclusion about MF authenticity.

  11. A Practical Methodology to Measure Unbiased Gas Chromatographic Retention Factor vs. Temperature Relationships

    PubMed Central

    Peng, Baijie; Kuo, Mei-Yi; Yang, Panhia; Hewitt, Joshua T.; Boswell, Paul G.

    2014-01-01

    Compound identification continues to be a major challenge. Gas chromatography-mass spectrometry (GC-MS) is a primary tool used for this purpose, but the GC retention information it provides is underutilized because existing retention databases are experimentally restrictive and unreliable. A methodology called “retention projection” has the potential to overcome these limitations, but it requires the retention factor (k) vs. T relationship of a compound to calculate its retention time. Direct methods of measuring k vs. T relationships from a series of isothermal runs are tedious and time-consuming. Instead, a series of temperature programs can be used to quickly measure the k vs. T relationships, but they are generally not as accurate when measured this way because they are strongly biased by non-ideal behavior of the GC system in each of the runs. In this work, we overcome that problem by using the retention times of 25 n-alkanes to back-calculate the effective temperature profile and hold-up time vs. T profiles produced in each of six temperature programs. When the profiles were measured this way and taken into account, the k vs. T relationships measured from each of two different GC-MS instruments were nearly as accurate as the ones measured isothermally, showing less than 2-fold more error. Furthermore, temperature-programmed retention times calculated in five other labs from the new k vs. T relationships had the same distribution of error as when they were calculated from k vs. T relationships measured isothermally. Free software was developed to make the methodology easy to use. The new methodology potentially provides a relatively fast and easy way to measure unbiased k vs. T relationships. PMID:25496658

  12. Gas chromatographic metabolic profiling: a sensitive tool for functional microbial ecology.

    PubMed

    Coucheney, Elsa; Daniell, Tim J; Chenu, Claire; Nunan, Naoise

    2008-12-01

    Microbial metabolomics, which consists of a non-targeted analysis of the metabolites released from ('exometabolome') or existing in ('endometabolome') a cell has mostly been used to study the metabolism of particular microbes. Metabolomes also represent a picture of microbial activity and we suggest that the exometabolome may also contain pertinent information for studying microbial interaction networks. Gas chromatography coupled to mass spectrometry is the most commonly used technique in metabolomics studies. It allows a wide range of metabolites to be detected but requires the derivatisation of compounds prior to detection. This type of non-targeted analysis can introduce biases to the detection and quantification of the different metabolites, particularly at the extraction and derivatisation steps. The aims of this study, therefore, were to quantify the sources of variability and to test the sensitivity of the GC metabolic profiling approach to small environmental changes such as shifts in temperature. The temperature sensitivity of metabolic profiles was compared with that of catabolic profiles obtained using Biolog microplates. Analytical variability was compared with biological variability by incubating bacterial strains isolated from soil with fructose at 20 degrees C and by replicating each step of the protocol (incubation, extraction and derivatisation). For both the endo- and the exometabolome, more than 70% of the total variability was of biological origin and principal components analysis clearly separated the strains along the first ordination axis. The endometabolome distinguished bacterial strains at the species level only, whereas separation was evident at the species and group level with the exometabolome. Temperature had a significant but differential effect on the metabolite production of the bacterial strains whilst their catabolic profiles remained relatively unaffected. The exometabolome was more sensitive to temperature shifts than the

  13. Gas chromatographic analysis of infant formulas for total fatty acids, including trans fatty acids.

    PubMed

    Satchithanandam, Subramaniam; Fritsche, Jan; Rader, Jeanne I

    2002-01-01

    Twelve powdered and 13 liquid infant formulas were analyzed by using an extension of AOAC Official Method 996.01 for fat analysis in cereal products. Samples were hydrolyzed with 8 N HCl and extracted with ethyl and petroleum ethers. Fatty acid methyl esters were prepared by refluxing the mixed ether extracts with methanolic sodium hydroxide in the presence of 14% boron trifluoride in methanol. The extracts were analyzed by gas chromatography. In powdered formulas, saturated fatty acid (SFA) content (mean +/- SD; n = 12) was 41.05 +/- 3.94%, monounsaturated fatty acid (MUFA) content was 36.97 +/- 3.38%, polyunsaturated fatty acid (PUFA) content was 20.07 +/- 3.08%, and total trans fatty acid content was 1.30 +/- 1.27%. In liquid formulas, SFA content (mean +/- SD; n = 13) was 42.29 +/- 2.98%, MUFA content was 36.05 +/- 2.47%, PUFA content was 20.65 +/- 2.40%, and total trans fatty acid content was 0.88 +/- 0.54%. Total fat content in powdered formulas ranged from 4.4 to 5.5 g/100 kcal and linoleic acid content ranged from 868 to 1166 mg/100 kcal. In liquid formulas, total fat content ranged from 4.1 to 5.1 g/100 kcal and linoleic acid content ranged from 820 to 1100 mg/100 kcal. There were no significant differences between powdered and liquid infant formulas in concentrations of total fat, SFA, MUFA, PUFA, or trans fatty acids.

  14. Capillary gas chromatographic determination of prometryn and its degradation products in parsley.

    PubMed

    Bardalaye, P C; Wheeler, W B

    1985-01-01

    Residue analysis of the herbicide prometryn (2,4-bis(isopropylamino)-6-methylthio-1,3,5-triazine) is widely known, but an analytical method for determining its metabolities or degradation products in addition to the parent chemical has not yet been reported in the literature. The procedure reported here is for the extraction and determination of prometryn and 2 metabolites, 2-amino-4-isopropylamino-6-methyl-thio-1,3,5-triazine and 2,4-diamino-6-methylthio-1,3,5-triazine, in parsley. Crops were extracted with 2-propanol followed by concentration of the extract and partitioning with a minimum amount of hexane in the presence of a large excess of water to remove most of the green pigment. The aqueous phase was divided into 2 equal halves: (A) One-half portion was partitioned with dichloromethane in the presence of saturated sodium chloride solution, the dichloromethane phase was separated, and the aqueous phase was discarded. The organic solvent was evaporated, and the contents were reconstituted in petroleum ether before prometryn analysis. (B) The other half was made slightly alkaline with ammonium hydroxide solution and was partitioned with ethyl acetate in the presence of saturated sodium chloride solution. The ethyl acetate phase was concentrated, centrifuged to remove any turbidity, and analyzed for the 2 metabolities above. Fused silica capillary gas chromatography (GC) with nitrogen-phosphorus (N-P) detection was used for quantitation. The limit of detection was 0.05 mg/kg for all the compounds examined. Recoveries from fortified parsley samples ranged from 59 to 73% at fortification levels of 0.05 to 1.0 mg/kg.

  15. Comprehensive two-dimensional gas chromatographic separations with a temperature programmed microfabricated thermal modulator.

    PubMed

    Collin, William R; Nuñovero, Nicolas; Paul, Dibyadeep; Kurabayashi, Katsuo; Zellers, Edward T

    2016-04-29

    Comprehensive two-dimensional gas chromatography (GC×GC) with a temperature-programmed microfabricated thermal modulator (μTM) is demonstrated. The 0.78 cm(2), 2-stage μTM chip with integrated heaters and a PDMS coated microchannel was placed in thermal contact with a solid-state thermoelectric cooler and mounted on top of a bench scale GC. It was fluidically coupled through heated interconnects to an upstream first-dimension ((1)D) PDMS-coated capillary column and a downstream uncoated capillary or second-dimension ((2)D) PEG-coated capillary. A mixture of n-alkanes C6-C10 was separated isothermally and the full-width-at-half-maximum (fwhm) values of the modulated peaks were assessed as a function of the computer-controlled minimum and maximum stage temperatures of μTM, Tmin and Tmax, respectively. With Tmin and Tmax fixed at -25 and 100°C, respectively, modulated peaks of C6 and C7 had fwhm values<53 ms while the modulated peaks of C10 had a fwhm value of 1.3s, due to inefficient re-mobilization. With Tmin and Tmax fixed at 0 and 210°C, respectively, the fwhm value for the modulated C10 peaks decreased to 67 ms, but C6 and C7 exhibited massive breakthrough. By programming Tmin from -25 to 0°C and Tmax from 100 to 220°C, the C6 and C7 peaks had fwhm values≤50 ms, and the fwhm for C10 peaks remained<95 ms. Using the latter conditions for the GC×GC separation of a sample of unleaded gasoline yielded resolution similar to that reported with a commercial thermal modulator. Replacing the PDMS phase in the μTM with a trigonal-tricationic room temperature ionic liquid eliminated the bleed observed with the PDMS, but also reduced the capacity for several test compounds. Regardless, the demonstrated capability to independently temperature program this low resource μTM enhances its versatility and its promise for use in bench-scale GC×GC systems.

  16. Evaluation of a Gas Chromatograph-Differential Mobility Spectrometer for Potential Water Monitoring on the International Space Station

    NASA Technical Reports Server (NTRS)

    Wallace, William T.; Limero, Thomas F.; Gazda, Daniel B.; Macatangay, Ariel V.; Dwivedi, Prabha; Fernandez, Facundo M.

    2015-01-01

    Environmental monitoring for manned spaceflight has long depended on archival sampling, which was sufficient for short missions. However, the longer mission durations aboard the International Space Station (ISS) have shown that enhanced, real-time monitoring capabilities are necessary in order to protect both the crewmembers and the spacecraft systems. Over the past several years, a number of real-time environmental monitors have been deployed on the ISS. Currently, volatile organic compounds (VOCs) in the station air are monitored by the Air Quality Monitor (AQM), a small, lightweight gas chromatograph-differential mobility spectrometer. For water monitoring, real-time monitors are used for total organic carbon (TOC) and biocide analysis. No information on the actual makeup of the TOC is provided presently, however. An improvement to the current state of environmental monitoring could be realized by modifying a single instrument to analyze both air and water. As the AQM currently provides quantitative, compound-specific information for VOCs in air samples, this instrument provides a logical starting point to evaluate the feasibility of this approach. The major hurdle for this effort lies in the liberation of the target analytes from the water matrix. In this presentation, we will discuss our recent studies, in which an electro-thermal vaporization unit has been interfaced with the AQM to analyze target VOCs at the concentrations at which they are routinely detected in archival water samples from the ISS. We will compare the results of these studies with those obtained from the instrumentation routinely used to analyze archival water samples.

  17. Rule-based expert system for evaluating the quality of long-term, in-situ, gas chromatographic measurements of atmospheric methane. Technical memo

    SciTech Connect

    Masarie, K.A.; Steele, L.P.; Lang, P.M.

    1991-11-01

    Methane is an important trace constituent of the earth's atmosphere because it is active both chemically and radiatively. The absorption of infrared radiation by atmospheric methane, and the rapid increase in the global atmospheric burden of methane over the past century combine to raise concerns that continued increases may contribute to global warming and climate change within the next century. The use of a rule-based expert system to assess the integrity of in situ gas chromatographic methane measurements made at the NOAA/CMDL Point Barrow, Alaska and Mauna Loa, Hawaii observatories is presented. The expert system flags ambient samples analyzed during chromatograph system instability and excludes them from further scientific analysis. The development and implementation of the expert system are described in detail. A comparison between data sets flagged by a human expert and by the expert system shows that the expert system can successfully reproduce the efforts of a human when evaluating gas chromatograph system stability. Advantages and limitations of the use of an expert system for the task are also discussed.

  18. Gibbs energy additivity approaches to QSRR in generating gas chromatographic retention time for identification of fatty acid methyl ester.

    PubMed

    Pojjanapornpun, Siriluck; Aryusuk, Kornkanok; Lilitchan, Supathra; Krisnangkura, Kanit

    2017-02-06

    The Gibbs energy additivity method was used to correlate the retention time (t R) of common fatty acid methyl esters (FAMEs) to their chemical structures. The t R of 20 standard FAMEs eluted from three capillary columns of different polarities (ZB-WAXplus, BPX70, and SLB-IL111) under both isothermal gas chromatography and temperature-programmed gas chromatography (TPGC) conditions were accurately predicted. Also, the predicted t R of FAMEs prepared from flowering pak choi seed oil obtained by multistep TPGC with the BPX70 column were within 1.0% of the experimental t R. The predicted t R or mathematical t R (t R(math)) values could possibly be used as references in identification of common FAMEs. Hence, FAMEs prepared from horse mussel and fish oil capsules were chromatographed on the BPX70 and ZB-WAXplus columns in single-step and multistep TPGC. Identification was done by comparison of t R with the t R of standard FAMEs and with t R(math). Both showed correct identifications. The proposed model has six numeric constants. Five of six could be directly transferred to other columns of the same stationary phase. The first numeric constant (a), which contained the column phase ratio, could also be transferred with the adjustment of the column phase ratio to the actual phase ratio of the transferred column. Additionally, the numeric constants could be transferred across laboratories, with similar correction of the first numeric constant. The TPGC t R predicted with the transferred column constants were in good agreement with the reported experimental t R of FAMEs. Moreover, hexane was used in place of the conventional t M marker in the calculation. Hence, the experimental methods were much simplified and practically feasible. The proposed method for using t R(math) as the references would provide an alternative to the uses of real FAMEs as the references. It is simple and rapid and with good accuracy compared with the use of experimental t R as references.

  19. High-pressure/high-temperature gas-solubility study in hydrogen-phenanthrene and methane-phenanthrene systems using static and chromatographic techniques

    SciTech Connect

    Malone, P.V.

    1987-01-01

    The design and discovery of sources for alternative energy such as coal liquefaction has become of major importance over the past two decades. One of the major problems in such design in the lack of available data, particularly, for gas solubility in polycyclic aromatics at high temperature and pressure. Static and gas-liquid partition chromatographic methods were used for the study of hydrogen-phenanthrene and methane-phenanthrene systems. The static data for these two binaries were taken along 398.2, 423.2, 448.2, and 473.2 K isotherms up to 25.23 MPa. Gas-liquid partition chromatography was used to study the infinite dilution behavior of methane, ethane, propane, n-butane, and carbon dioxide in the hydrogen-phenanthrene system as well as hydrogen, ethane, n-butane, and carbon dioxide in the methane-phenanthrene binary. The principle objective was to examine the role of the elution gas. Temperatures were along the same isotherms as the static data and up to 20.77 MPa. With the exception of carbon dioxide, Henry's constants were calculated for all systems. Expressions for the heat of solution as a function of pressure were derived for both binary and chromatographic data. Estimates of delta H/sub i/sup sol/ at high pressure were presented.

  20. Field gas chromatograph analyses of gases from a glowing dome at Merapi volcano, Java, Indonesia, 1977, 1978, 1979

    NASA Astrophysics Data System (ADS)

    Le Guern, F.; Gerlach, T. M.; Nohl, A.

    1982-12-01

    A new field gas chromatograph (FGC) and conventional evacuated bottle (EB) techniques have been used to study high temperature (> 600°C) volcanic gases from Merapi Volcano, Indonesia during 1977, 1978, and 1979. The FGC design allows analysis of H 2O, CO 2, SO 2, H 2S, H 2, COS, CH 4, CO, N 2, Ar, and O 2 in a manner that prevents loss of sulfur and water by condensation, inhibits corrosion from reactions of gases with lead-in tubes, and minimizes atmospheric contamination. The FGC analyses are highly superior to the EB data especially with respect to prevention of sulfur loss from reaction of SO 2 and H 2S. In addition to providing much improved H 2S data, the FGC system minimizes oxidation of H 2 and CO from contaminating atmospheric O 2 because of the elimination of a lengthy time interval between collection and analysis. Thermodynamic calculations indicated small errors for H 2 and CH 4 in the 1978 analyses provided by the proto-type FGC device. A later model FGC provided excellent analyses that were shown by thermodynamic calculations to be nearly equilibrium mixtures, requiring only minor corrections. The Merapi gases are H 2O-rich (88-95%) containing small amounts of CO 2 (3.5 to 7.5%), SO 2 (0.3 to 1.2%), and H 2S (0.3 to 1.2%). They resemble "excess volatiles" (Rubey,1955) except for too high a sulfur content. Thermodynamic calculations based on the analyses indicate that the gases were once at temperatures of at least 915°C with O 2 fugacities near quartz -magnetite-fayalite and that they have not been significantly diluted by disequilibrium admixture of meteoric water below these temperatures. This conclusion takes on special importance because stable isotope studies (Allard, 1980, 1982) of Merapi gases have shown that the water is meteoric and that much of the carbon and sulfur could be from sedimentary sources. The Merapi gases, therefore, may be "magmatic" even though they are not "juvenile" but recycled crustal volatiles.

  1. Solid-phase extraction with styrene-divinylbenzene sorbent for high-performance liquid or gas chromatographic determination of urinary chloro- and methylthiotriazines.

    PubMed

    Mendas, G; Drevenkar, V; Zupancic-Kralj, L

    2001-05-25

    A solid-phase extraction (SPE) procedure on a styrene-divinylbenzene (SDB-1 cartridge) for extraction and cleaning of the triazine herbicides atrazine, simazine, ametryn, and prometryn and atrazine monodealkylated metabolites from urine samples was developed and optimised for final high-performance liquid chromatographic (HPLC-UV diode array detection) and gas chromatographic (GC-electron-capture detection and GC-thermionic-sensitive detection) analyses. Interfering polar matrices were eliminated by rinsing SDB-1 with 1% acetonitrile in water or with pure water. Extraction recoveries were from 78 to 101% with an RSD of about 10% for all studied compounds. The extraction recovery for the didealkylated atrazine metabolite was significantly lower and this compound cannot be determined with these procedures. Sorbent matrix generated interferences, although not detected by the chromatographic system, lowered the response of nitrogen-phosphorus and electron-capture GC detectors for monodealkylated chlorotriazines when compared to standards prepared in n-hexane. HPLC and GC analysis with SPE (SDB-1) preconcentration showed excellent linearity over the concentration range tested, with detection limits in urine of 10 ng ml(-1) for the parent herbicides (HPLC and GC analysis) and 20 ng ml(-1) for monodealkylated chlorotriazines (HPLC analysis).

  2. A quantitative gas-liquid chromatographic method for the estimation of hecogenin and tigogenin in the leaves, juice and sapogenin concentrates of Agave sisalana.

    PubMed

    Cripps, A L; Blunden, G

    1978-05-01

    A gas-liquid chromatographic method has been devised for the routine estimation of the hecogenin [3beta-hydroxy-(25R)-5beta-spirostan-12-one] and tigogenin [ (25R)-5beta-spirostan-3beta-ol] contents of Agave sisalana leaf and juice samples and of the crude sapogenin concentrates known as "coffee grounds". Because of partial degradation of the sapogenins in the GLC system it was found necessary to acetylate the compounds prior to their estimation. In East African samples the tigogenin proportion of the total sapogenin content is usually about 10%. At this level, the 95% inverse tolerance limits on predicted tigogenin weights are approximately +/- 7%.

  3. Direct quantitative gas chromatographic separation of C2-C6 fatty acids, methanol, and ethyl alcohol in aqueous microbial fermentation media.

    PubMed

    Rogosa, M; Love, L L

    1968-02-01

    A method is described for the direct quantitative gas chromatographic separation of C(2)-C(6) lower fatty acid homologues, methanol, and ethyl alcohol in aqueous microbial fermentation media. A hydrogen flame detector and a single-phase solid column packing, comprising beads of a polyaromatic resin (polystyrene cross-linked with divinyl benzene), were employed. Direct injections of 1 to 10 muliters of aqueous culture supernatant fluids were made. Quantitative recoveries of C(2)-C(6) acids added to culture supernatant fluids were obtained.

  4. Direct Quantitative Gas Chromatographic Separation of C2-C6 Fatty Acids, Methanol, and Ethyl Alcohol in Aqueous Microbial Fermentation Media

    PubMed Central

    Rogosa, M.; Love, L. L.

    1968-01-01

    A method is described for the direct quantitative gas chromatographic separation of C2-C6 lower fatty acid homologues, methanol, and ethyl alcohol in aqueous microbial fermentation media. A hydrogen flame detector and a single-phase solid column packing, comprising beads of a polyaromatic resin (polystyrene cross-linked with divinyl benzene), were employed. Direct injections of 1 to 10 μliters of aqueous culture supernatant fluids were made. Quantitative recoveries of C2-C6 acids added to culture supernatant fluids were obtained. PMID:5645415

  5. A water extraction, static headspace sampling, gas chromatographic method to determine MTBE in heating oil and diesel fuel.

    PubMed

    Cummins, T M; Robbins, G A; Henebry, B J; Goad, C R; Gilbert, E J; Miller, M E; Stuart, J D

    2001-03-15

    A method was developed to determine the fuel/water partition coefficient (KMTBE) of methyl tert-butyl ether (MTBE) and then used to determine low parts per million concentrations of MTBE in samples of heating oil and diesel fuel. A special capillary column designed for the separation of MTBE and to prevent coelution and a gas chromatograph equipped with a photoionization detector (PID) were used. MTBE was partitioned from fuel samples into water during an equilibration step. The water samples were then analyzed for MTBE using static headspace sampling followed by GC/PID. A mathematical relationship was derived that allowed a KMTBE value to be calculated by utilizing the fuel/water volume ratios and the corresponding PID signal. KMTBE values were found to range linearly from 3.8 to 10.9 over a temperature range of 5-40 degrees C. This analysis method gave a MDL of 0.7 ppm MTBE in the fuel and a relative average accuracy of +/-15% by comparison with an independent laboratory using purge and trap GC/ MS analysis. MTBE was found in home heating oil in residential tanks and in diesel fuel at service stations throughout the state of Connecticut. The levels of MTBE were found to vary significantly with time. Heating oil and diesel fuel from terminals were also found to contain MTBE. This research suggests thatthe reported widespread contamination of groundwater with MTBE may also be due to heating oil and diesel fuel releases to the environment. used extensively for the past 20 years as a gasoline additive (up to 15 wt %) to reduce automobile carbon monoxide and hydrocarbon emissions. The fact that MTBE is highly soluble in water (approximately 5 wt %) (3) and chemically inert when compared to other fuel constituents causes it to be often detected at high concentrations in groundwater in the vicinity of gasoline spills. The EPA has reported that low levels of MTBE in drinking water (above 40 microg/L) may cause unpleasant taste and odors and has designated MTBE as a

  6. Determination of hexanal as an oxidative marker in vegetable oils using an automated dynamic headspace sampler coupled to a gas chromatograph/mass spectrometer.

    PubMed

    Ha, Jaeho; Seo, Dong-Won; Chen, Xi; Hwang, Jin-Bong; Shim, You-Shin

    2011-01-01

    An automated dynamic headspace sampler coupled to a gas chromatograph/mass spectrometer was evaluated as an oxidative marker to determine hexanal content in vegetable oils. For the effective analysis, a cooled injection system (CIS) was used to focus and to introduce the hexanal desorbed from the Tenax TA. The temperature of the CIS was maintained at -60 °C for 12 min before desorbing the hexanal. Hexanal was separated on a capillary column (DB-5, 0.25 mm × 60 m, 0.25 µm in film thickness) from 50 to 230 °C, followed by mass spectrometer-selected ion monitoring analysis at m/z 56. The instrumental response to hexanal was highly linear from 10 ng mL(-1) to 1 µg mL(-1) (r(2) = 0.9999). The relative standard deviation (RSD) of intra- and inter-day repeatability was acceptable, with values of less than 3.88 and 4.25%, respectively. The LOD and LOQ of hexanal were determined by gas chromatograph/mass spectrometer-selected ion monitoring to be 3.3 and 9.8 ng mL(-1), respectively. The acid value, peroxide value and fatty acid composition revealed a good correlation with the hexanal concentration.

  7. Sequential determination of triglycerides and free fatty acids in biological fluids by use of a continuous pretreatment module coupled to a gas chromatograph.

    PubMed

    Cárdenas, M S; Ballesteros, E; Gallego, M; Valcárcel, M

    1994-11-01

    A continuous system coupled to a gas-liquid chromatograph was used for the sequential determination of triglycerides and free fatty acids in serum and urine. The module provides compositional information and hence more detailed information on lipid metabolism changes in patients suffering metabolic disorders. Lipids in biological samples are manually extracted in methanol-n-hexane and introduced into the flow system; free fatty acids are then separated by retention on an ion-exchange resin and triglycerides (not retained) are transesterified with acetyl chloride in methanol. The resulting methyl esters are continuously injected into the gas chromatograph and determined by using a flame ionization detector. In a second step, retained free fatty acids are eluted and derivatized (also with acetyl chloride in methanol) and subsequently determined similarly as the triglycerides. The proposed method was applied to the determination of triglycerides in a lipid control serum; free fatty acids were determined in a human pool serum by the proposed method and compared with the volumetric method used in clinical practice. The results obtained in both instances showed good agreement between the results provided for triglycerides and free fatty acids. The proposed method was also applied to urine samples; a parallel recovery study was also made in order to assess the performance of the method.

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

    PubMed

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

    2013-11-01

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

  9. Exploring atmospheric photooxidation with a new Gas Chromatograph Time-of-Flight Chemical Ionization Mass Spectrometer (GC-ToF-CIMS)

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Allen, H. M.; Teng, A.; Crounse, J.; Wennberg, P. O.

    2015-12-01

    Atmospheric photooxidation is a fundamental process that effectively removes pollutants and greenhouse gases from the air we breathe. One way to explore these processes is to directly measure the stable intermediate oxidation products. Chemical Ionization Mass Spectrometry (CIMS) has proven to be a powerful tool to sensitively detect with high time resolution photooxidation products in the atmosphere such as hydroperoxides, acids, nitrates, and other oxygenated volatile organic compounds. Despite the potential to elucidate atmospheric photooxidation in detail, field observations of such compounds are sparse. Here we present the development of a new Gas Chromatograph Time-of-Flight Chemical Ionization Mass Spectrometer (GC-ToF-CIMS) for field deployment. Using low pressure gas chromatography and CF3O- ionization chemistry, the selective operation of a GC is combined with the sensitive, specific, and fast detection of a high-resolution ToF-CIMS. The combination of chromatographic separation and exact mass identification allows detecting isomer resolved photooxidation products. Direct measurements in the atmosphere of such isomer distributions are particularly interesting due to the broad range of their individual atmospheric lifetimes and impacts.

  10. 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.

    PubMed

    Vryzas, Zisis; Papadopoulou-Mourkidou, Euphemia

    2002-08-28

    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) < 20%. The limits of quantification (LOQ) and limits of detection (LOD) are 10 and 1 to 5 microg/kg, respectively. The method was validated with two types of soils containing 1.5 and 3.0% organic matter content, respectively; no statistically significant differences were found between solute recovery values from the two types of soils. The solute mean recovery values from freshly spiked (24 h aging) and spiked samples stored refrigerated for one week before processed were also not statistically different. Residue levels determined in field weathered soils were higher when soils were processed by MAE than with a comparison method based on flask-shaking of soil suspensions overnight. Extracts were analyzed by a gas chromatographic system equipped either with a thermionic (GC-NPD) or a mass spectrometric detector (GC-MS).

  11. Prototype of the gas chromatograph - mass spectrometer to investigate volatile species in the lunar soil for the Luna-Glob and Luna-Resurs missions.

    NASA Astrophysics Data System (ADS)

    Hofer, L.; Lasi, D.; Tulej, M.; Wurz, P.; Cabane, M.; Cosica, D.; Gerasimov, M.; Rodinov, D.

    2013-09-01

    In preparation for the Russian Luna-Glob and Luna-Resurs missions we combined our compact time-offlight mass spectrometer (TOF-MS) with a chemical pre-separation of the species by gas chromatography (GC). Combined measurements with both instruments were successfully performed with the laboratory prototype of the mass spectrometer and a flight-like gas chromatograph. Due to its capability to record mass spectra over the full mass range at once with high sensitivity and a dynamic range of up to 106 within 1s, the TOF-MS system is a valuable extension of the GC analysis. The combined GC-MS complex is able to detect concentrations of volatile species in the sample of about 2·10^-9 by mass.

  12. Solving chromatographic challenges in comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry using multivariate curve resolution-alternating least squares.

    PubMed

    Parastar, Hadi; Radović, Jagoš R; Bayona, Josep M; Tauler, Roma

    2013-07-01

    Multivariate curve resolution-alternating least squares (MCR-ALS) analysis is proposed to solve chromatographic challenges during two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOFMS) analysis of complex samples, such as crude oil extract. In view of the fact that the MCR-ALS method is based on the fulfillment of the bilinear model assumption, three-way and four-way GC × GC-TOFMS data are preferably arranged in a column-wise superaugmented data matrix in which mass-to-charge ratios (m/z) are in its columns and the elution times in the second and first chromatographic columns are in its rows. Since m/z values are common for all measured spectra in all second-column modulations, unavoidable chromatographic challenges such as retention time shifts within and between GC × GC-TOFMS experiments are properly handled. In addition, baseline/background contributions can be modeled by adding extra components to the MCR-ALS model. Another outstanding aspect of MCR-ALS analysis is its extreme flexibility to consider all samples (standards, unknowns, and replicates) in a single superaugmented data matrix, allowing joint analysis. In this way, resolution, identification, and quantification results can be simultaneously obtained in a very fast and reliable way. The potential of MCR-ALS analysis is demonstrated in GC × GC-TOFMS analysis of a North Sea crude oil extract sample with relative errors in estimated concentrations of target compounds below 6.0 % and relative standard deviations lower than 7.0 %. The results obtained, along with reasonable values for the lack of fit of the MCR-ALS model and high values of the reversed match factor in mass spectra similarity searches, confirm the reliability of the proposed strategy for GC × GC-TOFMS data analysis.

  13. Gas chromatographic methods for determination of gamma-BHC in technical emulsifiable concentrates and water-dispersible powder formulations and in lindane shampoo and lotion: collaborative study.

    PubMed

    Miles, J W; Mount, D L; Beckmann, T J; Carrigan, S K; Galoux, I M; Hitos, P; Hodge, M C; Kissler, K; Martijn, A; Sanchez-Rasero, F

    1984-01-01

    Although the gas chromatographic separation of the isomers of BHC was demonstrated two decades ago, the present AOAC method of analysis of BHC for gamma-isomer (lindane) content is based on a separation carried out on a liquid chromatographic partition column. A method of analysis has been developed that uses an OV-210 column for separation of the gamma-isomer from the other isomers and impurities in technical BHC. Di-n-propyl phthalate was chosen as an internal standard. The same system allows quantitation of lindane in lotion and shampoo after these products are extracted with ethyl acetate-isooctane (1 + 4). The analytical methods were subjected to a collaborative trial with 10 laboratories. The coefficient of variation for technical BHC was 2.83%. For the water-dispersible powder and emulsifiable concentrate, the coefficients of variation were 2.89% and 4.62%, respectively. Coefficients of variation for 1% lindane lotion and shampoo were 4.36% and 11.92%, respectively. The method has been adopted official first action.

  14. Separation of the fatty acids in menhaden oil as methyl esters with a highly polar ionic liquid gas chromatographic column and identification by time of flight mass spectrometry.

    PubMed

    Fardin-Kia, Ali Reza; Delmonte, Pierluigi; Kramer, John K G; Jahreis, Gerhard; Kuhnt, Katrin; Santercole, Viviana; Rader, Jeanne I

    2013-12-01

    The fatty acids contained in marine oils or products are traditionally analyzed by gas chromatography using capillary columns coated with polyethylene glycol phases. Recent reports indicate that 100 % cyanopropyl siloxane phases should also be used when the analyzed samples contain trans fatty acids. We investigated the separation of the fatty acid methyl esters prepared from menhaden oil using the more polar SLB-IL111 (200 m × 0.25 mm) ionic liquid capillary column and the chromatographic conditions previously optimized for the separation of the complex mixture of fatty acid methyl esters prepared from milk fat. Identifications of fatty acids were achieved by applying Ag(+)-HPLC fractionation and GC-TOF/MS analysis in CI(+) mode with isobutane as the ionization reagent. Calculation of equivalent chain lengths confirmed the assignment of double bond positions. This methodology allowed the identification of 125 fatty acids in menhaden oil, including isoprenoid and furanoid fatty acids, and the novel 7-methyl-6-hexadecenoic and 7-methyl-6-octadecenoic fatty acids. The chromatographic conditions applied in this study showed the potential of separating in a single 90-min analysis, among others, the short chain and trans fatty acids contained in dairy products, and the polyunsaturated fatty acids contained in marine products.

  15. Improved gas chromatographic method for determination of daminozide by alkaline hydrolysis and 2-nitrobenzaldehyde derivatization and survey results of daminozide in agricultural products.

    PubMed

    Steinbrecher, K; Saxton, W L; Oehler, G A

    1990-01-01

    An improved method was developed for the quantitative determination of daminozide. This new method combines the alkaline hydrolysis and distillation steps of the PAM II method for daminozide with the derivatization, cleanup, and gas chromatographic determination steps of the Wright method for unsymmetrical dimethyl hydrazine (UDMH). The minimum detectable level is 0.05 ppm. Recoveries range from 85 to 110% when daminozide is added at 0.1 to 1.0 ppm, and are generally 40% at the 0.05 ppm level. A variety of domestic and imported products were analyzed by this improved method and daminozide was detected in 33 of the 98 samples analyzed. Levels detected ranged from a trace amount to 0.80 ppm. The identity of UDMH hydrazone was confirmed by mass spectrometry in many samples, thus confirming the presence of daminozide. Two samples containing daminozide were analyzed independently by a second laboratory and the findings were closely duplicated.

  16. Rapid differentiation of the major causative agents of bacterial meningitis by use of frequency-pulsed electron capture gas-liquid chromatograph: analysis of acids.

    PubMed

    Brooks, J B; Kellogg, D S; Shepherd, M E; Alley, C C

    1980-01-01

    The major causative agents of bacterial meningitis, Haemophilus influenzae serogroup B, Neisseria meningitidis serogroups B and C, Klebsiella pneumoniae, Streptococcus pneumoniae, and two types of Escherichia coli, were cultured in a modified chemically defined Catlin medium and in a commercial version of the unmodified Catlin medium. The spent media were extracted under acidic conditions, and electron-capturing derivatives were prepared by derivatization with trichloroethanol or haptafluorobutyric anhydride. The derivatives were analyzed on a gas chromatograph equipped with a frequency-pulsed electron capture detector and a PEP-2 computer. The data obtained from the study show that these organisms can be easily distinguished from each other on the basis of metabolic products detected in either type of medium. Three different metabolic groups were detected within two serogroups of N. meningitidis. The methods are practical, and the new technique should offer clinical laboratories and hospitals a better method for rapid identification of this important group of pathogens.

  17. Rapid screening of phytosterols in orange juice by solid-phase microextraction on polyacrylate fibre derivatisation and gas chromatographic-mass spectrometric.

    PubMed

    Balme, Sébastien; Gülaçar, Fazil O

    2012-05-01

    The potential of solid-phase microextraction on polyacrylate coated fibre, with sequential or simultaneous trimethylsilyl derivatisation followed by gas chromatographic-mass spectrometric analysis, was evaluated for a rapid determination of the distribution of the phytosterols in aqueous food matrixes. Influences of different parameters (bis(trimethylsilyl)trifluoro-acetamide and sterol exposure time, sterol concentration and experimental protocol) on the recovery of sterols were investigated to determine optimum conditions which were tested for sterol extraction and analysis from orange juice. Best selectivity, sterol recovery and derivatisation yields were obtained by extraction and simultaneous derivatisation through immersion of the SPME-PA fibre in the orange juice (10min, 65°C) after headspace absorption of BSTFA (30min, 65°C) on the fibre. Nevertheless the method developed cannot be used for quantitative analysis. But the possibility to effect rapid screen of phytosterol containing in complex media have been shown.

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

    PubMed

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

    2014-12-29

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

  19. Evaluation of poly(90% biscyanopropyl/10% cyanopropylphenyl siloxane) capillary columns for the gas chromatographic quantification of trans fatty acids in non-hydrogenated vegetable oils.

    PubMed

    Delmonte, Pierluigi

    2016-08-19

    Current gas chromatographic (GC) methods for the analysis of fatty acids (FA) were optimized primarily for the quantification of the trans 18:1 FAs (18:1 tFAs) produced during the partial hydrogenation of fats and oils. Recent regulatory action regarding the application of partial hydrogenation in the processing of edible fats and oils may reshape the FA composition of these products. The higher content in 18:3 tFAs compared to 18:1 tFAs of most refined non-hydrogenated vegetable oils (RNHVO), and the challenge in their quantification applying current methods, suggest the need for new methodologies. This manuscript describes a simple GC method for the analysis of FAs in RNHVOs utilizing a 100m (0.25mm I.D.) capillary column coated with poly(90% biscyanopropyl/10% cyanopropylphenyl siloxane) (90% BCS). The optimization of the chromatographic conditions and the detection of co-eluting compounds were carried out by applying comprehensive two dimensional gas chromatography with online reduction (GC-OR×GC). Results showed that 90% BCS capillary columns operated at the elution temperature of 162°C provide the separation of the 18:1, 18:2 and 18:3 tFAs, contained in RNHVOs, from other components. A minor constituent of Canola oil, 16:3n-3, partially co-eluted with trans-18:1 FAMEs. This simple GC method showed the ability to measure trans-fat in RNHVOs at the level of 0.5g/100g, providing comparable quantitative results to the more complex GC×GC methodology.

  20. The Composition of Titan's Lower Atmosphere and Simple Surface Volatiles as Measured by the Cassini-Huygens Probe Gas Chromatograph Mass Spectrometer Experiment

    NASA Technical Reports Server (NTRS)

    Niemann, H. B.; Atreya, S. K.; Demick, J. E.; Gautier, D.; Haberman, J. A.; Harpold, D. N.; Kasprzak, W. T.; Lunine, J. I.; Owen, T. C.; Raulin, F.

    2010-01-01

    The Cassini-Huygens Probe Gas Chromatograph Mass Spectrometer (GCMS) determined the composition of the Titan atmosphere from 140km altitude to the surface. After landing, it returned composition data of gases evaporated from the surface. Height profiles of molecular nitrogen (N2), methane (CH4) and molecular hydrogen (H2) were determined. Traces were detected on the surface of evaporating methane, ethane (C2H6), acetylene (C2H2), cyanogen (C2N2) and carbon dioxide (CO2). The methane data showed evidence that methane precipitation occurred recently. The methane mole fraction was (1.48+/-0.09) x 10(exp -2) in the lower stratosphere (139.8 km to 75.5 km) and (5.65+/-0.18) x 10(exp -2) near the surface (6.7 km to the surface). The molecular hydrogen mole fraction was (1.01+/-0.16) x 10(exp -3) in the atmosphere and (9.90+/-0.17) x 10(exp -4) on the surface. Isotope ratios were 167.7+/-0.6 for N-14/N-15 in molecular nitrogen, 91.1+/-1.4 for C-12/C-13 in methane and (1.35+/-0.30) x 10(exp -4) for D/H in molecular hydrogen. The mole fractions of Ar-36 and radiogenic Ar-40 are (2.1+/-0.8) x 10(exp -7) and (3.39 +/-0.12) x 10(exp -5) respectively. Ne-22 has been tentatively identified at a mole fraction of (2.8+/-2.1) x 10(exp -7) Krypton and xenon were below the detection threshold of 1 x 10(exp -8) mole fraction. Science data were not retrieved from the gas chromatograph subsystem as the abundance of the organic trace gases in the atmosphere and on the ground did not reach the detection threshold. Results previously published from the GCMS experiment are superseded by this publication.

  1. Prototype of the gas chromatograph-mass spectrometer to investigate volatile species in the lunar soil for the Luna-Resurs mission

    NASA Astrophysics Data System (ADS)

    Hofer, L.; Wurz, P.; Buch, A.; Cabane, M.; Coll, P.; Coscia, D.; Gerasimov, M.; Lasi, D.; Sapgir, A.; Szopa, C.; Tulej, M.

    2015-06-01

    In preparation for the Russian Luna-Resurs mission we combined our compact time-of-flight mass spectrometer (TOF-MS) with a chemical pre-separation of the species by gas chromatography (GC). Coupled measurements with both instruments were successfully performed with the prototype of the mass spectrometer and a flight-like gas chromatograph. The system was tested with two test gas mixtures, a mixture of hydrocarbons and a mixture of noble gases. Due to its capability to record mass spectra over the full mass range at once with high sensitivity and a dynamic range of up to 106 within 1 s, the TOF-MS system is a valuable extension of the GC analytical system. Based on the measurements with calibration gases performed with the combined GC-MS prototype and under assumption of mean characteristics for the Moon's regolith, the detection limit for volatile species in a soil sample is estimated to 2·10-10 by mass for hydrocarbons and 2·10-9 by mass for noble gases.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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

  3. High performance liquid chromatographic separations of gas oil samples and their hydrotreated products using commercial normal phases.

    PubMed

    Oro, Nicole E; Lucy, Charles A

    2011-10-28

    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.

  4. Gas chromatographic-mass spectrometric analysis of essential oils from Pimpinella species gathered from Central and Northern Turkey.

    PubMed

    Tabanca, Nurhayat; Demirci, Betul; Ozek, Temel; Kirimer, Nese; Baser, K Husnu Can; Bedir, Erdal; Khan, Ikhlas A; Wedge, David E

    2006-06-09

    Essential oils from 15 Pimpinella species were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques. One species, Pimpinella anisum, in which only fruits were evaluated, was also included in the study. A total of 140 different compounds were identified and significant qualitative and quantitative differences were observed among the samples. Pimpinella essential oils were characterized as having mono-, sesqui- and trinorsesquiterpenoids, propenylphenols, and pseudoisoeugenols. Trinorsesquiterpenoids and phenylpropanoids appear to be chemical markers of Pimpinella species analyzed thus far. Essential oils obtained from Pimpinella roots share the same principal compound, epoxypseudoisoeugenyl-2-methylbutyrate at concentrations from 20 to 82.6%.

  5. Development and evaluation of a transportable fast gas chromatograph for the monitoring of organic vapors in air

    SciTech Connect

    Gonzalez, J.A.; Levine, S.P.; Berkley, R.E.

    1993-01-01

    Gas chromatography has the potential to be a real-time or near real-time monitoring method for organics in air. A transportable fast GC with FID/ECD and PID/ECD configurations has been developed. Preliminary evaluation has shown that all design features and improvements of the instrument worked successfully.

  6. [The gas chromatographic determination of sulfur- and oxygen-containing organic compounds released into the air of cellulose sulfate works].

    PubMed

    Taranenko, N A; Dorogova, V B

    1992-01-01

    The article presents data on the design of sensitive, selective, useful in group analysis method to detect dimethylsulphide, dimethyldisulphide, acetic, propionic, butyric and valeric acids, methyl alcohol and phenol by means of gas chromatography in the air of cellulose sulphate production working zone. The methods were tested in examining the work conditions in Bratsk found-lavage shops.

  7. Gas chromatographic vapor pressure determination of atmospherically relevant oxidation products of β-caryophyllene and α-pinene

    NASA Astrophysics Data System (ADS)

    Hartonen, Kari; Parshintsev, Jevgeni; Vilja, Vesa-Pekka; Tiala, Heidi; Knuuti, Sinivuokko; Lai, Ching Kwan; Riekkola, Marja-Liisa

    2013-12-01

    Vapor pressures (subcooled liquid, pliquid) of atmospherically relevant oxidation products of β-caryophyllene (β-caryophyllene aldehyde 0.18 ± 0.03 Pa and β-nocaryophyllene aldehyde 0.17 ± 0.03 Pa), and α-pinene (pinonaldehyde 16.8 ± 0.20 Pa, cis-pinic acid 0.12 ± 0.06 Pa, and cis-pinonic acid 0.99 ± 0.19 Pa) at 298 K were obtained by gas chromatography with flame ionization detection (FID) and mass spectrometric (MS) detection. The effects of stationary phase polarity and column film thickness on the vapor pressure values were investigated. Increase in stationary phase polarity provided smaller values, while increase in film thickness gave slightly higher values. Values for vapor pressure were at least two orders of magnitude lower when obtained by a method utilizing vaporization enthalpy (determined by gas chromatography-mass spectrometry) than by retention index method. Finally, the results were compared with values calculated by group contribution theory. For the β-caryophyllene oxidation products, the values measured by gas chromatography were slightly lower than those obtained by theoretical calculations. The opposite trend was observed for the α-pinene oxidation products. The methods based on gas chromatography are concluded to be highly useful for the determination of vapor pressures of semi-volatile compounds. Except for the most polar pinic and pinonic acids, differences between vapor pressure values obtained by GC-FID and GC-MS were small. Since GC-MS provides structural information simultaneously, the use of GC-MS is recommended.

  8. A Versatile, Automatic Chromatographic Column Packing Device

    ERIC Educational Resources Information Center

    Barry, Eugene F.; And Others

    1977-01-01

    Describes an inexpensive apparatus for packing liquid and gas chromatographic columns of high efficiency. Consists of stainless steel support struts, an Automat Getriebmotor, and an associated three-pulley system capable of 10, 30, and 300 rpm. (MLH)

  9. Development of a Low Power Gas Chromatograph-Mass Spectrometer for In-Situ Detection of Organics in Martian Soil

    NASA Technical Reports Server (NTRS)

    Pinnick, Veronica; Buch, Arnaud; VanAmerom, Friso H. W.; Danell, Ryan M.; Brinckerhoff, William; Mahaffy, Paul; Cotter, Robert J.

    2011-01-01

    The Mars Organic Molecule Analyzer (MOMA) is a joint venture by NASA and the European Space Agency (ESA) to develop a sensitive, light-weight, low-power mass spectrometer for chemical analysis on Mars. MOMA is a key analytical instrument aboard the 2018 ExoMars rover mission seeking signs of past or present life. The current prototype was built to demonstrate operation of gas chromatography (OC) and laser desorption (LD) mass spectrometry under martian ambient conditions (5-7 Torr of CO2-rich atmosphere). Recent reports have discussed the MO MA concept, design and performance. Here, we update the current prototype performance, focusing specifically on the GCMS mode.

  10. Evaluation of electron capture gas chromatographic method for determination of methyl mercury in freezer-case seafoods.

    PubMed

    Alvarez, G H; Hight, S C; Capar, S G

    1984-01-01

    A method was recently adopted by AOAC for determination of methyl-bound mercury in canned and fresh-frozen seafood by electron capture gas chromatography. That method was applied to the analysis of commercially prepared freezer-case seafoods. None of the commercially added ingredients produced electron capture responses that interfered in the analysis for methyl mercury. Recoveries of 95.7-114% were obtained in fortification studies of methyl mercury at 0.2 and 1.0 ppm levels. The applicability of aqueous methyl mercuric chloride solution for fortification studies was demonstrated.

  11. Gas chromatographic separation of nitrogen, oxygen, argon, and carbon monoxide using custom-made porous polymers from high purity divinylbenzene

    NASA Technical Reports Server (NTRS)

    Pollock, G. E.; Ohara, D.; Hollis, O. L.

    1984-01-01

    Existing porous polymers were surveyed for their ability to separate the subject gases. Certain products that showed more promise than others were synthesized and the existing synthetic procedures studied and modified to produce new polymers with enhanced ability to separate the subject gases. Evaluation of the porous polymers was carried out practically by gas chromatography at ambient temperature. The modified synthetic procedures were somewhat simpler than the originals. The new porous polymers made with high purity divinylbenzene enabled use of shorter columns to obtain the separations desired.

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

    EPA Science Inventory

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

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

    PubMed

    Larsson, L

    1983-08-01

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

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

    PubMed

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

    2009-02-01

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

  15. Chromatographic fingerprint analysis of metabolites in natural and artificial agarwood using gas chromatography-mass spectrometry combined with chemometric methods.

    PubMed

    Gao, Xiaoxia; Xie, Mingrong; Liu, Shaofeng; Guo, Xiaoling; Chen, Xiaoying; Zhong, Zhaojian; Wang, Lei; Zhang, Weimin

    2014-09-15

    Agarwood is a resinous material formed in wounded Aquilaria sinensis in China, which is widely used as an effective traditional Chinese medicine (TCM). This study is aimed to use gas chromatography-mass spectrometry combined with chemometric methods to create reliable criteria for accurate identification of natural agarwood and artificial agarwood, as well as for quality evaluation of artificial agarwood. Natural agarwood and artificial agarwood (stimulated by formic acid or formic acid plus fungal inoculation) were used as standards and controls for the gas chromatography-mass spectrometry (GC-MS) and multivariate analysis. The identification criteria developed were applied to commercial agarwood. A reliable criteria including correlation coefficient of GC-MS fingerprint of natural agarwood and 22 markers of metabolism in natural and artificial agarwood was constructed. Compared with chemically stimulated agarwood (formic acid) and in terms of the 22 markers, artificial agarwood obtained by formic acid stimulation and fungal inoculation were much closer to natural agarwood. The study demonstrates that the chemical components of artificial agarwood obtained by comprehensive stimulated method (formic acid plus fungal inoculation) are much closer to the natural agarwood than those obtained by chemically stimulated method (formic acid), as times goes by. A reliable criteria containing correlation coefficient of GC-MS fingerprint of natural agarwood and 22 metabolism markers can be used to evaluate the quality of the agarwood. As an application case, three samples were identified as natural agarwood from the 25 commercial agarwood by using the evaluation method.

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

    PubMed

    Kaal, Erwin; de Koning, Sjaak; Brudin, Stella; Janssen, Hans-Gerd

    2008-08-08

    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 automated procedure for thermally assisted hydrolysis and methylation (THM) of biopolymers is described. Drying of the sample, addition of the reagent, incubation and pyrolysis are performed inside the liner of a programmable temperature vaporizer injector. The new system not only allows efficient analysis of large series of samples, but also allows automated optimization of the experimental parameters based on an experimental design approach. The performance of the automated THM-procedure was evaluated by performing THM-GC of a poly(acrylic acid)-poly(maleic anhydride) copolymer (PAA/PMAH) and several polysaccharides. The optimized THM-procedure was applied for the structural characterization and differentiation of several lignins and hydroxypropylmethyl-celluloses. It was also applied to proteins. Here myoglobin and cytochrome c were used as the model compounds. Both conventional GC-mass spectrometry (MS) and comprehensive two-dimensional gas chromatography (GCxGC)-time-of-flight (TOF) MS were used for separation and identification of the species formed. The information obtained can aid in structure elucidation of polar biopolymers as well as in providing detailed compositional information which can be used to differentiate structurally similar biopolymers.

  17. Determination of volatile organic and polycyclic aromatic hydrocarbons in crude oil with efficient gas-chromatographic methods.

    PubMed

    Wang, Haijing; Geppert, Helmut; Fischer, Thomas; Wieprecht, Wolfgang; Möller, Detlev

    2015-01-01

    Determination of volatile organic compounds (VOCs) in crude oil, such as super volatile organic compounds (super VOCs) and simple polycyclic aromatic hydrocarbons (PAHs), is vital for targeting crude oil spill spots. In this study, a static headspace gas chromatography flame ionization detection method was established for determination of super VOCs in crude oil with both external and internal standard determination, which can be used in the field when using portable gas chromatography. Identification was done by comparing the retention time with the corresponding standards and quantitation was done with a new one-drop method. Another simplified and efficient method was performed to analyze volatile PAHs in crude oil, which can also be used in field analysis. Toluene was used as the extraction solvent for PAHs in crude oil. Method validation for both analyses was satisfactory. The result showed that n-butane and n-pentane were maximum super VOCs and naphthalene, phenanthrene and fluorene were the main PAHs in the crude oil studied. The super VOCs quantity ranged from 3 to 6% and the main PAHs consisted of 0.02-0.06% of studied crude oil.

  18. Gas chromatographic method for the determination of residual monomers, 2-(acryloyloxy)ethyl isocyanate and 2-(methacryloyloxy)ethyl isocyanate, as curing agents in an ultraviolet curable adhesive.

    PubMed

    Kim, Byoung-Hyoun; Kim, Nosun; Moon, Dong Cheul

    2014-02-01

    A gas chromatographic method is described for the determination of residual 2-(acryloyloxy)ethyl isocyanate (AOI) and 2-(methacryloyloxy)ethyl isocyanate (MOI) as curing agents in an ultraviolet curable adhesive. Pre-column derivatization was employed in the determination of AOI and MOI as a means of enhancing the response of the flame ionization detector. Urethane derivatives of AOI and MOI were derived using methanol for 30 min at room temperature. The accuracies (n = 5, three concentration levels) were in the range of 113.4 to 126.7%, and precisions (n = 5, three concentration levels) were in the range of 0.8 to 4.3% for AOI-OMe. Furthermore, the accuracies were in the range of 79.5 to 108.6% and the precisions were in the range of 1.0 to 2.4% for MOI-OMe. The correlation coefficients of six calibration standards were all greater than 0.9999 for AOI-OMe and greater than 0.9998 for MOI-OMe over the range from 10 to 100 µg/mL.

  19. A portable gas chromatograph with simultaneous detection by mass spectrometry and electroantennography for the highly sensitive in situ measurement of volatiles.

    PubMed

    Schott, Matthias; Wehrenfennig, Christoph; Gasch, Tina; Düring, Rolf-Alexander; Vilcinskas, Andreas

    2013-09-01

    Mating disruption is a sustainable method for the control of insect pests, involving the release of synthetic sex pheromones that disrupt the olfactory localization of females by males. However, the development and refinement of this strategy is hampered because current instruments lack the sensitivity to detect volatile organic chemicals in the field, and portable electroantennograms produce non-comparable relative units and distorted results in the presence of plant volatiles. To address the demand for more sensitive instruments that are suitable for the rapid in situ detection of airborne pheromones, we have developed a portable, automated needle trap device connected to a gas chromatograph, mass spectrometer, and electroantennographic detector (NTD-GC-MS/EAD) suitable for field applications. We tested the instrument by measuring the concentration of the sex pheromone (E,Z)-7,9-dodecadienyl acetate, which is used to disrupt the mating of the European grapevine moth Lobesia botrana (Lepidoptera: Tortricidae). Our data confirm that the instrument generates highly reproducible results and is highly sensitive, with a detection threshold of 3 ng/m(3) (E,Z)-7,9-dodecadienyl acetate in outside air.

  20. The gas chromatographic determination of volatile fatty acids in wastewater samples: evaluation of experimental biases in direct injection method against thermal desorption method.

    PubMed

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

    2014-04-11

    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.

  1. Development of a solid-phase extraction/gas chromatographic-mass spectrometric method for quantification of succinic acid in nucleoside derivatives for oligonucleotide synthesis.

    PubMed

    Stenholm, Ake; Drevin, Ingrid; Lundgren, Michael

    2005-04-08

    A solid-phase extraction (SPE)/gas chromatographic-mass spectrometric (GC-MS) method was developed for analysing residual succinic acid in nucleoside derivatives to be used in oligonucleotide synthesis. Use of a SPE protocol, enabled most of the derivatives to be trapped, thereby creating eluates enriched in succinic acid. GC-MS was used to quantify the amount of residual succinic acid in four different nucleoside preparations, with succinate concentrations varying from 0.18 to 0.24% (w/w). The within-day repeatability of the method was found to be 1.25% RSD. A linear relationship was observed between the amount of succinic acid in the sample and the GC-MS peak area, with a correlation coefficient of 0.9997 in the concentration interval 0.05-2.5% (w/w). Recoveries were measured by the addition of internal standards to working solutions and varied between 99.8 and 102.6%.

  2. [Analysis of pesticides including chlorine in welsh onions and mushrooms using gas chromatograph with an atomic emission detector (GC-AED)].

    PubMed

    Tateishi, Yukinari; Takano, Ichiro; Kobayashi, Maki; Tamura, Yasuhiro; Tomizawa, Sanae; Sakai, Naoko; Kamijo, Kyoko; Nagayama, Toshihiro; Kamata, Kunihiro

    2004-12-01

    An analytical method for the determination of 32 kinds of pesticide residues in onions, Welsh onions and mushrooms using gas chromatograph with an atomic emission detector (GC-AED) was developed. The pesticides were extracted with acetone-n-hexane (2:3) mixture. The crude extract was partitioned between 5% sodium chloride and ethyl acetate-n-hexane (1:4) mixture. The extract was passed through a Florisil mini-column for cleanup with 10 mL of acetone-n-hexane (1:9) mixture. Although the sensitivity of GC-AED was inferior to that of GC-ECD, GC-AED has a superior element-selectivity. Therefore pesticide residues in foods could be analyzed more exactly by using GC-AED. Thirty-two pesticides including chlorine in onion, Welsh onion and shiitake mushroom were detected without interference. Recoveries of these pesticides from samples determined by GC-AED were 64-114%, except for a few pesticides.

  3. Measurement of Temperature Dependence for Vapor Pressures of Seventeen OH-PBDEs and Eleven MeO-PBDEs by Gas Chromatographic Method.

    PubMed

    Zhao, Hongxia; Xie, Qing; Chen, Xiuying; Qu, Baocheng; Jiang, Jingqiu

    2016-05-01

    Hydroxylated polybromodiphenyl ethers (OH-PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) are emerging organic pollutants. Supercooled liquid vapor pressures (p L) and enthalpies of vaporization (∆vap H) for seventeen OH-PBDEs and eleven MeO-PBDEs were determined by a gas chromatographic technique. p L at 298 K ranged from 0.0173 Pa for 2'-OH-BDE3 to 2.32 × 10(-7) Pa for 3'-OH-BDE154 and they are approximately one order of magnitude smaller than those determined for the counterpart polybrominated diphenyl ethers (PBDEs). ∆vap H was in the range of 76-121 kJ/mol. The temperature dependence of p L was measured by fitting the experimental data with the log(p L/Pa) = a/(T/K) + b equation, and this corresponds to a 50-265 times higher p L value at 0 versus 30°C. Using fundamental quantum chemical descriptors, two quantitative structure-property relationship models (Q cum > 0.935) were developed to estimate p L at any temperature for the additional OH- and MeO-PBDE congeners.

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

    PubMed

    Laakso, Päivi H

    2014-01-01

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

  5. Round-robin evaluation of a solid-phase microextraction-gas chromatographic method for reliable determination of trace level ethylene oxide in sterilized medical devices.

    PubMed

    Harper, Thomas; Cushinotto, Lisa; Blaszko, Nancy; Arinaga, Julie; Davis, Frank; Cummins, Calvin; DiCicco, Michael

    2008-02-01

    Medical devices that are sterilized with ethylene oxide (EtO) retain small quantities of EtO residuals, which may cause negative systemic and local irritating effects, and must be accurately quantified to ensure non-toxicity. The goal of this round-robin study is to investigate the capability of a novel solid-phase microextraction-gas chromatographic (SPME-GC) method for trace-level EtO residuals analysis: three independent laboratories conducted a guided experiment using this SPME-GC method, in assessing method performance, ruggedness and the feasibility of SPME fibers. These were satisfactory across the independent laboratories, at the 0.05-5.00 ppm EtO range. This method was then successfully applied to analyze EtO residuals in several sterilized/aerated medical devices of various polymeric composition, reliably detecting and quantifying the trace levels of EtO residuals present ( approximately 0.05 ppm EtO). SPME is a feasible alternative for quantifying trace-level EtO residuals in sterilized medical devices, thereby lowering the limit of quantification (LOQ) by as much as two to three orders of magnitude over the current GC methodology of direct liquid injection.

  6. 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.

    PubMed

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

    2012-09-21

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

  7. Avoiding hard chromatographic segmentation: A moving window approach for the automated resolution of gas chromatography-mass spectrometry-based metabolomics signals by multivariate methods.

    PubMed

    Domingo-Almenara, Xavier; Perera, Alexandre; Brezmes, Jesus

    2016-11-25

    Gas chromatography-mass spectrometry (GC-MS) produces large and complex datasets characterized by co-eluted compounds and at trace levels, and with a distinct compound ion-redundancy as a result of the high fragmentation by the electron impact ionization. Compounds in GC-MS can be resolved by taking advantage of the multivariate nature of GC-MS data by applying multivariate resolution methods. However, multivariate methods have to be applied in small regions of the chromatogram, and therefore chromatograms are segmented prior to the application of the algorithms. The automation of this segmentation process is a challenging task as it implies separating between informative data and noise from the chromatogram. This study demonstrates the capabilities of independent component analysis-orthogonal signal deconvolution (ICA-OSD) and multivariate curve resolution-alternating least squares (MCR-ALS) with an overlapping moving window implementation to avoid the typical hard chromatographic segmentation. Also, after being resolved, compounds are aligned across samples by an automated alignment algorithm. We evaluated the proposed methods through a quantitative analysis of GC-qTOF MS data from 25 serum samples. The quantitative performance of both moving window ICA-OSD and MCR-ALS-based implementations was compared with the quantification of 33 compounds by the XCMS package. Results shown that most of the R(2) coefficients of determination exhibited a high correlation (R(2)>0.90) in both ICA-OSD and MCR-ALS moving window-based approaches.

  8. Limits of detections for the determination of mono- and dicarboxylic acids using gas and liquid chromatographic methods coupled with mass spectrometry

    PubMed Central

    Št’ávová, Jana; Beránek, Josef; Nelson, Eric P.; Diep, Bonnie A.; Kubátová, Alena

    2011-01-01

    The chromatographic separation and instrumental limits of detection (LODs) were obtained for a broad range of C1-C18 monocarboxylic (MCAs) and C2-C14 dicarboxylic acids (DCAs) employing either chemical derivatization followed by gas chromatography-mass spectrometry and flame ionization detection (GC-MS/FID) or direct analysis with liquid chromatography high resolution MS and tandem MS (LC-MS). Suitability, efficiency and stability of reaction products for several derivatization agents used for esterification (BF3/butanol), and trimethysilylation, including trimethylsilyl-N-N-dimethylcarbamate (TMSDMC) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) were evaluated. The lowest limits of detection for the majority of compounds below 10 pg (with the exception of acetic acid) were obtained for derivatization with BF3/butanol followed by GC-MS in the total ion current (TIC) mode. Further improvements were achieved when applying either selected ion monitoring (SIM), which decreased the LODs to 1–4 pg or a combination of SIM and TIC (SITI) (2–5 pg). GC-FID provided LODs comparable to those obtained by GC-MS TIC. Both trimethylsilylation (followed by GC-MS) and direct LC-MS/MS analysis yielded LODs of 5– 40 pg for most of the acids. For volatile acids the LODs were higher, e.g., 25 and 590 ng for TMSDMC and BSTFA derivatized formic acid, respectively whereas the LC-MS methods did not allow for the analysis of formic acid at all. PMID:21185238

  9. Gas chromatographic/nitrogen-phosphorus detection method for determination of ethylene thiourea in finished drinking waters: collaborative study.

    PubMed

    Longbottom, J E; Edgell, K W; Erb, E J; Lopez-Avila, V

    1993-01-01

    A joint U.S. Environmental Protection Agency (USEPA)-AOAC interlaboratory method validation study was conducted on USEPA National Pesticide Survey (NPS) Method 6, "Determination of Ethylene Thiourea (ETU) in Finished Drinking Water by Gas Chromatography with a Nitrogen-Phosphorus Detector." The purpose of the study was to determine and compare the mean recoveries and precision for determination of ETU in reagent water and finished drinking waters. The study design was based on Youden's nonreplicate plan for collaborative tests of analytical methods. The waters were spiked with ETU at 6 concentrations levels, prepared as 3 Youden pairs. In the method, the test water is extracted by passing the sample through an absorbent matrix type tube. ETU is recovered from the tube with methylene chloride, the extract is solvent-exchanged to ethyl acetate, and an aliquot of each extract is analyzed by gas chromatography using a nitrogen-phosphorus detector. Twelve laboratories participated in the study. Data were analyzed using a USEPA computer program, which measured recovery and precision for ETU and compared the performance of the method between the 2 water types. Over the concentration range tested, the mean percent recoveries of ETU were 82-92% in reagent water and 85-98% in finished drinking water. The range of the between-laboratory relative standard deviations (RSDR) for the 6 concentrations was 5-24% in reagent water, but was only 4-9% in finished drinking water. The range of the within-laboratory relative standard deviations (RSDr) was 6-14% for reagent water and 6-10% for finished drinking water. Results for the 2 water matrixes showed no statistically significant differences.(ABSTRACT TRUNCATED AT 250 WORDS)

  10. Fabrication of zeolitic imidazolate framework-8-methacrylate monolith composite capillary columns for fast gas chromatographic separation of small molecules.

    PubMed

    Yusuf, Kareem; Badjah-Hadj-Ahmed, Ahmed Yacine; Aqel, Ahmad; ALOthman, Zeid Abdullah

    2015-08-07

    A composite zeolitic imidazolate framework-8 (ZIF-8) with a butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5cm long×250μm i.d.) was fabricated to enhance the separation efficiency of methacrylate monoliths toward small molecules using conventional low-pressure gas chromatography in comparison with a neat butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5cm long×250μm i.d.). The addition of 10mgmL(-1) ZIF-8 micro-particles increased the BET surface area of BuMA-co-EDMA by 3.4-fold. A fast separation of five linear alkanes in 36s with high resolution (Rs≥1.3) was performed using temperature program. Isothermal separation of the same sample also showed a high efficiency (3315platesm(-1) for octane) at 0.89min. Moreover, the column was able to separate skeletal isomers, such as iso-octane/octane and 2-methyl octane/nonane. In addition, an iso-butane/iso-butylene gas mixture was separated at ambient temperature. Comparison with an open tubular TR-5MS column (30m long×250μm i.d.) revealed the superiority of the composite column in separating the five-membered linear alkane mixture with 4-5 times increase in efficiency and a total separation time of 0.89min instead of 4.67min. A paint thinner sample was fully separated using the composite column in 2.43min with a good resolution (Rs≥0.89). The perfect combination between the polymeric monolith, with its high permeability, and ZIF-8, with its high surface area and flexible 0.34nm pore openings, led to the fast separation of small molecules with high efficiency and opened a new horizon in GC applications.

  11. Gas-liquid chromatographic and gas-liquid-mass spectometric determination of fenvalerate and permethrin residues in grasshoppers and duck tissue samples

    USGS Publications Warehouse

    Reichel, W.L.; Kolbe, E.J.; Stafford, C.J.

    1981-01-01

    A procedure is described for determining fenvalerate and permethrin residues in grasshoppers and duck tissues. Samples are Soxhlet-extracted with hexane and cleaned up by gel permeation chromatography with an in-line alumina column. Samples are analyzed by gas-liquid chromatography with electron capture detection, and confirmed by gas-liquid chromatography-mass spectrometry. The average recovery from fortified tissues was 97%.

  12. Gas chromatographic measurements of activity coefficients at infinite dilution for refrigerants with a polyol ester oil as a stationary phase

    SciTech Connect

    Stryjek, R.; Bobbo, S.; Camporese, R.; Zilio, C.

    1999-05-01

    Activity coefficients at infinite dilution have been measured by gas chromatography for 14 refrigerants (R12, R22, R32, R124, R125, R134a, R142b, R143a, RE170, R236ea, R290, R600, R600a, and R236fa) as solutes, using a polyol ester oil (POE), EMKARATE by ICI, as a stationary phase (solvent). Instrumental analysis (NMR, IR) showed that the main components of the oil are pentaerithritol esters of carboxylic acids, and electrospray ionization spectrometry revealed an average molecular mass of the POE of 618 g/mol. The measurements were performed within a temperature range of 244 K to 313 K, but a specific temperature range for each refrigerant was adopted depending on its retention data. The experimental findings are well-represented by the equation: ln {gamma}{sub i}{sup {infinity}} = a{sub i} {minus} b{sub i}/T. Some refrigerants, i.e., R22, R124, R125, R236ea, and R236fa, show quite a considerable positive temperature dependence of their activity coefficients at infinite dilution, which can be attributed to hydrogen bonding with the POE, unlike other refrigerants that show a small, either positive or negative temperature dependence. To the authors` knowledge, there are no data in the literature on activity coefficients at infinite dilution for refrigerant and oil (lubricant) systems, and details on the solubility of refrigerants in oils are also extremely scarce.

  13. Determination of hexanal in rice using an automated dynamic headspace sampler coupled to a gas chromatograph-mass spectrometer.

    PubMed

    Wang, Yiru; Ha, Jaeho

    2013-01-01

    The aim of this study was to establish a method for the determination of hexanal as a lipid oxidation marker in rice. For the sample preparation, ground rice exhibited better sensitivity and reproducibility for the analysis of hexanal than whole rice. A total flow of purge gas of 300 mL at 20 mL/min of purge was sufficient to obtain the necessary sensitivity for the analysis of hexanal in rice. The total time for sample preparation and analysis for individual samples was approximately 15 min. A low incubation temperature of 30°C was chosen, not only to reduce the effect of water, but also to avoid excess lipid oxidation and loss of hexanal during the analysis. The limits of detection and quantification were 3.7 and 5.1 ng/g, respectively. Good linearity was obtained in the range from 5.1-500.0 ng/g. The recoveries of hexanal in rice were greater than 97.0 and 107.0% at the spiked levels of 5 and 50 ng/g, respectively, with relative standard deviations of 3.3 and 6.1%, respectively.

  14. Antioxidant Activity and Gas Chromatographic-Mass Spectrometric Analysis of Extracts of the Marine Algae, Caulerpa peltata and Padina Gymnospora

    PubMed Central

    Murugan, Kavitha; Iyer, Vidhya V.

    2014-01-01

    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. PMID:25593390

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

    USGS Publications Warehouse

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

    2002-01-01

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

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

    PubMed

    Darko, Ernest; Thurbide, Kevin B

    2016-09-23

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

  17. Gas chromatographic-mass spectrometric fragmentation study of phytoestrogens as their trimethylsilyl derivatives: Identification in soy milk and wastewater samples

    USGS Publications Warehouse

    Ferrer, I.; Barber, L.B.; Thurman, E.M.

    2009-01-01

    An analytical method for the identification of eight plant phytoestrogens (biochanin A, coumestrol, daidzein, equol, formononetin, glycitein, genistein and prunetin) in soy products and wastewater samples was developed using gas chromatography coupled with ion trap mass spectrometry (GC/MS-MS). The phytoestrogens were derivatized as their trimethylsilyl ethers with trimethylchlorosilane (TMCS) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). The phytoestrogens were isolated from all samples with liquid-liquid extraction using ethyl acetate. Daidzein-d4 and genistein-d4 labeled standards were used as internal standards before extraction and derivatization. The fragmentation patterns of the phytoestrogens were investigated by isolating and fragmenting the precursor ions in the ion-trap and a typical fragmentation involved the loss of a methyl and a carbonyl group. Two characteristic fragment ions for each analyte were chosen for identification and confirmation. The developed methodology was applied to the identification and confirmation of phytoestrogens in soy milk, in wastewater effluent from a soy-milk processing plant, and in wastewater (influent and effluent) from a treatment plant. Detected concentrations of genistein ranged from 50,000 ??g/L and 2000 ??g/L in soy milk and in wastewater from a soy-plant, respectively, to 20 ??g/L and <1 ??g/L for influent and effluent from a wastewater treatment plant, respectively. ?? 2009 Elsevier B.V.

  18. Gas chromatographic-mass spectrometric characterisation of amiton and the recovery of amiton from concrete, paint, rubber and soil matrices.

    PubMed

    Borrett, Veronica T; Gan, Tiang-Hong; Lakeland, Barry R; Leslie, D Ralph; Mathews, Robert J; Mattsson, Eric R; Riddell, Stuart; Tantaro, Vince

    2003-06-27

    Amiton [O,O-diethyl S-[2-(diethylamino)ethyl] phosphorothiolate], is an organophosphorus chemical included in Schedule 2 of the Chemical Weapons Convention (CWC). Verification provisions under the CWC rely on the existence of a database of analytical information for scheduled chemicals and related compounds. Little analytical information is available for amiton. In this study, gas chromatography-mass spectrometry (GC-MS) characterisation of amiton and its typical impurities (including by-products and degradation products), supported by selective GC detection and 31P NMR data, was undertaken. Twenty-one compounds, including a by-product unique to amiton from an industrial source, were identified. Involatile degradation products of amiton were derivatised to enable their identification by GC-MS. The recovery of amiton from matrices that may be expected in an inspection scenario (i.e. concrete, paint, rubber and soil) was also examined. Paint and concrete matrices were the most useful matrices for the detection of amiton, and its by-products and degradation products. Amiton was readily detected in these matrices after 28 days.

  19. A gas chromatographic/mass spectrometric method for tracing the microbial conversion of glucose into amino sugars in soil.

    PubMed

    He, Hongbo; Xie, Hongtu; Zhang, Xudong; Wang, Yanhong; Wu, Yeye

    2005-01-01

    Amino sugars in soils are heterogeneous and have been used as microbial residue biomarkers to investigate the microbial contribution to soil organic matter. However, it is not clear what the available carbon source is and how glucose is utilized for the synthesis of soil amino sugars. This paper presents a new gas chromatography/mass spectrometry (GC/MS) approach for the identification of 13C incorporation into three amino sugars, D-glucosamine, D-galactosamine, and muramic acid, in soil incubated with U-13C-glucose. Method evaluation showed that the chemical ionization (CI) mode was suitable for all these amino sugars, but that electron impact (EI) mode was applicable only to glucosamine and galactosamine. The 13C conversion rate was estimated based on the abundance ratio of the ions corresponding to the masses of the ions F+n and F (where n is the skeleton carbon number in the fragment ions F of the amino sugars) and calculated as atom percentage excess. The reproducibility of the method was excellent and clearly adequate for the present purpose. In addition, the new approach is highly accurate as tested with mixtures of U-13C-glucose and natural glucose.

  20. Study of the Behaviors of Gunshot Residues from Spent Cartridges by Headspace Solid-Phase Microextraction-Gas Chromatographic Techniques.

    PubMed

    Chang, Kah Haw; Yew, Chong Hooi; Abdullah, Ahmad Fahmi Lim

    2015-07-01

    Gunshot residues, produced after shooting activity, have acquired their importance in analysis due to the notoriety of firearms-related crimes. In this study, solid-phase microextraction was performed to extract the headspace composition of spent cartridges using 85-μm polyacrylate fiber at 66°C for 21 min. Organic compounds, that is, naphthalene, 2,6-dinitrotoluene, 2,4-dinitrotoluene, diphenylamine, and dibutyl phthalate were detected and analyzed by gas chromatography-flame ionization detection technique. Evaluation of chromatograms for diphenylamine, dibutyl phthalate, and naphthalene indicates the period after a gunshot was discharged, whether it was 1 days, 2-4 days, <5 days, 10 days, 20 days, or more than 30 days ago. This study revealed the potential effects of environmental factors such as occasional wind blow and direct sunlight on the estimation of time after spent cartridges were discharged. In conclusion, we proposed reliable alternative in analyzing the headspace composition of spent cartridges in a simulated crime scene.

  1. Solid-phase extraction and gas chromatographic- mass spectrometric determination of the veterinary drug xylazine in human blood.

    PubMed

    Barroso, M; Gallardo, E; Margalho, C; Devesa, N; Pimentel, J; Vieira, D N

    2007-04-01

    This paper presents a method for the determination of xylazine in whole blood using solid-phase extraction and gas chromatography-mass spectrometry. This technique required only 0.5 mL of sample, and protriptyline was used as internal standard (IS). Limits of detection and quantitation (LOQ) were 2 and 10 ng/mL, respectively. The method was found to be linear between the LOQ and 3.50 microg/mL, with correlation coefficients higher than 0.9922. Precision (intra- and interday) and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The analyte was stable in the matrix for at least 18 h at room temperature and for at least three freeze/thaw cycles. Mean recovery, calculated at three concentration levels, was 87%. To the best of our knowledge, this is the first time that solid-phase extraction is used as sample preparation technique for the determination of this compound in biological media. Because of its simplicity and speed when compared to other extraction techniques, the herein described method can be successfully applied in the diagnosis of intoxications by xylazine.

  2. Validation of atmospheric VOC measurements by proton-transfer-reaction mass spectrometry using a gas-chromatographic preseparation method.

    PubMed

    Warneke, Carsten; De Gouw, Joost A; Kuster, William C; Goldan, Paul D; Fall, Ray

    2003-06-01

    Proton-transfer-reaction mass spectrometry (PTR-MS) has emerged as a useful tool to study volatile organic compounds (VOCs) in the atmosphere. In PTR-MS, proton-transfer reactions with H30+ ions are used to ionize and measure VOCs in air with a high sensitivity and fast time response. Only the masses of the ionized VOCs and their fragments, if any, are determined, and these product ions are not unique indicators of VOC identities. Here, a combination of gas chromatography and PTR-MS (GC-PTR-MS) is used to validate the measurements by PTR-MS of a number of common atmospheric VOCs. We have analyzed 75 VOCs contained in standard mixtures by GC-PTR-MS, which allowed detected masses to be unambiguously related to a specific compound. The calibration factors for PTR-MS and GC-PTR-MS were compared and showed that the loss of VOCs in the sample acquisition and GC system is small. GC-PTR-MS analyses of 56 air samples from an urban site were used to address the specificity of PTR-MS in complex air masses. It is demonstrated that the ions associated with methanol, acetonitrile, acetaldehyde, acetone, benzene, toluene, and higher aromatic VOCs are free from significant interference. A quantitative intercomparison between PTR-MS and GC-PTR-MS measurements of the aforementioned VOCs was performed and shows that they are accurately measured by PTR-MS.

  3. Mass spectrometric identification and gas-liquid chromatographic determination of 2-chloroethyl esters of fatty acids in spices and foods.

    PubMed

    Heikes, D L; Griffitt, K R

    1979-07-01

    The 2-chloroethyl esters of 5 fatty acids have been identified in spice and food samples by gas-liquid chromatography-mass spectrometry (GLC/MS). Twenty-four spice samples were analyzed for the 2-chloroethyl esters of fatty acids by AOAC official multiple residues pesticide procedure using GLC with microcoulometric detection. The esters of capric, lauric, myristic, palmitic, and linoleic acids have been identified at levels up to 1400 ppm. 2-Chloroethyl linoleate was the most abundant ester in all samples. Several foods analyzed by the same procedures showed levels of 2-chloroethyl linoleate as high as 35 ppm. Recoveries from fortified samples ranged from 84 to 98% for the various esters. A method using an acid-catalyzed esterification reaction was developed to rapidly determine the fatty acid content of these spices. GLC analysis with microcoulometric detection was used. Recoveries from fortified samples ranged from 92 to 110%. After 2 spice samples found to be free of 2-chloroethyl esters were fumigated with ethylene oxide, the level of 2-chloroethyl linoleate reached 77 ppm. All levels of 2-chloroethyl esters were confirmed by GLC/MS.

  4. Target urinary analytes for the gas chromatographic- mass spectrometric detection of procyclidine and benzhexol in drug abuse cases.

    PubMed

    El-Haj, Babiker; Al-Amri, Abdulkader; Ali, Heyam Saad

    2011-03-01

    The two antiparkinsonian drugs procyclidine and benzhexol are presently finding considerable favor for their euphoric hallucinogenic effects among drug abusers in some countries. In anticipation of their possible scheduling in national drug laws, gas chromatography-mass spectrometry (GC-MS) methods for their detection in urine will be required. However, because of uncertainty of the metabolic fate of the two drugs in humans, the urinary target analytes for GC-MS detection were not well defined. The problem was addressed in the present study in which it was found that mono-hydroxy metabolites, where hydroxylation took place at the cyclohexane ring in both drugs, could be endorsed as the major target analytes. The metabolites could only be detected as the mono- and/or di-trimethylsilyl (TMS) derivatives. The predominance of either derivative depended on the temperature and time of heating with the derivatizing reagent. Because of the basic properties of the hydroxy metabolites, analytic method optimization was needed for their detection in urine included extraction under basic pH conditions. Urine hydrolysis with β-glucuronidase did not have an effect on the recovery of the metabolites, but was usually performed in search for other drugs. Because of the relative abundance of ions, the electron impact mass spectra of the mono-TMS derivatives and the chemical ionization (CI) mass spectra of the mono- and di-TMS derivatives of the hydroxy metabolites of both drugs were found to be more structurally informative. The CI mass spectra of the di- TMS derivatives have the additive advantage of being potentially useful for quantitative analysis.

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

    PubMed

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

    2006-05-03

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

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

    SciTech Connect

    Goldstein, A. H.; Yee, L. D.; Issacman-VanWertz, G.; Wernis, R. A.

    2016-03-01

    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

  7. Method for measuring changes in the atmospheric O2/N2 ratio by a gas chromatograph equipped with a thermal conductivity detector

    NASA Astrophysics Data System (ADS)

    Tohjima, Yasunori

    2000-06-01

    We present a method for measuring changes in the atmospheric O2/N2 ratio based on data from a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD). In this method, O2 and N2 in an air sample are separated on a column filled with molecular sieve 5A with H2 carrier gas. Since the separated O2 includes Ar, which has a retention time similar to that of O2, the (O2+Ar)/N2 ratio is actually measured. The change in the measured (O2+Ar)/N2 ratio can be easily converted to that in the O2/N2 ratio with a very small error based on the fact that the atmospheric Ar/N2 ratio is almost constant. The improvements to achieve the high-precision measurement include stabilization of the pressure at the GC column head and at the outlets of the TCD and the sample loop. Additionally, the precision is improved statistically by repeating alternate analyses of sample and a reference gas. The standard deviation of the replicate cycles of reference and sample analyses is about 18 per meg (corresponding to 3.8 parts per million (ppm) O2 in air). This means that the standard error is about 7 per meg (1.5 ppm O2 in air) for seven cycles of alternate analyses, which takes about 70 min. The response of this method is likely to have a 2% nonlinearity. Ambient air samples are collected under pressure in glass flasks equipped with two stopcocks sealed by Viton O-rings at both ends. Pressure depletion in the flask during the O2/N2 measurement does not cause any detectable change in the O2/N2 ratio, but the O2/N2 ratio in the flask was found to gradually decrease during the storage period. We also present preliminary results from air samples collected at Hateruma Island (latitude 24°03'N, longitude 123°49') from July 1997 through March 1999. The observed O2/N2 ratios clearly show a seasonal variation, increasing in spring and summer and decreasing in autumn and winter.

  8. 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

    PubMed Central

    Lee, Sang Mi; Shin, Gil-Ok; Park, Kyung Min; Chang, Pahn-Shick; Kim, Young-Suk

    2013-01-01

    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. PMID:23447013

  9. Gas chromatographic, mass spectrometric and stable carbon isotopic investigations of organic residues of plant oils and animal fats employed as illuminants in archaeological lamps from Egypt.

    PubMed

    Copley, M S; Bland, H A; Rose, P; Horton, M; Evershed, R P

    2005-06-01

    Man's use of illuminants in lamps or as torches to extend the working day and range of environments accessible to him would have been a major technological advance in human civilisation. The most obvious evidence for this in the archaeological record comes from pottery and stone vessels showing sooting due to the use of a wick in conjunction with a lipid-based fuel or illuminant. A wide range of potential fuels would have been exploited depending upon availability and burning requirements. Reported herein are the results of chemical investigations of a number of lamps recovered from excavations of the site of Qasr Ibrim, Egypt. Gas chromatographic, mass spectrometric and stable carbon isotopic analyses of both free (solvent extractable) and 'bound'(released from solvent extracted pottery by base treatment) lipids have revealed a wide range of saturated fatty acids, hydroxy fatty acids and alpha, omega-dicarboxylic acids. Examination of the distributions of compounds and comparisons with the fatty acid compositions of modern plant oils have allowed a range of fats and oils to be recognised. Specific illuminants identified include Brassicaceae (Cruciferae) seed oil (most likely radish oil, Raphanus sativus), castor oil (from Ricinus communis), animal fat, with less diagnostic distributions and delta(13)C values being consistent with low stearic acid plant oils, such as linseed (Linum usitatissimum) or sesame (Sesamum indicum) oils. The identifications of the various oils and fats are supported by parallel investigations of illuminant residues produced by burning various oils in replica pottery lamps. The findings are entirely consistent with the classical writers including Strabo, Pliny and Theophrastrus.

  10. Application of microwave-assisted desorption/headspace solid-phase microextraction as pretreatment step in the gas chromatographic determination of 1-naphthylamine in silica gel adsorbent.

    PubMed

    Yan, Cheing-Tong; Jen, Jen-Fon; Shih, Tung-Sheng

    2007-03-30

    Pretreatment of silica gel sample containing 1-naphthylamine by microwave-assisted desorption (MAD) coupled to in situ headspace solid phase microextraction (HS-SPME) has been investigated as a possible alternative to conventional methods prior to gas chromatographic (GC) analysis. The 1-naphthylamine desorbs from silica gel to headspace under microwave irradiation, and directly absorbs onto a SPME fiber located in a controlled-temperature headspace area. After being collected on the SPME fiber, and desorbed in the GC injection port, 1-naphthylamine is analyzed by GC-FID. Parameters that influence the extraction efficiency of the MAD/HS-SPME, such as the extraction media and its pH, the microwave irradiation power and irradiation time as well as desorption conditions of the GC injector, have been investigated. Experimental results indicate that the extraction of a 150mg silica gel sample by using 0.8ml of 1.0M NaOH solution and a PDMS/DVB fiber under high-powered irradiation (477W) for 5min maximizes the extraction efficiency. Desorption of 1-naphthylamine from the SPME fiber in GC injector is optimal at 250 degrees C held for 3min. The detection limit of method is 8.30ng. The detected quantity of 1-naphthylamine obtained by the proposed method is 33.3 times of that obtained by the conventional solvent extraction method for the silica gel sample containing 100ng of 1-naphthylamine. It provides a simple, fast, sensitive and organic-solvent-free pretreatment procedure prior to the analysis of 1-naphthylamine collected on a silica gel adsorbent.

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

    PubMed

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

    2012-06-05

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

  12. Performance characteristics of an automated gas chromatograph-ion trap mass spectrometer system used for the 1995 Southern Oxidants Study field investigation in Nashville, Tennessee

    NASA Astrophysics Data System (ADS)

    Daughtrey, E. Hunter; Adams, Jeffrey R.; Oliver, Karen D.; Kronmiller, Keith G.; McClenny, William A.

    1998-09-01

    A trailer-deployed automated gas chromatograph-mass spectrometer (autoGC-MS) system capable of making continuous hourly measurements was used to determine volatile organic compounds (VOCs) in ambient air at New Hendersonville, Tennessee, and Research Triangle Park, North Carolina, in 1995. The system configuration, including the autoGC-MS, trailer and transfer line, siting, and sampling plan and schedule, is described. The autoGC-MS system employs a pair of matched sorbent traps to allow simultaneous sampling and desorption. Desorption is followed by Stirling engine cryofocusing and subsequent GC separation and mass spectral identification and quantification. Quality control measurements described include evaluating precision and accuracy of replicate analyses of independently supplied audit and round-robin canisters and determining the completeness of the data sets taken in Tennessee. Data quality objectives for precision (±10%) and accuracy (±20%) of 10- to 20-ppbv audit canisters and a completeness of >75% data capture were met. Quality assurance measures used in reviewing the data set include retention time stability, calibration checks, frequency distribution checks, and checks of the mass spectra. Special procedures and tests were used to minimize sorbent trap artifacts, to verify the quality of a standard prepared in our laboratory, and to prove the integrity of the insulated, heated transfer line. A rigorous determination of total system blank concentration levels using humidified scientific air spiked with ozone allowed estimation of method detection limits, ranging from 0.01 to 1.0 ppb C, for most of the 100 target compounds, which were a composite list of the target compounds for the Photochemical Assessment Monitoring Station network, those for Environmental Protection Agency method TO-14, and selected oxygenated VOCs.

  13. 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.

    PubMed

    Lee, Sang Mi; Shin, Gil-Ok; Park, Kyung Min; Chang, Pahn-Shick; Kim, Young-Suk

    2013-02-27

    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.

  14. Comparing different gas chromatographic methods for the quantification of bisphenol A (BPA) trace levels in paper and cardboard products from the market.

    PubMed

    Jurek, A; Leitner, E

    2015-01-01

    Bisphenol A (BPA; 4,4'-(propane-2,2-diyl)diphenol), a suspected endocrine disruptor with weak estrogenic activity, is used in a variety of consumer products, including paper and cardboard products used as food contact materials. The present study compared four different gas chromatographic methods for the analysis of BPA in paper and cardboard food packages. Eighteen different food packages were extracted and BPA was determined using two different derivatisation reactions--trimethylsilylation with N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) and halide alkylation with pentafluorobenzoyl chloride (PFBOCl)--and four different separation and detection techniques. The BSTFA derivatives were quantified with (1) GC-MS in single-ion monitoring (SIM) mode with electron ionisation (EI-GC-MS) and (2) GC-MS/MS in multiple reaction monitoring (MRM) mode using electron ionisation (EI-GC-MS/MS); while the PFBOCl derivatives were quantified with (3) GC-MS using electron ionisation (EI-GC-MS) as well as (4) GC-MS with negative chemical ionisation (NCI-GC-MS). All developed methods showed good linearity (R(2) > 0.9938), precision (CV < 4.5% for reproducibility; CV < 2.2% for repeatability) and sensitivity, with limits of detection (LODs) between 0.02 µg kg(-1) for the pentafluorobenzoyl derivatives measured with the NCI-GC-MS method and 6 µg kg(-1) for the pentafluorobenzoyl derivatives determined with EI-GC-MS. Levels of BPA in the samples were in agreement for all methods, ranging from values below the limit of quantitation (LOQ) to 11.9 mg kg(-1) paper. In a last step, the maximum potential migration into food products was calculated for all tested paper and cardboard samples, assuming a 'worst case' scenario of 100% migration.

  15. A capillary gas chromatographic assay with nitrogen phosphorus detection for the quantification of topiramate in human plasma, urine and whole blood.

    PubMed

    Riffitts, J M; Gisclon, L G; Stubbs, R J; Palmer, M E

    1999-03-01

    An accurate and robust method involving liquid liquid extraction and capillary gas chromatographic (GC) assay with nitrogen phosphorus detection (NPD) was developed and validated for the quantitative determination of topiramate [2,3:4,5-bis-O-(-1-methylethylidene)-beta-D-fructopyranose sulfamate], Topamax, an anticonvulsant drug, in human plasma, urine, and whole blood. The galactopyranose analog of topiramate was used as the internal standard. A DB-5, fused silica capillary column (J&W Scientific, Folsom, CA) was used, yielding typical retention times of 4.95 min for topiramate and 5.32 min for the internal standard in human plasma. The assay involved organic extraction with methyl t-butyl ether (MTBE) from base, a back extraction into acid and a second extraction in MTBE. The organic solvent was evaporated, and the residue was redissolved and injected for analysis. The standard curve was validated from 0.5 to 50 microg/ml(-1) for human plasma and whole blood, and from 1.0 to 50 microg/ml(-1) for urine. Peak area ratios of drug to internal standard were determined and used to construct a standard curve. The resulting chromatograms showed no endogenous interfering peaks with the respective blank human fluids. Chromatograms corresponding to topiramate and the internal standard produced sharp peaks that were well resolved. This assay showed precision and accuracy of < or = 5%. Two minor human metabolites of topiramate did not interfere with the assay. This assay was successfully applied to determine the pharmacokinetics of topiramate during the development of this drug.

  16. 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.

    PubMed

    Jalbert, J; Gilbert, R; Tétreault, P

    1999-08-01

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

  17. Acquisition of a Gas Chromatograph/Mass Spectrometer System for Laboratory Study of Prebiotic Organic Geochemical Processes on the Early Earth, Mars, and Meteorites

    NASA Technical Reports Server (NTRS)

    McCollom, Thomas

    2004-01-01

    This was a major equipment grant that provided funds ($72K) for purchase of a benchtop gas chromatograph-mass spectrometer (GC-MS) for use in experimental studies of prebiotic organic compounds. An Agilent model 689015973 GC-MS was purchased and installed in the PI's lab in August of 2003. The instrument is now being used for a variety of research projects. The primary use of the instrument is to analyze and quantify organic products of laboratory experiments conducted by the PI. One example is shown, which shows organic products (predominantly n-alkanes) formed during Fischer-Tropsch-type abiotic synthesis under hydrothermal conditions. The analytical capabilities of the GC- MS allowed identification of the numerous organic products of this as well as other laboratory experiments. A key use of the instrument in this research is that the mass spectrometer capabilities allow use of isotopically labeled reactants to trace the progress of reactions and evaluate background contaminants. collaborative projects with other scientists involved in exobiology & astrobiology research (e.g., Mitch Schulte, NASA Ames; Katrina Edwards, Woods Hole Oceanographic Institution). For instance, an analysis of membrane lipids of an lithoautotrophic iron-oxidizing bacteria being grown on basalt as a source of metabolic energy, a project where the instrument is being used to evaluate possible biomarker compounds from these organisms is shown. These iron oxidizers are thought to be similar to those living within the ocean crust, and are being investigated as possible analog organisms to those on the early Earth or crust of Mars. The instrument has also been used by an outside investigator (graduate student Brandon Canfeld, Arizona State University) for identification and isotopic characterization of experimental products of abiotic organic synthesis experiments he is conducting with Dr. John Holloway. analysis of quality control samples for other NASA-funded projects. For instance, an

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

    PubMed

    Saliu, F; Anzano, M; Franzetti, A

    2015-03-01

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

  19. Liquid chromatographic extraction medium

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1994-09-13

    A method and apparatus are disclosed for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column. 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. 1 fig.

  20. Liquid chromatographic extraction medium

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1994-01-01

    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.

  1. A gas chromatographic-positive ion chemical ionization-mass spectrometric method for the determination of I-alpha-acetylmethadol (LAAM), norLAAM, and dinorLAAM in plasma, urine, and tissue.

    PubMed

    Moody, D E; Crouch, D J; Sakashita, C O; Alburges, M E; Minear, K; Schulthies, J E; Foltz, R L

    1995-10-01

    l-alpha-Acetylmethadol (LAAM) is approved as a substitute for methadone for the treatment of opiate addiction. Analytical methods are needed to quantitate LAAM and its two psychoactive metabolites, norLAAM and dinorLAAM, to support pharmacokinetic and other studies. We developed a gas chromatographic-positive ion chemical ionization-mass spectrometric method for these analyses. The method uses 0.5 mL urine or 1.0 mL plasma or tissue homogenate, deuterated (d3) isotopomers as internal standards, methanolic denaturation of protein (for plasma and tissue), and extraction of the buffered sample with n-butyl chloride. For tissue homogenates, an acidic back extraction is included. norLAAM and dinorLAAM were derivatized with trifluoroacetic anhydride. Chromatographic separation of LAAM and derivatized norLAAM and dinorLAAM is achieved with a 5% phenyl methylsilicone capillary column. Positive ion chemical ionization detection using methane-ammonia as the reagent gas produces abundant protonated ions (MH+) for LAAM (m/z 354) and LAAM-d3 (m/z 357) and ammonia adduct ions (MNH4+) for the derivatized norLAAM (m/z 453), norLAAM-d3 (m/z 45 6), dinorLAAM (m/z 439), and dinorLAAM-d3 (m/z 442). The linear range of the calibration curves were matrix dependent: 5-300 ng/mL for plasma, 10-1000 ng/mL for urine, and 10-600 ng/g for tissue homogenates. The low calibrator was the validated limit of quantitation for that matrix. The method is precise and accurate with percent coefficients of variation and percent of targets within 13%. The method was applied to the analysis of human urine and plasma samples; rat plasma, liver, and brain samples; and human liver microsomes following incubation with LAAM.

  2. Gas Chromatographic-Mass Spectrometric Analysis of Volatiles Obtained by Four Different Techniques from Salvia rosifolia Sm. and Evaluation for Biological Activity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Volatile constituents from the aerial parts of Salvia rosifolia Sm. (Lamiaceae), endemic to Turkey, were obtained by four different isolation techniques and then analyzed by gas chromatography (GC/FID) and gas chromatography – mass spectrometry (GC/MS) methods. Also in scope of the present work, the...

  3. Chromatographic hydrogen isotope separation

    DOEpatents

    Aldridge, Frederick T.

    1981-01-01

    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 colum. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale mutli-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  4. Chromatographic hydrogen isotope separation

    DOEpatents

    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.

  5. Chromatographic methods in the study of autism.

    PubMed

    Żurawicz, Ewa; Kałużna-Czaplińska, Joanna; Rynkowski, Jacek

    2013-10-01

    Research into biomarkers of autism is a new means of medical intervention in this disease. Chromatographic techniques, especially coupled with mass spectrometry, are widely used in determination of biomarkers and assessment of effectiveness of autism therapy owing to their sensitivity and selectivity. Among the chromatographic techniques gas chromatography and liquid chromatography, especially high-performance liquid chromatography, have found application in clinical trials. The high-performance liquid chromatography technique allows an analysis of liquid samples with a wide range of molecules, small and large, providing an opportunity to perform advanced assays within a short time frame. Gas chromatography with the appropriate preparation of samples (gaseous and liquid) and a selection of analysis conditions enables the separation of thermally stable, volatile and non-volatile organic substances in short runtimes. The chromatographic techniques that are currently used in metabolic studies in autism are designed to identify abnormalities in three areas: the metabolism of neurotransmitters, nutritional and metabolic status and manifestations of oxidative stress. This review presents a necessary theoretical introduction and examples of applications of chromatographic studies of disorder markers in autism.

  6. Trans fat labeling and levels in U.S. foods: assessment of gas chromatographic and infrared spectroscopic techniques for regulatory compliance.

    PubMed

    Mossoba, Magdi M; Moss, Julie; Kramer, John K G

    2009-01-01

    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

  7. Micro-column plasma emission liquid chromatograph

    DOEpatents

    Gay, Don D.

    1984-01-01

    In a direct current plasma emission spectrometer for use in combination with a micro-column liquid chromatograph, an improved plasma source unit. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

  8. Chromatographic Degradation of Phloridzin

    PubMed Central

    Grochowska, Maria J.

    1966-01-01

    Phloridzin, the main phenolic glucoside in apple leaves, has been found to undergo transformation during chromatography. When chromatographed repeatedly in ammoniacal solvents, at least 2 new derivatives appeared. One of these was identified as phloretic acid. When bioassayed in the presence of indole-3-acetic acid this substance behaved as though it promoted the destruction of the auxin. Comparative bioassay with naphthaleneacetic acid suggested that phloretic acid acts on indoleacetic acid destruction via stimulation of indoleacetic acid oxidase. However, at low concentration and in presence of a small amount of phloridzin it also showed a synergistic effect with indoleacetic acid. A substance with the same characteristics was obtained directly from apple leaves, which are known to contain phloridzin when the extracts were chromatographed only once in the same (alkaline) solvent. While not completely confirmed, this suggests that phloretic acid is normally present in apple leaves, where it may affect growth there by promoting indoleacetic acid oxidation. Images PMID:16656273

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  10. iGC2: an architecture for micro gas chromatographs utilizing integrated bi-directional pumps and multi-stage preconcentrators

    NASA Astrophysics Data System (ADS)

    Qin, Yutao; Gianchandani, Yogesh B.

    2014-06-01

    This paper reports an integrated micro gas chromatography (µGC) architecture which utilizes a bi-directional micropump. Four integral components--the bi-directional Knudsen pump (KP2), a two-stage preconcentrator-focuser (PCF2), a separation column, and a gas detector--are integrated in a 4.3 cm3 stack, forming a serial flow path. All four components are fabricated using the same three-mask process. Compared to the conventional approach used with multi-stage preconcentrators, in which valves are used to reverse flow between the sampling phase and the separation phase, this µGC architecture reduces the overall complexity. In this architecture, the vapors being sampled are drawn through the detector and column before reaching the PCF2. The microsystem operation is experimentally validated by quantitative analyses of benzene, toluene, and xylene vapors ranging in concentration from 43-1167 mg m-3.

  11. Gas chromatographic-mass spectrometric analysis of essential oils from Pimpinella aurea, Pimpinella corymbosa, Pimpinella peregrina and Pimpinella puberula gathered from Eastern and Southern Turkey.

    PubMed

    Tabanca, Nurhayat; Demirci, Betul; Kirimer, Nese; Baser, K Husnu Can; Bedir, Erdal; Khan, Ikhlas A; Wedge, David E

    2005-12-02

    Essential oils from fruits, stems and leaves and roots of Pimpinella aurea DC., P. corymbosa Boiss., P. peregrina L. were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques. Fruits and aerial parts of P. puberula (DC.) Boiss were also evaluated. A total of 140 different compounds were identified, and significant qualitative and quantitative differences were observed among the samples. In fact, the main constituents of each species were different and only the oils extracted from roots shared the same principal compound, epoxy pseudoisoeugenyl-2-methyl butyrate (26.8-42.8%). The other fractions were dominated by different sesquiterpene compounds although in three of them, P. aurea stem and leaves, P. puberula fruits and P. puberula stems and leaves, monoterpene constituents also appear as main ones.

  12. Low-resolution mass spectrometric relative response factors (RRFs) and relative retention times (RRTs) on two common gas chromatographic stationary phases for 87 polychlorinated dibenzofurans.

    PubMed

    Lundgren, Kjell; Rappe, Christoffer; Tysklind, Mats

    2004-05-01

    All 87 tetra- to octa-chlorinated dibenzofurans (PCDFs) were analysed using high-resolution gas chromatography/low-resolution mass spectrometry (HRGC-LRMS). The mass spectrometer was operated in two different modes: electron ionisation (EI), and negative ion chemical ionisation (NCI) with methane as a reagent gas. Baseline separation and identification of all PCDF congeners was carried out using one non-polar (DB-5) and one polar (RT-2330) capillary GC column. Relative retention times (RRTs) on both columns, and relative response factors (RRFs) in both EI- and NCI-modes, were calculated for all 87 of the PCDFs. Comparison of the EI-RRFs and NCI-RRFs showed that the mass spectrometric NCI-responses varied to a higher degree than the EI-responses. The level of NCI-response was dependent on the substitution positions of the chlorine atoms on the dibenzofuran molecule skeleton. The ratio between the highest and lowest RRFs was 26 in the NCI-mode, but only 2.3 in the EI-mode. Thus, quantification of tetra- to octa-CDFs in environmental samples using the NCI-mode will result in incorrect estimates of PCDF concentrations unless 13C-labelled internal standards are used for each congener, or RRFs are taken into consideration. In contrast, the quantification of PCDFs in the EI-mode using a single internal 13C-labelled PCDF standard for each PCDF homologue is accurate according to the findings in this investigation. A flue gas sample from a municipal solid waste incinerator (MSWI) analysed in the NCI-mode was quantified with and without NCI-RRFs. When using NCI-RRFs the reported concentration of SigmaPCDFs in the flue gas sample increased by 40%. Furthermore, TCDF analysis was compared using two mass spectrometers (a VG 12-250 and a Finnigan 4500) operating in EI-mode. These quadrupole instruments performed equally well, giving similar EI-RRFs for the tested compounds.

  13. Purge-and-trap isothermal multicapillary gas chromatographic sample introduction accessory for speciation of mercury by microwave-induced plasma atomic emission spectrometry.

    PubMed

    Rodriguez Pereiro, I; Wasik, A; Lobiński, R

    1998-10-01

    A compact device based on purge-and-trap multicapillary gas chromatography was developed for sensitive species-selective analysis of methylmercury and Hg2+ by atomic spectrometry. The operating mode includes in situ conversion of the analyte species to MeEtHg and HgEt2 and cryotrapping of the derivatives formed in a 0.53-mm-i.d. capillary, followed by their flash (< 30 s) isothermal low-temperature separation on a minimulticapillary (22 cm) column. The very low detection limits obtained (0.01 pg mL-1 of Hg for methylmercury) are due to the narrow injection band and reduced peak broadening in a bundle of 0.038-mm capillaries at high flow rates (> 60 mL min-1) compatible with an MIP AES detector (no dilution with a makeup gas is required). Developments regarding each of the steps of the analytical procedure and effects of operational variables (sample volume, purge flow, trap temperature, separation conditions) are discussed. The device allows speciation of MeHg+ and Hg2+ down to 5 pg g-1 in urine and, after a rapid microwave-assisted hydrolysis, down to 0.1 ng g-1 in solid biological samples with a throughput of 6 samples/h. The analytical protocols developed were validated by the analysis of DORM-1 (dogfish muscle), TORT-1 (lobster hepatopancreas), and Seronorm urine certified reference materials.

  14. Gas chromatographic-mass spectrometric analysis of volatiles obtained by four different techniques from Salvia rosifolia Sm., and evaluation for biological activity.

    PubMed

    Ozek, Gulmira; Demirci, Fatih; Ozek, Temel; Tabanca, Nurhayat; Wedge, David E; Khan, Shabana I; Başer, Kemal Hüsnü Can; Duran, Ahmet; Hamzaoglu, Ergin

    2010-01-29

    Four different isolation techniques, conventional hydrodistillation (HD), microwave-assisted hydrodistillation (MWHD), microdistillation (MD) and micro-steam distillation-solid-phase microextraction (MSD-SPME), have been used to analyze the volatile constituents from the aerial parts of Salvia rosifolia Sm. by gas chromatography and gas chromatography coupled to mass spectrometry. HD and MWHD techniques produced quantitatively (yield, 0.39% and 0.40%) and qualitatively (aromatic profile) similar essential oils. alpha-Pinene (15.7-34.8%), 1,8-cineole (16.6-25.1%), beta-pinene (6.7-13.5%), beta-caryophyllene (1.4-5.0%) and caryophyllene oxide (1.4-4.4%) were identified as major constituents of this Turkish endemic species. Besides, the hydrodistilled oil of S. rosifolia was evaluated for antibacterial, antifungal, anticancer, antioxidant and cytotoxic activities. The hydrodistilled oil of S. rosifolia showed antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA) with a MIC value of 125microg/mL. Other human pathogenic microorganisms (Escherichia coli, Pseudomonas aeruginosa, Enterobacter aerogenes, Salmonella typhimurium, Staphylococcus epidermidis, Candida albicans) were also inhibited within a moderate range (MIC=125-1000microg/mL). Antifungal activity of the oil was also observed against the strawberry anthracnose-causing fungal plant pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides. No cytotoxicity was observed for S. rosifolia oil up to 25mg/mL against malignant melanoma, epidermal, ductal and ovary carcinoma.

  15. Optimization of a novel headspace-solid-phase microextraction-gas chromatographic method by means of a Doehlert uniform shell design for the analysis of trace level ethylene oxide residuals in sterilized medical devices.

    PubMed

    DiCicco, Michael P; Lang, Bridget; Harper, Thomas I

    2009-06-01

    Medical devices sterilized by ethylene oxide (EtO) retain trace quantities of EtO residuals, which may irritate patients' tissue. Reliably quantifying trace level EtO residuals in small medical devices requires an extremely sensitive analytical method. In this research, a Doehlert uniform shell design was utilized in obtaining a response surface to optimize a novel headspace-solid-phase microextraction-gas chromatographic (HS-SPME-GC) method developed for analyzing trace levels of EtO residuals in sterilized medical devices, by evaluating sterilized, polymer-coated, drug-eluting cardiovascular stents. The effects of four independent experimental variables (HS-SPME desorption time, extraction temperature, GC inlet temperature and extraction time) on GC peak area response of EtO were investigated simultaneously and the most influential experimental variables determined were extraction temperature and GC inlet temperature, with the fitted model showing no evidence of lack-of-fit. The optimized HS-SPME-GC method demonstrated overall good linearity/linear range, accuracy, repeatability, reproducibility, absolute recovery and high sensitivity. This novel method was successfully applied to analysis of trace levels of EtO residuals in sterilized/aerated cardiovascular stents of various lengths and internal diameter, where, upon heating, trace EtO residuals fully volatilized into HS for extraction, thereby nullifying matrix effects. As an alternative, this novel HS-SPME-GC method can offer higher sensitivity compared with conventional headspace analyzer-based sampling.

  16. 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).

    PubMed

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

    2011-04-01

    The chemical warfare agent O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate (VX) and many related degradation products produce poorly diagnostic electron ionization (EI) mass spectra by transmission quadrupole mass spectrometry. Thus, chemical ionization (CI) is often used for these analytes. In this work, pseudomolecular ([M+H](+)) 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.

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

    PubMed

    Zhang, Chun-Yun; Chai, Xin-Sheng

    2015-03-13

    A novel method for the determination of the diffusion coefficient (D) of methanol in water and olive oil has been developed. Based on multiple headspace extraction gas chromatography (MHE-GC), the methanol released from the liquid sample of interest in a closed sample vial was determined in a stepwise fashion. A theoretical model was derived to establish the relationship between the diffusion coefficient and the GC signals from MHE-GC measurements. The results showed that the present method has an excellent precision (RSD<1%) in the linear fitting procedure and good accuracy for the diffusion coefficients of methanol in both water and olive oil, when compared with data reported in the literature. The present method is simple and practical and can be a valuable tool for the determination of the diffusion coefficient of volatile analyte(s) into food simulants from food and beverage packaging material, both in research studies and in actual applications.

  18. Gas chromatographic analysis of fatty acid methyl esters of milk fat by an ionic liquid derived from L-phenylalanine as the stationary phase.

    PubMed

    González Mendoza, Laura; González-Álvarez, Jaime; Fernández Gonzalo, Carla; Arias-Abrodo, Pilar; Altava, Belén; Luis, Santiago V; Burguete, Maria Isabel; Gutiérrez-Álvarez, María Dolores

    2015-10-01

    A Gas Chromatography (GC) method has been developed for the separation and characterization of the different fatty acids in anhydrous milk fat (AMF) by means of an ionic liquid stationary phase, characterized by a monocationic imidazolium salt derived from L-phenylalanine. The inner surface of a fused silica capillary column was modified using this ionic liquid functionality and 3-aminopropyldiethoxymethyl silane. This coated GC column, which exhibited good thermal stability (270°C) and good efficiency (2700 plates/m), has been characterized using the Abraham solvation parameter model. The intra-day and inter-day precision of the method have been evaluated, obtaining relative standard deviations (RSD) from 0.99% to 4.0% and from 2.8% to 9.2%, respectively. Furthermore, recoveries from 90% and 99% have been achieved.

  19. Gas chromatographic determination of N-nitrosamines, aromatic amines, and melamine in milk and dairy products using an automatic solid-phase extraction system.

    PubMed

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

    2011-07-13

    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.

  20. The use of a gas chromatograph coupled to a metal oxide sensor for rapid assessment of stool samples from irritable bowel syndrome and inflammatory bowel disease patients.

    PubMed

    Shepherd, S F; McGuire, N D; de Lacy Costello, B P J; Ewen, R J; Jayasena, D H; Vaughan, K; Ahmed, I; Probert, C S; Ratcliffe, N M

    2014-06-01

    There is much clinical interest in the development of a low-cost and reliable test for diagnosing inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), two very distinct diseases that can present with similar symptoms. The assessment of stool samples for the diagnosis of gastro-intestinal diseases is in principle an ideal non-invasive testing method. This paper presents an approach to stool analysis using headspace gas chromatography and a single metal oxide sensor coupled to artificial neural network software. Currently, the system is able to distinguish samples from patients with IBS from patients with IBD with a sensitivity and specificity of 76% and 88% respectively, with an overall mean predictive accuracy of 76%.

  1. Analytical Method for the Detection of Ozone Depleting Chemicals (ODC) in Commercial Products Using a Gas Chromatograph with an Electron Capture Detector (GC-ECD)

    SciTech Connect

    Lee, Richard N.; Dockendorff, Brian P.; Wright, Bob W.

    2008-08-01

    This document describes an analytical procedure that was developed for the trace level detection of residual ozone depleting chemicals (ODC) associated with the manufacture of selected commercial products. To ensure the United States meets it obligation under the Montreal Protocol, Congress enacted legislation in 1989 to impose an excise tax on electronic goods imported into the United States that were produced with banned chemicals. This procedure was developed to technically determine if residual ODC chemicals could be detected on electronic circuit boards. The analytical method utilizes a “purge and trap” technique followed by gas chromatography with electron capture detection to capture and analyze the volatile chemicals associated with the matrix. The method describes the procedure, the hardware, operating conditions, calibration, and quality control measures in sufficient detail to allow the capability to be replicated. This document corresponds to internal Standard Operating Procedure (SOP) EFL-130A, Rev 4.

  2. Themodynamics of adsorption and patterns of the gas-chromatographic retention of cyclic amines on surfaces of graphitized thermal carbon black

    NASA Astrophysics Data System (ADS)

    Yashkina, E. A.; Yashkin, S. N.; Svetlov, D. A.; Gorshkov, V. V.

    2015-09-01

    The thermodynamic characteristics of adsorption (TCA) of aniline, cyclohexylamine, and some of their derivatives on surfaces of graphitized thermal carbon black (GTC) are experimentally determined under conditions of gas-adsorption chromatography. It is concluded that the TCA values for the studied compounds depend to a large extent on the features of the geometrical and electronic structure of molecules in the gas phase. The effect of the sp 3- sp 2-rehybridization of nitrogen atoms upon moving from molecules of unsubstituted aniline to N-methyl- and N,N-dimethylanilines are determined, along with the ortho-effects in 2-methyland 2,6-dimethylanilines on the TCA values. It is shown that the above intramolecular effects result in nonadditive contributions to the energy of adsorption of the NH2-group in the a number of the studied compounds. Values of the thermal component of adsorption entropy are calculated, allowing conclusions on the physical state of the molecules of the studied compounds in the field of GTC adsorption forces. The mobility of adsorbate molecules is estimated using models of delocalized and localized adsorption. It is shown that in the series of ortho- meta- para-substituted anilines, the para-isomer is characterized by the highest values of retention on GTC, while the relative order of ortho- and meta-isomer elution is determined by the Van der Waals sizes of substituents in aromatic rings. A conclusion is reached on the high structural selectivity of a GTC surface in respect to positional isomers in the series of studied aniline derivatives.

  3. Enantiodifferentiation of 3-sec-butyl-2-methoxypyrazine in different species using multidimensional and comprehensive two-dimensional gas chromatographic approaches.

    PubMed

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

    2015-01-01

    With respect to the current hypothesis that natural amino acids may serve as starting material for the biosynthesis of alkyl-methoxypyrazines, the enantiomeric distribution of the potent aroma compound 3-sec-butyl-2-methoxypyrazine (SBMP) was determined in various species using heart-cut multidimensional gas chromatography (H/C MDGC) or comprehensive two-dimensional gas chromatography (GC × GC). Complementary to an earlier described separation on octakis-(6-O-methyl-2,3-di-O-pentyl)-γ-cyclodextrin used as chiral stationary phase, we found a reversal of the elution order of SBMP enantiomers on heptakis-(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin, providing further confirmation options for that type of analysis. Optimization of the enantioseparation of SBMP in a single-oven H/C enantio-MDGC system involved the use of a dual-jet cryo modulator for trapping of analytes transferred from the achiral (1)D column to the chiral (2)D column before starting the (2)D enantioseparation with an independent temperature ramp. For the enantiodifferentiation by enantio-GC × GC, the modulation period had to be significantly shortened to avoid loss of chiral resolution gained in (1)D. H/C MDGC with mass spectrometric detection (MS) using selected ion monitoring (SIM) was sufficient for parts per billion level analysis, whereas H/C MDGC-MS/MS or GC × GC time-of-flight (TOF) MS were necessary for parts per trillion level analysis. In various vegetables, lady beetles and Vitis vinifera species analyzed, only (S)-SBMP was detected, supporting the hypothesis of natural amino acids serving as starting material for the biosynthesis of alkyl-methoxypyrazines.

  4. Rapid high-performance liquid chromatographic determination with fluorescence detection of furosemide in human body fluids and its confirmation by gas chromatography-mass spectrometry.

    PubMed

    Saugy, M; Meuwly, P; Munafo, A; Rivier, L

    1991-04-05

    Furosemide (FD: Lasix) is a loop diuretic which strongly increases both urine flow and electrolyte urinary excretion. Healthy volunteers were administered 40 mg orally (dissolved in water) and concentrations of FD were determined in serum and urine for up to 6 h for eight subjects, who absorbed water at a rate of 400 ml/h. Quantification was performed by HPLC with fluorescence detection (excitation at 233 nm, emission at 389 nm) with a limit of detection of 5 ng/ml for a 300-microliters sample. The elution of FD was completed within 4 min using a gradient of acetonitrile concentration rising from 30 to 50% in 0.08 M phosphoric acid. The delay to the peak serum concentration ranged from 60 to 120 min. FD was still easily measurable in the sera from all subjects 6 h after administration. In urine, the excretion rates reached their maximum between 1 and 3 h. The total amount of FD excreted in the urine averaged 11.2 mg (range 7.6-14.0 mg), with a mean urine volume of 3024 ml (range 2620-3596 ml). Moreover, the urine density was lower than 1.010 (recommended as an upper limit in doping analysis to screen diuretics) only for 2 h. An additional volunteer was administered 40 mg of FD and his urine was collected over a longer period. FD was still detectable 48 h after intake. Gas chromatography-mass spectrometry with different types of ionization was used to confirm the occurrence of FD after permethylation of the extract. Negative-ion chemical ionization, with ammonia as reactant gas, was found to be the most sensitive method of detection.

  5. Gas chromatographic method using electron-capture detection for the determination of musk xylene in human blood samples. Biological monitoring of the general population.

    PubMed

    Angerer, J; Käfferlein, H U

    1997-05-23

    Musk xylene (2,4,6-trinitro-1,3-dimethyl-5-tert.-butylbenzene, MX), a synthetic musk often used in different fragrances and soaps to substitute the natural musk, is a potential contaminant of humans. In this publication, a specific and sensitive detection method for the determination of musk xylene in human blood samples is described. The clean-up of the blood samples includes an extraction step followed by a solid-phase adsorption to separate MX from other plasma components. Separation and detection was carried out by capillary gas chromatography and an electron capture detector (GC-ECD). The results were verified using qualitative capillary gas chromatography and a mass selective detector with electron impact ionisation (GC-EI-MS). epsilon-Hexachlorocyclohexane (epsilon-HCH) is used as internal standard. The reliability of the GC-ECD method has been proved. The relative standard deviations of the within-series imprecision were 12.7% for samples with a concentration of 0.5 microg/l and 2.1% for samples with a concentration of 5.0 microg/l, whereas the relative standard deviations for the between-day imprecision were 14.9% (0.5 microg/l samples) and 3.4% (5.0 microg/l samples). The losses during sample treatment were between 10.1% and 17.8%. No interfering peaks were observed. The absolute detection limit was 0.1 microg/l plasma. A total of 72 human blood samples were analysed to determine the MX concentrations within the general population. In 66 of the 72 human blood samples, the MX concentrations ranged from 0.10 to 1.12 microg/l plasma for the described method. In six samples no MX was detected. The median concentration was 0.24+/-0.23 microg MX/l plasma. The 95 percentile was 0.79 microg/l. No correlation could be found between MX concentrations and smoking habit, broca index, age, sex as well as fish consumption habits. Nevertheless, the results demonstrate the exposure of the general population to MX.

  6. Comparison of two clean-up methodologies for the gas chromatographic/mass spectrometric determination of low nanogram/gram levels of polynuclear aromatic hydrocarbons in seafood.

    PubMed

    Nyman, P J; Perfetti, G A; Joe, F L; Diachenko, G W

    1993-01-01

    The March 1989 oil spill in Alaska prompted the Food and Drug Administration (FDA) to conduct a thorough investigation of clean-up methodologies aimed at determining low ng/g (ppb) levels of polynuclear aromatic hydrocarbons (PAHs) in seafood. The clean-ups from a modified FDA method and a National Marine Fisheries Service (NMFS) method were evaluated on the basis of the determination of 18 PAHs at levels ranging from 1 to 5 ppb by gas chromatography/mass spectrometry. In the modified FDA method, seafood extracts were purified by a liquid-liquid partition followed by a three-step elution through silica, alumina, and C18 solid-phase extraction cartridges. In the NMFS method, seafood extracts were purified by column chromatography through a deactivated silica gel/alumina column and a gel permeation high performance liquid chromatography column. Both methods quantitated 18 PAHs at levels ranging from 1 to 5 ppb. With the exception of naphthalene, average recoveries based on internal deuterated standards ranged from 73 to 144% for the modified FDA method and 63 to 106% for the NMFS method.

  7. Headspace, solid-phase micro-extraction, gas chromatographic-mass spectrometric analysis of terpenoids in the latex of Euphorbia species.

    PubMed

    Patel, Asmita V; Sumner, Stephen; Thompson, H Leslie; Blunden, Gerald; Wright, David; Liu, Jun-Feng; Zan, Jun-Feng

    2013-01-01

    The volatile and semi-volatile terpenoids in the latex of Euphorbia amygdaloides, E. exigua, E. helioscopia, and E. peplus were analyzed by headspace, solid-phase micro-extraction (HS-SPME), coupled with gas chromatography-mass spectrometry. The volatiles were extracted using a 100 microm polydimethylsiloxane SPME fiber under optimized extraction conditions. The compounds detected encompassed a range of chemical classes, but only terpenoids were evaluated. Only sesquiterpene hydrocarbons were detected in the tested samples of E. exigua, E. helioscopia, and E. peplus, with beta-caryophyllene being the major one, but were never recorded in latex samples of E. amygdaloides, in which only the diterpene hydrocarbon kaur-16-ene was detected. Alpha-Humulene was consistently found in samples of E. helioscopia, and E. peplus, but never in those of the other two species. These preliminary results show that the developed procedure is suitable for the analysis of small samples of Euphorbia latex and that, for each individual species, there is very little qualitative difference between samples, regardless of either place or date of collection.

  8. High-separation efficiency micro-fabricated multi-capillary gas chromatographic columns for simulants of the nerve agents and blister agents

    NASA Astrophysics Data System (ADS)

    Li, Yi; Du, Xiaosong; Wang, Yang; Tai, Huiling; Qiu, Dong; Lin, Qinghao; Jiang, Yadong

    2014-05-01

    To achieve both high speed and separation efficiency in the separation of a mixture of nerve and blister agent simulants, a high-aspect-ratio micro-fabricated multi-capillary column (MCC, a 50-cm-long, 450-μm-deep, and 60-μm-wide four-capillary column) was fabricated by the application of the microelectromechanical system (MEMS) techniques. Mixtures of chemical warfare agent (CWA) simulants - dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), and methyl salicylate - were used as samples. The fabricated MCC allowed for the separation of all the components of the gaseous mixture within 24 s, even when the difference in boiling point was 4°C, as in the case of TEP and methyl salicylate. Furthermore, interfering agents - dichloromethane, ethanol, and toluene - were also included in the subsequent gaseous mixture samples. The boiling point of these six components ranged from 78°C to 219°C. All six components were clearly separated within 70 s. This study is the first to report the clear separation of gas mixtures of components with close boiling points. The column efficiency was experimentally determined to be 12,810 plates/m.

  9. Development of an equilibrium headspace gas chromatographic method for the measurement of noncovalent association and partitioning of n-alkylbenzenes at infinite dilution in fulvic acid pseudophase.

    PubMed

    Eljack, Mahmoud D; Wilson, Rachael E; Hussam, Abul; Khan, Shahamat U

    2015-02-27

    Fulvic acid (FA), the most important water soluble fraction of humic substances in nature, is known to form aggregate pseudophase and complexes with organic and inorganic species. Here, we report a novel equilibrium headspace gas chromatography (eHSGC) and a two-step reaction model to measure n-alkylbenzene-FA association constant (K11) and n-alkylbenzene-pseudophase FAn association constant (Kn1) without solute concentration and response factor. The K11 and Kn1 values were 2-3 orders of magnitude higher than those for sodium dodecylsulfate. Changes in peak area were used to calculate the critical FA-aggregation concentration (cfc), mole fraction based partition coefficients (Kx), activity coefficients of solute inside the aggregate pseudophase (γm(∞)), and transfer free energies of alkyl CH2 at infinite dilution. The cfc was found to be 10±0.5μM. The Kx values are of the order of 10(7) in the FA-aggregate pseudophase. The data shows that benzene has the lowest (0.0002) and n-butylbenzene has the highest (0.01) γm(∞) values, which are seven orders of magnitude smaller than γw(∞) in water. The transfer free energy of association of a CH2 group, -155cal/mol, compared to that of benzene, -9722cal/mol, indicates that the FA-aggregate pseudophase is more polarizable benzene-like and less n-alkane aliphatic-like.

  10. Comparison of differential mobility spectrometry and mass spectrometry for gas chromatographic detection of ignitable liquids from fire debris using projected difference resolution.

    PubMed

    Lu, Yao; Chen, Ping; Harrington, Peter B

    2009-08-01

    The significance of forensic arson analysis accelerates the applications of new technologies in this area. Based on the previously reported application of differential mobility spectrometry (DMS) as a detection method for gas chromatography (GC) in arson analysis, the performances of DMS and mass spectrometry (MS) were compared using a novel chemometric tool, projected difference resolutions (PDRs). The PDR results show that one-way mass spectra data exhibit higher resolution than DMS data, while total ion chromatograms from GC-DMS show higher resolution than that from GC/MS for differentiating seven kinds of ignitable liquids. Combining the information from both chromatography and spectra, two-way data always have higher resolution than one-way data for these two detection methods, and GC/MS would exhibit better performance than GC-DMS according to the minimum resolution value. To verify the PDR results, a fuzzy rule-building expert system was applied for classifying these seven kinds of ignitable liquids from fire debris based on GC-DMS and GC/MS data, respectively. The prediction accuracies were consistent with PDR results, which proved that PDR is a powerful tool in comparing the performances of different analysis methods for pattern recognition.

  11. Sample cleanup and reversed-phase high-performance liquid chromatographic analysis of polar aromatic compounds in groundwater samples from a former gas plant.

    PubMed

    Müller, M B; Zwiener, C; Frimmel, F H

    1999-11-12

    A method for the analysis of the polar aromatic compounds 1H-quinolin-4-one (Q), 10H-acridin-9-one (A), 5H-phenanthridin-6-one (P) and 9H-fluoren-9-one (F) in aqueous solutions has been developed. The method comprises steps for sample preparation (solid-phase extraction, cleanup) and analytical determination by means of reversed-phase high-performance liquid chromatography (RP-HPLC). For the cleanup step the suitability of two different sorbents (alternative A: silica gel, alternative B: LiChrolut EN) was investigated. Alternative B depicted several advantages, in particular higher sorbent capacity, faster and less complicated handling, higher recovery and better reproducibility. For Q, A and P, reproducibility of all method steps is better than 13%, with recovery rates ranging from 76% to 105% (n=3). Alternative B was applied to groundwater samples from a former gas plant. The analytes A and P could be detected at concentrations in the micro/l range.

  12. Comparison of solid-phase microextraction and dynamic headspace methods for the gas chromatographic-mass spectrometric analysis of light-induced lipid oxidation products in milk.

    PubMed

    Marsili, R T

    1999-01-01

    A sensitive, rapid procedure for testing lipid oxidation products in milk is developed using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry. SPME is as sensitive as dynamic headspace (DH) analysis for measuring the pentanal and hexanal produced in milk after exposure to light. Furthermore, compared with DH, SPME is less expensive and demonstrates better precision and accuracy. In addition, SPME does not exhibit carryover or septa artifact peaks. The linearity of calibration curves (based on the method of additions technique with an internal standard) is consistently better for SPME than for DH. Furthermore, replicate analyses of pentanal and hexanal spiked in skim milk and 2% milk at 2 ng/mL demonstrate significantly lower coefficients of variation using SPME. To further test the practicality of SPME for measuring light-induced chemical changes in milk, 2% milk and skim milk samples are exposed to fluorescent light (200 foot-candles) for 0, 3, 6, 9, 12, 17, 24, and 48 h and analyzed by SPME and DH. Pentanal and hexanal in all samples are measured by SPME and DH. Correlation coefficients of resulting plots indicate that SPME is more accurate than DH in measuring the quantity of lipid oxidation products in milk.

  13. QuEChERS Method Followed by Solid Phase Extraction Method for Gas Chromatographic-Mass Spectrometric Determination of Polycyclic Aromatic Hydrocarbons in Fish

    PubMed Central

    Khorshid, Mona; Souaya, Eglal R.; Hamzawy, Ahmed H.; Mohammed, Moustapha N.

    2015-01-01

    A gas chromatography equipped with mass spectrometer (GCMS) method was developed and validated for determination of 16 polycyclic aromatic hydrocarbons (PAHs) in fish using modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for extraction and solid phase extraction for sample cleanup to remove most of the coextract combined with GCMS for determination of low concentration of selected group of PAHs in homogenized fish samples. PAHs were separated on a GCMS with HP-5ms Ultra Inert GC Column (30 m, 0.25 mm, and 0.25 µm). Mean recovery ranged from 56 to 115%. The extraction efficiency was consistent over the entire range where indeno(1,2,3-cd)pyrene and benzo(g,h,i)perylene showed recovery (65, 69%), respectively, at 2 µg/kg. No significant dispersion of results was observed for the other remaining PAHs and recovery did not differ substantially, and at the lowest and the highest concentrations mean recovery and RSD% showed that most of PAHs were between 70% and 120% with RSD less than 10%. The measurement uncertainty is expressed as expanded uncertainty and in terms of relative standard deviation (at 95% confidence level) is ±12%. This method is suitable for laboratories engaged daily in routine analysis of a large number of samples. PMID:25873966

  14. Preparation and characterization - including in situ Small Angle X-Ray Scattering - of gas chromatographic capillary columns with mesoporous silica thin films as stationary phases.

    PubMed

    Lefebvre, D; Rayes, R Sayah-El; Jousseaume, V; Maret, M; Veyre, L; Charleux, B; Thieuleux, C; Ricoul, F

    2015-09-25

    In this study the preparation of various mesoporous silica thin films as new stationary phases for gas chromatography (GC) columns is presented. The synthesis was performed inside capillaries via a sol-gel process using a templating route. The as-obtained columns were found to be highly efficient for the fast separation of light n-alkanes (C1-C5) mixture; these columns exhibiting a normalized retention 30 times higher than that of a commercially available silica column used as standard. A particular effort was directed towards the characterization of the stationary phase physical features: thin film inspection by Scanning Electron Microscopy and, for the first time to our knowledge, in situ SAXS characterization using synchrotron radiation were used to study the impact of the pore-network structuration on the GC properties. Worm-like, cubic and hexagonal phases were observed for specific preparation conditions. Unexpectedly, the normalized retention relative to film thickness appeared higher with disordering of the pores network.

  15. Gas chromatographic mass spectrometric determination of 1,2,3-propanetrioltrinitrate (nitroglycerin) in human plasma using the nitrogen-15 labelled compound as internal standard.

    PubMed

    Gerardin, A; Gaudry, D; Wantiez, D

    1982-08-01

    A method for the quantitative determinatio of 1,2,3-propanetrioltrinitrate (nitroglycerin) in human plasma by gas chromatography mass spectrometry has been developed. After addition of 1,2,3 and methyl acetate (90 : 10). The extracts are purified by partition between, first, the extraction solvent and a mixture of acetonitrile and water (60 : 40) and, secondly, the resultant aqueous phase and benzene. THe solvent is evaporated to a small volume before injection. The fragment ions at m/z 46 and 47 are monitored for the measurement of the [NO2]+ and [15NO2]+ ions using electron impact ionization. The mean recovery (%) +/- SD in blind plasma samples spiked with amounts in the concentration range 0.35-3.52 nmol 1(-1), was 97.4 +/- 9.0 (n = 58). Within a day, recovery experiments gave rise to coefficients of variation of 9.6, 6.4 and 2.7% at the levels 0.44, 0.88 and 11 nmol 1(-1), respectively. Concentrations in plasma down to about 0.2 nmol 1(-1) (50 pg ml-1) could be estimated. Percent recovery of duplicate determinations in the range 0.5-1.96 nmol 1(-1) +/- SD was 99.4 +/- 6.0 (n = 80).

  16. High-separation efficiency micro-fabricated multi-capillary gas chromatographic columns for simulants of the nerve agents and blister agents

    PubMed Central

    2014-01-01

    To achieve both high speed and separation efficiency in the separation of a mixture of nerve and blister agent simulants, a high-aspect-ratio micro-fabricated multi-capillary column (MCC, a 50-cm-long, 450-μm-deep, and 60-μm-wide four-capillary column) was fabricated by the application of the microelectromechanical system (MEMS) techniques. Mixtures of chemical warfare agent (CWA) simulants - dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), and methyl salicylate - were used as samples. The fabricated MCC allowed for the separation of all the components of the gaseous mixture within 24 s, even when the difference in boiling point was 4°C, as in the case of TEP and methyl salicylate. Furthermore, interfering agents - dichloromethane, ethanol, and toluene - were also included in the subsequent gaseous mixture samples. The boiling point of these six components ranged from 78°C to 219°C. All six components were clearly separated within 70 s. This study is the first to report the clear separation of gas mixtures of components with close boiling points. The column efficiency was experimentally determined to be 12,810 plates/m. PMID:24899869

  17. Improved conventional and microwave-assisted silylation protocols for simultaneous gas chromatographic determination of tocopherols and sterols: Method development and multi-response optimization.

    PubMed

    Poojary, Mahesha M; Passamonti, Paolo

    2016-12-09

    This paper reports on improved conventional thermal silylation (CTS) and microwave-assisted silylation (MAS) methods for simultaneous determination of tocopherols and sterols by gas chromatography. Reaction parameters in each of the methods developed were systematically optimized using a full factorial design followed by a central composite design. Initially, experimental conditions for CTS were optimized using a block heater. Further, a rapid MAS was developed and optimized. To understand microwave heating mechanisms, MAS was optimized by two distinct modes of microwave heating: temperature-controlled MAS and power-controlled MAS, using dedicated instruments where reaction temperature and microwave power level were controlled and monitored online. Developed methods: were compared with routine overnight derivatization. On a comprehensive level, while both CTS and MAS were found to be efficient derivatization techniques, MAS significantly reduced the reaction time. The optimal derivatization temperature and time for CTS found to be 55°C and 54min, while it was 87°C and 1.2min for temperature-controlled MAS. Further, a microwave power of 300W and a derivatization time 0.5min found to be optimal for power-controlled MAS. The use of an appropriate derivatization solvent, such as pyridine, was found to be critical for the successful determination. Catalysts, like potassium acetate and 4-dimethylaminopyridine, enhanced the efficiency slightly. The developed methods showed excellent analytical performance in terms of linearity, accuracy and precision.

  18. Determination of tetramethylenedisulfotetramine in human urine with gas chromatograph-flame thermionic detection coupling with direct immersed solid-phase micro-extraction.

    PubMed

    Zeng, Dong; Chen, Bo; Yao, Shouzhuo; Ying, Jianying

    2006-06-02

    An analytical method for determination of tetramethylenedisulfotetramine (tetramine) in human urine by gas chromatography-flame thermionic detection (GC-FTD) coupling with a direct immersed solid-phase micro-extraction (DI-SPME) was developed. The enrichment effects of three fiber coatings of SPME for tetramine were compared. Results showed that the enrichment effect of polar 85 microm polyacrylate (PA) coating was better than that of apolar 100 and 7 microm polydimethylsiloxane (PDMS) coatings. Other experimental parameters, such as ionic strength, volume, temperature of sample solution and time for extraction, time and temperature for desorption, were also optimized. The correlation coefficient of the calibration curve was 0.9998 in the range of 0.082-41.0 ng/mL for tetramine. The limit of quantitation of tetramine in urine was 0.082 ng/mL. In this method, the sample pretreatment is simple and convenient. As a monitoring means, it has been successfully applied to detection of tetramine toxicosis in criminal cases, as well as clinical therapy of poisoned sufferer.

  19. Development and characterization of a solvent extraction-gas chromatographic/mass spectrometric method for the analysis of perfluorooctanesulfonamide compounds in solid matrices.

    PubMed

    Tittlemier, Sheryl A; Pepper, Karen; Edwards, Laura; Tomy, Gregg

    2005-02-25

    A method utilizing solvent extraction and analysis by gas chromatography-positive chemical ionization mass spectrometry (SE-GC-PCIMS) was developed for the analysis of three neutral hydrophobic perfluorooctanesulfonamide compounds [perfluorooctanesulfonamide (PFOSA), N-ethyl perfluorooctanesulfonamide (N-EtPFOSA), and N,N-diethyl perfluorooctanesulfonamide (N,N-Et2PFOSA)]. These compounds are suspected metabolic precursors of perfluorooctane sulfonate. The SE-GC-PCI-MS method was used to analyze all three perfluorooctanesulfonamides in fast food, fish, and Arctic marine mammal liver samples. The SE-GC-PCI-MS method produced relatively higher recoveries of the analytes (averaging 83 +/- 6%, 84 +/- 9%, and 89 +/- 19% for N,N-Et2PFOSA, N-EtPFOSA, and PFOSA, respectively) with lower coefficients of variation, and less susceptibility to matrix effects, than ion pair extraction-liquid chromatography-tandem mass spectrometric methods. Method detection limits (MDLs) were 100, 120, and 250 pg/g for N,N-Et2PFOSA, N-EtPFOSA, and PFOSA, respectively. The three compounds were found at concentrations ranging from below the MDL to 22 ng/g wet weight in fast food, fish, and Arctic marine mammal liver samples.

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

    PubMed

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

    2010-02-19

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

  1. 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".

    PubMed

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

    2006-10-01

    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.

  2. A new headspace gas chromatographic method for the determination of methanol content in paper materials used for food and drink packaging.

    PubMed

    Hu, Hui-Chao; Tian, Ying-Xin; Jin, Hui-Jun; Chai, Xin-Sheng; Barnes, Donald G

    2013-10-02

    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 <3.5%, with recovery in the range of 93.4-102%. The present method is reliable, accurate, and suitable for use in batch testing of the 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.

  3. Chromatographic methods of fractionation.

    PubMed

    Friesen, A D

    1987-01-01

    Chromatography's functional versatility, separation efficiency, gentle non-denaturing separating process and ease of automation and scale-up make it attractive for industrial scale protein purification. The Winnipeg Rh Institute's new Plasma Fractionation facility is an example of the use of chromatography for the large scale purification of plasma protein fractions. The fractionation facility has a capacity to process 800 litres of plasma per batch into blood clotting factor VIII and IX, albumin and intravenous immune serum globulin (i.v. ISG). Albumin and i.v. ISG are purified using ion exchange columns of DEAE-Sepharose (230 litre size), DEAE-Biogel (150 litre size) and CM-Sepharose (150 litre size). The chromatographic process is automated using a Modicon 584 Programmable Logic Controller to regulate valves, pumps and sensors which control plasma flow during fractionation. The stainless steel tanks and piping are automatically cleaned-in-place. The high degree of automation and cleaning provides efficient operation and sanitary processing. Chromatographic methods (DEAE-Sepharose and metal chelation) are also being used at the pilot scale to purify the human blood products superoxide dismutase and hemoglobin from outdated red blood cells. Characterization of the protein fractions produced by chromatography has shown them to be of equal or higher quality than fractions produced by other techniques.

  4. Electron capture gas-liquid chromatographic study of metabolites produced by some arthritic transudate-associated organisms in vitro and in vivo in rabbit models.

    PubMed

    Brooks, J B; Melton, A R

    1978-10-01

    Computerized, frequency-pulsed, modulated electron capture gas-liquid chromatography was used to study the acid metabolites produced in vitro in fetal calf serum and in vivo in an animal chamber model. Several strains of Diplostreptococcus agalactiae, Propionibacterium acnes, Staphylococcus aureus, and Streptococcus serogroups A, B, and G were studied. All of these organisms have been reported to be associated with arthritic transudates in humans. Metabolites were detected by this method from derivatized extracts of both spent fetal calf serum and chamber fluids. Since there was little host response to the organisms cultured in the chambers, it is highly probable that the products detected represent metabolites produced in an in vivo type of environment. The metabolic patterns were reproducible and exhibited many similarities in vitro and in vivo. Production of the acids detected was reproducible, and these acids were useful identification markers. The data support published reports (J. B. Brooks, C. C. Alley, and J. A. Liddle, Anal. Chem. 46: 1930-1934, 1974; J. B. Brooks, G. Choudhary, R. B. Craven, D. Edman, C. C. Alley, and J. A. Liddle, J. Clin. Microbiol. 5:625-628, 1977; J. B. Brooks, R. B. Craven, A. R. Melton, and C. C. Alley, in H. H. Johnson and W. B. Newson, ed., Second International Symposium on Rapid Methods and Automation on Microbiology, 1976; J. B. Brooks, R. B. Craven, D. Schlossberg, C. C. Alley, and F. M. Pitts, J. Clin. Microbiol. 8:203-208, 1978; J. B. Brooks, D. S. Kellogg, C. C. Alley, H. B. Short, and H. H. Handsfield, J. Infect. Dis. 129:660-668, 1974) that bacterial metabolites might be detectable in diseased body fluids. The growth characteristics of the organisms in the animal model and fetal calf serum are discussed, and a moderately priced computer for performing data manipulations is evaluated.

  5. Simultaneous determination of amphetamine and methamphetamine enantiomers in urine by simultaneous liquid-liquid extraction and diastereomeric derivatization followed by gas chromatographic-isotope dilution mass spectrometry.

    PubMed

    Wang, Sheng-Meng; Wang, Ting-Cheng; Giang, Yun-Seng

    2005-02-25

    A simple, rapid, reliable, and economic analytical scheme starting with in situ liquid-liquid extraction and asymmetric (or diastereomeric) chemical derivatization (ChD) followed by gas chromatography (GC)-isotope dilution mass spectrometry (MS) is described for the simultaneous determination of D- and L-amphetamine (AP) and methamphetamine (MA) in urine which could have resulted from the administration of various forms of questioned amphetamines or amphetamines-generating drugs. By using L-N-trifluoroacetyl-1-prolyl chloride (L-TPC) as chiral derivatizing agent, resolutions of 2.2 and 2.0 were achieved for the separation of AP and MA enantiomeric pairs, respectively, on an ordinary HP-5MS capillary column. The GC-MS quantitation was carried out in the selected ion monitoring (SIM) mode using m/z 237 and 251 as the quantifier ions for the respective diastereomeric pairs of AP-L-TPC and MA-L-TPC. The calibration curves plotted for the two pairs of analytes stretch with good linearity down to 45 ng/mL, and the limits of detection and quantitation determined were as low as 40 and 45 ng/mL, respectively. Also, a comparative study using 10 real-case urine specimens previously screened as positive for MA administration showed mostly tolerable biases between the two sums (of concentration) of D- and L-MA obtained via an asymmetric L-TPC-ChD approach and via an ordinary pentafluoropropionylation (PFPA-ChD) approach, respectively, as well as between the two sums of D- and L-AP obtained thereupon, thus validating the proposed analytical scheme as a promising forensic protocol for the detailed analysis of enantiomeric amphetamines in urine.

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

    PubMed

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

    2015-12-18

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

  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.

    PubMed

    Pätzold, R; Brückner, H

    2006-07-01

    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. A new method for direct total OH reactivity measurements using a fast Gas Chromatographic Photo-Ionization Detector (GC-PID)

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Sinha, V.; Bockisch, S.; Klüpfel, T.; Williams, J.

    2012-04-01

    *160*400 mm), light (8 kg) and provides a good time resolution (50-60 sec). The method is able to operate in ambient conditions, requires no external carrier gas, and an internal battery provides power for ca. 12 hours which makes the instrument suitable for outdoor field campaigns. The GC-PID detection limit for pyrrole is 3 ppb, which is adequate for this application and total OH reactivity can be measured under optimum conditions down to 4 sec-1. The new set-up has been tested in parallel to previously validated PTR-MS measurements for CRM in laboratory experiments, a plant chamber, and boreal forest field studies. Advantages and drawbacks of the new technique are discussed. Although the polymerization of pyrrole on the detector window remains a weakness in the present version of the system, in general the GC-PID produces acceptable results. [1] Calpini et al, 1999, Analusis, 27, 328 [2] Kovacs and Brune. 2001, Journal of Atmospheric Chemistry, 39, 105-122 [3] V. Sinha et al, 2008, Atmos. Chem. Phys., 8, 2213-2227 [4] http://www.environics-iut.de/

  9. Gas chromatographic analysis of plant sterols

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  10. Gas Chromatographic Determination of Fatty Acid Compositions.

    ERIC Educational Resources Information Center

    Heinzen, Horacio; And Others

    1985-01-01

    Describes an experiment that: (1) has a derivation step using readily available reagents; (2) requires limited manipulative skills, centering attention on methodology; (3) can be completed within the time constraints of a normal laboratory period; and (4) investigates materials that are easy to acquire and are of great technical/biological…

  11. Note on the chromatographic analyses of marine polyunsaturated fatty acids

    USGS Publications Warehouse

    Schultz, D.M.; Quinn, J.G.

    1977-01-01

    Gas-liquid chromatography was used to study the effects of saponification/methylation and thin-layer chromatographic isolation on the analyses of polyunsaturated fatty acids. Using selected procedures, the qualitative and quantitative distribution of these acids in marine organisms can be determined with a high degree of accuracy. ?? 1977 Springer-Verlag.

  12. Performance evaluation of a versatile multidimensional chromatographic preparative system based on three-dimensional gas chromatography and liquid chromatography-two-dimensional gas chromatography for the collection of volatile constituents.

    PubMed

    Pantò, Sebastiano; Sciarrone, Danilo; Maimone, Mariarosa; Ragonese, Carla; Giofrè, Salvatore; Donato, Paola; Farnetti, Sara; Mondello, Luigi

    2015-10-23

    The present research deals with the multi-collection of the most important sesquiterpene alcohols belonging to sandalwood essential oil, as reported by the international regulations: (Z)-α-santalol, (Z)-α-trans bergamotol, (Z)-β-santalol, epi-(Z)-β-santalol, α-bisabolol, (Z)-lanceol, and (Z)-nuciferol. A versatile multidimensional preparative system, based on the hyphenation of liquid and gas chromatography techniques, was operated in the LC-GC-GC-prep or GC-GC-GC-prep configuration, depending on the concentration to be collected from the sample, without any hardware or software modification. The system was equipped with a silica LC column in combination with polyethylene glycol-poly(5% diphenyl/95% dimethylsiloxane)-medium polarity ionic liquid or β-cyclodextrin based GC stationary phases. The GC-GC-GC-prep configuration was exploited for the collection of four components, by using a conventional split/splitless injector, while the LC-GC-GC-prep approach was applied for three low abundant components (<5%), in order to increase the quantity collected within a single run, by the LC injection of a high sample amount. All target compounds, whose determination is hampered by the unavailability of commercial standards, were collected at milligram levels and with a high degree of purity (>87%).

  13. Micro-column plasma emission liquid chromatograph. [Patent application

    DOEpatents

    Gay, D.D.

    1982-08-12

    In a direct current plasma emission spectrometer for use in combination with a microcolumn liquid chromatograph, an improved plasma source unit is claimed. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

  14. Ask the experts: chromatographic baselines.

    PubMed

    Smith, Graeme; James, Christopher A; Scott, Rebecca; Woolf, Eric

    2014-05-01

    Bioanalysis invited a selection of leading researchers to express their views on chromatographic baseline assignment in the bioanalytical laboratory. The topics discussed include the challenges presented with ensuring automated baseline assignment is correct, when reintegration is necessary, regulation and consistency in terminology. Their enlightening responses provide a valuable insight into developing an industry consensus towards reintegration. An accompanying commentary article in this issue, authored by Howard Hill and colleagues (Huntingdon Life Sciences), provides background to this much debated topic.

  15. Micro and nanotechnologies for the development of an integrated chromatographic system

    NASA Astrophysics Data System (ADS)

    Casals, O.; Romano-Rodríguez, A.; Illa, X.; Zamani, C.; Vilà, A.; Morante, J. R.; Gràcia, I.; Ivanov, P.; Sabaté, N.; Fonseca, L.; Santander, J.; Figueras, E.; Cané, C.

    2007-05-01

    The development of an integrated gas chromatographic system using micro and nanotechnologies is presented in this paper. For this purpose, the different components of the chromatographic system, namely the preconcentrator, the chromatographic column and the gas sensors are being investigated and developed, and the actual state of this investigation is presented. The proposed target application comes from the agrofood industry, in particular the determination of the fish freshness. The structure of the preconcentrator has been fabricated using deep reactive ion etching (DRIE). The same fabrication technique has been employed for the patterning of the silicon microcolumns, which have been sealed with Pyrex glass. Inlet and outlets have been connected and initial experiments of functionalization have been performed. Gas sensors have been obtained by microdeposition of doped WO 3 or SnO II nanomaterials on microhotplates and their responses to the gases of interest have been measured, proving that the target gas concentrations can be detected.

  16. Vibrational Spectroscopy of Chromatographic Interfaces

    SciTech Connect

    Jeanne E. Pemberton

    2011-03-10

    Chromatographic separations play a central role in DOE-supported fundamental research related to energy, biological systems, the environment, and nuclear science. The overall portfolio of research activities in the Separations and Analysis Program within the DOE Office of Basic Energy Sciences includes support for activities designed to develop a molecular-level understanding of the chemical processes that underlie separations for both large-scale and analytical-scale purposes. The research effort funded by this grant award was a continuation of DOE-supported research to develop vibrational spectroscopic methods to characterize the interfacial details of separations processes at a molecular level.

  17. Chromatographic determination of the diffusion coefficients of light hydrocarbons in polymers

    NASA Astrophysics Data System (ADS)

    Yakubenko, E. E.; Korolev, A. A.; Chapala, P. P.; Bermeshev, M. V.; Kanat'eva, A. Yu.; Kurganov, A. A.

    2017-01-01

    Gas-chromatographic determination of the diffusion coefficients that allows for the compressibility of the mobile phase has been suggested. The diffusion coefficients were determined for light hydrocarbons C1-C4 in four polymers with a high free volume, which are candidates for use as gas-separating membranes. The diffusion coefficients calculated from chromatographic data were shown to be one or two orders of magnitude smaller than the values obtained by the membrane method. This may be due to the presence of an additional flow through the membrane caused by the pressure gradient across the membrane in membrane methods.

  18. Chromatographic Separation of Vitamin E Enantiomers.

    PubMed

    Fu, Ju-Yen; Htar, Thet-Thet; De Silva, Leanne; Tan, Doryn Meam-Yee; Chuah, Lay-Hong

    2017-02-04

    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.

  19. Gas amplified ionization detector for gas chromatography

    DOEpatents

    Huston, Gregg C.

    1992-01-01

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

  20. Mass Spectral Investigations on Toxins. 2. Simultaneous Detection and Quantification of Ultra-Trace Levels of Simple Trichothecenes in Environmental and Fermentation Samples by Gas Chromatographic/Negative Ion Chemical Ionization-Mass Spectrometric Techniques

    DTIC Science & Technology

    1987-01-01

    macrocyclic trichothecenes or semisynthetic compounds. Scirpentriol (3a-HOVER), deoxynivalenol (DON), fusarinon-X (FUSX), monoacetoxyscirpenol (MAS) and...S.R. Gas Chromhtog- raphy with Electron Capture and Mass Spectrometric Detection of Deoxynivalenol in Wheat and Other Grains. J. Assoc. Off. Anal. Chem

  1. Trace Gas Analyzer (TGA) program

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The design, fabrication, and test of a breadboard trace gas analyzer (TGA) is documented. The TGA is a gas chromatograph/mass spectrometer system. The gas chromatograph subsystem employs a recirculating hydrogen carrier gas. The recirculation feature minimizes the requirement for transport and storage of large volumes of carrier gas during a mission. The silver-palladium hydrogen separator which permits the removal of the carrier gas and its reuse also decreases vacuum requirements for the mass spectrometer since the mass spectrometer vacuum system need handle only the very low sample pressure, not sample plus carrier. System performance was evaluated with a representative group of compounds.

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

    PubMed

    White, Robert L

    2015-11-20

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

  3. Nanofluidic Size-Exclusion Chromatograph

    NASA Technical Reports Server (NTRS)

    Feldman, Sabrina; Svehla, Danielle; Grunthaner, Frank; Feldman, Jason; Shakkottai, P.

    2004-01-01

    Efforts are under way to develop a nanofluidic size-exclusion chromatograph (SEC), which would be a compact, robust, lightweight instrument for separating molecules of interest according to their sizes and measuring their relative abundances in small samples. About as large as a deck of playing cards, the nanofluidic SEC would serve, in effect, as a laboratory on a chip that would perform the functions of a much larger, conventional, bench-top SEC and ancillary equipment, while consuming much less power and much smaller quantities of reagent and sample materials. Its compactness and low power demand would render it attractive for field applications in which, typically, it would be used to identify and quantitate a broad range of polar and nonpolar organic compounds in soil, ice, and water samples. Size-exclusion chromatography is a special case of high-performance liquid chromatography. In a conventional SEC, a sample plug is driven by pressure along a column packed with silica or polymer beads that contain uniform nanopores. The interstices between, and the pores in, the beads collectively constitute a size-exclusion network. Molecules follow different paths through the size-exclusion network, such that characteristic elution times can be related to sizes of molecules: basically, smaller molecules reach the downstream end of the column after the larger ones do because the smaller ones enter minor pores and stay there for a while, whereas the larger ones do not enter the pores. The volume accessible to molecules gradually diminishes as their size increases. All molecules bigger than a pore size elute together. For most substances, the elution times and sizes of molecules can be correlated directly with molecular weights. Hence, by measuring the flux of molecules arriving at the downstream end as a function of time, one can obtain a liquid mass spectrum for the molecules present in a sample over a broad range of molecular weights.

  4. Multi-residue methods for the determination of over four hundred pesticides in solid and liquid high sucrose content matrices by tandem mass spectrometry coupled with gas and liquid chromatograph.

    PubMed

    Lozowicka, Bozena; Ilyasova, Gulzhakhan; Kaczynski, Piotr; Jankowska, Magdalena; Rutkowska, Ewa; Hrynko, Izabela; Mojsak, Patrycja; Szabunko, Julia

    2016-05-01

    For the first time three methods: matrix solid phase dispersion (MSPD), original and modified QuEChERS, with and without clean up step were studied in order to evaluate the extraction efficiency of various classes of pesticides from solid and liquid high sucrose content matrices. Determinations over four hundred pesticides were performed by gas and liquid chromatography with triple quadrupole mass spectrometry (GC/LC/MS/MS) using multiple reaction monitoring. The proposed methods were validated on sugar beets and their technological product beet molasses. In general, the recoveries obtained for the original QuEChERS and MSPD method were lower (<70%) than for the modified QuEChERS without clean up in sugar beet and with clean up in beet molasses. Among these methods, high extraction yields were achieved as recommended in SANCO/12571/2013, with repeatability of 4.4-19.2% and within-laboratory reproducibility of 7.1-18.4% for citrate QuEChERS, whereas greater ruggedness were observed for MSPD. The limit of quantification (LOQ) at (the lowest MRL=0.01mgkg(-1)e.g. for oxamyl()) or below (0.005mgkg(-1)) the regulatory maximum residue level for the pesticides were achieved. The expanded measurement uncertainty was not higher than 30% for all target analytes. Matrix effects were compared and observed for both matrices at both gas and liquid chromatography. The most compounds showed signal enhancement and it was compensated by using matrix-matched calibration and modified QuEChERS characterized lower matrix effects. The confirmation of suitability citrate QuEChERS optimized method was to use for routine testing of several dozen samples determination and residue of epoxiconazole and tebuconazole (both at 0.01mgkg(-1)) in the samples of beet molasses and cyfluthrin (0.06mgkg(-1)) in sugar beet were found.

  5. 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

    USGS Publications Warehouse

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

    1996-01-01

    A method for the determination of 79 semivolatile organic compounds (SOCs) and 4 surrogate compounds in soils and bottom sediment is described. The SOCs are extracted from bottom sediment by solvent extraction, followed by partial isolation using high-performance gel permeation chromatography (GPC). The SOCs then are qualitatively identified and quantitative concentrations determined by capillary-column gas chromatography/mass spectrometry (GC/MS). This method also is designed for an optional simultaneous isolation of polychlorinated biphenyls (PCBs) and organochlorine (OC) insecticides, including toxaphene. When OCs and PCBs are determined, an additional alumina- over-silica column chromatography step follows GPC cleanup, and quantitation is by dual capillary- column gas chromatography with electron-capture detection (GC/ECD). Bottom-sediment samples are centrifuged to remove excess water and extracted overnight with dichloromethane. The extract is concentrated, centrifuged, and then filtered through a 0.2-micrometer polytetrafluoro-ethylene syringe filter. Two aliquots of the sample extract then are quantitatively injected onto two polystyrene- divinylbenzene GPC columns connected in series. The SOCs are eluted with dichloromethane, a fraction containing the SOCs is collected, and some coextracted interferences, including elemental sulfur, are separated and discarded. The SOC-containing GPC fraction then is analyzed by GC/MS. When desired, a second aliquot from GPC is further processed for OCs and PCBs by combined alumina-over-silica column chromatography. The two fractions produced in this cleanup then are analyzed by GC/ECD. This report fully describes and is limited to the determination of SOCs by GC/MS.

  6. Fermentation condition outweighed truffle species in affecting volatile organic compounds analyzed by chromatographic fingerprint system.

    PubMed

    Tang, Ya-Jie; Wang, Guan; Li, Yuan-Yuan; Zhong, Jian-Jiang

    2009-08-04

    The influences of fermentation conditions and truffle species (i.e., Tuber melanosporum, Tuber sinense, Tuber indicum, and Tuber aestivum) on the volatile organic compounds (VOCs) originated from truffle fermentation mycelia were studied by using chromatographic fingerprint system for the first time. Gas chromatography combined with statistical methods including similarity analysis and hierarchical cluster analysis was applied to develop chromatographic fingerprint system for truffle VOCs evaluation. Fermentation conditions affected the VOCs from truffle fermentation mycelia much more significantly than truffle species. This indicated that it is possible to adjust the aroma of truffle fermentation mycelia similar with the natural fruiting-body through the control of fermentation process.

  7. More than 170 polyunsaturated tocopherol-related compounds in a vitamin E capsule: Countercurrent chromatographic enrichment, gas chromatography/mass spectrometry analysis and preliminary identification of the potential artefacts.

    PubMed

    Hammann, Simon; Kröpfl, Alexander; Vetter, Walter

    2016-12-09

    Tocopherols and tocotrienols (usually summed up as vitamin E) are a class of structurally related natural antioxidants. Commonly, only some of the eight classic representatives (four tocopherols and four tocotrienols) are found with varied composition in food. In this study we fractionated 230mg oil from commercial vitamin E supplement capsules by countercurrent chromatography (CCC) and subsequent analysis by gas chromatography with mass spectrometry (GC/MS) of silylated CCC fractions showed that these eight isomers represented only about 70% of total tocopherol compounds. Detailed analysis enabled the detection of 161T3 isomers (α-, γ- and δ-T3) along with 18 tetra- and several penta-unsaturated isomers (tocools), two tocomonoenol isomers, and several degradation products with shorter isoprenoid side chain (apo-tocools). Altogether, over 170 tocool compounds, most likely artefacts which originated from an inappropriate oil refining process were described in this study. Silver ion high performance liquid chromatography (Ag(+)-HPLC) was used to separate one fraction rich in γ-T3 into four peaks each consisting of at least five peaks according to GC/MS. About ten γ-T3 isomers were also detected in rice bran oils from one producer bought retail in Germany.

  8. Non-targeted metabolomics study for the analysis of chemical compositions in three types of tea by using gas chromatograph-mass spectrometry and liquid chromatography-mass spectrometry.

    PubMed

    Zhang, Lei; Zeng, Zhongda; Ye, Guozhu; Zhao, Chunxia; Lu, Xin; Xu, Guowang

    2014-08-01

    Tea is one of the most widely consumed beverages in the world for its benefits to daily life and health. To discover the difference and correlation of chemical compositions in the three typical types of tea, a non-targeted metabolomics method was developed. After the optimization of extraction methods, gas chromatography-time-of-flight mass spectrometry and liquid chromatography-quadrupole time-of-flight mass spectrometry were applied for metabolomics analysis, 1,812 and 2,608 features were obtained, respectively. By comparing with the known compounds in public and/or commercial databases, 173 compounds were tentatively identified, and 109 of them were experimentally confirmed by standards. Totally, 33 tea samples including 12, 12 and 9 samples of green, oolong and black tea, respectively, were analyzed by using the above two methods. Multivatiate analysis, Mann-Whitney U test and hierarchical cluster analysis were used to find and visualize the differential components in the three types of tea. Finally, 90 compounds, which contain catechins, amino acids, organic acids, flavonol glycosides, alkaloids, carbohydrates, lipids, etc, were found with a significant difference among them. This study demonstrates the potentials and power of metabolomics methods to understand the chemical secrets of tea. This should help a lot to optimize the processes of agriculture, storage, preparation and consumption.

  9. A headspace solid-phase microextraction gas-chromatographic mass-spectrometric method (HS-SPME-GC/MS) to quantify hexanal in butter during storage as marker of lipid oxidation.

    PubMed

    Panseri, Sara; Soncin, Silvia; Chiesa, Luca Maria; Biondi, Pier Antonio

    2011-07-15

    A method using headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC/MS) was developed and validated for the extraction and quantification of hexanal content in butter (at ngg(-1) level) during storage at 4°C. The variability of hexanal content among seasons of production and the influence of high extraction temperature on ex-novo formation of hexanal were also evaluated. The HS-SPME conditions were optimised and analytical parameters of the method (linearity, accuracy, and precision) demonstrate its usefulness. The reproducibility and accuracy of the quantitative analysis was assured by the use of D(12)-hexanal as internal standard. For the applications, the headspace was extracted using CAR/PDMS fiber for 180min at 4°C. Hexanal contents in samples during all storage period (shelf-life) and from butters produced in different seasons were analysed. Butter samples at the end of shelf-life and samples produced in August showed highest values of hexanal, confirming that the temperature both in storage and distribution phases represents a critical factor to maintain the quality of butter.

  10. Liquid-liquid extraction/headspace/gas chromatographic/mass spectrometric determination of benzene, toluene, ethylbenzene, (o-, m- and p-)xylene and styrene in olive oil using surfactant-coated carbon nanotubes as extractant.

    PubMed

    Carrillo-Carrión, Carolina; Lucena, Rafael; Cárdenas, Soledad; Valcárcel, Miguel

    2007-11-09

    BTEX-S compounds are widely distributed in the environment and can be present in different foodstuffs, including olive oil. Taking into account the risks of the exposure to these compounds, analytical methods for their determination in different matrices are mandatory. In this paper, the use of surfactant-coated multiwalled carbon nanotubes as additive in liquid-liquid extraction is applied for the determination of single-ring aromatic compounds in olive oil samples. After sample treatment, the aqueous extracts are subsequently analyzed by headspace/gas chromatography/mass spectrometry allowing the determination of BTEX-S within ca. 15 min. Each stage of the proposed LLE/HS/GC/MS configuration involves a selectivity enhancement avoiding the interference of other compounds of the sample matrix. Limits of detection were in the range 0.25 ng mL(-1) (obtained for ethylbenzene) and 0.43 ng mL(-1) (for benzene). The repeatability of the proposed method expressed as RSD varied between 1.9% (styrene) and 3.3% (benzene) (n=11).

  11. Gas Analyzer

    NASA Technical Reports Server (NTRS)

    1983-01-01

    A miniature gas chromatograph, a system which separates a gaseous mixture into its components and measures the concentration of the individual gases, was designed for the Viking Lander. The technology was further developed under National Institute for Occupational Safety and Health (NIOSH) and funded by Ames Research Center/Stanford as a toxic gas leak detection device. Three researchers on the project later formed Microsensor Technology, Inc. to commercialize the product. It is a battery-powered system consisting of a sensing wand connected to a computerized analyzer. Marketed as the Michromonitor 500, it has a wide range of applications.

  12. Gas chromatographic-tandem mass spectrometric analysis of β-lyase metabolites of sulfur mustard adducts with glutathione in urine and its use in a rabbit cutaneous exposure model.

    PubMed

    Lin, Ying; Dong, Yuan; Chen, Jia; Li, Chun-Zheng; Nie, Zhi-Yong; Guo, Lei; Liu, Qin; Xie, Jian-Wei

    2014-01-15

    A method for quantitation of β-lyase metabolites of sulfur mustard (SM) adducts with glutathione has been developed and validated using gas chromatography-tandem mass spectrometry (GC-MS/MS). The linear range of quantitation was 0.1-1000ng/mL in urine with a method detection limit of 0.02ng/mL. The method was applied in a rabbit exposure model. Domestic rabbits were cutaneously exposed to neat liquid SM in three dosage levels, and the β-lyase metabolites in urine were determined as 1,1'-sulfonylbis[2-(methylthio)ethane] (SBMTE). The study showed that even though more than 99% of the total amount of β-lyase metabolites was excreted in the first week after exposure, the β-lyase metabolites of SM adducts with glutathione could be detected in urine from rabbits for up to 3 or 4 weeks after the SM cutaneous exposure. For high dosage group (15mg/kg, 0.15 LD50), the mean concentration of SBMTE detected was 0.32ng/mL on day 28. For middle (5mg/kg, 0.05 LD50) and low (2mg/kg, 0.02 LD50) dosage groups, the mean concentrations of SBMTE were 0.07ng/mL and 0.02ng/mL on day 21, respectively. The data from this study indicate that the method is sensitive and provides a relatively long time frame for the retrospective detection of SM exposure.

  13. Freeze drying for gas chromatography stationary phase deposition

    DOEpatents

    Sylwester, Alan P.

    2007-01-02

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

  14. Chromatographic properties PLOT multicapillary columns.

    PubMed

    Nikolaeva, O A; Patrushev, Y V; Sidelnikov, V N

    2017-03-10

    Multicapillary columns (MCCs) for gas chromatography make it possible to perform high-speed analysis of the mixtures of gaseous and volatile substances at a relatively large amount of the loaded sample. The study was performed using PLOT MCCs for gas-solid chromatography (GSC) with different stationary phases (SP) based on alumina, silica and poly-(1-trimethylsilyl-1-propyne) (PTMSP) polymer as well as porous polymers divinylbenzene-styrene (DVB-St), divinylbenzene-vinylimidazole (DVB-VIm) and divinylbenzene-ethylene glycol dimethacrylate (DVB-EGD). These MCCs have the efficiency of 4000-10000 theoretical plates per meter (TP/m) and at a column length of 25-30cm can separate within 10-20s multicomponent mixtures of substances belonging to different classes of chemical compounds. The sample amount not overloading the column is 0.03-1μg and depends on the features of a porous layer. Examples of separations on some of the studied columns are considered.

  15. Chromatographic Separation of Glucose and Fructose

    NASA Astrophysics Data System (ADS)

    Kuptsevich, Yu E.; Larionov, Oleg G.; Stal'naya, I. D.; Nakhapetyan, L. A.; Pronin, A. Ya

    1987-03-01

    The structures, mutarotation, and the physicochemical properties of glucose and fructose as well as methods for their separation are examined. Their chromatographic separation on cation exchangers in the calcium-form is discussed in detail. A theory of the formation of complexes of carbohydrates with metal cations is described and the mechanism of the separation of glucose and fructose on cation exchangers in the calcium-form is discussed in detail. Factors influencing the chromatographic separation of glucose and fructose on sulphonic acid cation-exchange resins are also considered. The bibliography includes 138 references.

  16. Automated gas chromatography

    DOEpatents

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

    1999-01-01

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

  17. Chromatographic, Spectroscopic and Mass Spectrometric Approaches for Exploring the Habitability of Mars in 2012 and Beyond with the Curiosity Rover

    NASA Technical Reports Server (NTRS)

    Mahaffy, Paul

    2012-01-01

    The Sample Analysis at Mars (SAM) suite of instruments on the Curiosity Rover of Mars Science Laboratory Mission is designed to provide chemical and isotopic analysis of organic and inorganic volatiles for both atmospheric and solid samples. The goals of the science investigation enabled by the gas chromatograph mass spectrometer and tunable laser spectrometer instruments of SAM are to work together with the other MSL investigations is to quantitatively assess habitability through a series of chemical and geological measurements. We describe the multi-column gas chromatograph system employed on SAM and the approach to extraction and analysis of organic compounds that might be preserved in ancient martian rocks.

  18. Chromatographic determination of the differential isosteric adsorption enthalpies and differential entropies on ordered silica materials.

    PubMed

    Grajek, H; Paciura-Zadrozna, J; Witkiewicz, Z

    2008-06-13

    The adsorption properties of the ordered mesoporous siliceous materials: MCM-41C16 (denoted as C16), MCM-41C16-SH and MCM-41C16-NH(2) (known as MCMs) having different surface functionalities were studied by inverse gas chromatography to assess their suitability for adsorption of analytes from gas and liquid phases. Polar and non-polar adsorbates were employed. The differential isosteric enthalpies, -DeltaH(ads), and differential entropies, -DeltaS(ads), of adsorption of different 'molecular probes' were determined chromatographically. A mathematical link between the -DeltaH(ads), and -DeltaS(ads) magnitudes and experimental data was derived through an Antoine-type equation. The present studies have been entirely restricted to the region of low adsorbate concentration. The problem of the interrelationship between the -DeltaH(ads), and -DeltaS(ads) values, known as the 'thermodynamic compensation effect', and interpretation of chromatographic data for the adsorption of different adsorbates on the MCMs have been considered in the light of both experimental data obtained in the present studies and the data available in the literature for siliceous adsorbents with randomly ordered structures. It was shown chromatographically that there is substantial parallelism between the magnitudes of the differential isosteric enthalpy and differential entropy for some 'molecular probes' chromatographed on C16 and its derivatives. Complementary information was obtained by atomic-force microscopy (AFM), X-ray photoelectron spectroscopy and X-ray diffraction (XRD) spectroscopy.

  19. Numerical Simulation of an Optical Chromatographic Separator

    DTIC Science & Technology

    2009-02-02

    its close relative, Bacillus thuringiensis ," Anal. Chem. 78, 3221-3225 (2006). 10. S. J. Hart, A. Terray, K. L. Kuhn, J. Arnold, and T. A. Leski...Terray, T. A. Leski, J. Arnold, and R. Stroud, "Discovery of a significant optical chromatographic difference between spores of Bacillus anthracis and

  20. Nano-fabricated size exclusion chromatograph

    NASA Technical Reports Server (NTRS)

    Svehla, D.; Feldman, S.; Feldman, J.; Grunthaner, F.; Shakkottai, P.; dle Castillo, L.; White, V.

    2002-01-01

    This poster describes the development of a nano-fabricated size exclusion chromatograph (nSEC) based on the principle that molecules traveling through a microcolumn containing nano-fabricated features will have characteristics elution times that directly correlate to molecular weight.

  1. Functional chromatographic technique for natural product isolation†

    PubMed Central

    Lau, Eric C.; Mason, Damian J.; Eichhorst, Nicole; Engelder, Pearce; Mesa, Celestina; Kithsiri Wijeratne, E. M.; Gunaherath, G. M. Kamal B.; Leslie Gunatilaka, A. A.

    2015-01-01

    Natural product discovery arises through a unique interplay between chromatographic purification and biological assays. Currently, most techniques used for natural product purification deliver leads without a defined biological action. We now describe a technique, referred to herein as functional chromatography, that deploys biological affinity as the matrix for compound isolation. PMID:25588099

  2. Method to fabricate silicon chromatographic column comprising fluid ports

    DOEpatents

    Manginell, Ronald P.; Frye-Mason, Gregory C.; Heller, Edwin J.; Adkins, Douglas R.

    2004-03-02

    A new method for fabricating a silicon chromatographic column comprising through-substrate fluid ports has been developed. This new method enables the fabrication of multi-layer interconnected stacks of silicon chromatographic columns.

  3. Method for the chromatographic separation of cations from aqueous samples

    DOEpatents

    Horwitz, E.P.; Chiarizia, R.; Dietz, M.L.

    1997-07-29

    An extraction chromatographic material is described for extracting metal cations from a liquid stream. The extraction chromatographic material is prepared by adsorbing a diesterified methanediphosphonic acid on an inert particulate support. 7 figs.

  4. Tadpole toxicity prediction using chromatographic systems.

    PubMed

    Fernández-Pumarega, Alejandro; Amézqueta, Susana; Fuguet, Elisabet; Rosés, Martí

    2015-10-30

    Toxicity has been emulated in tadpole species through chromatographic systems. The parameter studied to evaluate the non-specific toxicity of a compound is the narcosis concentration (Cnar), which is defined as the concentration needed for the immobilization of the organism. Because experimental investigation with animals is lengthy, costly, technically difficult, and ethically questionable, there is a great interest in developing surrogate physicochemical systems able to emulate biological systems to obtain the same information in a faster, more economic, and easier manner. In order to see which chromatographic systems would be able to emulate tadpole narcosis, both, tadpole narcosis data and data in several chromatographic and electrophoretic systems, were fitted to a linear solvation energy relationship (LSER) model. Thus, by comparison of the models it was possible to see which of the chromatographic systems were more similar to the biological one. The physicochemical systems that best emulate tadpole narcosis were an HPLC system based on an immobilized artificial membrane (IAM) column, and two micellar electrokinetic chromatography (MEKC) systems based on sodium taurocholate (STC) and a mixture of sodium dodecylsulphate (SDS) and Brij 35 as surfactants. A system based on a RP18 HPLC column also was selected for comparison because it is a common column in most analytical laboratories. To establish the models, a set of compounds with known Cnar values were analyzed in the chromatographic, and electrophoretic selected systems and, then, the retention factor (k) was correlated to the concentration of narcosis. Statistics showed that the system based on STC micelles was the best to emulate toxicity in tadpoles. The robustness and predictive ability of the developed models were validated.

  5. Gas chromatographic determination of triclopyr in fruits and vegetables.

    PubMed

    Ting, K C; Lee, C S

    1995-01-20

    This research was comprised of two parts: quantitative analyses, and confirmatory test. In the quantitative analyses, five classes of fruits and vegetables comprising 10 individual commodities were fortified with triclopyr herbicide at 0.4 and 0.8 ppm level. Triclopyr was extracted from the matrices and derivatized separately to 2-chloroethylene ester with 2-chloroethanol-BCl3 and methyl ester with diazomethane. The esters were then quantitated by GC-ECD and GC-NPD. The GC-ECD recoveries for 2-chloroethylene ester were 100.0% and 100.7% at 0.4 ppm and 0.8 ppm fortification levels, respectively, whereas methyl ester recovery was 103.9% at 0.4 ppm fortification level. Similarly, the GC-NPD recoveries for 2-chloroethylene ester were 99.0% and 97.9% at 0.4 ppm and 0.8 ppm fortification levels respectively, whereas methyl ester recovery was 102.0% at 0.4 ppm fortification level. In the confirmatory test, the 2-chloroethylene ester was introduced into a GC-ion trap. The EI mass spectrum was then interpreted based on the criteria of molecular ion, isotopes, base ion, characteristic ions and the nitrogen rule. Compared to existing methods, this method has reduced partition solvents to nearly one-tenth. In addition, this method proved to be simple, fast, safe and accurate.

  6. Gas chromatographic determination of pentachlorophenol in human blood and urine

    SciTech Connect

    Atuma, S.S.; Okor, D.I.

    1985-09-01

    The extraction, identification and quantification of pentachlorophenol (PCP) in human blood and urine are of great importance for monitoring human exposure to this environmental chemical. Although reports abound in the literature on PCP residues, toxicity and environmental fate, there is hardly any information on its existence in the developing tropical countries, particularly in Nigeria. There is therefore the need to survey the status of PCP in Nigerian environment with a view to establishing the potential health hazards resulting from its bioaccumulation. This paper reports a preliminary survey of the residue levels of PCP in human blood and urine of the general population in Bendel State of Nigeria.

  7. GAS CHROMATOGRAPHIC RETENTION PARAMETERS DATABASE FOR REFRIGERANT MIXTURE COMPOSITION MANAGEMENT

    EPA Science Inventory

    Composition management of mixed refrigerant systems is a challenging problem in the laboratory, manufacturing facilities, and large refrigeration machinery. Ths issue of composition management is especially critical for the maintenance of machinery that utilizes zeotropic mixture...

  8. Chromatographic fingerprint analysis of Pycnogenol dietary supplements.

    PubMed

    Chen, Pei; Song, Fenhong; Lin, Long-Ze

    2009-01-01

    The bark of maritime pine (Pinus pinaster Aiton) has been widely used as a remedy for various degenerative diseases. A standard high-performance liquid chromatographic (HPLC) procedure for Pycnogenol analysis is a method specified in the United States Pharmacopeia (USP) monograph, which requires measurement of peak areas and identification of four components of the extract: caffeic acid, catechin, ferulic acid, and taxifolin. In this study, a fingerprint analysis using an HPLC method based on the USP monograph has been developed to provide additional qualitative information for the analysis of Pycnogenol-containing dietary supplements (PDS). Twelve commercially available PDS samples were purchased and analyzed along with a standard Pycnogenol extract. Their chromatographic fingerprints were analyzed using principal component analysis. The results showed that two of the samples were not consistent with the standard reference Pycnogenol extract. One contained other active ingredients in addition to Pycnogenol, and the other may have resulted from a quality control issue in manufacturing.

  9. Chromatographic purification of highly active yeast ribosomes.

    PubMed

    Meskauskas, Arturas; Leshin, Jonathan A; Dinman, Jonathan D

    2011-10-24

    Eukaryotic ribosomes are much more labile as compared to their eubacterial and archael counterparts, thus posing a significant challenge to researchers. Particularly troublesome is the fact that lysis of cells releases a large number of proteases and nucleases which can degrade ribosomes. Thus, it is important to separate ribosomes from these enzymes as quickly as possible. Unfortunately, conventional differential ultracentrifugation methods leaves ribosomes exposed to these enzymes for unacceptably long periods of time, impacting their structural integrity and functionality. To address this problem, we utilize a chromatographic method using a cysteine charged Sulfolink resin. This simple and rapid application significantly reduces co-purifying proteolytic and nucleolytic activities, producing high yields of intact, highly biochemically active yeast ribosomes. We suggest that this method should also be applicable to mammalian ribosomes. The simplicity of the method, and the enhanced purity and activity of chromatographically purified ribosome represents a significant technical advancement for the study of eukaryotic ribosomes.

  10. Gas chromatography.

    PubMed

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

    1998-06-15

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

  11. Nano-fabricated size exclusion chromatograph

    NASA Technical Reports Server (NTRS)

    Svehla, D.; Feldman, S.; Feldman, J.; Grunthaner, F.; Shakkottai, P.; Castillo, L. del; White, V.

    2002-01-01

    This paper describes the development of a nano-fabricated size exclusion chromatograph (nSEC) based on the principle that molecules traveling through amicrocolumn containing nano-fabricated features will have characteristic elution times that directly correlate to molecular weight. Compared to conventional size exclusion chromatography, the nSEC offers greater control over the size exclusion process; mass fabrication; integration of the separation column with associated valves, pumps, and detectors; and dramatic reductions in instrument mass and power requirements.

  12. MULTISPECTRAL IDENTIFICATION OF POTENTIALLY HAZARDOUS BYPRODUCTS OF OZONATION AND CHLORINATION - PART I: STUDIES OF CHROMATOGRAPHIC AND SPECTROSCOPIC PROPERTIES OF MX

    EPA Science Inventory

    The gas chromatographic (GC) and Fourier transform infrared and mass spectroscopic (FT-IR and MS, respectively) properties of (Z)-2-chloro-3-(dichloromethyl)4-oxobutenoic acid (MX) (a highly mutagenic byproduct of drinking water chlorination) and several related compounds were st...

  13. Portable Gas Analyzer

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The Michromonitor M500 universal gas analyzer contains a series of miniature modules, each of which is a complete gas chromatograph, an instrument which separates a gaseous mixture into its components and measures the concentrations of each gas in the mixture. The system is manufactured by Microsensor Technology, and is used for environmental analysis, monitoring for gas leaks and chemical spills, compliance with pollution laws, etc. The technology is based on a Viking attempt to detect life on Mars. Ames/Stanford miniaturized the system and NIOSH funded further development. Three Stanford researchers commercialized the technology, which can be operated by unskilled personnel.

  14. High pressure liquid chromatographic gradient mixer

    DOEpatents

    Daughton, Christian G.; Sakaji, Richard H.

    1985-01-01

    A gradient mixer which effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum "band-broadening".

  15. High-pressure liquid chromatographic gradient mixer

    DOEpatents

    Daughton, C.G.; Sakaji, R.H.

    1982-09-08

    A gradient mixer effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum band-broadening.

  16. Chromatographic enrichment and enantiomer separation of axially chiral polybrominated biphenyls in a technical mixture.

    PubMed

    Berger, Urs; Vetter, Walter; Götsch, Arntraut; Kallenborn, Roland

    2002-10-11

    The separation properties of different chromatographic methods regarding the enantioselective separation of axially chiral (atropisomeric) polybrominated biphenyls (PBB) were studied. For this purpose, the technical hexabromobiphenyl product Firemaster BP-6 was characterised by gas-chromatography coupled to electron capture detection (GC/ECD) and electron-capture negative ion mass spectrometry (GC/ECNI-MS) as well as by liquid chromatographic fractionating on active carbon and celite. Twelve individual PBBs including potential atropisomeric PBBs were isolated from Firemaster BP-6 by reversed-phase high-performance liquid chromatography (HPLC) on three serially coupled octadecylsilane columns. Six of the 12 isolated PBBs (three tri-ortho and di-ortho substituted PBBs, respectively) were separated into atropisomers on a HPLC column containing permethylated beta-cyclodextrin on silica. Moreover, the temperature dependency of the enantiomer separations is discussed. Gas chromatographic enantiomer separation of PBBs is a very demanding task due to high elution temperatures. However, the atropisomers of one tri-ortho substituted PBB congener (PBB 149) could be resolved on a column coated with randomly modified heptakis(6-O-tert.-butyldimethylsilyl-2,3-di-O-methyl)-beta-cyclodextrin in OV 1701.

  17. Packed multi-channels for parallel chromatographic separations in microchips.

    PubMed

    Nagy, Andrea; Gaspar, Attila

    2013-08-23

    Here we report on a simple method to fabricate microfluidic chip incorporating multi-channel systems packed by conventional chromatographic particles without the use of frits. The retaining effectivities of different bottlenecks created in the channels were studied. For the parallel multi-channel chromatographic separations several channel patterns were designed. The obtained multipackings were applied for parallel separations of dyes. The implementation of several chromatographic separation units in microscopic size makes possible faster and high throughput separations.

  18. A review of the extraction and chromatographic determination methods for the analysis of parabens.

    PubMed

    Piao, Chunying; Chen, Ligang; Wang, Yu

    2014-10-15

    Parabens are a family of most widely used antimicrobial preservatives in food ingredients, cosmetic consumer products and pharmaceutical preparations. But several recent studies have cautioned that exposure to parabens may have more harmful consequences on animal and human health than what we realized previously, which made the analysis of parabens necessary. In this paper, we reviewed main sample preparation methods and chromatographic analysis methods proposed in formerly published works dealing with the analysis of parabens in different matrices. The sample preparation methods included ultrasonic assisted extraction, supercritical fluid extraction, pressurized liquid extraction, solid phase extraction, solid phase microextraction, liquid phase microextraction, dispersive liquid-liquid microextraction, stir bar sorptive extraction and matrix solid phase dispersion. The chromatographic analysis methods involved liquid chromatography, gas chromatography, and capillary electrophoresis.

  19. Liquid chromatographic determination of melamine in beverages.

    PubMed

    Ishiwata, H; Inoue, T; Yamazaki, T; Yoshihira, K

    1987-01-01

    A liquid chromatographic method is described for the determination of melamine in beverages. Melamine is separated by column chromatography using cation and anion exchange resin and determined by ion-pair liquid chromatography using an ODS column and a mixture of acetonitrile and 0.05M phosphate buffer (pH 3.0) containing 0.005M sodium 1-laurylsulfate (1 + 4, v/v) as mobile phase. Recoveries of melamine ranged between 90.3 +/- 7.8 and 102.1 +/- 5.6% at levels of 0.6 to 2.4 ppm in 4 kinds of beverages. The quantitation limit was 2.5 micrograms melamine in 50 mL beverage. The method was applied to the migration test of melamine from melamine-formaldehyde resin products to the beverages.

  20. Interface for liquid chromatograph-mass spectrometer

    DOEpatents

    Andresen, B.D.; Fought, E.R.

    1989-09-19

    A moving belt interface is described 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. 8 figs.

  1. Interface for liquid chromatograph-mass spectrometer

    DOEpatents

    Andresen, Brian D.; Fought, Eric R.

    1989-01-01

    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.

  2. Authenticity analysis of pear juice employing chromatographic fingerprinting.

    PubMed

    Willems, Jamie L; Low, Nicholas H

    2014-12-03

    Pear juice is predominately composed of carbohydrates/polyols (>95% of the total soluble solids), making it susceptible to adulteration by the addition of less expensive commercial sweeteners. In this research, the major carbohydrate and polyol (fructose, glucose, sucrose, and sorbitol) content of 32 pure pear juices representing five world producing regions and three years of production was determined. Additionally, methods employing oligosaccharide profiling to detect the debasing of these samples with four commercial sweeteners (HFCS 55 and 90, TIS, and HIS) were developed using capillary gas chromatography with flame ionization detection (CGC-FID) and high-performance liquid chromatography with pulsed amperometric detection (HPAE-PAD). Detection limits for the four commercial sweeteners ranged from 0.5 to 5.0% (v/v). In addition, the developed CGC-FID method could be used to (a) detect the addition of pear to apple juice via arbutin detection and (b) determine if a pear juice was produced using enzymatic liquefaction via the presence of O-β-d-glucopyranosyl-(1→4)-d-glucopyranose (cellobiose), all within a single chromatographic analysis.

  3. Comparison of three advanced chromatographic techniques for cannabis identification.

    PubMed

    Debruyne, D; Albessard, F; Bigot, M C; Moulin, M

    1994-01-01

    The development of chromatography technology, with the increasing availability of easier-to-use mass spectrometers combined with gas chromatography (GC), the use of diode-array or programmable variable-wavelength ultraviolet absorption detectors in conjunction with high-performance liquid chromatography (HPLC), and the availability of scanners capable of reading thin-layer chromatography (TLC) plates in the ultraviolet and visible regions, has made for easier, quicker and more positive identification of cannabis samples that standard analytical laboratories are occasionally required to undertake in the effort to combat drug addiction. At laboratories that do not possess the technique of GC combined with mass spectrometry, which provides an irrefutable identification, the following procedure involving HPLC or TLC techniques may be used: identification of the chromatographic peaks corresponding to each of the three main cannabis constituents-cannabidiol (CBD), delta-9-tetrahydrocannabinol (delta-9-THC) and cannabinol (CBN)-by comparison with published data in conjunction with a specific absorption spectrum for each of those constituents obtained between 200 and 300 nm. The collection of the fractions corresponding to the three major cannabinoids at the HPLC system outlet and the cross-checking of their identity in the GC process with flame ionization detection can further corroborate the identification and minimize possible errors due to interference.

  4. Novel reduced pressure-balance syringe for chromatographic analysis.

    PubMed

    Windom, Bret C; Bruno, Thomas J

    2010-11-19

    When withdrawing a fluid sample (for additional chromatographic analyses) from an apparatus operated at a reduced pressure, a typical syringe proves to be ineffective (even if it is equipped with a gas tight plunger). It simply does not create enough pressure differential to remove a fluid sample from a reduced pressure environment. We encountered such a situation as part of efforts to extend the operation of the advanced distillation curve protocol to reduced pressures. The problem was solved by the development of a pressure balance syringe that allows reliable and precise sampling from an apparatus operating at sub-ambient pressures. This new device uses an external vacuum source to evacuate a syringe barrel, allowing a user to withdraw fluid samples from environments with pressures as low as 0.5kPa. To demonstrate the operation of the newly developed device, distillate analyses were performed on two fluids at low pressure: a predefined validation mixture, and a commercial soy based biodiesel fuel. The pressure balance syringe was used successfully for sampling in both cases. The use of the pressure balance syringe is not limited to reduced pressure distillations; indeed it can be used for a variety of applications in which chemical/compositional analyses are desired on a fluid contained in a reduced pressure environment.

  5. High-capacity pressurized continuous chromatograph

    SciTech Connect

    Begovich, J.M.; Byers, C.H.; Sisson, W.G.

    1983-01-01

    Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. The feed material is continuously introduced at a stationary point at the top of the bed, and eluent is allowed to flow everwhere else around the annulus. The rotation of the sorbent bed causes the separation components to appear as helical bands, each of which has a characteristic, stationary exit point; hence the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6-m-long device with a 12.7-mm-wide annulus. The effects of annulus width and diameter have been studied using the same device with annulus widths up to 114.3 mm. With this largest width, approximately 96% of the area available within the outer cylinder is devoted to the rotating sorbent bed. Further annulus-width studies have been pursued on units with 89- and 445-mm diameters. These geometric extensions to the basic concept allow extremely large capacity increases with minimal loss in separation and no increase in chromatograph diameter. The effects associated with increased feed concentration have also been studied. In this effort as well as in the annulus-width program, the separation of copper, nickel, and cobalt components from a carbonate solution was studied in detail. The nickel and cobalt components are found in the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. Nominally 50-..mu..m0-diam Dowex 50W-X8 cation exchange resin was used as the bed material. The nickel concentration of the feed was varied tenfold, from 136.1 to approximately 1400 meq/L. The combined effects of the bed loading and annulus width were studied and compared with nonlinear theory.

  6. High-capacity pressurized continuous chromatograph

    SciTech Connect

    Begovich, J.M.; Byers, C.H.; Sisson, W.G.

    1983-01-01

    Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. The feed material is continuously introduced at a stationary point at the top of the bed, and eluent is allowed to flow everywhere else around the annulus. The rotation of the sorbent bed causes the separated components to appear as helical bands, each of which has a characteristic, stationary exit point; hence the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6-m-long device with a 12.7-mm-wide annulus. The effects of annulus width and diameter have been studied using the same device with annulus widths up to 114.3 mm. With this largest width, approximately 96% of the area available within the outer cylinder is devoted to the rotating sorbent bed. Further annulus-width studies have been pursued on units with 89- and 445-mm diameters. These geometric extensions to the basic concept allow extremely large capacity increases with minimal loss in separation and no increase in chromatograph diameter. The effects associated with increased feed concentration have also been studied. In this effort as well as in the annulus-width program, the separation of copper, nickel, and cobalt components from a carbonate solution was studied in detail. The nickel and cobalt components are found in the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. Nominally 50-..mu..m-diam Dowex 50W-X8 cation exchange resin was used as the bed material. The nickel concentration of the feed was varied tenfold, from 136.1 to approximately 1400 meq/L. The combined effects of the bed loading and annulus width were studied and compared with nonlinear theory. 17 references, 9 figures, 1 table.

  7. High-capacity pressurized continuous chromatograph

    SciTech Connect

    Begovich, J.M.; Byers, C.H.; Sisson, W.G.

    1983-01-01

    Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. The feed material is continuously introduced at a stationary point at the top of the bed, and eluent is allowed to flow everywhere else around the annulus. The rotation of the sorbent bed causes the separated components to appear as helical bands, each of which has a characteristic, stationary exit point; hence the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6m-long device with a 12.7-mm-wide annulus. The effects of annulus width and diameter have been studied using the same device with annulus widths up to 114.3 mm. With this largest width, approximately 96% of the area available within the outer cylinder is devoted to the rotating sorbent bed. Further annulus-width studies have been pursued on units with 89- and 445-mm diameters. These geometric extensions to the basic concept allow extremely large capacity increases with minimal loss in separation and no increase in chromatograph diameter. The effects associated with increased feed concentration have also been studied. In this effort as well as in the annulus-width program, the separation of copper, nickel, and cobalt components from a carbonate solution was studied in detail. The nickel and cobalt components are found in the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. Nominally 50-..mu..m-diam Dowex 50W-X8 cation exchange resin was used as the bed material. The nickel concentration of the feed was varied tenfold, from 136.1 to approximately 1400 meq/L. The combined effects of the bed loading and annulus width were studied and compared with nonlinear theory. 9 figures, 1 table.

  8. Authentication of geographical origin of palm oil by chromatographic fingerprinting of triacylglycerols and partial least square-discriminant analysis.

    PubMed

    Ruiz-Samblás, Cristina; Arrebola-Pascual, Cristina; Tres, Alba; van Ruth, Saskia; Cuadros-Rodríguez, Luis

    2013-11-15

    Main goals of the present work were to develop authentication models based on liquid and gas chromatographic fingerprinting of triacylglycerols (TAGs) from palm oil of different geographical origins in order to compare them. For this purpose, a set of palm oil samples were collected from different continents: South eastern Asia, Africa and South America. For the analysis of the information in these fingerprint profiles, a pattern recognition technique such as partial least square discriminant analysis (PLS-DA) was applied to discriminate the geographical origin of these oils, at continent level. The liquid chromatography, coupled to a charged aerosol detector, (HPLC-CAD) TAGs separation was optimized in terms of mobile phase composition and by means of a solid silica core column. The gas chromatographic method with a mass spectrometer was applied under high temperature (HTGC-MS) in order to analyze the intact TAGs. Satisfactory chromatographic resolution within a short total analysis time was achieved with both chromatographic approaches and without any prior sample treatment. The rates of successful in prediction of the geographical origin of the 85 samples varied between 70% and 100%.

  9. Band target entropy minimization for retrieving the information of individual components from overlapping chromatographic data.

    PubMed

    Xia, Zhenzhen; Liu, Yan; Cai, Wensheng; Shao, Xueguang

    2015-09-11

    Band target entropy minimization (BTEM) is a self-modeling curve resolution (SMCR) approach relying on non-negative criterion and minimization of Shannon entropy. In this study, BTEM algorithm was applied to retrieving the information of individual components from overlapping gas chromatography-mass spectrometry (GC-MS) data. The algorithm starts with dividing the whole data into bands along the retention time. In each band, singular value decomposition (SVD) is used to decompose the data into scores and loadings. Because the pure chromatographic signal possesses the lowest Shannon entropy, the chromatographic signal of each component can be constructed by optimizing the combination of the loadings with minimal Shannon entropy under non-negative criterion. To show the efficiency of the algorithm, a simulated four-component overlapping GC-MS data and an experimental GC-MS data of 18 organophosphorus pesticide mixture are investigated. The results show that both the chromatographic profiles and mass spectra of the components can be successfully extracted from the overlapping signals.

  10. Automated gas chromatography

    DOEpatents

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

    1999-07-13

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

  11. Evaluation of practical chromatographic procedures for identification of clinical isolates of mycobacteria.

    PubMed Central

    Luquin, M; Ausina, V; López Calahorra, F; Belda, F; García Barceló, M; Celma, C; Prats, G

    1991-01-01

    After experimental conditions were established, 366 strains of mycobacteria belonging to 23 different species were studied for fatty acids, secondary alcohols, and mycolic acid cleavage products by capillary gas-liquid chromatography. Additionally, the mycolic acid pattern was studied by thin-layer chromatography. Capillary gas-liquid chromatography allowed direct identification of the following Mycobacterium spp.: M. kansasii, M. marinum, M. szulgai, M. xenopi, M. malmoense, and M. gordonae. The patterns of mycolic acid methyl esters recorded for the test strains of M. chelonae and M. agri may be of value in the identification of these species. Moreover, the combined use of the two chromatographic techniques provided precise identification of the M. tuberculosis complex, M. simiae, M. fallax, M. triviale, and M. chelonae-like organisms. A minimal set of biochemical tests is usually required to obtain identification to the species level when chromatographic procedures alone are not sufficient. Under the reported experimental conditions, thin-layer chromatography and capillary gas-liquid chromatography are rapid and very useful techniques for the identification of mycobacteria. Images PMID:1993746

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

    ERIC Educational Resources Information Center

    Gallaher, T. N.; And Others

    1977-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Welz, E. A., Jr.

    1967-01-01

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

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

    ERIC Educational Resources Information Center

    Jaffe, Dan; Herndon, Scott

    1995-01-01

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

  15. Chemometric approach for development, optimization, and validation of different chromatographic methods for separation of opium alkaloids.

    PubMed

    Acevska, J; Stefkov, G; Petkovska, R; Kulevanova, S; Dimitrovska, A

    2012-05-01

    The excessive and continuously growing interest in the simultaneous determination of poppy alkaloids imposes the development and optimization of convenient high-throughput methods for the assessment of the qualitative and quantitative profile of alkaloids in poppy straw. Systematic optimization of two chromatographic methods (gas chromatography (GC)/flame ionization detector (FID)/mass spectrometry (MS) and reversed-phase (RP)-high-performance liquid chromatography (HPLC)/diode array detector (DAD)) for the separation of alkaloids from Papaver somniferum L. (Papaveraceae) was carried out. The effects of various conditions on the predefined chromatographic descriptors were investigated using chemometrics. A full factorial linear design of experiments for determining the relationship between chromatographic conditions and the retention behavior of the analytes was used. Central composite circumscribed design was utilized for the final method optimization. By conducting the optimization of the methods in very rational manner, a great deal of excessive and unproductive laboratory research work was avoided. The developed chromatographic methods were validated and compared in line with the resolving power, sensitivity, accuracy, speed, cost, ecological aspects, and compatibility with the poppy straw extraction procedure. The separation of the opium alkaloids using the GC/FID/MS method was achieved within 10 min, avoiding any derivatization step. This method has a stronger resolving power, shorter analysis time, better cost/effectiveness factor than the RP-HPLC/DAD method and is in line with the "green trend" of the analysis. The RP-HPLC/DAD method on the other hand displayed better sensitivity for all tested alkaloids. The proposed methods provide both fast screening and an accurate content assessment of the six alkaloids in the poppy samples obtained from the selection program of Papaver strains.

  16. High-speed counter-current chromatographic isolation of ricinine, an insecticide from Ricinus communis.

    PubMed

    Cazal, Cristiane de Melo; Batalhão, Jaqueline Raquel; Domingues, Vanessa de Cássia; Bueno, Odair Corrêa; Filho, Edson Rodrigues; Forim, Moacir R; da Silva, Maria Fátima G Fernandes; Vieira, Paulo Cezar; Fernandes, João Batista

    2009-05-08

    The alkaloid ricinine, an insecticide for leaf-cutting ant (Atta sexdens rubropilosa), was obtained from Ricinus communis. A two-phase solvent system composed of CH(2)Cl(2)/EtOH/H(2)O (93:35:72, v/v/v) was used for high-speed counter-current chromatographic (HSCCC) isolation of ricinine in high yield and with over 96% purity, as determined by liquid and gas chromatography-mass spectrometry (LC-MS and GC-MS). Identification of ricinine was performed by comparison of (1)H NMR, (13)C NMR and LC-MS/MS data.

  17. Chromatographic Separations of Enantiomers and Underivatized Oligosaccharides

    SciTech Connect

    Liu, Ying

    2004-01-01

    My graduate research has focused on separation science and bioanalytical analysis, which emphasized in method development. It includes three major areas: enantiomeric separations using high performance liquid chromatography (HPLC), Super/subcritical fluid chromatography (SFC), and capillary electrophoresis (CE); drug-protein binding behavior studies using CE; and carbohydrate analysis using liquid chromatograph-electrospray ionization mass spectrometry (LC-ESI-MS). Enantiomeric separations continue to be extremely important in the pharmaceutical industry. An in-depth evaluation of the enantiomeric separation capabilities of macrocyclic glycopeptides CSPs with SFC mobile phases was investigated using a set of over 100 chiral compounds. It was found that the macrocyclic based CSPs were able to separate enantiomers of various compounds with different polarities and functionalities. Seventy percent of all separations were achieved in less than 4 min due to the high flow rate (4.0 ml/min) that can be used in SFC. Drug-protein binding is an important process in determining the activity and fate of a drug once it enters the body. Two drug/protein systems have been studied using frontal analysis CE method. More sensitive fluorescence detection was introduced in this assay, which overcame the problem of low sensitivity that is common when using UV detection for drug-protein studies. In addition, the first usage of an argon ion laser with 257 nm beam coupled with CCD camera as a frontal analysis detection method enabled the simultaneous observation of drug fluorescence as well as the protein fluorescence. LC-ESI-MS was used for the separation and characterization of underivatized oligosaccharide mixtures. With the limits of detection as low as 50 picograms, all individual components of oligosaccharide mixtures (up to 11 glucose-units long) were baseline resolved on a Cyclobond I 2000 column and detected using ESI-MS. This system is characterized by high chromatographic

  18. Noble gas fractionation during subsurface gas migration

    NASA Astrophysics Data System (ADS)

    Sathaye, Kiran J.; Larson, Toti E.; Hesse, Marc A.

    2016-09-01

    Environmental monitoring of shale gas production and geological carbon dioxide (CO2) storage requires identification of subsurface gas sources. Noble gases provide a powerful tool to distinguish different sources if the modifications of the gas composition during transport can be accounted for. Despite the recognition of compositional changes due to gas migration in the subsurface, the interpretation of geochemical data relies largely on zero-dimensional mixing and fractionation models. Here we present two-phase flow column experiments that demonstrate these changes. Water containing a dissolved noble gas is displaced by gas comprised of CO2 and argon. We observe a characteristic pattern of initial co-enrichment of noble gases from both phases in banks at the gas front, followed by a depletion of the dissolved noble gas. The enrichment of the co-injected noble gas is due to the dissolution of the more soluble major gas component, while the enrichment of the dissolved noble gas is due to stripping from the groundwater. These processes amount to chromatographic separations that occur during two-phase flow and can be predicted by the theory of gas injection. This theory provides a mechanistic basis for noble gas fractionation during gas migration and improves our ability to identify subsurface gas sources after post-genetic modification. Finally, we show that compositional changes due to two-phase flow can qualitatively explain the spatial compositional trends observed within the Bravo Dome natural CO2 reservoir and some regional compositional trends observed in drinking water wells overlying the Marcellus and Barnett shale regions. In both cases, only the migration of a gas with constant source composition is required, rather than multi-stage mixing and fractionation models previously proposed.

  19. [Combination similarity algorithm on chromatographic fingerprints].

    PubMed

    Zhan, Xueyan; Shi, Xinyuan; Duan, Tianxuan; Li, Lei; Qiao, Yanjiang

    2010-11-01

    The similarity of chromatographic fingerprints is one of the effective approaches evaluating the quality stability of Chinese medicine, and the cosine of angle plays an important role in the application of similarity. However, the cosine approach is insensitive to the data difference when the distribution range of the data sets is wide. When the data proportion of the reference sample and the test sample is greatly different, it confirms that the sensitivity of the cosine to the differences of the peaks owned by both the reference sample and the test sample differs from the peaks owned only by the reference sample or the test sample in this study. The method considers the peaks owned by one sample in addition to peaks owned by both samples, and determines their own appropriate weigh targeting for the maximal homostasis value of proportion among the peaks of all of Smilax glabra Roxb. samples. The method based on sample data could reflect the difference in the chemical composition area ratio between the reference sample and test samples sensitively, and measures the similarity among the nine Smilax glabra Roxb. samples, which is a new similarity algorithm for evaluating the quality stability of herbal medicines.

  20. Tailing of chromatographic peaks in GC-MS caused by interaction of halogenated solvents with the ion source.

    PubMed

    Brocks, Jochen J; Hope, Janet M

    2014-07-01

    The injection of analytes into a gas chromatography-mass spectrometry (GC-MS) system using dichloromethane (DCM) as solvent led to gradual deterioration of chromatographic signals, with significant tailing and loss of sensitivity for C17+ hydrocarbons. The injector, gas chromatograph and transfer line were excluded as causes. Normal peak shape could only be restored by the insertion of a cleaned MS ion source. To elucidate potential surficial contaminants, the ion source was heated from 260 to 320°C, leading to the release of increasing concentrations of ferrous chloride [FeCl2(g)]. The ferrous chloride probably formed through the decomposition of DCM on metal surfaces in the ion source. We posit that the tailing was caused by the adsorption of analytes to sub-µm layers of FeCl2 at crystal defect sites in the metal, followed by the slow release of molecules back into the gas phase. There are at least two other cases in the literature in which tailing is specifically associated with the use of halogenated solvents. However, it is possible that the problem is relatively common, albeit rarely diagnosed and reported. The tailing of chromatographic peaks caused by the formation of ferrous chloride in the mass spectrometer can be diagnosed by scanning the MS background signal for the diagnostic isotopic pattern of FeCl2(+). The problem is easily solved by cleaning the MS ion source and avoiding halogenated solvents.

  1. CHROMATOGRAPHIC AND MASS SPECTRAL STUDIES OF PERFLUOROOCTANESULFONATE AND THREE PERFLUOROOCTANESULFONAMIDES

    EPA Science Inventory

    The chromatographic and mass spectral characteristics of perfluorooctanesulfonate (PFOS) and three nitrogen-substituted perfluorooctanesulfonamides have been obtained. A methyl/phenol mixed phase fused silica capillary column was used for GC analysis, while a C18 reversed phase ...

  2. Method for liquid chromatographic extraction of strontium from acid solutions

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1992-01-01

    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. Quantifying process tradeoffs in the operation of chromatographic sequences.

    PubMed

    Ngiam, Sheau-Huey; Bracewell, Daniel G; Zhou, Yuhong; Titchener-Hooker, Nigel J

    2003-01-01

    A method for the rapid representation of key process tradeoffs that need to be made during the analysis of chromatographic sequences has been proposed. It involves the construction of fractionation and maximum purification factor versus yield diagrams, which can be completed easily on the basis of chromatographic data. The output of the framework developed reflects the degree of tradeoff between levels of yield and purity and provides a fast and precise prediction of the sample fraction collection strategy needed to meet a desired process specification. The usefulness of this approach for the purposes of product purification and contaminant removal in a single chromatographic step has been successfully demonstrated in an earlier paper and it is now extended by application to a chromatographic sequence: the separation of a hypothetical three-component protein system by hydrophobic interaction chromatography (HIC) followed by size exclusion chromatography (SEC). The HIC operation has a strong impact upon the subsequent SEC step. The studies show how the analysis of performance in such a chromatographic sequence can be carried out easily and in a straightforward fashion using the fractionation diagram approach. The methodology proposed serves as a useful tool for identifying the process tradeoffs that must be made during operation of a sequence of chromatographic steps and indicates the impact on further processing of the cut-point decisions that are made.

  4. Gas Chromatic Mass Spectrometer

    NASA Technical Reports Server (NTRS)

    Wey, Chowen

    1995-01-01

    Gas chromatograph/mass spectrometer (GC/MS) used to measure and identify combustion species present in trace concentration. Advanced extractive diagnostic method measures to parts per billion (PPB), as well as differentiates between different types of hydrocarbons. Applicable for petrochemical, waste incinerator, diesel transporation, and electric utility companies in accurately monitoring types of hydrocarbon emissions generated by fuel combustion, in order to meet stricter environmental requirements. Other potential applications include manufacturing processes requiring precise detection of toxic gaseous chemicals, biomedical applications requiring precise identification of accumulative gaseous species, and gas utility operations requiring high-sensitivity leak detection.

  5. Combined extraction-cleanup column chromatographic procedure for determination of dicofol in avian eggs

    USGS Publications Warehouse

    Krynitsky, A.J.; Stafford, C.J.; Wiemeyer, Stanley N.

    1988-01-01

    Dicofol in avian eggs was completely oxidized to dichlorobenzophenone (DCBP) when a hexane Soxhlet extraction procedure was used. This degradation did not occur with other avian tissues (muscle and liver). For this reason, a combined extraction-cleanup column chromatographic procedure, without added heat, was developed for the determination of dicofol in avian eggs. Homogenized subsamples of eggs were mixed with sodium sulfate, and the mixture was added as the top layer on a column prepacked with Florisil. The dicofol and other compounds of interest were then eluted with ethyl ether-hexane. The extracts, relatively free from lipids, were quantitated on a gas chromatograph equipped with a 63Ni electron-capture detector and a methyl silicone capillary column. Recoveries from chicken eggs, fortified with dicofol and other DDT-related compounds, averaged 96%. Analysis of eggs of eastern screech-owls, fed a meat diet containing 10 ppm technical Kelthane, showed that both dicofol and DCBP were present. Results were confirmed by gas chromatography/mass spectrometry. This method is rapid and reliable, involves a minimum of sample handling, and is well suited for high volume determination of dicofol in eggs and other avian tissues.

  6. A simple multi-scale Gaussian smoothing-based strategy for automatic chromatographic peak extraction.

    PubMed

    Fu, Hai-Yan; Guo, Jun-Wei; Yu, Yong-Jie; Li, He-Dong; Cui, Hua-Peng; Liu, Ping-Ping; Wang, Bing; Wang, Sheng; Lu, Peng

    2016-06-24

    Peak detection is a critical step in chromatographic data analysis. In the present work, we developed a multi-scale Gaussian smoothing-based strategy for accurate peak extraction. The strategy consisted of three stages: background drift correction, peak detection, and peak filtration. Background drift correction was implemented using a moving window strategy. The new peak detection method is a variant of the system used by the well-known MassSpecWavelet, i.e., chromatographic peaks are found at local maximum values under various smoothing window scales. Therefore, peaks can be detected through the ridge lines of maximum values under these window scales, and signals that are monotonously increased/decreased around the peak position could be treated as part of the peak. Instrumental noise was estimated after peak elimination, and a peak filtration strategy was performed to remove peaks with signal-to-noise ratios smaller than 3. The performance of our method was evaluated using two complex datasets. These datasets include essential oil samples for quality control obtained from gas chromatography and tobacco plant samples for metabolic profiling analysis obtained from gas chromatography coupled with mass spectrometry. Results confirmed the reasonability of the developed method.

  7. New approaches to the kinetic study of alcoholic fermentation by chromatographic techniques.

    PubMed

    Lainioti, Georgia Ch; Karaiskakis, George

    2013-09-01

    The kinetics of the fermentation process has gained increasing interest, not only in the scientific community, but in the industrial world as well. Information concerning the improvement of batch fermentation performance may potentially be valuable for the designing of scale-up processes. Intensive studies have been conducted with the use of various chromatographic techniques, such as conventional gas chromatography, reversed-flow gas chromatography (RFGC), high-performance liquid chromatography, field-flow fractionation and others. In the present study, specific focus is placed on the employment of RFGC, a method that can successfully be applied for the determination of physicochemical quantities, such as reaction rate constants and activation energies, at each phase of the alcoholic fermentation. In contrast to conventional chromatographic techniques, RFGC can lead to substantial information referring to the evaluation of fermentation kinetics at any time of the process. Moreover, gravitational field-flow fractionation, a sub-technique of field-flow fractionation, presents the ability to monitor the proliferation of Saccharomyces cerevisiae cells through their elution profiles that can be related to the different cell growth stages. The combination of the two techniques can provide important information for kinetic study and the distinction of the growth phases of yeast cell proliferation during alcoholic fermentations conducted under different environmental conditions.

  8. Early Evolved Gas Results from the Curiosity Rover’s SAM Investigation at Gale Crater

    NASA Astrophysics Data System (ADS)

    Mahaffy, Paul R.; Franz, H.; McAdam, A.; Brunner, A.; Eigenbrode, J.; Stern, J.; SAM Science Team; MSL Science Team

    2013-10-01

    The Mars Science Laboratory Mission is designed to explore the habitability of the selected landing site at Gale crater. The Sample Analysis at Mars (SAM) instrument suite contributes to this study with a search for organic compounds, an analysis of the composition of inorganic volatiles, and measurements of the isotopic composition light elements. Both atmospheric and solid samples are analyzed. The layers in the central mound (Mt. Sharp) of Gale crater are important targets for the MSL mission. However, in situ measurements made during the past year of interesting regions close to the Bradbury landing site have revealed a diverse geology and several primary mission objectives have already been realized. SAM is located in the interior of the Curiosity rover. The MSL cameras, a laser induced breakdown spectrometer, and elemental analysis instrumentation serves to locate sampling sites and interogate candidate materials before solid sample is collected either with a drill or a scoop for delivery to SAM and the XRD instrument CheMin. SAM integrates a quadrupole mass spectrometer (QMS), a tunable laser spectrometer (TLS), and a 6-column gas chromatograph (GC) with a solid sample transport system and a gas processing and enrichment system. Results of SAM atmospheric composition analyses have already been reported (1,2). To date, multiple SAM evolved gas experiments have examined samples from fines scooped from an aeolian drift and from two drilled samples of a mudstone. Major evolved gases are H2O, CO2, O2, SO2, H2S, H2, and a number of minor species. These data help confirm the likely presence of perchlorates, the presence of phylosillicates, and both reduced and oxidized compounds evolved from the same sample. 1) P.R. Mahaffy et al., Abundance and Isotopic Composition of Gases in the Martian Atmosphere from the Curiosity Rover, Science 343, (2013). 2) C.R. Webster et al., Isotope Ratios of H, C and O in Martian Atmospheric Carbon Dioxide and Water Measured by the

  9. Separation and identification of various vulcanization agents and antioxidants in two types of rubber by chromatographic and spectrometric methods.

    PubMed

    Chauveau, S; Hamon, M; Leleu, E

    1991-11-01

    The aim of this study was to separate and identify by chromatographic and spectrometric methods, the various allergenic vulcanization agents and antioxidants used in the manufacture of industrial rubber. Specimens of elastomers were manufactured specially for this study. The specificity of the gas chromatographic method developed allows separation of all the manufacturing additives in the selected rubber types after one injection only, even though they belong to extremely varied chemical categories. The GLC method was coupled with mass spectrometry, which permitted identification of the peaks obtained and the study of the fragmentation of the 4 reference products under various conditions. Separation by TLC was performed in parallel on the same extracts, allowing rapid identification of the products tested for, and showed new spots after vulcanization.

  10. Continuous melting and ion chromatographic analyses of ice cores.

    PubMed

    Huber, T M; Schwikowski, M; Gäggele, H W

    2001-06-22

    A new method for determining concentrations of organic and inorganic ions in ice cores by continuous melting and contemporaneous ion chromatographic analyses was developed. A subcore is melted on a melting device and the meltwater produced is collected in two parallel sample loops and then analyzed simultaneously by two ion chromatographs, one for anions and one for cations. For most of the analyzed species, lower or equal blank values were achieved with the continuous melting and analysis technique compared to the conventional analysis. Comparison of the continuous melting and ion chromatographic analysis with the conventional analysis of a real ice core segment showed good agreement in concentration profiles and total amounts of ionic species. Thus, the newly developed method is well suited for ice core analysis and has the advantages of lower ice consumption, less time-consuming sample preparation and lower risk of contamination.

  11. Ion-exchange chromatographic analysis of peroxynitric acid.

    PubMed

    Nakashima, Yoichi; Ikawa, Satoshi; Tani, Atsushi; Kitano, Katsuhisa

    2016-01-29

    Ion-exchange chromatographic analysis of peroxynitric acid (O2NOOH) was performed by combining an acidic eluate with an UV-vis detector and immersing the separation column in an ice-water bath. The decomposition behavior of peroxynitric acid in the solution was also studied using this system. The fraction for the peroxynitric acid peak was collected. Ion-exchange chromatographic analysis of this fraction, after standing at room temperature for 24h, showed that the decomposition products were mainly nitrate ions with a very small amount of nitrous acid. The peroxynitric acid peak area correlated perfectly with the total amount of decomposition products. The ion-exchange chromatographic isolation allowed us to evaluate the molar extinction coefficient of peroxynitric acid precisely in a wider wavelength range than previous reports. The value decreases monotonically from 1729±26M(-1)cm(-1) at 200nm to 12.0±0.5M(-1)cm(-1) at 290nm.

  12. Mathematical functions for the representation of chromatographic peaks.

    PubMed

    Di Marco, V B; Bombi, G G

    2001-10-05

    About ninety empirical functions for the representation of chromatographic peaks have been collected and tabulated. The table, based on almost 200 references, reports for every function: (1) the most used name; (2) the most convenient equation, with the existence intervals for the adjustable parameters and for the independent variable; (3) the applications; (4) the mathematical properties, in relation to the possible applications. The list includes also equations originally proposed to represent peaks obtained in other analytical techniques (e.g. in spectroscopy), which in many instances have proved useful in representing chromatographic peaks as well; the built-in functions employed in some commercial peak-fitting software packages were included, too. Some of the most important chromatographic functions, i.e. the Exponentially Modified Gaussian, the Poisson, the Log-normal, the Edgeworth/Cramér series and the Gram/Charlier series, have been reviewed and commented in more detail.

  13. Improved Chromatographic Techniques for Sulfur Pollutants

    NASA Technical Reports Server (NTRS)

    Hartmann, C. H.

    1971-01-01

    This paper describes several improvements in instrumental techniques for the analysis of low ppb concentrations of sulfur gases using gas chromatography (G.C.). This work has focused on the analytical problem of ambient air monitoring of the two main sulfur gas pollutants, hydrogen sulfide and sulfur dioxide. The most significant technical improvement that will be reported here is the newly developed silica gel column for ppb concentrations of the light sulfur gases (COS, H2S, CS2, SO2, CH3SH). A simplified inlet system will be described which improves reliability of the GC system. The flame photometric detector is used as the means of selectively and sensitively detecting the low concentrations of sulfur gases. Improvements will be described which have yielded better performance than previously reported for this application of the detector. Also included in this paper will be a report of field monitoring using this improved GC system. Reliability and repeatability of performance at the low ppb concentrations of sulfur gases will be demonstrated.

  14. Intact protein separation by chromatographic and/or electrophoretic techniques for top-down proteomics.

    PubMed

    Capriotti, Anna Laura; Cavaliere, Chiara; Foglia, Patrizia; Samperi, Roberto; Laganà, Aldo

    2011-12-09

    Mass spectrometry used in combination with a wide variety of separation methods is the principal methodology for proteomics. In bottom-up approach, proteins are cleaved with a specific proteolytic enzyme, followed by peptide separation and MS identification. In top-down approach intact proteins are introduced into the mass spectrometer. The ions generated by electrospray ionization are then subjected to gas-phase separation, fragmentation, fragment separation, and automated interpretation of mass spectrometric and chromatographic data yielding both the molecular weight of the intact protein and the protein fragmentation pattern. This approach requires high accuracy mass measurement analysers capable of separating the multi-charged isotopic cluster of proteins, such as hybrid ion trap-Fourier transform instruments (LTQ-FTICR, LTQ-Orbitrap). Front-end separation technologies tailored for proteins are of primary importance to implement top-down proteomics. This review intends to provide the state of art of protein chromatographic and electrophoretic separation methods suitable for MS coupling, and to illustrate both monodimensional and multidimensional approaches used for LC-MS top-down proteomics. In addition, some recent progresses in protein chromatography that may provide an alternative to those currently employed are also discussed.

  15. Liquid chromatographic determination and identification tests for dexamethasone in bulk drugs and elixirs: collaborative study.

    PubMed

    Bunch, E A

    1987-01-01

    A normal phase liquid chromatographic method for the determination of dexamethasone in bulk drugs and elixirs was collaboratively studied by 6 laboratories. The method uses a silica column, water-modified acetic acid-methanol-methylene chloride mobile phase, cortisone internal standard, and photometric detection at 254 nm. Collaborators were supplied blind duplicate samples of 3 bulk drugs, 2 commercial elixirs, and 1 authentic elixir. Dexamethasone elixir dosage level is 0.5 mg/5 mL. Mean recovery of dexamethasone from the authentic elixir formulated to contain 0.471 mg/5 mL was 94.5%. (Authentic elixirs were found to stabilize about 6% below the theoretical concentration.) Mean recovery for the bulk drugs was between 97.1 and 100.1%. Mean coefficients of variation for bulk drug and elixir samples were less than 0.8% and 3.6%, respectively. Identification tests for dexamethasone by thin-layer chromatography, infrared spectroscopy, and relative LC retention times, as well as the gas chromatographic determination of alcohol in the elixirs were also collaboratively studied. Mean recovery of alcohol from the synthetic elixir was 98.6%. The mean coefficient of variation for alcohol for all samples analyzed was less than 1.4%. The LC method for dexamethasone in drug substance and elixirs, the identification tests, and the GC method for alcohol in dexamethasone elixirs have been adopted official first action.

  16. On-line coupling of supercritical fluid extraction and chromatographic techniques.

    PubMed

    Sánchez-Camargo, Andrea Del Pilar; Parada-Alfonso, Fabián; Ibáñez, Elena; Cifuentes, Alejandro

    2017-01-01

    This review summarizes and discusses recent advances and applications of on-line supercritical fluid extraction coupled to liquid chromatography, gas chromatography, and supercritical fluid chromatographic techniques. Supercritical fluids, due to their exceptional physical properties, provide unique opportunities not only during the extraction step but also in the separation process. Although supercritical fluid extraction is especially suitable for recovery of non-polar organic compounds, this technique can also be successfully applied to the extraction of polar analytes by the aid of modifiers. Supercritical fluid extraction process can be performed following "off-line" or "on-line" approaches and their main features are contrasted herein. Besides, the parameters affecting the supercritical fluid extraction process are explained and a "decision tree" is for the first time presented in this review work as a guide tool for method development. The general principles (instrumental and methodological) of the different on-line couplings of supercritical fluid extraction with chromatographic techniques are described. Advantages and shortcomings of supercritical fluid extraction as hyphenated technique are discussed. Besides, an update of the most recent applications (from 2005 up to now) of the mentioned couplings is also presented in this review.

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

    SciTech Connect

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

    1980-05-14

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

  18. Advanced hyphenated chromatographic-mass spectrometry in mycotoxin determination: current status and prospects.

    PubMed

    Li, Peiwu; Zhang, Zhaowei; Hu, Xiaofeng; Zhang, Qi

    2013-01-01

    Mass spectrometric techniques are essential for advanced research in food safety and environmental monitoring. These fields are important for securing the health of humans and animals, and for ensuring environmental security. Mycotoxins, toxic secondary metabolites of filamentous fungi, are major contaminants of agricultural products, food and feed, biological samples, and the environment as a whole. Mycotoxins can cause cancers, nephritic and hepatic diseases, various hemorrhagic syndromes, and immune and neurological disorders. Mycotoxin-contaminated food and feed can provoke trade conflicts, resulting in massive economic losses. Risk assessment of mycotoxin contamination for humans and animals generally depends on clear identification and reliable quantitation in diversified matrices. Pioneering work on mycotoxin quantitation using mass spectrometry (MS) was performed in the early 1970s. Now, unambiguous confirmation and quantitation of mycotoxins can be readily achieved with a variety hyphenated techniques that combine chromatographic separation with MS, including liquid chromatography (LC) or gas chromatography (GC). With the advent of atmospheric pressure ionization, LC-MS has become a routine technique. Recently, the co-occurrence of multiple mycotoxins in the same sample has drawn an increasing amount of attention. Thus, modern analyses must be able to detect and quantitate multiple mycotoxins in a single run. Improvements in tandem MS techniques have been made to achieve this purpose. This review describes the advanced research that has been done regarding mycotoxin determination using hyphenated chromatographic-MS techniques, but is not a full-circle survey of all the literature published on this topic. The present work provides an overview of the various hyphenated chromatographic-MS-based strategies that have been applied to mycotoxin analysis, with a focus on recent developments. The use of chromatographic-MS to measure levels of mycotoxins, including

  19. Chromatographic fingerprints analysis for evaluation of Ginkgo Biloba products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The leaf extract of Ginkgo biloba has purported value for improving mental capacities in Alzheimer’s patients. The flavonoids and the terpene lactones are considered to be the two main active components that influence human health. This paper compared an LC/UV chromatographic fingerprint method wi...

  20. On the ion chromatographic determination of S(IV)

    NASA Astrophysics Data System (ADS)

    Dasgupta, Purnendu K.

    Ion Chromatographie determination of S(IV) is described with special reference to the determination of SO 2(g) and/or aerosol S(IV) along with chloride, nitrate and sulfate in particulate matter. A method is presented for the baseline separation of the above species. The Chromatographic behavior of hydroxymethanesulfonate under various eluent conditions is discussed.

  1. Chromatographic profiles of Ginkgo biloba leaves and selected products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An LC-DAD-ESI/MS method was developed to obtain chromatographic profiles for the flavonoids and terpene lactones of Ginkgo biloba leaves and selected G. biloba products. The method was used to identify 46 glycosylated flavonols and flavones, 3 free flavonol aglycones, catechin, 10 biflavones, a dihy...

  2. Performance of chromatographic systems to model soil-water sorption.

    PubMed

    Hidalgo-Rodríguez, Marta; Fuguet, Elisabet; Ràfols, Clara; Rosés, Martí

    2012-08-24

    A systematic approach for evaluating the goodness of chromatographic systems to model the sorption of neutral organic compounds by soil from water is presented in this work. It is based on the examination of the three sources of error that determine the overall variance obtained when soil-water partition coefficients are correlated against chromatographic retention factors: the variance of the soil-water sorption data, the variance of the chromatographic data, and the variance attributed to the dissimilarity between the two systems. These contributions of variance are easily predicted through the characterization of the systems by the solvation parameter model. According to this method, several chromatographic systems besides the reference octanol-water partition system have been selected to test their performance in the emulation of soil-water sorption. The results from the experimental correlations agree with the predicted variances. The high-performance liquid chromatography system based on an immobilized artificial membrane and the micellar electrokinetic chromatography systems of sodium dodecylsulfate and sodium taurocholate provide the most precise correlation models. They have shown to predict well soil-water sorption coefficients of several tested herbicides. Octanol-water partitions and high-performance liquid chromatography measurements using C18 columns are less suited for the estimation of soil-water partition coefficients.

  3. Optimizing Chromatographic Separation: An Experiment Using an HPLC Simulator

    ERIC Educational Resources Information Center

    Shalliker, R. A.; Kayillo, S.; Dennis, G. R.

    2008-01-01

    Optimization of a chromatographic separation within the time constraints of a laboratory session is practically impossible. However, by employing a HPLC simulator, experiments can be designed that allow students to develop an appreciation of the complexities involved in optimization procedures. In the present exercise, a HPLC simulator from "JCE…

  4. Raman Gas Analyzer (RGA): Natural Gas Measurements.

    PubMed

    Petrov, Dmitry V; Matrosov, Ivan I

    2016-06-08

    In the present work, an improved model of the Raman gas analyzer (RGA) of natural gas (NG) developed by us is described together with its operating principle. The sensitivity has been improved and the number of measurable gases has been expanded. Results of its approbation on a real NG sample are presented for different measurement times. A comparison of the data obtained with the results of chromatographic analysis demonstrates their good agreement. The time stability of the results obtained using this model is analyzed. It is experimentally established that the given RGA can reliably determine the content of all molecular NG components whose content exceeds 0.005% for 100 s; moreover, in this case the limiting sensitivity for some NG components is equal to 0.002%.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  6. DETERMINATION OF INTERFERING TRIAZINE DEGRADATION PRODUCTS BY GAS CHROMATOGRAPHY-ION TRAP MASS SPECTROMETRY

    EPA Science Inventory

    Deethyl atrazine (DEA), along with other triazine degradation products, has been added to the US Environmental Protection Agency's Drinking Water Contaminant Candidate List (CCL). In its gas chromatographic (GC) analysis, deethyl atrazine, a degradation product of atrazine, can ...

  7. BARCHAN: Blob Alignment for Robust CHromatographic ANalysis.

    PubMed

    Couprie, Camille; Duval, Laurent; Moreaud, Maxime; Hénon, Sophie; Tebib, Mélinda; Souchon, Vincent

    2017-02-10

    Two-dimensional gas chromatography (GC×GC) plays a central role into the elucidation of complex samples. The automation of the identification of peak areas is of prime interest to obtain a fast and repeatable analysis of chromatograms. To determine the concentration of compounds or pseudo-compounds, templates of blobs are defined and superimposed on a reference chromatogram. The templates then need to be modified when different chromatograms are recorded. In this study, we present a chromatogram and template alignment method based on peak registration called BARCHAN. Peaks are identified using a robust mathematical morphology tool. The alignment is performed by a probabilistic estimation of a rigid transformation along the first dimension, and a non-rigid transformation in the second dimension, taking into account noise, outliers and missing peaks in a fully automated way. Resulting aligned chromatograms and masks are presented on two datasets. The proposed algorithm proves to be fast and reliable. It significantly reduces the time to results for GC×GC analysis.

  8. Chromatographic methods for analysis of triazine herbicides.

    PubMed

    Abbas, Hana Hassan; Elbashir, Abdalla A; Aboul-Enein, Hassan Y

    2015-01-01

    Gas chromatography (GC) and high-performance liquid chromatography (HPLC) coupled to different detectors, and in combination with different sample extraction methods, are most widely used for analysis of triazine herbicides in different environmental samples. Nowadays, many variations and modifications of extraction and sample preparation methods such as solid-phase microextraction (SPME), hollow fiber-liquid phase microextraction (HF-LPME), stir bar sportive extraction (SBSE), headspace-solid phase microextraction (HS-SPME), dispersive liquid-liquid microextraction (DLLME), dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO), ultrasound-assisted emulsification microextraction (USAEME), and others have been introduced and developed to obtain sensitive and accurate methods for the analysis of these hazardous compounds. In this review, several analytical properties such as linearity, sensitivity, repeatability, and accuracy for each developed method are discussed, and excellent results were obtained for the most of developed methods combined with GC and HPLC techniques for the analysis of triazine herbicides. This review gives an overview of recent publications of the application of GC and HPLC for analysis of triazine herbicides residues in various samples.

  9. Chromatographic and spectroscopic profiles of Cannabis of different origins: Part I.

    PubMed

    Brenneisen, R; elSohly, M A

    1988-11-01

    High-resolution capillary gas chromatography with flame ionization detection and mass spectrometry (GC and GC/MS) and high-performance liquid chromatography (HPLC) were used to establish complex chemical profiles (chemical signatures) of Cannabis samples of known origin. Over 100 compounds could be differentiated, including noncannabinoids (terpenes, alkanes) as well as minor and major cannabinoids and their acids. A characteristic peak pattern was found within a limited number of specimens of identical origin. Correlation studies on the basis of peak area ratios [A(x)/A(i.s.)] showed the feasibility of tracing Cannabis chemically to its country of origin. Several forensic science applications for the chromatographic and spectroscopic profiles of confiscated Cannabis samples are discussed, such as detection of additives (phencyclidine), differentiation of chemotypes, and monitoring of tetrahydrocannabinol (THC) potency.

  10. 21 CFR 862.2230 - Chromatographic separation material for clinical use.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Chromatographic separation material for clinical... Laboratory Instruments § 862.2230 Chromatographic separation material for clinical use. (a) Identification. A chromatographic separation material for clinical use is a device accessory (e.g., ion exchange absorbents,...

  11. 21 CFR 862.2230 - Chromatographic separation material for clinical use.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Chromatographic separation material for clinical... Laboratory Instruments § 862.2230 Chromatographic separation material for clinical use. (a) Identification. A chromatographic separation material for clinical use is a device accessory (e.g., ion exchange absorbents,...

  12. Gas Chromatography

    NASA Astrophysics Data System (ADS)

    Qian, Michael C.

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

  13. Accuracy of peak deconvolution algorithms within chromatographic integrators

    SciTech Connect

    Papas, A.N. ); Tougas, T.P. )

    1990-02-01

    The soundness of present-day algorithms to deconvolve overlapping skewed peaks was investigated. From simulated studies based on the exponentially modified Gaussian model (EMG), chromatographic peak area inaccuracies for unresolved peaks are presented for the two deconvolution methods, the tangent skim and the perpendicular drop method. These inherent inaccuracies, in many cases exceeding 50%, are much greater than those calculated from ideal Gaussian profiles. Multiple linear regression (MLR) was used to build models that predict the relative error for either peak deconvolution method. MLR also provided a means for determining influential independent variables, defining the required chromatographic relationships needed for prediction. Once forecasted errors for both methods are calculated, selection of either peak deconvolution method can be made by minimum errors. These selection boundaries are contrasted to method selection criteria of present data systems algorithms.

  14. Intercalibration of chromatographic methods for auxino phytodrugs in Solanaceae.

    PubMed

    Gennaro, M C; Marengo, E; Gianotti, V; Angioi, S; Copeta, G

    2003-04-18

    Three chromatographic methods are considered for the determination in Solanaceae of auxino-similar phytodrugs, so called because their structure resembles an auxine plant hormone. The phytodrugs studied were: 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenoxypropionic acid, 2,4-dichlorophenoxybutyric acid, 2-methyl-4-chlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, naphthylacetic acid and 2-naphthyloxyacetic acid. Three chromatographic methods, respectively based on ion-interaction HPLC, GC-MS with intra-injector derivatisation and CC-MS with pre-injection derivatisation, were developed, optimised and validated. A comparative discussion of the advantages/disadvantages of the methods suggests a strategy for their preferential use, that is essentially a function of the matrix complexity.

  15. Techniques of preparing plant material for chromatographic separation and analysis.

    PubMed

    Romanik, G; Gilgenast, E; Przyjazny, A; Kamiński, M

    2007-03-10

    This paper discusses preparation techniques of samples of plant material for chromatographic analysis. Individual steps of the procedures used in sample preparation, including sample collection from the environment or from tissue cultures, drying, comminution, homogenization, leaching, extraction, distillation and condensation, analyte enrichment, and obtaining the final extracts for chromatographic analysis are discussed. The techniques most often used for isolation of analytes from homogenized plant material, i.e., Soxhlet extraction, ultrasonic solvent extraction (sonication), accelerated solvent extraction, microwave-assisted extraction, supercritical-fluid extraction, steam distillation, as well as membrane processes are emphasized. Sorptive methods of sample enrichment and removal of interferences, i.e., solid-phase extraction, and solid-phase micro-extraction are also discussed.

  16. The chromatographic behaviour of wasp venom kinin, kallidin and bradykinin.

    PubMed

    MATHIAS, A P; SCHACHTER, M

    1958-09-01

    Wasp venom kinin which has hitherto appeared to be homogeneous can be resolved by ionexchange chromatography into a single major and two minor components. These are indistinguishable by their action on smooth muscle and by their rapid inactivation by chymotrypsin. All three components of wasp kinin are chromatographically different from kallidin or bradykinin. The close similarity of the latter compounds is confirmed by their identical behaviour on an ion-exchange resin.

  17. Can enantiomers be separated in achiral chromatographic systems?

    NASA Astrophysics Data System (ADS)

    Davankov, V. A.

    2016-10-01

    Consideration of chromatography of a nonracemic mixture on an achiral sorbent from a stereochemical point of view allows the claim that partial separation of the excess enantiomer zone from the racemate zone is possible only with analytes capable of self-associating under the conditions of the chromatographic column. It is from these positions that features of this process can be explained and conditions for its maximal proceeding formulated.

  18. Metal-Organic Frameworks for Thin-Layer Chromatographic Applications.

    PubMed

    Schenk, Claudia; Kutzscher, Christel; Drache, Franziska; Helten, Stella; Senkovska, Irena; Kaskel, Stefan

    2017-01-25

    Preparation of thin-layer chromatographic (TLC) plates based on metal-organic frameworks (MOFs) as porous stationary phases is described. DUT-67 (DUT = Dresden University of Technology), a zirconium based MOF, was used in combination with a fluorescent indicator as stationary phase for analyzing a small selection of a wide spectrum of relevant analytes. The successful separation of benzaldehyde from trans-cinnamaldehyde and 4-aminophenol from 2-aminotoluene is reported as a model system using optimized eluent mixtures containing acetic acid.

  19. Development of fast enantioselective gas-chromatographic analysis using gas-chromatographic method-translation software in routine essential oil analysis (lavender essential oil).

    PubMed

    Bicchi, Carlo; Blumberg, Leonid; Cagliero, Cecilia; Cordero, Chiara; Rubiolo, Patrizia; Liberto, Erica

    2010-02-26

    The study aimed to find the best trade-off between separation of the most critical peak pair and analysis time, in enantioselective GC-FID and GC-MS analysis of lavender essential oil, using the GC method-translation approach. Analysis conditions were first optimized for conventional 25 m x 0.25 mm inner diameter (dc) column coated with 6(I-VII)-O-tert-butyldimethylsilyl-2(I-VII)-3(I-VII)-O-ethyl-beta-cyclodextrin (CD) as chiral stationary phase (CSP) diluted at 30% in PS086 (polymethylphenylpolysiloxane, 15% phenyl), starting from routine analysis. The optimal multi-rate temperature program for a pre-set column pressure was determined and then used to find the pressures producing the efficiency-optimized flow (EOF) and speed-optimized flow (SOF). This method was transferred to a shorter narrow-bore (NB) column (11 m x 0.10 mm) using method-translation software, keeping peak elution order and separation. Optimization of the enantioselective GC method with the translation approach markedly reduced the analysis time of the lavender essential oil, from about 87 min with the routine method to 40 min with an optimal multi-rate temperature program and initial flow with a conventional inner diameter column, and to 15 min with FID as detector or 13.5 min with MS with a corresponding narrow-bore column, while keeping enantiomer separation and efficiency.

  20. Prediction of pesticides chromatographic lipophilicity from the computational molecular descriptors.

    PubMed

    Casoni, Dorina; Petre, Jana; David, Victor; Sârbu, Costel

    2011-02-01

    Quantitative structure-property relationship models were developed for the prediction of pesticides and some PAH compounds lipophilicity based on a wide set of computational molecular descriptors and a set of experimental chromatographic data. The chromatographic lipophilicity of pesticides has been evaluated by high-performance liquid chromatography (HPLC) using different chemically bonded (C18, C8, CN and Phenyl HPLC columns) stationary phases and two different organic modifiers (methanol and acetonitrile, respectively) in the mobile phase composition. Through a systematic study, by using the classic multivariate analysis, several quantitative structure-property/lipophilicity multi-dimensional models were established. Multiple linear regression and genetic algorithm for the variable subset selection were used. The internal and external statistical evaluation procedures revealed some appropriate models for the chromatographic lipophilicity prediction of pesticides. Moreover, the statistical parameters of regression and those obtained by applying t-test for the intercept (a(0)) and for the slope (a(1)) in order to evaluate relationship between experimental and predicted octanol-water partition coefficients in case of the test set compounds, revealed two statistically valid models that can be successfully used in lipophilicity prediction of pesticides.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  2. Chelate-modified polymers for atmospheric gas chromatography

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  3. Space Shuttle Trace Gas Analyzer

    NASA Technical Reports Server (NTRS)

    Dencker, W.

    1975-01-01

    A Trace Gas Analyzer (TGA) with the ability to detect the presence of toxic contaminants in the Space Shuttle atmosphere within the subparts-per-million range is under development. The design is a modification of the miniaturized Gas Chromatograph-Mass Spectrometer (GCMS) developed for the Viking Mars Lander. An ambient air sample is injected onto the GC column from a constant volume sample loop and separated into individual compounds for identification by the MS. The GC-MS interface consists of an effluent divider and a silver-paladium separator, an electrochemical cell which removes more than 99.99% of the hydrogen carrier gas. The hydrogen is reclaimed and repressurized without affecting the separator efficiency, a feature which enables a considerable weight reduction in the carrier gas supply system.

  4. Rotating annular chromatograph for continuous metal separations and recovery

    SciTech Connect

    Begovich, J.M.; Sisson, W.G.

    1981-01-01

    Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. By continuously introducing the feed material to be separated at a stationary point at the top of the bed and eluent everywhere else around the annulus, elution chromatography occurs. The rotation of the sorbent bed causes the separated components to appear as helical bands, each of which has a characteristic, stationary exit point; hence, the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6-m-long device with a 12.7-mm-wide annulus. The effect of annulus width and diameter has recently been studied using the same device with a 50.8-mm-wide annulus and another 0.6-m-long chromatograph with an 89-mm diameter and annulus widths of 6.4, 12.7, and 22.2 mm. These columns have been constructed of Plexiglas and typically operate at a gauge pressure of 175 kPa. To further study the effect of size and pressure, a new 445-mm-diam by 1-m-long column with a 31.8-mm-wide annulus has been fabricated. Its metal construction allows preparative-scale operation with a wide variety of liquids at pressures to 1.3 MPa. Three metal recovery systems have been explored: (1) separation of iron and aluminum in ammonium sulfate-sulfuric acid solutions; (2) separation of hafnium from zirconium in sulfuric acid solutions; and (3) the separation of copper, nickel, and cobalt in ammonium carbonate solutions. This last system simulates the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. It has been studied, using similar conditions, on each of the chromatographs, and the results demonstrate the effect of column dimensions on the quality and quantity of the separation. 8 figures, 1 table.

  5. Determination of Free-Energy Relationships Using Gas Chromatography

    NASA Astrophysics Data System (ADS)

    Snow, Nicholas H.

    1996-06-01

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

  6. Liquid chromatographic determination of pyrantel tartrate in medicated formulations.

    PubMed

    Konrardy, Joyce A; Burner, Mary A; Garner, Tommy W; Litchman, Mark A; Webster, Gregory K

    2003-01-01

    The validation of a novel liquid chromatographic (LC) method for the determination of pyrantel tartrate in feed is presented. The method provides a significant improvement over the efficiency and precision of AOAC Official Method 978.30. The method was shown to be accurate, precise, linear, and robust for medicated articles. Unlike the official method, the LC method was shown to be a superior stability-indicating method. After the method was validated by using laboratory blends, the effectiveness of the method was demonstrated with marketed product as well.

  7. Methods and apparatus for analysis of chromatographic migration patterns

    DOEpatents

    Stockham, Thomas G.; Ives, Jeffrey T.

    1993-01-01

    A method and apparatus for sharpening signal peaks in a signal representing the distribution of biological or chemical components of a mixture separated by a chromatographic technique such as, but not limited to, electrophoresis. A key step in the method is the use of a blind deconvolution technique, presently embodied as homomorphic filtering, to reduce the contribution of a blurring function to the signal encoding the peaks of the distribution. The invention further includes steps and apparatus directed to determination of a nucleotide sequence from a set of four such signals representing DNA sequence data derived by electrophoretic means.

  8. Methods and apparatus for analysis of chromatographic migration patterns

    DOEpatents

    Stockham, T.G.; Ives, J.T.

    1993-12-28

    A method and apparatus are presented for sharpening signal peaks in a signal representing the distribution of biological or chemical components of a mixture separated by a chromatographic technique such as, but not limited to, electrophoresis. A key step in the method is the use of a blind deconvolution technique, presently embodied as homomorphic filtering, to reduce the contribution of a blurring function to the signal encoding the peaks of the distribution. The invention further includes steps and apparatus directed to determination of a nucleotide sequence from a set of four such signals representing DNA sequence data derived by electrophoretic means. 16 figures.

  9. Cation exchange chromatographic elution and separation of rubidium

    SciTech Connect

    Mehta, V.P.; Khopkar, S.M.

    1982-01-01

    The systematic cation exchange chromatographic separation of rubidium on Dowex 50W-X8 was carried out with mineral acids and their salts as eluants.A selectivity scale for various eluants in terms of the elution constant was devised. Rubidium was separated from a large number of elements in binary mixtures by the process of gradient or selective elutions or selective sorption. The noteworthy feature of the method is the sequential separation of rubidium from alkali as well as alkaline earth elements.

  10. Multi-objective optimization of chromatographic rare earth element separation.

    PubMed

    Knutson, Hans-Kristian; Holmqvist, Anders; Nilsson, Bernt

    2015-10-16

    The importance of rare earth elements in modern technological industry grows, and as a result the interest for developing separation processes increases. This work is a part of developing chromatography as a rare earth element processing method. Process optimization is an important step in process development, and there are several competing objectives that need to be considered in a chromatographic separation process. Most studies are limited to evaluating the two competing objectives productivity and yield, and studies of scenarios with tri-objective optimizations are scarce. Tri-objective optimizations are much needed when evaluating the chromatographic separation of rare earth elements due to the importance of product pool concentration along with productivity and yield as process objectives. In this work, a multi-objective optimization strategy considering productivity, yield and pool concentration is proposed. This was carried out in the frame of a model based optimization study on a batch chromatography separation of the rare earth elements samarium, europium and gadolinium. The findings from the multi-objective optimization were used to provide with a general strategy for achieving desirable operation points, resulting in a productivity ranging between 0.61 and 0.75 kgEu/mcolumn(3), h(-1) and a pool concentration between 0.52 and 0.79 kgEu/m(3), while maintaining a purity above 99% and never falling below an 80% yield for the main target component europium.

  11. Thin layer chromatographic determination of deoxynivalenol in processed grain products.

    PubMed

    Trucksess, M W; Flood, M T; Page, S W

    1986-01-01

    The thin layer chromatographic (TLC) method of Trucksess et al. (J. Assoc. Off. Anal. Chem. (1984) 67, 40-43) was modified for the determination of deoxynivalenol (DON) in high-sugar breakfast cereals, corn syrup, and beer. Celite was added to the substrate before extraction with acetonitrile-water (84 + 16). After filtration through an alumina-charcoal-Celite (0.5 + 0.7 + 0.3) column, the filtrate was evaporated to dryness and redissolved in water, which was passed through an octylsilyl reverse phase column. DON was eluted with anhydrous ethyl ether. The residue remaining after the eluate was evaporated to dryness was dissolved in CHCl3-acetonitrile (4 + 1) and chromatographed on AlCl3-impregnated silica gel TLC plates. The blue fluorescent DON spot was quantitated fluorodensitometrically after the TLC plate was heated at 120 degrees C for 7 min. Recoveries of DON added to breakfast cereals at 100, 200, and 400 ng/g levels and to syrup and beer at 50, 100, and 200 ng/g levels averaged 86%. The limit of determination in these products was about 50 ng/g.

  12. A discontinuous Galerkin method to solve chromatographic models.

    PubMed

    Javeed, Shumaila; Qamar, Shamsul; Seidel-Morgenstern, Andreas; Warnecke, Gerald

    2011-10-07

    This article proposes a discontinuous Galerkin method for solving model equations describing isothermal non-reactive and reactive chromatography. The models contain a system of convection-diffusion-reaction partial differential equations with dominated convective terms. The suggested method has capability to capture sharp discontinuities and narrow peaks of the elution profiles. The accuracy of the method can be improved by introducing additional nodes in the same solution element and, hence, avoids the expansion of mesh stencils normally encountered in the high order finite volume schemes. Thus, the method can be uniformly applied up to boundary cells without loosing accuracy. The method is robust and well suited for large-scale time-dependent simulations of chromatographic processes where accuracy is highly demanding. Several test problems of isothermal non-reactive and reactive chromatographic processes are presented. The results of the current method are validated against flux-limiting finite volume schemes. The numerical results verify the efficiency and accuracy of the investigated method. The proposed scheme gives more resolved solutions than the high resolution finite volume schemes.

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

    PubMed

    Tang, Baokun; Row, Kyung Ho

    2013-08-01

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

  14. 40 CFR 86.511-90 - Exhaust gas analytical system.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... system for HC, CO and CO2, Figure F90-3, consists of a flame ionization detector (FID) (heated (235°±15... analytical system for methanol consists of a gas chromatograph (GC) equipped with a flame ionization detector. The analysis for formaldehyde is performed using high pressure liquid chromatography (HPLC) of...

  15. 40 CFR 86.511-90 - Exhaust gas analytical system.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... system for HC, CO and CO2, Figure F90-3, consists of a flame ionization detector (FID) (heated (235°±15... analytical system for methanol consists of a gas chromatograph (GC) equipped with a flame ionization detector. The analysis for formaldehyde is performed using high pressure liquid chromatography (HPLC) of...

  16. An application of gas chromatography to planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Oyama, V.

    1974-01-01

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

  17. Position sensitive radioactivity detection for gas and liquid chromatography

    DOEpatents

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

    2001-01-01

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

  18. 40 CFR 86.111-94 - Exhaust gas analytical system.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... hydrocarbon (THC) (hydrocarbon plus methanol in the case of methanol-fueled vehicles), methane (CH4) (for... of nitrogen (NOX). The schematic diagram of the continuous THC analysis train (and for THC plus... determination of THC, a methane analyzer (consisting of a gas chromatograph combined with a FID) for...

  19. Model-based design of peptide chromatographic purification processes.

    PubMed

    Gétaz, David; Stroehlein, Guido; Butté, Alessandro; Morbidelli, Massimo

    2013-04-05

    In this work we present a general procedure for the model-based optimization of a polypeptide crude mixture purification process through its application to a case of industrial relevance. This is done to show how much modeling can be beneficial to optimize complex chromatographic processes in the industrial environment. The target peptide elution profile was modeled with a two sites adsorption equilibrium isotherm exhibiting two inflection points. The variation of the isotherm parameters with the modifier concentration was accounted for. The adsorption isotherm parameters of the target peptide were obtained by the inverse method. The elution of the impurities was approximated by lumping them into pseudo-impurities and by regressing their adsorption isotherm parameters directly as a function of the corresponding parameters of the target peptide. After model calibration and validation by comparison with suitable experimental data, Pareto optimizations of the process were carried out so as to select the optimal batch process.

  20. Chromatographic hydrophobicity index: pH profile for polyprotic compounds.

    PubMed

    Fuguet, Elisabet; Ràfols, Clara; Bosch, Elisabeth; Rosés, Martí

    2009-11-06

    The Chromatographic Hydrophobicity Index (CHI) has been measured for several diprotic compounds. In order to model the variation of CHI with pH, a general equation for polyprotic compounds which allows the calculation of CHI for each one of the species has been proposed. Different types of diprotic solutes have been selected: neutral acids, neutral bases, and amphiprotic compounds (non-zwitterionic and zwitterionic). The applicability of the model to these complex polyprotic compounds, its advantages and limitations, as well as the information provided by the fits is discussed. In general, the model fits the experimental behaviour of all kind of solutes very well, obtaining the higher hydrophobicity values for the neutral form of the compounds, except for the zwitterionic phenylalanine. The equation and parameters obtained allow an easy calculation of CHI of the compound at any pH value.