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  • Gas chromatography  (173)
  • Springer  (173)
  • 2000-2004  (1)
  • 1985-1989  (172)
  • 1935-1939
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Trees 1 (1987), S. 94-101 
    ISSN: 1432-2285
    Keywords: Monoterpenes ; Abies alba Mill ; Resin ; Seeds ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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
    ISSN: 1432-1432
    Keywords: Primordial terrestrial atmospheres ; CH4, C2H2, CO2 ; Prebiotic synthesis ; High-frequency discharge ; Hydrocarbons ; Gas chromatography ; Mass Spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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
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    Physics and chemistry of minerals 27 (2000), S. 665-678 
    ISSN: 1432-2021
    Keywords: Key words Amber ; Rumantite ; Succinite ; Pyrolysis ; Gas chromatography ; Mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Romanian amber (rumanite) has been considered to be a separate species of fossil resin for more than a century. While earlier investigators held it to be very similar to succinite (Baltic amber), modern scholars have assigned it a distinctly different botanical origin. We have found that almost all of the constituents of the ether-soluble fractions of 13 specimens of authentic rumanite identified by gas chromatography–mass spectrometry have previously been reported in the soluble fraction of succinite, including succinic acid and its monoterpene esters. Additionally and significantly, the soluble fraction of rumanite contains a number defunctionalized compounds that do not preexist in succinite, but that are produced by pyrolysis of whole succinite or of its insoluble polymeric fraction. Simultaneous methylation pyrolysis–gas chromatography–mass spectrometry of the polymeric fraction of seven of the rumanite specimens yielded further copious amounts of dimethyl succinate, a number of diterpene resin acid methyl esters, and additional defunctionalized compounds known to be pyrolysis products of succinite. The evidence shows conclusively that the botanical origin of rumanite is not distinct from that of succinite. Rather, rumanite is a succinite that has suffered partial thermal degradation in the course of the folding of the Oligocene Kliwa sandstone formation in which it is most commonly found.
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  • 4
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Electron-capture ; Thermal-energy electrons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 5
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    Chromatographia 20 (1985), S. 195-196 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Wide-bore capillaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 6
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    Chromatographia 20 (1985), S. 308-312 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Silica surface modification ; Hexamethylcyclotrisilazane ; Hexamethyldisilazane ; Support materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 7
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    Chromatographia 20 (1985), S. 343-346 
    ISSN: 1612-1112
    Keywords: Thermosorb ; Tenax GC ; Environmental Analysis ; Trace Organics ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 8
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    Chromatographia 20 (1985), S. 371-375 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Flame photometric detector ; Sulphur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 9
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    Chromatographia 20 (1985), S. 538-542 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fluidized beds ; Industrial chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 10
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Preparation of methyl esters ; Tetramethylammonium hydroxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 11
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Linear temperature programming ; Thermodynamic chracteristics ; Calculation of k PT ′ for LPTGC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 12
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    Chromatographia 21 (1986), S. 110-112 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Nitrochlorobenzene isomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 13
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    Chromatographia 21 (1986), S. 149-151 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention indices ; Comparison of data ; Alkenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 14
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    Chromatographia 21 (1986), S. 157-160 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Alkylation ; Carboxylic acids ; Urine analysis ; Micelles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 15
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    Chromatographia 21 (1986), S. 214-218 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Behaviour of metal acetylacetonates ; Adsorption isotherms ; Heat of solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 16
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    Chromatographia 22 (1986), S. 278-282 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mixed phases ; Chlorinated C1−C3 hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 17
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Nitrogen-selective detector ; Flash methylation ; Morphine ; Blood analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 18
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    Chromatographia 22 (1986), S. 333-336 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Split sampling ; PTV-sampling ; Discrimination ; Quantitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 19
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    Chromatographia 22 (1986), S. 329-332 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Esterification in aqueous solution ; n-propyl esters of C1−C22 fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 20
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Micropacked columns ; Quantitation ; Fermentation products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 21
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Esterification in aqueous solution ; n-Propyl esters of aromatic polycarboxylic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 22
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    Chromatographia 23 (1987), S. 790-795 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary columns in series ; Variable polarity columns ; Essential oils analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 23
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Aqueous samples ; Direct injection ; Traces of ketones and halogenated hydrocarbons ; Environmental analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 24
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Backflushing, peak-cutting technique ; Trace analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 25
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid crystals ; Substituted benzenes and selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 26
    ISSN: 1612-1112
    Keywords: Gas chromatography ; FT-IR detection ; γ- and δ-Haloesters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 27
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid crystal ; Capillary columns ; Retention data ; Stationary phase film thickness ; Column surface quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 28
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    Chromatographia 25 (1988), S. 21-24 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sample concentration ; Chromatographic evaporation ; Solvent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 29
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Preparative scale separations ; Plate model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 30
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index ; Hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 31
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    Chromatographia 25 (1988), S. 404-408 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Silica surface modification ; Hexamethylcyclotrisilazane ; Hexamethyldisilazane ; Support materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 32
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    Chromatographia 25 (1988), S. 609-612 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Triglyceride composition of grapes ; Identification system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 33
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    Chromatographia 25 (1988), S. 655-658 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Structure-retention relationships ; Connectivity indices, topological indices ; Alkenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 34
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    Chromatographia 22 (1986), S. 271-274 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index calculation ; Epoxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 35
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    Chromatographia 23 (1987), S. 50-52 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention indices ; C6 alkanols ; OV-101 ; Carbowax 20M
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 36
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    Chromatographia 26 (1988), S. 34-36 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas analysis in halogen lamps ; Sampling device
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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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  • 37
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    Chromatographia 26 (1988), S. 229-233 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Glass capillaries ; Chirasil-Val ; Immobilisation ; Enantiomeric separation
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    Topics: Chemistry and Pharmacology
    Notes: 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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  • 38
    ISSN: 1612-1112
    Keywords: Gas chromatography ; On-line process analysis ; Injection of volatile compounds
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    Topics: Chemistry and Pharmacology
    Notes: 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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  • 39
    ISSN: 1612-1112
    Keywords: Gas chromatography ; FAME fingerprinting ; Animal fats ; Transesterification
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    Topics: Chemistry and Pharmacology
    Notes: 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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  • 40
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    Chromatographia 27 (1989), S. 596-600 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass spectrometry ; Azines
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    Topics: Chemistry and Pharmacology
    Notes: 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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  • 41
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    Chromatographia 27 (1989), S. 221-224 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Large volume sample injection ; Closed on-column injector
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    Topics: Chemistry and Pharmacology
    Notes: 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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  • 42
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    Chromatographia 28 (1989), S. 139-142 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Silica surface ; Silanols ; Strongly interacting sites
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    Topics: Chemistry and Pharmacology
    Notes: 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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  • 43
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    Chromatographia 28 (1989), S. 167-169 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Determination of monomer in polymers ; Sealed glass capillary sampling
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    Topics: Chemistry and Pharmacology
    Notes: 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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  • 44
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    Chromatographia 28 (1989), S. 237-240 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Slope of log plot ; Homologous series ; Retention index ; Retention time ; Uncertainty ; Free energy
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    Topics: Chemistry and Pharmacology
    Notes: 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.
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  • 45
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Optimization of gas-solid separations ; Plate height equation ; Computer mapping procedure
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    Topics: Chemistry and Pharmacology
    Notes: 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.
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  • 46
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary liquid, choice of ; Physico-chemical data
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    Topics: Chemistry and Pharmacology
    Notes: Summary A table of data for acidity, basicity, polarity and London potential for stationary phases is given. These provide guidance in choosing a stationary phase for a given task from the 26 substances listed. The indices are calculated from infra-red shifts of 1-chlorobutane and the visible wavelength shifts of l2 when they are dissolved in the stationary phases, from NMR estimates of acidity and basicity and from relative retention data. They replace the less reliable data of Burns and Hawkes. Methods of determining the indices are suggested that require only a gas chromatograph and can be applied by technicians with no specialized understanding of solution parameters. An attempt to add electron donoracceptor indices to the table was unsuccessful. A further table is given of the slopes of the log plots d(logt′)/dC for use in extrapolating from one homologue to another on these stationary phases.
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  • 47
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    Chromatographia 20 (1985), S. 403-406 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Separation of sugars ; Oxime formation ; Silylation
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    Topics: Chemistry and Pharmacology
    Notes: Summary The procedure involving oxime formation followed by silylation for the analysis of standard hexoses by GC resulted in unseparated peaks for D-glucose, D-mannose and D-galactose. This procedure was therefore modified to obtain clear separation of hexoses. STOX (hydroxylamine containing phenyl-β-D-glucopyranoside as the internal standard) was mixed with trimethylsilylimidazol or hexamethyldisilazane, and then added to a standard sugar mixture containing D-glucose, D-galactose and D-mannose. The mixture was analyzed by gas chromatography with OV-17/OV-22 as the stationary phase, resulting in three distinct peaks.
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  • 48
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Esterification in aqueous solution ; n-Butyl esters of aliphatic hydroxy acids
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    Topics: Chemistry and Pharmacology
    Notes: Summary Aliphatic hydroxy acids were esterified in aqueous solution in the presence of sulfuric acid. Esterification of lactic, tartronic malic and citric acids in water/n-butanol mixtures with mole ratios between 0.02 and 2.53 can be utilized for the determination of these aliphatic hydroxy acids by gas chromatography. Water does not interfere at water/n-butanol mole ratios below 0.02. For mole ratios above 0.02 anhydrous sodium sulfate is used for the binding of water. The mole ratio range was 0.25–2.53 for anhydrous sodium sulfate/water, and 0.32–1.27 for sulfuric acid/anhydrous sodium sulfate.
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  • 49
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Multi-chromatography ; Selectivity tuning ; Column combination ; Theory
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    Topics: Chemistry and Pharmacology
    Notes: Summary The evolution of the use of mixed phases or serial column combinations is outlined, leading to systems with fixed-length columns to be used in selectivity tuning (“multi-chromatography”). The difference between multi-chromatography and multi-dimensional gas chromatography is outlined. After discussing the system used in subsequent work, the fundamental relationships of multi-chromatography are detailed. Among the basic relationships the additivity of retention data, the relationship between the individual and composite capacity factors and the relative retentivity serving as the fundamental parameter of a multi-chromatography system are discussed. The relative retentivity is derived as a function of gas holdup times, pressures, and average velocities or flow rates. Finally, the relationships between individual vs. composite relative retention, efficiency, and resolution values are deduced.
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  • 50
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    Chromatographia 21 (1986), S. 697-700 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Methyl silicones ; Unified retention index ; Hydrocarbons
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    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic retention indices of 51 hydrocarbons were determined on OV-101 dimethylsilicone between 40 and 70°C. From the measured data the unified retention indices were calculated.
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  • 51
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Flame ionisation detection ; Cyanogen ; Cyanogen chloride
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    Topics: Chemistry and Pharmacology
    Notes: Summary The response of a flame ionisation detector (FID) to cyanogen ((CN)2) and cyanogen chloride (CNCI) has been studied. The lower limits of detection for (CN)2 and CNCl were 6×10−12 moles and 2×10−11 moles respectively. In a comparative study a thermal conductivity detector gave as its lower limit of detection for both (CN)2 and CNCl 4×10−11 moles. Both detectors showed excellent linearity over the range 0 to 10 micromoles. The ratio of the gradients of the FID calibrations (CN)2/CNCI were found to be approximately two suggesting the response depended on the cyanide group. The response and stability of the FID was investigated as a function of air and hydrogen flow-rates. The response increased with increasing air flow-rate for both (CN)2 and CNCI up to 300cm3min−1, thereafter no significant increase was observed. On raising the hydrogen flow from 10 to 25cm3min−1 only a slight increase in the sensitivity of the FID towards both (CN)2 and CNCI was observed. At higher flow rates the response for (CN)2 increased markedly whereas at the same flow rates the response for CNCI increased only slightly.
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  • 52
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    Chromatographia 22 (1986), S. 63-64 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Reid vapour pressure ; Stabilized crude oils ; C2−C5 hydrocarbons
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    Topics: Chemistry and Pharmacology
    Notes: Summary A new rapid method has been developed to determine Reid Vapour Pressure (RVP) for stabilized crude oils by gas chromatography. The quantity of light hydrocarbons dissolved in crude oil was measured directly by gas chromatographic analysis, while the RVP value was computed utilizing a new correlation with this quantity at constant temperature. A variety of crude oils were investigated and the results revealed the accuracy of this method.
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  • 53
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Thermionic detector ; Flame-forming agents ; CO2 and water gas
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    Topics: Chemistry and Pharmacology
    Notes: Summary The use of carbon monoxide were suggested as the flame-forming agent in the thermionic detector (TID). The main characteristics of this detector were studied. It was shown that the optimum flow rate of carbon monoxide is 40 ml/min at an air flow rate of 400–550 ml/min. The response increases twice with the positive potential on the collector. Molar responses of TID were compared with those obtained when using carbon monoxide and hydrogen. For instance, for phosphorus containing compounds they are approximately the same (∼102), while for nitrogen containing compounds in the case of carbon monoxide, there is a 2–5 fold increase in the response. The linear dynamic range for methaphose and azobenzene is 103.
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  • 54
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Glass capillary columns ; Pre-treatment of column surface ; n-Octadecanol films
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    Topics: Chemistry and Pharmacology
    Notes: Summary The properties of n-octadecanol films on bare surface of glass capillary columns, leached with hydrochloric acid, HMDS treated and covered with BaCO3 have been investigated. Using the “inverse” gas chromatography method it was found that the structure of the n-octadecanol film distinctly depends on the glass surface preparation. The influence of the properties of the treated glass surface was particularly strong on the structure and properties of the n-octadecanol monolayer directly adjacent to the column wall.
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  • 55
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    Chromatographia 23 (1987), S. 53-54 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Dual-column system ; Thermal conductivity detector ; Anesthetic gas mixtures
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    Topics: Chemistry and Pharmacology
    Notes: Summary A simple dual-column system with a thermal conductivity detector is described, that can be used for the quantitative analysis of anesthetic gas mixtures of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane), nitrous oxide and oxygen. The separation was performed on a Carbopack (SP 1000) column and a Porapak Q column arranged in series across the detector.
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  • 56
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    Chromatographia 23 (1987), S. 818-824 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Selective sampling ; On-line fractionation ; Essential oil analysis
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    Topics: Chemistry and Pharmacology
    Notes: Summary The paper describes the possibilities of on-line selective sampling as an on-line fraction technique for the analysis of essential oils. Selective sampling is a micro-separation method, on-line with on-column injection, carried out directly in the syringe body by means of a selective elution of the sample through a fraction cartridge. The paper reports a method of both preparing and standardizing silica gel cartridges, and illustrates through some examples the results of some elution series of solvents on different essential oils.
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  • 57
    ISSN: 1612-1112
    Keywords: Organic pollutants determination ; Gas chromatography ; Thermal desorption
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    Topics: Chemistry and Pharmacology
    Notes: Summary The problem of the separation of 34 volatile organic chlorinated compounds is solved by using three different GC columns selected according to the needs of the particular separation required. The effect of water vapor contained as moisture in the trapped air on the retention of some characteristic compounds is studied. The influence of dead volumes on trap injection is also studied.
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  • 58
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    Chromatographia 23 (1987), S. 888-892 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Calculation of temperature programmed ; Retention indices
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    Topics: Chemistry and Pharmacology
    Notes: Summary A new method is presented for the calculation of the retention indices under linear temperature programming with or without an initial isothermal period. The data calculated by the method are in good agreement with the isothermal retention indices.
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  • 59
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    Chromatographia 23 (1987), S. 169-170 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Packed column ; Immobilized silicone stationary phases ; Ozonization
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    Topics: Chemistry and Pharmacology
    Notes: Summary Immobilization of silicone stationary phases, OV-1701 vinyl and OV-225 vinyl, on Chromosorb W-AW support was achieved in a simple procedure using ozone as an initiator. A column efficiency of 2400 theoretical plates/meter was obtained.
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    Chromatographia 23 (1987), S. 195-198 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Structure-retention relationships ; Polarity parameters ; Retention index
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    Topics: Chemistry and Pharmacology
    Notes: Summary The possibility of evaluation of the parameters representing the dispersive solute-solvent interactions is presented. BN and Bs values can be used to describe the liquid phase polarity and to predict the retention indices of alcohols when the model polyxyethylene glycol dialkyl ethers and their sulphur analogs are used as stationary phases. The possibility of the first ionization potentials estimation is also presented.
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    Chromatographia 23 (1987), S. 240-242 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stillingia oil ; Quantitative lipid analysis ; Chinese tallow,Sapium sebiferum
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    Topics: Chemistry and Pharmacology
    Notes: Summary Contemporary stillingia oil from China is qualitatively similar to the oil described earlier, but it exhibits significant quantitative differences reflecting a degree of autoxidation of the unsaturated fatty acids either before or after crushing of the seeds.
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  • 62
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chemically bonded phases ; Specific interactions ; Chloroderivatives of alkanes and alkenes
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    Topics: Chemistry and Pharmacology
    Notes: Summary Interactions of Cu(II) complexes chemically bonded to the surface of silica with chloro-derivatives of alkanes and alkenes were investigated. It was found that chlorine as a substituent exerts a considerable influence on the retention of the individual chloro-derivatives. In the case of chloroalkenes this influence is negative while in the case of chloroalkanes it is positive. The magnitude of the observed effect depends on the number of substituents and on the way of their distribution within the molecule.
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  • 63
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    Chromatographia 23 (1987), S. 286-288 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Macroporous copolymers of 2-hydroxyethyl ; methacrylate ; Graft polymers ; Polar sorbent for gas chromatography
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    Topics: Chemistry and Pharmacology
    Notes: Summary The gas chromatographic behaviour of crosslinked macroporous 2-hydroxyethyl methacrylate grafted with 2-methyloxazoline was investigated and the range of applicability of the copolymer was assessed. Retention index values were measured on this copolymer and compared with those obtained on the terpolymer 2-hydroxyethyl methacrylate-ethylene dimethacrylate-acrylonitrile. Rohrschneider constants and efficiency data for selected sorbates are given. The use of this type of polymer in the separation of various types of compounds is documented by various examples.
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    Chromatographia 23 (1987), S. 423-426 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Complexation ; Mercaptosilane chemically bonded phase ; Transition metal complexes ; Olefinic π-complexes
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    Topics: Chemistry and Pharmacology
    Notes: Summary A column packing containing thiol groups chemically bonded to the silica surface was synthesized. The thiol functional groups were used as ligands capable of forming stable complexes with Cu(II). The prepared material was characterized by gas chromatography using unsaturated linear and branched hydrocarbons as well as cyclic and aromatic hydrocarbons. The occurrence of specific metal—olefin interactions resulting from the formation of π-complexes during the chromatographic process was observed.
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    Chromatographia 23 (1987), S. 499-501 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Packed+capillary GC switching system ; Precolumn construction, oven and connector
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    Topics: Chemistry and Pharmacology
    Notes: Summary The constractional details of precolumns, its oven and connector have been given with two types of multiflow control modules. Two types of phases made in China, a silanized pellicular beads and a non silanized pellicular silica beads, with an optimum particle size of 20μm to 30μm were packed in the precolumn 20mm in length with the column efficiency of 4620 plates/meter at column temperature of 49°C. A 25m×0.22mm i.d. capillary column coated with bonded methylsilicone phase from Chrompack connected with the precolumn (250°C) has an efficiency of 5376 plates/meter for n-octane. But it decreased to 3149 plates/meter by decreasing the precolumn temperature to 130°C.
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    Chromatographia 20 (1985), S. 681-682 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Geothermal gases ; Molecular sieves ; Low temperature separations
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    Topics: Chemistry and Pharmacology
    Notes: Summary The gases evolved from geothermal fields, after condensation of H2O, CO2, H2S and NH3 in caustic solution, contain He, H2, Ar, O2, N2, CH4 and higher hydrocarbons. The analysis for the major components in these residual gas mixtures can be achieved by use of two simple gas chromatographs in parallel, and using 5Å molecular sieve. The separation of He and H2 to baseline is achieved by using low temperatures (30°C) coupled with a relatively long column; and the difficult separation of Ar and O2 is achieved by use of a cryogenically cooled column. The use of switching valves to backflush and bypass columns ensures that a minimum time for analysis can be achieved whilst retaining baseline separations of the He/H2 and Ar/O2 pairs.
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    Chromatographia 20 (1985), S. 685-688 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fuming sulphuric acid-ethanol esterification ; Ethyl and methyl esters of herbicides
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    Topics: Chemistry and Pharmacology
    Notes: Summary A fuming sulphuric acid-ethanol esterification method has been applied to chlorophenoxy acids and some other herbicides. This method is compared with esterification by iodoethane and diazomethane. The chlorophenoxy acids studied were: 2,4-D, dichlorprop, MCPA, MCPB, mecoprop and 2,4,5-T. Other herbicides studied were: benazolin, bentazone, bromophenoxime, bromoxynil, chlorthal, dicamba, 3,6-dichloropicolinic acid, dinoseb, ethephon, fluroxypyr, glyphosate, haloxyfop, ioxynil, picloram, 2,3,6-TBA and triclopyr. Fuming sulphuric acid-ethanol esterification can be successfully applied to chlorophenoxy acids, benazolin, 3,6-dichloropicolinic acid, dinoseb, fluroxypyr, haloxyfop, picloram and triclopyr. The reproductibility of the method is ±5%.
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  • 68
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Step profile method ; Adsorption isotherm ; Water film pressure ; Surface free energy
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    Topics: Chemistry and Pharmacology
    Notes: Summary Investigation of water adsorption by the step profile method (Glueckauf method) was carried out with the help of a modified gas chromatography equipped with thermal-conductivity detector. On the basis of the adsorption isotherm obtained, the water film pressure and the polar component of the surface free energy of quartz were calculated. The calculated value of the polar component of the surface free energy of quartz agrees with analogous values obtained by other methods.
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    Chromatographia 25 (1988), S. 313-318 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index ; Slope of log plot ; Homologous series ; Partition coefficient
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    Topics: Chemistry and Pharmacology
    Notes: Summary The slope of the n-alkane log plot dt′R/dnc (t′R=adjusted retention time; nc=carbon number) for a stationary phase can be used to obtain the retention index of an unidentified substance in a chromatogram containing only one peak with a known retention index, or to predict the retention time of a substance from that of a different homolog in the same series. It can also be used to translate retention indices into relative retention time, partition coefficient or specific retention volume. Published values of the slope are collected and critically evaluated. Equations are deduced that predict its approximate value at a specified temperature given the value at only one other temperature.
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    Chromatographia 21 (1986), S. 397-401 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention time extrapolation ; Retention time interpolation
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    Topics: Chemistry and Pharmacology
    Notes: Summary An empirical method of extrapolating and interpolating gas chromatographic retention times obtained at three equally spaced isothermal temperatures is described. The accuracy of the method was evaluated from retention time data obtained using packed glass columns. A procedure for constructing retention time tables for homologous series and the derivation of an equation for calculating retention times as a function of temperature is also presented.
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  • 71
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Glass capillary columns ; Bile acids ; Hexafluoroisopropyl esters
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    Topics: Chemistry and Pharmacology
    Notes: Summary A modified gas chromatographic glass capillary technique for determination of five major bile acids (Cholic acid: CA, Chenodeoxycholic acid: CDCA, Deoxycholic acid: DCA, Lithocholic acid: LCA and Ursodeoxycholic acid: UDCA) has been developed after preliminary extraction with XAD-2 resin. Enzymatic hydrolysis prevents the formation of interferring degradation products. Ether extraction with centrifugation eliminates water soluble interferring substances. Derivatization to hexafluorpropyl- instead of methyl esters results in better separation, shortens analysis time and prolongs the life span of the column.
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  • 72
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    Chromatographia 25 (1988), S. 598-602 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary columns ; Steroid profiles
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    Topics: Chemistry and Pharmacology
    Notes: Summary Steroid conjugates are hydrolysed enzymatically using β-glucuronidase after extraction from urine using a solid phase extraction cartridge. After hydrolysis the free steroids are removed from the matrix, again utilising solid phase extraction. Derivatisation of the free hydroxyl groups using Hydrox-Sil AQ produces the respective TMS ethers which are extracted into hexane, in which solvent they are stable for many days. Capillary GC analysis with flame ionisation detection produces a profile of the steroids present in the sample. This technique is suitable for following changes in the urinary excretion profiles of patients undergoing investigation for a variety of steroid production-related diseases.
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  • 73
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    Chromatographia 25 (1988), S. 539-542 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Temperature programming ; Retention index
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method is presented for the calculation of retention indices at an assigned temperature from temperature-programmed data. If the retention times at two different program rates for the solutes and the n-alkanes are known, the retention indices at an assigned temperature can be calculated directly.
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  • 74
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    Chromatographia 25 (1988), S. 589-592 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Hold-up time determination
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    Topics: Chemistry and Pharmacology
    Notes: Summary New versions are suggested for the gas hold-up time calculation in gas chromatography. The results are compared with those obtained by using other methods. The advantages of the suggested ways of calculation are pointed out.
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  • 75
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    Chromatographia 25 (1988), S. 618-620 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Toluenesulfonic acid isomer distribution ; Ethyl toluenesulfonate isomers
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    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method for the determination of isomeric distribution in toluenesulfonic acid samples is described. The acids are transformed into the corresponding ethyl esters by reaction with triethyl orthoformate in toluene. The reaction mixture can be injected, without further purification, into the gas chromatograph. The separation is best performed on columns containing OV-210 or polyphenyl ether (6 rings) as the stationary phase.
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  • 76
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    Chromatographia 22 (1986), S. 183-186 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; C2−C5 hydrocarbons ; Pre-Concentration on silica gel ; Sorption efficiency
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    Topics: Chemistry and Pharmacology
    Notes: Summary A short stainless steel column packed with silica gel is cooled to −78°C and atmospheric hydrocarbons are preconcentrated from 3 I of air on it. Desorption to the analytical column is by heating for 10 min to 200°C. Analysis is by GC on OPN-Poracil C at 27°C. The sorption efficiencies were nearly 100% for most of the light hydrocarbons.
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  • 77
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    Chromatographia 25 (1988), S. 725-730 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Structure-retention correlation ; Kováts retention index ; Alkylaromatics
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    Topics: Chemistry and Pharmacology
    Notes: Summary Relative retention data and Kováts retention indices were measured for several hydrocarbons (mainly for alkylbenzenes) on dinonylphtalate and polyethylenelycol 4000 stationary phase. Correlations were searched between these retention data and the following physical (boiling point, molrefraction, molvolume) and topological (connectiviity index and general index of molecular complexity) properties of solutes. The best fitting equations was choosen among more than 150 equations involving linear, quadratic, exponential, two variables linear and quadratic dependence of retention data and the properties mentioned as well as their inverses.
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  • 78
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid crystals ; Thermodynamic properties
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    Topics: Chemistry and Pharmacology
    Notes: Summary Thermodynamic properties of 22 solutes at infinite dilution have been determined in the smectic, nematic and isotropic mesophases of 4,4′-bis(heptyloxy)azoxybenzone. The thermodynamic properties are discussed in relation to the solute-solvent (liquid crystal) interactions as conditioned by the degree of order in the liquid crystal.
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  • 79
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Perhalogenated compounds ; Relative retentions ; Identification by interpolation
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    Topics: Chemistry and Pharmacology
    Notes: Summary Separation of perhalogenated compounds resulting from thermolysis, photolysis or radiolysis of mixtures of halogens in carbon tetrachloride was carried out by programmed temperature gas chromatography. Plots of relative retentions (to CBr4) vs the number of bromine atoms present for known compounds of the general formula CxBryClz (x=1 and 2; y+z=4 or 6) gave three linear correlations (all with r〉0.99). These correlations permitted projections of the identities of reaction products for which no standards were available. These projections were later confirmed by CG-MS. *** DIRECT SUPPORT *** A0732166 00010
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  • 80
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    Chromatographia 26 (1988), S. 413-416 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas analysis in incandescent lamps ; Gas chromatographic determination of O2 impurity in argon
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    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive GC method was developed to analyse O2 (∼10–400ppm) in argon, by using Ar as carrier gas. A sampling method was developed for lamp analysis, and the O2 impurity content in the gas filling of incandescent lamps was measured. The results of the GC and MS measurements were in good agreement.
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  • 81
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    Chromatographia 27 (1989), S. 37-43 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Methylbromide ; Charcoal tubes ; Pollution
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    Topics: Chemistry and Pharmacology
    Notes: Summary Air sampling of methylbromide using 900 mg HBr-treated activated charcoal tubes, followed by solvent desorption and FID or ECD chromatographic analysis, makes it possible to evaluate concentrations ranging from 0.2 ppm (1 mg×m−3) to 250 ppm (1g×m−3) at ambient temperature even with a high hygrometric level. Thermal desorption does not lead to satisfactory results.
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  • 82
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    Chromatographia 27 (1989), S. 60-66 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass loadability ; Stationary phase capacity ; Capillary columns
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    Topics: Chemistry and Pharmacology
    Notes: Summary In GLC the mass load can be normalized with respect to the amount of stationary phase in one plate. This quantity can be used for a specified solute-liquid phase combination in any capillary or packed column, irrespective of the column dimensions or the number of plates. For each individual solute in a given stationary phase a unique factor β″ can be found, which accounts for the specific shape of the isotherm of this particular combination. this factor β″ corresponds well with the activity coefficients of the solutes in the stationary phase, by which a fairly good approximation of the mass loadability of the column at hand can be made without need for experiment.
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  • 83
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    Chromatographia 27 (1989), S. 552-558 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Radio gas chromatography ; 3H- and14C-labelled compounds ; Isotope effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Radio gas chromatography (RGC) is a valuable tool for the analysis of radioactively labelled compounds. Recent advances in capillary GC, especially in column technology and instrumentation have also induced new possibilities in this field. With regard to the preservation of the achieved separation efficiency, radioactivity detection is the main problem in capillary RGC. Based on published data and on our extensive experience in conventional RGC, a simple, reliable and versatile method has been developed for the radioactive detection: purge gas is added to the effluent of the capillary column and the RGC detection unit with conversion tube and flow-through proportional counter is used maintaining small dead volumes and dimensions. The influence of the extra-column volumes and of the total gas flow rate (of the carrier, purge and quenching gases) on the peak shape was investigated. It was also found that the isotopic effect commonly known in GC of2H- and3H-labelled compounds is hardly measurable for larger [G-14C] labelled species such as [G-14C] labelled higher fatty acids with high isotopic abundance of14C, even on the highly efficient capillary columns. The quantitative aspects of the detection method used are discussed and some applications to the analysis of labelled biochemicals (amino and fatty acids) are demonstrated.
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  • 84
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Coke oven gas evolution ; On-line gas analysis
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    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatograph will thermal conductivity detector (TCD) connected on line via a cleaning train to the semi-industrial scale Coke Oven Text Plant of the Spanish National Coal Institute (INCAR), has been used to control the evolution of the permanent gases during the coking process. The undesirable presence of oxygen in the coke oven gas can be detected with this system that will be applied to determine the end of the coking process by quantitative analysis of the gas evolved.
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  • 85
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Microwave plasma detector ; Thiophenes ; Shale oil distillates
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    Topics: Chemistry and Pharmacology
    Notes: Summary A series of alkylthiophenes and dimethyl disulfide were tentatively identified in an oil shale retort gas condensate from a 6-kg bench-scale retort using gas chromatography with a microwave-induced helium plasma detector (GC-MIP). The sulfur species were present in concentrations ranging from 1.5 to 10.7 mol ppm in the undiluted offgas. The GC-MIP technique was successful in selectively detecting the sulfur components in the complex mixture. Quantitation was simplified relative to GC with flame-photometric detection because of the absence of quenching or other interference problems at the concentrations studied. Attempts to determine stoichiometry of the sulfur components by comparison of carbon, hydrogen, and sulfur ratios with those of standards were unsuccessful because of the complexity of the carbon and hydrogen chromatograms.
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  • 86
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Air pollutants ; Adsorbent enrichment ; Thermal desorption
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    Topics: Chemistry and Pharmacology
    Notes: Summary A new automatic method is described for quantitative determination of some light C2–C4 hydrocarbons in urban air: ethene, ethyne, propane, propene, butane and iso-butane. This method is based on an enrichment step at room temperature using a solid sorbent and subsequent thermal desorption for gas chromatographic separation and FID detection. The instrument is built up of a small commercial gas chromatograph and a laboratory-made trap and desorption unit. The sampling parameters, sample volume, concentration and humidity of air have been investigated.
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  • 87
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    Chromatographia 27 (1989), S. 159-163 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Flame photometric detector ; Sulfur compounds ; Response quenching
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    Topics: Chemistry and Pharmacology
    Notes: Summary The long time retardation of the main hydrocarbon peak in the chimney of the flame photometric detector greatly reduces the responses of later-eluting sulfur compounds. In the absence of hydrocarbons in the flame, the slope (s) of the log I vs. log [S] plot (where I is the sulfur response and [S] is the sulfur concentration in the sample) is of the highest value and is constant for all experimental conditions tested. Flame hydrocarbons cause the s value to decrease, and this is dependent on the oxygen to hydrogen ratio in the flame (O/H) and, under certain conditions, also on the sulfur to carbon ratio (S/C) of the sample. The abnormalities observed in the determination of methyl thiol in natural gas are explained on the basis of the present study.
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  • 88
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    Chromatographia 27 (1989), S. 631-632 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Wide-bore glass capillary columns ; End-sealing ; Static coating
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    Topics: Chemistry and Pharmacology
    Notes: Summary An end-sealing method to be used for static coating of wide-bore glass capillaries is described. After the capillary was completely filled with the coating solution, one end is connected to a gas-tight syringe (10-ml volume) via silicone tubing and the other end is fixed with shortcutted silicone tubing for sealing with a plug. The method is highly successful.
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  • 89
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    Chromatographia 27 (1989), S. 233-237 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; FTIR ; Hemoglobin
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    Topics: Chemistry and Pharmacology
    Notes: Summary The use of N, O (S)-tert.-Butyldimethylsilyl derivatives of amino acids for capillary gas chromatography and FTIR identification of amino acids is described. Rapid identification is achieved by computerised comparison of FTIR spectra. Derivatives that are characterised by identical sets of ions in gas chromatography-mass spectrometry experiments are clearly distinguished and identified by means of their infrared spectra. This, for example, is the case with alanine, β-alanine and sarcosine, which norvaline and valine, and with norleucine, leucine and isoleucine. Unknows are also promptly detected. This is especially useful in screening biological samples for less common amino acids. Screening of hemoglogin hydrolysates for amino acid adducts is exemplified.
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  • 90
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ethyl carbamate ; Direct injection quantification ; Cold injection system ; Optimised SIM
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    Topics: Chemistry and Pharmacology
    Notes: Summary An integrated procedure is described which allows direct injection quantitative screening to single figure parts per billion (μg/L) levels of ethyl carbamate in the natural matrix of distilled alcoholic beverage. Injection and detection performance was studied and optimized to allow this routine, reproducible, trace analysis without any sample pre-treatment. All aspects of the analysis including autosampler run sequences and automated internal standard report generation are initiated and controlled from a single GC/MS workstation.
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  • 91
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Trichloroethyl ester ; Dicarboxylic acid ; Urine samples ; Electron capture ; Biological monitoring
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    Topics: Chemistry and Pharmacology
    Notes: Summary Dicarboxylic acids were esterified by 2,2,2-trichloroethanol by using trifluoroacetic anhydride and phosphoric acid as catalysts. The method was developed to facilitate the evaluation of workers' exposure to sensitising acid anhydrides and other compounds metabolised to acids in the body. The sensitivity of the acid determination in urine was in the order of 2–4 ng ml−1 for aliphatic and alicyclic acids and 15ng ml−1 for phthalic acid.
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  • 92
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    Chromatographia 27 (1989), S. 499-508 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Electron capture detector ; Space-charge model
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    Topics: Chemistry and Pharmacology
    Notes: Summary Mathematical analysis, allowing the determination of the distribution of the electron and positive ion concentration in an electron-capture detector with a cylindrical electrode arrangement and with constant and pulsed voltage supplies, has been carried out. The measurements obtained confirm the assumptions concerning the “space change” model of the ECD introduced by Gobby et al. and cast doubt upon the general assumption of the complete removal of the electrons from the detector by the voltage pulse. The physical factors influencing the current characteristics of the detector and the possible distortions connected with the electrode geometry have been explained on the basis of the measurements carried out.
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  • 93
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    Chromatographia 27 (1989), S. 455-460 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Surface free energy ; Silane-covered materials ; Film pressure
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    Topics: Chemistry and Pharmacology
    Notes: Summary The surface free energy, or film pressure, π0, is measured for mica (Mica HK), silane-covered mica (Mica NP), Chromosorb W DMCS and glass beads. The film pressure is obtained from gas chromatography. The materials are used as adsorbents and benzyl alcohol and n-dodecane are used as molecular probes. Adsorption isotherms at 353 K are obtained from gas chromatography data and the surface free energy is computed with the help of the Gibbs equation. Values of π0 for a given surface are found to vary with the molecular probe. With benzyl alcohol π0 varies from 44 erg/cm2 for Mica 60 HK to 76 erg/cm2 for glass. In the case of n-dodecane π0 is found to vary in the same manner but the values range from 25 to 45 erg/cm2. The results are in good agreement with the values obtained with the contact angle method.
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  • 94
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    Chromatographia 27 (1989), S. 469-471 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace analysis ; Ethylene oxide ; Capillary column
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A headspace gas chromatographic method for determination of traces of ethylene oxide (EO) in sterilized materials has been developed. The method allows the determination of the amount of EO by putting the samples directly into acetonitrile and analysing by means of headspace GC. The procedure described is simple, sensitive, reproducible and linear. The lower limit of detection is 0.015 μg/g of sterilized material.
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  • 95
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Colloidal stationary phases ; Liquid crystals as stationary phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Colloid systems consisting of the nematic liquid crystals p,p′-azoxyphenetol and p,p′-methoxyethoxyazoxybenzene and high-disperse mineral particles (aerosil, carbon black) are proposed to be used as stationary phases in gas chromatography. The dependence of the retention of normal paraffins, Rohrschneider and McReynolds test solutes (benzene, ethanol, methyl ethyl ketone, nitromethane, pyridine, butanol-1, 2-pentanone, and nitropropane) on the composition of the colloid systems was investigated. The investigated colloid sorbents including liquid crystals retain their selectivity for meta/para isomers up to 50% of the aerosil content and practically at all studied carbon black concentrations.
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  • 96
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    Chromatographia 28 (1989), S. 24-26 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Anesthetics ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive capillary gas chromatographic method is described for the simultaneous determination of lidocaine, tetracaine, procaine and dibucaine. The method was applied to the determination of anesthetics in tissue homogenates incubated at 38°C at doses between 10 and 400 mg/kg. In the liver tissue thein vitro metabolization of the studied anesthetics is most rapid for tetracaine, also fast for procaine, while for lidocaine and dibucaine the metabolization is very slow. In brain tissue thein vitro metabolization of anesthetics is very slow. The method shows good analytical parameters: linearity between 5 and 40 μg/ml; day-to-day reproducibility ca. 8% for a concentration of 20 μg/ml, precision ca. 7% for a concentration of 20μg/ml. Accuracy is also very good.
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  • 97
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chlorinated methanes ; Activated charcoal sampling ; Pollution
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    Topics: Chemistry and Pharmacology
    Notes: Summary A sampling method using activated charcoal, followed by percolation with ethanol and FID or ECD chromatographic analysis, depending on the concentrations to be monitored, makes it possible to evaluate concentrations of methylene chloride between 5 and 1000mg m−3, chloroform between 0.1 and 2000mg m−3, and carbon tetrachloride between 0.015 and 1000mg m−3.
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  • 98
    ISSN: 1612-1112
    Keywords: Gas chromatography ; GC/MS and headspace GC ; Elastomeric stoppers for injectables ; Trace hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Elastomeric stoppers for injectables have been surveyed by means of GC/MS screening. Residual contamination by hexanes (2-methylpentane, 3-methylpentane, n-hexane, methylcyclopentane, cyclohexane) toluene and xylenes occurred in all the samples tested. A headspace GC purity test is suggested, by using these residual chemicals as purity indexes.
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  • 99
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    Chromatographia 28 (1989), S. 313-314 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fused-silica columns ; Static coating ; Sealing method
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    Topics: Chemistry and Pharmacology
    Notes: Summary In this paper a new sealing method for the static coating of capillary columns is described. When one end of the fully filled capillary was immersed into liquid nitrogen in a Dewar flask, the coating solution at this end would be frozen and became a temporary seal, and an air-free solvent/seal interface was obtained. No bumping has ever been found at the interface, even when butane was used as solvent. By applying this sealing method, several capillary columns, including some narrow bore capillary, had been successfully coated.
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  • 100
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Renewal theory ; Monte-Carlo simulation ; Prediction of retention and peak widths
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    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for prediction of gas chromatographic retention times and peak half widths is based on the renewal theory. The only requirements are the heats of vaporization of the compounds to be separated and one calibration measurement. With this data, retention times and peak half widths can be predicted for isothermal as well as temperature-programmed gas chromatography. For the separation of non-polar substances on non-polar stationary phases the prediction error for retention times is approx. 1–2%. First simulations of polar molecules and polar stationary phases indicate that this method is also applicable in these cases but some extension will be required.
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