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  • Analytical Chemistry and Spectroscopy  (98)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 3 (1970), S. 1-11 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The low resolution and complete high resolution mass spectra of a series of methyl and deuterium substituted bicyclo[4.1.0]heptane-2-one derivatives have been measured. An attempt has been made to test the operation of a fragmentation process analogous to the known photochemical rearrangement, and to determine if the substitution effects critical to the photorearrangement also influence the electron-impact process. The fragmentation pattern of these conjugated cyclopropyl ketones is detailed and the influence of the cyclopropyl ring is discussed. It is suggested that electron-impact-induced rearrangements which are analogous to photochemical transformations will be relatively low energy processes and will remain prominent at low ionizing voltages.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 4 (1990), S. 61-77 
    ISSN: 0886-9383
    Keywords: Infrared ; Spectroscopy ; Spectrometry ; Retrieval ; Confirmation ; Chemometrics ; Adequate peaks ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the series of analytical techniques for identification of chemical substances, infrared spectrometry presents by far the highest information content. However, the information is most complicated too. It concerns a multitude of band positions, band intensities and band shapes, which, moreover, can be disturbed by matrix and other effects. The high redundancy, however, allows conclusions to be made by a qualitative, subjective procedure.IR is often used to prove the equality between a sample and a reference material, e.g. in quality control of a production process. In forensic control, the question to be answered is mostly not to prove equality, but whether or not the presence of a compound in a sample, e.g. a drug, can be proved. Moreover, testing has to be performed according to objective rules.To fulfil these requirements, a new retrieval algorithm, the ‘Adequate Peaks Search’, is presented. It concerns representing the reference spectra by sets of adequate peak positions and the sample spectrum by a set of all peak positions, whereafter the cross-sections of the sample set and the reference sets are determined. The concept ‘adequate peak’ is defined and criteria have been formulated to evaluate the results into a positive (presence of the analyte is proved) or negative (presence is not proved) conclusion.The detection limit when the Adequate Peaks Search (APS) method was applied was four to seven times lower than that attained by a number of experts.
    Additional Material: 8 Ill.
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  • 3
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of protonation and hydrogen bonding in linear Schiff bases obtained from n-butylamine with butyraldehyde, crotonaldehyde, sorbaldehyde and all-trans-retinal were studied by means of 15N and 13C NMR. The protonation-induced chemical shifts (Δδ) are an order of magnitude larger for 15N than for 13C. For 15N, this effect was found to increase with the extent of conjugation, culminating in the retinylideneimine (Δδ = -146 ppm), which constitutes a model for the study of the structure of the Schiff base linkage in visual pigments and related systems. Theoretical calculations of protonation-induced Δδ values based on MINDO/ 3 are in agreement with experimental results.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 635-642 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potent endectocide 23-(O-methyloximino)-F28249α and related compounds were identified and characterized by mass spectrometry. The fragmentation pathway of 23-(O-methyloximino)-F28249α was identified by its high-resolution mass spectrum and the electron impact unit mass spectra of its homologs. This fragmentation pathway is presented and discussed.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 196-198 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H and 77Se spin-lattice relaxation times have been measured for the series of organochalcogen compounds MeE(CH2)nEMe (E=S, Se, n=0-3; E = O, n = 1, 2). The methyl and methylene proton T1 values decreased with increasing mass/size of the chalcogen and with increasing methylene chain length. The values are primarily due to intra- and inter-molecular dipole-dipole relaxation with proton-proton cross-relaxation effects playing a significant role. 77Se T1 values are dominated by spin rotation and chemical shielding anisotropy mechanisms, their relative importance depending on the size of the molecule and temperature of measurement.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 8 (1974), S. 409-412 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass Spectra of the methyl esters of ethane, n-propane, isopropane, n-butane, sec-butane and tert-butane sulphinic acids have been determined. In general, the parent ions are of low abundance and the most prevalent are the hydrocarbon ions which arise by α-cleavage. Other ions that serve to characterise these compounds are those from the CH4SO2 and HSO2 fragments.
    Additional Material: 1 Tab.
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  • 7
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A highly sensitive (subpicomole level), structure-specific method of analysis has been developed for characterizing and quantitating the dinucleotide thymidylyl(3′ → 5′)thymidine methyl phosphotriester by desorption chemical ionization tandem mass spectrometry. The methodology can be applied to related compounds such as the parent dinucleotide and employs either positive or negative ionization mass spectra or daughter spectra. The procedure allows specification of the site of methyl attachment.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 221-227 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Human exposure to aromatic amines may be monitored by measuring the amount of sulfinamide adduct bound to hemoglobin. In order to develop a sensitive and selective method for measuring aromatic amines present in low concentrations the mass spectra of the pentafluoropropionamide derivatives of a series of aromatic amines were determined under various ionization conditions. With electron ionization the aromatic amine derivatives typically yield intense molecular ions with fragmentation leading to elimination of C2F5 and COC2F5. Higher molecular weight polycyclic aromatic amines, e.g., 6-aminochrysene, give prominent molecular ions as well as intense ions corresponding to M-174 (loss of CNHCOC2F5). With positive chemical ionization using methane as reagent gas the derivatives give protonated molecular ions as the base peaks, as well as the associated ions at M + 29 and M + 41. Negative ion chemical ionization yields, primarily, peaks corresponding to the loss of HF from the molecular anions. Negative ion chemical ionization with selected ion monitoring is generally more suitable than positive chemical ionization or electron ionization for the quantitative analysis of aromatic amines present in biological samples in the mid femtomolar range. Exposure of human subjects to aromatic amines was determined via basic hydrolysis of the isolated sulfinic acid amide hemoglobin adducts. Analysis of the derivatized extracts by gas chromatography/negative ion chemical ionization/mass spectrometry demonstrated the presence of aniline, ortho-, meta-, and para-toluidine, 2-naphthylamine, and 4-aminobiphenyl. The hemoglobin adduct levels of these amines in both cigarette smokers and nonsmokers were determined. The mean values of the adduct levels of ortho- and para-toluidine, 2-naphthylamine, and 4-aminobiphenyl were higher in smokers than in nonsmokers, while the mean adduct values of aniline and meta-toluidine were similar in both groups. Adducts of 2-, 3-, 4-ethylaniline, 2,3-, 2,4-, 2,5-, 2,6-dimethylaniline, and 3-aminobiphenyl have been detected in smokers' blood. 1-Aminoanthracene, 9-aminophenanthrene, and 6-aminochrysene have not been detected. GC/MS procedures were also used to determine the extent of binding of aniline-2,3,4,5,6-d5 to hemoglobin in rats administered aniline-d5.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 248-252 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Column loadability - overload phenomenon ; Non-classical approach to theory of loadability ; Effect on retention times, peak shape ; Effect of column length ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The usual concepts of the dynamics of an overloaded solute band fail to explain several phenomena such as the typical “leading-tail” shape and retention deviations exhibited by overloaded peaks, and why these defects are more commonly observed in short columns. These and other related deviations from theory can be rationalized by a non-classical approach to the overloading phenomenon.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 10 (1987), S. 467-469 
    ISSN: 0935-6304
    Keywords: GC/FTIR/MS coupling ; Curie-point pyrolysis ; Programmable automatic multisampler ; 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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