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  • Electronic Resource  (378)
  • 1995-1999  (378)
  • 1900-1904
  • Analytical Chemistry and Spectroscopy  (378)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1051-1055 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Electroblotting proteins separated by gel electrophoresis provides a suitable support for further manipulations and analysis of small amounts of relatively pure samples. On-membrane digestion, peptide mapping by mass spectrometry, and database searching offer sensitive and fast tools to identify the analyte. By providing sequence information, tandem mass spectrometry can go a step further, confirming the database identification, solving problems connected with post-translational modifications and sequence variations, or supplying the stretches of internal sequence necessary to synthesize an oligonucleotide probe for gene isolation. The viability of this approach was successfully evaluated using different tandem mass spectrometric techniques: metastable decomposition in a matrix-assisted laser desorption/ionization (MALDI) time-of-flight instrument with a curved-field reflectron; low energy collision-induced dissociation in a MALDI quadrupole ion trap mass spectrometer; and high energy collision-induced dissociation in a high-performance four-sector mass spectrometer with massive cluster-impact ionization.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-6304
    Keywords: Electrokinetic chromatography (EKC) ; Pseudo-stationary phase ; Micelles ; Dendrimers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 245-246 
    ISSN: 0935-6304
    Keywords: Chloride ; suppressed ion chromatography ; concrete ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 569-571 
    ISSN: 0935-6304
    Keywords: Supercritical Fluid Extraction (SFE) ; Gas chromatograph ; Pesticides residues ; Fluazinan ; 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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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 476-480 
    ISSN: 0749-1581
    Keywords: NQR ; 35Cl NQR ; MO theory ; H-bonds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The charge distribution in hydrogen bridges of varying strengths in solid 2-chloro-4-nitrobenzoic acid complexes was studied using the 35Cl nuclear quadrupole resonance technique (NQR). The dependence of 35Cl NQR frequencies on the proton affinities was analysed. Molecular orbital calculations using atom superposition and electron delocalization molecular orbital theory showed that the trends of changes in the charge density on the chlorine, nitrogen and oxygen atoms, and on the binding energy and the bond order of NH and OH groups are consistent with the NQR results. Also, the agreement between theoretical and experimental results showed that the 3,5-dimethylpyridine complex represents the critical point at 50% proton transfer.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0749-1581
    Keywords: 1H NMR ; 13C NMR ; substituted dihydronaphthalenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H and 13C NMR studies were carried out on the substituted dihydronaphthalene compounds 1,2-dihydro-8-isopropyl-6,7-dimethoxy-2-methylnaphthalene, 3-bromo-1, 2-dihydro-8-isopropyl-6, 7-dimethoxy-2-methylnaphthalene, 3, 4-dihydro-5-isopropyl-6, 7-dimethoxy-3-methyl-1(2H)-naphthalenone, 1, 2-dihydro-6, 7-dimethoxy-2, 8-dimethylnaphthalene, 3-bromo-1, 2-dihydro-6, 7-dimethoxy-2, 8-dimethylnaphthalene and 3, 4-dihydro-6, 7-dimethoxy-3, 5-dimethyl-1(2H)-naphthalenone. Complete assignments of the proton and carbon spectra were made using one- and two-dimensional NMR techniques including APT, COSY, NOESY and 1H-13C HETCOR spectroscopy.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0749-1581
    Keywords: peptides ; HPLC-NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The efficiency of directly coupled HPLC - NMR spectroscopy for the separation and characterization of synthetic peptide libraries was investigated using a model system based on a mixture of all 27 tripeptide combinations of alanine (A), methionine (M) and tyrosine (Y) as the C-terminal amides. The 1H NMR spectra were obtained in real time using on-flow HPLC - NMR spectroscopy at 600 MHz and 21 of the 27 peptides were identified on the basis of chemical shifts and coupling constants, including the use of diagnostic values derived from 1H NMR spectra and 1H—13C and 1H—15N HMQC studies on authentic A—A—A—OH and Y—Y—Y—OH. The effects on 1H NMR chemical shifts of pH and of varying proportions of acetonitrile and water as occurred during the gradient elution HPLC run were evaluated. The HPLC - NMR approach could provide a facile method for investigating the relative efficiency of resin-based peptide synthesis for different amino acid combinations and should rapidly provide data suitable for deriving structure-retention time relationships for peptides.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 9 (1995), S. 125-135 
    ISSN: 0886-9383
    Keywords: Procrustean analysis ; FT-IR spectroscopy ; NIR spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Procrustean methods allow the fitting of a given matrix to another given matrix observed on the same objects. In the traditional approach orthogonal constraints are imposed upon the transformation matrix, whereas in the alternative approach Procrustean analysis may be performed without such constraints. The two methods (with and without constraints) were compared on data dealing with mid- and near-infrared spectra of oil. The aim was to reconstruct the mid-infrared spectral information using data from the near-infrared spectra. Unconstrained Procrustean analysis proved to be the more efficient for both the calibration and verification sets. Furthermore, the analysis of the transformation matrix between the two infrared ranges made it possible to indicate wavelengths and wave numbers corresponding to the same chemical groups.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0935-6304
    Keywords: Natural gas analysis ; Sulfur components ; Sulfur selective detection ; Universal detectors ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present contribution, the performance of a number of commercially available selective and universal detectors that can be used in the analysis of sulfur components in natural gas is evaluated in terms of sensitivity, selectivity, reproducibility, quenching effect, stability, and compound dependence of the sulfur response. Investigated detectors include the sulfur chemiluminescnce, the flame photometric, the electron capture, the mass spectrometric, the thermal conductivity, and the flame ionization detector. The sulfur chemiluminescence detector was found to have the best overall performance, e.g., low picogram amounts of sulfur can be detected accurately and the linear dynamic range is more than five orders of magnitude. After careful optimization, the sulfur response of this detector was found to be almost compound independent. All other detectors, including the flame photometric and the electron capture detector, have more or less compound dependent responses.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 535-539 
    ISSN: 0935-6304
    Keywords: Coupled LC/GC ; Solid phase extraction ; Automated SPE/GC ; Co-solvent effect ; NP-pesticides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to meet the requirements of analyzing very low concentrations of pesticides in water (typically at 0.1 μg/l or less), samples have to be concentrated prior to GC-analysis. Samplie pre-concentration by off-line methods based on solid phase extraction (SPE) or liquid-liquid extraction are very time consuming and cumbersome. Moreover, the quantitative performance of the analytical method as a whole in terms of accuracy and reliability is seriously hindered by elaborate, manually performed sample pre-treatment steps. This paper describes an automated method based on solid phase extraction and capillary gas chromatography. The technique was applied for the analysis of 31 polar organophosphorus and organonitrogen pesticides. A commercially available HPLC/GC instrument is modified, using the LC-part for solid phase extraction. The sample, of which only a few ml's is required to obtain sufficiently low detection limits, is delivered by a robotic large volume autosampler. After solid phase extraction and elution, the eluate is transferred into the GC via a so called “loop type interface”. In this paper the instrumentation and analytical methodology is described, as well as the main validation results. The quantitative performance (i.e. recovery and repeatability) of the most polar solutes like metamitron and dimethoate appears to be better than obtained with off-line SPE as a result of the more beneficial ratio between the amount of sorbent and the sample volume. As the loop-type interface causes losses of the most volatile compounds, a co-solvent is added. This co-solvent provides sufficient trapping capacity in the capillary pre-columns to allow quantitative analysis of even the most volatile pesticides. Moreover a better separation of early eluting compounds is also established.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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