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  • 1990-1994  (43)
  • 1980-1984
  • 1970-1974
  • 1992  (43)
  • Gas chromatography
  • Nuclear reactions
  • Physics
  • 1
    ISSN: 1434-4475
    Keywords: Gas chromatography ; Polyphenyl ethers ; Lubricants, synthetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The described synthesis of synthetic lubricants based on polyphenyl ethers requires an analytical characterization of the isomerization step, which is important to the process optimization. The separation of the intermediates succeeds with gas chromatography; the isomers are determined using a retention index system. The obtained results are compared with the composition of the final product, which was investigated by HPLC analysis.
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  • 2
    ISSN: 1432-1246
    Keywords: Stereometabolism ; Ethylbenzene exposure ; R- and S-mandelic acid ; Gas chromatography ; Enantiomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ethylbenzene is an important industrial solvent and a key substance in styrene production. Ethylbenzene metabolism leads to the formation of mandelic acid, which occurs in two enantiomeric forms, and phenyl-glyoxylic acid. To decide which enantiomer is preferably formed, 70 urine samples of exposed workers were taken at the end of shifts and — after 3-pentyl ester derivatisation — gas chromatographically analysed. The R/S ratio of mandelic acid enantiomers in urine amounts to 19:1, which means that R-mandelic acid is a major metabolite and S-mandelic acid is one of the minor urinary metabolites of ethylbenzene in man. The R/S ratio is independent of ambient air concentration of ethylbenzene within the investigated range. Compared to an ethylbenzene monoexposure the height of total mandelic acid excretion is decreased in the case of coexposure to other aromatic solvents.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 66 (1992), S. 298-299 
    ISSN: 1432-0738
    Keywords: 2,4-Dichlorophenol ; Accident ; Fatality ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A case involving an accidental fatality resulting from skin absorption of 2,4-dichlorophenol in a factory is presented. The compound was quantified using gas chromatography after separation on a SP-1240 DA column and detection with flame ionization. Confirmation was obtained with mass spectrometry. Blood concentration was 24.3 mg/l. Other drugs, including ethanol, were not detected.
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  • 4
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Activity coefficients ; 18-Crown-6-ether and tetraethyleneglycol dimethyl ether ; Thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The thermodynamic properties of different solutes at infinite dilution have been determined at 323.15 K. Deviations from ideality are discussed in terms of different contributions. The activity coefficients are compared with the calculated values by the one group contribution method.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 33 (1992), S. 103-112 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chiral separations ; Allethrin ; Cypermethrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid and gas chromatographic separations of the pyrethroid insecticides allethrin and cypermethrin have been investigated with various achiral and chiral stationary phases. Diastercomeric and enantiomeric selectivity was observed for cypermethrin on a Pirkle-type chiral LC stationary phase, but very strong interactions and therefore long retention times prevented the separation of allethrin on this phase. Trans-allethrin isomers were separated on a chiral β-cyclodextrin RP-HPLC column while cypermethrin showed some difficulties on this phase due to isomerization. Diastereomeric but no enantiomeric selectivity by GC was achieved for cypermethrin with an apolar DB 5 capillary. GC separation of the diastereomers was used to study the selective photodegradation of cypermethrin isomers after forestry applications. Chiral β-cyclodextrin-based GC phases showed some enantioselectivity for cis- and trans-allethrin isomers. A separation of the eight isomers into six partially resolved peaks was achieved by GC with a coupled column consisting of chiral permethylated β-cyclodextrin and DB 1701 as stationary phases. This combination was used to characterize allethrin formulations intended for indoor use and to investigate allethrin products formed by ozonolysis of thin films of the insecticide.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Free fatty acids ; Cheese ; Programmed temperature vaporizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method with a capillary column and a programmed temperature vaporizer injector has been used to analyze the individual free fatty acids in cheese. The lipids were extracted from an acidified cheese slurry with diethyl ether and treated with tetramethylamonium hydroxide (TMAH) to convert the free fatty acids to tetramethylammonium soaps (TMA-soaps), which were subsequently pyrolyzed to methyl esters in the injector. Carrying out injection at the initial column temperature resulted in lower dispersion of the results, but the solvent front prevented quantitative determination of butyric and caproic acids, and an injector temperature of 300°C was therefore employed. Under the conditions tested, trimethylamine (tma) flash-off did not affect the determinations. The accuracy of the method improved at higher free fatty acid contents (coefficient of variation of 0.53% for a total free fatty acid content of 9000 mg/kg as opposed to 7.0% for a total free fatty acid content of 1400 mg/kg). The recovery rate for individual free fatty acids ranged between 91 and 103%.
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  • 7
    ISSN: 1612-1112
    Keywords: Gas chromatography ; coupling capillary columns ; Selectivity optimization ; Dual oven tuning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A computer-assisted procedure is presented for optimization of selectivity of tandem capillary columns with the same apolar (SE-54) stationary phase by varying column temperatures. The procedure is based on a threshold criterion calculated from the required resolution factor in which the separating power of the columns as a function of temperature is incorporated. The validity of the procedure has been verified by the analysis of a sample containing 33 hydrocarbons on two 31 m×0.3 mm i.d. SE-54 capillary columns coupled in series and by varying the temperatures of both columns in the range 60–100°C. At the optimum temperatures (70°C for the first and 92°C for the second column) 26 compounds were resolved equal to or better than Rji=1.00 in 22.8 min.
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  • 8
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Carbon adsorbents ; Methyliodide ; Effect of KI on adsorption ; Thermodynamics of adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography has been used to measure the adsorption at zero surface coverage of methyl iodide on different types of carbon. The effect on the adsorption of methyl iodide of adding potassium iodide to the carbon samples was also studied. The differences observed in the behaviour of these samples for the adsorption of methyl iodide are explained on the basis of the textural characteristics of the samples. Thermodynamic functions of adsorption of methyl iodide at zero surface coverage are obtained.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Partition coefficients ; Olive oil-nitrogen partition ; QSAR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas-liquid chromatographic method has been used for direct determination of the partition coefficients (KD) of alcohols, ethers and ketones between olive oil and nitrogen. Olive oil was characterised as a stationary phase for gas chromatography. The differential molar enthalpies of solution were also calculated from retention data. Correlations between log KD for olive oil — nitrogen and molecular connectivity indices, differential molar enthalpies of solution, biological activity and partition coefficients for blood-air were obtained.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 621-626 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Methyl and ethyl chloroformate ; Derivatization in the presence of water ; Alkyl and alkoxycarbonyl esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Phenolic acids, i.e. benzoic, phenylacetic, phenylpropenoic (cinnamic), phenylglycolic (mandelic), phenylpropionic and their variously substituted forms can be converted almost instantly to derivatives amenable to GC by treatment with methyl or ethyl chloroformate. The reaction, catalyzed by pyridine, proceeds even in the presence of water. The carboxylic group is esterified to the corresponding alkyl ester but even the alkoxycarbonyl ester (mixed anhydride) can be produced by altering the reaction conditions. Hydroxyl groups on the benzene ring or adjacent to the carboxylic group are converted to the alkoxycarbonyl ethers. Benzoic acid and some of its substitutents, unlike the other aromatic acids, shows a tendency to mixed anhydride formation even under conditions used for alkyl esters. A well deactivated capillary column with a thin film of stationary phase of low polarity enables even the mixed anhydrides to be analyzed successfully.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 163-165 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Cyclodextrins ; Crown ethers ; Dimethylnaphthalene isomer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The twelve structural C2 isomers of naphthalene are resolved on a single capillary column using α, β, or γ cyclodextrin as the stationary phase. A change in elution order is seen upon going from α to β and then γ cyclodextrin which can be related to the size of the cyclodextrin cavity and the stereochemical fit of the isomer. A crown-ether column and a liquid-crystal column were found to be unable to separate all of the isomers.
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  • 12
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; Partition coefficients ; Multiple headspace extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Equilibrium headspace gas chromatography has been applied to the determination of the partition coefficients of volatile compounds in water-air systems. Only techniques that are suited to a fully automatic headspace procedure using the pneumatic headspace sampling-technique have been considered. Particularly simple is the technique of “vapor phase calibration —VPC” where an external vapor standard is used to calibrate the concentration of the volatile analyte in the headspace, while the concentration in the sample is found from the difference in the total amount in the vial. This technique is described in detail for 2-butanone in water. Finally, the water-air partition coefficients of several selected volatile compounds at different temperatures are listed together with their temperature functions.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 241-248 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Natural insecticides ; Marigolds ; Isolation of volatiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The results of optimizing Soxhlet and Simultaneous Distillation-Extraction (SSDE) procedures for the isolation of natural insecticides fromTagetes erecta, Tagetes patula, andTagetes minuta, members of theCompositae family, are presented. Extraction procedures were developed and validated that produced the extract with the highest degree of biocidal activity. The highest activity was obtained with extracts isolated by SSDE using methylene chloride. Initial work was carried out on a micro-SSDE. Preparative SSDE was used to provide large quantities of extracts for bioassays. Bioassays were used to govern optimization procedures usingAedes aegypti andAnopheles stephensi adults and larvae as target organisms.Tagetes minuta was determined to be the most active of the three species studied. Evaluation of activity and recovery versus extraction time was investigated. It was determined that an extraction time of ten hours resulted in the highest activity and over 90% recovery of the oils. Finally, supercritical fluid extraction of the flowers with CO2 was compared to SSDE.
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  • 14
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sociation constants ; Hydrogen bonding solutes ; Nearly ideal binary solvent theory ; Isosteric solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic data measured on mixtures of 19,24-dioctadecyldotetracontane, A≡C78, and 18,23-dioctadecyl-1-hentetracontanol, POH, allow the determination of the standard chemical potential of a solute on an ideal stationary phase with primary alcohol groups at ideal dilution. The Nearly Ideal Binary Solvent Theory provides the link between these data and the sociation constant of the solute with the primary alcohol. The method was applied to calculate sociation constants of a series of hydrogen bonding solutes. Results are compared with those determined by spectroscopy and calorimetry.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 398-410 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Reversed-flow technique ; Catalysis ; Hydrodenitrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Many important parameters of surface catalysed reactions can be determined simultaneously, under nonsteady state conditions using Reversed-Flow Gas Chromatography. A simple, slightly modified gas chromatograph is required. The distorted diffusion bands, obtained experimentally for reactant and product(s), can be analysed mathematically, using simple PC programs, to give the pre-exponential factors and the exponential coefficients of a function consisting of the sum of two-four exponential functions of time. From these, and some geometrical and diffusional characteristics of the reaction cell, the values of adsorption, desorption and reaction rate constants, the overall mass transfer coefficients in the gas and in the solid catalyst, and the adsorption equilibrium constant, for both reactant and product(s) can be calculated. The above parameters were determined at various temperatures and over three catalysts for the hydrodenitrogenation of piperidine ton-pentane, an industrially important hydrotreating process. The results obtained can help to understand the mechanism of reactions on solid surfaces and to confirm experimentally theoretical calculations on adsorption and surface reactions.
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  • 16
    ISSN: 1612-1112
    Keywords: Gas chromatography ; High-pressure Soxhlet extraction ; Organochlorine residue analysis ; Supercritical fluid extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The operational conditions of a high-pressure Soxhlet extractor (pressure, temperature, time and amount of sample) have been optimized, using carbon dioxide as extractant for the determination of organochlorine pesticides and polychlorinated biphenyls (PCBs) in certified potato, carrot, olive oil and lyophilized fish tissue samples. Good recoveries were obtained.
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  • 17
    Electronic Resource
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    Springer
    Chromatographia 34 (1992), S. 475-478 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Telomeric fluoroalkanols ; Retention index ; Regression equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of fluoroalkanols with the general formula H(CF2CF2)nCH2OH (n=1–8) on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices were determined at three temperatures. A correlation between the retention index values, the molecular weights and the number of C and F atoms in the solute molecules was found.
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  • 18
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    Springer
    Chromatographia 34 (1992), S. 461-467 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Allyl thiocyanate and isothiocyanate ; Plant extract ; Analytical artifacts ; Isomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Allyl thiocyanate and isothiocyanate were synthesized and could be analysed by gas chromatography without isomerization by keeping the injector at, or below, 50°C. Synthetic allyl isothiocyanate contained none of the isomeric thiocyanate but allyl thiocyanate contained 0.5% of isothiocyanate. The NMR spectra indicated both compounds to be free of the corresponding isomer. Analysis of extracts of stinkweed, mustard and horseradish by GC using non-isomerizing conditions showed that only the stinkweed extract contained allyl thiocyanate. Mustard and horseradish extracts contained allyl, and other, isothiocyanates but no allyl thiocyanate. Allyl thiocyanate previously reported in extracts of mustard and horseradish was most likely an artifact caused by partial isomerization of allyl isothiocyanate under the conditions of isolation and/or analysis.
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  • 19
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    Chromatographia 34 (1992), S. 513-528 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Open-tubular (capillary) columns ; History of chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 20
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    Springer
    International journal of legal medicine 105 (1992), S. 65-68 
    ISSN: 1437-1596
    Keywords: Fire victim ; Exposure before or after death ; Carbon monoxide hemoglobin ; Gas chromatography ; Brandopfer ; Antemortale und postmortale Exposition ; Kohlenmonoxid-Hämoglobin ; Gaschromatographie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Mit Hilfe der Gaschromatographie wurde die Kohlenmonoxid-Konzentration im Blut des rechten und linken Herzens vergleichend untersucht. Das Material stammt von Leichen mit antemortaler oder nicht-antemortaler Feuer- oder CO-Exposition. Das Konzentrationsverhältnis von COHb zwischen linkem und rechtem Herzblut (L/R-Quotient) scheint ein nicht brauchbares Kriterium zu sein, um festzustellen, ob der Tod sich vor oder nach der Feuer-Exposition ereignet hat; mit der Ausnahme von solchen Fällen, wo bei makrokopischer Untersuchung kein Ruß in den Atemwegen gefunden wird und wo die COHb-Konzentration innerhalb jener Grenzen ist, welche für Zigaretten-Raucher als normal angesehen werden.
    Notes: Summary Carbon monoxide hemoglobin (COHb) concentrations in left and right heart blood samples from cadavers both exposed and not exposed to fire or CO gas were analyzed by the gas chromatographic method. The COHb concentration ratio between samples of left and right heart blood (L/R ratio) does not appear to be useful for establishing whether death has occurred before or after exposure to fire with the exception of cases where no soot can be detected in the airways by the naked eye and the COHb concentration in the blood sample is within the level considered normal for tobacco smokers.
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  • 21
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    Springer
    Chromatographia 33 (1992), S. 575-580 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention indices ; Solubility parameters ; Alkylbenzenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new three-parameter equation is obtained that relates gas liquid chromatographic retention indices for nonpolar and weakly polar substances such as hydrocarbons to their total solubility parameters, molar volume and the number of carbon atoms by applying the expanded solubility parameters model to gas-liquid chromatography (GLC). Regression analysis is performed according to the three-parameter equation for a number of C6−C11 alkylbenzenes on stationary phases of different polarity and at various temperatures. The regression coefficient is always higher than 0.9995 and the standard deviation lower than 3.3 i.u. For isomers, the equation is simplified to a two-parameter equation and the correlations between retention indices, total solubility parameters and molar volume are excellent. Regression analysis shows that the approach successfully predicts the retention indices of alkylbenzenes on polar and non-polar stationary phases.
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  • 22
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    Springer
    Chromatographia 33 (1992), S. 147-150 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; MS detection ; Metachlor ; Herbicide residues ; Tomatoes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatograph/mass selective detector method is presented for the analysis of the major metabolic residues of metolachlor by acid hydrolysis of tomato fruit. The two major hydrolysis products, CGA-37913 (2-[2-ethyl-6-methylphenyl]amino-1-propanol) and derivatised CGA-49751 (4-[2-ethyl-6-methylphenyl]-2-hydroxy-5-methyl-3-morpholinone) were monitored in the selective ion mode atm/z 162 andm/z 160, respectively. Recoveries from 87 to 96% were obtained for tomato fortified at 50 to 200μg kg−1. The proposed method of analysis will allow for a detection limit of 11 μg kg−1 for CGA-37913 and 12 μg kg−1 for the derivatised CGA-49751.
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  • 23
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Cheese volatiles ; Mixed phase ; Optimum phase composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A mixed-phase capillary GC column has been designed for the separation of the compounds commonly present in the volatile fraction of cheeses. The design includes the calculation of the optimum phase concentration and the operating conditions. The evaluation of the resulting column indicates that its performance in the qualitative and quantitative analysis of cheese volatile compounds is better than those of other columns coated with a single stationary phase.
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  • 24
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    Chromatographia 33 (1992), S. 272-278 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Electron-capture detector ; Polychlorinated biphenyls ; Simplex optimization ; Principal component factor analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified simplex technique has been applied to optimize the performance of an electron-capture detector under constant-current and constant-frequency pulse modes for the gas chromatographic analysis of polychlorinated biphenyls. Optimal performance was obtained by adjusting the four experimental parameters of pulse voltage, detector temperature, make-up gas flow rate, and reference current (or pulse frequency) using the signal-to-noise ratio of the eluting peak as the criterion. The results show that constant-current pulse mode has better sensitivity and dynamic range whereas the constant-frequency pulse mode has the lower detection limit. Subsequent principal component factor analysis indicated that similar performance is achievable using only three parameters.
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  • 25
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    Chromatographia 33 (1992), S. 279-283 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Direct aqueous injection ; KF.2H2O containing sorbents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For direct aqueous injection gas-chromatographic analysis of polar compounds present in aqueous solutions sorbents containing conventional stationary phases and potassium fluoride crystal hydrate are proposed. On such sorbents polar compounds elute with narrow symmetrical zones under gentle chromatographic conditions. In such sorbents KF.2H2O mainly deactivates the surface of the solid support. The polarity of these sorbents is compared with the polarity of molten potassium fluoride dihydrate and conventional stationary phases.
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  • 26
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    Chromatographia 34 (1992), S. 636-642 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Linear programmed temperature indices ; Retention temperature ; Calculation of retention indices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Programmed Temperature Retention Indices (PTRI) of several solutes on four packed columns coated with stationary phases covering a range of polarities have been estimated for sixteen temperature programs by exploiting isothermal retention data obtained at 70–180°C. PTRI calculations have been carried out by interpolating the retention temperatures calculated according to Curvers et al. from the graphs of retention index against column temperature, matched according to polynomials of grade 1 to 3 and by hyperbolic fitting. PTRIs by the van den Doole & Kratz equation and by cubic splines have also been computed. Comparison is made of these PTRIs with those calculated from cubic splines of the measured retention temperatures throughout the various temperature programs and the retention index deviations in terms of variance and relative error are explored. The smallest variance are found for the less polar stationary phases, PS-255 and OV-105; the biggest variance values are found for OV-275. Data are given showing that about 95% of the determinations of PTRIs on the low polarity stationary phases show deviations of not greater than 2%.
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  • 27
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Pulsed discharge emission detector ; Emission spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This publication contains our initial development of a pulsed discharge emission detector (PDED) (patent pending). It uses a pulsed high voltage discharge in helium, which provides a stable source for atomic and polyatomic emission spectroscopy. We have evaluated this detector for both quantitative and qualitative analysis of a range of chemical compounds. Emission spectra observed from the pulsed high voltage discharge are valuable for spectral analysis. The results obtained for selected permanent gases in the ultraviolet, visible and infrared regions of the optical spectrum indicate that these spectra can be used for compound identification after a chromatographic separation. The data are unique in our opinion and serve as a basis for the future development and investigation of the analytical significance of this detection method.
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  • 28
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    Chromatographia 34 (1992), S. 266-268 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phases ; Crosslinking ; Europium chelates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic stationary phase containing europium chelates was modified by a free radical crosslinking with 2,2′-azobis(2-methylpropionitrile). The stationary phase was characterized by injections of the McReynolds series of standard solutes. A better thermal stability and an enhanced polarity was observed.
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  • 29
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Alipharic amines in air ; Impinger sampling ; Gas membrane enrichment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the determination of shortchain aliphatic amines in ambient air based on impinger sampling in dilute H2SO4, selective enrichment across a PTFE gas membrane and quantification by gas chromatography. The enrichment step is carried out in a flow system directly connected to the chromatograph. The separation is performed on a packed column with nitrogen selective detection. The enrichment per sample volume was in the range 7.3 to 8.2 mL−1 for C1−C6 amines. Detection limits were ca 3–10 nM with enrichment of a 2.9 mL liquid sample. After impinger sampling of 5 m3 air in 10 mL absorption solution, this corresponds, to 0.4–0.8 ng/m3 (ca 0.2–0.5 ppt by volume) in air.
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  • 30
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid organic salts ; Alkane-and perfluoroalkanesulfonates ; Solvation mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A series of tetraalkylammonium alkanesulfonate and perfluoroalkanesulfonate liquid organic salts are studied as model solvents to characterize quantitatively the influence of fluorine substitution on retention in gasliquid chromatography. Interpretation of solvation interactions is performed using two new thermodynamic models suggested by Kollie and Poole and Abraham and co-workers. For the solvents studied any reduction in dispersive interactions accompanying the introduction of fluorine must be approximately offset by an increase in the cavity term. Of the polar interactions, orientation interactions are large but only weakly influenced by the introduction of fluorine; solvent hydrogen-bond base interactions are strong and significantly influenced by the inductive effect of fluorine on the electron density on the sulfonate group; solvent hydrogen-bond acid interactions are negligible for all salts.
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  • 31
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Methylphenylsiloxane stationary phases ; Kovats retention indices ; Monosubstituted benzenes, benzaldehydes and acetophenones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention indices of some monosubstituted benzenes, benzaldeyhdes and acetophenones have been determined on seven OV polymethylphenylsiloxane liquid phases. The interactions and forces that affect the separation of the isomers and their elution sequences are discussed, taking into account mesomeric and inductive effects of the substituents in the benzene ring and the dipole moments of these solutes. These phases are not very selective for the separation or the accurate assessment of the effect of substituent over the benzene nucleus. This may be explained by the presence of the considerable number of benzene nuclei integral to the structure of these phases.
    Type of Medium: Electronic Resource
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  • 32
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 33 (1992), S. 507-513 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Supercritical fluid chromatography ; Supercritical carbon dioxide ; Sulfur chemiluminescence detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sulfur chemiluminescence detection (SCD) for the determination of sulfur-containing compounds in gas chromatography (GC) and supercritical fluid chromatography (SFC) is described. The detector is based on the chemiluminescence reaction of ozone with sulfur monoxide which is produced in an H2/O2 reducing flame from sulfur-containing analytes. High selectivity over nonsulfur-containing species has been achieved for a number of mercaptans and sulfur-containing polycyclic aromatic hydrocarbons. Minimum detectable quantities of 23 and 26 pg S (S/N=3) for dibenzothiophene and benzo[b]naphtho[1,2-d]thiophene, respectively, have been obtained using the SFC/SCD system. It was found that connecting a buffer volume flask to the vent of the vacuum pump that draws the effluents and ozone gas into the chemiluminescence reaction chamber, increases the sensitivity of the SCD.
    Type of Medium: Electronic Resource
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  • 33
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 33 (1992), S. 237-243 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Porous graphite ; Adsorption isotherms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The objective of this work was to correlate adsorption isotherms of ethylene at −78°C on porous graphitic carbon (PGC) with gas chromatographic performance, the intention being that such isotherms could be used as a quality control test for PGC's in general, whether used for GC, HPLC or other adsorptive purposes. GC of test solutes shows that severe peak tailing on bare PGC is removed almost totally by a coating PGC with as little as 0.05% by weight of Carbowax 1500. Surprisingly there is little corresponding change in the ethylene adsorption isotherms, although it is possible to distinguish small differences at surface coverages below 5% of a monolayer of ethylene. Further work is required to establish a useful QC test.
    Type of Medium: Electronic Resource
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  • 34
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 83-84 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Unified retention index ; BP-1 dimethylsiloxane ; Hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic retention indices for 23 hydrocarbons were determined on BP-1 dimethylsiloxane between 45 and 65°C. From the data measured unified retention indices were calculated. These values agree well with the corresponding experimental values. The values of unified retention indices obtained on BP-1 are compared with those determined on OV-101 and on squalane. The differences between the unified and the experimental retention indices on BP-1, OV-101 and squalane columns are shown.
    Type of Medium: Electronic Resource
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  • 35
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Dihydroxy crown ether stationary phases ; Immobilization by condensation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two new kinds of crown ethers: 3,5-dibutyl-unsymmetrydibenzo-14-crown-4-dihydroxy (cis-, and trans-) with the OH-terminal silicone oil in different proportion were coated on glass capillary columns, and immobilized by condensation using a coupling agent of alkyltrimethoxysilane. Chromatographic characteristics, including column efficiency, polarity, selectivity, phase transition temperature and thermal stability were studied. The columns were compared with PEG-20M in terms of polarity and selectivity. The immobilization and retention mechanisms are also discussed.
    Type of Medium: Electronic Resource
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  • 36
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 834-836 
    ISSN: 0935-6304
    Keywords: Static headspace ; Optimization of conditions ; Gas chromatography ; Blood alcohol ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The precision and sensitivity of head-space GC can be improved by careful selection of the operating conditions: partitioning in the vapor phase can be promoted by altering the sample matrix; the ratio of the volumes of the gaseous and liquid phases, the sample temperature, the equilibration time, and the effect of sample mixing should also be considered.Most of the principles covered here can be applied to either manual headspace GC or to headspace GC utilizing an automated sampler.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 37
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 478-479 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Kováts retention index ; GW-BASIC program ; Computer-assisted calculation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 38
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 256-259 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; High temperature ; Narrow bore glass columns ; CH3O-terminated polysiloxane, PS-090 ; Triglycerides ; Free base porphyrins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of high-temperature-stable, medium polarity glass capillary columns coated with immobilized PS-090 (a 20 % diphenyl-substituted, CH3O-terminated polydimethylsiloxane) has made it possible to analyze routinely, and with good separation efficiency, high molecular weight compounds such as triglycerides and free base porphyrins. Cold on-column injection was used throughout this work to avoid discrimination against involatile compounds, and disposable (fused silica) retention gaps were used to protect the column against contamination with involatile material. On-column injection into narrow bore glass columns was achieved by using glass-to-silica connections to attach wider bore (0.2 mm i.d.) deactivated fused silica tubing to the columns.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 39
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 332-334 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary column ; Volatile components of crab and shrimp ; Environmental contaminants ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary GC and GC-MS have been used for the identification and quantitation of n-alkanes, naphthalenes, and alkylben-zenes among the volatile components of crab and shrimp meat.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 40
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 505-509 
    ISSN: 0935-6304
    Keywords: Unified chromatography ; Gas chromatography ; Supercritical fluid chromatography ; Open tubular column ; Injection technique ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A unified approach to sequential gas and supercritical fluid Chromatography using 50 μm i.d. open tubular columns is described. Sample introduction is performed by means of a rotary injection valve. In order that linear velocities can be optimized independently, a second rotary valve in the chromatographic oven is used to direct the flow of column eluate to the flame ionization detector through either fused silica tubing in GC, or a frit restrictor in SFC.Applications of sequential GC-SFC on a 50 μm i.d. open tubular column are demonstrated, and comparisons made between sequential GC-SFC on 50 and 100 μm i.d. columns.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 41
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 745-750 
    ISSN: 0935-6304
    Keywords: On-line coupling ; LC-GC ; LC-GC-MS ; Liquid chromatography ; Gas chromatography ; Mass spectrometry ; Chlorinated polycyclic aromatic hydrocarbons ; Urban air ; Occupational exposure measurement ; Bus drivers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Coupled liquid chromatography - gas chromatography - mass spectrometry (LC-GC-MS) has been applied for on-line clean up, separation, and identification of chlorinated polycyclic aromatic hydrocarbons (CI-PAHs). A loop-type interface was used to couple the liquid chromatograph on-line with the GC-MS, and concurrent solvent evaporation was used for sample transfer.A back-flush technique was used in conjunction with a two-dimensional column system for isolation of CI-PAHs and polycyclic aromatic hydrocarbons (PAHs). This fraction was transferred on-line to the GC and separated on a capillary column. Selective and sensitive detection of CI-PAHs in the GC eluate was obtained by negative ion chemical ionization (NICI) mass spectrometry and selected ion monitoring (SIM).The combined on-line system for isolation, separation, and identification showed high precision and accuracy, and demonstrated a linear response from 1 to 1000 pg for chlorinated PAHs. The estimated detection limit was 250 fg for 1-chloropyrene and 1,6-dichloropyrene.The technique was demonstrated by analysis of urban air samples. The low detection limit made it possible to use the technique for analysis of personally carried monitoring equipment for measurement of exposure to CI-PAHs in the work environment.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 42
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 539-547 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Neural networks ; Pattern recognition ; Simulated data ; Simulated annealing ; Essential oils ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The matching of the pattern of peaks produced during gas chromatography is of importance to many applications. At present, this task is generally performed manually, but this generates the usual problems associated with human inspection, such as a lack of objectivity and reproducibility, proneness to errors, and practical restriction of the volume of data which can reasonably be processed.This paper explores the use of a novel algorithm for automation of this task. The performance of the method on well controlled simulated data sets and real chromatograms is used to show not only how problems of manual inspection can be circumvented, but also how the existence of such a powerful method should open up the possibility of many new analyses for quality control, discrimination of varieties of sample, and the identification of specific components within a sample.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 43
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 800-806 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Resolution of enantiomers ; Chiral stationary phase ; Derivatized cyclodextrin ; Trifluoroacetylated cyclodextrin ; Structural effects ; Thermodynamic properties ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: More than 30 enantiomeric alcohols have been analyzed, without prior derivatization, by gas chromatography using a fused silica capillary column coated with octakis(3-O-trifluoro-acetyl-2,6-di-O-n-pentyl)-γ-cyclodextrin. Most were analyzed over a range of isothermal temperatures from 35 to 70°C. Enantiomeric separations were observed for most of the analytes, even at temperatures as low as 35°C.The stereoselectivity of the stationary phase was found to depend on the length of the longest carbon chain attached to the stereogenic centre in 2- and 3-hydroxy alkanes, the relative positions of the methyl and hydroxyl substituents in methylsubstituted alcohols, and the effects of multiple bonds in the analyte molecule. Thermodynamic data calculated from the results suggest that the enantiomers of all the analytes are resolved by a similar process. Retention and thermodynamic data are presented and possible mechanisms discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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