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  • Gas chromatography  (172)
  • Springer  (172)
  • American Chemical Society
  • American Institute of Physics (AIP)
  • 1985-1989  (172)
  • 1935-1939
Collection
Publisher
  • Springer  (172)
  • American Chemical Society
  • American Institute of Physics (AIP)
  • Wiley-Blackwell  (105)
Years
Year
  • 1
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    Chromatographia 27 (1989), S. 37-43 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Methylbromide ; Charcoal tubes ; Pollution
    Source: Springer Online Journal Archives 1860-2000
    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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  • 2
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    Chromatographia 27 (1989), S. 60-66 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass loadability ; Stationary phase capacity ; Capillary columns
    Source: Springer Online Journal Archives 1860-2000
    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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  • 3
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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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  • 4
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    Chromatographia 27 (1989), S. 644-648 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ion exchange resins ; Polymeric supports ; Chloromethanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of compounds of various classes on macroporous sulfonated cation exchangers in the form of the fourth period elements in Mendeleev's table (i. e. in the K, Ca, Co, Ni, Cu, Zn-forms) has been investigated. It has been shown that these sorbents are characterized by a high specificity of molecular interaction. It has also been established that the gas-chromatographic properties of cation exchangers depend on the nature and valency of the metal ion in the ionogenic group.
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  • 5
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    Chromatographia 27 (1989), S. 109-112 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Packed columns ; Immobilized stationary phase ; Poly(ethylene glycol) phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Carbowax 20M poly(ethylene glycol) stationary phase was immobilized on Chromosorb W by cross-linking with pluriisocyanate. The properties of the prepared packing material were investigated. Column efficiencies of 10,960 and 7,510 theoretical plates/meter were obtained for n-pentadecane and 1-heptanol, respectively.
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  • 6
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    Chromatographia 27 (1989), S. 159-163 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Flame photometric detector ; Sulfur compounds ; Response quenching
    Source: Springer Online Journal Archives 1860-2000
    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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  • 7
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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
    Source: Springer Online Journal Archives 1860-2000
    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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  • 8
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ethyl carbamate ; Direct injection quantification ; Cold injection system ; Optimised SIM
    Source: Springer Online Journal Archives 1860-2000
    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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  • 9
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    Chromatographia 27 (1989), S. 455-460 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Surface free energy ; Silane-covered materials ; Film pressure
    Source: Springer Online Journal Archives 1860-2000
    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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  • 10
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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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  • 11
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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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  • 12
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    Chromatographia 28 (1989), S. 639-642 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary columns ; Split injection ; Sample tailing and cold trap effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sample plug tailing together with a cold trap effect brings about discrimination against low boiling components at an initial column temperature above the boiling point of the solvent. In conventional split injection, this compensates for the opposite effects of such factors as the gas phase viscocity change and the pressure wave during the split period, and reasonable results are obtained. In stop-flow injection, however, since the influences of the opposite factors are diminished, the sample plug tailing and the cold trap effect may produce results showing lower than true concentrations for the low boiling components.
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  • 13
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    Chromatographia 28 (1989), S. 313-314 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fused-silica columns ; Static coating ; Sealing method
    Source: Springer Online Journal Archives 1860-2000
    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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  • 14
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    Chromatographia 28 (1989), S. 502-504 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention variation ; Effect of sample composition on retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The variation of the retention index of a solute due to the presence of a closely neighboring peak is discussed. The neighboring peak is likely to modify the original stationary liquid by forming a temporary “mixed” stationary phase. The extent of the retention index variation is influenced by many experimental parameters and becomes pronounced when the stationary phase is overloaded by the neighboring peak and the film thickness of the stationary phase is not very large. However, the exact extent of this variation is rather unpredictable. The practical significance of this finding is also discussed.
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  • 15
    ISSN: 1612-1112
    Keywords: Gas chromatography ; FAME fingerprinting ; Animal fats ; Transesterification
    Source: Springer Online Journal Archives 1860-2000
    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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  • 16
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    Chromatographia 27 (1989), S. 71-76 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Electron-capture detector ; Constant-current mode ECD ; Non-linearity of ECD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effects of the ionization source activity, sample input rate, electron capture rate constant, ventilation rate constant and baseline frequency on the linearity, detectability and sensitivity of the constant-current electron-capture detector (CC-ECD) were investigated. The proposed model representing an extension of the Wenthworth-Lovelock model proved to be useful in demonstrating that the CC-ECD can be highly nonlinear for strong electron capturers, at high ionization source activities, at a low ventilation rate constant and at low baseline frequencies. Optimization of the CC-ECD operation is possible by a reasonable adjustment of the studied parameters.
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  • 17
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Coke oven gas evolution ; On-line gas analysis
    Source: Springer Online Journal Archives 1860-2000
    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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  • 18
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    Chromatographia 27 (1989), S. 182-184 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Micropacked columns ; Alkyl-modified silica ; Hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Micropacked columns for liquid chromatography were evaluated for the gas chromatographic separation of hydrocarbons. A glass-lined stainless-steel tube of 30 cm×0.3 mm i.d., packed with 5-μm alkyl-modified silica, was employed as the separation column. The micropacked columns were successfully applied to the separation of components of a light oil and a kerosine.
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  • 19
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    Chromatographia 27 (1989), S. 205-208 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Kováts indices ; Numerical interpolation ; Dead time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Comparison with normal procedures shows that numerical interpolation of the logarithms of gross retention times generates quite useful Kováts indices for gas chromatographic analysis. The dead time concept is not used in the interpolation.
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  • 20
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Adsorption studies ; Clinoptilolite ; Zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Adsorption properties of NH4-clinoptilolite, thermally treated at 400, 550 and 650°C, were investigated by gas-solid chromatography. Adsorption of ten hydrocarbons, including aliphatic, alicyclic, chlorinated and aromatic compounds is discussed in the light of adsorbate-adsorbent interactions. The imporatant thermodynamic parameters of adsorption are determined. A detailed discussion is presented on the alteration of the surface properties of NH4-clinoptilolite caused by thermal treatment. Experimental data obtained show that NH4-clinoptilolite treated at 650°C can be successfully employed as a column packing in analytical gassolid chromatography.
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  • 21
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    Chromatographia 27 (1989), S. 436-440 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid crystal stationary phases ; PAH ; FAME ; Mesomorphic polysiloxane phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The gas-chromatographic properties of two mesomorphic polysiloxane (MEPSIL) stationary phases, one smectic (SB) and the other nematic (N), were investigated. The retention indices and separation factors (relative retentions), α, of several pairs of polycyclic aromatic hydrocarbon (PAH) and fatty acid methyl ester (FAME) isomer solutes were used to gauge differences in the selectivity provided by each. The heats of solution of the PAH showed that the smectic MEPSIL is more selective for solutes with different length-to-breadth ratios. Also, five peaks were resolved for sixcis andtrans octadecenoic FAME isomers with this solvent. The nematic MEPSIL, on the other hand, was found to be more useful at higher temperatures because of its higher clearing point. In addition, solute capacity factors were smaller than those observed with the smectic MEPSIL, as evidenced by lower retention indices. The former was therefore more useful for the analysis of high molecular-weight PAH.
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  • 22
    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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  • 23
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chlorinated methanes ; Activated charcoal sampling ; Pollution
    Source: Springer Online Journal Archives 1860-2000
    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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  • 24
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    Chromatographia 28 (1989), S. 139-142 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Silica surface ; Silanols ; Strongly interacting sites
    Source: Springer Online Journal Archives 1860-2000
    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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  • 25
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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
    Source: Springer Online Journal Archives 1860-2000
    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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  • 26
    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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  • 27
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Optimization of gas-solid separations ; Plate height equation ; Computer mapping procedure
    Source: Springer Online Journal Archives 1860-2000
    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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  • 28
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Renewal theory ; Monte-Carlo simulation ; Prediction of retention and peak widths
    Source: Springer Online Journal Archives 1860-2000
    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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  • 29
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Microwave plasma detector ; Thiophenes ; Shale oil distillates
    Source: Springer Online Journal Archives 1860-2000
    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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  • 30
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Air pollutants ; Adsorbent enrichment ; Thermal desorption
    Source: Springer Online Journal Archives 1860-2000
    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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  • 31
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    Chromatographia 27 (1989), S. 596-600 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass spectrometry ; Azines
    Source: Springer Online Journal Archives 1860-2000
    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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  • 32
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    Chromatographia 27 (1989), S. 221-224 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Large volume sample injection ; Closed on-column injector
    Source: Springer Online Journal Archives 1860-2000
    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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  • 33
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    Chromatographia 27 (1989), S. 233-237 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; FTIR ; Hemoglobin
    Source: Springer Online Journal Archives 1860-2000
    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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  • 34
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Trichloroethyl ester ; Dicarboxylic acid ; Urine samples ; Electron capture ; Biological monitoring
    Source: Springer Online Journal Archives 1860-2000
    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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    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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    Chromatographia 27 (1989), S. 333-339 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Catalytic reactions ; Adsorption and desorption rate constants ; Reversed-flow techniques
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    Topics: Chemistry and Pharmacology
    Notes: Summary A small volume of reactant, 1-butene, is injected onto a catalytic bed and is allowed to diffuse away from it together with the product butane, along a narrow empty chromatographic tube; the latter is connected perpendicularly to the middle point of another similar tube through which hydrogen flows as reactant and carrier gas, transferring both 1-butene and butane to the detector through an analytical column. By using the reversed-flow GC technique, extra peaks are obtained in the chromatographic trace, sampling the concentration of both the readtant and product at the junction of the two tubes as a function of time. These concentrations are the result of the diffusion of the substances along the narrow empty tube, modified by the adsorption-desorption rates and the rate of the catalytic reaction. From the extra peaks of the reactant and product, a number of physicochemical quantities pertaining to the catalytic reaction can be calculated simultaneously, using appropriate mathematical analysis. These include adsorption rate constants, reaction rate constants, desorption rate constants, partition coefficients, and the overall mass transfer coefficients of the reactant across the gas-solid boundary of the catalytic bed.
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  • 37
    ISSN: 1612-1112
    Keywords: Gas chromatography ; KF·2H2O as stationary phase ; Alcohols ; Organic bases
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    Topics: Chemistry and Pharmacology
    Notes: Summary Potassium fluoride crystal dihydrate is used as the stationary phase for the rapid analysis of polar compounds in aqueous solutions. KF·2H2O is compared with some conventional stationary phases, organic salts and molten crystal hydrates of inorganic salts.
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  • 38
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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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  • 39
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    Chromatographia 28 (1989), S. 631-638 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace GC/FTIR ; Optimization ; Detection limits ; Cryogenic trapping
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    Topics: Chemistry and Pharmacology
    Notes: Summary For the trace analysis of volatile components in a nonvolatile matrix, the headspace sampling technique offers the potential to lower detection limits in GC/FTIR experiments. Optimization of chromatographic operating parameters for Headspace GC/FTIR is discussed, aiming at the best compromise between maximum chromatographic resolution and highest S/N ratio of the infrared spectra. It is shown that the combination of headspace sampling with cryogenic capillary head trapping is able to provide Headspace GC/FTIR with the best performance in terms of sensitivity and chromatographic resolution.
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  • 40
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Reaction rate studies ; Dicyclopentadiene
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    Topics: Chemistry and Pharmacology
    Notes: Summary The gas chromatographic reactor technique was used to study the kinetics of dicyclopentadiene dissociation in several liquid phases (Versamid 900, neopentyl glycol sebacate, Triton X-305, Carbowax 6000, ethylene glycol phthalate and diethylene glycol succinate). Reaction rates and Arrhenius parameters are reported in the temperature range of 170–200°C. Kinetic data for the lower polarity liquid phases are in good agreement with literature values for liquid phases of the same nature reported previously. Reaction rates are higher when polar liquid phases are used. This behavior can be explained as a result of side reactions which lead to high molecular weight compounds which can be observed in the reaction chromatogram.
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    Chromatographia 28 (1989), S. 385-390 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary column ; Split injection ; Stop-flow method
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    Topics: Chemistry and Pharmacology
    Notes: Summary Major concerns in the development of the stop-flow split injection are discussed. Split ratio fluctuation caused by the pressure wave, solvent recondensation and gas viscosity change can be substantially diminished through the formation of a nearly uniform gaseous sample plug. Instrumental variables exerting influence on the accuracy of quantitation were studied. Higher injector temperature and the use of a carrier gas with higher heat conductivity benefit the quick vaporization of the sample liquid, and thus, help in the formation of a sample plug with more unformity.
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    Chromatographia 28 (1989), S. 405-411 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Concentration of volatile flavor compounds ; ODS packing
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    Topics: Chemistry and Pharmacology
    Notes: Summary Volatile flavor compounds in aqueous model systems, distillates of coffee extract and juices such as apple, tomato, pineapple and grape were adsorbed on an ODS column during HPLC and monitoring absorption at 280nm. The adsorbed volatile compounds were eluted with a small volume of ethanol. Volatile compounds in the eluates were concentrated 22 to 100 times those in the distillates. Recovery of compounds was 50–90%. Breakthrough of specific compounds such as γ-valerolactone, furfuryl acetate and t-2-hexenal in the model systems and several compounds in the juice distillates was detected by capillary GC. Pattern similarity calculated between the GC profiles of a juice distillate and the corresponding eluate gave a qualitative comparison. This novel and versatile method utilizing conventional RP-HPLC may be widely applicable for concentrating volatiles in aqueous systems, at levels from ppm to ppb.
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  • 43
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Simultaneous distillation-extraction ; Cheese volatiles
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    Topics: Chemistry and Pharmacology
    Notes: Summary A simultaneous distillation-extraction apparatus proposed by Godefroot has been used for the GC study of volatile components of cheese. 5–10 g of cheese provide a fraction that can be directly injected into a GC or a GC/MS. Two capillary columns (SE-30 and SP-1000) were evaluated, the second one being adequate for quantitative determinations. Camphor was used as internal standard. The coefficients of variation ranged from 1.4 to 11.8. The technique can be used as a fast method for the characterization of cheeses from their volatile component concentrations.
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    Chromatographia 25 (1988), S. 1087-1088 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Log plot ; Homologous series
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    Topics: Chemistry and Pharmacology
    Notes: Summary The slope of the log plot of the adjusted retention time of a homologous series usually varies from that of the n-alkane series by no more than 2%, though with unusual interactions between the functional group and the stationary phase the difference may be as high as 7%.
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  • 45
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Preparative scale separations ; Plate model
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    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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    Chromatographia 25 (1988), S. 404-408 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Silica surface modification ; Hexamethylcyclotrisilazane ; Hexamethyldisilazane ; Support materials
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    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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  • 47
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Statistical criteria ; Non-linear models ; Constants for n-alkane retention curve ; Multiparametric least-squares adjustment
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    Topics: Chemistry and Pharmacology
    Notes: Summary Multiparametric, least-squares, regression treatment of G.C. data is extended to describe deviations from the usual linear model. Through statistical evaluation of results, four parameters models are generally found adequate and the use of higher degree empirical models is discouraged.
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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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    Chromatographia 26 (1988), S. 125-132 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Non-equilibrium frontal chromatography ; Nonlinear isotherms ; Variable velocity ; Multicomponent mixtures
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    Topics: Chemistry and Pharmacology
    Notes: Summary The paper presents a classification of various theoretical models for multicomponent gas chromatography at u=var for high concentrations of the mixture components with consideration of the major distinctive features of the interphase mass exchange inside the porous grains of the adsorbent and outside them within the porous medium of the chromatographic column. It has been shown that the conditions determining a given front behaviour of multicomponent gas mixture at u=var depend on: theoretical models for the kinetics and dynamics of adsorption; the values of mass exchange parameters inside the porous grains and in the porous medium. Formulae have been derived for calculating the values of the quantities characterising the frontal behaviour in the stage of adsorption and desorption of multicomponent mixture at u=var.
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    Chromatographia 25 (1988), S. 21-24 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sample concentration ; Chromatographic evaporation ; Solvent effect
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    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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  • 51
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phase polarity ; Polarity parameters ; Structure-retention relationships
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    Topics: Chemistry and Pharmacology
    Notes: Summary The new stationary phase polarity parameters BN and BS evaluated from the concept of the electric intermolecular interactions are used to describe the polarity of polyoxyethylene glycol dialkyl ethers and their sulphur analogs. Relations between the discussed parameters and accepted measures of surfactants' polarity are presented and discussed. The considered parameters are correlated with the compound structures. Structural increments for characteristic fragments of the molecule are calculated and use to predict BN and BS values.
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    Chromatographia 25 (1988), S. 134-138 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sulfur ; n-Octane adsorption
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    Topics: Chemistry and Pharmacology
    Notes: Summary From the adsorption isotherms of n-octane on the surface of sulfur at 29.8°C and 40.6°C some thermodynamic functions were determined. On the basis of these data the structure of the adsorbed layer of n-octane is postulated. The molecular interactions and adsorption mechanism are also discussed. It is stated that both quasi-liquid and quasi-sold layers may be formed on the surface of sulfur depending on the surface coverage with n-octane.
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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 25 (1988), S. 393-396 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Separation of optical isomers ; Chirasil-Val capillary columns ; Amino acid esters
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    Topics: Chemistry and Pharmacology
    Notes: Summary D,L-amino acids were derivatized with (+), (±)-2-butanol or N-trifluoroacetyl-L-prolyl chloride (L-TPC) and then chromatographed. Four optical isomers were separated on a Chirasil-Val capillary column. By this method, the concentration of optical impurities arising from the commercial optically active reagents can be determined. The observed abnormal elution orders of enantiomeric amino acid esters may be caused by a selective intermolecular force.
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  • 55
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Essential oils ; Evaporation rate ; Perfume composition
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    Topics: Chemistry and Pharmacology
    Notes: Summary A simple method was developed for the determination of the evaporation rate of essential oils and perfumery composition using gas chromatography with temperature programming. The volatility of 19 essential oils and 17 perfumery composition was evaluated. The method is useful for different comparative measurements.
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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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    Chromatographia 25 (1988), S. 609-612 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Triglyceride composition of grapes ; Identification system
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    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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    Chromatographia 25 (1988), S. 655-658 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Structure-retention relationships ; Connectivity indices, topological indices ; Alkenes
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    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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    Chromatographia 25 (1988), S. 735-736 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; α,ω-diiodoperfluoroalkanes ; Separation ; identification
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    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of α,ω-diiodoperfluoralkanes on a glass capillary column coated with OV-101 methylsilicone was investigated. Retention indices were determined at three temperatures (140, 150 and 160°C). The correlation between the retention indices and the boiling points of the investigated compounds was studied.
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    Chromatographia 25 (1988), S. 731-734 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention Index (l) ; Temperature dependence of Retention Index
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    Topics: Chemistry and Pharmacology
    Notes: Summary A linear dependence of (T−T1)/[1(T)−1(T1)] on temperature (considering the retention index 1(T1) at temperature T1 as a standard value) is derived. Both ther retention index at an assigned temperature and the temperature dependence of the retention index can be calculated from retention data measured at two temperature-programing rates.
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    Chromatographia 26 (1988), S. 171-177 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; GC/MS analysis ; Polycyclic aromatic hydrocarbons ; Bituminous coal ; Brown coal ; Plant waxes ; Thermodesorption
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    Topics: Chemistry and Pharmacology
    Notes: Summary Polycyclic aromatic hydrocarbons (PAH) today are ubiquitous detectable constituents of recent sediments. The compounds are adsorbed on particulate emissions and are thus transferred to the environment. To date the analysis of PAH in sediments, dust samples and plant material is based mainly on the application of solvent-extraction methods followed by liquid chromatography and/or gas chromatographic separation of the extracts. An alternative approach for the analysis of PAH in solid samples such as coal, sediments, dust samples and plant waxes is shown in this contribution. A commercially available device for the analysis of volatile compounds present in solid matter is connected on-line to a GC/MS system. The device enables the thermal desorption of hydrocarbons at a temperature of 320°C. Subsequently, the hydrocarbons trapped on the initial part of the capillary column are analyzed by GC/MS. The application of mass chromatography provides the possibility of detection and quantitation of PAH in complex mixtures even when they coelute with other compounds. The sample amount required varies between 1 and 10 mg depending on the hydrocarbon content.
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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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  • 63
    ISSN: 1612-1112
    Keywords: Gas chromatography ; (S)-(+)-Naproxen ; Amino acid methyl esters ; Resolution of diasteroisomers
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    Topics: Chemistry and Pharmacology
    Notes: Summary A GC method has been elaborated for the separation of enantiomers of some amino acid methyl esters after derivatization with activated (S)-(+)-naproxen. Nine amino acid ester paris were completely resolvede in a single run on a fused silica capillary column.
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    Chromatographia 25 (1988), S. 993-998 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; HPLC system ; Micropacked column ; Organic mobile phase ; UV detection
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    Topics: Chemistry and Pharmacology
    Notes: Summary Retention behaviours of aromatic hydrocarbons were examined by using the vapour of an organic substance as the mobile phase and silica gel as the stationary phase. Gas chromatographic separation of aromatic hydrocarbons was demonstrated by using a system comprising a liquid chromatographic (LC) pump, a micropacked column for LC, a column oven and a UV detector.
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  • 65
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index ; Hydrocarbons
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    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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    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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    Chromatographia 25 (1988), S. 621-626 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Pre-column photolysis ; Halogenated hydrocarbons ; Identification of photolysis products ; Reaction mechanisms
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    Topics: Chemistry and Pharmacology
    Notes: Summary Photodecomposition of chloro- and bromoderivatives of saturated, unsaturated and aromatic hydrocarbons has been studied under flow conditions using reaction gas chromatography. The photodegradation products were separated on a column coated with squalane and identified by comparing the measured retention data with those of standards and published retention indices, The results can be used to clarify the decomposition of such compounds.
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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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    Chromatographia 25 (1988), S. 817-821 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Water analysis ; Macroreticular polymeric adsorbent resins ; Herbicides
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the determination of 3-phenyl-4-hydroxy-6-chloropyridazine in potable water. The method is based on isolation and enrichment by passing the water sample through a column of macroreticular polymeric adsorbent resin, concentration, derivatisation with pentafluorobenzoyl chloride and GC measurement with a N-specific detector. The individual experiments for establishing the working conditions, especially the adsorption characteristics of different types of resin, are described. The highest enrichment efficiency is obtained with the methacrylate-type resin XAD7. In field-sampling experiments a 10cm column yields 57% recovery at 100mLmin−1 flow rate, 0.3 ppb concentration level and 1 L sample volume. The method is completely documented; performance data are a detection limit of 0.07 μg L−1 and a mean recovery of 75% at the 0.3 ppb level.
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  • 70
    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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  • 71
    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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  • 72
    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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  • 73
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    Chromatographia 25 (1988), S. 87-90 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Free acids in cheese ; Tetramethylammonium hydroxide soaps ; Packed and capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid gas chromatographic method for the analysis of individual free fatty acids (FFA) in cheese has been developed. Lipds were extract from a cheese paste acidified with diethyl ether and tetramethylammonium hydroxide (TMAM) was used for converting the FFA to TMA-soaps, which are transformed to methyl esters in the chromatographic injector. The effect of lactic acid was determined. The reproducibility of the method was studied and the coefficient of variation for the total FFA was found to be 2.2%. Recovery of individual FFA was in the range 87 to 106%.
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  • 74
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    Chromatographia 25 (1988), S. 453-454 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Reversed-flow technique ; Polymer activities ; Polymer interaction parameters
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    Topics: Chemistry and Pharmacology
    Notes: Summary The reversed-flow, gas-chromatographic method for measuring activities and activity coefficients in binary liquid mixtures is now extended to the determination of activity coefficients of the solvent in polymer-solvent systems over the whole range of polymer concentration, as well as for the calculation of Flory-Huggins interaction parameters. The parameters found by the present method are compared with those determined by other techniques or calculated theoretically.
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  • 75
    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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  • 76
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    Chromatographia 25 (1988), S. 547-559 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid column chromatography ; Process scale separations ; Review
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    Topics: Chemistry and Pharmacology
    Notes: Summary The relative merits of large scale gas chromatography (GC) and high performance liquid chromatography (HPLC) have not been reviewed for some considerable time. Although methodologies capable of manufacturing high efficiency (and hence cost effective) plant have existed for over a decade, commercial introduction has been remarkably slow. This has primarily been caused by confidentiality restrictions placed on equipment manufacturers, in turn severely limiting wide ranging applications data. These are necessary to raise potential end users confidence that both techniques offer viable large scale routes to separation and purification of mixtures as analysed by laboratory chromatographic methods. Considerable recent progress has been made with large scale HPLC plant, which has led to sufficient published data to make both technical and economic comparisons against GC possible.
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  • 77
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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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  • 78
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    Chromatographia 25 (1988), S. 691-693 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Al, Cr, Co and Fe acetylacetonates ; Capillary column separation
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    Topics: Chemistry and Pharmacology
    Notes: Summary The retention and resolution of simple mixture of Al(III), Cr(III), Co(III), and Fe(III) acetylacetonates were investigated on capillary columns coated with methyl and methyl phenyl silicones (OV-1 or OV-17) used as the stationary phase, at different column temperatures and carrier gas flow rates. Successful elution and good resolution were obtained only for the Al(III) and Cr(III) complexes, both under isothermal and programmed-temperature conditions; better resolution was observed on the column coated with OV 17.
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  • 79
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    Chromatographia 26 (1988), S. 300-304 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Polycyclic aromatic hydrocarbons ; Phenolic compounds ; Air pollution
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    Topics: Chemistry and Pharmacology
    Notes: Summary An improved procedure for the determination of the less volatile air pollutants of recycled closed atmospheres by activated carbon-Soxhlet extraction is proposed. After total treatment of desorbate, PAH determination is then accomplished by RP-HPLC using both adsorptiometric and fluorimetric UV detection; phenolic compounds are determined by GC-MS. This technique is suitable for very low levels of PAH and phenolic compounds.
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  • 80
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    Chromatographia 26 (1988), S. 34-36 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas analysis in halogen lamps ; Sampling device
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    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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  • 81
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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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  • 82
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    Trees 1 (1987), S. 94-101 
    ISSN: 1432-2285
    Keywords: Monoterpenes ; Abies alba Mill ; Resin ; Seeds ; Gas chromatography
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    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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  • 83
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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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  • 84
    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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  • 85
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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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  • 86
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Esterification in aqueous solution ; n-Propyl esters of aromatic polycarboxylic acids
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    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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  • 87
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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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  • 88
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Prediction of retention volume ; Porous polymers coated with liquid phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new expression which permits the prediction of the net retention volumes in gas chromatography with column packings of coated porous polymers is reported. The porous polymers Chromosorb 101 and Chromosorb 102 were used as supports and squalane, Ethofat and Carbowax 20M as stationary phases at three different column temperatures of 80°C, 100°C and 150°C. Several organic compounds of various polarity were used as test compounds and the net retention volumes, VNtheor, have been calculated according to this new expression. The VNtheor values were compared with the experimental net retention volumes, VNexp, and it was found that the difference between these two values is dependent on the type of compound and column packing. Nevertheless, the elution order could be predicted in most cases.
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  • 89
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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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  • 90
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary columns ; Immobilized Carbowax-type stationary phases ; Free fatty acids analysis
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    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary columns coated with acid-modified poly-(ethylene glycol)-type immobilized stationary phases have been studied. The thermostability and chromatographic behaviour of the columns and the stability of the coated films after washing with different solvents were investigated.
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  • 91
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fourier transform IR detection ; Headspace sampling ; Solvents of abuse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary After experimental intoxication of rats, gas chromatography — Fourier transform infrared spectrometry with headspace sampling (HS/GC/FT-IR) was used to identify solvents of abuse in biological material (blood, liver, lungs and brain). Limits of detection were measured for acetone, 2-butanone, ether, toluene and trichlorethylene with standard solutions. All the solvents have been identified in the organs of the intoxicated rats. For blood samples a salting-out effect was obtained with potassium carbonate. HS/GC/FT-IR allowed the identification of metabolites of acetone (isopropanol) and of 2-butanone (2-butanol) in blood and organs.
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  • 92
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Physico-chemical properties ; Retention indices ; Cycloolefins
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    Topics: Chemistry and Pharmacology
    Notes: Summary The retention indices of mono and polycycloolefins with endo or exo double bonds, on squalane or polypropylenglycol 425 are related to their physico-chemical properties such as boiling point, molar volume, molar refraction, and refractive index. Equations have been empirically obtained, from which accurate retention indices of these compounds can be predicted. Unknown boiling points of some of these compounds can also be calculated from their lineal relation with the retention index on squalane.
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  • 93
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    Chromatographia 23 (1987), S. 839-843 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phases ; Porous polymer beads ; Polarity ; Adsorbents ; Breakthrough volume
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    Topics: Chemistry and Pharmacology
    Notes: Summary The breakthrough volume of ådsorbent traps made with porous polymer beads Porapak N, P. Q, R, S was evaluated by analysis of polarity reference substances proposed by Rohrschneider (ethanol, methyl ethyl ketone, nitrometane, benzene, pyridine) by McReynolds (butanol, methyl propyl ketone) and of the first term of some homologous series: alcohols, aldehides, carboxilic acids, nitrocompounds, iodoalkanes and nitriles. Adjusted retention times of the compounds were measured at 200°C and correlated with the physical properties and with polarity class according to Ewell. Trapping efficiency of the various Porapak types was evaluated and the theoretical breakthrough volumes at 25°C was calculated for the used test substances.
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  • 94
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    Chromatographia 23 (1987), S. 850-855 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary columns ; Bacterial cellular fatty acids ; Stationary phase selectivity ; Solid phase preseparation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The importance of selectivity in the capillary gas chromatographic analysis of the cellular fatty acids of micro-organisms is underestimated. The analysis on apolar silicone phases can lead to erratic elucidation of the fatty acid structure. Qualitative errors have been detected in commercially available standards on which computer matching identification techniques are based. Using highly polar capillary columns of the cyanopropyl silicone type, the errors could be elucidated. The exact identification of the hydrolysis products of bacteria is a must for chemotaxonomic studies applying chromatographic techniques. The fatty acid methyl ester profiles can also contain other chemical components which are very important taxonomic markers. Fatty aldehydes, for example, are main components in someClostridium species. Fractionation techniques are described for selective enrichment of fatty aldehydes and hydroxy fatty acids.
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  • 95
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    Chromatographia 23 (1987), S. 215-219 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid chromatography ; Thermodynamic equilibria ; Solution and adsorption thermodynamics ; Gas adsorption isotherms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary After a brief recall of the chromatographic principles, the different applications of gas chromatographic measurements of thermodynamic equilibria were reviewed. Gas and liquid chromatographies are now well known and elegant methods for measuring the physicochemical properties and phase equilibrium thermodynamic constants. Although fundamentally a dynamical method and mostly known as a powerful separation technique, chromatography can be schematized by a sucession of equilbria of a chemical species partitioning between a mobile phase and a fixed liquid or solid stationary phase. It can be operated in either infinite dilution or finite concentration conditions and permits to collect a large number of data for calculating molecular interactions for solutes which are either rare or available at the trace level. Gas chromatography permits the measurement of gas adsorption isotherm, gas-liquid equilibria, molecular diffusion and interaction virials. The modelization of successive partition equuilibria occuring in the chromatographic column leads to rather simple expression of differential enthalpy, entropy, free energy of adsorption or solution, variation of heat capacity, complexation constant, second virial coefficients, gas-solid and gasliquid isotherm and also binary or ternary equilibria. The possibilities of High Performance-Liquid Chromatography to investigate adsorption from solutions and chemical equilibria are also discussed.
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  • 96
    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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  • 97
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Nitrogen-specific detector ; Flash methylation ; Barbital and pentobarbital ; Blood analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and simplified method is described for the determination of barbital (B) and pentobarbital (PB) in blood using gas chromatography with a nitrogen-specific flame ionization detector. After a simple one-step extraction, B and PB were reconstituted in trimethylanilinium hydroxide and introduced directly into the gas chromatograph. Lower limits of detection was 0.14 μg/ml for B and PB in either water or blood solutions. The recoveries for B from water and blood were 90 and 88%, respectively; for PB they were essentially complete. The average between-run and within-run coefficients of variation for B from water and blood were lower than 7.8%, whereas those of PB were lower than 3.0%. The scale and sensitivity of detection for B and PB were found to be suitable for use in pharmacokinetic studies in the rat.
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  • 98
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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
    Source: Springer Online Journal Archives 1860-2000
    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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  • 99
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Backflushing, peak-cutting technique ; Trace analysis
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    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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  • 100
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Alkylthiazoles ; Energy contributions of the alkyl groups ; Retention indices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention indices and their energy equivalents were determined for ten alkylthiazoles analysed on the stationary phases Apiezon L, Triton X-305 and Carbowax 1000. It was found that the energy contributions of identical alkyl groups to the partial molar free energy of sorption of a molecule are not equivalent. Smaller energy contribututions are due to the α-position of alkyl groups with respect to the heteroatoms in the thiazole ring (α-effect). This effect was most pronounced for 2-alkylthiazoles. Higher sorption energies were found for dimethylthiazoles with two methylgroups in a vicinal position. The retention indices were predicted for ten other di- and tri-substituted methyl, ethyl and propyl thiazoles on the basis of the so-called α- and ortho-effects. The predicted values are in good agreement with the experimentally determined values.
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