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  • 1995-1999  (659)
  • 1996  (659)
  • Atomic, Molecular and Optical Physics  (433)
  • Analytical Chemistry and Spectroscopy  (226)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 111-116 
    ISSN: 0935-6304
    Keywords: Polynuclear aromatic hydrocarbons ; Liquid chromatography ; Alcohols ; Micelles ; Enviromental samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for the separation of polycyclic aromatic hydrocarbons (PAHs) by high-performance liquid chromatography using a hybrid micellar mobile phase is described. The detection of PAHs was carried out using the fluorescence method with programmable excitation and emission wavelength. The method is applied to the analysis of several environmental samples (sea water, sediments, limpets, sea worms) and several of these compounds are quantitated at concentration below 70 ng L-1(kg-1) in the original samples.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 99-104 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Micellear electrokinetic chromatography ; Organic modifiers ; Naphthalene sulfonates ; Surface water ; Thermostatting ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The production and use of naphthalene sulfonates can easily cause pollution of surface and other types of waters. In the present study, capillary electrophoresis in combination with UV absorption detection was used to separate 21 amino- and hydroxy-substituted naphthalene sulfonates which included multiple isomeric compounds. The influence of various parameters such as pH (which turned out to be extremely important), temperature of the surrounding air flow, and the use of buffer additives (micelles, cyclodextrins, organic modifiers) was studied. Complete separation of all analytes including the isomers, was achieved in two runs with a 50 mM boric acid/borate buffer, containing either 100 mM sodium dodecylsulfonate or 15% acetonitrile. The limits of detection obtained for the individual compounds typically were 20μgI-1. River water samples spiked at this concentration level could be analysed using a simple three-step sample clean-up procedure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 403-408 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Cryogenic trapping ; Capillary ; Focusing ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cryogenic trapping of solutes leads to narrowing of the chromatographic band. By placing the trap at the end of a capillary column, it is possible to study the effectiveness of the trap in terms of producing a sharpened elution profile. The trap may be heated by supplementary heating, but here convective heating from the GC oven is employed simply by turning off the cryogenic coolant. It is estimated that it takes about 50 s for the trap to heat up sufficiently to allow trapped solute to be remobilized, although this depends upon the oven temperature and thermal mass of the trap. It can also be shown that the more volatile solutes mobilize faster from the trap in this particular mode of operation. The recovery of trapped components shows that there is essentially quantitative trapping, and the solutes are trapped just at the leading edge of the trap.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 409-412 
    ISSN: 0935-6304
    Keywords: Micellar electrokinetic chromatography ; Rhei Rhizoma ; Scutellariae Radix ; Coptidis Rhizoma ; Bioactive constituents determination ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A capillary electrophoretic method for simultaneous determination of six bioactive ingredients (berberine, palmatine, baicalin, sennoside B, emodin, and sennoside A) in the Chinse herbal formula San-huang-hsieh-hsin-tang was established. A carrier composed of aqueous buffer solution (50 mM sodium cholate, 15 mM sodium dihydrogen phosphate, and 4.25 mM sodium borate)-acetonitrile (3:2) was found to be the most suitable electrolyte for this separation. Contents of these constituents in a non-pretreated methanol-water extract of San-huang-hsieh-hsin-tang sample could be easily determined within 20 min. The effects of borate, cholate, and organic modifier (acetonitrile) concentration of the carrier on the migration behavior of the solutes were also studied.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 418-418 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 485-491 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Qualitative analysis ; Quantitative analysis ; Retention indices ; Retention times ; Solvent effect ; Sulfur Chemiluminescence Detection (SCD) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas chromatrography (GC) with sulfur chemiluminescence detection (SCD) is an outstanding combination for selectively determining trace concentrations of sulfur compounds in hydrocarbon samples. GC peaks can be identified by retention times when reproducible, automated injection techniques are used. However, as described in this work, analysts should be on the look out for retention shifting due to solvent effects from sample components. Three examples of retention shifting are presented: (1) thiophene by benzene; (2) methylthiophenes by toluene; and (3) dibenzothiophene by gas oil. Depending on samples and analysis conditions, retention shifts from a few hundredths to 1.5 min have been observed. Such retention shifts are likely to cause errors in peak identifications. Therefore, when using SCD, simultaneous FID monitoring is recommended as an aid in evaluating chromatograms for possible retention shifting due to solvent effects.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 497-502 
    ISSN: 0935-6304
    Keywords: α-Monoacetotriacylglycerides ; Celastraceae ; Fatty acids ; GLC ; GLC-(NCI)MS ; Maytenus seed oils ; OV-225-OH, OH-terminated ; SOP-50, methoxy-terminated ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The seed oils of three Maytenus species have been examined by high temperature GLC using SOP-50 (methoxy-terminated) and OV-225-OH (OH-terminated) glasscapillary columns. The main compounds (71-76%) could be identified as α-mono-acetotriacylglycerols by a combination of high temperature GLC-MS in negative chemical ionization mode with a CH4/N2O mixture as reactant gas and other spectroscopical methods (infrared, 1H- and 13C-nuclear magnetic resonance spectroscopy). The OV-225-OH phase demonstrated better separation properties that the SOP-50 phase for this substance class and up to eight species of α-monoacetotriacylglycerols could be separated. The content of usual triacyclglycerols was below 1%. The results of the analysis of the individual fatty acids as their methyl esters by GC and GC-MS are also presented.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 521-526 
    ISSN: 0935-6304
    Keywords: LSS model ; Whey proteins ; HIC of proteins ; Circular dichroism ; 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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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 527-529 
    ISSN: 0935-6304
    Keywords: High pressure gas chromatography ; Stationary phases ; Hydrocarbons ; 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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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 11
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Enantiomeric separations ; Acidic compounds ; Neutral β-cyclodextrins ; Sulfobutyl ether β-cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High resolution could be achieved for the enantiomers of acidic drugs, namely, sulindac, fenoprofen, ketoprofen, warfarin, and hexobarbital, in a buffer of pH 3 by the simultaneous addition of uncharged and charged β-cyclodextrin derivatives. The interaction of the analytes with the anionic sulfobutyl ether β-cyclodextrin provides the analytes with an adequate electrophoretic mobility whereas the interaction with various neutral β-cyclodextrins generates high enantioselectivity. Five neutral cyclodextrins, the native β-cyclodextrin, as well as methyl-, dimethyl-, trimethyl- and hydroxypropyl-β-cyclodextrin, were tested to enhance the enantioselectivity of the electrophoretic system. High resolution values and the shortest analysis times for the five drugs tested were achieved in a buffer made of 100 mM phosphoric acid adjusted to pH 3 with triethanolamine and containing dimethyl- or trimethyl-β-cyclodextrin in addition to sulfobutyl ether β-cyclodextrin.
    Additional Material: 5 Ill.
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  • 12
    ISSN: 0935-6304
    Keywords: Chlorobiphenyl congeners ; Aroclors ; DB-XLB phase ; HP-5/HT-5 serial coupled phases ; GC-ECD ; GC-MS-SIM ; GC-Ion Trap MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three HRGC systems (1: 30m DB-XLB capillary with MS-SIM detection; 2: 60m DB-XLB capillary with full-scan, ion-trap MS detection; and 3: Parallel dual-column DB-17 and series-coupled HP5/HT5 with ECD detection) were used to completely characterize multiple lots of 8 different-numbered Aroclor mixtures by quantitative calibration against 9 solutions containing primary standards of all 209 PCB congeners. Despite lower absolute sensitivity and more Aroclor congener coelutions than the dual-column ECD system, the MS systems enabled measurement of more congeners per Aroclor since their greater linear response range did not require dilution of samples and standards. Pairs of different lots of Aroclors 1248 and 1254 displayed markedly different proportions of congeners, and the 1254 pair displayed strong differences in the extent of ortho-chlorine substitution. The tables of congener weight percent distributions among Aroclors are more comprehensive and quantitatively precise than those of prior publications. However, the limitations of single-level calibration precluded measurement of all congeners to the ±10% accuracy desirable for establishing these Aroclors as secondary standards for comprehensive, quantitative congener-specific PCB analysis.
    Additional Material: 3 Ill.
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  • 13
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Mass spectrometry ; Electrospray ionization ; Fourier transform ion cyclotron ; Resonance ; Biomolecule analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe the current state of the on-line combination of capillary electrophoresis (CE) electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS), and discuss aspects of the FTICR technique relevant to its use as a detection scheme for on-line separations. Aspects including sensitivity, mass resolution, duty cycle, and tandem mass spectrometric capabilities are discussed in the context of online separations with examples from the authors' laboratory.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 0935-6304
    Keywords: HPLC of phenols ; Dianthus caryophyllus ; Carnation vascular wilt ; Fusarium oxysporum f. sp. dianthi ; Root phenolic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 43-48 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Mass spectrometry ; Wax esters ; Festuca arundinacea ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ester portion of epicuticular waxes of tall fescue (Festuca arundinacea Schreb.) is composed of mixtures of homologous series of fatty acids esterfied with fatty alcohols. GC analyses of natural esters gave rise to the separation of several compounds of different chain length. To identify and quantify individual components in the mixture, GC/MS analyses were carried out, and the mass spectra of each peak were recorded and analyzed for characteristic ions. This approach permitted a comparison with data obtained from classical methods using GC analysis of acid and alcohol moieties obtained by hydrolysis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 0935-6304
    Keywords: Optimization of GC conditions ; Sugar analysis ; Acid analysis ; Chlorogenic acid ; Raffinose ; Pectin decomposition products ; Galacturonic acid ; Arabinose ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Our GC-MS method for the simultaneous quantitation of sugars and acids as their silyl(oxime) derivatives, from one solution by one injection, has been extended to the reproducible determination of high molecular weight compounds sensitive to decomposition yet requiring a high evaporation temperature (e.g. chlorogenic acid and rffinose) and for the quantitation of the decomposition products of pectin (i.e., for the determination of galacturonic acid at low ng levels in the presence of a 10-100 fold excess of glucose eluting just before the acid). The optimized GC procedure has been used for quantitation of the sugar and acid (including chlorogenic acid) composition of potato samples, and for the determination of the increasing amount of the decomposition products of pectin substances in apple pulp after different storage times.
    Additional Material: 1 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 66-66 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 180-182 
    ISSN: 0935-6304
    Keywords: trans-Fatty acids ; Semi-industrial frying ; Capillary GC ; 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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  • 20
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 183-188 
    ISSN: 0935-6304
    Keywords: Chelating agents ; Complexation ; Capillary zone electrophoresis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A capillary electrophoretic method has been developed which achieves rapid quantitative separation and determination of ethylenediaminetetraacetic acid, N-(2-hydroxyethyl)ethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminediacetic acid, and nitrilotriacetic acid in Hanford tank waste simulant (TWS). Direct UV detection of Cu2+/chelator complexes is used to achieve enhanced sensitivity. The qualitative and quantitative reliability of the method and the quality of separations, as given by efficiency and resolution, is presented. In addition, the limits of detection and linearity of detector response with concentration are given for each chelator. The selection of Cu as the UV-absorbing species over other transition metals present in the waste is discussed.
    Additional Material: 5 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 49-53 
    ISSN: 0935-6304
    Keywords: Polycyclic aromatic sulfur heterocycles ; Crude oil ; Oil maturity ; Fingerprinting ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is presented for the identification and quantification of C2-substituted benzothiophenes in crude oil. The method will enable analysis of the pattern of these compounds, for example as a basis for differentiating crude oils from one another (fingerprinting) and for investigation of their suitability as indicators of oil maturity. Here results are reported for five crudes from Iraq, Venezuela, Saudi Arabia, the former Soviet Union, and the North Sea. The aromatic fraction of the crudes was oxidized and the dioxides of the heterocycles separated according to the number of carbon atoms in the side chains. The final separation was by capillary GC with atomic emission or flame ionization detection. A fluorinated analog was synthesized and used as internal standard. The concentrations of 2,3-, 2,4-, 2,7-, and 3,7-dimethylbenzothiophene ranged between 11 and 272 ppm. Three other dimethylated benzothiophenes present in lower amounts were also identified.
    Additional Material: 4 Ill.
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  • 22
    ISSN: 0935-6304
    Keywords: Capillary Supercritical Fluid Chromatography ; Mass Spectrometry ; SFC-MS ; On-line combination ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An interface for coupling supercritical fluid chromatography to a magnetic sector mass spectrometer was developed and evaluated. The interface is based on direct introduction of the mobile phase, carbon dioxide, into the ion-source of the mass spectrometer. The SFC-MS system was optimized with respect to the signal-to-noise ratio. Under optimized conditions, the estimated detection limit for n-pentadecane is approximately 30 ppm. Spectra obtained in the electron-impact ionization mode show a very good similarity with library spectra. The performance of the SFC-MS system was evaluated by the analysis of a number of test mixtures. A sample containing several low molecular mass, thermally unstable compounds, which could neither be analyzed by GC-MS nor by LC-MS, was analyzed. Also for the analysis of high molecular mass compounds, the coupled system showed a good performance.
    Additional Material: 9 Ill.
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  • 23
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 37-42 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The headspace gas in static headspace gas chromatography contains mostly saturated water vapor. In the case of the cryofocusing enrichment technique this may cause baseline distortion in the early part of the chromatogram or may even lead to ice-plugging of the capillary column. A water-trap is described in which the water vapor is removed from the headspace gas before entering the cryo-trap. The water trap is packed with lithium chloride on a porous support and is regenerated after each analysis by heating under backflush conditions. It therefore can be used for automatic operation. Data are given for the precision and accuracy, and some practical examples, for environmental and flavor analysis are shown.
    Additional Material: 6 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 59-61 
    ISSN: 0935-6304
    Keywords: Steam chromatography ; Salt-water stationary phases ; Retention of alcohols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 25
    ISSN: 0935-6304
    Keywords: Gas Chromatography ; Ion-Trap Mass Spectrometry ; Pesticide residue analysis ; Eggs ; Ardea cinera ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 26
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 65-65 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 27
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. iii 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 28
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 80-84 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Specific detectors ; ECD/FPD response ratios ; Retention indices ; Identification on real samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A previous paper reported the possibility of using the ratio between the responses of two different specific detectors to a single compound (detector response ratio, DRR) as an identification criterion for that compound, in combination with its retention index.This article gives some applications of DRR in the identification of some pesticides in four different fruits (apples, apricots, strawberries, and peaches) in a range varying from 0.02 to 1.3 ppm, by means of their ECD/FPD DRRs. After clean-up GC analyses were performed on a single column with dual parallel detection; a personal computer system was used for data analysis.
    Additional Material: 4 Ill.
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  • 29
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 91-94 
    ISSN: 0935-6304
    Keywords: Chiral selector anchored to polysiloxane ; Chiral phase capillary GC ; Immobilization ; Thermal treatment ; High enantioselectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chiral selector L-t-leucine-t-butylamide has been anchored to a polysiloxane by nucleophilic displacement of 2,2,2-trifluoroethyl ester-functionalized block polysiloxanes with L-t-leucine-t-butylamide. Attempts were made to immobilize the chiral polysiloxanes inside the capillaries by thermal treatment at 300°C for 30-90 min. The polysiloxanes were found to be more resistant than Chirasil-Val to the racemization caused by such high temperature treatment. Capillary columns coated with this type of immobilized polysiloxane have shown very high enantioselectivity and thermal stability.
    Additional Material: 3 Ill.
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  • 30
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 284-284 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 31
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 277-283 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Coupled columns ; Four factor optimization ; Simplex method ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optimization of a gas chromatographic system with two capillary columns coupled in series in a single oven for the linear temperature programmed separation of a mixture of C1—C10 hydrocarbons has been carried out using the simplex optimization method. The following four selectivity parameters were optimized: the initial temperature of the oven; the initial hold time; the temperature programmed rate; and the pressure at the mid-point of the system. The optimization procedure was monitored by the Cp criterion.
    Additional Material: 3 Ill.
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  • 32
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis-mass spectrometry ; Membrane preconcentration ; Capillary electrophoresis ; Sulfonated membrane ; Polar drug metabolites ; Toxic oil syndrome ; Eosinophilia-myalgia syndrome ; 3-Phenylamino-1,2-propanediol ; 3-Phenylamino-L-alanine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 33
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. VII 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 34
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 298-300 
    ISSN: 0935-6304
    Keywords: Dynamic head space ; Coffee berry ; Identification ; Hypothenemus hampei ; Plant-insect relationship ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 35
    ISSN: 0935-6304
    Keywords: Capillary GC ; Drug screening ; Retention index ; Reporting ; Mean list length ; Blood analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dual-column gas chromatographic retention index method was evaluated for the toxicological screening for basic drugs in autopsy blood samples. The dual-column approach with DB-5 and DB-1701 capillary columns doubles the Identification Power of the corresponding single column methods. The long-term intralaboratory variation of the dialkylfluoroaniline series based retention indices of drugs in blood ranged from 0.03% to 0.2% which was generally better than that obtained using the relative retention time. Novel software is described for the processing and reporting of the dual-column chromatographic data in analytically useful form. Besides retention data, the response factors served as an additional identification factor.
    Additional Material: 4 Ill.
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  • 36
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 327-332 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Separation performance ; Fourier analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple procedure is presented for determining separation performance of HRGC analysis of multicomponent mixtures. The procedure is based on the computation of Autocovariance Function (EACVF) from the digitized experimental chromatogram. Graphic inspection of the EACVF plot permits easy computation of the width value of the single component peak, σ; from the EACVF value at t=O the number of component in the mixture, m, can be simply derived. From these two basic quantities all the other chromatographic performance attributes can be calculated. The consistency of the procedure is tested for different chromatograms and compared with the more complex EACVF fitting method. Several features of the multicomponent chromatogram, overloading effects included, are directly detected.
    Additional Material: 4 Ill.
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  • 37
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 339-344 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Trace gas analysis ; Multichannel thick film silicone rubber traps ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Established standard methods for analyzing semi-volatile pollutants by capillary gas chromatography are cumbersome, time-consuming, and expensive. With the longer term aim of replacing the sample preparation procedures with convenient concertrating and thermal desorption steps, thick film silicone rubber traps were constructed in a novel multi-channel configuration. Tests were performed to determine breakthrough volumes and thermal desorption characteristics for total transfer of the trap contents to a capillary column. Initial results are very promising.
    Additional Material: 6 Ill.
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  • 38
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 333-338 
    ISSN: 0935-6304
    Keywords: Adsorptive enrichment/thermal desorption ; Microtrap ; VOC and PVOC analysis ; Humid air sample analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An instrument has been developed and tested for the continuous measurement of volatile organic compounds (VOC) in air. The system consists of a gas chromatograph equipped with a dedicated sampling device that allows the sample to be transferred to a cooled microtrap via sampling loops (10, 100, 250 ml) or via a direct pump transfer to the trap. The microtrap is placed in the chromatographic oven just below a modified split-splitless injector, allowing direct liquid injection for calibration of the system; the injector is in communication with the sampling valve equipped with the loop and the sampling pump. The system allows 24-hour sampling and analysis of a large number of VOC (up to 25 individual hydrocarbons ranging from C2—C9) and also polar volatile organic compounds PVOC. Thanks to the particular trap geometry, a minimum consumption of liquid nitrogen (between 150—300 ml) is needed for each analytical run and no water managing system is normally required for humid air samples.
    Additional Material: 5 Ill.
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  • 39
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 353-358 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Gas chromatography-mass spectrometry ; Essential oil analysis ; Ylang-ylang oil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Steam distillation (SD), simultaneous distillation-solvent extraction (SDE), and supercritical (CO2) extraction (SFE) were used to isolate volatile secondary metabolites from fresh, totally mature flowers of Colombian ylang-ylang (Cananga odorata). The various extracts were analyzed by capillary chromatography (DB-1, DBWAX, 60 m columns) using FID, NPD or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard substances were employed for compound identification. 51, 70, and 73 compounds at concentrations above 100 ppb were detected in the SD, SDE, and SFE extracts, respectively. The main constituents of these extracts were linalool (20.7, 28.0, and 16.5%), germacrene-D (10.1, 3.1, and 20.3%) benzyl benzoate (14.1, 2.9, and 3.9%), benzyl acetate (9.6, 17.0, and 6.2%), caryophyllene (3.1, 2.9, and 3.9%), and p-methylanisole (6.8, 6.1, and 2.7%). 85% of the composition of SDE extracts was represented by oxygenated compounds. Heavy hydrocarbons (Cn 〉20) and fatty acids were found only in the SFE extracts, which also had a higher content of nitrogenated compounds (phenylacetonitrile, 4-methylbenzaldoxime, indole, 2-phenyl-nitroethane, and methyl anthranilate) and sesquiterpenes (43% vs 19.5% in SD and 8.1% in SDE) and 1.5 - 2 times lower concentration of monoterpenes and light oxygenated compounds than the SD (49.7%) and SDE (64.5%) extracts.
    Additional Material: 4 Ill.
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  • 40
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 359-361 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Atomic emission detection ; Triclosan ; Dental plaque ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A validated gas chromatographic method for the determination of triclosan in human dental plaque is described. Based on plaque sample weights of 10 mg, the limit of detection (2 × S/N) is 0.5 μg/g. The method is linear (r = 0.9986) from the limit of detection to 50 μg/g. Recoveries from placebos spiked with 2.0, 25, and 50 μg/g of triclosan were 105.6%±7.5%, 107.2%±3.1%, and 99.1%±1.1%, respectively (n = 3 at each level). Twenty replicate preparations and analyses of a homogenized sample, conducted by two operators over the course of 4 days, showed agreement to within 9% RSD. Analyses of dental plaque collected from patients after brushing with dental cream containing triclosan, shows triclosan to be retained in dental plaque at concentrations above the minimum inhibitory concentration (1 μg/g) after 12 h.
    Additional Material: 1 Ill.
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  • 41
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 42
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    Journal of High Resolution Chromatography 19 (1996), S. 371-371 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 43
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 377-382 
    ISSN: 0935-6304
    Keywords: Capillary chromatography ; Boiling points prediction ; Identification ; Chlorobenzenes ; Phenols ; Programmed temperature ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quantitative correlations between physicochemical parameters and structure of various solutes and their gas chromatographic behavior were investigated in order to predict the retention values. The identification of unknown samples in gas chromatographic routine analysis of environmental samples is enhanced by the use of these correlations in conjuction with other chromatographic methods and with mass spectrometry. The boiling points of many compounds are easily found in literature and therefore their correlation with retention values obtained in isothermal or programmed temperature analysis permit restriction of the choice of names of unknown compound to within a narrow range. The correlation between the boiling points and the retention times of chloro- and bromo-benzenes and of some chloro- and nitro- substituted phenols was investigated on non-polar capillary columns and permitted the tentative identification of many compounds belonging to these homologous series.
    Additional Material: 3 Ill.
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  • 44
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; FID, O-FID, and MS detection ; Glycol ethers and glycol ether acetates ; Heptafluorobutyryl derivatives ; Mass spectra ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Twelve compounds, commonly used as industrial solvents and belonging to the chemical class of glycol ethers and glycol ether acetates, were investigated. Several analytical conditions, applied to single or connected capillary columns of different length and polarity coating and connected to FID, O-FID and MS detection systems, were assayed. Tests on heptafluorobutyryl derivatives were also attempted to improve the analytical sensitivity. The aims were to establish gas chromatographic methods suitable for analysis of reference standard compounds and to verify their applicability to biological matrix analysis for pharmacokinetic and toxicological studies, since these chemicals have been shown to be hazardous in laboratory animals and are presumed to be dangerous in man.
    Additional Material: 6 Ill.
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  • 45
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    Journal of High Resolution Chromatography 19 (1996), S. 444-448 
    ISSN: 0935-6304
    Keywords: LC-GC coupling ; Loop-type interface ; Alcohols ; Sterols ; Olive oil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modified loop-type interface is decribed which uses two 6-way valves and concurrent eluent evaporation to perform an on-line transfer and simultaneous gas chromatographic analysis of two different fractions pre-separated by liquid chromatography. The interface is used to simultaneously analyze aliphatic alcohols and sterols present in olive oil. LC pre-separation is carried out using a normal phase column (20 cm × 0.21 cm i.d.) and hexane-isopropanol (99:1) as a mobile phase at a flow of 0.2 ml/min; for the GC analysis a 5 % phenyl, 95 % dimethyl siloxane (25 m × 0.32 mm i.d., 0.4 μm film thickness) column is used.
    Additional Material: 4 Ill.
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  • 46
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    Journal of High Resolution Chromatography 19 (1996), S. 462-462 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 47
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    Journal of High Resolution Chromatography 19 (1996), S. 463-463 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 48
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    Journal of High Resolution Chromatography 19 (1996), S. 449-456 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography (SFC) ; Packed columns ; Pressure drop ; Selectivity ; Resolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of pressure drop on retention, selectivity, plate height and resolution was investigated systematically in packed supercritical fluid chromatography (SFC) using pure carbon dioxide as the mobile phase. Numerical methods developed previously which enabled the prediction of pressure gradients, diffusivities, capacity factors, plate heights and resolutions along the length of the column were used for the model calculations. The effects of inlet pressure and supercritical fluid flow rate on selectivity and resolution are studied. In packed column SFC with pure carbon dioxide as the mobile phase, the pressure drop can have a significant effect on resolution. The flow rate is shown to have a larger effect than generally realized. The calculated data are shown to be in good agreement with the experimental results. Finally, the variation of the chromatographic parameters along a 5.5 meter long model SFC column is illustrated. The possibilities and limitations of using long packed columns in SFC are discussed. It is demonstrated that long columns with large plate numbers do not necessarily yield better separations.
    Additional Material: 7 Ill.
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  • 49
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    Journal of High Resolution Chromatography 19 (1996), S. 464-464 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 50
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Purge and trap extraction ; 1,2,4-TCB ; Environmental analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High resolution gas chromatography (HRGC) coupled to a “purge and trap” extraction-injection technique is described as a method of determining 1,2,4-trichlorobenzene in water at levels as low as parts-per-trillion (ppt). In order to investigate the interference from other volatile organic compounds (VOCs) several detection systems were compared: flame ionization, electron capture, and mass spectrometry-multiple ion detection. Concentrations ranging from 15 to 600 ng/L were analyzed in 20 ml standard aqueous solutions. The mean accuracy of the method varied from 89 to 103%, and its mean precision varied from ± 0.85 to ± 7.5 % for all detectors. The detection limits were 20 ng/L for FID, 2 ng/L for ECD and 0.5 ng/L for MID-MS detectors. The procedure was successfully applied to the analysis of industrial waste waters. The necessity of an appropriate internal standard to improve the quantitative determination and to determine possible losses or degradation of 1,2,4-trichlorobenzene during handling or storage is discussed.
    Additional Material: 5 Ill.
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  • 51
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    Journal of High Resolution Chromatography 19 (1996), S. 469-471 
    ISSN: 0935-6304
    Keywords: Microextration ; GC/MS ; Chlorobenzenes ; Water samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 52
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    Journal of High Resolution Chromatography 19 (1996), S. 465-469 
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction (SFE) ; Beef ; Anabolic steroids, synthetic ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 53
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    Journal of High Resolution Chromatography 19 (1996), S. vii 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 54
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    Journal of High Resolution Chromatography 19 (1996), S. 478-480 
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis ; Chiral separation ; Cyclodextrins ; Methoxamine ; Lobeline ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 55
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    Journal of High Resolution Chromatography 19 (1996), S. 492-496 
    ISSN: 0935-6304
    Keywords: High - speed capillary GC ; Carbon dioxide cryotrap ; Deactivated metal tubing ; Thermal decomposition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ten different metal tubings were investigated for thermal decomposition of analytes when used as the trap tube in a cryotrap/thermodesorption inlet system. No noticeable sample decomposition of hydrocarbons, chlorinated hydrocarbons and a brominated hydrocarbon was observed for six of the tubings with hydrogen as the carrier gas. This observation may be partly attributed to the developed deactivation techniques that produce inert metal tubings that are being widely adopted by many column manufacturers, the different trap materials used in comparison to previous studies and the decreased sample residence time in the hot trap tube. A cryotrap using carbon dioxide was constructed and tested as a alternative to the previously used liquid nitrogen based systems. This cryotrap was able to trap compounds with a boiling point of 80°C.
    Additional Material: 5 Ill.
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  • 56
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    Journal of High Resolution Chromatography 19 (1996), S. 511-514 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Enantiomer separation ; Amino acids ; N-Alkyloxycarbonyl alkylamide derivatives ; Nucleophilic substitution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of amino acids were first converted into N-alkyloxycarbonyl 2,2,2-trifluoroethyl esters, and then into N-alkyloxycarbonyl alkylamides by nucleophilic substitution of the ester group with amines. The first reaction proceeds instantaneously, while the second substitution occurs smoothly with n-propylamine and isobutylamine. The final derivatives were produced for separation on a capillary column coated with Chirasil-Val by GC. Pro, which is difficult to separate completely as its N-perfluoroacyl alkyl ester derivative, showed complete separation of the enantiomeric pair. All amino acids examined in this study showed an increased separation factor.
    Additional Material: 3 Ill.
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  • 57
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    Journal of High Resolution Chromatography 19 (1996), S. 530-533 
    ISSN: 0935-6304
    Keywords: High-performance liquid chromatography ; Paeoniae Radix ; Peony constituent separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 58
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    Journal of High Resolution Chromatography 19 (1996), S. 543-548 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; High temperature ; Dead time ; Constants of the n-alkane retention time curve ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In gas liquid chromatography, the column dead time and the constants of the n-alkane retention time curve are calculated by the multiparametric least-squares regression iterative method at high temperature between 180 and 270°C. The method was applied to two types of columns. The first group includes eight packed columns (seven OV polymethylphenylsiloxane and Apolane-87), while the second includes five glass capillary columns (four methylsilicone with different film thicknesses and Apolane-87). The calculated tM and b values were compared with those obtained by Guardino's, Grobler's, and Kaiser's methods. The influences of coating thickness and temperature thereon were investigated.
    Additional Material: 4 Tab.
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  • 59
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    Journal of High Resolution Chromatography 19 (1996), S. 569-570 
    ISSN: 0935-6304
    Keywords: Microbore SFC ; Chiral separation ; 3,5-Dimethylphenyl carbamate derivative of cellulose ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 60
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    Journal of High Resolution Chromatography 19 (1996), S. 559-563 
    ISSN: 0935-6304
    Keywords: Pesticide residue analysis ; Solid phase extraction ; Ground water ; Surface water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A critical study of a solid phase extraction method using C18 SPE columns for the determination of 23 halogenated pesticides is presented. Type of sorbent, sorbent mass, flow rate in the extraction process, sample concentration of the different compounds, sample volume, pH, ionic strength and type of water were evaluated. Recoveries of pesticides under study yield a linear relationship, except for conazole fungicides and captan. Losses can be expected for heptachlor, aldrin, and captan. Sample volume and flow rate of extraction affect recoveries. Matrix effects from surface and groundwaters were observed. Recoveries for vinelozolin and dieldrin from groundwater were lower than those obtained from nanopure water. In river water losses of these compounds are higher. Captan and penconazole were not present and high losses were obtained for trifluralin, α-BHC, γ-BHC, tri-allate and chlorpyriphos. Impurities arising from the sorbent materials of cartridges have been detected.
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  • 61
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    Journal of High Resolution Chromatography 19 (1996), S. 549-558 
    ISSN: 0935-6304
    Keywords: Size exclusion chromatography ; Petroleum waxes ; Flame ionization detector ; Refractive index detector ; Molecular weight distribution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular weight distribution of solid petroleum waxes is a key parameter for the general characterization of these materials. Particular interest concerns extremely large components, typically present in oil distillation residua, and solid deposits found in oil production facilities. Molecular weight distributions of oil waxes were determined in this work by high temperature size exclusion chromatography. Separations were carried out with two different eluents, namely toluene and ortho-dichlorobenzene and two detection systems, these being a differential refractive index and a flame ionization detector. Toluene proved to be the best choice when combined with flame ionization detection. Better uniformity of response was the greatest advantage achieved by this approach. The experimental set up permitted analysis of samples containing molecules with up to 138 carbon atoms. Burning properties of very large molecules, isomerism affecting calibration, and signal asymmetry when flame ionization detection was adopted were three issues still requiring additional efforts to understand and to improve analysis accuracy.
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  • 62
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    Journal of High Resolution Chromatography 19 (1996), S. 577-580 
    ISSN: 0935-6304
    Keywords: Phenolic compounds ; Solid phase extraction ; Coal gasification ; GC/MS ; XAD-4 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 63
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    Journal of High Resolution Chromatography 19 (1996), S. 588-590 
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; Water samples ; Polycyclic aromatic hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 64
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    Journal of High Resolution Chromatography 19 (1996), S. 585-587 
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; Volatiles ; 2-Heptanol ; Ethyl benzoate ; (E)-Hex-2-enal ; 1-Terpinen-4-oI ; Rubus glaucus ; Rosaceae ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 65
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    Journal of High Resolution Chromatography 19 (1996), S. 596-596 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 66
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    Journal of High Resolution Chromatography 19 (1996) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 67
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    Journal of High Resolution Chromatography 19 (1996), S. 597-607 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Atomic emission detection ; Environmental applications ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Environmental applications of capillary gas chromatography coupled with atomic emission derection (GC-AED) have been reviewed with emphasis on both the commercial and laboratory-built systems. Attention was focused on (1) element-selective detection of non-metallic as well as metallic pollutants, (2) identification of contaminants, and (3) sample preparation considerations.
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  • 68
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    Journal of High Resolution Chromatography 19 (1996), S. 613-616 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Electrochemical detection ; End column detection ; Nickel electrode ; Carbohydrates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbohydrates were separated by capillary electrophoresis (CE) and detected electrochemically using a nickel microelectrode which was operated at a constant applied potential (∼0.6 V vs. Ag/AgCI). A simple capillary electrode holder design facilitated alignment between the separation capillary and the working microelectrode without the use of micro-positioning equipment. The separations were performed under alkaline conditions (pH 〉 11), matching the high pH requirements for amperometric detection at the nickel electrode. The analytical procedure developed showed detection limits for the carbohydrates studied in the micromolar range, showing a linear response in the range tested (micromolar to millimolar). The procedure was used to identify sugars in two real samples (i.e., urine and in a common beverage). The potential use of the system for the determination of amino acids was also demonstrated.
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  • 69
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    Journal of High Resolution Chromatography 19 (1996), S. 691-695 
    ISSN: 0935-6304
    Keywords: HPLC ; Molecular sieve ; Cis-trans isomers ; Phenols ; Selectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A molecular sieve known as Silicalite was used as the column packing for HPLC. Silicalite contains channels (or cavities) approximately 6 Å in diameter but, unlike most other molecular sieves, Silicalite is hydrophobic. The retention times of methyl ketones and substituted phenols containing n-alkyl groups increase with increasing chain length of the substituent. However, phenols with very bulky substituents appear to be excluded from the Silicalite channels and elute very quickly. Excellent separations were obtained for a number of compounds with only slight differences in chemical structure. These include phenol isomers with a primary- or secondary alkyl group, position isomers of substituted phenols, and aliphatic cis-trans isomers.
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  • 70
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis ; Chiral separation ; Cyclodextrin ; Anisodamine ; Glycopyrronium ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 71
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    Journal of High Resolution Chromatography 19 (1996), S. 622-626 
    ISSN: 0935-6304
    Keywords: Multidimensional capillary chromatography ; Polychlorinated biphenyls ; PCBs ; Congener ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multidimensional chromatography was used to resolve the specific chlorobiphenyl (CB) congeners 28, 52, 101, 118, 138, 153, and 180 in technical aroclor standards. Single column analysis of polychlorinated biphenyls (PCBs) results in co-elution of key congeners with other components in the mixture; therefore using two columns of different selectivity was necessary to enhance the resolution achievable on just one column. The HT8 column (8% phenylpolycarborane-siloxane phase) has been reported to have specific selectivity characteristics for improved PCB separation. When coupled with a BPX5 column (5% phenylpolysiloxane-silphenylene phase), it has been shown here to provide unambiguous identification of 7 marker compounds which are used to monitor PCB occurrence and distribution. All seven marker CBs are present in aroclor 1254, and by adjusting the size of the heartcut window, it was possible to obtain resolution of the marker congeners from other congeners. Single column analysis is unable to achieve this result. This offers an alternative to GC-MS analysis.
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  • 72
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    Journal of High Resolution Chromatography 19 (1996), S. 647-650 
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis (CZE) ; Separation of herbicides ; Chlorophenoxy acid ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 73
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    Journal of High Resolution Chromatography 19 (1996) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 74
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    Journal of High Resolution Chromatography 19 (1996), S. 69-79 
    ISSN: 0935-6304
    Keywords: Large volume injection ; PTV injector ; Water analysis ; River sediment ; Pesticides ; Polycyclic aromatic hydrocarbons (PAHs) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Temperature programmable (PTV) injectors with packed widebore (ca. 3.5 mm i.d.) liners are used for large volume injection in capillary gas chromatography with the aim to simplify and/or improve off-line sample pretreatment proecdures. A simple procedure for optimization of large volume PTV injection is described. The system performance, i.e. linearity and repeatability, is evaluated for polar nitrogen/phosphorus containing pesticides (PTV-GC-NPD) and organochlorine pesticides (PTV-GC-ECD) in river water extracts as well as for polycyclic aromatic hydrocarbons (PAHs) in river sediment (PTV-GC-MS).
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  • 75
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    Journal of High Resolution Chromatography 19 (1996), S. 124-126 
    ISSN: 0935-6304
    Keywords: Reversed-phase HPLC ; Propionic antiinflammatory drugs ; Barbituric sedatives and hypnotics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 76
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    Journal of High Resolution Chromatography 19 (1996), S. 128-128 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 77
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    Journal of High Resolution Chromatography 19 (1996), S. 129-129 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 78
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Chiral separation ; Selenium amino acids ; Vancomycin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Baseline separation of the enantiomers of the negatively charged 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatives of cystine, methionine, ethionine, and their seleno analogs can be achieved in 3-5 min with capillary electrophoresis in polyacrylamide coated capillaries and submillimolar concentrations of vancomycin as the chiral selector.In addition to the vancomycin concentration, the separation is affected by the type, concentration and pH of the buffer. Good buffers are more suitable than phosphate buffer. At pH values above the isoelectric point of vancomycin the mobility difference between the enantiomers becomes smaller. This effect is larger than would be expected from the reversal of the vancomycin migration alone.
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  • 79
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    Journal of High Resolution Chromatography 19 (1996), S. 151-154 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Atomic emission spectroscopy ; Enantiomeric separation ; Cyclodextrins ; Chemical warfare agents ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the organophosphorus nerve agents sarin, tabun, and cyclohexyl methylphosphonofluoridate (GF) produces a mixture of two stereoisomers except for soman where four stereoisomers are produced. Significant differences exist in the reported toxicity and AChE inhibition rates of the various stereoisomers. This makes the ability to distinguish between the different stereoisomers desirable. Five different derivatized cyclodextrin stationary phases developed for gas chromatography were tested for their ability to resolve the nerve agent stereoisomers using a gas chromatograph interfaced to an atomic emission detector. Of the five columns that we examined, only the 2,6-di-O-pentyl-3-O-trifluoroacetyl or 2,6-di-O-pentyl-3-O-butyryl γ-cyclodextrins were able to successfully resolve all four soman stereoisomers. The elution order for each column was determined using solutions of isolated soman stereoisomers. Enantiomers of sarin, tabun, and GF were resolved with varying degrees of success on the different cyclodextrin stationary phases. Only the butyryl γ-cyclodextrin was able to separate the enantiomers of all four of the nerve agents examined in this study. The capacity (k) and selectivity (α) factors were determined for each of the chemical warfare agents successfully separated. The TNO Prins Maurits Laboratory in the Netherlands has previously developed several different chromatographic methods to resolve the stereoisomers of soman, sarin, and tabun. The advantage of the method described here is that commercially available cyclodextrin gas chromatography columns were used to resolve the stereoisomers, thereby facilitating rapid and routine analysis of organophosphorus nerve agents.
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  • 80
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    International Journal of Quantum Chemistry 57 (1996), S. 7-15 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution of the Schrödinger equation for the d-dimensional hydrogen atom in a d-dependent potential defined by Gauss' law has been studied by the shifted 1/d method and the δ expansion. These methods provide analytical formulas for the eigenvalues and eigenfunctions which have been tested against “exact” numerical values obtained recently. The comparison shows that the results obtained with the analytical expressions are in excellent accord with the numerical ones and, on the other hand, provide a theoretical justification for a proposed empirical expression for the energies of the two-dimensional hydrogen atom with a logarithmic potential energy function. © 1996 John Wiley & Sons, Inc.
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  • 81
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    International Journal of Quantum Chemistry 57 (1996), S. 17-33 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis of the structure of the optimized effective Kohn-Sham exchange potential vx and its gradient approximations is presented. The potential is decomposed into the Slater potential vs and the response of vs to density variations, vresp. The latter exhibits peaks that reflect the atomic shell structure. Kohn - Sham exchange potentials derived from current gradient approaches for the exchange energy are shown to be quite reasonable for the Slater potential, but they fail to approximate the response part, which leads to poor overall potentials. Improved potentials are constructed by a direct fit of vx with a gradient-dependent Padé approximant form. The potentials obtained possess proper asymptotic and scaling properties and reproduce the shell structure of the exact vx. © 1996 John Wiley & Sons, Inc.
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  • 82
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    International Journal of Quantum Chemistry 57 (1996), S. 43-51 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analytical exact expressions are obtained for matrix elements of the modified Pöschl-Teller oscillator over different operators including powers of the hyperbolic functions sinh(α x), cosh(α x), and tanh(α x) and the differential operators d/dx and d2/dx2. These expressions are derived using explicitly the Pöschl-Teller eigenfunctions. In addition, several recursion relations connecting different Pöschl-Teller matrix elements are obtained using the factorization and hypervirial techniques. It is shown that these relations can be used to make easier the computation of the matrix elements. © 1996 John Wiley & Sons, Inc.
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  • 83
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    International Journal of Quantum Chemistry 57 (1996), S. 53-61 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The D-dimensional Coulomb system serves as a starting point for generating generalized atomic shells. These shells are ordered according to a generalized Madelung rule in D dimensions. This rule together with an Aufbau Prinzip is applied to produce a D-dimensional periodic table. A model is developed to rationalize the ordering of the shells predicted by the generalized Madelung rule. This model is based on the introduction of a Hamiltonian, invariant under the q-deformed algebra Uq(so(D)), that breaks down the SO(D + 1) dynamical symmetry of the hydrogen atom in D dimensions. The D = 2 case (Flatland) is investigated in some detail. It is shown that the neutral atoms and the (moderately) positive ions correspond to the values q = 0.8 and q = 1, respectively, of the deformation parameter q. © John Wiley & Sons, Inc.
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  • 84
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    International Journal of Quantum Chemistry 57 (1996), S. 137-137 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 85
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    International Journal of Quantum Chemistry 57 (1996), S. 1-2 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 86
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    International Journal of Quantum Chemistry 57 (1996), S. 123-135 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio calculations at the scf level were carried out to compute the polarization potential map (mpp) of the nucleic acid bases: cytosine, thymine, uracil, adedine, and guanine. For this purpose, the Dunning's 9s5p basis set contracted to a split-valence, was selected to perform the calculations. The molecular polarization potential (mpp) at each point was evaluated by the difference between the interaction energy of the molecule with a unit point charge and the molecular electrostatic potential (mep) at that point. meps and mpps for the different molecules were computed with a density of 5 points/Å2 on the van der Waals surface of each molecule, defined using the van der Waals radii. Due to the symmetry of the molecules, only half the points were computed. The total number of points calculated was 558 for cytosine, 621 for thymine, 526 for uracil, 666 for adenine, and 699 for guanine. The results of these calculations are analyzed in terms of their implications on the molecular interactions between pairs of nucleic acid bases. © 1996 John Wiley & Sons, Inc.
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  • 87
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    International Journal of Quantum Chemistry 57 (1996) 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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    Topics: Chemistry and Pharmacology
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  • 88
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    International Journal of Quantum Chemistry 57 (1996), S. 139-139 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 89
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    International Journal of Quantum Chemistry 57 (1996), S. 141-155 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The matrix differential calculus is applied for the first time to a quantum chemical problem via new matrix derivations of integral formulas and gradients for Hamiltonian matrix elements in a basis of correlated Gaussian functions. Requisite mathematical background material on Kronecker products, Hadamard products, the vec and vech operators, linear structures, and matrix differential calculus is presented. New matrix forms for the kinetic and potential energy operators are presented. Integrals for overlap, kinetic energy, and potential energy matrix elements are derived in matrix form using matrix calculus. The gradient of the energy functional with respect to the correlated Gaussian exponent matrices is derived. Burdensome summation notation is entirely replaced with a compact matrix notation that is both theoretically and computationally insightful. © 1996 John Wiley & Sons, Inc.
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  • 90
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    International Journal of Quantum Chemistry 57 (1996), S. 157-172 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The size-extensive quadratic CI method with single(s), double(D), and triple (T) excitations, QCISDT, is compared with QCISD, QCISD(T), CCSDT-n, and CCSDT. It is shown that QCISDT results are more accurate than are either QCISD or QCISD(T) results. In particular, QCISDT turns out to be more stable than are QCISD and QCISD(T) in cases with considerable multireference character. QCISDT and CCSDT results are of similar accuracy with slight advantages for the former method. Since QCISDT is much easier to implement on a computer than is CCSDT, it is an attractive alternative to CCSDT. © 1996 John Wiley & Sons, Inc.
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  • 91
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    International Journal of Quantum Chemistry 57 (1996), S. 173-182 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article presents remarks on the meaning of stopping power and of its magnitude. More precisely, the first set of remarks concerns the connection of stopping power with elements of particle-transport theory, which describes particle transport and its consequences in full detail, including its stochastic aspects. The second set of remarks concerns the magnitude of the stopping power of a material and its relation with the material's electronic structure and other properties. © 1996 John Wiley & Sons, Inc.
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  • 92
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    International Journal of Quantum Chemistry 57 (1996), S. 219-227 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the first hydrogen bond of the guanine-cytosine (G-C) pair, the potential function V(r, R) is found for the nonequilibrium bond length R. A new form of the semiempirical potential function, Clementi's calculations for V(r, R0) and some experimental data are used. New wave functions and energy levels as a function of the H-bond length for the ground and several excited states are obtained. This allows one to obtain frequencies and amplitudes of some vibrations of the G-C pair side groups involved in the formation of the hydrogen bond when the latter is not excited and when it is excited to the first energy level. © 1996 John Wiley & Sons, Inc.
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  • 93
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    International Journal of Quantum Chemistry 57 (1996), S. 229-233 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Restricted open-shell Hartree-Fock and unrestricted Hartree-Fock calculations of the electric-field gradient in atoms B, N, O, Al, S, and Cl were performed by relieving the spherical symmetric constraint. The Sternheimer's core polarization effect is then automatically taken into account. The orbitals produced by the axial symmetric self-consistent field are found to have axial symmetry of s-d and p-f mixing types. However, the nonequivalence of the three p orbitals also gives rise to ambiguity. © 1996 John Wiley & Sons, Inc.
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  • 94
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    International Journal of Quantum Chemistry 57 (1996), S. 235-243 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The diagonalization of a class of lattice spin models of a particular structure is first reviewed and secular polynomials for these models are calculated explicitly from the corresponding secular matrices. The structure of the eigenvectors of the given secular matrices is investigated and used to determine the eigenvalues theoretically, and proofs which have not appeared are presented. These results can be compared to the results obtained from the full secular polynomials. © 1996 John Wiley & Sons, Inc.
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  • 95
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    International Journal of Quantum Chemistry 57 (1996) 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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  • 96
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    International Journal of Quantum Chemistry 57 (1996), S. 259-259 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 97
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    International Journal of Quantum Chemistry 57 (1996), S. 263-263 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 98
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    International Journal of Quantum Chemistry 57 (1996), S. 377-389 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The recently introduced set of quadratic ionic and covalent valence indices from changes in the pair-diagonal part of the molecular (Hartree-Fock) two-electron density matrix, ΔΓ(2)(a, b) (orthogonal atomic orbital [OAO] basis set), relative to separated atoms limit (SAL), is extended to cubic valence numbers; they are calculated from the corresponding changes in the three-electron density matrix, ΔΓ(3)(a,b,c). The two- and three-electron indices are given by the corresponding contributions to ΔΓ(2), and ΔΓ(3), which are quadratic and cubic in terms of relevant changes in the one-electron density matrix. The new valence measures are partitioned into one-, two-, and three-center contributions comprising purely ionic (covalent) and mixed ionic-covalent terms. For integral OAO occupations in the SAL, the sum of all three-electron contributions vanishes exactly in the UHF approximation; for fractional occupations, they give rise to a rather small correction to the overall two-electron valence index. The properties of cubic valence numbers are tested on a model three-orbital description of a symmetric (ABA), collinear transition state and on the OQ2 (Q = 1,0, -1) and O2(bond)H+ systems. Preliminary results for B2H6 are also given. © 1996 John Wiley & Sons, Inc.
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  • 99
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    International Journal of Quantum Chemistry 60 (1996), S. 235-248 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extremal pair functions for an n-electron wave function of a closed-shell state are defined as linear combinations of spin-orbital-product pair functions that make some functionals (e.g., r212 or r-112) extremal. They are related to the natural spin geminals in the uncorrelated limit and are useful both for an analysis of wave functions in view of an understanding of the chemical bond and for the treatment of electron correlation. Numerical examples are shown and discussed for He2 as well as the 10-electron systems Ne, HF, H2O, NH3, and CH4. © 1996 John Wiley & Sons, Inc.
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  • 100
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    International Journal of Quantum Chemistry 60 (1996), S. 287-295 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The generalized Langevin equations are presented by considering such microscopic motions of molecules described by the microscopic Hamiltonian whose potential function is quadratic and internal degree of freedom is multidimensional. Considering the long time behavior of the reactive mode, the Grote-Hynes equation has been derived from the generalized Langevin equations. Furthermore, we have proved that solving the Grote-Hynes equation is equivalent to solving the eigenvalue problem for the whole system, and then the Grote-Hynes treatment coincides with the transition-state theory for the whole system. © 1996 John Wiley & Sons, Inc.
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