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  • 1995-1999  (211)
  • 1980-1984  (413)
  • Gas chromatography
  • Nuclear reactions
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European food research and technology 209 (1999), S. 400-406 
    ISSN: 1438-2385
    Keywords: Key words Pumpkin seed oil ; Oil adulteration ; Δ7-Phytosterols ; Sample clean-up procedure ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A simple and accurate method for the determination of phytosterols by capillary gas chromatography was developed for the analysis of the seeds and oil of the pumpkin Cucurbita pepo L., the naked seed variety growing in the southern Styrian parts of Austria. After extraction of the oil and saponification, the remaining unsaponifiable material was isolated and purified using silica gel columns. For greater volatility, the sterols were derivatised to trimethylsilylethers, and gas chromatography was performed on a column of high polarity, allowing separation of the Δ5-sterols from the Δ7-sterols and thus yielding a typical chromatographical pattern. Quantification of the phytosterols using 5α-cholestan or cholesterol as internal standards led to a method of high accuracy. Comparison of the chromatographic pattern of the phytosterol fraction of pumpkin seed oil with those of other vegetable oil samples permitted the use of this method to detect adulteration of pumpkin seed oil.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 268-272 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass spectrometry ; Analytical pyrolysis ; Chinese art objects ; Mercury analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A few samples of polychrome Chinese archaeological objects of art have undergone analytical pyrolysis coupled with GC-MS to evaluated the possibility of contemporary characterization of the pigments as well as the organic media used. The red pigment cinnabar (HgS) is easily media used. The red pigment cinnabar (HgS) is easily detected, whereas in the case of organic components positive results are only found where the matrices are resistant to archaeological environmental conditions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 321-326 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace analysis ; Open-tubular trap ; Very thick film column
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An open-tubular trap with a very thick film was studied for “full on-line” headspace capillary gas chromatography, and was used as an enrichment trap for headspace sampling. The preparation of the open-tubular column with up to an 80 μm thick film, by combining both static and dynamic coating, is described in detail. The break-through volume for the open-tubular trap of different film thickness, as the loading capacity for HS sampling, does not increase linearly in proportion to the film thickness. A study of the difference between a packed adsorbent trap and an open-tubular trap shows that HS capillary GC with open-tubular trap loses less of the retention capacity, has better resolution ability and higher recovery. By independently and rapidly heating the open-tubular trap, the GC peaks may have higher resolution. Examples of successful analyses, by the opentubular trap with “full on-line” HS capillary GC, include trace aromatic hydrocarbon (1 ppm-100 ppm) in polybutadiene-styrene rubber and trace alcohol and acrylic esters (10 ppm–1000 ppm) in polyacrylate hydrous emulsion.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Supercritical fluid chromatography ; Solvating gas chromatography ; Polybutadiene coated zirconia ; CO2 mobile phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this paper, practical considerations of column efficiency, separation speed, thermal stability, and column polarity of capillary columns packed with polybutadiene-coated zirconia were investigated under solvating gas chromatography (SGC) conditions using carbon dioxide as mobile phase. When compared with results obtained from conventional porous octadecyl obtained from conventional porous octadecyl bonded silica (ODS) particles, PBD-zirconia particles produced greater change in mobile phase linear velocity with pressure than conventional ODS particles under the same conditions. The maximum plate number per second (Nt) obtained with a 30 cm PBD-zirconia column was approximately 1.5 times higher than that obtained with an ODS column at 100 °C. Therefore, the PBD-zirconia phase is more suitable for fast separations than conventional ODS particles in SGC. Maximum plate numbers per meter of 76,900 and 63,300 were obtained using a 57 cm×250 μm i.d. fused silica capillary column packed with 3 μm PBD-zirconia at 50 °C and 100 °C, respectively. The PBD-zirconia phase was stable at temperatures up to 320 °C under SGC conditions using carbon dioxide as mobile phase. Polarizable aromatic compounds and low molecular weight ketones and aldehydes were eluted with symmetrical peaks from a 10 cm column packed with 3 μm PBD-zirconia. Zirconia phases with greater inertness are required for the analysis of more polar compounds by SGC.
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  • 5
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Average column pressure ; Average column flow ; Specific retention volume ; Distribution coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A systematic derivation of corresponding equations shows that averaging the pressure and the flow rate of the mobile phase in a gas chromatographic column over the column length and over the time that an unretained component resides in the column, requires the use of three different compressibility correction factors,j 2 1 ,j 3 2 , andj 4 3 . When multiplied by the adjusted retention volume,V R-VM, the Martin and James mobile phase compressibility correction factorj 3 2 , only, produces the value of specific retention volume,V g T , which is connected unambiguously with the thermodynamic phase distribution coefficient,K, of the sorbate.
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  • 6
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sorptive preconcentration ; Air monitoring ; Nicotine ; Hospital air
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A novel method for the enrichment of nicotine from gaseous samples is presented. It is based on the sampling of 6 liters of air onto a cartridge packed with 100% polydimethylsiloxane (PDMS) particles. The analytes are dissolved (partitioned) into the PDMS phase which results in much better recoveries and reproducibilities compared to those obtained on common adsorbents. The PDMS tube is then placed in a thermal desorption (TD) unit connected to a CGC-NPD or CGC-MS system. The procedure was employed for routinely monitoring air in a hospital. Nicotine was typically found at levels ranging from 5 to 250 μg m−3 (ppb) depending on the location and number of smokers present. Additionally, the efficiency of nicotine filters was determined by sampling simultaneously at the filter in- and outlet and was found to be 46%.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Rechtsmedizin 9 (1999), S. 184-189 
    ISSN: 1434-5196
    Keywords: Key words Ethyl glucuronide ; Congeners of alcoholic beverages ; Alkyl glucuronide ; Gas chromatography ; Mass spectrometry ; Schlüsselwörter Ethylglucuronid ; Begleitstoffe ; Alkylglucuronid ; Gaschromatographie ; Massenspektrometrie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Es wird die chemische Synthese von Alkylglucuroniden beschrieben, die nach Konsum von begleitstoffhaltigen Getränken als Metaboliten im Urin erscheinen. Von folgenden Alkoholen wurden die Glucuronide synthetisiert: Methanol, d5-Ethanol, Propanol, Isopropanol, Butanol, Isobutanol, R-(–)-2-Butanol, S-(+)-2-Butanol, Isopentanol, S-(–)-2-Methylbutanol. Die Retentionsindizes der Acetyl-, Pentafluorpropyl(PFP)- und Trimethylsilyl(TMS)-derivate werden mitgeteilt und der Einfluß der chemischen Struktur auf den RI-Wert diskutiert. Die Massenspektren der homologen Derivate erwiesen sich als sehr ähnlich, aber einige Fragmente sind spezifisch für die Kettenlänge der Alkylgruppe und können zur Identifizierung und Quantifizierung der Glucuronide in Urinproben herangezogen werden.
    Notes: Abstract The chemical synthesis of alkyl glucuronides, which appear as metabolites in urine after the consumption of beverages containing congeners of ethanol, is described. Glucuronides of the following alcohols were synthesized: methanol, d5-ethanol, propanol, isopropanol, butanol, isobutanol, R-(–)-2-butanol, S-(+)-2-butanol, isopentanol and S-(–)-2-methylbutanol. The retention indices of acetyl, pentafluorpropyl (PFP) and trimethylsilyl (TMS) derivatives are given and discussed in relation to the chemical structures. Mass spectra of homologous derivatives were shown to be very similar but some fragments were specific for the chain length of the alkyl moiety and can be used for identification and a quantitative estimation of glucuronides in urine samples.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    International journal of legal medicine 112 (1999), S. 124-131 
    ISSN: 1437-1596
    Keywords: Key words Hydroxyproline ; D/L Aspartic acid ; N-TFA isopropyl ester derivatives ; Gas chromatography ; Collagen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Notes: Abstract The proportion of D- to L-enantiomers of aspartic acid in metabolically isolated proteins has been used by forensic scientists to estimate age at death. We have demonstrated the interference of a derivative of hydroxyproline (N-TFA isopropyl Hyp ester) with the N-TFA isopropyl L-Aspartic (Asp) acid ester during gas chromatography of amino acids. This has serious implications for the accurate quantification of the D- to L-Asp ratio extracted from collagenous proteins. Having demonstrated the potential for this co-elution in amino acid standards, acid-soluble dentine proteins and non-mineralised collagen, we argue that this problem can be overcome either by high resolution separation or by analysis of the (Hyp-poor) non-collagenous protein fraction.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Microwave and ultrasonic extraction ; River sediment ; Dioxin-like polychlorobiphenyls ; Toxic equivalency factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Microwave extraction and ultrasonication of dioxin-like polychlorobiphenyls (PCBs) from sediment samples were investigated. After separation of dioxin-like PCBs from a sample matrix on an acidic-alkaline silica gel column, dioxin-like PCBs were determined by GC-ECD, using dual capillary columns. Recoveries of dioxin-like PCBs in river sediment samples exceeded 80% by both extraction techniques. Toxic equivalency factors and their use for the PCB congeners investigated were applied.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 273-280 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Complexation stationary phases ; Bonding metal complexes ; Capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of polysiloxanes with cyano or thiol groups as stationary phases for complexation gas chromatography is discussed. The polymers were obtained via polycondensation followed by polymerisation of the corresponding dichloro- or dimethoxy-silanes. Both the phases were modified by bonding transition metal chlorides with were modified by bonding transition metal chlorides with cyano (CuCl2 or CoCl2) and thiol groups (NiCl2 or CoCl2). The phases were examined in order to determine their application to the analysis of ethers, thioethers and ketones. Due to the presence of lone electron pairs on oxygen or sulphur atoms, the compounds should be capable of specific interacting with the electron-withdrawing centre of the liquid stationary phases. A number of retention parameters (retention indices, molecular retention indices and specific retention volume) were determined, which allowed characterisation of specific interactions between the bonded metal and the compound analysed. The results also enabled assessment of the influence of the structure of the compounds on their retention. The measurements were also carried out for the phases with free SH and CN groups as reference phases. The work demonstrates that the phases obtained may be useful for effective separations.
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  • 11
    ISSN: 1612-1112
    Keywords: Gas chromatography ; [60] Fulleropyrrolidine polysiloxane ; High temperature stationary phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this paper, a new type of [60]fulleropyrrolidine functionalized polysiloxane in which the fullerene moieties were incorporated in the main polysiloxane chain was synthesized the first time and used as a stationary phase for capillary gas chromatography. It demonstrated high column efficiency (2600–2866 plates m−1, on a 250 μm diameter column, for naphthalenek=3.1–3.2, 120 °C), a wide operational temperature range (90–360 °C) and outstanding thermostability. It can be used at 360 °C with a baseline drift of 5∼8×10−15A. Benzene homologues, aromatic hydrocarbons, polar compounds such as alcohols, esters, ketones, anilines and phthalic diesters can be seperated well on this column.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 385-390 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Structure correlations ; Polycyclic aromatic hydrocarbons ; Polychlorinated biphenyls ; Polychlorinated pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A composite chromatographic retention index system has been developed for identifying polycyclic aromatic hydrocarbons, polychlorinated biphenyls and polychlorinated pesticides. When retention indices and thermodynamic data of polycyclic aromatic hydrocarbons on 5% phenylmethylsiloxane stationary phase were compared with those obtained on polydimethylsiloxane a correlation was found between retention and electronic properties. Determination and quantitation of individual contaminants in water and sediment samples from Lake Mecoacán were achieved by capillary gas chromatography with flame ionization and electrocapture detection.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 509-512 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Homologous series ; Retention times
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is shown how to estimate the retention times of homologous series members in linear temperature programmed gas chromatography with the aid of a spread-sheet. Both the ease of estimation and the accuracy of the estimation depend on whether the homologue is eluted during the rising portion of the temperature program or the hold time at the end, and also on whether the homologous series is eluted from one injection or a number of injections. When all members of the series elute in the one chromatographic run the percentage standard deviation of the predicted retention times from the experimental retention times is 0.1. When members of the series elute in different chromatographic runs, the percentage standard deviation of predicted times from experimental times is 0.6, compared with an experimental percentage standard deviation for replicates of 0.5.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 513-519 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid phase microextraction ; Open cap vials ; Volatile compounds (BTEX) ; Water matrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The testing of open cap vials in headspace solid-phase microextraction combined with capillary gas chromatography is reported. The losses of volatile analytes from such vials were analyzed theoretically and investigated experimentally. The benzene, toluene, ethylbenzene, and xylene isomers spiked in water were used as model compounds. Extraction yields and precision obtained under optimized experimental conditions as exposure time, desorption time and temperature were compared applying vials with open caps or sealed with teflon lined septa.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 567-571 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mixed stationary phase ; Calixarenes ; Crown ethers ; Cyclodextrins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Mixed stationary phases containing of 25,27-dibutoxy-5,11,17,23-tetra-tert-butyl-26,28-diundecenyloxy calix [4]arene (C[4]B)+ω-undecylomethyl-18-crown-6 polysiloxane (PSO-11-18-C-6) and C[4]B polysiloxane (PSO-C[4]B)+permethyl-β-cyclodextrin (PM-β-CD) were investigated in capillary gas chromatography. By comparing their selectivity for positional isomers with that of the corresponding individual pure stationary phases, synergistic effects were found.
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid-phase microextraction ; Fibre coating ; Volatile organic compounds ; Semi-volatile organic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The efficiency of direct solid-phase microextraction (SPME) was determined for 27 selected volatile and semivolatile organic compounds (BTEX, chloro- and bromobenzenes, chlorinated pesticides and PCBs). The fibres used were 7μm polydimethylsiloxane (PDMS), 30μm PDMS, 100μm PDMS, 65μm PDMS-divinylbenzene, 85μm polyacrylate, 65μm Carbowax-divinylbenzene, 75μm Carboxen-PDMS and a new 65μm C8 fibre. Extraction yields for these compounds were calculated under standardised conditions: 75μm Carboxen-PDMS was found to be the most efficient fibre for compounds with low boiling points. Although 65μm C8 can be used for extraction of all compounds studied, in no one case is it the most effective coating. 100μm PDMS and the more polar coatings can be used for a broad range of compounds, whereas application of 7μm and 30μm PDMS cannot be recommended. Inter-fibre comparison revealed significant differences between three different Carboxen-PDMS fibres. The results enable suitable coatings to be chosen for each of the 27 compounds and for substances with similar properties.
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  • 17
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Cisplatin determination ; Blood analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary gas chromatographic method is described for the determination of cisplatin based on the complexation of platinum(II) with bis(isovalerylacetone) ethylenediimine (H2IVA2en) and extraction in chloroform. The chromatography was carried out on a BP1 or a BP5 column with an FID. Copper(II), nickel (II) and palladium(II) separated completely and did not affect the determination of platinum(II). The method was applied of the determination of cisplatin in a pharmaceutical preparation and blood samples of cancer patients after infusion of cisplatin. The amounts of cisplatin in blood were found to be within 246–283 ng mL−1 with a C.V. of 2.35–4.26%.
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  • 18
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Reversed-flow gas chromatography ; Carbon monoxide oxidation ; Bimetallic Pt−Rh catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Catalytic fractional conversions of carbon monoxide to carbon dioxide over Pt−Rh alloy catalysts in the presence of excess oxygen, under steady-state or non steady-state conditions, as well as corresponding rate constants for the CO oxidation reaction were measured by using the reversed-flow gas chromatographic technique. From the variation of the conversions with temperature, maximum values of conversions were found, which depend on the catalysts nature (Pt content), while from the variation of the rate constants with temperature, activation energies for the CO oxidation reaction were determined, which also depend on the catalyst Pt content. The results suggest a synergism between Pt and Rh in the Pt−Rh bimetallic catalysts in accordance with previous works, showing that reversed-flow gas chromatography can be used with simplicity and accuracy for the kinetic study of the CO oxidation reaction, which is of technological importance for the control of air pollution.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 333-337 
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Gas chromatography ; Solvating gas chromatography ; Peak capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this paper, a general peak capacity expression was evaluated using columns containing various packing materials under solvating gas chromatography (SGC) conditions. Differing from column efficiency, peak capacity can describe both separation capability and speed when introducing the dead time into the peak capacity expression. Various factors that influence peak capacity in SGC are described, including particle pore size, chemical surface modification, particle size, column length, temperature, and pressure.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 399-405 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid phase adsorption ; Supercritical fluid extraction ; Sewage ; Organic pollutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Analytical methods have been developed for the determination of organic pollutants of intermediate polarity in sewage. Water samples are first passed through a solid phase adsorption cartridge. The analytes are then extracted from the absorbent with supercritical CO2 into a small volume of trapping solvent. Finally, the extracts are analyzed directly by capillary gas chromatography and gas chromatography-mass spectrometer. The various parameters (pressure, temperature, type and concentration of modifiers, trapping solvent, flow rate and volume of supercritical fluid and equilibrium time) influencing the efficiency of extraction were studied. Extraction efficiencies for the test compounds are 〉70%, and relative standard deviations are 〈4.6% (n=3). The methods established were applied to the analysis of sewage at the Lanzhou Wastewater Treatment Plant, China. 66 organic pollutants were detected, of which 15 compounds appeared in the list of priority pollutants suggested by the US EPA.
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  • 21
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Electron capture detector ; Anti-picornaviral agent in dog serum ; Enteroviruses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic assay for the determination of SCH 48973, a potent broad spectrum anti-picornaviral agent, was developed and validated in dog serum. The method involved extraction with organic solvent followed by separation on a capillary column (DB-1) with quantitation by an electron-capture detector. The method was sensitive with a limit of quantitation of 10 ng mL−1. The linearity of the method was satisfactory as indicated by correlation coefficients of 〉0.999 and visual examination of the calibration curves. The method was precise with a coefficient of variation ranging from 2.3 to 13.2% and accurate with a bias ranging from −9.1 to 7.9%. Moreover, SCH 48973 was stable in dog serum after being subjected to three freeze-thaw cycles. The assay was shown to be sensitive, specific, accurate and precise, and reliable for use in pharmacokinetic or toxicokinetic studies.
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  • 22
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 181-182 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; microwave induced emission spectrometry ; speciation ; mercury ; SPME, headspace SPME ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 23
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 294-296 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; capillary ; fused silica ; rotenone ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 3 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 303-304 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; food analysis ; pesticide residues ; thiabendazole ; imazalil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 25
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 395-402 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; pulsed splitless injection ; pesticide residues ; matrix effects ; retention gap ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The applicability of pulsed splitless injection to the gas chromatographic analysis of pesticide residues in fruit and vegetables has been evaluated. 22 pesticides belonging to different chemical classes, including those known to be liable to matrix induced response enhancement, were selected for the study. The parameters of pressure pulse have been tested for optimum performance of injection. Application of the pressure pulse was found to decrease matrix effects during analyses of real samples. Further decline of matrix effects was obtained using higher sample injection volumes. The installation of a deactivated retention gap was necessary to obtain good peak shapes with injection volumes exceeding 1 μL of sample. Up to 4 μL was then injected without peak distortion and consequent loss of resolution. Using 4 μL pulsed splitless injection, matrix effects were almost completely eliminated even at very low concentration levels of analytes. The highest matrix effects observed for tested compounds at the lowest concentration level tested were in the range of 110-122%.
    Additional Material: 3 Ill.
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  • 26
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 565-588 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Kovats retention index ; vapor pressure ; boiling point ; Wilson activity coefficient ; binary phase diagrams ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Non-ideal mixing in a dimethylsilicone stationary phase is modeled according to the Wilson activity coefficient. Pure liquid vapor pressures of alkylated compound series are calculated from capillary GLC retention with the functional group heat of solution in a polymer solvent. The new method uses the Kovats index, molar mass, and functional group to determine the bubble line of a compound. Boiling points at reduced and normal pressure are compared to literature values of 194 gasoline components. An unlike molecular pair interaction parameter is derived, using only bubble line data of the pure liquids. Binary phase diagrams are constructed and compared to vapor liquid equilibrium data.
    Additional Material: 22 Ill.
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  • 27
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 24-28 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; ECD ; Micro-ECD ; GC detector ; organochlorine pesticides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A new ECD, the HP 6890 Series Micro-ECD, was designed to address inherent deficiencies in classical electron capture detectors (ECD), especially with respect to sensitivity, linearity, dynamic range, and ruggedness. Several novel technologies were incorporated in the totally new design and were refined through practical testing and user feedback. Validation of the micro-ECD performance was accomplished through side-by-side testing of the Micro-ECD with previous ECDs following US EPA Contract Laboratory Program methods for pesticides and PCBs. In addition, extensive interviews were conducted with early users of the Micro-ECD who also had experience with other designs running a variety of ECD methods. The design and resulting performance improvements are described.
    Additional Material: 6 Ill.
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  • 28
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    Electronic Resource
    Springer
    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 206 (1998), S. 48-51 
    ISSN: 1431-4630
    Keywords: Key words Carbohydrates ; Myo-inositol ; Orange juice quality ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A gas chromatographic method using a capillary column is described for the quantitative analysis of fructose, glucose, sucrose and myo-inositol in orange juice. The method is evaluated for precision and recovery using phenyl-β-glucoside as an internal standard. The results support the suitability of the method. Carbohydrates (fructose, glucose, sucrose and myo-inositol) were determined in different kinds of orange juice. The determination of carbohydrate composition and ratios of the carbohydrate constituents provide a method to assess orange juice quality, especially the myo-inositol content and myo-inositol/fructose ratio. These new indices, which were found to be lower in samples made from concentrates, provide information on the quality and genuineness of orange juice.
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  • 29
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    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 206 (1998), S. 213-216 
    ISSN: 1431-4630
    Keywords: Key words Milk fat ; Mixed fat ; Milk fat content ; Butyric acid ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The analysis of butyric acid (C4) is of importance for the determination of the proportion of milk fat in mixed fats. Three gas chromatographic methods were compared with regard to their precision for the measurement of C4, i.e. analysis of butyric acid methyl ester after trans-esterification of fat by sodium methylate (method A) or trimethyl sulphonium hydroxide (method B), as well as analysis of free butyric acid (method C), using an internal standard with each method. The examination of 30 milk fats which varied greatly in terms of their C4 content, using methods A, B and C, resulted in mean values of C4 of 3.42 g/100 g fat, 3.71 g/100 g fat and 3.06 g/100 g fat, respectively. The value determined using method B seemed too high, and this may have been due to the presence of co-eluting artefacts, whereas the value determined using method C was clearly too low, and can probably be attributed to losses during sample preparation. The standard deviation (SD) of 0.015 obtained from repeated analyses using method A was quite good. Results obtained using methods B and C had SDs of 0.029 and 0.074, respectively. Different levels of free fatty acids did not affect the results obtained using method A. When method A was checked by analysis of the reference fat, CRM 164, the C4 level determined was found to deviate from the certified C4 content of 3.49 (± 0.06) g/100 g fat by only 0.05 g C4/fat 100 g. Thus method A proved the most suitable for the determination of the proportion of milk fat in mixed fats by analysis of butyric acid.
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  • 30
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    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 207 (1998), S. 180-181 
    ISSN: 1431-4630
    Keywords: Key words UHT milk ; Storage ; Monosaccharides ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Changes in the free monosaccharide fraction and non-casein nitrogen during the 3-month storage of five batches of commercial UHT milk were studied. Batches with high residual proteolytic activity showed a considerable increase in galactose, N–acetyl glucosamine and N–acetyl galactosamine levels during the storage period, whereas their glucose and myo-inositol contents remained unaltered. In batches with slight or negligible proteolytic activity no changes in the free monosaccharide fraction were observed.
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  • 31
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    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 206 (1998), S. 77-82 
    ISSN: 1431-4630
    Keywords: Key words Anticarcinogen ; CLA ; Conjugated linoleic acid ; Daily intake ; Foods ; Gas chromatography ; Lipids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The quantities of the biologically active isomer of conjugated linoleic acid (CLA) – C18:2 c9t11 – in 139 German foods were analysed by capillary gas chromatography (results are given as a % of all identified fatty acid methyl esters). The CLA content ranged from 0.40% (Gouda) to 1.70% (Jurassic cheese, Old Emmentaler) in dairy products, from 0.11% (rabbit) to 1.20% (lamb) in meat, and from 0.01% (pike-perch) to 0.09% (carp) in fish. CLA could be detected in neither vegetable fats or oils nor in margarines (CLA 〈0.01%). Crisps, chocolates, cakes and pastries, and other foods have only a negligible CLA content. The average estimated CLA intake in Germany was calculated to be 0.35g CLA/day for women and 0.43g CLA/day for men.
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  • 32
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    Intensive care medicine 24 (1998), S. 415-421 
    ISSN: 1432-1238
    Keywords: Key words Acetone ; Gas chromatography ; Isoprene ; Lipid peroxidation ; Microwave desorption ; N-pentane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: Application of a new method for analysis of exhaled gas in critically ill patients. Design: Open study. Setting: Surgical intensive care unit of an university hospital. Patients: Thirty-seven consecutive, critically ill, mechanically ventilated patients. Interventions: None. Measurements and results: Chemical analysis of the patient's exhaled gas was based upon substance adsorption and concentration onto activated charcoal, microwave desorption and gas chromatographic separation. Patients with acute respiratory distress syndrome (ARDS) exhaled less isoprene than those without ARDS [9.8 (8.2–21.6) vs 21.8 (13.9–41.4) nmol/m2 per min [median (95 % confidence interval)], p = 0.04]. In patients who developed pulmonary infection, pentane elimination increased from 0.4 (0.0–5.4) to 2.7 (0.6–6.1, p = 0.05) nmol/m2 per min and isoprene elimination decreased from 5.2 (0–33) to 5.0 (0–17, p = 0.05) nmol/m2 per min, resulting in a significant increase in pentane/isoprene ratio from 0.1 (0–0.3) to 0.4 (0–15, p = 0.007) when compared to patients without pulmonary infection. Conclusions: The new method allows quantitative analysis of human gas samples with low substance concentrations and is well suited for clinical studies which involve the investigation of metabolic processes in the lung and the body.
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  • 33
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    Chromatographia 47 (1998), S. 305-308 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Silicone phases ; Film thickness ; Large-bore capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A technique is described for determination of the amount of bonded phase in commercial columns. It is adapted to the determination of the real nature and the thickness of a siloxane bonded film. Ten-centimeter samples of column are used. The method is tested for large-bore capillary columns. Applications to kinetic studies are suggested.
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  • 34
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    Chromatographia 47 (1998), S. 313-345 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sample pretreatment ; Coupling on-line to capillary GC ; Robotization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sample pretreatment is often the bottleneck of a tracelevel analytical procedure. In order to increase performance, increasing attention is therefore being devoted to combining sample pretreatment on-line with the separation technique that has to be used. In the present review, a variety of procedures in use today for sample treatment coupled on-line to capillary gas chromatography (GC) is briefly discussed. Special attention is devoted to coupled-column techniques such as SPE-GC and LC-GC (SPE, solid-phase extraction; LC, column liquid chromatography) which are topics of much current interest, also because of their frequent use in so-called hyphenated systems.
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  • 35
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chiral stationary phases ; Enantioseparation ; Toxaphene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of the enantiomers of the compounds of technical toxaphene (CTTs) on heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin (β-TBDM) has been studied by gas chromatography with electron-capture detection (GC-ECD). Enantiomers of eight of the nine CTTs under investigation were separated on this chiral stationary phase. Separations of the enantioners of CTTs have hitherto been achieved ontert-butyldimethylsilylated β-cyclodextrin (β-BSCD). The chiral resolution values and separation factors of the CTTs on β-TBDM have been compared with those obtained on β-BSCD. Although several components coeluted, enantioselective determination of three CTTs was possible in an extract of seal blubber. For each CTT the first-eluting enantiomer was enantioenriched. Enantioselective accumulation of2-endo, 3-exo,5-endo,6-exo,-8,8,9,10-octachlorobornane (B8-1412) in biota has been established for the first time.
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  • 36
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mixed stationary phases ; Dibenzo-18-crown-6 ether ; MPBHpB ; Synergistic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synergistic effect is investigated in mixed gas chromatographic stationary phases containing dibenzo-18-crown-6 +MPBHpB [o-methyl-p-phenylene-bis-(p-heptoxy benzoate)], [o-methyl-p-phenylene-bis-(p-heptoxy benzoate)], with benzene/cyclohexane, cyclokexanes, phenols, alcohols and aniline derivatives as sample compounds pairs. Some of the separations reveal positive or negative synergistic effect. This effect depends on the temperature, the mixing ratio and the linear velocity of the carrier gas.
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  • 37
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Enantiomeric separation ; Chiral derivatization ; Unusual secondary aromatic amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatographic and gas chromatographic methods were developed for the separation of unusual secondary aromatic amino acids. Amino acids containing 1,2,3,4-tetrahydroisoquinoline, 1,2,3,4-tetrahydronorharmane-1-carboxylic acid and 1,2,3,4-tetrahydro-3-carboxy-2-carboline moieties were synthetized in racemic or chiral forms. The high-performance liquid chromatography was carried out either on a teicoplanin-containing chiral stationary phase or on an achiral C18 column. In the latter case the diastereomers of the amino acids formed by precolumn derivatization with the chiral reagents 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate or 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide were separated. The gas chromatographic analyses were based on separation on a Chirasil-L-Val column.
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  • 38
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phases ; Calix[4]arene derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two new kinds of calix[4]arene derivatives, 5,11,17,23-tetra-tert-butyl-25,27-bis(isopropylcarbamoyl-methoxy)-26,28-diundecenyloxy calix[4]arene (C[4]A) and 25,27-dibutoxy-5,11,17,23-tetra-tert-butyl-26,28-diundecenyloxy calix[4]arene (C[4]B), have been synthesized for use as stationary phases in capillary gas chromatography with OV1701. These stationary phases demonstrate high column efficiencies, wide operating temperature ranges, good thermal stability and excellent selectivity for aromatic isomers, especially phenol compounds. Their inclusion properties are also discussed.
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  • 39
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    Chromatographia 47 (1998), S. 724-726 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Phthalate esters ; PVC ; Plastic toys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the analysis of 10 phthalate esters in plastic toys is described. The samples are soxhlet extracted in dichloromethane and phthalate esters in the extract are analysed by GC. Detection limits of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, bis(2-ethylhexyl) phthalate, di-n-octyl phathalate, di-n-nonyl phthalate, benzyl butyl phthalate and benzyl octyl phthalate were approximately 5 ppm. The detection limits of diisononyl phthalate and diisodecyl phthalate, which are mixtures of several isomers, were approximately 200ppm. Analysis of 17 plastic toys revealed that only PVC-toys contained phthalate esters. Bis(2-ethylhexyl) phthalate, diisononyl phthalate and diisodecyl phthalate in concentrations up to 40% were present in the PVC-toys.
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  • 40
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Correlation equation ; Alkylbenzenes ; Naphthalenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A detailed statistical analysis is presented for comparing the validity of selected literature-recommended equations with the unified retention index concept for calculating the retention indexes of alkylbenzenes on UCON LB 550X and naphthalenes on polydimethylsiloxane. Comparison with literature sources shows that the unified retention index provides the smallest residual error for a set of aromatic hydrocarbons.
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  • 41
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    Chromatographia 47 (1998), S. 579-586 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Ewe's cheese ; Triacylglycerols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Triacylglycerols from Idiazabal cheese fat were analysed by high-performance liquid chromatography (LC) with a non-linear gradient of acetone in acetonitrile and a light-scattering detector. Molecular species of triacylglycerols were predicted by a simple and a multiple linear regression analysis of logk of the LC peaks and molecular variables such as equivalent carbon number of the possible triacylglycerol, chain length and number of double bonds of each fatty acid of the triacylglycerol. Predicted results were confirmed by gas chromatographic analysis of the fatty acids in the LC peaks. The main triacylglycerols of Idiazabal cheese fat contained butyric acid, butyroyl-dipalmitin, butyroyl-myristoyl-palmitin and butyroyl-palmitoyl-olein. The most abundant triacylglycerols were those with even partition numbers of 36, 34 and 38.
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  • 42
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Organochlorine and organophosphorus pesticides ; Herbal medicine ; Essential oils ; Sulfuric acid treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid and new clean-up method utilizing sulfuric acid treatment is demonstrated to identify and quantify the level of organochlorine (OC) and organophosphorus (OP) pesticide residue concentrations in herbal essential oils by gas chromatography (GC). Essential oils fortified with pesticides, that are extracted from herbs by steam distillation are partitioned with 65% acetonitrile/water(v/v) and treated with sulfuric acid at different reaction times and sulfuric acid concentrations. Optimal conditions, to avoid interference from essential oils in gas chromatographic analysis, is 17% (v/v) of a mixed phase ratio of sulfuric acid to organic solvent (hexane/ethyl ether=9∶1, v/v) and a reaction time of 30s. The response of the flame ionization detector (FID) is linear for all pesticides determined. Recovery of pesticides from fortified herbs studied are in the range of 75% to 111% (RSD, 4% to 11%) for OC, and 72% to 116% (RSD, 2% to 11%) for OP. Although sulfuric acid treatment destroys carbamate and some organophosphorus pesticides, this method has efficiently reduced matrix interference and provides a rapid, economical clean-up method with excellent linear data having low coefficients of variation for the GC analyses of BHC isomers, DDD, DDE, DDT, chlorothalonil, chloropyrifos, tetradifon, fenitrothion, malathion, and parathion in matrices of herbal essential oils.
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  • 43
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Alkenes ; Epoxides ; Retention index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention indices or five 1-alkenes, seven branched alkenes and five cycloalkenes and the corresponding epoxides were determined at two temperatures on a fused-silica capillary column coated with cyanopropyl methyl siloxane to interpret their chromatographic behaviour. The standard deviation was 0.2 index units.
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  • 44
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phases ; β-Cyclodextrin derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Five β-cyclodextrin derivatives, heptakis[2,6-di-O-pentyl-3-O-(4-nitrobenzyl)-β-CD (CD-I), heptakis [2,6-di-O-pentyl-3-O-(5-hexenyl)]-β-CD (CD-II), heptakis-(2, 6-di-O-cinnamyl-3-O-methyl)-β-CD (CD-III), heptakis-(2, 6-di-O-cinnamyl-3-O-acetyl)-β-CD (CD-IV) and heptakis(2, 6-di-O-cinnamyl-3-O-trifluoroacetyl)-β-CD (CD-V), were synthesized and coated on fused-silica capillary coluns. Their chromatographic characteristics were tested and compared with heptakis (2,3,6-tri-O-pentyl)-β-CD (CD-VI) and heptakis (2,6-di-O-pentyl-3-O-trifluoroacetyl)-β-CD (CD-VII). It was found that the size, polarity, and aromatic property of the substituted group at the 3-position of heptakis (2,6-di-O-pentyl)-β-cyclodextrins greatly influenced their chromatographic properties and separation ability. The introduction of aromatic group or a group containing a double-bond may bring π-π interactions between the host and guest molecules, and therefore increased the separation ability of the β-CDs for substituted benzene isomers. Introduction of cinnamyl groups in to the 2,6-3-position of β-CD has a significant effect on the chromatographic properties of the stationary phases(CD-III-CD-V).
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  • 45
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    Chromatographia 47 (1998), S. 570-574 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Compressibility correction factor ; Specific retention volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The exact definition of the compressibility correction factor,j, has been extensively discussed in recent literature. In this work, it is shown that this compressibility correction factor has several different interpretations; however, the simplest and most useful meaning involves a correction from the experimentally accessible pressure at the outlet of a column to the average pressure in the column. Also, an unconventional definition of the retention volume of a solute in terms of the sample size and the equilibrium concentration of the solute in the mobile phase is presented. This retention volume definition is presented as an alternative to the common definition ofV R as the volume of carrier gas which passes through the column in a period of time called the retention time. In this discussion, it is emphasized that the temeprature dependence of the specific retention volume is determined by the thermodynamics of the phase distribution process for the solute and not by an equation-of-state for the carrier gas. Finally, the conventional correction of the specific retention volume by a factor of 273/T c can be used to correct a volume of carrier gas to a pseudo-standard state of 273 K and the average pressure in the column; however, this corrected specific retention volume has no relation to the specific retention volume that would be experimentally obtained at this standard state temperature and pressure. compressibility correction factor, and specific retention volume, were examined with regard to the physical interpretation, exact definition and appropriate standard states to be applied to these commonly reported chromatographic parameters. Such arcane discussions are beneficial to the health of science but may lead to confusion among potential and practicing chromatographers. In order to prevent or at least help ameliorate this problem, the following discussion presents a somewhat unorthodox interpretation of the questioned terms along with a pseudo-physical explanation of the so-called retention volume which is ubiquitous throughout the chromatographic literature.
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  • 46
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Solid-phase microextraction ; Local anaesthetic lidocaine ; Optimisation of extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Solid-phase microextraction (SPME) has been combined with gas chromatography (GC) and liquid chromatography (LC) for the determination of lidocaine in human urine. A polydimethylsiloxane (PDMS) coated fibre was directly immersed into buffered urine. Extraction conditions such as time, pH, ionic strength, temperature, and agitation were optimised. The extracted lidocaine was thermally desorbed in a split/splitless injector for analysis with a GC-FID system or desorbed with liquid in a specially designed SPME-LC interface for analysis with an LC-UV system. After optimisation the method developed was evaluated and validated. Extraction yields of 22% were obtained in about 45 min. The reproducibility of the method is 〈5% (relative standard deviation). For five-times diluted urine, linear ranges were found from 5–1000 and 25–1000 ng·mL−1 for SPME-GC and SPME-LC, with detection limits of 5 ng·mL−1 for SPME-GC and 25 ng·mL−1 for SPME-LC. SPME can be used as a simple sample pretreatment method for the determination of lidocaine in urine by GC and LC.
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  • 47
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    Chromatographia 47 (1998), S. 685-688 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; Safrole ; Asarum species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The development of a headspace GC method (HS-GC) to determine the safrole content in differentAsarum species from China and Europe, using eugenol as internal standard, is presented in this paper. The best results could be achieved by thermostating the samples at 100°C for 30.0 min, adding 10 μL of water to each sample. Optimum pressurisation and injection time showed to be 3.0 min and 12 s, respectively. GC separation was performed on an SE-54 column. The HS-GC results for safrole were in good agreement with those obtained by direct GC analysis of the dichloromethane (DCM) plant extracts. The investigated Asarum samples showed great deviations concerning the safrole content even within the sameAsarum species, e.g.Asarum himalaicum from Sichuan contained 0.0051% of this compound, the same species from the province of Hebei 0.53%.
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  • 48
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Pyrolysis GC ; Residual polystyrene ; Streptomycin ; Vitamin B1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Residual synthetic adsorbent, cross-linked polystyrene, used in drug purification has been analyzed quantitatively by Curie-point pyrolysis gas chromatography. The peaks of intact polystyrene adsorbent in the pyrogram were used as key peaks for quantitative measurement of residues of the adsorbent in vitamin B1 and streptomycin sulfate. It was shown that them-ethylstyrene orp-ethylstyrene peaks in the pyrolyzates were suitable for determination of polystyrene adsorbent content. The levels of residual adsorbent in the drugs were found to be 〈0.1 %, the value stipulated by the International Conference on Harmonization (ICH). In quantitative evaluation of an adsorbent content of 0.1 % the precision was 3.6 % and 2.7 % for vitamin B1 and streptomycin sulfate, respectively.
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  • 49
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid-phase microextraction ; Headspace sampling ; Cyanide in blood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Cyanide can be extracted from whole blood samples by headspace solid-phase microextraction (SPME) with a Carbowax/divinylbenzene-coated fiber. During heating a vial of a whole blood sample containing cyanide and acetonitrile as internal standard (IS) at 50°C in the presence of Na2SO4, a Carbowax/divinylbenzene-coated SPME fiber was exposed in the headspace of the vial for 45 min to allow adsorption of cyanide and IS. The fiber needle was then injected into a capillary gas chromatography (GC) instrument equipped with nitrogen-phosphorus detection. The headspace SPME-GC with a Supel-Q PLOT fused silica capillary column gave large peaks for cyanide and IS; almost no interfering peaks appeared. Recoveries of cyanide dnd IS from human whole blood were 3.02–4.06% and 0.21%, respectively. The calibration curve for cyanide added to human blood showed excellent linearity in the range of 0.04–4.0 μg mL−1; the detection limit was about 0.02 μg mL−1. The coefficients of intra-day and inter-day variation were not greater than 7.1 and 9.2%. Good correlation (r 2=0.999) was found between the present SPME-GC method and the conventional microdiffusion colorimetric method. Data on determination of cyanide in rat blood after intraperitoneal administration are also presented.
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  • 50
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    Chromatographia 47 (1998), S. 63-71 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid foods ; Food packaging materials ; Vinylchloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The interaction of vinylchloride (VC) with liquid foods, such as water, olive oil and honey, was studied using the relatively new technique of Reversed-Flow Gas Chromatography (RFGC). The RFGC method permits the calculation of the VC diffusion coefficient in the liquid phase (water, oil and honey) and the determination of the partition coefficient of VC between the liquid and the carrier gas, as well as the determination of the Henry's constant of VC in the liquid food. From the variation of the above parameters with temperature, thermodynamic parameters (free and excess free energies, enthalpies, entropies and activity coefficients) were calculated for the adsorption of VC by liquid foods. These are discussed in comparison with the same parameters calculated from empirical equations or determined experimentally by other techniques.
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  • 51
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    Journal of biomedical science 5 (1998), S. 415-420 
    ISSN: 1423-0127
    Keywords: Isoprostanes ; Oxidative stress ; Lipid peroxidation ; Gas chromatography ; Mass spectrometry ; Human disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The development of a specific, reliable and noninvasive method for measuring oxidative stress in humans is essential for establishing the role of free radicals in human diseases. Currently, accurate techniques to assess oxidant injury in vivo are extremely limited although a number of approaches are being investigated. Of these, the measurement of specific products of nonenzymatic lipid peroxidation, the F2-isoprostanes (F2-IsoPs), appears to be a more accurate marker of oxidative stress in vivo in humans than other available methods. The purpose of this brief review is to acquaint the reader with the IsoPs from a biochemical perspective and to provide information regarding the utility of quantifying these compounds as indicators of oxidant stress.
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  • 52
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    Space science reviews 84 (1998), S. 199-206 
    ISSN: 1572-9672
    Keywords: Nuclear reactions ; Nucleosynthesis ; Abundances ; Stars:Evolution ; Interior ; Rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We first recall the observational and theoretical facts that constitute the so-called 3He problem. We then review the chemical anomalies that could be related to the destruction of 3He in red giants stars. We show how a simple consistent mechanism can lead to the destruction of 3He in low mass stars and simultaneously account for the low 12C/13C ratios and low lithium abundances observed in giant stars of different populations. This process should both naturally account for the recent measurements of 3He/H in galactic HII regions and allow for high values of 3He observed in some planetary nebulae. We propose a simple statistical estimation of the fraction of stars that may be affected by this process.
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  • 53
    ISSN: 1612-1112
    Keywords: Gas chromatography ; SPME ; Soil and groundwater samples ; Chlorobenzenes ; Thermal desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A complex method was developed for the determination of chlorobenzenes in soil and groundwater samples. Samples were taken at two sites in Baranya county, where a mixture of chlorobenzene waste was deposited, causing severe contamination in the environment. Clean-up of these sites demands modern and reliable analytical methods. Several sample preparation techniques were used, such as solid phase microextraction (SPME), supercritical fluid extraction (SFE), and a recently developed thermal desorption method. The applicability of various sample preparation methods was compared by measuring recovery percentages, relative standard deviations and by investigating the matrix dependency of these values. Gas chromatography was used for quantitative determination of chlorobenzenes, using MS, IR, FID and ECD detection techniques. Detection levels were as low as 1 ppt in water, and 10 ppt in soil samples. Chlorobenzene concentration was in the range 1 ppt-1 ppm in water and 100 ppb-100 ppm in soil samples. Identification and calibration of these compounds were performed by quantitative standards. This complex analytical method can be used for rapid and precise quantitative and qualitative determination of chlorobenzenes.
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  • 54
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    Chromatographia 48 (1998), S. 86-88 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid phase extraction ; Methoxime-silyl derivate ; Urinary steroids ; Women with effluvium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Urinary steroid metabolites were measured by capillary gas chromatography in 25 women (aged 33.3±12.0 years) with effluvium and 16 control healthy laboratory workers women (aged 34.6±8.4 years). There was significant elevation in the level of a number of steroids and steroid metabolites. The elevation of most steroid metabolites refers to the increased steroid secretion of the adrenal and the high cortisol metabolites levels may be do to stress in some of the patients with effluvium.
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  • 55
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chiral separation ; Alcohols ; Diols ; Trimethylsilylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic chiral separation of several chiral 2-and 3-alkanols and diols was studied both in their free hydroxyl and in their trimethylsilyl ether forms. First, the derivatization procedure was verified through the identification of the trimethylsilyl ethers formed on the basis of their mass spectra and optimized to obtain quantitative reaction. The optimized procedure was applied to the trimethylsilylation of racemic mixtures of various hydroxyl compounds. The silylation was found to be highly effective in the improvement of the separation of the individual enantiomers. The major advantages of the derivatization process can be summarized as: (i) excellent baseline separation of the enantiomers of the silyl ethers was achieved in contrast to the parent OH-containing compounds, (ii) the sensitivity of detection highly increased, (iii) the separations do not show any significant concentration dependence and finally (iv) the analysis time needed decreased significantly.
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  • 56
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Heats of vaporization ; Gibbs free energies ; Kováts retention indices ; Alkylbenzenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In our paper we propose a new method for the determination of heats of vaporization (ΔH vap(i)) and the Gibbs free energies of vaporization (Δμp(i)) for individually selected alkylbenzenes, chromatographed on stationary phases of low and medium polarity. The method is based on a new thermodynamic description of the Kováts retention index (I (i)) making use of Trouton's rule. In fact, we attribute physical significance to two empirical relationships, well known from the literature. We can describe thermodynamically the magnitude ofI (i) using two relations, each of them potentially useful for further determination of δH vap(i) and Δμp(i). A comparison was made of the results obtained with the use of our new approach and of those already existing in the literature attained in a completely different way. The comparison suggests that the calculated δH vap(i) and Δμp(i) values are thermodynamically acceptable and hence correct, and the data suit into the series of similar values determined on stationary phases of different polarity.
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  • 57
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    Chromatographia 48 (1998), S. 156-157 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gel permeation chromatography ; Organophosphorous pesticides ; Plant samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The work presents a GC method for the determination of six organophosphorous pesticide residues in cabbage. Chopped cabbage was blended with acetone, then extracted with the mixture of n-hexane:methylene chloride (1:1). The extract was purified on a GPC column packed with BioBeads SX-3 gel. The pesticides were eluted with the mixture of methylene chloride:cyclohexane (1:1) at the flow rate of 0.5 mL min−1. After concentrating the extract was analysed by GC. Nearly 100 samples of cabbage were analysed; trace residues of dimethoate (about 0.05 ppm) were found in 10 samples. The average recoveries of the pesticides were above 80% with a relative standard deviation mostly less than 10%.
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  • 58
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    Chromatographia 48 (1998), S. 163-165 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid-phase extraction ; Urinary steroids ; Terbutaline treatment ; Asthmatic children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Steroid metabolites have been measured by capillary gas chromatography in the urine of 38 children aged 3–6 years. The children comprised three groups: those with asthma being treated with Terbutaline (13), children with asthma but not undergoing treatment (17), and control children in hospital but free from endocrine diseases (8). There were significant (P〈0.05) differences between the amounts of steroids excreted by the different groups of children. Terbutaline therapy led to elevated levels of tetrahydrocortisone, androstenediol, 11-ketopregnanetriol and a reduced ratio of androgen to cortisol metabolites compared with those for untreated asthmatic children. We assume that Terbutaline does not have a steroid-like mechanism of action but acts by modification of the activity of several adrenocortical enzymes. We suggest a hypothesis whereby the antiasthmatic effect of Terbutaline could not only be a connected with its well-known mechanism of action, but it might be explained as a result of the modification of the production of certain glucocorticoids and androgen hormones.
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  • 59
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    Chromatographia 48 (1998), S. 758-762 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Butyric acid ; Milk fat content ; Mixed fats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Quantitation of the milk fat content in mixed fats is of interest in food analysis. It can be achieved by calculation from the butyric acid (C4) content in the mixed fat and a mean C4 content for pure milk fats. Alternatively, instead of applying a C4 mean value, the C4 content in the actual milk fat can be used if this reference sample is available. A recently improved analytical method based on gas chromatography of butyric acid methyl ester using an internal standard has been applied to determine the milk fat content in mixtures with beef tallow, lard, soybean oil, olive oil, sunflower oil, palm kernel oil and palm oil ranging from 1 to 90% milk fat content. Within the whole range of mixtures, mean absolute deviations between the determined and the actual milk fat content were below 0.5% and the maximum absolute deviation was not more than 1.0% when using the reference sample. The overall mean absolute deviation was 0.04% for milk fat contents of 1 to 10% and 0.28% for milk fat contents of 10 to 90%.
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  • 60
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    Chromatographia 48 (1998), S. 728-738 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phases ; Prototypical phases ; Retention model ; Retention value ; Dipolarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Stationary phases are characterised in a multilinear retention model by retention data of a set of selected prototypical substances. Prototypical stationary phases confirm the application of prototypical substances in the retention model. For comparison, 27 stationary phases are characterized with solute descriptors of the solvation model. New adjusted substance factors are calculated for 33 selected compounds for a new characterization of GC stationary phases in the extended retention model with retention values, calculated from retention indices and b-values of the n-alkane equation. Substance dipolarityD N-factors are separated from πN, the adjusted dipolarity-polarisability. New substance factors give satisfying correlation results and new explanatory factors as phase descriptors for 27 stationary phases.
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  • 61
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid-phase extraction ; Rapeseed oil ; Sterols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary gas chromatographic method is described for the determination of major plant sterols and cholesterol in edible oils and fats. In the sample preparation procedure reversed-phase, solid-phase extraction with C18 adsorbent was used to extract the unsaponifiable matter and for sample cleanup after saponification. Sterols were quantitated as their trimethylsilylether derivatives using an internal standard method (betulin). The method was validated by recovery tests and analysis of two reference materials representing vegetable oil mixture and milk fat matrices. Average recoveries of spiked cholesterol and cholesterol acetate in rapeseed oil were 103±4% (n=12) and 101±3% (n=10), respectively. The sterol values determined in the reference materials were found to be in a good agreement with their given certified or indicative values. Applied to edible oils and fats, plant sterols and cholesterol at levels〉20 mg kg−1 could be accuratively quantitated.
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  • 62
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid phase extraction ; Brazilian sugar cane spirit ; Lower fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method for the analysis of seventeen acids in a water/ethanol matrix is described. The diluted samples were first concentrated by solid phase extraction. Nonanoic acid was the internal standard. A good separation profile was obtained for all compounds, including the isomers: n and iso-butyric acids, n and isovaleric acids and n and iso-caproic acids. The method is fast, sensitive (20–30 μg L−1) and has a good reproducibility (4–7 %). The recovery was in the range of 94%–116% for the medium chain acids (C7-C16). This method allowed the identification of fourteen acids in caninhas and other spirits. The total acid content and the profile of the exportation type caninhas are similar to the ones obtained for several international beverages.
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  • 63
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Metal complexes ; Chemically bonded phases ; Thermodynamic parameters ; Specific interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Results are presented of studies of packings containing copper (II) acetylacetonate (acac), hexafluoroacetylacetonate (hfac), and chloride, chemically bonded via β-dik-etonate groups. The retention parameters retention factor (k) specific retention volume (V g), and molecular retention index (M e) were measured and used to calculate the thermodynamic parameters free energy of adsorption (ΔG a) heat of adsorption (−ΔH a), and entropy of adsorption (ΔS a). These parameters enable, characterization of specific interactions between aromatic and cyclic hydrocarbons, ethers and thioethers and metal complexes chemically bonded, to a silica surface.
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  • 64
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Atomic emission and MS detection ; Solid-phase extraction ; Aqueous samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A procedure is described for the (non-target) screening of hetero-atom-containing compounds in tap and waste water by correlating data obtained by gas chromatography (GC) using atomic emission (AED) and mass selective (MS) detection. Solid-phase extraction (SPE) was coupled on-line to both GC systems to enable the determination of microcontaminants at the 0.02–1 μg L−1 level in 7–50 mL of aqueous sample. The screening was limited to compounds present in at least one heteroatom-selective GC-AED trace above a predetermined concentration level. These compounds were identified by their partial formulae (AED) and the corresponding mass spectra, which were obtained from the GC-MS chromatogram via the retention index concept. The potential of the approach was demonstrated by the identification of target compounds as well as all unknowns present in tap and waste water above the predetermined threshold of 0.05 μg L−1 (tap water) or 0.5 μg L−1 (waste water).
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  • 65
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid crystal stationary phase ; Packed columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation ofm-, p-, o- xylenes andm-, p- ethyltoluenes was studied on a packed column with 2,5% of 4-[(4-chlorobenzyl)oxy]-4′-cyanoazobenzene (CBOCA) on Chromosorb W HP 100–120 mesh. The synthesis and study of the mesomorphic behaviour of CBOCA are presented. Temperature range for the separation ofm-, p-, o- xylenes (in this order of elution) is 125–85°C, at cooling. The best separation was achieved at about 90°C. The separation temperature domain ofm-ethyltoluene fromp- ethyltoluene is 160–85°C.
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  • 66
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Calix[4]arene-tetramethyldisiloxane stationary phases ; Geometric and positional isomer separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Poly(p-tert-butyldimethoxydipropyloxycalix[4]arene-tetramethyldisiloxane) (TBCX-TMDS) and poly(dimethoxydipropyloxycalix[4]arene-tetramethyl-disiloxane) (CX-TMDS), have been prepared and used as stationary phases for isothermal capillary gas chromatographic separations of positional isomers. Retention factors and separation factors for the isomers were measured. The isomers investigated were well-resolved on the two phases. Retention of all the solutes investigated is greater on TBCX-TMDS than on CX-TMDS, probably because of extra dispersive interactions of the solutes with thetert-butyl groups of the phase. Separation factors for closely-eluting isomer pairs are similar on the two phases. This seems to indicate either that the solutes are retained by non-inclusion processes or that if the isomer molecules do enter the cavity of the calixarene, i.e. the solute is retained by inclusion, thetert-butyl groups do not play a role in discriminating between the isomers.
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  • 67
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Water analysis ; Derivatization with bromine ; Aromatic amines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For improved determination of aromatic amines by gas chromatography and detection with an electron capture detector (GC-ECD) a derivatization method based on the bromination of the aromatic ring in an acetic acid medium was developed. In general, all free ortho and para-positions relative to the amino group undergo electrophilic substitution. Separation of at least 30 compounds in a single chromatographic run in 30 min is possible. With this method, 56 aromatic amines were studied and only in 6 cases were no derivatives obtained. Quantitation limits determined from calibration data are 1.2–40 μg L−1 for a 100 mL sample and an injection volume of 1 μL. Previous experiments suggest that both sample and injection volume may be increased to lower the quantitation limit.
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  • 68
    ISSN: 1612-1112
    Keywords: Gas chromatography ; UV-Vis detection ; Gas phase absorption spectrometry ; Alcohols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This article describes a theoretical/practical study of the parameters which affect the chromatograms obtained when using a molecular diode-array spectrometer as the detector in gas chromatography. The objective is to offer some rules which permit the identification of the optimum signal/noise relation. To achieve this, we study the effect of the different parameters which affect the noise and how to reduce their impact, as well as alternatives for increasing the signal. All the options tested can be applied by correctly programming the spectrometer with BASIC programs, within reach of any use who has even a small understanding of programming. Finally, we consider the effect that the selection of the acquisition conditions may have on the chromatographic resolution. All the studies are carried out using a mixture of alcohols and phenols.
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  • 69
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    Chromatographia 48 (1998), S. 817-822 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Crown ether capped cyclodextrin ; Chiral separations ; Isomer separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The solution of a new synthesized compound, mono-6-(1'-benzo-aza-15-crown-5)-2, 3, 6- permethyl-β-cyclodextrin, in the moderately polar polysiloxane OV-1701 was coated onto fused silica capillary column. The chromatographic characteristics including column efficiency, polarity and selectivity were studied. Excellent selectivity for the separation of enantiomers and positional isomers was obtained. The results show that the combined effect between the special caves of β-cyclodextrin and crown ether plays a significant role in the separation.
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  • 70
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    Chromatographia 48 (1998), S. 299-304 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; Ethoxylated alcohols ; Ethoxylated alkylamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Headspace-gas chromatography was used to determine the contents of toxic 1,4-dioxane, ethylene oxide and ethylene glycol in ethoxylated alcohols and alkylamines, and in commercial cosmetics and washing products. A Permaphase PEG capillary column was used for the determination of 1,4-dioxane and ethylene oxide and a DB-17 column for ethylene glycol determination. Dimethylformamide was used as the solvent in the determination of 1,4-dioxane and ethylene oxide, and undecanol in the case of ethylene glycol. The detection limits for ethylene oxide, 1,4-dioxane and ethylene glycol are 1,2 and 10 μg·g−1, respectively.
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  • 71
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid phase extraction ; Polychlorobiphenyls ; Clorinated pesticides ; Organochlorine separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography of polychlorinated biphenyls and chlorinated pesticides in water samples is carried out after adsorption from a 25–500 mL sample, on a cartridge containing 100 mg aminopropyl-bonded porous silica. The clean-up step in which the PCBs and chlorinated pesticides are separated in different eluates is achieved by passing 25 mL of 40% aqueous methanol through the NH2 Sep-Pak cartridge. The PCBs are desorbed with 500 μL ethylacetate, which is concentrated and analysis by GC-ECD. The average recovery, at 1 ppb is 〉97% with a standard deviation 〈2. The limits of detection are 0.1 ng μL−1 and 5 pg μL−1 respectively for Cl3-PCB and Cl8-PCB congeners. In the separation of PCBs from the chlorinated pesticides tested in this work, only the Aldrin is adsorbed for 60% with the PCBs by the NH2 Sep-Pak cartridge. The method described is rapid, simple and reproducible.
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  • 72
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    Chromatographia 48 (1998), S. 443-449 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas chromatography-mass spectrometry ; Triethanolamine in air
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Low amounts of triethanolamine, collected in ORBO 53 tubes during air sampling, required the development of a very sensitive method for determination. After desorption and silylation reaction with trimethylsilyl imidazole/trimethyl chlorosilane, the derivative was analyzed by gas chromatography-mass spectrometry on an Ultra 2 silica capillary column in single ion monitoring mode (retention time: about 6 min). The method has a detection limit of 1–2 pg with a desorption efficiency of about 81%. Linearity of response was ascertained in the ranges 10–100 ng and 100–1000 ng. Short-term method validation was carried out by intra- and inter-day assays on three amounts for each reference calibration curve. All results satisfied the pre-defined acceptance criteria. In general, the whole procedure was easily performed and was appropriate for our needs. Breakthrough volume was appropriate for our needs. Breakthrough volume was determined on authentic samples and was about 40–60 L, using a flow rate of 1 L·min−1. The amounts of triethanolamine found in the samples ranged from 150 to 250 ng (about 2.5–4.2 μg·m−3).
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  • 73
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Soil samples ; Microwave-assisted solvent extraction ; Nitrogen detection ; Triazine herbicides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Recent work demonstrated that the combination of microwave assisted solvent extraction (MASE) and capillary gas chromatography with selective nitrogen detection (GC-NPD) is a viable approach for the efficient determination of triazine herbicides in soils. However, for soils with a high organic matter content or the injection of more concentrated extracts to obtain lower LOD's the performance of gas chromatographic analysis of uncleaned extracts is hampered. This results in both a decrease of the chromatographic response of analytes and a decrease in the life time of the column due to coextracted matrix substances. The effect of various types of soils on the chromatographic analysis of triazine herbicides was studied. It appeared that for the investigated samples with an organic matter content below 5% processing of uncleaned extracts is possible. Samples with a higher organic matter content required a cleanup step. A rapid procedure on 100 mg silica cartridges has been developed using solvents compatible with the MASE extracts and the instrumental analysis. Beside the testing with different standard soils, about 120 samples of an ongoing monitoring program involving three different types of soil (organic matter content: 3–37%) were analysed. The selected compounds atrazine, desethylatrazine, desisopropyl-atrazine and simazine could be assayed in the various soil types to a level of at least 2 μg kg−1. For soil samples with a high organic matter content (〉5%), the rapid cleanup procedure allowed the trace analysis of the triazines and considerably increased the life time of the capillary column. Recoveries at levels from 2 to 50 μg kg−1 ranged from 70 to 100% with RSDs ranging from 5.1 to 9.5%. Confirmation of positive samples was carried out by gas chromatography mass spectrometry.
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  • 74
    ISSN: 1612-1112
    Keywords: Gas chromatography ; UV-Vis detection ; Gas phase absorption spectrometry ; Derivatization ; Alcohols and phenols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is proposed for the determination of alcohols and phenols based on their derivatization to benzoates and gas chromatography-gas phase molecular absorption spectrometry. All parameters affecting the derivatization reaction, such as the solvent, basic medium, benzoyl chloride and stirring time, were optimized. Chromatographic and instrumental conditions were also studied. Finally, a calibration study was performed and the results were compared to that obtained by the direct determination of the compounds.
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  • 75
    ISSN: 1612-1112
    Keywords: Gas chromatography ; On-line SPE-GC-MS ; Beverage carton packages ; Contaminant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An unknown migration contaminant was found in a number of mineral water samples contained in beverage carton packages. This compound was isolated by a fully automatic solid phase extraction system and identified by means of GC-MS as 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) [126-86-3], which is used as a surfactant in water-based printing inks and migrates during the production of the beverage carton material into the inner polyethylene film and subsequently into the product. The determined concentrations of TMDD ranged up to more than 50 μg L−1.
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  • 76
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid-phase extraction ; Graphitized carbon black ; Volatile organic compounds ; Workplace air
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A fast, simple, and reliable method is presented for the determination of atmospheric semi-volatile organic pollutants at μg m−3 levels. The method has been used to monitor potentially carcinogenic toxic compounds to which workers are exposed in workplaces, and to measure the same compounds in outdoor air.
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  • 77
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Cholesterol oxides ; Cholesterol oxidation products (COPs) ; Meat products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method of extraction, purification and gas chromatographic analysis of five cholesterol oxidation products (COPs) (7β-hydroxycholesterol, 5α, 6α-epoxycholesterol, 25-hydroxycholesterol, 7-ketocholesterol and cholestane-3β, 5α, 6β-triol) has been developed. The method is aimed at the determination of COPs in meat and meat products, in particular dry sausages, where large differences in the content of cholesterol and its oxidation derivatives may occur. Linearity of response of trimethylsilyl ethers was defined. The minimum concentration tested was 2.5 μg g−1 in the injected solution. The main feature of the present work is the addition of a purification step of unsaponifiables by SPE on silica cartridges. Extraction recoveries of COP standard mixtures, performed with or without the SPE step, are evaluated. The introduction of the clean-up step results in high purity samples without further losses in the entire process.
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  • 78
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Programmed-temperature vaporization (PTV) ; Large-volume injection ; Direct water injection ; Triazines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The potential of large-volume PTV injection was studied for the analysis of triazine herbicides in water samples. Direct water injection and in-vial extraction were described and compared. Detection limits were between 0.01–0.02 μg L−1 and relative standard deviations were 〈9%. Both methods are suitable for the analysis of triazines at ppt-level, although in-vial extraction is favourable for water samples with relatively large amounts of matrix components.
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  • 79
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    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 205 (1997), S. 415-418 
    ISSN: 1431-4630
    Keywords: Key words Human adipose tissue ; Cancer ; Conjugated linoleic acid ; CLA ; Gas chromatography ; Infrared spectroscopy ; Mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The methyl ester and 4,4-dimethyloxazoline (DMOX) derivatives of the geometric isomers cis9,trans11- and trans9,trans11-octadecadienoic acid and the two minor isomers trans9,cis11- and cis9,cis11-octadecadienoic acid were found in human adipose tissue, by using gas chromatography–direct deposition–Fourier transform infrared spectroscopy (GC–DD–FTIR) and gas chromatography–electron ionization mass spectrometry (GC–EIMS).
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  • 80
    ISSN: 1431-4630
    Keywords: Key words Authentication ; Spirits ; Natural hydrogen and carbon isotope ratios ; Gas chromatography ; Linear discriminant analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Gas chromatography and the determination of natural isotope ratios are powerful analytical methods which can be used to check the authenticity of alcoholic beverages and to detect any adulteration. To check the origin and the authenticity of commercial fruit spirits, whiskies, etc., 197 samples were analysed by gas chromatography, 2H-NMR and 13C isotope mass spectrometry. The discrimination between different varieties was demonstrated by bivariate and multivariate discriminant analysis using different concentrations of volatile compounds such as methanol, butan-1-ol, 2- and 3-methyl-butanol, benzaldehyde and hexanol as well as isotopic data like (D/H)I, (D/H)II and 13C/12C isotopomers of ethanol. The results show that by using multivariate discriminant analysis it is possible to distinguish not only between different groups of spirits, e.g. those made of stone-fruit, malaceous fruit, grain and corn, but also between individual varieties, such as cherry, plum, mirabelle and apple. If the detection of highly rectified ethyl alcohol of agricultural origin and the identification of its raw materials are required, then natural isotope ratios are the only discriminant analytical parameters available.
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  • 81
    ISSN: 1432-072X
    Keywords: Key words Paracoccus denitrificans ; Paracoccus ; versutus ; CS2 oxidation ; CS2 oxygenase ; Autotrophy ; 16S rRNA phylogeny ; Plasmids ; Megaplasmids ; Murein ; Gas chromatography ; SDS-PAGE profiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three distinct strains (KL1, KS1, and KS2) of facultatively chemolitho-autotrophic bacteria able to use carbon disulfide or carbonyl sulfide as sole energy substrates were identified as novel strains of Paracoccus denitrificans. Evidence for their identity as biovars of P. denitrificans and as close relatives of Paracoccus versutus is based on their DNA composition, total sequencing of the genes for their 16S rRNA, muropeptide profiles, amino acid composition of peptidoglycan, kinetics of murein degradation by lysozyme, possession of large plasmids (91–98 kb) and megaplasmids (〉 450 kb), and plasmid transfer between the strains and with P. denitrificans and P. versutus. No functions have been identified for the 91- to 98-kb plasmids of strains KL1 and KS2, but curing strain KL1 of its plasmid did not affect growth on carbon disulfide, thiosulfate or succinate. Emendation of the formal description of Paracoccus denitrificans is presented. Autotrophic growth on carbon disulfide and thiosulfate was confirmed by 14CO2 fixation. Evidence is presented for initiation of carbon disulfide oxidation by an NADH-dependent oxygenase. Cell-free extracts catalyzed (1) NADH-stimulated uptake of oxygen in the presence of carbon disulfide, and (2) carbon-disulfide-stimulated oxidation of NADH. The activity was not sedimented at 50,000 ×g. Intermediates in aerobic carbon disulfide metabolism were shown by GC and GC/MS to include carbonyl sulfide and hydrogen sulfide, but anaerobic production of COS and H2S from carbon disulfide did not occur. SDS-PAGE of cell-free extracts showed polypeptides that were unique to growth on carbon disulfide, common to carbon disulfide and carbonyl sulfide, or found after growth on carbon disulfide, carbonyl sulfide or thiosulfate. The possible identity of these as proteins involved in sulfur compound metabolism is discussed.
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  • 82
    Electronic Resource
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    Springer
    Chromatographia 44 (1997), S. 91-96 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid chromatography ; Racemic sulphoxides ; Enantiomer separation ; Preparative LC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The enantiomeric resolution of seven racemic sulphoxides on chiral stationary phases has been investigated by gas and liquid chromatography. In gas chromatography the separations were performed on octakis-(2,6-di-O-pentyl-3-O-butyryl)-γ-cyclodextrin (FS Lipodex-E) and heptakis-(2,6-di-O-methyl-3-O-pentyl)-β-cyclodextrin (DMP-β-CD). Both stationary phases were suitable for separation of the enantiomers of the sulphoxides. With one exception for each series all racemetes could be resolved on both stationary phases; FS Lipodex-E was more enantioselective than DMP-β-CD, whereas the latter seemed more generally applicable. Liquid chromatographic separations with Chiralcel-OB as stationary phase were significantly improved by optimization of mobile phase composition and temperature. Resolution factors up to Rs=6 were achieved indicating that the improved separations could now be easily used for preparative purposes.
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  • 83
    Electronic Resource
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    Springer
    Chromatographia 44 (1997), S. 320-324 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Wine analysis ; Pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid method based on gas chromatography which determines parathion-methyl, fenitrothion, chlorpyrifos, dichlofluanid, vinclozolin, chlozolinate, procymidone and iprodione is described. It involves quantitative extraction with n-hexane and determination by capillary gas chromatography using an electron capture detector. Pesticides were satisfactorily separated in 15 min with a phenylmethylsilicone fused-silica capillary column under isothermal conditions. Quantitation was carried out using dieldrin as internal standard. The method seems appropriate for oenological laboratory work because of its simplicity and rapidity. It was successfully used to identify and quantify pesticides studied in musts and wines.
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  • 84
    Electronic Resource
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    Chromatographia 44 (1997), S. 97-99 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; FAMEs ; Rapeseed-mustard ; Half-seeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An efficient and economical GC method for rapid determination of FAMEs in rapeseed-mustard is described. The seeds were transmethylated with acetylchloride, using microwave heating and separation achieved on a 3 m column packed with a mixture of 2% SP-2300 and 3% SP-2310 on Chromosorb ‘W’. The method is compared with the conventional heating method and extended efficiently for half-seed analysis. The fatty acid composition of the FAMEs mixtures prepared by both methods was similar with highly significant correlation coefficients (P〈0.001).
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  • 85
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Trace volatile components ; Human breath
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified GC sampling system and its analytical use are described for the determination of volatile components of human breath or in ambient atmosphere with flame-ionization detection (FID). The difficulties of collection for low concentration samples were alleviated by using a very small trapping column packed with activated charcoal. The collected samples can be measured directly after thermal desorption onto the chromatographic column (packed with Porapak Q). The preconcentration recoveries for pentane, methanol, ethanol and acetone have been studied.
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  • 86
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Temazepam in plasma ; Pharmacokinetic studies ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive method was developed for the determination of temazepam in plasma using capillary gas chromatography. After the extraction into dichloromethane-pentane (1∶1), temazepam was quantitated as its O-trimethylsilyl derivative on a capillary column with a63Ni electron capture detector using prazepam as internal standard. The detector response was found to be linear in the concentration range 0.031 to 8 μg mL−1. The detection limit was about 3.5 ng mL−1. The intraday and inter-day coefficients of variation were below 9%. The method was used to determine the pharmacokinetic profile of temazepam in rats after intravenous administration.
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  • 87
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    Springer
    Chromatographia 44 (1997), S. 179-186 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention-boiling point correlation ; Trouton's rule ; Alkylbenzenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A thermodynamic interpretation of the empirical correlation between retention and boiling point for alkylbenzenes in stationary phases of low and medium polarity has been found. The transfer of molecules between the liquid and mobile phases was assumed to be similar to, although not identical with, vaporization of any given pure liquid and characterized using the Trouton's rule. The two equations developed relate relative retentions to solute boiling point and two systems constants under a given set of conditions. The first equation was found to give a better description since it involves fewer assumptions and approximations. Validity of the model was confirmed by agreement between theoretical and experimental values for equation constants although the agreement becomes poorer as the stationary phase polarity increases. The relationships discussed are applicable to all congeneric solutes of low polarity in stationary phases of medium polarity.
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  • 88
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    Chromatographia 44 (1997), S. 279-282 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention volumes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Through a straightforward mathematical derivation it is shown that the compressibility correction factor equals the ratio of gas pressure at the column outlet to the average pressure in the column, $$j = p_0 \sqrt p $$ . Therefore, by multiplying by this factor, the experimentally measured retention volumes can be recalculated to the average pressure in the column. Corrected retention volumes thus represent the volume of the mobile phase under real conditions of chromatography in the column. Appropriate definitions for corrected retention volumes and factorj are formulated.
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  • 89
    ISSN: 1612-1112
    Keywords: Solid-phase extraction ; Gas chromatography ; Ion trap tandem mass spectrometry ; Water samples ; Environmental analysis ; Pesticides ; Bromide ; Nitrite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary On-line solid-phase extraction-gas chromatographyion-trap tandem mass spectrometry (SPE-GC-MS/MS) has been used for the trace-level determination of polar and apolar pesticides. The SPE-GC interface, an Autoloop 2000, was operated at an injection temperature of 90°C which permitted the determination of thermolabile pesticides such as carbofuran and carbaryl. Rectilinear calibration curves were obtained for the analytes tested over a range of 0.1–500 ng L−1, using a sample volume of 10–100 mL for enrichment on an SPE cartridge packed with styrene-divinylbenzene copolymer. The detection limits for the pesticides were in the 0.01–4 ng L−1 range. For a number of pesticides acceptable tandem mass spectra were obtained at levels as low as 0.1 ng L−1 level in real-life water samples. As a demonstration of the applicability of this technique for inorganic anions, bromide and nitrite were converted into 4-bromoacetanilide and 2-phenylphenol, respectively. The reaction products were pooled and subjected to simultaneous analysis by the present method using full-scan mass spectrometric detection. The detection limits were 0.3 and 2 ng L−1, respectively.
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  • 90
    Electronic Resource
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    Chromatographia 44 (1997), S. 386-392 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; HBr-treated capillary column ; Methylmercury chloride ; Halide exchange ; ECD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography with electron capture detection (GC-ECD) for the analysis of methylmercury choloride (MMC) using a packed column and a capillary column has been investigated. The columns were 2% silicone OV-227 Uniport HP glass column and a DB-17 capillary column, each pretreated by about ten injections of HBr-methanol solution. MMC was separated as a sharp peak by the HBr-teated column and determined directly by ECD without derivatisation. The mass spectrum of MMC indicated that halide exchange from chloride to bromide proceeded during separation. The minimum detectable concentrations were approximately 5 ng mL−1 on the packed column, and 2 ng mL−1 on the capillary. Calibration curves showed good linearity between 5–200 ng mL−1 for the packed column, and between 2–200 ng mL−1 for the capillary. Relative standard deviations of peak areas were 0.95% for the packed column and 0.43% for the capillary at the level of 100 ng mL−1 in both cases. The column treatment technique was applicable to determination of methylmercury in fish samples.
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  • 91
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phases ; Isomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Heptakis(2,6-di-O-benzyl)-β-CD(I), heptakis(2,6-di-O-benzyl-3-O-pentyl)-β-CD(II), heptakis(2,6-di-O-benzyl-3-O-methyl)-β-CD(III) and heptakis(2,6-di-O-benzyl-3-O-acetyl)-β-CD(IV) derivatives were synthesized and identified. Their thermal stabilities were tested using PyGC. These CD derivatives are stable up to 300°C and suitable for use as gas chromatographic stationary phases. The fused silica capillary columns coated with heptakis(2,6-di-O-benzyl-3-O-methyl)-β-CD and heptakis(2,6-di-O-benzyl-3-O-pentyl)-β-CD showed excellent chromatographic properties in separating positional isomers.
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  • 92
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Tenax-TA sampling ; Thermal desorption ; Preconcentration ; Flame ionization detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary By participating in an International Hydrocarbons Intercomparison Experiment, a method for the determination of nonmethane hydrocarbons was evaluated. The method involves Tenax-TA sampling, thermal desorption and preconcentration combined with capillary gas chromatography with flame ionization detection. Sixty target compounds from C2 to C11 were separated by using a megabore capillary column with a thick film of bonded nonpolar siloxane stationary phase (5 μm, Rtx-1). The unusually thick film in the column was an advantage for resolving light hydrocarbons (C2−C3) at room temperature. The percent difference between the National Institute of Standards and Technology (NIST) and our laboratory in the intercomparison experiment is in the range of 0.99%–19.70%.
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  • 93
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Modified silica gel ; Gaseous standard mixtures ; FID calibration ; Methyl chloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A possibility of extending analytical applications of chemically modified silica gels is described. This involves their utilization for the generation of gaseous standard mixtures consisting of methyl chloride as the analyte and nitrogen as a carrier gas to be used for the calibration of the GC-FID system. N-methylmorpholine was chemically bonded to the propylsilylated surface of silica gel forming chloride of an appropriate immobilized compound which, under certain conditions, undergoes thermal decomposition yielding a single, volatile component (methyl chloride). Such a method of generating specific amounts of a standard substance can be used both for a single point calibration and for checking the accuracy of an analytical instrument in a relatively wide measurement range. It was found that 3.40±0.081 mg of methyl chloride can be generated per 1 g of the modified gel.
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  • 94
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Aliphatic and aromatic aldehydes ; Thiazolidine derivatives ; Flame photometric detection ; Cigarette smoke
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A selective and sensitive method for the simultaneous determination of aliphatic and aromatic aldehydes in cigarette smoke by gas chromatography (GC) has been developed. After trapping of cigarette smoke into dilute hydrochloric acid containing ascorbic acid, aldehydes were converted into their thiazolidine derivatives by the reaction with cysteamine, and then measured by GC with flame photometric detection using two-connected fused-silica capillary columns containing DB-17 and DB-210, respectively. The derivatives were sufficiently volatile and gave single symmetrical peaks. The calibration curves for aliphatic and aromatic aldehydes in the range 20–2000 ng were linear and the detection limits at a signal-to-noise ratio of 3 were ca. 4–100 pg injected. Aliphatic and aromatic aldehydes in cigarette smoke could be selectively determined by this method without any interference from coexisting substances. Overall eecoveries of aldehydes added to cigarette smoke samples were 83–110%. Analytical results for the contents of aliphatic and aromatic aldehydes in mainstream and sidestream smokes of several cigarettes are presented.
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  • 95
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    Chromatographia 44 (1997), S. 497-504 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas chromatography-mass spectrometry ; Column liquid chromatography ; Polycyclic aromatic hydrocarbons ; Food analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several separation and detection methods for polycyclic aromatic hydrocarbons (PAHs) in smoked chicken by GC and HPLC were compared. With HPLC and a gradient solvent system, all 16 PAHs could be simultaneously separated and detected by fluorescence with seven settings of programmable wavelength (excitation/emission). The presence of impurities in smoked chicken could interfere with the subsequent identification and quantification of PAHs by HPLC. With GC and a temperature programming method, all 16 PAHs could be separated and the PAHs in the chicken sample could be detected with an ion-trap mass spectrometer even in the presence of fat-or PAH-like impurities. Nine PAHs were identified by the former method while fourteen PAHs were identified by the latter method. The retention times by HPLC were shorter than those by GC, also, the former had better separation for most PAHs than the latter.
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  • 96
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    Chromatographia 44 (1997), S. 505-513 
    ISSN: 1612-1112
    Keywords: Colum liquid chromatography ; Gel permeation chromatography ; Gas chromatography ; Organophosphorus, organochlorine and pyrethroid pesticides ; Multiresidue analysis in medicinal plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Multiresidue analysis of organophosphorus, organochlorine and pyrethroid pesticides in medicinal plants, gives problems of extraction, purification and detection. Analytical methodologies have been developed for vervain and tested for camomile and peppermint without prior knowledge of the pesticides used in their treatment. Extraction is common to all three pesticide families: acetone or acetonitrile is chosen depending on the particular matrix. Isolation of organophosphorus compounds is performed by gel permeation chromatography. Organochlorine and pyrethroid pesticides are extracted in two steps: gel permeation followed by adsorption chromatography on silica el cartridges. Analysis and detection of organophosphorus compounds is by gas chromatography with a nitrogen phosphorus detector; organochlorine and pyrethroid compounds are identified by gas chromatography with an electron capture detector.
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  • 97
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Surface ionization detection (SID) ; Cocaine ; Cocaethylene ; Cocapropylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Cocaethylene together with cocaine spiked in human whole blood has been found measurable at high sensitivities by capillary gas chromatography with surface ionization detection. The drugs could be rapidly extracted by Sep-Pak C18 cartridges with recovery of more than 60%. The calibration curves for both cocaethylene and cocaine using cocapropylene as internal standard were linear in the range 50–300 pmol mL−1 of whole blood. The detection limits of cocaethylene and cocaine were 5–10 pmol mL−1 (0.1–0.2 pmol on column if recovery is 100%). Cocaethylene could be determined for whole blood obtained from rats (ca. 200 g body wt.), which had received subcutaneous injection of 10 mg cocaine hydrochloride and 2.0 mL of 30% (v/v) ethanol 3 h before sampling; the mean levels of cocaethylene and cocaine were 101 and 1230 pmol mL−1, respectively.
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  • 98
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    International journal of legal medicine 111 (1997), S. 1-5 
    ISSN: 1437-1596
    Keywords: Key words Benzodiazepines ; Storage condition ; Long-term stability ; Forensic toxicology ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Notes: Abstract An approach to determine the stability of benzodiazepines and some of their metabolites (n = 13) by means of a routinely applied gas chromatographic method using electron capture detection was made in this preliminary study. Validation data of the method are given. Spiked blood and plasma samples were stored at 4° C and analysed at selected times up to 240 days. The concentrations of all analytes had decreased to at least 60% of the original levels at the end of the observation period. A clear pattern of breakdown could not be established. The data obtained suggest that results from long-term stored samples should be interpreted cautiously. Further investigations concerning the stability of drugs in blood and plasma samples, additional methods of identification and determination as well as the establishment of optimal storage conditions seem necessary.
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  • 99
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 363-368 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Solid-phase extraction ; Automation ; Water samples ; Acetylation ; Chlorophenols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An automated system for derivaatization was coupled on-line with solid-phase extraction-gas-chromatography (SPE-GC). The system was optimized for the determination of phenol and chlorinated phenols in aqueous samples. The test analytes were acetylated with acetic anhydride; proper buffering of the sample was a critical factor. Next, the phenol acetates were enriched on a SPE cartridge and transferred to a GC; two appraoaches were studied. In the first approach, the derivatives were enriched on disposable C18 cartridges (ASPEC type) and desorbed with methylacetate. Aan aliquot of the final eluate was injected on-line the GC by means of a loop-type interface. In the second approach, trace enrichment was performed on 10 × 2 mm i.d. LC-type precolumn packed with polystyrenedivinylbenzene copolymer (PLRP-S) this precolumn was dried with a mitrogen purge and the phenol acetates were desorbed with ethyl acetate which was injectedon-line into the retention gap of the GC under partially concurrent solvent evaporation (PCSE) conditions. The Derivatization-SPE-GC system which was based on the loop-type interface has the advantage of simplicity and easy operation, the main drawback is the impossibility to determine phenol acetates which elute prior to trichlorophenol acetates. With the derivatization-SPE-GC approach using PCSE-based desorption, even the most volatile analyte of the test series, phenol acetate, can be determined successfully. The entire procedure, including the derivatization step, was fully automated and integrated in one set-up. The precision data for the integrated on-line derivatization-SP-FID system were fully satisfactory, with RSD values of 1-12 % at the 1 μg/1 level. When a sample volume of 2.2 ml was analyzed, The detection limits for the chlorinated phenol acetates were in the 0.1-0.3 μg/1 range.
    Additional Material: 4 Ill.
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  • 100
    ISSN: 0935-6304
    Keywords: Supercritical Fluid Extraction (SFE) ; Gas chromatography ; Dicofol ; Fish ; LC50 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Toxicity evaluation of Dicofol to Astyanax bimaculatus schubarti, a characteristic fish species living in tropical rivers and lakes was carried out through LC50 - 96 Hours. These experiments were performed under laboratory controlled conditions with atmospheric air flow and dilution water at 25°C in the static mode, supercritical fluid extraction (SFE) with pure CO2 and CO2 modified with hexane and methanol were used at 50, 70, 80, and 100°C and 300 atm. Several collection modes were studied to extract Dicofol from fish samples. The extraction efficiencies were directly comparedd with those obtained after 8 h of Soxhlet extraction using the same clean-up with Florisil and analysis by HRGC/ECD and HRGC/MS as a confirmatory analytical technique. The SFE recoveries at temperatures lower than 80°C were typically lower than soxhlet recoveries; however a temperature increase enhanced the efficiency of SFE. The results showed that under certain conditions, supercritical fluid gave higher extractio power (extracted 11 % more pesticide), shorter extraction time, and lower solvent consumption than Soxhlet, thus affording an excellent alternative to the conventional method for extracting Dicofol from fish sample.
    Additional Material: 5 Ill.
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