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  • Gas chromatography  (19)
  • Springer  (19)
  • National Academy of Sciences
  • 1975-1979  (19)
  • 1979  (19)
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Publisher
Years
  • 1975-1979  (19)
Year
  • 1979  (19)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 790-798 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Dead-time ; log ts=f(C) ; Retention index calculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung In der vorliegenden Arbeit wird eine Methode zur Retentionsindex-Bestimmung beschrieben, die von einem kubischen Zusammenhang zwischen Bruttoretentionszeit-Differenzen der Referenzhomologen und der Kohlenstoffzahl ausgeht. Hieraus ergeben sich direkt die Nettoretentionszeiten. Der Fehler der Totzeitbestimmung entfällt bei dieser Methode. Mit den so gewonnenen Nettoretentionszeiten erhält man über einen kubischen Zusammenhang zwischen 1g ts=f(C) die Retentionsindices. Extrapolationen und Interpolationen sind über 300 Retentionsindexeinheiten mit einem mittleren Fehler von ±0,02 Retentionsindexeinheiten möglich. Das Verfahren bietet sich für eine automatische Berechnung der I-Werte mittels on-line-Datenverarbeitung an.
    Notes: Summary The method for the calculation of retention indices described here is based on a third order relationship between the logarithm of differences of unadjusted retention times of homologues and the carbon number. From this adjusted retention times are directly calculated. A determination of the dead-time is not necessary thus avoiding the errors connected with this factor. A cubic equation for the logarithm of the adjusted retention time lg ts as a function of carbon number Cn is used for the retention index calculation. Extrapolations and interpolations can be done over a range of 300 index units with an average deviation of ±0.02 i.u.. The method offers the possibility of an automated on-line calculation of retention indices by computer merely on the basis of unadjusted retention times.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 523-526 
    ISSN: 1612-1112
    Keywords: Amantadine ; Gas chromatography ; Gas chromatography-mass spectrometry ; Biochemical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple, selective and sensitive method for the quantitation of amantadine in biological samples is described. After extraction from biological samples using a two-step procedure, amantadine is quantitatively converted into its isothiocyanate (NCS) derivative by treatment with carbon disulfide and then determined quantitatively using isobaric compounds, p-methoxyphenyl-ethylamine-NCS or N-acetylamantadine as external standards. The applicability of this method is illustrated by determining plasma levels of amantadine for pharmacokinetic studies and levels in dialysate samples of amantadine treated patients who were on dialysis machines.
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  • 3
    ISSN: 1612-1112
    Keywords: Polynuclear aromatic hydrocarbons ; Retention index ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An equation has been derived allowing to predict retention index values on nematic phases from computable parameters and sizes of the molecules of polycyclic aromatic hydrocarbons. Another equation, which has also been derived, allows to determine the shape parameter of a molecule from chromatographic data.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 583-586 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Clinical analysis ; Meningitis detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas liquid chromatography was performed on cerebrospinal fluid from cases of purulent meningitis, and control subject. A relatively constant pattern of peaks was obtained in all samples. Four constant peaks in the chromatogram frequently showed a significant increase in purulent meningitis but not in aseptic meningitis or control cases. There was a gradual return to normal levels during clinical improvement, usually within 5–6 days of appropriate therapy. In one case of recurrent meningitis, an increase in the peaks was noted with relapse. Identification of the compounds represented by these peaks may provide further information regarding diagnosis, prognosis and pathogenesis of meningitis.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 168-170 
    ISSN: 1612-1112
    Keywords: Acid catalyzed esterification ; Amino acids ; Fatty acids ; Gas chromatography ; Isopropyl esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Acid-catalyzed esterification of carboxyl groups with acetyl chloride in isopropanol is investigated. Yields are equivalent to those obtained with reagent prepared conventionally by bubbling gaseous hydrogen chloride into isopropanol. The preparation of the former reagent is less time consuming and no special equipment is needed. The procedure is applicable for other alcohols as well.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 533-538 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sorbents: liquid phases, supports, adsorbents ; Thermodynamical classification ; Polarity and selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Equations modifying Rohrschneider's relationship between ΔI and thermodynamical characteristics values are derived. Polarity in chromatography is discussed as a possibility of stationary phases or absorbents to enter into intermolecular interactions and is determined on the basis of the partial molar free energies of solution (ΔG) of six test substances. A simple method for the calculation of stationary phase polarity in terms of ΔG from retention indices and McReynolds constants is given. Equations are presented for the calculation of stationary phase selectivity utilizing ΔG data tabulated for selected test substances. The thermodynamical basis of selecting a reference phase for a unified system expressing the selectivity of stationary phases which can also be applied for adsorbents is suggested. The energy equivalent to an index unit, ΔGi.u., is discussed.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 803-807 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ionization detector ; High frequency discharge ; Specific or no specific detection ; Gas adsorption (by flues)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The response of a high frequency ionization detector according to various parameters: voltage, tuning capacitance, feed-back capacitance, space between the electrodes and direct flux-plasma distance is studied. The characteristic measure of v in accordance to high voltage for various mixtures of carrier gas argon-nitrogen gives a maximum which demonstrates that specific automatic analyses of oxygen, krypton and methane are possible with concentrations in the order of ppb. Complete adsorption of 0.8 ppb of methane by a flue of 120 cm in tube 2×4 mm at 50°C after twentieth recycling is essential.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 530-532 
    ISSN: 1612-1112
    Keywords: Hexetidine ; Triamine ; Gas chromatography ; On-column interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography was used for the direct assay of hexetidine and triamine in a pharmaceutical formulation. During this work we came across a strong oncolumn interaction, in such a way that the GLC retention, selectivity and response parameters were seriously modified relative to the injections of hexetidine and triamine standard solutions. The interaction was traced to the coinjected hydrochloride form of a major component of the sample and in practical terms points to the potential quantitation errors that may be associated to similar systems.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 665-671 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index ; Multiple correlation ; Molecular properties ; Prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Ein auf der linearen, multiplen Korrelation basierendes Verfahren wird vorgestellt, das es gestattet, den Retentionsindex von Substanzen in der gaschromatographischen Trennung aus einem Satz Säulenkonstanten und drei bis vier Substanzeigenschaften zu berechnen. Der Fehler der Berechnung liegt unter 2%. Der Ansatz wurde für isothermes und temperaturprogrammiertes Arbeiten getestet.
    Notes: Summary A method based on linear multiple correlation is introduced allowing the calculation of gas chromatographic retention indices from a set of column constants and three to four physical properties of the solute. The error is less than 2%. The formulation has been tested for isothermal and temperature programmed working conditions.
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  • 10
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Porous polymer supports ; Retention behaviour-effect of support
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The gas chromatographic behaviour of a series of compounds of different polarity on columns of Ethofat 60/25 on Chromosorb P HMDS (an inactive support) and Chromosorb 101 (an active support) was investigated. To observe how the support influences the chromatographic process, we separated the contribution to the retention volume of the interaction phenomena associated with the stationary phase, the solid support and the corresponding interfaces. In some cases the Chromosorb 101 exerts an influence on the process even with high percentages (〉10%) of stationary phase. The values of the experimental partition constants of a series of compounds and the factors that contribute to adsorption on these columns are calculated.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 733-736 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas volume, influence of ; Preconcentration ; Wine headspace analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Examination was made of the changes in composition of aroma volatiles trapped on Chromosorb 105 during dynamic headspace sampling of aged wine. Collections from different gas volumes were analysed and a subsequent collection made. It was demonstrated that analyses of headspace collections containing reduced quantities of the more volatile and more, hydrophobic compounds could aid in the identification and quantitative determination of alcoholic beverage components.
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  • 12
    ISSN: 1612-1112
    Keywords: Inclusion compound ; Urea-cetylalcohol adduct ; Gas chromatography ; Clathration process ; Phase changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Phase changes in urea-cetyl alcohol inclusion compounds prepared by various methods were monitored gas chromatographically. The decomposition temperature interval and the presence of the free components could be found from the temperature dependence of the retention data. Study of the clathration process yielded facts that can be used in the preparation of this type of inclusion compound.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 265-270 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Columns: open tubular ; Columns: capillary ; Efficiency ; Mean specific plate number
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new parameter, the mean specific plate number, is proposed for assessing the efficiency of support coated open tubular (SCOT) and wall coated open tubular (WCOT) columns and for comparing the efficiency of different open tubular columns. It has the advantage over most previously used parameters in that it has only a small dependence on the partition ratio and it allows for the column diameter. A graphical presentation is given of the maximum theoretical mean specific plate number as a function of the partition ratio for SCOT columns having a range of relative porous layer thicknesses and for WCOT columns with a range of phase ratios. This presentation permits ready visual comparison of the potential efficiency of different columns and enables a simple evaluation of the percentage utilization of theoretical efficiency from experimentally determined values of the maximum mean specific plate number. For a given column the percentage utilization of theoretical efficiency at optimum average gas velocity and that at optimum practical gas velocity or at a higher average gas velocity are shown to be equal provided that corrections for column pressure drop are made.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 463-466 
    ISSN: 1612-1112
    Keywords: Hydrothermal treatment of Porasils ; Adsorption properties ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple modification was employed by thermal or hydrothermal treatment of silica gel (Porasil). In this way chromatographic materials with advantageous properties were prepared. The changes of the adsorbent under different thermal and hydrothermal treatment were studied in more detail. The experimental results show that under controlled conditions material with required chromatographic properties can be prepared.
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  • 15
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ethanolamines ; Ethylene glycols ; Porapak Q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary GC separation of pure ethanolamines as well as mixtures with ethylene glycols, obtained from a real technological process is achived using Porapak Q coated with 15% Carbowax 20M. Symmetrical peaks, satisfactory resolution, and reasonable analysis times are obtained. The proposed method is suitable for a convenient, correct and express routine analysis.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 509-515 
    ISSN: 1612-1112
    Keywords: Optimization ; Carrier gas velocity ; Gas chromatography ; Influence of temperature on optimum velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The selection of the average linear carrier gas velocity in the analysis of a multicomponent mixture under isothermal and programmed-temperature conditions is discussed. It is shown that one shouls always select a velocity which is at least equal but preferably higher than the optimum average gas velocity of the earliest peak at the initial column temperature.
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  • 17
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index calculation ; lg ts=f(C) ; Dead-time ; Complex mixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die bisher in der Literatur beschriebenen Verfahren zur Retentionsindex-Bestimmung beruhen auf einem linearen Zusammenhang zwischen dem Logarithmus der Nettoretentionszeit lg ts und der Kohlenstoffzahl C der n-Alkane. Wie genaue Meßwerte für Retentionszeiten zeigen, ist die Funkton lg ts=f(C) nicht streng linear. Die Krümmung des Funktionsbildes bedingt, daß lineare Regressionsmethoden, sowie auch die Methode nach Kovats, es nicht erlauben, extrapolativ sowie über weite Retentionsbereiche interpolativ I-Werte zu berechnen. In dieser Arbeit werden Retentionsindices aufgrund eines kubischen Zusammenhanges zwischen lg ts und der Kohlenstoffzahl ermittelt. Die hierzu notwendige Totzeit tm wird aus den Differenzen der Bruttoretentionszeiten der Referenzhomologen ermittelt.
    Notes: Summary Methods of retention index calculation described in the literature have been based on a linear relationship between the logarithm of the adjusted retention times lg ts and the carbon numbers C of n-alkanes. Exact measurements of the retention times of n-alkanes show that the relationship lg ts=f(C) is in fact not strictly linear. Correct extrapolative or interpolative calculations of retention indices over a wide retention range are therefore impossible when using the original formula as given by Kovats or methods based on a linear regression concept. The method of retention index calculation presented here is based on a cubic relationship between lg ts and carbon number allowing extrapolative or interpolative calculations. The hold-up time (tm) is calculated on the basis of differences of retention times of the reference homologues.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 89-94 
    ISSN: 1612-1112
    Keywords: Determination of HCl ; Derivatization ; Trace analysis ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung In der vorliegenden Arbeit wird die Möglichkeit untersucht, kleine Mengen HCl durch derivatisierung mit 7-Oxabicyclo-(4.1.0)-heptan und anschließendem gas-chromatographischen Nachweis des Reaktionsproduktes 2-Chlorcyclohexanol zu bestimmen. Die Nachweisgrenze für das Produkt der Derivatisierung (2-Chlorcyclohexanol) entspricht 2 pg HCl. Durch verschiedene Probleme, die im Rahmen dieser Arbeit diskutiert werden, wird diese Nachweisgrenze in der Praxis nicht erreicht. Es zeigt sich jedoch, daß HCl-Konzentrationen im Bereich von ppm (bzw. HCl-Mengen〈1 μg) ohne weiteres zu bestimmen sind. Die Möglichkeiten dieser Analysenmethode werden diskutiert.
    Notes: Summary This paper the possibility of determining small quantities of HCl by derivatization with 7-oxabicyclo-(4.1.0)-heptane and subsequent gas chromatographic identification of the reaction product 2-chlorocyclohexanol is examined. The detection limit for the derivative (2-chlorocyclohexanol) is equivalent to 2 pg HCl. On account of various problems, discussed in the paper, this detection limit is not achieved in practice. It is nevertheless apparent that concentrations of HCl in the ppm-region (quantities of HCl〈1 μg) can be determined without difficulty. The scope for this method of analysis is disscussed.
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  • 19
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Columns: open tubular ; Columns: capillary ; Columns: capillary: comparison ; Efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A detailed comparison is given of the various equations derived by Golay and that derived by Hawkes for assessing the theoretical efficiency of SCOT columns. The terms in these equations which describe the resistance to mass transfer in both the gas phase and in the liquid phase are given in a form which permits the equations to be compared directly. A numerical comparison is then made of the potential efficiency predicted by the different equations for five partition ratio values for a set of nine idealized SCOT columns with a wide range of porous layer thickness and liquid loading. The potential column efficiencies are expressed in terms of the maximum theoretical mean specific plate number. It is shown that appreciable differences occur between the theoretical efficiencies given by the different equations when the porous layer thickness and liquid loading are high, but these differences are small for most of the columns used in practice.
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