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  • Artikel  (670)
  • Gas chromatography
  • 1985-1989  (277)
  • 1980-1984  (393)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Trees 1 (1987), S. 94-101 
    ISSN: 1432-2285
    Schlagwort(e): Monoterpenes ; Abies alba Mill ; Resin ; Seeds ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Using gas-chromatographic methods, the variability of the contents of monoterpene hydrocarbons (α-pinene, β-pinene, Δ3carene and limonene) in the resin of silver fir seeds (Abies alba Mill.) was studied. Resin cavities were characterized according to their position on the seed surface. It was estabilished that the terpene content of the resin of cavities localized on the abaxialadaxial surfaces of the seed differs significantly, creating a gradient of resin composition around the circumference of the seed. The differences between various resin cavities of single seeds were greater than the differences between different seeds of a single cone and between seeds of various cones on a single tree. An accurate definition of the resin cavity location on the seeds appears to be a fundamental condition for the collection of a sample representing the resin composition of individual trees. Resin biosynthesis in the course of organogenesis and the control of terpene contents in the resin of various locations on the seed and the cone are discussed.
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 23 (1986), S. 113-118 
    ISSN: 1432-1432
    Schlagwort(e): Primordial terrestrial atmospheres ; CH4, C2H2, CO2 ; Prebiotic synthesis ; High-frequency discharge ; Hydrocarbons ; Gas chromatography ; Mass Spectrometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Various hydrocarbons were synthesized by high-frequency discharge in a primordial terrestrial model atmosphere. The products were extracted by benzene or methanol and analyzed by GC-MS. The mean carbon chain length of the hydrocarbons formed by the discharge through pure CH4 gas was less than 6. Benzene was also obtained. Some isomers were obtained for each of the hydrocarbons containing a given number of carbons. When a small amount of C2H2 was added to the CH4, longer chain compounds were formed, as compared with discharge in CH4 only. However, when the amount of C2H2 was increased, unextractable high molecular weight compounds were produced. The amounts of products decreased as the mixing ratio of CO2 to CH4 increased. No hydrocarbons were detected when the ratio of CO2/CH4 exceeded 1.
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 34 (1983), S. 20-26 
    ISSN: 1570-7458
    Schlagwort(e): Dioryctria abietella ; Cone pyralid ; Lepidoptera ; Pyralidae ; Sex pheromone, (Z,E)-9,11-tetradecadienyl acetate ; Single sensillum recordings ; Electroantennography ; Gas chromatography ; Mass spectrometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé L'analyse en chromatographie gazeuse associée à une détection électroantennographique a montré que l'acétate (Z,E)-9,11-tétradécadiényle (Z,E)-9,11–14:Ac est l'un des composants de la phéromone de Dioryctria abietella Schiff (Lepid.: Pyralidae). Couplage chromatographie en phase gazeuse spectrometrie de masse a montré la présence d'acétate tétradécadiényle avec un spectre de masse et un indice de rétention identiques au Z,E-9,11–14:Ac Un récepteur cellulaire sensible à la fois au Z,E-9,11–14:Ac et à un extrait de la femelle a été identifié sous l'antenne du mâle. Les analyses des antennogrammes et de la cellule isolée ont étayé la caractérisation du composant de la phéromone comme étant Z,E-9,11–14:Ac. Un récepteur cellulaire additionnel sensible à l'acétate (Z.)-9-tétradécadiényle et à l'acétate (Z.E.)-9,12-tétradécadiényle a été trouvé sur l'antenne du mâle, mais il n'était pas activé par l'extrait de la femelle. Sur le terrain Z,E-9,11–14:Ac, présenté seul, attirait des nombres importants de mâles de D. abietella. L'addition de l'acétate (Z)-9-tétradécényle a inhibé l'attraction des mâles par les pièges.
    Notizen: Summary Gas chromatographic analyses coupled with electro-antennographic detection indicated that (Z,E)-9,11-tetradecadienyl acetate (Z,E-9, 11–14:Ac) is a pheromone component of the cone pyralid Dioryctria abietella. Gas chromatographic-mass spectrometric analyses confirmed the presence of a tetradecadienyl acetate with mass spectrum and retention index identical to Z,E-9,11–14:Ac. A receptor cell sensitive to both Z,E-9,11–14:Ac and the female extract was identified on the male antenna. An additional receptor cell sensitive to (Z)-9-tetradecenyl acetate and (Z,E)-9,12-tetradecadienyl acetate was found on the male antenna but was not activated by the female extract. In the field Z,E-9,11–14:Ac presented alone attracted significant numbers of male D. abietella. Addition of (Z)-9-tetradecenyl acetate inhibited the attraction of males to traps.
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 13 (1980), S. 651-660 
    ISSN: 1612-1112
    Schlagwort(e): Capillary columns, glass ; Gas chromatography ; Column preparation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Glass capillary column chromatography is the most rapidly growing part of gas chromatography. There are many complex new analytical tasks and they require special capillary columns. Fortunately there is a wide range of column preparation methods available, and they make the preparation of glass capillary columns a more varied job than that of packed columns. In this paper these methods are reviewed and suggestions are given for making task-oriented columns.
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  • 5
    ISSN: 1612-1112
    Schlagwort(e): Configuration ; Chiral phases ; Gas chromatography ; Isovaline
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The D-(resp. R) configuration of isovaline (=2-ethylalanine) was proved for the peptide antibiotics antiamoebin, Tü 165 (CBS 382.62), stilbellin, samarosporin (=emerimicin IV), suzukacillin B (A), trichotoxin A-40 and A-50. This contradicts the previously reported L-configuration for isovaline in antiamoebin and emerimicin IV. The configuration was determined by GC of the N-trifluoroacetyl-isovaline n-propyl ester on glass capillary columns coated with the chiral stationary phase N-propionyl-L-valine tert.-butylamide polysiloxane (Chirasil Val). The D-configuration of the isovaline from trichotoxin A-40 was also established independently using GC of N-pentafluoro-propionyl-isovaline (+)-3-methyl-2-butyl esters on glass capillary columns coated with OV 17.
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 601-602 
    ISSN: 1612-1112
    Schlagwort(e): Ethanolamines ; Ethylene glycols ; Direct separation ; Gas chromatography ; Short glass capillaries
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An effective and rapid GC separation of ethanolamines, even in the presence of ethylene glycols, using short glass capillary columns is developed. No preliminary derivatisation of the sample is necessary. The separation is completed in 6 minutes.
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 143-147 
    ISSN: 1612-1112
    Schlagwort(e): Capillary columns ; Gas chromatography ; Retention index ; Structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention index of twenty different homologous series of esters have been determined experimentally on polar (Carbowax 1540) and non-polar (squalane) columns. General equations to calculate retention index have been established by statistical methods. The influence of the length and inductive effect of acid and alcohol chains and the relative position of the carboxylic group are discussed.
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 285-288 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Porous layer open tubular columns ; Kaolin as support ; Column performance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary PLOT columns have been prepared with kaolin as the liquid phase support. These columns show good efficiency with different stationary phases and good thermal stability with polar phases. The performance of columns is shown by the separation of various mixtures such as fatty acids, phenols and anilines which are of analytical importance.
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  • 9
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Urea herbicides ; Catalytic hydrolysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method is described for the rapid catalytic hydrolysis of phenylurea herbicides on silica gel at elevated temperatures. After derivatisation of the anilines produced with heptafluorobutyric acid anhydride final analysis is done on a gas chromatograph equipped with an electroncapture detector. Detection limits are in the 1–5 picogram range. The method has successfully been applied to residue analysis of water samples at the 1 ppb level. The determination of free anilines present in water samples and the potential of various techniques to be used to discriminate between free anilines and parent herbicides are also discussed.
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  • 10
    ISSN: 1612-1112
    Schlagwort(e): Teflon capillary columns ; Chemically modified teflon ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The preparation of teflon capillary columns employing direct coating of the stationary phase to the chemically modified teflon surface and the role of the chemically modified teflon in the separation mechanism are described. Two types of contributions from the modified teflon have been observed: nonspecific adsorption of the carbon surface and specific interactions of polar groups in the carbon skeleton. The use of polar liquid phases can eliminate adsorption due to the presence of polar groups in the modified teflon.
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  • 11
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Van der Waals' volume ; Polarity of stationary phase ; Retention index
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Equations for Retention Index (I) versus Van der Waals, volume (Vw) on squalane are studied for alcohols, carbonyls, esters and ethers. Each equation includes linear and branching substances with different positions of the functional group in the carbon chain. The study is extended to stationary phases with polarities from 4.29 to 91.54 on the Tarjan et al. scale. Variations of the slope and origin ordinate values with the polarity of the stationary phase are discussed.
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 125-132 
    ISSN: 1612-1112
    Schlagwort(e): Capillary columns ; Fast analysis ; Gas chromatography ; Instrumental effects ; Optimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The efficiency of fast GC columns depends largely on the quality of the chromatograph. A theoretical and experimental study shows the relative importance of the various phenomena involved and permits the optimization of a GC System. Extremely good performances, exceeding 2,500 plates per second have been routinely obtained.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 351-354 
    ISSN: 1612-1112
    Schlagwort(e): Supported catalysts ; Reserved-flow GC ; Drying step ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Application of reversed-flow gas chromatography to study the drying step in the preparation of supported catalysts is proposed. It is demonstrated that this technique can be applied to investigate the kinetic law followed, as well as to obtain kinetic parameters of drying (rate constants, activation energies and frequency factors). Amaterial illustrating this application is γ-Al2O3 impregnated with usual organic solvents (n-C5H12,n-C6H14,n-C7H16, CH3COCH3 and CH3CH2OH). It was found that in all cases above a simple first-order law based onone kind of active site is followed. Moreover, it was observed that the activation energyE a of the drying process increases almost linearly with the relative molecular mass of the solvent, whereas for the same solventE a increases with the amount used. The operation of a kinetic compensation effect suggests “similar” activated complexes of the various solvents used.
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 569-574 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Capillary columns ; Fused silica capillaries ; Capillary drawing ; Glass capillaries
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A compact description is given of a simple and reliable method of drawing flexible fused silica capillary for gas chromatography. Some emphasis is given to the fact that the practices of drawing optical fibres should not be followed too slavishly so this leads to unnecessarily complicated and expensive equipment. Satisfactory capillary column silica tubing can be made with straightfoward extension of the method developed earlier for drawing thick walled capillary. A simple glass/silica hydrogen oxygen diffusion flame bumer is described for fusing the preform tubing at the draw point which is enclosed by a water cooled glass enclosure to trap evaporated silica and maintain the operation under dust free conditions. The uniformity of the capillary diameter is better than 5% which is adequate for most gas chromatographic purposes. The second part of the paper yet to be published will cover the methods developed for coating the capillary both internally and externally.
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 13 (1980), S. 567-571 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Helium detector
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Four main factors which determine the shape and the polarity of the helium detector signal are discussed. All possible responses of this detector, both in elution and in vacancy chromatography, are presented and special attention is drawn to the intermediate region. The idea of ionization vacancy is introduced for the specific case of two components which are unresolved by the column and to which the detector responds with different sensitivity.
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 13 (1980), S. 574-575 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Xylenol isomers ; Sugar derivatives as liquid phases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Adenosine, guanosine and inosine used as liquid phases in gas chromatography permits the separation of all six xylenol isomers.
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  • 17
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Polycyclic aromatic hydrocarbons ; Retention index ; Average molecular polarizabilities
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A significant correlation has been found between the retention indices of polycyclic aromatic hydrocarbons on non-polar stationary phases and the average molecular polarizabilities of the molecules separated on these phases. Equations have been derived for the determination of the average molecular polarizabilities, directly from the retention indices.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 69-72 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Polynuclear aromatic hydrocarbons ; Retention index ; Vapour pressure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention index of a planar polynuclear aromatic hydrocarbon on the GC phases OV-101, SE-52, and OV-17 is strictly related only to the boiling point, and less closely to the relative molecular mass. The very approximates relation with connectivity index ins only a consequence of the latter. On a nematic lqiuid crystal phase, a variation of activity coefficient, expressed in terms of a shape factor, also influences the retention of PAH.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 269-276 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Detector performance ; Trace analysis ; Catalytic conversion ; Multidimensional gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Relationships are derived describing how the detection limit of a chromatographic system depends on the minimum detectable limit of the detector and the chromatographic parameters such as column length, efficiency, carrier gas flow rate and the capacity factor. Performance data of detectors developed in the last 25 years at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences are given and a few selected application examples are listed. These include trace analysis by preconcentration and by direct analysis and the utilization of multidimensional gas chromatography with two columns, two detectors, a 12-port valve, and a catalytic conversion reactor.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 277-278 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; C1−C5 Hydrocarbons ; Dimethyl ether
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An analytical GC method was developed which uses a single packed column consisting of three packings in series prepared with the following liquid phases: dimethyl sulfolane, propylene carbonate, and silver nitrate. This system provides satisfactory resolution of mixtures of C1−C5 hydrocarbons and dimethyl ether obtained when converting methanol to gasoline. Due to the high capacity of the column it is possible to inject larger sample amounts permitting trace analysis.
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  • 21
    ISSN: 1612-1112
    Schlagwort(e): Phthalides ; Umbelliferae ; Liquid-solid chromatography ; Gas chromatography ; Ligustilide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A liquid-solid chromatographic pre-fractionation of naturally occurring phthalides has been developed. The LSC was carried out on a column of silica applying a 1–50% gradient elution of diethyl ether (containing 2% methanol) in pentane. The enrichment in the fractions led to better possibilities for a gas chromatographic separation and isolation allowing further studies by spectroscopic methods. Ligustilide may easily isomerize during GC as a result of ageing of the column.
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 30-32 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Arsenic ; Inorganic materials
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method is described for the quantitative chlorination and extraction of arsenic as arsenic trichloride from a number of alloys. The conditions for the quantitative gas chromatographic measurement of the volatile chloride have been studied. The proposed method for inorganic materials is very fast giving results within 10 min; sensitive, 1.5·10−13 g As can be detected, simple and accurate. At the ng level of As the error is about 20% with a standard deviation less than 20%, and at the 10pg level the error is about 36% with a standard deviation of 44%.
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 765-768 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Preparative scale chromatography ; Capacity ; Dual-stage separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The capacity of different versions of single- and dual-stage separation of mixtures on a preparative scale is considered. It has been shown that dual-stage separation with intermediate condensation considerably enhances the capacity of the installation as compared with a single-stage process.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 117-124 
    ISSN: 1612-1112
    Schlagwort(e): Various packed GC column ; Gas chromatography ; Porous layer beads ; GC/MS analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Theoretical comparisons of various packed GC column types are presented with respect to analysis time, efficiency, sample dilution, and sample capacity for a given maximum inlet pressure. In particular, totally porous particles, porous layer beads, and glass beads are compared with one another. It is shown that 30 μm porous layer beads offer a useful compromise between analysis time and plate count with relatively good sample capacity. Moreover, when using 1 mm i.d. columns (microbore), outlet flow rates that are reasonable for direct coupling to magnetic sector mass spectrometers are achieved making these columns suitable for GC/MS. Using 30 μm Zipax porous layer beads, columns yielding 8,000 to 10,000 plates/meter have been produced with inlet pressures of 13 to 26 atm. A simple modification of the injection port converts the maximum inlet pressure of a commercial gas chromatograph to 26 atm. With such pressures, columns in excess of 20,000 plates can be achieved. Chromatograms are presented illustrating the promise of these microbore columns for GC and GC/MS analysis.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 245-248 
    ISSN: 1612-1112
    Schlagwort(e): Chromatoscopy ; Gas chromatography ; Graphitized carbon black ; Molecular structure and retention ; Aromatic hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A molecular-statistical calculation of the retention volumes at zero sample size on graphitized thermal carbon black is carried out for quasi-rigid molecules of fluorene, indene, 1-methylindene, 2-methylindene and three dimethylindenes. A reasonable agreement is observed between the calculated and the available experimental gas chromatographic data. The potential barrier to internal rotation and the torsional angle in styrene molecules are estimated by comparing theoretically calculated and measured retention volumes.
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  • 26
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Silicone liquid phases ; Oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The on-column oxidation of apolar and polar silicones used as gas chromatographic stationary phases is investigated. Even at 225° the effects of oxidation are found to be slight. Of the materials investigated the methylphenylsilicones are the most stable.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 505-508 
    ISSN: 1612-1112
    Schlagwort(e): Glass capillary ; Gas chromatography ; Methyl chloroacetates ; Methyl chloropropanoates ; Methyl chlorobutanoates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The gas chromatography of all chlorinated methyl acetates, methyl propanoates and methyl mono- and dichlorobutanoates has been studied on Carbowax 20M and SE-30 glass capillary columns under various running conditions. The order of elution on a non-polar column was largely determined by the boiling point of esters, whereas on a polar column it was much influenced by the structure of compounds. Complete separation of the combined mixture of all 27 compounds could not be achieved, however, methyl 3,3-dichlorobutanoate was the only ester overlapped on both columns in spite of the various column temperatures used. The best separation of the mixture was on Carbowax 20M with a temperature program from 50°C at 8°C/min, isothermal running conditions leading either to poor separation of volatile components or long analysis time and broad peaks of higher chlorinated esters. The relative retention times for compounds at the various column temperatures are given and the retention order on a polar and on a non-polar column discussed.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 517-520 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Carbon-silica adsorbents ; n-Octadecanol film ; Phase transitions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The properties of the n-octadecanol film on carbon-silica adsorbent (Carbosil) were investigated. It was found that n-octadecanol forms an oriented film on the Carbosil's surface. If the surface of the basic silica gel is not completely covered with carbon, then the phase transition takes place in this film at a temperature higher than the melting temperature of n-octadecanol. One may distinguish two forms of this film, characterised by the different structures and the temperatures of the phase transitions. The first exists on the surface of silica gel unblocked by carbon. This part of the film is a monolayer, in which the alcohol molecules are vertically oriented. The solid compact-liquid expanded type phase transition at the well-defined temperature occurs in this film. In the second part of the film formed on the carbon surface, there is a multilayer of n-octadecanol. Its molecules are probably parallely oriented in relationship to the adsorbent surface. This film desintegrates progressively when the temperature increase. Maximum temperature of this phase transition is lower than the temperature of its analogue on pure silica gel surface.
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 546-558 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Capillary columns ; Quantitative analysis ; Sample inlet systems ; High-speed analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The attainment of precise quatitative analytical data using open-tubular (capillary) columns in standard, commercially available gas chromatographic instrumentation is demonstrated. Key elements in the design and proper utilization of the instrumentation are discussed. The function of the various sample introduction systems is elaborated and their quantitative performance demonstrated. The extra-column contribution to band-spreading is determined and the resultant data is used assessing the suitability of commercial instrumentation for highspeed capillary gas chromatography. The quantitative analysis of a sample containing some eleven components in less than thirty seconds is shown.
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  • 30
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Crystal hydrates as stationary phases ; Mobile Phases containing water ; Selective retentions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The use of crystallohydrates, crystallohydrate solutions and melts as stationary phases in gas chromatography has been proposed. Crystallohydrates have been shown to display high selectivity in the separation of polar organic compounds when use is made of water vapours as the mobile phase. Some aspects of gas-liquid chromatography in water vapours and with the stationary phase comprising crystallohydrates have been studied, and the preliminary results obtained point to the desirability of further progress in this field.
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 16 (1982), S. 201-203 
    ISSN: 1612-1112
    Schlagwort(e): Phenols ; Whisky ; Gas chromatography ; Aroma compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Twelve volatile phenols were identified in whisky by combined gas chromatography-mass spectrometry. Of these phenols 2,4-dimethylphenol was found for the first time in the aroma of whisky. The content of phenol, o-, m-, and p-cresol, guaiacol, p-ethylphenol, p-ethylguaiacol and eugenol in whiskies originating from different countries was determined by gas chromatography as their 2,4-dinitrophenyl ethers using electron capture detection. The results show that Scotch whiskies differ from others in the content of o-, m-, and p-cresol. The odour threshold values of phenols studied were determined in a 10% (v/v) ethanol-water mixture and in some cases also in the whiskies. Cresols have been found to make contribution to the aroma of Scotch whisky.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 16 (1982), S. 26-31 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Ionization detectors ; Gaia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary This paper is an account of the development of the gaia hypothesis as seen through the eyes of a gas chromatographer. Gaia is a radical notion about the Earth which postulates the climate and chemical composition to be regulated at an optimum by and for life. Gas chromatography played an important role in the gathering of evidence for the hypothesis but most significantly the art of inventing detectors lead to the developement of a planetary life detector through which gaia was revealed.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 16 (1982), S. 282-285 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Naphtha analysis ; Gasoline analysis ; Hydrocarbon type analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Two different gas chromatographic methods are used for the determination of hydrocarbon type distribution in naphtha and gasoline samples with final boiling points up to 275 °C. The methods are based either on a single capillary column or on a valve-switched packed column system. Both methods give extensive information on paraffins, olefins, naphthenes and aromatics in total as well as by carbon-number. In each case the analysis is fully automated with a computer controlling the entire analysis from injection to results presentation. The advantages and limitations of both methods are discussed.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 16 (1982), S. 322-324 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Graphitized carbon black supports ; Determination of hydroxyacids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Acid-washed graphitized carbon black (Carbopakc B) modified with trimesic adic and PEG 20M has proved to be effective for quantitative analysis of underivatized low molecular weight hydroxyacids. Calibration data revealed good linear relationships between relative peak area and concentration for lactic and 3-hydroxybutyric acids down to 0.05 mmol/l. The packing material was suitable for the analysis of aqueous solutions of hydroxyacids as it is tolerant to injections of water over a prolonged period of use. The GC system developed has been applied to the analysis of some hydroxyacids of biomedical interest in blood plasma and lactic acid contained in wine and beer.
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  • 35
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Modified thermal energy analyzer ; Selective detection of nitrogen compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A modification to the TEATM Analyzer is described, which allows it to be used as a highly selective GC detector for nitrogen compounds as well as for N-nitrosamines and nitro compounds. The modified Analyzer is as sensitive as the AFID, but has a much higher selectivity towards nitrogen compounds than the AFID. Its response appears to be molar, with an output that is dependent only on the number of nitrogen atoms present. The performance of the modified Analyzer for the analysis of ammonia, amines,N-nitrosamines, nitriles and organonitro compounds is reported and discussed, as is its application to the detection of these compounds in bacon and beer samples.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 33-36 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Preparative scale chromatography ; Capacity ; Dual-step separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The capacity of dual-step preparative chromatographic separation systems is considered. It is shown that dualstep separation makes it possible to enhance the capacity of preparative installations as compared with single- and dual-stage purification of the compounds.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 44-46 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Natural gas analysis ; Poropak N
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A simple gas chromatographic method is described for the rapid analysis of natural gas using thermal conductivity detectors and programmed-temperature operation of a single Poropak N column. The method permits the determination of nitrogen, carbon dioxide and hydrocarbons containing one to seven carbon atoms.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 553-559 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Open-tubular (capillary) columns ; Immobilized liquid phases ; Thick-film columns ; Diffusion coefficients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The influence of the liquid phase film thickness in open-tubular (capillary) columns on the individual resistance-to-mass-transfer terms and on the overall column efficiency is examined from the theoretical point of view. Methods for the calculation of the diffusion coefficients are discussed.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 560-569 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Open-tubular (capillary) columns ; Immobilized liquid phases ; Thick-film columns ; GC-FTIR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The performance of a column prepared with an immobilized (chemically bonded) methylsilicone phase having a film thickness of 5μm is investigated in detail. Due to their high sample capacity, such columns are particularly useful when directly coupling gas chromatography with spectroscopic techniques such as Fourier-transform infrared spectroscopy. Thick-film columns can even be used with thermal conductivity detectors.
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 600-604 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Retention index ; Alkyl benzenes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The additivity concept in the retention index system of Kovats has been examined for a series ofn-alkylbenzenes and theiro- andp-monosubstituted nitro-, amino-, and chloro-derivatives. Anomalous behaviour is exhibited by the first three members of the series on both polar and non-polar stationary phases. For addition of a methylene group ton-propylbenzene or ap-substituted derivative, it is found that the retention increment, Δl CH2, approaches 100 units. However, the strong inductive effect of the group in the ortho position and the steric effects apparent in ano-substituted alkylbenzene lead to large variations of retention increment upon addition of-CH2-to the alkyl chain. A study ofn-alkylbenzene retention on Apiezon L and Carbowax 20M over a wide range of temperatures has verified the linearity of the retention increment with temperature and has revealed that this gradient increases with increasing carbon side-chain length for the first few members of the series, thereafter becoming constant. Functional retention increments, Δlx, for substitution of nitro-, amino- and chloro-groups into the benzene ring are given.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 691-692 
    ISSN: 1612-1112
    Schlagwort(e): Dichlorophenol isomers ; Sodium benzenesulfonate ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary It is difficult to separate all the dichlorophenol isomers as free phenols by gas-liquid chromatography. However they were effectively separated on 4,4′-dimethoxyazoxybenzene (liquid crystal), and all the isomers were separated appreciably well on sodium 1-naphthalenesulfonate, 2-naphthalenesulfonate and dodecylbenzenesulfonate.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 65-69 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Oxygenates ; Fused-silica capillary columns
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method of analysing gasolines that contain oxygenates has been developed. The method uses a single fusedsilica capillary column and gives quantitative data for the oxygenates and the hydrocarbons in one analysis.
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 75-78 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Trace analysis ; GC-concentration ; Enrichment factor ; Theoretical evaluation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Based on gas chromatographic retention data obtained on a given adsorbent and at a given trap efficiency at different temperatures new equations are proposed for the evaluation of the enrichment factor. These equations are suitable under various preconcentration conditions such as: equilibrium saturation, complete trapping and permissible losses. Compared to known expressions for the evaluation of the enrichment factor the equations suggested consider the band broadening of the impurity in a trap causing a loss of the substance at the adsorption stage and dilution of the sample during desorption when the desorbed impurities are directed into the gas chromatographic column without intermediate freezing out in an graphic column without intermediate freezing out in an empty tube. The new equations may be used to select the optimum preconcentration conditions providing the necessary sensitivity.
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  • 44
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Electron-capture ; Thermal-energy electrons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The products resulting from the reaction between thermal energy electrons and organic compounds have been investigated to further our knowledge of the mode of action of the electron-capture detector. Thermal energy electrons were generated by maintaining a corona discharge between a stainless steel cathode and a silver/silver chloride anode. The effects of electrode geometry, gas composition, gas flow rate, and the physical properties of the test substances were investigated. The design of the reactor was modified to minimize losses of unchanged substrate. Reaction products of benzaldehyde, tolualdehydes, chlorobenzaldehydes, and dichlorobenzenes were identified by combined gas chromatography — mass spectrometry.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 20 (1985), S. 195-196 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Wide-bore capillaries
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 191-194 
    ISSN: 1612-1112
    Schlagwort(e): Thermal treatment of MgO and MgCO3 ; Adsorption properties ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The changes in the chromatographic properties of MgO and MgCO3 due to thermal treatment was investigated. The experimental results show that thermally treated MgO and MgCO3 can be used as stationary phase for the gas-adsorption chromatography of hydrocarbon mixtures.
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 20 (1985), S. 308-312 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Silica surface modification ; Hexamethylcyclotrisilazane ; Hexamethyldisilazane ; Support materials
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary For chromatographic purposes the use of mixtures instead of individual silylating agents can produce better deactivated surface than those shown by silicas modified by hexamethylcyclotrisilazane or hexamethyldisilazane separately.
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 20 (1985), S. 343-346 
    ISSN: 1612-1112
    Schlagwort(e): Thermosorb ; Tenax GC ; Environmental Analysis ; Trace Organics ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A preliminary study has been carried out to evaluate a new adsorbent, Thermosorb, for trace level organic contaminants. For this purpose, a comparison was made with a well-characterized adsorbent, Tenax GC, using a prepared aqueous solution of trace organic components. In addition, a comparison was made of chromatograms of air contaminants obtained using both of these adsorbents, under equivalent conditions. The results clearly indicated the potential of this thermally stable, inorganic adsorbent for many trace organic substances of environmental interest.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 20 (1985), S. 371-375 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Flame photometric detector ; Sulphur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The effect of experimental conditions such as gas flow rates, detector and column temperatures on sulphur response are discussed. It is concluded that the response of the flame photometric detector is affected by the O/H ratio and the total gas flow. Column temperature has an important influence upon S2 emission. It is shown that the sulphur response of the FPD is dependent on the compound containing the sulphur.
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 20 (1985), S. 538-542 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Fluidized beds ; Industrial chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Chromatography is carried out under the conditions of fluidization, in long, straight tubes under organized and non-organized conditions. Under non-organized conditions the column is filled only with a sorbent. In organized conditions, either metal coils are added into the column or a segmented column is utilized with metal grids. The results obtained are compared to those obtained under fixed-bed conditions when the column is completely filled with the sorbent. Organized fluidized beds provide a significant decrease in longitudinal bandspreading.
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  • 51
    ISSN: 1612-1112
    Schlagwort(e): Esterification in aqueous solution ; n-Butyl esters of fatty acids ; Gas chromatography ; Fatty acid analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The esterification of C1−C8 fatty acid in aqueous solutions and in the presence of sulfuric or hydrochloric acid and with n-butanol is described. It has been established that the esterification can be used for the quantitative determination of these fatty acids in the concentration ratio range of [H2O]/[n-BuOH]=0.01–5.3. In the concentration ratio range of 0.01–0.8 the water present does not interfere. In the concentration range of above 0.8 anhydrous sodium sulfate is used for binding the water, in the amount of [Na2SO4.anh.]/[H2O]≥0.2.
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  • 52
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Preparation of methyl esters ; Tetramethylammonium hydroxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Tetramethylammonium hydroxide in methanol has been proposed as a catalyst for preparing methyl esters of both free fatty acids and glycerides of fats. Nevertheless, procedures normally recognized as suitable can be inadequate when the fat under study contains noticeable amounts of low relative molecular mass esters. The method using tetramethylammonium hydroxide has been examined and modified in order to analyze milk fats by capillary GC. The pyrolysis methylation of free fatty acids in capillary injectors has been also studied. The modified method was satisfactory for both neutral and acid milk fats.
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  • 53
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Linear temperature programming ; Thermodynamic chracteristics ; Calculation of k PT ′ for LPTGC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A simple method has been elaborated to calculate capacity ratios under programmed-temperature conditions (k PT ′ ) from the thermodynamic characteristics determined for the given column under isothermal conditions and the parameters of programmed-temperature operations.
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 21 (1986), S. 110-112 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Nitrochlorobenzene isomers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An efficient, reproducible and rapid gas chromatographic method for the analysis of nitrochlorobenzenes has been described in this paper. The method uses FFAP as stationary phase and 3,4-dichloronitrobenzene as internal standard. The total analysis time of the method is less than 15 minutes with a coefficient of variation ranging from 0.41% to 1.19% for different levels of three isomers.
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 21 (1986), S. 149-151 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Retention indices ; Comparison of data ; Alkenes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Gas chromatographic retention indices for 47 C5 to C8 alkenes on OV-101 dimethylsilicone at 50 and 70 °C were determined within a standard deviation of 0.3i.u. Data obtained on OV-101 are compared with those measured on squalane. The comparison of the retention index and dl/dT values from both columns is presented as linear regression equations with correlation coefficients greater than 0.98.
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 21 (1986), S. 157-160 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Alkylation ; Carboxylic acids ; Urine analysis ; Micelles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Carboxylic acids can be converted to their methyl esters in an aqueous sample which contains no organic solvent. The reaction appears to be assisted by the presence of a quaternary ammonium salt surfactant. The procedure is best described as a pseudo-organic phase, or micelle-like, reaction. The important experimental variables have been optimized by Simplex procedures. The reaction proceeds in 80–100% yield, for common carboxylic acids, at room temperature in less than one hour. This reaction is superior to existing two-phase extractive alkylation procedures.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 472-476 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Liquid stationary phase ; Liquid phase bleeding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The theory of the evaporation of the liquid stationary phase is elaborated and experimentally verified. On the basis of this theory the role played by the losses in the amount of liquid phase present is quantitatively determined. General techniques are examined which minimize the losses; these techniques are based on saturating the incoming carrier gas with liquid phase vapours and raising the pressure of the carrier gas in the column, e.g. by connecting a capillary to the column outlet in order to offer resistance to the gas flow. The application of these techniques ensures stable performance of the gas chromatographic columns using a volatile liquid phase.
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 493-500 
    ISSN: 1612-1112
    Schlagwort(e): Esterification in aqueous solution ; iso butyl esters of C1–C20 fatty acids ; Gas chromatography ; Fatty acid analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary C1–C20 carboxylic acids have been esterified in aqueous solutions with i-butanol. Gas chromatographic analyses have been performed from a single chromatogram. It has been established that esterification in the concentration range of [H2O]/[i-BuOH]=0.01–10.3 can be utilized for the quantitative determination of these carboxylic acids. The presence of water does not interfere in the range of [H2O]/[i-BuOH]=0.01–1.03. In the cases of [H2O]/[i-BuOH]〉1.03, anhydrous sodium sulfate has been used for binding the water, in an amount of [Na2SO4]anh./[H2O]≥0.2.
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 21 (1986), S. 214-218 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Behaviour of metal acetylacetonates ; Adsorption isotherms ; Heat of solution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Specific retention volumes, adsorption isotherms, molar heats of solution and changes of the entropy were determined from chromatographic data, which was obtained by the gas chromatographic separation of metal acetylacetonates. The retention data for Cr(III), Co(III) and Al(III) acetylacetonates were measured at different temperatures and different flow rates. From the retention data other values associated with adsorption and solution phenomena were calculated.
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 11-14 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Cross-linked Stationary phase ; Immobilized Stationary phase ; Packed columns ; Trapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A coating of silicone SE-54 on Chromosorb W has been converted to an analytically stable, immobilized stationary phase layer by cross-linking with an organic peroxide. Up to 10% by weight has been applied in this manner. Excellent high temperature qualities are exhibited, such as low bleeding and good base line stability, during typical analyses. Poly (2,6-dimethyl-p-phenylene oxide) has also been crosslinked as a surface coating on Chromosorb W with an organic peroxide. From 3 to 4% by weight has been immobilized in this way. The resultant packing material, following high temperature conditioning, has been examined for use as an adsorbent of trace substances, similar to the applications to which such adsorbents as Tenax GC have commonly been applied, e.g. trace analysis of air. It appears to exhibit satisfactory properties for this analytical purpose.
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 21-22 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Isopropylidene-glucose ; Glucose ; GC of TMS-derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary This paper describes the gas chromatographic separation of the mixture of di- and mono-O-isopropylidene-D-glucose and D-glucose as their trimethylsilyl derivatives. The use of OV-101 as liquid phase provides a complete separation for the all components in the mixture. Quantative analysis was performed using xylitol as the internal standard for di- and mono-O-isopropylidene-D-glucose, and sorbitol as the internal standard for α-and β-glucose.
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  • 62
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Nuclear magnetic resonance ; Terpenes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A procedure is described for recording1H NMR spectra of flowing gaseous GC fractions boiling as high as 200°C. The line width of the signals in the NMR spectra is smaller than 2.2Hz.
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 556-559 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Liquid chromatography ; Tetramethrin ; Residues
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method is described for the analysis of tetramethrin aqueous formulation and residues of tetramethrin on woolen cloth. The samples were extracted with acetonitrile and partitioned with benzene. Interferences were removed by liquid column chromatography with acid alumina and eluted with 10% ethyl acetate-hexane. Analysis was by gas chromatography with a 10% UCW98 (methylsilicone) column. Detection was made with the flame ionization detector to avoid the repeated dilutions necessary with use of the electron capture detector.
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 615-618 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Retention index ; Electric parameters ; Physico-chemical relationships ; Structure-retention study
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new equation is derived relating the retention index to the molecular polarizabilities, ionization potentials and permanent dipole moments of the stationary phase and the solute. Various implications of this equation to quantitative structure-retention relationships are discussed.
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 278-282 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Mixed phases ; Chlorinated C1−C3 hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method to establish the optimum composition of mixed stationary phases used in GC is given for the case when only the retention times on the individual phases are known. The method has been empirically tested for the resolution of chlorinated C1−C3 hydrocarbons.
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 303-306 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Nitrogen-selective detector ; Flash methylation ; Morphine ; Blood analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A simplified gas chromatographic method for the rapid determination of morphinn in rat and human blood is described. After single extraction, morphine was reconstituded in trimethylanilinium hydroxide and introduced directly into a gas chromatograph equipped with a nitrogen specific flame ionization detector. Limits of detection were 0.5μg/ml for either water or blood solutions. Analytical recoveries of morphine, added to either water or blood were 88±6 and 90±3% $$(\bar x \pm SD)$$ , respectively, when compared with morphine dissolved in methanol. The between-run coefficients of variation were 5.0 and 5.4% for water and blood, respectively, over the range of 0.5–32.2μg/ml, whereas the within-run coefficients of variation at 1μg/ml were 8.1 and 7.9%, respectively. The application of the method to an in vivo animal experiment is demonstrated.
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 333-336 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Split sampling ; PTV-sampling ; Discrimination ; Quantitation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Parallel studies on split-sampling and PTV-sampling procedures have been made to highlight the difficulties in quantitative analysis for capillary columns. Parameters such as total sample amount, carrier gas and packing material used for the injector glass insert were studied. The results clearly demonstrate the importance of optimizing all experimental parameters which give rise to discrimination effects during injection.
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 329-332 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Esterification in aqueous solution ; n-propyl esters of C1−C22 fatty acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary C1−C22 carboxylic acids have been esterified in aqueous solution with n-propanol. Gas chromatographic analyses have been performed from a single chromatogram. It has been proven that esterification in the concentration range of [H2O]/[n-PrOH]=0.022–8.45 can be utilized for the quantitative determination of these carboxylic acids. The presence of water does not interfere in the range of [H2O]/[n-PrOH]=0.22–1.27. In the cases of [H2O]/[n-PrOH]〉1.27, anhydrous sodium sulfate has been used for binding the water, in an amount of [Na2SO4 anh.]/[H2O]〉0.7.
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 358-362 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Micropacked columns ; Quantitation ; Fermentation products
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new method is proposed for the analysis by gas chromatography of volatile compounds found in alcoholic and acetic fermentation samples. The method represents a suitable choice for the accurate and precise determination of 19 compounds (including Methanol) by direct injection onto a single column. Chromatograms of synthetic mixtures as well as actual samples show the capabilities of the micropacked column used.
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  • 70
    ISSN: 1612-1112
    Schlagwort(e): Aldehydes and ketones ; 2,4-dinitrophenylhydrazine-coated silica gel ; Gas chromatography ; Column liquid chromatography ; Pollution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary After a brief review of several methods described in the literature this paper discusses air-sampling on 2,4-dinitrophenylhydrazine-coated silica gel and identification requirements for aldehydes and ketones most commonly found in industrial pollution. Quantitative analysis of formaldehyde and acetaldehyde either by GC or by HPLC techniques is established using a dynamic system producing test atmospheres and compared with the usual colorimetric determinations.
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  • 71
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Esterification in aqueous solution ; n-Propyl esters of aromatic polycarboxylic acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The direct esterification and gas chromatographic analysis of aromatic carboxylic acids as n-propyl esters is described. Derivatization is performed in aqueous solution with n-propanol in the presence of sulfuric acid. The n-propyl esters of benzoic, phthalic, trimellitic and pyromellitic acids permit their gas chromatographic separation from each other and from fatty acids and aliphatic dicarboxylic acids. At mode ratios of [H2O]/[n-PrOH]≤0.03 the water present does not interfere with the esterification reaction. At mole ratios above 0.03 anhydrous sodium sulfate is used for binding the water, at mole ratios of [Na2SO4anh.]/[H2O]=0.51–1.52 and of [H2SO4]/[Na2SO4anh.]=0.43–1.28, respectively.
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  • 72
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 23 (1987), S. 790-795 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Capillary columns in series ; Variable polarity columns ; Essential oils analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary By connecting capillary columns of different polarity in series and by changing the temperature program gradient, a system of variable polarity is obtained. The working conditions can be adjusted to optimize separations of complex mixtures. Application to the analysis of essential oils of: lavender, thyme, lemon petit grain, bergamot, and tangerine, are reported.
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  • 73
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Aqueous samples ; Direct injection ; Traces of ketones and halogenated hydrocarbons ; Environmental analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Procedures for the quantitative analysis of industrial effluents which involve concentration by solvent extraction or the purge-and-trap method are time-consuming, labor-intensive, and prone to error. Direct aqueous injection gas chromatography using an electron-capture detector for the analysis of volatile halocarbons at the ppb level is in routine use in many laboratories. We now discuss the development of a similar protocol for the analysis of volatile polar organics such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and tretrahydrofuran using a flame-ionization detector.
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 23 (1987), S. 566-570 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Backflushing, peak-cutting technique ; Trace analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A backflusing, peak-cutting method was developed for the analysis of trace components present in the tail of a major component peak. Using a helium-ionization detector, the minimum detectable concentration (MDC) was: oxygen in hydrogen, 0.5ppm; nitrogen in oxygen or argon, 1ppm; and methane and carbon monoxide in nitrogen, 1ppm. The corresponding MDC values for the conventional single-column method were 7.2ppm, 8.3ppm, and 14 and 5ppm, respectively. Equations used to predict the retention time are given. The accuracy of the predicted retention time is about two percent compared to experimental results.
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  • 75
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Liquid crystals ; Substituted benzenes and selectivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention mechanisms of polymethylbenzenes and n-alkylbenzenes on the inert solid support Chromaton (spec-surface area: 1m2/g) and the adsorbent-support Silochrom (C-80 (80 m2/g) coated with p-n-butyl oxybenzoic acid have been investigated.
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 23 (1987), S. 547-552 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; FT-IR detection ; γ- and δ-Haloesters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The decomposition of γ- and δ-haloesters has previously been observed to take place within a commercial GC/FT-IR light-pipe system. Using a home-built light-pipe interface, an analysis of this same class of compounds was conducted from which the source of the decomposition was determined to be a brass fitting central to the commercial system's assembly. It is proposed that the reaction is due to a weakening of the carbon-halogen bond by metal interaction thereby allowing lactonization to occur.
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  • 77
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Liquid crystal ; Capillary columns ; Retention data ; Stationary phase film thickness ; Column surface quality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Glass capillary columns were prepared from non-deactivated and deactivated glass and coated with (2-methyl-4-[trans-4-n-propyl-cyclohexylcarbonyloxy]-benzoic acid-[4-n-heptyloxy-phenylester]) as the liqud phase, in different film thicknesses. The columns were tested using substances of different structures and polarities. It was verified that the capacity factors, retention indices and selectivity significantly depend on the thickness of the liquid crystalline stationary phase film and the quality of the tube, particularly in the case of columns with thin films. Trasition temperatures (melting and clearing point) of the liquid crystal are also dependent on these two factors.
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 25 (1988), S. 21-24 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Sample concentration ; Chromatographic evaporation ; Solvent effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Several micro-techniques for the removal of solvent from dilute solutions of volatile compounds have been compared. Large solute losses were experienced when the conventional blow-down technique was applied. Better yields could be obtained with static evaporation procedures, as long as an effective reflux was maintained. However, careful optimization of the vessel design and operating conditions is necessary. The most efficient volume reduction technique was shown to be chromatographic evaporation. Quantitative recoveries were obtained for the compounds tested and the process was significantly faster than static concentration. Moreover, operating conditions (gas flow, temperature) are less critical. With modifications, the principle can be used for the concentration of large sample volumes down to a few microliters.
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  • 79
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Preparative scale separations ; Plate model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Two close-boiling materials, diethyl ether (DEE) and dichloromethane (DCM), were separated to investigate the effects of the pure components and the mixture on elution in preparative gas-liquid chromatography. Nitrogen was used as the carrier gas, and the chromatographic column (1 cm I.D. and 0.75m length) was packed with Chromosorb A with different quantities of dinonyl phthalate stationary phase and particle sizes. Below ca. 7% (by wt.) of feed concentration, the experimental elution curves of pure DEE and DCM were almost the same as those of the mixture, and the theoretical plate model can be used successfully to predict the elution curves.
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  • 80
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Retention index ; Hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention of hydrocarbons present in the C5 pyrolysis fraction of gasolines on the stationary phases squalane and methylsilicone oil JXR at 30, 40 and 50°C was investigated by capillary gas chromatography. The unified retention indices of the hydrocarbons were also calculated on squalane. The retention indices obtained on these two phases were interrelated and the quantitative relationship with the structure of the solutes was studied. Equations based on the unified retention indices calculated on squalane and some selected structural elements of the solutes permit the calculation of their retention on methylsilicone with sufficient accuracy.
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  • 81
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 25 (1988), S. 404-408 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Silica surface modification ; Hexamethylcyclotrisilazane ; Hexamethyldisilazane ; Support materials
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The paper is concerned with the structure of an organic layer bonded to the silica surface modified with silazanes. The changes of the retention volumes of hydrocarbons is studied for the silicas modified with hexamethylcyclotrisilazane, hexamethyldisilazane and their mixtures. It is shown that most of the carbon in the layer after hexamethylcyclotrisilazane modification is bonded to the surface by Si−O−Si bonds. This fact supports the assumption of a fragmentation of the cyclosilane used for modification.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 25 (1988), S. 609-612 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Gas chromatography ; Triglyceride composition of grapes ; Identification system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The triglyceride composition of the Tempranillo grape (Vitis vinifera) has been examined by a combination of HPLC and GLC. To identify the triglycerides, equations were applied relating log k′ with the molecular variables: equivalent carbon number, chain length and number of double bonds in each of the fatty acids in the glycerides. Ten triglycerides were found, the principal ones being trilinolein (35.75%), dilinoleyl-olein (21.03%) and dilinoleyl-palmitin (17.02%).
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 25 (1988), S. 655-658 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Structure-retention relationships ; Connectivity indices, topological indices ; Alkenes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Retention indices of different alkenes are correlated with connectivity and topological parameters. The appropriate statistically valid relations hips are derived and discussed.
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 271-274 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Retention index calculation ; Epoxides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The separation of C6 epoxides on a glass capillary column coated with OV-101 dimethylsilicone liquid phase was investigated. Retention indices were determined at four temperatures between 60 and 90°C. Linear regression equations permit the pre-calculation of the retention indices and the dI/dT values of the C6 epoxides from their properties.
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 23 (1987), S. 50-52 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Retention indices ; C6 alkanols ; OV-101 ; Carbowax 20M
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Gas chromatographic retention indices for 16 C6 alkanols measured on capillary columns coated with OV-101 methylsilicone and Carbowax 20M propylethyleneglycol liquid phases at 80° and 90°C were determined. The respective standard deviation values were 0.5 and 0.8 i.u. The correlation between the retention indices measured on non-polar and polar stationary phases and the boiling points of the alkanols was studied.
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 26 (1988), S. 34-36 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Gas analysis in halogen lamps ; Sampling device
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new type of gas sampling device was constructed to improve the analysis of the gas in halogen lamps. Low levels of gases such as O2, CH4, C2H4 and CH3Br could be determined by the techniques worked out.
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  • 87
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 26 (1988), S. 229-233 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Glass capillaries ; Chirasil-Val ; Immobilisation ; Enantiomeric separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Immobilisation methods of the chiral silicone stationary phase Chirasil-L-Val have been studied. In addition to the standard techniques of radical-induced immobilisation with dicumyl peroxide and azo tert-butane, immobilisation was solely achieved by thermal treatment: conditioning at low flow-rates or under stop-flow conditions led to unexpectedly high immobilisation despite mild temperatures. The presence of water vapor in the carrier gas accelerated the immobilisation process. While up to 75% immobilisation was attainable with both ATB and thermal methods, immobilisation with DCUP did not exceed 50%, despite relatively high DCUP concentrations. Whilst all immobilisation methods were accompanied by varying degrees of racemisation at the chiral centre, it was possible to establish conditions that yielded a high immobilisation (in excess of 70%) with a negligible loss in enantiomeric selctivity. The immobilisation reactions also slightly affected the polarity of the stationary phase, reflected in a shift of the Kovats-Indices of amino acid derivatives and in the accompanying “Squalane-Effect”. With respect to immobilisation, racemisation and polarity shift, thermal immobilisation with water-saturated carrier gas proved to be the optimum method.
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 26 (1988), S. 383-386 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; On-line process analysis ; Injection of volatile compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A modified on-line liquid injection technique with rotary valves for gas chromatography has been developed. Applications for the on-line analysis of 2-methylpropene, cyclohexene and 1-butene are described. All samples were loaded under pressure. The results obtained show excellent reproducibility with less than 0.1% relative standard deviation (r.s.d.; n=6) for the peak areas measured. The method is particularly advantageous for samples containing both gas and liquid ccomponents at one bar.
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  • 89
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; FAME fingerprinting ; Animal fats ; Transesterification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The triglycerides of animal fats from milk, meat or cheese can also be characterized by the gaschromatographic pattern of the fatty acid methylesters (FAME) after conversion by an unsophisticated transesterification procedure. Even from the FAME pattern falsifications of commercial animal fats can be revealed by the fast separation of the FAME using a standard CW 20 M (polyethyleneglycol) capillary column. Characteristic patterns of FAME originating from different animals are shown. The patterns of the FAME from different races of the same animal are very similar, so that the characterisation according to the type of animal is not disturbed.
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 27 (1989), S. 596-600 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Mass spectrometry ; Azines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary We have studied the gas chromatographic behaviour of several 3-methyl-2-benzothiazolone-azines. In HPLC analysis all the unsymmetrical azines show double peaks, whereas in HRGC analysis only some of these compounds show the two peaks corresponding to the Z (syn) and E (anti) isomers. By means GC/MS analysis the mass spectrum of each azine was recorded. We have assigned the E and Z configurations to the first and second gas chromtographic peaks on the basis of the ratio between the relative abundances of the two most significant framment ions at m/z 163 and 164.
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 27 (1989), S. 221-224 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Large volume sample injection ; Closed on-column injector
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new simplified version of a “closed” on-column injector is introduced. Because of its design isobaric injection conditions do not have to be followed and a wide range of injection temperatures above the boiling point of the sample solvent can be chosen for on-column injections in capillary gas chromatography. Also, when following certain basic injection rules, injections of large sample volumes (≥20 μl or more) give accurate and reproducible results without further problems.
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 28 (1989), S. 139-142 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Silica surface ; Silanols ; Strongly interacting sites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The paper describes how the method of gas-phase titration of the strongest adsorption sites can be utilized to calculate a relative strength of interaction of the sites with chromatographic solutes. An excellent correlation with earlier, theoretical predictions of Giddings is noted. Significant influence of the sites on the width of a chromatographic band is observed when the interactions are an order of magnitude stronger than those of normal sites.
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 28 (1989), S. 167-169 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Determination of monomer in polymers ; Sealed glass capillary sampling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Residual styrene in polystyrene and free phenol in phenolic plywood adhesive have been determined by sealing samples in glass capillary tubes. To prevent loss of sample the ends of the capillary tubes were sealed with a kind of putty made of anhydrous calcium sulfare, calcium carbonate and a small quantity of phenylmethylsilicone fluid. No volatile compounds were released from this sealing material when the capillary tubes were placed in a quartz vaporising furnace at temperatures up to 300°C.
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 28 (1989), S. 237-240 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Slope of log plot ; Homologous series ; Retention index ; Retention time ; Uncertainty ; Free energy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The free energy of partition of a methylene group $$\Delta G_{CH_2 }^ \circ $$ is constant within a homologous series down to C5 and nearly constant to C3, contrary to the finding of Golovnya and Grigoryeva [5]. Retention indices are linear with carbon number: values may be extrapolated from higher carbon numbers to C5 within experimental uncertainty, to C4 with error no greater than 5 units and to C3 with error no greater than 10 units. Error in extrapolating the logarithm of the adjusted retention time, log t′R, to C5 is thus negligible, to C4 has possible error up to 5b/100 and to C3 up to 10b/100, whereb is the slope of the plot of log t′R against carbon number.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Optimization of gas-solid separations ; Plate height equation ; Computer mapping procedure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary This paper proposes an optimization model for gas-solid chromatographic separations in a non-linear programming form and an approximate equation of the plate height for the model. A computer-modified mapping procedure is also described for searching the optimum separation conditions. Just five experiments and about 20 minutes of the computer time are needed to establish the optima of column temperature and of the carrier gas linear velocity. The relative deviation between the predicted and the experimental values was found to be within 20% for the plate heights, and within 1.5% for the retention times.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 13 (1980), S. 61-67 
    ISSN: 1612-1112
    Schlagwort(e): Optimization ; Carrier gas velocity ; Gas chromatography ; Influence of temperature on optimum velocity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Zusammenfassung Die Wahl der mittleren, linearen Trägergasgeschwindigkeit bei der Analyse von Mehrkomponentengemischen unter isothermen und temperaturprogrammierten Bedingungen wird diskutiert. Es wird gezeigt, daß stets eine Trägergasgeschwindigkeit gewählt werden sollte, die mindestens gleich, besser jedoch höher ist, als die optimale Gasgeschwindigkeit für den ersten Peak, gemessen bei der Starttemperatur (Temperaturprogramm) oder bei der eingestellten Ofentemperatur (isotherme Fahrweise).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 13 (1980), S. 686-692 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Micropacked columns in GC ; Microparticles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Porous silica microparticles designed for modern liquid chromatography have proven effective in gas chromatography. Columns of 35–50 cm gave plate heights as low as 3.3 particle diameters and speeds of 2400 theoretical plates per second or 500 effective theoretical plates per second. Inlet pressures up to 70 atmospheres were required using hydrogen as carrier gas. The particles as received were too retentive for fast chromatography and gave asymmetric peaks. A coating of fluorosilicone oil overcame both problems. Other coatings were less effective. Bonded phases proved less satisfactory on both counts and also gave substantially less efficient columns and greater flow resistance. Column efficiency and flow resistance were sharply dependent on physical properties of the particles. The most efficient packing was clearly spherical particles of 5–10 μm diameter with narrow size distribution, pore diamters about 50 nm, BET surface areas of 25–50 m2/g and surfaces modified with trifluoropropyl silicone. A six-component hydrocarbon sample was separated in 33 s with a resolution of 4 for the most difficult pair and in 2.6 s with a minimal resolution. Performance was limited by end effects and by available pressure so that much better performance can be expected from longer columns and higher pressures.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 13 (1980), S. 752-754 
    ISSN: 1612-1112
    Schlagwort(e): Xylenol isomers ; Gas chromatography ; Polyols and polyethers as stationary phase ; Hydrogen bonding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Xylenol isomers can be resolved on most polyols (sugars or sugar alcohols) and polyethers (polyethylene glycol or polypropylene glycol) with hydrogen-bonding interaction. They are separated on vinical polyols which have more hydroxy hydrogen than tetrol, and even on vicinal triol when its hydroxy hydrogen is acidic (stronger proton donor). The stronger is the hydrogen bonding interaction between xylenols and the liquid phase, the better is the separation of 2,4- and 2,5-xylenol, and the poorer the separation of 2,4-and 2,3-xylenol.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 19-22 
    ISSN: 1612-1112
    Schlagwort(e): Teflon columns ; Chemically modified teflon ; Gas chromatography ; Capillary columns
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Wall-coated open tubular columns prepared from chemically modified teflon tubing have been developed for gas chromatography. Chemical reaction of the inner walls of teflon tubing allows bonding of an adhesive layer on which a variety of stationary phaes can be coated. Test mixtures of alkanes and alcohols were used to investigate the chromatographic properties of these columns and the stability and mixing of the adhesive and stationary phae layers. the results in dicate that mixing of the layers is negligible and that the column is stable for a long period of time.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 55-66 
    ISSN: 1612-1112
    Schlagwort(e): Capillary columns, glass ; Gas chromatography ; Column preparation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Kapillar-Gas-Chromatographie ist heute das sich am stärksten entwickelnde Gebiet der Gas-Chromatographie. Es gibt viele komplexe, neue Fragestellungen in der Analytik, welche den Einsatz spezieller Kapillarsäulen erfordem. Glücklicherweise gibt es aber auch eine große Zahl von Herstellungsverfahren für Kapillarsäulen, welche — noch mehr als bei der Herstellung von gepackten Säulen — eine Anpassung an die gestellten Aufgaben ermöglichen. In diesem Artikel werden die Herstellungsverfahren für Kapillarsäulen zusammengestellt und Anregungen gegeben, wie aufgaben-orientierte Säulen erreicht werden.
    Notizen: Summary Glass capillary column chromatography is the most rapidly growing part of gas chromatography. There are many complex new analytical tasks and they require special capillary columns, Fortunately there is a wide range of column preparation methods available, and they make the preparation of glass capillary columns a more varied job than that of packed columns. In this paper these methods are reviewed and suggestions are given for making task-oriented columns.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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