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  • 550 - Earth sciences  (29)
  • Magnetism  (27)
  • Analytical Chemistry and Spectroscopy  (25)
  • Biochemistry and Biotechnology  (21)
  • 1
    Electronic Resource
    Electronic Resource
    Separation of Positional Isomers on A, C- and A,D-Bridged Calix[6]arene as Stationary Phases in Capillary GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 679-682 
    Details
    ISSN: 0935-6304
    Keywords: A,C- and A,D-bridged calix[6]arene ; stationary phase ; capillary gas chromatography ; geometric and positional isomer separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A,C-Bridged (ACCX) and A,D-bridged isopropyldimethylsilylcalix[6]arene (ADCX) dissolved in OV-1701 were used as stationary phases in isothermal capillary gas chromatographic separation of some positional isomers. Retention factors and separation factors for the isomers were measured. The isomers investigated are well resolved on the two phases. Retention of all the solutes investigated is longer on ACCX than on ADCX. The longer retention on A,C-bridged calix[6]arene is probably due to extra inductive interactions of the solute molecule with the carbonyl moieties in the phase. Separation factors for closely eluting isomer pairs are similar on the two phases. This seems to indicate that the carbonyl moieties do not play an appreciable role in discriminating the isomer molecules on entering the cavity of the calixarene if the solute is retained by the inclusion process.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Proton-transfer reactions within ionized methanol clusters: Mass spectrometric and molecular orbital studies (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 969-976 
    Details
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Proton-transfer reactions that proceed within methanol cluster ions were studied using an electron impact time-of-flight mass spectrometer. When CH3OH seeded in helium is expanded and ionized by electron impact, the protonated species, (CH3OH)nH+, are the predominant cluster ions in the low-mass region. In CH3OD clusters, both (CH3OD)nH+ and (CH3OD)nD+ ions are observed. The ion abundance ratios, (CH3OD)nH+/(CH3OD)nD+, show a tendency to decrease as the methanol concentration increases, which is apparently related to the cluster structure and reaction energetics. The results suggest that the effective formation of (CH3OD)nH+ ions at low concentration of CH3OD in the expansion is the result of the relatively facile rotation of methanol molecules within the smaller clusters that tend to form at low CH3OD concentration. Ab initio molecular orbital calculations were carried out to investigate the rearrangement and dissociative pathways of ionized methanol dimer. Ion-neutral complexes, [CH3OH2+…O(H)CH2] and [CH3OH2+…OCH3], are found to play an important role in the low-energy pathways for production of CH3OH2+ + CH2OH (and OCH3) from ionized methanol dimer.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jms.1190300706
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  • 3
    Electronic Resource
    Electronic Resource
    Electron impact ionization of ethylene-methanol heteroclusters: Stable configurations and mechanisms in intracluster ion-molecule reactions (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 931-939 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions that proceed within mixed ethylene-methanol cluster ions were studied using an electron impact time-of-flight mass spectrometer. The ion abundance ratio, [(C2H4)n(CH3OH)mH+]/[(C2H4)n(CH3OH)m+], shows a propensity to increase as the ethylene/methanol mixing ratio increases, indicating that the proton is preferentially bound to a methanol molecule in the heterocluster ions. The results from isotope-labelling experiments indicate that the effective formation of a protonated heterocluster is responsible for ethylene molecules in the clusters. The observed (C2H4)n(CH3OH)m+ and (C2H4)n(CH3OH)m-1CH3O+ ions are interpreted as a consequence of the ion-neutral complex and intracluster ion-molecule reaction, respectively. Experimental evidence for the stable configurations of heterocluster species is found from the distinct abundance distributions of these ions and also from the observation of fragment peaks in the mass spectra. Investigations on the relative cluster ion distribution under various conditions suggest that (C2H4)n(CH3OH)mH+ ions with n + m ≤ 3 have particularly stable structures. The result is understood on the basis of ion-molecule condensation reactions, leading to the formation of fragment ions, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_2=\!=\mathop {\rm O}\limits^ + {\rm CH}_3 $\end{document} and (CH3OH)H3O+, and the effective stabilization by a polar molecule. The reaction energies of proposed mechanisms are presented for (C2H4)n(CH3OH)mH+(n + m ≤ 3) using semi-empirical molecular orbital calculations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210280902
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  • 4
    Electronic Resource
    Electronic Resource
    Application of capillary electrophoresis to amino acid sequencing of peptide (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 510-515 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Micellar electrokinetic chromatography ; Peptide sequencing ; Phenylthiohydantoin-amino acids ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Separations of twenty phenylthiohydantoin (PTH) amino acids, and amino acid derivatives, resulting from the Edman degradation of peptides and proteins, were optimized for peptide sequencing by capillary electrophoresis. Manual sequencing of angiotensin II was performed by Edman degradation and capillary electrophoresis of the PTH amino acid obtained after each cycle. The results were compared with those of an automated conventional protein sequencer. Interfacing capillary electrophoresis with Edman degradation provides an additional option for protein sequencing.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150160184
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  • 5
    Electronic Resource
    Electronic Resource
    Mixed-dye staining method for protein detection in polyacrylamide gel electrophoresis using calconcarboxylic acid and rhodamine B (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2412-2415 
    Details
    ISSN: 0173-0835
    Keywords: Protein staining ; Sodium dodecyl sulfate-polyacrylamide gel electrophoresis ; Calconcarboxylic acid ; Rhodamine B ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: We have developed a new mixed-dye protein staining method that is simple, rapid, and sensitive. A freshly prepared mixture of calconcarboxylic acid (NN, 0.02%) and rhodamine B (RB, 0.04%) in 40% methanol / 7% acetic acid, was used as a staining solution. RB acts as an auxiliary agent to inhibit the binding of NN to the gel matrix, reducing the background staining and therefore enhancing the protein staining by NN. This mixed-dye staining method reduces the total staining and destaining time to less than an hour, and increases the sensitivity to 25 ng of bovine serum albumin, which is greater than the 100 ng sensitivity limit of Coomassie Brilliant Blue R-250 (CBBR) staining.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191409
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  • 6
    Electronic Resource
    Electronic Resource
    Gas chromatographic enantiomer separation on polysiloxane-anchored permethyl-β-cyclodextrin (Chirasil-Dex) (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 713-717 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; Polysiloxane-anchored cyclodextrin stationary phases ; Chirasil-Dex ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240131012
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  • 7
    Electronic Resource
    Electronic Resource
    New on-line concentrator for LC-GC: Analysis of PAHs with LC-GC (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 748-753 
    Details
    ISSN: 0935-6304
    Keywords: LC-GC ; PAHs ; Glass, vial-shaped concentrator ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new, versatile, and low cost on-line LC-GC interface has been devloped for the fast and reliable introduction of large volume samples into a cappillary GC column without using the conventional retention gap. PAHs in soot were analyzed by on-line normal phase HPLC-capillary GC. A glass, vial-shaped on-line concentrator provides a zone for solvent evaporation and sample concentration. Large volumes of HPLC eluate can be concentrated with the on-line concentrator and then transferred directly into the cappillary column. Trace levels (〈 10 ppb) of PAH compounds can be efficiently concentrated with the on-line concentrator and determined without loss or contamination.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240131105
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  • 8
    Electronic Resource
    Electronic Resource
    Extending the scope of enantiomer separations on Chirasil-Dex by GLC: Comparison with permethylated β-cyclodextrin dissolved in OV-1701 (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 723-729 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective GC ; Polysiloxane-anchored cyclodextrin stationary phase ; Chirasil-Dex ; Cyclodextrin derivatives dissolved in OV-1701 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: GLC on polysiloxane-anchored permethylated β-cyclodextrin (Chirasil-Dex) has been used to separate the enantiomers of 106 racemates of different classes of compounds ranging from alkanes to highly polar compounds such as underivatized diols and free acids. Chromatographic data are listed and compared with those obtained by GLC on permethylated β-cyclodextrin dissolved in OV-1701.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240151106
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  • 9
    Electronic Resource
    Electronic Resource
    CGC enantiomer separation on diluted cyclodextrin derivatives coated on fused silica columns (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 470-474 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective capillary gas chromatography ; Enantiomer separation of volatiles ; Cyclodextrin derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-resolution capillary gas chromatographic separation of enantiomers, belonging to different classes of compounds on cyclodextrin derivatives is described. The solutions of heptakis (2,3,6-O-trimethyl)-β-cyclodextrin (Phase I), heptakis (2,6-O-dimethyl-3-O-trifluoro-acetyl)-β-cyclodextrin (Phase II) and heptakis (2,6-O-dimethyl-3-O-heptafluorobutyryl)-β-cyclodextrin (Phase III) in the moderately polar polysiioxane OV-1701 were coated onto deactivated fused silica capillaries furnishing columns of high efficiency. The three phases show different enantioselectivities for various racemic mixtures.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240130706
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  • 10
    Electronic Resource
    Electronic Resource
    Automated analysis of volatile halogenated hydrocarbons in rainwater and ambient air by purge and trap capillary gas chromatography (1991)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 14 (1991), S. 83-90 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Volatile halogenated hydrocarbons (VHH) ; Purge and trap technique ; Automated system ; Rainwater ; Ambient air ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An automated system employing a purge and trap technique with capillary gas chromatography and electron-capture detection (ECD) has been developed for the analysis of trace levels of volatile halogenated hydrocarbons and applied to the determination of the compounds in environmental samples such as rainwater and ambient air. The operation of the method, its application to environmental samples, and the results obtained are described. Use of the system ensured good chromatographic resolution and high accuracy, even with trace levels of the compounds.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240140204
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