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  • 1995-1999  (671)
  • 1998  (671)
  • Industrial Chemistry  (457)
  • Analytical Chemistry and Spectroscopy  (163)
  • Chemical Engineering
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  • 1995-1999  (671)
Year
  • 101
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 63-64 
    ISSN: 0935-6304
    Keywords: Injection port performance ; comprehensive two-dimensional GC ; GC× ; GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 102
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 65-68 
    ISSN: 0935-6304
    Keywords: GC-MS ; rain ; roof runoff ; fatty acids ; phenols ; alkanes ; chlorinated compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 103
    ISSN: 0935-6304
    Keywords: gas chromatography, helium ionization detector (HID) ; formaldehyde ; atmospheric oxygenates ; volatile organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Two different gas chromatographic detectors, the helium ionization detector (HID) and the more commonly used flame ionization detector (FID), were used in parallel to compare their responses to a number of organic compounds. Atmospherically important oxygenated species were analyzed, as well as hydrocarbons and chlorinated and sulfur containing organics. The HID exhibited the better response to all compounds investigated, most notably to formaldehyde and higher oxygenates. A gas chromatographic system was developed to trap and analyze atmospheric organic compounds with HID detection. This required careful choice of the adsorbent material and removal of inorganic components (namely nitrogen and oxygen) before analysis. Real air samples were then taken and analyzed qualitatively for a range of olefinic and aromatic compounds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 104
    ISSN: 0935-6304
    Keywords: high temperature capillary GC ; high temperature capillary GC-MS ; organic tracers ; OV-1701-OH ; smoke aerosols ; triglycerides ; wax esters ; triterpenyl esters ; Amazon ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A custom-made glass capillary column coated with OV-1701-OH (88% methyl, 7% cyanopropyl, 5% phenylpolysiloxane) was used to analyze smoke samples from biomass combustion of different species of plants collected in the Amazon forest. CS2 was used as solvent in order to enhance the dissolution and analysis of the heavier molecular weight components. The performance of the column was monitored during the experiments and a moderate increase in activity was observed after taking the column to high analytical temperatures (390°C). Trennzahl values typically dropped 20-30% from 1.7/m to the average of 1.35/m. In general, the performance of the custom-made column was satisfactory and comparable to the commercial high temperature columns. The high temperature high resolution GC and GC-MS analyses revealed the presence of a number of high molecular weight components reported to occur in smoke aerosols for the first time. These components consisted of series of wax esters (long chain alcohols esterified with long chain fatty acids) with up to 58 carbon numbers, aliphatic hydrocarbons, triglycerides, triterpenyl esters (e.g. α- and β-amyryl stearate). Although other types of compounds were also detected, their complete structure elucidation solely by electron impact MS was not adequate and other techniques will be required.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 105
    ISSN: 0935-6304
    Keywords: cyclodextrin derivatives ; enantiomer micropreparative GC ; thick-film wide-bore columns ; high-purity enantiomer isolation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Representative examples of preparative GC isolation of pure enantiomers in amounts ranging from 0.5 to 2 mg, with thick-film wide-bore open tubular columns coated with cyclodextrin (CD) diluted in polysiloxanes, are described. Two 25 m×0.53 mm i.d. columns, coated with 3 μm of 30% 2,6-di-O-methyl-3-O-pentyl-β-CD/OV-1701 and 2 μm of 30% 2,3-di-O-acetyl-6-O-tert- butyldimethylsilyl-β-CD/PS-086 as stationary phases, were used. Methyl 3-hydroxyhexanoate, methyl 2-methylbutanoate, δ-hexalactone, δ-octalactone, and γ-decalactone (the latter from a nature-identical mango aroma), were submitted to automated micropreparative GC. Average yields of about 30% were achieved when amounts above 20 μg/μl were injected, and an enantiomeric purity above 90% was obtained.
    Additional Material: 2 Ill.
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  • 106
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 121-123 
    ISSN: 0935-6304
    Keywords: gas chromatography ; capillary columns ; column efficiency ; column comparison ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The correct meaning of the the term “utilization of the theoretical efficiency” vs. the “coating efficiency” is explained.
    Additional Material: 1 Tab.
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  • 107
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 125-127 
    ISSN: 0935-6304
    Keywords: multidimensional gas chromatography ; self-made connectors ; effluent splitting ; press fit connectors ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 108
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 133-136 
    ISSN: 0935-6304
    Keywords: GC ; analysis of vegetable oil ; petroselinic acid ; butyl esters ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 109
    ISSN: 0935-6304
    Keywords: Enantioselective multidimensional capillary gas chromatography (enantio-MDGC) ; stable isotope ratio mass spectrometry (IRMS) ; multidimensional gas chromatography coupled on-line with isotope ratio mass spectrometry (MDGC-IRMS) ; calibration; isotope discrimination ; authenticity control ; authentication of genuine flavor components ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Multidimensional gas chromatography coupled on-line with isotope ratio mass spectrometry (MDGC-IRMS) is presented as a powerful method for origin-specific analysis. Scope and limitations of this sophisticated coupling technique are discussed with regard to accuracy and precision.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 110
    ISSN: 0935-6304
    Keywords: Epoxytriacylglycerols ; high temperature gas chromatography ; hydroxytriacylglycerols ; ketotriacylglycerols ; lipids ; negative chemical ionization mass spectrometry ; SOP-50 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Five seed oils consisting of unusual triacylglycerols have been examined by high temperature gas chromatography using glass capillary columns coated with the stationary phase SOP-50 (50%-diphenyl-50%-dimethylpolysiloxane, methoxy-terminated). The investigated hydroxy, epoxy, and ketokonjuene triacylglycerols were first derivatized in order to permit analysis by high temperature gas chromatography. Structural elucidation of the intact triacylglycerols was performed with high temperature gas chromatography/negative chemical ionization-mass spectrometry using NH3 as a reagent gas. Individual derivatized lipid species with a molecular weight up to 1176 g/mol could be identified.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 111
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 175-180 
    ISSN: 0935-6304
    Keywords: Supercritical Fluid Extraction (SFE) ; supercritical fluid chromatography ; solid trapping ; solvent trapping ; polymeric phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---One way of collecting extracted analytes after a supercritical fluid extraction (SFE) is to pass the depressurized fluid through a trap composed of a solid adsorbent. The influence of the adsorbent nature on the trap efficiency has been studied. First, the retention factors of each compound of a polarity test mix (tetracosane, naphthalene, fluoranthene, acetophenone, N,N-dimethylaniline, 2-naphthol, decanoic acid) have been determined on five high specific area (greater than 800 m2/g) polymeric phases by supercritical fluid chromatography (SFC). The comparison of this values with those obtained on octadecyl silica (ODS) showed that polymeric phases have the greatest retention power. After that, the efficiency of a solid trap filled with the greatest retention power polymeric adsorbent was evaluated by using pure carbon dioxide and 2.5%, 5%, 10%, and 20% methanol-modified carbon dioxide. As expected, this trap permitted a quantitative collection of all the former compounds even when a content as high as 10% of methanol was implemented. A solid trap filled with ODS adsorbent allowed quantitative collection of all the compounds only at a methanol content lower than 2.5%.
    Additional Material: 7 Ill.
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  • 112
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 185-188 
    ISSN: 0935-6304
    Keywords: Dill ether ; stereoselective synthesis ; dill ether stereoisomers ; enantioselective GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 113
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 197-199 
    ISSN: 0935-6304
    Keywords: Chiral recognition of 2-pentanol enantiomers ; enantioselective interactions ; capillary gas chromatography ; permethylated-β-cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 114
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 209-214 
    ISSN: 0935-6304
    Keywords: Dual capillary gas chromatography ; non-methane hydrocarbons (NMHCs) ; refocusing ; PLOT column ; carbon dioxide interference ; ambient air analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analytical method based on a dual capillary gas chromatographic technique combining the advantages of GasPro PLOT and a non polar narrow bore WCOT column was developed for the analysis of air samples containing C2-C9 NMHCs. A refocusing step was not required due to the fast heating rate of the sample preconcentration trap and the resolving power of the PLOT column for C2 and C3 NMHCs. Water had to be removed from the air samples to avoid plugging of the columns if the initial GC oven temperature was below ambient temperature. To dry air samples, a scrubber and a cryogenic technique were employed. The interferences caused by carbon dioxide were reduced by purging the loaded sample preconcentration trap with helium. The dual column system was compared to a method employing a refocusing device and a single narrow bore WCOT column. Both systems provided a high degree of precision. However, the dual column approach was superior to the single column system due to better resolution of low molecular weight components.
    Additional Material: 7 Ill.
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  • 115
    ISSN: 0935-6304
    Keywords: Chiral GC ; chiral stationary phase ; cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---2,3-Di-O-pentyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin has been evaluated as an enantioselective stationary phase for capillary gas chromatography. Experimental results show a good enantioselectivity towards compounds with different functional groups (haloalkanes, alcohols, esters, terpenoids, amino acid derivatives, and heterocycles). Column stability improves mixing the chiral phase with polysiloxane SE-54 (1 : 1).
    Additional Material: 2 Ill.
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  • 116
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 245-251 
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction (SFE) ; liquid trapping ; fat-soluble vitamins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A series of four complete factorial experiments were performed to determine the major parameters affecting the trapping efficiencies of fat-soluble vitamins after supercritical fluid extraction. The parameters varied were the collection solvent, extraction flow rate, collection temperature, restrictor temperature, and collection pressurization. The identity of the collection solvent was found to have the most profound effect. The viscosity and surface tension of the collection solvent appeared to have great significance.
    Additional Material: 3 Ill.
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  • 117
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 587-591 
    ISSN: 0935-6304
    Keywords: capillary GC ; polymethoxyflavones ; citrus oil ; GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The cold pressed peel oils of three species of citrus fruit, viz. sweet orange, tangerine, and grapefruit, have been examined for polymethoxyflavones by GC and GC-MS. Four GC column stationary phases were compared and separation of the six predominant orange oil polymethoxyflavones was obtained isothermally at 310°C in under ten minutes, including the resolution of the polymethoxyflavones from β-sitosterol. The nature of the stationary phase and the analysis temperature exercise dramatic effects on the resolution and elution order of the components, DB-35ms providing the best overall separation. A temperature programmed separation is also presented and the polymethoxyflavone composition of all three oils, as determined by GC-MS, is described. This is the first reported GC-MS study of the PMFs of these citrus species. While tangerine oil is as rich in polymethoxyflavones as orange oil, they are less abundant and occur at lower concentrations in grapefruit oil. Hydroxy-polymethoxyflavones were identified by GC-MS in tangerine oil. One hydroxy-pentamethoxyflavone, M+ = 388, identified in tangerine was also present at low levels in both orange and grapefruit oils. These results are compared with previous studies utilizing HPLC and GC.
    Additional Material: 6 Ill.
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  • 118
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 605-607 
    ISSN: 0935-6304
    Keywords: Reversed-flow MEKC ; separation according to polarity ; organic modifiers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Reversed-flow MEKC, i.e. MEKC at low pHs to suppress the electroosmotic flow, was evaluated for the separation of some homologous series. At low pHs compared to MEKC, the elution order reverses and normal phase type migration is obtained. Moreover, the elution window is nearly infinite. Efficiencies are very high and reproducibilities in absolute migration times are acceptable (%RSD 〈 5). The influence of a series of alcohol modifiers was investigated.
    Additional Material: 2 Ill.
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  • 119
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 597-604 
    ISSN: 0935-6304
    Keywords: high temperature gas chromatography ; atomic emission detection ; microwave induced plasma ; compound independent calibration ; non-ionic surfactants ; alcohol ethoxylates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---High temperature gas chromatography (HT-GC) coupled to atomic emission detection (AED) has been applied for the determination of alkyl chain distribution, mole average degree of ethoxylation and weight percent distribution of the corresponding homologues of alcohol ethoxylates without all the actual homologues being available as pure references. Based upon its constant elemental response, the HT-GC-AED system has been evaluated for its applicability to compound independent calibration within the homologous series of the alcohols and alcohol ethoxylates. Discrimination against high molecular weight components by gas chromatography requires conversion to the acetyl or trimethylsilyl derivatives. The latter includes introduction of the hetero atom silicon and thus allows monitoring of the silicon trace. Thus selectivity will be enhanced by excluding detection of compounds which do not react with the derivatization reagent. The method has been validated with the analysis of the technical product Brij 30, consisting of a mixture of alcohol ethoxylates with a vendor-specified mole average degree of ethoxylation of four. The experimental result yields a mole average degree of 4.0 ± 0.1 in the carbon, silicon and oxygen traces.
    Additional Material: 12 Ill.
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  • 120
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 608-612 
    ISSN: 0935-6304
    Keywords: propolis ; profiling ; CZE ; MEKC ; flavonoids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The usefulness of capillary electrophoresis (CE) with diode array detection for the profiling of Propolis, a hive product, is investigated. Water extracts of Propolis were analyzed with both capillary zone electrophoresis (CZE) at pH 7.0 and 9.3, and micellar electrokinetic chromatography (MEKC) with sodium dodecyl sulfate at pH 9.3. Characteristic profiles were obtained and several organic acids and preservatives could be identified by means of library comparison of the recorded UV spectra combined with addition of reference compounds to the extracts. The selectivity of the CZE and MEKC system differed considerably but the information obtained with both methods was similar. The dry residues of the water extraction were extracted with ethanol-water (70 : 30, v/v) and analyzed with the MEKC system to enable the separation of the more hydrophobic constituents of the Propolis samples. Complex profiles containing various well separated peaks were obtained allowing the identification of some interesting flavonoids. On the basis of the recorded CZE and MEKC profiles, the Propolis samples could be divided into two clearly different groups which are probably from a different origin.
    Additional Material: 4 Ill.
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  • 121
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 625-627 
    ISSN: 0935-6304
    Keywords: End-closure ; end-seal ; static coating ; glass and fused silica capillaries ; press-fit cap ; polyethylene closure ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 122
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; microplasma mass spectrometry ; radio frequency plasma ; element-selective detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Simultaneous element-selective detection of the halogens and carbon was accomplished with capillary gas chromatography coupled with microplasma mass spectrometry. The microplasma ion source was a radio frequency plasma contained inside the last 4-5 cm of the 0.32 mm i.d. fused silica capillary column. The ion source was located inside the high vacuum housing of the MS, and only the GC carrier gas (2.3 mL min-1 of helium) was used for plasma generation. Atomic ions were detected in the positive mode. Detection limits were in the low picogram area, and the selectivity to carbon ranged from 8×102 for fluorine to higher than 104 for the other halogens. By introduction of both hydrogen and oxygen as reagent gases, peak tailing was avoided by suppression of analyte reactions with the silica walls of the ion source. Special attention was given to the fluorine-selective detection due to an interfering background species at m/z 19, assumed to be H3O+ originating from the reagent gases. The background signal was minimized by careful control of the power level.
    Additional Material: 5 Ill.
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  • 123
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 107-112 
    ISSN: 0935-6304
    Keywords: Linalool; linalyl acetate ; enantioseparation by enantioselective gas chromatography ; enantiomer distributions in natural products obtained by different extraction processes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The enantiomeric distributions of linalool and linalyl acetate in various natural products are measured by enantioselective gas chromatography on alkyl-substituted cyclodextrins. Different plant cultivars were investigated by four extraction processes: steam distillation, solvent extraction, supercritical fluid extraction, and headspace analysis. Careful attention must be paid to linalool which undergoes partial racemization under certain processing conditions. In most cases, enantiomeric distribution is a powerful tool for authenticity testing.
    Additional Material: 1 Ill.
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  • 124
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 113-120 
    ISSN: 0935-6304
    Keywords: Enantioselective GC of chlorinated bis(propyl) ethers ; environmental analysis ; contamination of the Elbe River ; cyclodextrin derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Cyclodextrin derivatives are evaluated as chiral stationary phases for the enantiomer separation of chlorinated bis(propyl) ethers (BPE). The enantiomeric composition of the 2,3,2′,3′- and 1,3,2′,3′-isomers of tetrachlorobis(propyl) ether in the Elbe River has been quantitatively determined by enantioselective gas chromatography and coupled gas chromatography/mass spectrometry in selected-ion-monitoring mode. Significant enantiomeric discriminations are observed in selected water samples, indicating that enantioselective bio-degradation mechanisms are at least partly responsible for the overall degradation processes.
    Additional Material: 5 Ill.
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  • 125
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 128-132 
    ISSN: 0935-6304
    Keywords: Pyrolysis ; GC/MS ; phenolic urethane resin ; thermal decomposition ; metal casting ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 126
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 137-139 
    ISSN: 0935-6304
    Keywords: Pentachlorophenol ; urine ; microextraction ; SPME ; GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 127
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 161-168 
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; optimization ; mixture design ; DUP 654 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Capillary Electrochromatography (CEC) offers a rapid, economical, and efficient means for resolving nonionic compounds in the reversed phase mode on octadecylsilane (ODS) columns. A CEC optimization on a Hypersil ODS capillary column was employed to identify a suitable mobile phase for the pressure-driven (reversed phase ODS) separation of the anti-inflammatory 2-phenylmethyl-1-naphthol (DUP 654), and its related substances. The proportions of mobile phase modifiers methanol, acetonitrile, and water as well as pH were employed as variables in a stacked mixture design. Comparable response surface profiles were obtained for the CEC separations at pH 4 and pH 8. However, subtle differences were evident in the quality of separations obtained in the liquid chromatographic (LC) mode when using a specially-prepared column packed with exactly the same stationary phase as used in the CEC experiments. A mapping of the response surface for separations on a commercially available Hypersil ODS LC column revealed obvious differences. The differences indicate that the transfer of ODS based separation methods between CEC and LC involves more than simply transferring the conditions from one mode to the other.
    Additional Material: 7 Ill.
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  • 128
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 169-174 
    ISSN: 0935-6304
    Keywords: CZE ; detection limit ; signal-to-noise ratio ; correlation chromatography ; reproducibility ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Poor signal-to-noise ratios and analytical reproducibility in capillary electrophoresis were improved by application of multiple injections of the same sample at (pseudo) randomly chosen time moments. One order of signal-to-noise ratio improvement was achieved in practice using an in-house developed computer-controlled pneumatic sampler. However, it is demonstrated here that better implementation of the capabilities of multiple input requires that the detector signal noise be “pre-whitened”, i.e. spikes, baseline drift, oscillations etc. must be removed from the detector signal before transforming it to the electropherogram in the common form. Such filtering of the detector signal was realized by implementing iterative, menu-driven software written in Matlab, a high-level programming language.
    Additional Material: 5 Ill.
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  • 129
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 181-184 
    ISSN: 0935-6304
    Keywords: Trace analysis, atmospheric ; digital signal processing ; signal to noise reduction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 130
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 189-192 
    ISSN: 0935-6304
    Keywords: Chiral stationary phases ; pyrethroic acids ; enantiomer separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 131
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 193-196 
    ISSN: 0935-6304
    Keywords: capillary electrophoresis ; dissolving solvent selection ; optimization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 132
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    Journal of High Resolution Chromatography 21 (1998), S. 201-208 
    ISSN: 0935-6304
    Keywords: PAN ; peroxyacetyl nitrate ; alkyl nitrate ; chlorinated hydrocarbons ; halocarbons ; capillary GC-ECD ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A cryogenic preconcentration/high-resolution gas chromatographic technique has been developed for the rapid, simultaneous quantitation of C1-C4 organic nitrates and halocarbons in ambient air. Whole-air samples are collected in TedlarTM bags by an evacuated-chamber method. Samples were stable in 0.010-cm-thick bags for 24 h if they were immediately stored in a freezer at -25°C. Analytes in a 50-cm3 air sample were efficiently preconcentrated on fused-silica beads at -180°C and thermally desorbed at 30°C. High-resolution gas chromatography with a cross-linked polydimethylsiloxane fused-silica capillary column and an electron-capture detector were used for separation and quantitation of the analytes. An analysis time of about 12 min was facilitated by sample cryofocusing at -180°C and oven temperature programming. Recoveries of the analytes by the evacuated-chamber method were better than 95%. The sensitivity of the technique for sample volumes of 50 cm3 is in the sub-parts-per-trillion by volume (ppt[v]) range for many of the analytes, with an average precision of about ±5% for analytes at levels of about 10 ppt(v).
    Additional Material: 4 Ill.
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  • 133
    ISSN: 0935-6304
    Keywords: capillary electrophoresis ; enantiomer separation ; hydroxypropyl-β-cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Following an extended screening project, 86 racemic drugs were investigated by capillary zone electrophoresis in the presence of the chiral solvating agent (CSA) hydroxypropyl-β-cyclodextrin. A total of 42 drugs out of 86 tested was thereby separated into enantiomeric pairs. Statistical analysis of the numerous experiments performed un der identical conditions reveals a loose correlation of the migration separation factor (αm) with the migration retardation factor (Rm). For a subset of 23 drugs, a drop in the concentration of the CSA was also studied, showing the way to further optimization.
    Additional Material: 6 Ill.
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  • 134
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    Journal of High Resolution Chromatography 21 (1998), S. 253-257 
    ISSN: 0935-6304
    Keywords: Edible oils ; lipids in foods ; HPLC ; Polycyclic Aromatic Hydrocarbons (PAHs) ; off line LC-LC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 135
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    Journal of High Resolution Chromatography 21 (1998), S. 234-240 
    ISSN: 0935-6304
    Keywords: Micellar electrokinetic capillary chromatography ; electroosmotic migration ; electrophoretic migration of micelle ; retention mechanism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In the present work, four organic modifiers, viz. urea, dioxane, methanol, and tetrahydrofuran, were comparatively and systematically studied in terms of their effects on electrokinetic migration behavior and the retention mechanism of homologous solutes in MECC. The results showed that the electroosmotic mobility, μeo, and the electrophoretic mobility of a micelle, μep,mc, decrease linearly with increasing organic modifier concentration. The ability of organic modifiers to lower μeo is greater than their ability to lower μep,mc. The negative values of the slopes of these linear relationships, Deo and Dep,mc, increase along the series the order urea 〈 methanol 〈 dioxane 〈 tetrahydrofuran. The logarithm of the capacity factor (ln k′) of uncharged homologous solute, which is mainly determined by the hydrophobic interaction, decreases linearly with increasing organic modifier concentration, due not only to the decrease in the partition coefficient but also to the decrease in the phase ratio. A linear relationship was observed between the slope of the plot of ln k′ vs. organic modifier concentration and the carbon number of homologous compound. The slope of such a relationship can characterize the hydrophobicity of the organic modifier. The hydrophobicity of such organic modifiers is also found to increase along the series urea 〈 methanol 〈 dioxane 〈 tetrahydrofuran.
    Additional Material: 7 Ill.
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  • 136
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    Journal of High Resolution Chromatography 21 (1998), S. 258-262 
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; splitless injection ; large sample volume ; injector design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 137
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    Journal of High Resolution Chromatography 21 (1998), S. 291-297 
    ISSN: 0935-6304
    Keywords: Gradient ; liquid chromatography ; micro-HPLC ; mixer ; electrospray mass spectrometry ; cytochrome c ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper describes a new method for gradient elution at low flow rate. By adjusting the solvent composition flowing into a dynamic mixer, we can program the concentration of solvent, B, inside a dynamic mixer to form a time-resolved solvent gradient delivered to the column. The input gradient is related to the output gradient by the equation, Bin = Bout + τ × dBout/dt, in which τ is the gradient response time constant at specified flow rate, and Bin and Bout are input and output concentration of solvent B, respectively.
    Additional Material: 8 Ill.
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  • 138
    ISSN: 0935-6304
    Keywords: chemiluminescence detector ; guava ; MDGC ; 2-pentanethiol ; Psidium guajava ; SCD ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 139
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    Journal of High Resolution Chromatography 21 (1998), S. 378-382 
    ISSN: 0935-6304
    Keywords: Large volume injection ; on-column injection ; flooded zone ; solvent trapping ; temperature measurement on precolumn wall ; water analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Solvent trapping reconcentrates volatile components after injection or on-line transfer of large volumes. When an early vapor exit is used, typically after a 5-10 m × 0.53 mm i.d. uncoated precolumn, the solvent trapping process differs from that described previously. The visual experiments and the conclusions drawn therefrom, as described in a previous paper, are supplemented with chromatographic results. They show that even hexane can be quantitatively analyzed in 250 μl of a pentane solution. Injection of a volume of 250 μl by vaporizer/precolumn solvent splitting was used in the analysis of gasoline in drinking water. Conditions for the transfer of a 1000 μl volume can easily be adjusted through detection of the front end of the flooded zone by a thermocouple mounted on the outer wall of the precolumn.
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  • 140
    ISSN: 0935-6304
    Keywords: high temperature gas chromatography ; flavonoids ; propolis ; high molecular weight compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The underivatized acetone and hexane fractions from propolis samples (predominant flora Citrus spp. and Vernonia polyanthes) were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds, including flavonoid aglycones, phenolic acids, and high molecular weight compounds were characterized in crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude extracts without need for prior derivatization and purification.
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  • 141
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    Journal of High Resolution Chromatography 21 (1998), S. 411-413 
    ISSN: 0935-6304
    Keywords: Modulator ; GC x GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 142
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    Journal of High Resolution Chromatography 21 (1998), S. 401-406 
    ISSN: 0935-6304
    Keywords: capillary electrophoresis ; Turkey Red Oil ; surfactants ; industrial process water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A method using capillary electrophoresis with direct UV detection has been developed and validated for the determination of Turkey Red Oil (sulfonated castor oil). The highest performance with respect to separation efficiency and analysis time was achieved with 30 mM Tris (pH 8.0) buffer containing 7.5 mM HP-β-CD. The feasibility of the proposed CE method for the analysis of Turkey Red Oil surfactant in industrial water samples is demonstrated. Spiking of real samples gave recoveries between 90 and 106%. The CE results were compared with that obtained by GC-MS. It was concluded that CE can be a good alternative for fast determination of Turkey Red Oil component distribution in industrial process waters with no sample preparation other than dilution. However, the method sensitivity is not satisfactory for monitoring surfactant level in a waste effluent stream.
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  • 143
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    Journal of High Resolution Chromatography 21 (1998), S. 417-420 
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; dihydrotestosterone esters ; dihydroepitestosterone esters ; Kováts retention indices ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 144
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    Journal of High Resolution Chromatography 21 (1998), S. 427-434 
    ISSN: 0935-6304
    Keywords: Linear solvation energy relationship ; retention ; mobile phase ; stationary phase ; additives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Linear solvation energy relationships (LSERs) were used to delineate which specific intermolecular interactions are responsible for changes in retention for a variety of well characterized analytes when acidic and basic additives were used in reversed phase HPLC. The effects of trifluoroacetic acid, triethylamine and a combination of trifluoroacetic acid and triethylamine on the LSERs were compared to those observed in the absence of additives. These effects were examined using four different mobile phase modifiers and five different stationary phases. Trifluoroacetic acid alone and in combination with triethylamine produced LSER regression coefficients nearly identical to those obtained with no additive present in the mobile phase. Triethylamine alone produced different LSER regression coefficients from the other systems unless the mobile phase contained trifluoroethanol as the mobile phase modifier, or the stationary phase consisted of a polymeric support.
    Additional Material: 3 Ill.
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  • 145
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    Journal of High Resolution Chromatography 21 (1998), S. 435-439 
    ISSN: 0935-6304
    Keywords: Micellar Electrokinetic Chromatography (MEKC) ; counter pressure moderated MEKC ; migration time window ; peak resolution and peak capacity in MEKC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The influence of a hydrostatic counter pressure on basic mobility equations in MEKC was analyzed theoretically and investigated experimentally. Taking into account the influence of counter pressure, the modified mobility equations predict a decreased migration time ratio t0/tMC, which was confirmed by results obtained in SDS-MEKC separation of a homologous series of n-alkyl phenyl ketones. As a result, the migration time window could be enlarged in a simple way without having to change the chemistry of the system. Although counter pressures reduce peak efficiency in MEKC by disturbing the plug profile, the concomitant enlargement of the migration time window compensates for this effect. Especially for later migrating compounds, peak resolution could be enhanced at moderate counter pressures. The overall peak capacities within the whole migration window increases slightly when applying counter pressures up to 10 mbar.
    Additional Material: 3 Ill.
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  • 146
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    Journal of High Resolution Chromatography 21 (1998), S. 445-449 
    ISSN: 0935-6304
    Keywords: chiral separation ; organic cation effect ; ethylamines ; ethanolamines ; basic drugs ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper addresses the influence of small organic cations in the background electrolyte (BGE) on chiral separation by capillary zone electrophoresis (CZE). Seven basic drugs, viz. alprenolol, amphetamine, anisodamine, isoprenaline, pinacidil, synephrine, and verapamil were used as test compounds with hydroxylpropyl-β-cyclodextrin (HP-β-CD) as the chiral selector. Resolution of the chiral test compounds was studied at pH 2.5 in the presence of Tris, ethanolamine, diethanolamine, triethanolamine, diethylamine, and triethylamine, which exist in their cationic forms at this pH value. Among the six cationic additives studied, triethylamine is most effective in enhancing resolution. A tentative mechanism of the effect is proposed.
    Additional Material: 7 Ill.
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  • 147
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    Journal of High Resolution Chromatography 21 (1998), S. 450-456 
    ISSN: 0935-6304
    Keywords: Drying cartridge ; gas chromatography ; solid-phase extraction ; microcontaminants ; water samples ; on-line SPE-GC ; mass spectrometric detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A drying cartridge was used and optimized for the in-line elimination of water from the desorption eluent in on-line solid phase extraction-gas chromatography (SPE-GC). The cartridge is essentially a small stainless-steel precolumn packed with a drying agent which can be regenerated by simultaneous heating and purging with a moisture-free gas. The drying cartridge was mounted on an additional valve instead of between the SPE-GC transfer valve and the on-column injector to enable regeneration of the cartridge during the GC run and, thus, to increase sample throughput. Three drying agents were tested, viz. sodium sulfate, silica, and molecular sieves. Although molecular sieves have the highest capacity, silica was preferred because of practical considerations. Large-volume injections were performed through the in-line drying cartridge using a mixture of 23 microcontaminants ranging widely in polarity and volatility. Four solvents were tested. With pentane and hexane, the more polar analytes were retained by the drying cartridge. Ethyl acetate and methyl acetate gave much better (and closely similar) recoveries for all analytes. Because water elimination on the silica cartridge proved to be less critical than with ethyl acetate, this solvent was finally selected. The entire SPE-drying cartridge-GC set-up was combined with mass spectrometric (MS) detection for the determination of a mixture of micropollutants in real-life water samples. With 10-ml tap water samples spiked at the 0.5 μg/l level, for the majority of the test compounds the analyte recoveries generally were 60-106%, and (full-scan) detection limits typically were 0.01-0.03 μg/l. Some very polar analytes such as, e.g. dimethoate, were (partially) sorbed onto the silica packing of the drying cartridge.
    Additional Material: 4 Ill.
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  • 148
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    Journal of High Resolution Chromatography 21 (1998), S. 464-470 
    ISSN: 0935-6304
    Keywords: liquid chromatography ; chiral separation ; chiral recognition mechanism ; chiral stationary phase ; separation of enantiomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A chiral recognition mechanism which can rationalize the resolution of N-(3,5-dinitrobenzoyl)-α-amino amides on chiral stationary phases (CSPs) obtained from N-(3,5-dinitrobenzoyl)leucine amide derivatives has been proposed on the basis of the chromatographic resolution behavior of various N-(3,5-dinitrobenzoyl)-α-amino acid derivatives and N-(various benzoyl)leucine N-propyl amides. The proposed chiral recognition mechanism utilizes two hydrogen bonding interactions between the CSP and the analyte and a π-π donor-acceptor interaction between the N-(3,5-dinitrobenzoyl) groups of the CSP and the analyte. From the chiral recognition mechanism proposed, it has been concluded that the resolution of π-acidic N-(3,5-dinitrobenzoyl)-α-amino acid derivatives on π-acidic CSPs derived from N-(3,5-dinitrobenzoyl)leucine amide delivatives is not unusual, but is merely the extension of the resolution of the π-basic racemates on π-acidic CSPs. However, the chromatographic behavior of the resolution of N-(3,5-dinitrobenzoyl)phenylglycine derivatives on CSPs derived from N-(3,5-dinitrobenzoyl)leucine amide derivatives is different from that of the resolution of other N-(3,5-dinitrobenzoyl)-α-amino acid derivatives. To rationalize this exceptional behavior, a second chiral recognition mechanism which utilizes two hydrogen bonding interactions (which are different from those of the first chiral recognition mechanism) between the CSP and the analytes and a π-π donor-acceptor interaction between the N-(3,5-dinitrobenzoyl) group of the CSP and the phenyl group of the analytes has been proposed to compete with the first chiral recognition mechanism. In this instance, it has been proposed that the separation factors and the elution orders of the resolution of N-(3,5-dinitrobenzoyl)phenylglycine derivatives are dependent on the balance of the two competing chiral recognition mechanisms.
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  • 149
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    Journal of High Resolution Chromatography 21 (1998), S. 477-479 
    ISSN: 0935-6304
    Keywords: Silica rod column ; micro-HPLC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 150
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    Journal of High Resolution Chromatography 21 (1998), S. 498-504 
    ISSN: 0935-6304
    Keywords: Nonaqueous solvents ; capillary electrophoresis ; charge transfer complexation ; argentation ; silver ion ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This study represents the first application of Ag(I) charge transfer complexation in nonaqueous capillary electrophoresis. This method applies the principles of argentation chromatography to nonaqueous electrophoretic separations and is termed “nonaqueous argentation electrophoresis”. Since the separations are performed in 100% nonaqueous media, the advantages of nonaqueous solvents, such as enhanced solubility and flexibility in selectivity enhancement, compared to an aqueous or mixed hydroorganic solvent, are realized. A variety of compounds were separated. Qualitatively, the separation of eleven sulfonamides in 100% acetonitrile is shown to improve greatly upon the addition of Ag(I). These results also show that nonaqueous argentation electrophoresis provides fast, well-resolved separations of compounds, such as N-containing heterocyclics, that can selectively complex with Ag(I). Migration data and separation selectivities of these compounds by nonaqueous argentation electrophoresis were compared to previous aqueous argentation electrophoresis results. Selectivities were found to be significantly different for the two separation media. Ag(I) complexation provides an effective means of manipulating selectivity in nonaqueous capillary electrophoresis.
    Additional Material: 9 Ill.
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  • 151
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    Journal of High Resolution Chromatography 21 (1998), S. 519-522 
    ISSN: 0935-6304
    Keywords: Supercritical Fluid Extraction (SFE) ; Micellar Eletrokinetic Capillary Chromatography (MEKC) ; Diuron ; sugar cane ; orange ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 152
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    Journal of High Resolution Chromatography 21 (1998), S. 509-512 
    ISSN: 0935-6304
    Keywords: Cholesterol oxidation ; gas chromatography ; oxysterols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The performance of a fused silica column coated with 50% phenyl-/50% dimethyl-polysiloxane, characterized by a high thermal stability, was evaluated for the gas chromatographic determination of cholesterol oxidation products. A silylated mixture of eighteen oxysterol standards (0.1 mg/ml of each compound) was injected into the gas chromatographic system. The temperature was programmed from 230 to 260°C at 2.5°/min and then to 290°C at 1°/min; the injector and detector temperatures were set at 325°C, and the gas linear velocity was 22.8 cm/s. The column gave a fast (15 min) and satisfactory resolution of the main cholesterol oxides. Good separation of the hydroxy from the epoxy derivatives was achieved.The suitability of the method for the determination of oxysterols in food matrices was successfully tested on a saponified lipid extract from egg yolk powder, previously enriched and purified by NH2 solid phase extraction.
    Additional Material: 3 Ill.
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  • 153
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    Journal of High Resolution Chromatography 21 (1998), S. 531-539 
    ISSN: 0935-6304
    Keywords: gas chromatography ; carrier gas flow ; loss modified Poiseuille flow ; hold-up times ; peak widths ; velocity profiles ; permeability of helium through fused silica ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Hold-up times and peak widths have been measured in long fused silica GC capillary columns at high temperature with helium as the carrier gas. The results lead to the conclusion that the helium permeates through the column walls. The conventional Poiseuille theory of carrier gas flow has been extended to include this phenomenon. The resulting “loss modified Poiseuille” model, which uses literature values for the permeability of fused silica to helium, has been used to simulate the observed behavior. Good agreement between simulation and experiment validates the model. Simulations have been used to explore the effect of column permeability on hold-up times, peak widths, and velocity profiles over a broad range of column geometries.
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  • 154
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    Journal of High Resolution Chromatography 21 (1998), S. 549-553 
    ISSN: 0935-6304
    Keywords: Hydroxytyrosol ; GC-MS ; wine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Hydroxytyrosol (HTy) is a potent natural antioxidant found in olive oil and in mill waste waters. Although wines are rich in polyphenols, hydroxytyrosol has not been identified in wines so far. We have analyzed ten wines from different grape varieties grown in several Italian regions, using a gas-chromatograph coupled to a mass selective detector (GC-MS). Solid-phase extraction of wine samples was performed on a C18 column, with ethyl acetate used as eluting agent. Eluates were derivatized with bis(trimethylsilyl)trifluoroacetamide (BSTFA) and analyzed by GC-MS using one target and two qualifying ions. The detection limit was 15 pg/μL, with 49% average recovery. Under these experimental conditions hydroxytyrosol was detected in all wines analyzed. Its average concentrations in red and white wines were 4.0 mg/L and 1.9 mg/L, respectively.
    Additional Material: 3 Ill.
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  • 155
    ISSN: 0935-6304
    Keywords: Ligand-exchange chromatography ; dodecyl-norephedrine ; enantiomeric separation ; amino alcohol ; coating ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Underivatized aliphatic β-amino alcohols with a primary or secondary alcohol moiety were separated into enantiomers by high performance liquid chromatography using octadecylsilanized silica coated with N-n-dodecyl-(1R,2S)-norephedrine as the stationary phase and an aqueous solution containing copper(II) and barbital as the mobile phase.
    Additional Material: 5 Ill.
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  • 156
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    Journal of High Resolution Chromatography 21 (1998), S. 554-560 
    ISSN: 0935-6304
    Keywords: LC stationary phases ; octadecyl and octylsilica characterization ; cyclodextrins ; partially methylated cyclodextrins ; heptakis(2,6-di-O-methyl)-β-CD ; evaporative light scattering detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In order to establish guidelines to help the analyst in the choice of the most suitable octadecyl or octyl bonded phase for the LC analysis of a given partially methylated β-CD sample, analyses of four commercially available dimethyl-β-cyclodextrins (DM-β-CDs) have been carried out on nine octyl (C8) or octadecyl (C18) silica bonded or polymeric bonded phases which differ significantly in their hydrophilic and hydrophobic properties. Chromatograms show that the nature of the packing materials has considerable influence on the resolution of complex mixtures composed of closely related compounds such as partially methylated β-CDs. Among various kinds of C8 and C18 bonded phases, silica based and monomeric phases which present both reinforced hydrophobic and polar interactions showed the best performance. Whatever the complexity of the commercial DM-β-CD, the richest chromatographic fingerprints, which best depict the complexity of the mixture, are obtained with Nucleosil 50-5-C8 column. For the simplest mixtures, Nucleosil 50-5-C8 column with acetonitrile-water (34:66) as mobile phase is the most suitable chromatographic system and leads to the best resolution between heptakis (2,6-di-O-methyl)-β-CD and hexakis (2,6-di-O-methyl)-mono(2,3,6-tri-O-methyl)-β-CD (14 OCH3 and 15 OCH3). This chromatographic system might enable an LC-MS coupling for direct identification of the different components in the mixture as well as control of batch to batch variations.
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  • 157
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    Journal of High Resolution Chromatography 21 (1998), S. 565-568 
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; precalculation of retention indices ; boiling points ; two- and multidimensional taxonomic groups of organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---It was shown that reciprocally unambiguous conformity between GC retention indices (at least for the commonly used standard nonpolar polydimethylsiloxane liquid phases) and boiling points of organic compounds is typical not only within one-dimensional taxonomic groups (homologous series and/or groups of congeners), but also within two- and multidimensional taxonomic groups (with simultaneous variations of some structural fragments). In all cases, this conformity is described by three-parameter non-linear equations log RI = a log Tb + b (n1 + Σ ki ni) + c, where n1 is the serial number of homologue within corresponding series and ni is the number of other structural fragments in the molecules. The coefficients ki in this equation reflect the relative alterations of molecular polarizabilities and may be estimated as ratios of refractions ki = RD(X)/RD(CH2), where X are variable structural fragments within a group of congeners, RD(CH2) = 4.647 cm3mol-1. The approach under discussion permits precalculation of the retention indices of any organic compounds with known boiling points. The precision of proposed method of RI precalculation is comparable with the contemporary level of interlaboratory reproducibility of experimental RI determination with standard nonpolar liquid phases (5-10 i.u.).
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  • 158
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    Journal of High Resolution Chromatography 21 (1998), S. 583-586 
    ISSN: 0935-6304
    Keywords: Fast gas chromatography ; narrow-bore columns ; flash-2D-GC ; dedicated fast GC instrumentation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Savings in analysis time in capillary GC have always been an important issue for chromatographers since the introduction of capillary columns by Golay in 1958. In laboratories where gas chromatographic techniques are routinely applied as an analytical technique, every reduction of analysis time, without significant loss of resolution, can be translated into a higher sample throughput and hence reduce the laboratory operating costs. In this contribution, three different approaches for obtaining fast GC separations are investigated. First, a narrow-bore column is used under conventional GC operating conditions. Secondly, the same narrow-bore column is used under typical fast GC conditions. Here, a high oven temperature programming rate is used. The third approach uses a recent new development in GC instrumentation: Flash-2D-GC. Here the column is placed inside a metal tube, which is resistively heated. With this system, a temperature programming rate of 100°/s is possible. The results obtained with each of these three approaches are compared with results obtained on a column with conventional dimensions. This comparison takes retention times as well as plate numbers and resolution into consideration.
    Additional Material: 4 Ill.
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  • 159
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    Journal of High Resolution Chromatography 21 (1998), S. 592-596 
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; new chiral selectors anchored to polysiloxane ; t-leucine derivatives ; immobilization ; radical-induced cross-linking ; low racemization of the phases ; high enantioselectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---New chiral polysiloxanes have been prepared as stationary phases for gas chromatography, with (S)-(-)-t-leucine-t-butylamide, (S)-(-)-t-leucine-(S)-(-)-1-phenylethylamide, (S)-(-)-t-leucine-(S)-(-)-1-(α-naphthyl)ethylamide, (S)-(-)-t-leucine-(R)-( + )-1-phenylethylamide, and (S)-(-)-t-leucine-(R)-( + )-1-(α-naphthyl)ethylamide as selectors. Immobilization is achieved by radical-induced cross-linking with 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (V4) and dicumyl peroxide (DCUP) as cross-linking reagents and cured at 170°C. Under these conditions, racemization of (S)-(-)-t-leucine is less than 4.5% (R) for 1 h curing, while for polysiloxanes with the conventional (S)-(-)-valine selectors about 20% of R-enantiomers are formed by racemization. In the presence of 5% (w/w) V4 and 6% of DCUP with regard to the phases, 70-80% immobilization is achieved; without V4, the degree of immobilization is about 50% for both the (S)-(-)-t-leucine and (S)-(-)-valine selectors. As the size of the amide moieties of the selectors increases from t-butyl to 1-(α-naphthyl)ethyl, the degree of immobilization decreases. If the curing time is prolonged to 2 h, the extent of racemization increases. The selectivity factors achieved for amino acid enantiomers and similar pharmaceuticals are generally higher than those obtained with the corresponding non-immobilized Chirasil-Val phases.
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  • 160
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    Journal of High Resolution Chromatography 21 (1998), S. 620-622 
    ISSN: 0935-6304
    Keywords: Multidimensional gas chromatography ; comprehensive two-dimensional gas chromatography ; kerosene analysis ; cryogenic modulation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 161
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    Journal of High Resolution Chromatography 21 (1998), S. 617-619 
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; cellulose acetate fiber ; microcolumn liquid chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 162
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    Journal of High Resolution Chromatography 21 (1998), S. 613-616 
    ISSN: 0935-6304
    Keywords: Micro LC ; FID detection ; superheated water ; alcohols ; aldehydes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In the current study, an HPLC-FID system using superheated water as the eluent is constructed and further improved. Signal stability during temperature programmed operation was improved by using separate thermostatting of the 50 μm capillary restrictor. Operating the restrictor at 75°C prevented the superheated water from sputtering in the restrictor. Conventional octadecyl-modified silica, thermostable polymeric reversed phase and carbon type HPLC columns were used. The feasibility of the system is demonstrated by the analysis of a variety of compounds such as alcohols and aldehydes. It is shown that increased temperatures decrease elution times and, in addition to this, frequently improve peak shapes and column efficiencies. The separation of lower aldehydes is performed at 175°C with a detection limit in the low μg/ml range. The possibility of temperature programming is demonstrated for the separation of a range of alcohols. Furthermore, it is shown that temperature programming can be used for sample enrichment. Large volume injection with low temperature enrichment resulted in good peak shapes and a significant improvement of the detection limit. In this way, detection limits of 0.2 μg/ml (ppm) could be obtained for the aldehydes studied. Finally, the possibilities of using mobile phase additives as, e.g., buffers were briefly examined.
    Additional Material: 5 Ill.
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  • 163
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    Journal of High Resolution Chromatography 21 (1998), S. 623-624 
    ISSN: 0935-6304
    Keywords: Sulfur compounds ; waste paper ; chemiluminescence detector ; food packaging ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
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  • 164
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    Journal of High Resolution Chromatography 21 (1998), S. 640-644 
    ISSN: 0935-6304
    Keywords: chiral separation ; uncharged and charged cyclodextrin ; borate complexation ; capillary electrophoresis ; propranolol and its metabolites ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A buffer system of borate with charged (carboxymethyl-β-CD) and uncharged (β-CD) cyclodextrins (CDs) was employed in the chiral resolution and separation of propranolol and its selected major metabolites. By appropriate choice of buffer and additive conditions, chiral resolution of all of the compounds studied was achieved in a single analysis, where near baseline resolution was found for the difficult to resolve propranolol-glycol (Pr-glycol). This has not been observed in previous studies of propranolol and its metabolites.
    Additional Material: 9 Ill.
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  • 165
    ISSN: 0935-6304
    Keywords: gas chromatography (GC) ; nitrogen-phosphorus detection (NPD) ; sorptive extraction/thermal desorption (SE/TD) ; amines ; in-situ derivatization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The use of sorptive extraction/thermal desorption (SE/TD) for the enrichment of amines from aqueous samples was investigated. The amines were derivatized in situ in the water sample by pentafluorobenzoyl chloride and subsequently enriched onto the SE cartridge. Two SE/TD cartridges were used, a commercially available polydimethylsiloxane (PDMS) packed cartridge and a similar cartridge prepared with newly synthesized poly(butyl acrylate) (PBA). Blank profiles of PBA were not as good as those obtained from the PDMS phase. A complex chromatogram was obtained using mass spectrometric detection. Fortunately, the use of a nitrogen-phosphorus detector (NPD) resulted in clean blanks. The PBA phase showed superior performance for the enrichment of the polar amine derivatives from water samples compared to the PDMS material. Using a CGC-NPD set-up and only 1 mL samples, detection limits are in the sub-ppb range.
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  • 166
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    Journal of High Resolution Chromatography 21 (1998), S. 661-664 
    ISSN: 0935-6304
    Keywords: SPME ; AED ; metazachlor ; pesticides ; waste water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 167
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    Journal of High Resolution Chromatography 21 (1998), S. 658-660 
    ISSN: 0935-6304
    Keywords: 1,3-Dioxolanes ; acetals ; ketals ; coffee-like flavorings ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper concerns a number of commercially available coffee-like flavoring preparations, identifying certain dioxolane structures of particular interest. The research was carried out by GC/MS, and spectral characterization was performed of the compounds in question, and especially of the acetals and ketals produced from compounds with carbonyl functions and 1,2-propylene glycol. Some determinations by means of chiral gas chromatography and by Isotope Ratio Mass Spectrometry (IRMS) have been useful in improving the analytical characterization of certain dioxolanes.
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  • 168
    ISSN: 0935-6304
    Keywords: PAHs ; on-line SPE ; disk extraction ; RPLC ; water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 169
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    Journal of High Resolution Chromatography 21 (1998), S. 32-38 
    ISSN: 0935-6304
    Keywords: LMCS ; column bleed ; modulation ; signal enhancement ; capillary GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A Longitudinally Modulated Cryogenic System (LMCS) was evaluated for its use in detection enhancement in capillary gas chromatography. The mechanism for chromatographic re-elution for the LMCS is substantially different to other cryogenic devices. The cooled region of the capillary column in which chromatographic bands may be focused is heated by the surrounding oven temperature either by moving the trap along the column, or by moving the column out of the trap. By continually modulating the LMCS at the detector end of the capillary column, signal-to-noise ratios of routine chromatograms can be readily increased by a factor of ten, thus enhancing chromatographic detection. Base widths of peaks, which are often about 2-3 s or more can be easily reduced to 0.3 s when the LMCS is employed in the detection enhancement mode, thus offering a simple avenue to improved peak height sensitivity in capillary gas chromatography.
    Additional Material: 7 Ill.
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  • 170
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    Journal of High Resolution Chromatography 21 (1998), S. 47-54 
    ISSN: 0935-6304
    Keywords: multidimensional gas chromatography ; comprehensive two-dimensional gas chromatography ; GC×GC ; characterization of petroleum samples ; quantitative analyses ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A software program was developed to enable the quantification of the complex 3D-data sets as produced by GC×GC. Using this software, it was demonstrated that the detectability limit of GC×GC in our study is 18 times better than that of ‘normal’ capillary gas chromatography (CGC). This enhancement is due to the signal increase produced by the thermal modulation effect. The relative standard deviation of 0.9% as measured on a test mixture was excellent. Furthermore, a comparison was made for the group-type separation of heavy gas oils between the hyphenation of LC and GC (LC-GC) and GC×GC. Although these separations are different in nature, the agreement of the results of both methods was very good. The results of GC×GC may even be more accurate, since, different from CGC, even in the most complex chromatograms the baseline in the second dimension chromatograms is always present.
    Additional Material: 5 Ill.
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  • 171
    ISSN: 0935-6304
    Keywords: Bornane congeners ; toxaphene compounds ; heart-cut multidimensional gas chromatography ; enantioselectivity ; chiral GC separation ; biological samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The enantiomeric ratios of the chlorinated bornanes, 2-exo, 5,5,9,9,10, 10-heptachlorobornane (B[20030]-(022)), 2-endo,3-exo,5-endo,6-exo,8, 8,10,10-octachlorobornane (B[12012]-(202), Parlar No. 26), 2-exo,3-endo,6-endo,8,9,10,10-heptachlorobornane (B[21001]-(112)), 2,2,5,5,9,9, 10,10-octachlorobornane (B[30030]-(022), Parlar No. 38), 2-endo,3-exo,5-endo6-exo,8,8,9,10,10-nonachlorobornane (B[12012]-(212), Parlar No. 50), and 2,2,5,5,8,9,9,10,10-nonachlorobornane (B[30030]-(122), Parlar No. 62) were determined in a hake liver (Merluccius merluccius) and in two whitebeaked dolphin blubber (Lagenorynchus albirostris) samples. The analysis was performed by heart-cut multidimensional gas chromatography using an electron capture detector (ECD). Ultra 2 (5%-phenyl-95%-methylsilicone) was used as stationary phase in the first column and enantioselectivity was obtained in the second column with a phase consisting of a mixture of OV-1701 and heptakis(2,3,6-O-tert- butyldimethylsilyl)-β-cyclodextrin (10 : 1). All reference standards were also tested on the enantioselective column alone. The comparison of the two systems showed that deviations of ±0.12 from the racemic enantiomer ratio can be observed for the single column due to co-eluting impurities which are present in the reference standards. In most of the heart-cut chromatograms of the biota samples about 15 peaks could be found, showing the importance of a multidimensional separation system for an interference-free quantification by ECD. In all biological samples a significant deviation from the racemic enantiomer ratio was found for B[30030]-(022) (Parlar No. 38) and for B[30030]-(122) (Parlar No. 62). This indicates that an enantioselective disposition of the congeners occurs. In addition, considerations are presented concerning the relationship between congener structure and enantiomeric disposition.
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  • 172
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    Journal of High Resolution Chromatography 21 (1998), S. 69-71 
    ISSN: 0935-6304
    Keywords: liquid chromatography ; chiral separations ; chiral stationary phase ; separation of enantiomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 173
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    Journal of High Resolution Chromatography 21 (1998), S. 3-10 
    ISSN: 0935-6304
    Keywords: Co-electroosmotic capillary electrophoresis ; high performance liquid chromatography ; phenolic lignin degradation compounds ; inorganic anions ; organic modifiers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Two methods are presented for the quantitative capillary electrophoretic (CE) determination of phenolic lignin degradation compounds as well as of inorganic anions and organic acids in Kraft black liquors. Important phenolic lignin degradation compounds can be rapidly separated by co-electroosmotic CE after acidification of the liquors and subsequent extraction of the compounds with chloroform. A capillary electrophoretic separation of phenolic compounds is performed by using a phosphate/borate electrolyte system and UV detection at 214 nm. In addition, a HPLC method using a gradient with water, methanol, and acetic acid is also developed. Inorganic ions which are of importance to the pulping process can be determined by simply diluting the black liquors after sampling and subsequent analysis with a chromate electrolyte system and indirect UV detection at 185 nm. In addition, the concentration of low molecular aliphatic carboxylic acids can be determined simultaneously within the same run. By method optimization it is possible to separate the anions within one minute and, at the same time, to increase the resolution of the solutes. The electrolyte systems for the CE separations were optimized by varying the pH value and by adding organic solvents. Short separation times are obtained by adding a polycationic EOF modifier (hexadimethrine bromide) to the electrolyte which reverses the electroosmotic flow. A migration of the anionic analytes in the same direction as the electroosmotic flow is thus established.
    Additional Material: 8 Ill.
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  • 174
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    Journal of High Resolution Chromatography 21 (1998), S. 81-86 
    ISSN: 0935-6304
    Keywords: Available niacin ; capillary electrophoresis ; total niacin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Available and total niacin content in lentils and faba beans have been analyzed by capillary electrophoresis (CE), and the results compared with those obtained by high performance liquid chromatography (HPLC). Acidic and enzymatic hydrolysis have been carried out for available niacin determination, and an alkaline extraction performed for total niacin. The extracts were subsequently purified using a strong anion exchanger resin. Precise conditions for purification had to be worked out for each one of the two analytical methods (HPLC and CE). The HPLC analysis for available and total niacin was carried out in an ion-pair reverse phase column with UV detection at 261 nm. For the CE separation, the following conditions were employed: a 20 mM sodium tetraborate; 15 mM sodium dodecyl sulfate and 20% isopropyl alcohol solution as separation buffer; 30 kV and 25 or 30°C. Separation was carried out in a 70 cm effective length × 75 μm i.d. fused-silica capillary using on-column UV detection at 254 nm. The results obtained by CE for lentils and faba beans were similar to those obtained by HPLC.
    Additional Material: 2 Ill.
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  • 175
    ISSN: 0935-6304
    Keywords: supercritical fluid chromatography ; experimental design optimization ; Diesel fuel ; group-type analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An optimization procedure is presented for group-type analysis of diesel fuel by supercritical fluid chromatography using packed silica column and a mixed mobile phase. A set of five responses, four values of resolution of a performance mixture and analysis time, was modeled using a Doehlert matrix for experimental design. Optimized experimental conditions for the five responses were obtained from a response surfaces optimization, taking into account various constraints on SF6 content in mobile phase and analysis time. The predicted and experimental resolutions were in good agreement for the different optimized conditions and one of them was selected to for application to a given diesel fuel for comparison with the results obtained by SFC using pure CO2 and by HPLC. The conditions found in this study provide an alternative method for the determination of mono-, di-, and polyaromatic compounds in middle distillates.
    Additional Material: 9 Ill.
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  • 176
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    Journal of High Resolution Chromatography 21 (1998), S. 309-314 
    ISSN: 0935-6304
    Keywords: Chlorophenols ; separation ; CZE ; pH ; organic modifiers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 177
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    Journal of High Resolution Chromatography 21 (1998), S. 298-302 
    ISSN: 0935-6304
    Keywords: Toxaphene ; thermal decomposition ; stationary phases ; gas chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Some toxaphene congeners are thermally unstable under commonly used gas chromatographic temperature conditions. The thermal stability of the 22 commercially available congeners has been studied at four different heating rates on four stationary phases Ultra 2 (5%-diphenyl-95%-dimethylpolysiloxane), a liquid crystalline phase (N,N′-bis(p-butoxy-benzylidene)-α,α′-bis-p-toluidine), Rtx-2330 (90%-biscyanopropyl-10%-phenylcyanopropyl-polysiloxane), and heptakis-(2,3,6-O-t-butyldimethylsilyl)-β-cyclodextrin (TBDMS-CD) diluted in OV-1701-OH. A substantial degradation of the congeners Parlar 39, 42, 50, 56, 58, and 62 could be observed on the cyanopropyl polysiloxane stationary phase. Furthermore, the applied temperature program and stationary phase had an influence on the signal areas. These factors are important for a quantitative analysis.
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  • 178
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    Journal of High Resolution Chromatography 21 (1998), S. 317-320 
    ISSN: 0935-6304
    Keywords: GC/MS analysis ; SIM mode ; UV stabilizers ; PET ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 179
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    Journal of High Resolution Chromatography 21 (1998), S. 323-331 
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis ; chiral separations ; chiral crown ethers ; 18-crown-6-tetracarboxylic acid ; synthesis ; applications ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An overview is presented of the applicability of the crown ether 18-crown-6-tetracarboxylic acid (18C6H4) as buffer additive in capillary electrophoresis (CE) for the separation of enantiomers. The chiral selector 18C6H4 is particularly useful for the separation of racemates having a primary amino function. Unfortunately, the crown ether is no longer commercially available. The synthesis and spectroscopic characterization are therefore described in detail. Moreover, a method is presented for the regeneration of the crown ether after CE application. Some new enantiomeric separations of amino acids i.e. NORLEU, ARG, GLU, m-TYR, and o-TYR are listed and the influence of the pH and temperature of the separation buffer is discussed. An intermediate in the synthetic pathway, namely 18-crown-6-tetracarboxamide, did not exhibit any enantioselectivity in CE.
    Additional Material: 6 Ill.
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  • 180
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    Journal of High Resolution Chromatography 21 (1998), S. 363-367 
    ISSN: 0935-6304
    Keywords: high temperature gas chromatography ; triacylglycerol ; lipids ; Jatropha multifida ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 181
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    Journal of High Resolution Chromatography 21 (1998), S. 303-307 
    ISSN: 0935-6304
    Keywords: gas chromatography ; modified silica gel ; gaseous standard mixtures ; FID calibration ; carbon monoxide and carbon dioxide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Quartz rods coated with a thin layer of chemically modified silica gel have been used for the generation of a two-component gaseous standard mixture containing carbon monoxide and carbon dioxide. A new method based on thermal decomposition of immobilized compounds chemically bonded to the surface of silica gel has been used in the generation process. The oxalic acid moiety bonded to the glycydoxypropylsilylated surface of silica gel underwent decarbonylation and decarboxylation at 300°C, yielding carbon monoxide and carbon dioxide. On-line connection of a thermal desorber with the GC/FID enabled calibration of the detector following the process of methanization of CO and CO2. The following amounts of CO and CO2 were generated per unit length of the rod: 15.1 × 10-8 Mol cm-1 (RSD = 5.71%) for CO and 34.2 × 10-8 Mol cm-1(RSD = 5.16%) for CO2.
    Additional Material: 4 Ill.
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  • 182
    ISSN: 0935-6304
    Keywords: Large-volume on-column injection ; gas chromatography ; infrared spectrometry ; microcontaminants ; solid-phase extraction ; open-split interface ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A large-volume on-column GC-cryotrapping-IR system was developed for injections of up to 100 μl of organic extracts. Considerable reduction of the solvent-and-water background and enhanced analyte detectability was achieved by using an open-split interface between the GC column and the IR detector and improving the leak-tightness of the system. The system was combined with solid-phase extraction to yield on-line SPE-GC-IR. With this set-up, sample volumes of only 20 ml sufficed to detect, and identify, microcontaminants in tap and surface water at the 0.1-1 μg/L level. Detection limits were on the order of 15 ng/L for tap water when using appropriate functional-group chromatograms. Or, in other words, SPE-GC-IR is a suitable technique for the screening of environmental water samples for functional groups, i.e. classes of compounds, of interest.
    Additional Material: 5 Ill.
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  • 183
    ISSN: 0935-6304
    Keywords: gas chromatography ; sorptive preconcentration ; air sampling ; VOCs ; nitro-PAH's ; PAHs ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper is concerned with the determination of volatile and semi-volatile organic components in air and gaseous (headspace) samples, focusing primarily on polar analytes. Samples were analyzed by preconcentration on different (ad)sorbents followed by thermal desorption and analysis by capillary gas chromatography. The performance of a cartridge filled with 100% polydimethylsiloxane (PDMS) particles was compared to that of adsorbents like Tenax TA and Carbotrap 300. Though the PDMS phase is non-polar it showed adequate retention for both polar and non-polar components. The blank runs of the PDMS trap were significantly better than those of most adsorbents and did not deteriorate, as was the case with all the conventional adsorbents investigated. With respect to trapping efficiencies, the PDMS phase performed better for most of the analytes under investigation compared to the adsorbents. For a range of analytes including triethylamine, butanone, diacetyl, nicotine, and acetic acid the PDMS phase performed exceptionally well whereas all adsorbents showed unsatisfactory performance. The packed PDMS traps were employed for the determination of organic acids, PAH's and nitro-PAH's in air and for the analysis of the headspace of cacao and hop.
    Additional Material: 9 Ill.
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  • 184
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 347-354 
    ISSN: 0935-6304
    Keywords: Fragrances ; chirality evaluation ; semi-automated multidimensional gas chromatography ; infrared spectrometry ; mass spectrometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The use of a semi-automated, multidimensional gas chromatography (MDGC) Fourier transform infrared (FT-IR) mass spectrometry (MS) system in the determination of components causing contact dermatitis has been investigated. Fragrances are widely used in cosmetic and household products and are the leading cause of contact dermatitis. Such products contain numerous components such as emulsifiers, thickeners, solubilizers, pigments, antioxidants, and many other compounds, which can make it difficult to isolate the compound of interest. MDGC has the capability for component analysis in such complex matrices. A semi-automated MDGC system, which consists of a commercial instrument modified in our laboratory to include two computer controlled valves and a single trap which is manually controlled was evaluated for analysis of irritants in a total of thirteen soaps. Using heartcutting techniques, components causing dermatitis were identified in eight of the thirteen soaps by examining both the infrared and mass spectra obtained and matching them with computer spectral libraries. Results from these analyses show that a baby soap and three other mild soaps were free of irritants. Irritants were identified in the remaining eight soaps. In addition, to demonstrate the versatility of the semi-automated system, the enantiomeric composition of a chiral irritant in two soaps also was determined.
    Additional Material: 8 Ill.
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  • 185
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 368-370 
    ISSN: 0935-6304
    Keywords: Solid-phase microextraction ; headspace analysis ; gas chromatography ; mass spectrometry ; volatile analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 186
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 575-576 
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography (CEC) ; chiral separations ; Vancomycin stationary phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 187
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 577-581 
    ISSN: 0935-6304
    Keywords: Volatiles ; Bromeliaceae ; Bromelia plumieri ; glycosidically bound volatiles ; aroma precursors ; glucoconjugates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 188
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 649-652 
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; NPD ; nicotine ; pharmaceutical analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The delivery of drugs through human skin using transdermal drug delivery (TDD) systems has become an established technology. A popular drug with that dosage form is nicotine for smoking cessation. A stability indicating method for the analysis of nicotine TDDs using gas chromatography (GC) with post-column effluent splitting to a flame ionization detector (FID) and a nitrogen-phosphorus detector (NPD) is described. FID detection gave reliable results with low day-to-day variability. The detector is relatively simple to operate. NPD detection offered enhanced sensitivity and specificity. The combination of both detectors resulted in a rugged method for content analysis with high sensitivity for detection of degradation products at low concentration levels. Despite a relatively simple sample preparation procedure no matrix interferences were observed.
    Additional Material: 3 Ill.
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  • 189
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 665-666 
    ISSN: 0935-6304
    Keywords: SPME; GC/MS ; Hg2+ and CH3Hg+ urine samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 190
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 653-657 
    ISSN: 0935-6304
    Keywords: capillary electrophoresis ; mass spectrometry ; CE-MS ; amphetamines ; Ecstasy ; biological fluids ; urine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Capillary electrophoresis (CE) was interfaced with a quadrupole mass spectrometer, using pneumatically-assisted electrospray ionization (ESI) in order to analyze Ecstasy and derivatives in urine. The influence of the sheath liquid composition, including the type and the percentage of the organic solvent, as well as the nature of the conductive acid modifier, were examined in order to find optimal coupling conditions. A fractional factorial design was also used to optimize the electrospray experimental parameters, such as the nebulizing gas pressure, the electrospray voltage, the drying gas flow rate, the drying gas temperature, the skimmer voltage, and the sheath liquid flow rate. The separation conditions were optimized in terms of temperature, electrolyte concentration, percentage of organic modifier, as well as capillary type. Finally, the optimal CE-ESI-MS conditions were applied to the analysis of Ecstasy and other related amphetamines in urine samples, following a liquid-liquid extraction procedure.
    Additional Material: 7 Ill.
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  • 191
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 671-673 
    ISSN: 0935-6304
    Keywords: gas chromatography ; monosaccharides ; pentafluorobenzylhydroxylamine ; electron capture detector ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 192
    ISSN: 0935-6304
    Keywords: Fluoroquinolone ; ASTED ; HPLC fluorescence ; sarafloxacin ; flumequine ; oxolinic acid ; chicken liver ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A recently introduced programmable fluorescence detector was compared with a single wavelength fluorescence detector for quantification of fluoroquinolone (FQ) antibacterial agents, which have widely varying spectral characteristics. The two detectors were connected in parallel to an HPLC system to test their performance characteristics. With single wavelength detection, two FQs, flumequine and oxolinic acid could be detected at an emission wavelength of 368 nm in a single chromatogram while a third FQ, sarafloxacin, was not observed at that wavelength. Similarly, when the detector was optimized for sarafloxacin emission at 440 nm, the other two compounds were undetected. In contrast, all three FQs were quantified at their individual maxima in a single run using the programmable fluorescence detection. The applicability of an HPLC - programmable fluorescence detector, in combination with on-line microdialysis, also was evaluated using chicken liver fortified at low ppb levels with the three FQs. After on-line microdialysis sample clean up, the resultant HPLC chromatograms were free of background interference enabling the programmable detector to optimize the quantitation of the three analytes in a single run. The limit of quantification (LOQ) determined for each FQ was 1.0 ppb and the limit of detection (LOD) was 0.2 ppb, an order lower in magnitude than was obtainable with single wavelength detection.
    Additional Material: 3 Ill.
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  • 193
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 267-281 
    ISSN: 0935-6304
    Keywords: Chemically bonded phases, CBPs ; liquid chromatography, HPLC ; preparation; surface characterization ; column evaluation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In order to increase chromatographic selectivity and to extend the analytical capability of reversed phase liquid chromatography (RP HPLC) many investigators have concentrated on the preparation of silica based column packings with chemically bonded phases (CBP). These phases have also been successfully used in sample preparation techniques, mainly in solid phase extraction (SPE). Although alkyl bonded phases (e.g., C2, C8, and C18) are the most widely used packings in RP HPLC and SPE, various specific applications require CBPs with polar functional groups (e.g., -NH2, -NO2, -CN, and/or -OH). The solution of problems with separation of complicated chiral compounds was attempted by applying stationary phases with chiral selectors (e.g., cyclodextrins, Pirkle phases, crown ethers, etc.). On the other hand, packings with pseudo-membrane or liquid crystal properties have been utilized for the separation of various substances of natural origin. Porous silica is commonly used as a support in the preparation of CBPs. Its physico-chemical characteristics, such as: type and structure of siliceous matrix, porosity, type and concentration of silanol groups, as well as surface purity, strongly influence the density and structure of chemically bonded phases. Recognition of these properties is helpful in optimizing separation processes based on RP HPLC elution and/or extraction of substances with polar character.
    Additional Material: 12 Ill.
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  • 194
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 287-290 
    ISSN: 0935-6304
    Keywords: DNA ; capillary electrophoresis ; sample injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Silver-coated capillaries were used for direct sample injection in multiplexed capillary electrophoresis. The absence of an additional electrode simplifies mechanical alignment, reduces contamination, and decreases the amount of sample needed. Capillaries were coated by a silver paint which is a suspension of silver particles in an organic solvent. To provide electrical contact, the upper part of the capillary and a platinum wire were wound together by a copper wire. Electrical resistance from the platinum wire to the tip of the capillary was small enough (7 ω to 50 ω) to inject large amounts of DNA samples. Electrokinetic injection from eight separate sample vials to eight capillaries was demonstrated for DNA sequencing by multiplexed capillary electrophoresis. Signal-to-noise ratio and resolution were good enough to call up to 350 base pairs.
    Additional Material: 3 Ill.
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  • 195
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; microplasma mass spectrometry ; radio frequency plasma ; element-selective detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Capillary gas chromatography was performed with mass spectrometric detection using a novel microplasma ion source for operation in an element-selective mode. The ion source was a 350 kHz radio frequency helium plasma, which was sustained inside the 4 cm end of a 0.32 mm i.d. fused silica capillary column, and located inside the high vacuum chamber of the quadrupole mass spectrometer. Due to the low volume of the ion source, a stable low pressure discharge was produced utilizing only the 2.25 mL min-1 of GC carrier gas (helium) for plasma support. Small amounts of oxygen (0.1-0.2% v/v) were added to the plasma gas in order to prevent carbon deposits and to enhance signal-to-noise ratios. Chlorine and bromine were selectively detected at the 5-20 pg s-1 level (S/N = 2), and both produced a response that was linear within 3 orders of magnitude.
    Additional Material: 3 Ill.
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  • 196
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 315-316 
    ISSN: 0935-6304
    Keywords: Tertiary amine ; ruthenium ; chemiluminescence ; photochemical oxidation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 197
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 355-362 
    ISSN: 0935-6304
    Keywords: Large volume injection ; solvent evaporation ; flooded zone ; solvent trapping ; on-column injection ; water analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Using a specially treated glass capillary, evaporation of the solvent during large volume injection into a precolumn was visually investigated in order to better understand the solvent trapping process. Using an early vapor exit, the process differs from the classical description of solvent trapping. First, there is a substantial pressure drop over the solvent-coated (“flooded”) precolumn, causing evaporation to take place not only at the rear edge, but also within the flooded zone or at its front end (which may result in almost complete loss of volatile solutes). Secondly, the evaporation rate increases as the liquid enters deeper into the precolumn, eventually turning partially concurrent evaporation into a fully concurrent evaporation with massive loss of volatiles. Thirdly, the capacity of the precolumn to retain liquid is substantially higher than observed in systems without early vapor exit
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 198
    ISSN: 0935-6304
    Keywords: Headspace solid-phase microextraction (HS/SPME) ; capillary gas chromatography ; volatile wine aroma compounds ; aromatic pattern ; chemometric classification ; HS/SPME standard addition method ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Headspace solid-phase microextraction (HS/SPME) was studied and optimized for the capillary gas chromatographic (CGC) analysis of wine aroma compounds. The results were compared with those obtained using the direct sampling mode (DI/SPME) and using liquid/liquid extraction with Kaltron. The aromatic patterns obtained by HS/SPME-CGC were applied to the chemometric classification of wine varieties. The HS/SPME-CGC standard additional method is an appropriate technique for the quantitative analysis of volatile wine aroma compounds.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 199
    ISSN: 0935-6304
    Keywords: Oil ; oil spill ; GC/MS ; GC/FID ; carbon isotope ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---During January and February 1996, a significant number of tarball/patty incidents occurred along the coasts of Vancouver Island, Washington, Oregon, and California. Samples of the tarballs were collected from the affected beaches and analyzed by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/flame ionization detector (GC/FID) using a tiered analytical approach developed for determining the origin of oils. Selected samples were further analyzed using a carbon isotopic technique. Also, the relative abundances of a large number of “source-specific marker” compounds, in particular alkylated series of polycyclic aromatic hydrocarbons within the same alkylation isomeric groups, were compared. Results of the analysis revealed that (1) California/Oregon samples were chemically similar and consistent with the same source. They were identified to be bunker type fuel; (2) The tarball samples collected from British Columbia and Ocean Shores, Washington were chemically similar and consistent with the same source (also bunker type fuel). They were found to be similar to but may have a source different than the California/Oregon samples; (3) The source of the tarball/patty samples was neither Alaska North Slope oil nor California Monterrey Miocene oil; (4) The spilled oil samples have been highly weathered since release, and the California samples were more heavily weathered than the British Columbia samples.
    Additional Material: 7 Ill.
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  • 200
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 407-410 
    ISSN: 0935-6304
    Keywords: Capillary GLC ; nitrous oxide as carrier gas ; carrier gas correlation of retention factors ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---On use of nitrous oxide as carrier gas the retention factors of the chromatographed compounds decrease linearly with increasing average column pressure. Other retention characteristics (relative retention, retention index) change linearly. This effect was demonstrated by using a capillary column coated with nonpolar polydimethylsiloxane phase SE-30. As shown for capillary GLC the linear correlation is valid for the same column:ki(G1,P1) = A ki(G2, P2) + B, where ki(G1, P1) and ki(G2,P2) are the retention factors of compound i at average column pressures P1 and P2 when using carrier gases G1 and G2, respectively; A and B are coefficients.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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