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  • 1980-1984  (4,319)
  • Analytical Chemistry and Spectroscopy  (4,318)
  • Nuclear reactions
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  • 101
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mass Spectrometry Reviews 3 (1984), S. 161-207 
    ISSN: 0277-7037
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 20 Ill.
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  • 102
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mass Spectrometry Reviews 3 (1984), S. 319-355 
    ISSN: 0277-7037
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 103
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mass Spectrometry Reviews 3 (1984), S. 357-394 
    ISSN: 0277-7037
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 30 Ill.
    Type of Medium: Electronic Resource
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  • 104
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mass Spectrometry Reviews 3 (1984) 
    ISSN: 0277-7037
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 105
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mass Spectrometry Reviews 3 (1984), S. 527-585 
    ISSN: 0277-7037
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 106
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984) 
    ISSN: 0306-042X
    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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  • 107
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 55-59 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fast atom bombardment mass spectral data are presented for the polypeptides insulin, oxidized insulin A-chain, carboxymethylated insulin B-chain, and glucagon. The doubly-charged molecular ion of the intact insulin molecule produced with fast atom bombardment with xenon atoms is observed at a reduced accelerating voltage (4 kV).
    Additional Material: 4 Ill.
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  • 108
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The capillary gas chromatographic negative ion chemical ionization mass spectrometric assay of peptidoaminobenzophenone (2-o-chlorobenzoyl-4-chloro-N-methyl-N′ -glycylglycinanilide) (1) and its three metabolites in human plasma reported in Part 1 was changed as follows: (1) the reagent gas was changed to ammonia from isobutane; (2) each unlabelled compound (1%) was added to the deuterium-labelled compound used as the internal standard; (3) all samples were injected in the splitless mode; (4) one more metabolite, lormetazepam, was determined; (5) day-to-day reproducibility was checked in the range of 1-50 ng ml-1. Points 1 to 3 improved the preciseness with small-sized samples. Calibration curves were prepared in the range of 0.5-50 ng ml-1. Plasma levels of compound 1 and its four metabolites in 10 volunteers were measured.
    Additional Material: 1 Ill.
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  • 109
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 63-67 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the chemical ionization mass spectral characteristics of a series of derivatized 1-benzyltetrahy-droisoquinoline alkaloids is presented. Tetrahydropapaveroline and some related benzyltetrahydroisoquinolines were converted to their corresponding O-trimethylsilyl of N-trifluoroacetyl-O-trimethylsilyl derivatives prior to analysis by combined gas chromatographic methane chemical ionization mass spectrometry. The chemical ionization mass spectra of the derivatized alkaloids are compared to the electron impact mass spectra of the N-trifluoroacetyl-O-trimethylsilyl derivative of tetrahydropapaveroline, a representative benzyltetrahydroisoquinoline alkaloid. The effects of the nitrogen substituent and ion source pressure on the relative abundance of significant ions in the chemical ionization mass spectra of these alkaloids are also described.
    Additional Material: 2 Ill.
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  • 110
    Electronic Resource
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 101-105 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The copper salt of tenuazonic acid was studied by both positive and negative ion techniques. Fragmentation was elucidated with the aid of collision-induced dissociation/mass-analysed ion kinetic energy spectroscopy. During the course of the investigations, a homolog of tenuazonic acid was tentatively identified by using a combination of mass spectral techniques.
    Additional Material: 3 Ill.
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  • 111
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984) 
    ISSN: 0306-042X
    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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  • 112
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 202-202 
    ISSN: 0306-042X
    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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  • 113
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984) 
    ISSN: 0306-042X
    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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  • 114
    Electronic Resource
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 203-206 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have developed a method for determination of chlorhexidine, a disinfectant, in medical waste water by selected ion monitoring (SIM). Our method consists of the following procedures. (1) Chlorhexidine in the medical waste water was extracted and purified by an Extrelut® column with ethyl acetate. (2) The eluted chlorhexidine was converted to a triazine derivative with trifluoroacetic anhydride. (3) The triazine derivative was subjected to on-column methylation on a gas chromatographic column. (4) Finally, the triazine N-methyl derivative of chlorhexidine was identified and determined by SIM. Recoveries of the compound added to medical waste water were about 90% in amounts ranging from 1 to 10 μg. In the waste water from our medical waste water treatment plant, chlorhexidine concentrations were found to be 0.085-1.94 mg I-1. The present method is superior to the pre-existing ones in its quick separation, specificity and sensitivity.
    Additional Material: 4 Ill.
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  • 115
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 211-216 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The identification of biotransformation products of the new antihypertensive drug urapidil in mouse, rat, dog and man has been performed by means of high-performance liquid chromatographic and mass spectrometric techniques. In urine, three metabolites were found in addition to the unchanged drug. The para-hydroxylated product (1) (6-{3-[4-(o-methoxy-p-hydroxyphenyl) piperazinyl]-propylamino}-1,3-dimethyl-uraci), the O-demethylated compound (2) (6-{3-[4-(o-hydroxyphenyl) piperazinyl]-propylamino}-1,3-dimethyluracil) and the uracil-N-dealkylated compound (3) (6-{3-[4-(o-methoxyphenyl)piperazinyl]-propylamino}-1-methyl-uracil). In urine of dog, the metabolite with the N-oxide structure (5) was also identified, but only in trace arnounts (6-{3-[4-(o-methoxyphenyl)piperazinyl-N-oxide]-propylamino}-1,3-dimethyluracil).
    Additional Material: 5 Ill.
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  • 116
    Electronic Resource
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 207-210 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both the advantages and limitations of gas chromatography negative ion chemical ionization (NICI) mass spectrometry arise from the technique's close similarity to gas chromatography using a conventional electron capture detector (ECD). The specificity of both techniques arises from the wide range of response factors from different compound classes. However, the fact that almost every compound has some electron capture response is the reason the ECD has the reputation of being the least specific of the specific detectors for pesticide residue analysis. Moreover, while good ECD response means good NICI response, it does not guarantee sufficient negative ion mass spectral data for confirmatory purposes. The applications presented in this paper illustrate both the advantages and limitations of the technique. The most obvious applications are straightforward extensions of gas chromatographic ECD methods of analysis as illustrated in the gas chromatographic NICI analysis of pendimethalin, a dinitroaniline herbicide, at the pg level. The use of gas chromatography NICI as a confirmatory technique to complement a gas chromatographic method using a flame photometric detector is shown in the analysis of fosthietan, an organophosphate pesticide, in corn tissues. The gas chromatographic NICI analysis of sulfamethazine residues in cattle and swine tissues exemplifies that good ECD response does not guarantee satisfactory negative ion mass spectral data for confirmatory purposes.
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  • 117
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 217-222 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Basic aspects f fast atom bombardment mass spectrometry such as matrix effects, discriminatory effects between positive and negative ion formation, sensitivity, and isotope dilution have been investigated using oligopeptides and amino acid derivatives as model compounds. The matrix selected was found to have a decisive influence on the sensitivity of fast atom bombvardment. Acidic and basic properties of the samples could be correlated with different ionization efficiencies in positive or negative ion formation. With respect to sensitivity, a roughly linear relation between signal intensity and sample amount was observed in the range of 1 ng to 10 μg of sample. Nanogram amounts of samples could be detected by fast atom bombardment mass spectrometry. Finally, the suitability of fast atom bombardment for quantitative investigations is proven by the investigation of isotopically labelled mixtures.
    Additional Material: 8 Ill.
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  • 118
    Electronic Resource
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 223-229 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The positive and negative chemical ionization mass spectra of 29 amino acid carboxy-n-butyl ester N-(O,S)-Pentafluoropropionate derivatives hae been determined. The positive ion (PI) mass spectra conform to the expected fragmentation patterns for this amino acid derivative but their methane negative ion chemical ionization (NICI) mass spectra displayed marked differences between various amino acid classes and bvetween positional isomers within the same class. Isomeric butyric acid (α, β and γ) and tyrosine (o, m amd p-hydroxylation) derivatives all had remarkably difterent NICI mass spectra. Aliphatic amino acid CO2-n-butyl-N-PFP derivatives (except glycine) can be readily recognized by a characteristic fragmentation process corresponding to [M-H-C4CO2H]-. Deuterium labellung studies were used to delineate some of the major NICI fragmentation processes. While the PICI mass spectra all gave comparable detection responses differences were observed with various amino acids when operating in the NICI mode. The order of sensitivity of detection for six representative amino acid-carboxy-n-butyl-N-PFP derivatives were: hydroxyproline 〉 lysine 〉 cysteine 〉 glycine=leucine=methionine in the ratio of 100:20:7:1. In PICI mass spectrometry derivatized leucine yielded a response 25 times less than its NICI mass spectrometric value.
    Additional Material: 2 Ill.
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  • 119
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 230-235 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron impact fragmentations of amino-oxy acid esters and their N-acetyl derivatives were studied. Primary fragmentation led to elimination of amino-oxy or ester groups providing structurally significant ester or amino-oxy ions, respectively. N-acetyl derivatives expel a keten molecule providing molecular ions of amino-oxy acid esters, which in turn follow the above mentioned pathways of fragmentation. In addition, N-acetyl amino-oxy ions were observed in the mass spectra of N-acetyl derivatives. The mass spectral fragmentation pattern of amino-oxy acid esters and their N-acetyl derivatives as well as their volatility and thermostability suggest such substances as being useful derivatives for gas chromatographic/mass spectrometric studies of naturally occurring amino-oxy compounds.
    Additional Material: 7 Ill.
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  • 120
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fast heavy ions, i.e. fission fragments from a 252Cf-source, have been used to desorb and ionize peptides and proteins from a sample surface. Masses of the desorbed ions have been determined by the time-of-flight technique. The mass interval of the molecules studied is 1000-14 000 u. Quasi-molecular ions of higher masses than earlier reported have been observed. The results include the detection of quasi-molecular ions of proinsulins, cytochrome-C, ribonuclease and two phospholipases. The general features of mass spectra of proteins using this ionization method are described. Emphasis is put on the discussion of metastable ion decay, neutral components, multiply charged ions, isotopic broadening, and cluster ion formation. Also the precision which can be obtained with a straight time-of-flight mass spectrometer will be discussed. Future applications of the technique are outlined.
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  • 121
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    Biological Mass Spectrometry 11 (1984), S. 258-258 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 122
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984) 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 123
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Macroions of lysozyme and polystyrene produced by the electrospraying of dilute solutions of these macromolecules into nitrogen gas at atmospheric pressure have been studied by means of the measurement of their mobilities in nitrogen by means of an ion-drift spectrometer. In the case of polystyrene mainly clusters of negative macroions have been detected and studied, but in the case of lysozyme macroions containing one, two or three positive charges can be identified. The effect of change of solution concentration, temperature and pressure in the ion-drift tube on the data obtained in the case of polystyrene has been observed.
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  • 124
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 269-272 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An isotope dilution mass spectrometry method is described for determining chenodeoxycholic acid pool size in children. The stable isotopically labeled tracer. (11,12-2H2) chenodeoxycholic acid, was administered orally to children, and the enrichment of bile was measured by selected ion monitoring gas chromatography mass spectrometry. The level of (11,12-2H2) chenodeoxycholic acid enrichment found in the patient samples was in the range of 0.5 to 5%. Data are presented illustrating the duplication of this method in two independent laboratories using standard quadrupole mass spectrometers. This procedure provides the clinician with a non-radioactive method for determining chenodeoxycholic acid pool size which is especially beneficial in studies involving children and pregnant women.
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  • 125
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Negative ionization resulted in the simplification of a previously published method. The new method permits the determination of 0.25 nmol l-1 nitroglycerol in plasma with a coefficient of variation of 9.1%.
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  • 126
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extracts derived from rat liver and Phaseolus leaves are shown, by collision-induced dissociation of [MH]+ ions generated by fast atom bombardment mass spectrometry, to contain cytidine 3′,5′-cyclic monophosphate and guanosine 3′,5′-cyclic monophosphate respectively, and not the 2′,3′-cyclic isomers. Interference peaks, expected to be common to all mass-analysed ion kinetic energy spectra of ions generated by the fast atom bombardment process from glycerol-based matrices are identified. It is shown that unequivocal identification of cytidine 3′,5′-cyclic monophosphate can be made at the microgram level. Attempts to derive a quantitative procedure based on using different cyclic nucleotides as internal standards were unsuccessful due to the poor solubility of these compounds in the matrix system.
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  • 127
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    Biological Mass Spectrometry 11 (1984), S. i 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 128
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    Biological Mass Spectrometry 11 (1984), S. 415-420 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A MAT 731 mass spectrometer has been modified to permit multiple ion monitoring at resolutions of 8000-10 000. The greater imprecision in response ratio (analyte/internal standard) determinations which accompanies the increase in mass spectrometric resolution is attributable to the weaker signal detected, rather than to instrument instability. The mass spectrometer has been coupled to a microprocessor-based data system and software prepared to facilitate the precise determination of response ratios. Imprecision is markedly reduced when isotope ratios are determined by linear regression analyses of signals attributable to the two ionic species detected.
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  • 129
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    Biological Mass Spectrometry 11 (1984) 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 130
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    Biological Mass Spectrometry 11 (1984), S. 428-434 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The possibilities of using combined capillary gas chromatography mass spectrometry for highly sensitive and selective determinations of enantiomeric alanines of bacterial origin have been evaluated. The alanines were separated as their diastereoisomeric N-heptafluorobutyryl-2-butyl ester derivatives on a 25 m fused silica capillary column coated with SE-54 as stationary phase. The mass spectra of the derivative obtained by chemical ionization using methane or ammonia (positive ions) and methane or Isobutane (negative ions) as reagent gases have been recorded. The highest sensitivity of detection was achieved by selected ion monitoring in the negative ion mode (detection limit about 0.8 pg). The method was tested by measuring the R-alanine content in (a) Escherichia coli cultures and (b) natural bacterial communities associated with plant roots. In (a) the recorded detection limit implied possibilities to detect R-alanine corresponding to 103-104 E. coli cells. The precision for quantifying R-alanine in the cultures was 14% (coefficient of variation). (b) demonstrated an application where the R/(R + S) ratio of alanine is low. It was shown that accurate determinations of this ratio in the picogram range could be effected down to 0.4%.
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  • 131
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    Biological Mass Spectrometry 11 (1984), S. 455-461 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pulsed positive and negative ion methane chemical ionization mass spectrometry of pyrrolizidine alkaloids is reported. Positive ion spectra are characterized by a high relative abundance of [MH]+ ions while the negative ion spectra exhibit ion peaks due to dissociative electron capture. Fragmentation in both positive and negative ion spectra primarily occurs at the ester groups with the positive charge residing with the pyrrolizidine ring system while the negative charge in contrast tends to reside with the necic acid moiety. Esterification at C-9 v. C-7 can be distinguished for non-cyclic esters of retronecine in the positive ion specta.
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  • 132
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    Biological Mass Spectrometry 11 (1984), S. 497-501 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectral fragmentation patterns of 26 N-allyl-, N,N-diallyl-, and N-cyclopropylbenzamides substituted on the acyl part with halo, methoxyl, methyl or nitro groups have been studied. All the compounds gave mass spectra containing diagnostic fragment ions which can be useful for identification purposes. Characteristic ions serving to distinguish between the two structural isomeric amide series are discussed.
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  • 133
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    Biological Mass Spectrometry 11 (1984), S. 522-528 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Competition for solvent glycerol and solute phthalic acid by the alkali metal cations Li+, Na+, K+, Rb+ and Cs+ in cationization fast atom bombardment spectra is quantited.
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  • 134
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    Biological Mass Spectrometry 11 (1984) 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 135
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    Biological Mass Spectrometry 11 (1984), S. 562-568 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron ionization mass spectra of reduced and permethylated isomeric mixtures of the major urinary tri- to deca-oligosaccharides of patients with mannosidosis are reported. Many of the oligosaccharide isomers can be differentiated in the mixtures on the basis of their distinct fragmentation patterns.
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  • 136
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    Biological Mass Spectrometry 11 (1984), S. 549-556 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Direct measurement of protein digests by fast atom bombardment mass spectrometry was examined in detail under various conditions such as with different amounts of sample and kinds of matrix. The results indicated that (i) signals of peptides covering, over 90% of the protein sequence could be detected in the mass spectrum; (ii) almost all signals of peptides including those of over 3000 u could be recorded with about 5 μg of protein digest; (iii) a peptide containing a cystine residue(s) gave the signal of the mother peptide together with that of its fragments formed by cleavage of the disulfide linkage.
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  • 137
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    Biological Mass Spectrometry 11 (1984), S. 557-561 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural differences in 13C/12C ratios of various metabolic fuels can produce systematic changes in the 13C/12C ratio of breath CO2, and therefore introduce errors into 13CO2 breath tests. To gain insight into the potential problem, we compared 13C/12C ratios of plasma macronutrients to those of breath CO2 under conditions that should alter the percentages of carbohydrate and lipid being oxidized. In rats, 48 h of starvation decreased the 13C/12C ratio of breath CO2 by 3.5‰. At this time the 13C/12C ratio of breath CO2 was very similar to that of plasma lipids. In humans, 30 min of heavy exercise increased the breath 13CO2/12CO2 ratio by 1.3‰. These changes in breath 13C/12C ratios could be predicted from 13C/12C ratios of plasma macronutrients and the percentage of carbon dioxide derived from each macronutrient, but only when compared within the same populations. For example, the 13C/12C ratios of plasma macronutrients of residents of Chicago, Illinois (USA) and Tokyo (Japan) differed by 1-3‰. An empirical correction of 13CO2 breath test data is recommended when breath tests are run under conditions that will change metabolic fuel utilization.
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  • 138
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    Biological Mass Spectrometry 11 (1984), S. 589-593 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: One of the cornerstones of an architectural approach adopted by this laboratory in screening vegetables for pesticides and industrial chemicals is the extensive use of element-selective gas chromatographic detectors followed by gas chromatography/mass spectrometry. In this particular case history, a recently introduced European fungicide, iprodione, was thought to be the first reported incidence in mache imported from France. An analytical protocol involving chemical ionization was devised to confirm this finding as well as search for possible potential metabolites.
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  • 139
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel application of Collisionally Activated Decomposition Mass analysed Ion Kinetic Energy (CAD MIKE) spectrometry to separation and positive structural identification of urinary methylmalonic acid (MMA) (the pathognomonic compound for the diagnosis of methylmalonic acidurias) is presented.CAD MIKES scans of EI ionic species at m/z 119 ([M + H]+) and m/z 101 ([M - OH]+) have been obtained from a pure standard of MMA and from crude urinary acid fractions.With reference to the procedures employed so far, the advantages of the proposed method lie in fast and simplified sample pretreatment and in a quick non-controversial response to a clinical suspicion of serious, life-threatening inherited metabolic diseases.
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  • 140
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    Mass Spectrometry Reviews 3 (1984), S. 445-477 
    ISSN: 0277-7037
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
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  • 141
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An assay for the quantitative analysis of six biologically important prostanoids based on combined gas chromatography negative ion chemical ionization mass spectrometry has been developed. Prostanoids were extracted from biological fluids by liquid chromatography on Sep-Pak cartridges and converted to pentafluorobenzyl ester derivatives. Samples were injected on capillary columan by the splitless technique and injections were made in a high boiling hydrocarbon solvent (n-dodecane) in order to minimize chromatographic run times. Quantification was carried out using selected ion monitoring of the appropriate [M-pentafluorobenzyl]- anion. The assay has been used for profiling cyclooxygenase metabolites of arachidonic acid in guinea pig lung perfusate after induction of anaphylaxis and platelet rich plasma after collagen-stimulated aggregation.
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  • 142
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    Biological Mass Spectrometry 11 (1984), S. 96-99 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As part of a continuing research program associated with the detection of anabolic steroid residues in horse urine,1-8 normal samples from entire male horses have now been investigated. Isomers of three C-18 neutral steroids; 4-estron-17-ol-3-one (1), estrane-3,17-diol (2) and an unsaturated estranediol having a possible structure (3), have been identified in urine samples from two male horses aged 8 and 14 years. Of these three steroids, compound (2) was not detected in the urine of a 2.5 yr old entire male nor in the majority of post-race urine samples from entire male horses average age 3.8 yrs (n = 34). Ten of these samples showed tentative indications of this compound. Although the isolation of isomers of estrane-3,17-diol from human non-pregnancy urine has been reported previously,9 analysis of non-pregnancy urine samples in the present study did not reveal the presence of these compounds.
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  • 143
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    Biological Mass Spectrometry 11 (1984), S. 106-113 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectrometric determination of moth pheromone components by means of selected ion monitoring with electron impact and chemical ionization has been evaluated. For the analysis of acetates, chemical ionization with ammonia as reactant gas proved advantageous with respect to sensitivity and selectivity. A quantitative assay for determination of pheromone samples from individual turnip moth females (Agrotis segetum, Noctuidae), using internal standards, deuterated at the acyl group, was developed. The assay showed correct linearity in the investigated region (20-2000 pg). Signal to noise ratios for 100 pg of acetates using chemical ionization (ammonia as reactant gas) were in the range 10-50 depending on the degree of unsaturation. Conservative limits of detection (background signal + three times the standard deviation) and quantification (background signal + 10 times the standard deviation) were approximately 70 and 240 pg, respectively. A significant decrease in gland titre of (Z)-5-decenyl acetate and (Z)-7-dodecenyl acetate after mating was established.
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  • 144
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The quantification of prostaglandin PGE2 by gas chromatography mass spectrometry in the form of an easily prepared derivative is described. After extraction and purification of biological samples the compound was derivatized in two steps to 9-enol-PGE2-methylester-trimethylsilylether, 9-enol-PGE2 -Me-TMS3. The molecular ion at m/z 582 with 40% relative abundance and the fragment ion at m/z 492 with 100% relative abundance permit a specific and sensitive evaluation in the selected ion monitoring mode. The high masses selected lie above the biological background. The calibration curve produced by adding known amounts (10-200 ng) of PGE2 to blank human urine and with (2H4)-deuterated PGE2 as internal standard gave a linear correlation. The separation from biological impurities was obtained on a 50 m glass capillary column and resulted in sharp and symmetrical peaks.
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  • 145
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metabolites of benzofenac (3-chloro-4-benzyloxyphenylacetic acid) were determined in rat, rabbit, dog, and human urine by GC/MS. Before analysis the urine was extracted and the extracts were treated with diazomethane. Deuterium-labelled benzofenac, 3-chloro-4-([methylene-2H2]-benzolyoxy) phenylacetic acid was used for the elucidation of the structures of some main metabolites and the determination of trace metabolites. The structures of the metabolites were determined from spectra obtained by electron impact and chemical ionization.
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  • 146
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    Biological Mass Spectrometry 11 (1984), S. 118-120 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The deamination of putrescine catalysed by diamine oxidase was carried out in deuterium oxide and deuterated buffers. Enamine and α,β-unsaturated intermediates were excluded, based on the observation that deuterium was not incorporated into Δ1-pyrroline during its enzymatic formation in deuterium oxide. When the reaction mixture was buffered with phosphate, isolated Δ1-pyrroline contained two deuterium atoms at C-3, indicating that a phosphate-promoted, non-enzymatic isotope exchange had occurred. Using 5,5-dimethyl-Δ1-pyrroline as a model compound, the nature of the non-enzymatic deuterium exchange was studied and a bifunctional catalysis mechanism proposed. The results suggest that the choice of buffer could alter the conclusions drawn from enzyme mechanism studies involving imine-enamine tautomerism.
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  • 147
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    Biological Mass Spectrometry 11 (1984), S. 127-131 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The urine of a young child with hypoglycemia and a Reye's like syndrome contained an excess of unusual aromatic products with a three carbon chain, phenylpropionylglycine and 3- and 4-(hydroxyphenyl)propionic and 3-(3-methoxy-4-hydroxyphenyl)propionic acids, as well as of organic acids usually found in fatty acid β-oxidation defects: the mono- and dicarboxylic acids derived from the respective (ω - 1) and ω-oxidation of C6 to C10 fatty acids.
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  • 148
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    Biological Mass Spectrometry 11 (1984), S. 132-141 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The applicability and the present limitations of the laser microprobe mass analyser LAMMA®-500 as an instrument for the structural analysis of higher molecular weight, non-volatile, bio-organic compounds (≤2000 u) were investigated. For this purpose mass spectra of various synthetic and natural compounds representing cell wall components of Gram-negative bacteria, e.g. phospholipids and lipid A-like molecules were studied. In several cases these spectra exhibited relatively simple and interpretable patterns with a prominent quasi-molecular ion originating from alkali attachment. For one group of the compounds studied - synthetic lipid A-like molecules containing a phosphate moiety - the spectra were rather complicated and lacked pronounced quasi-molecular peaks. Possible reasons for this observation are discussed.
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  • 149
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    Biological Mass Spectrometry 11 (1984), S. 145-148 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The positional isomerism of seven dodecenols (Δ5-Δ11), without any prior chemical modification, was clearly elucidated by the conventional combined gas chromatography electron impact mass spectrometry. The relative abundances of some predominant fragment ions in the isomers examined were governed by the position of the original double bond. The intensity ratios of certain selected pairs of predominant ions are of diagnostic value for the determination of the double bond position. A procedure for the location of the double bond position is given.
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  • 150
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    Biological Mass Spectrometry 11 (1984), S. 155-158 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A capillary column gas chromatographic mass spectrometric method, involving the use of a deuterated analogue as internal standard, was developed and used to identify and quantify tryptamine in the rat brain. The mean level of tryptamine i rat whole brain was 0.54 pmolg-1.
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  • 151
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    Biological Mass Spectrometry 11 (1984), S. 164-166 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extent of biliary excretion of hydroxyethyl starch (HES) in man after intravenous administration of 500 ml of a 6% solution to nine healthy male volunteers was determined using a specific gas chromatograph mass spectrometer selected ion monitoring procedure. On the average, less than 1% of the administered dose was recovered in feces over a 14 day period.
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  • 152
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron impact mass spectra of the chemical carcinogens 4-(4-aminophenyl)-2-methylaminothiazole, 4-(4-aminophenyl)-2-methylaminothiazole, and 4-(4-aminophenyl)-2-aminothiazole were studied. The 3-(4-aminophenyl)-2-substituted thiazoles were isolated from the anaerobic microsomal reduction of their respective 4-nitrophenyl analogues. Microsomes prepared from rat and rabbit kidney tissues were used. The identity of the reduction products were established by chemical synthesis and mass spectrometry. The mass spectrometric fragmentation of the nitro derivative shows prominent ions arising from the loss of the nitro group, ring enlargement of the thiazoles, and the phenylthiirene ion resulting from 1,2-cleavage of the thiazole ring. In the 4-(4-aminophenyl)-2-substituted amino derivative prominent ions result from the preferential 1,2-cleavage of the thiazole ring to give the common 2-(4-aminophenyl) thiirene ion and subsequent fragmentation of this ion.
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  • 153
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    Biological Mass Spectrometry 11 (1984), S. 159-163 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By means of laser microprobe mass analysis (LAMMA) platinum was detected in the renal proximal tubular cells of a dog that had been intravenously adminstered the antitumor drug cisplatin (5 mg per kg body weight). No definite subcellular localization of the heavy metal was obtained. Sample prparation and analytical features are examined to increase spatial resolution of analysis while maintaining sufficient detection efficiency. The LAMMA method is destructive, but the amount and type of evaporated material can readily be determined when using LAMMA in combination with transmission electron microscopy. Instrumental optimization and standardization of mass signals is possible by using platinum-loaded, ion chelating resin beads embedded and sectioned with the tissue.
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  • 154
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    Biological Mass Spectrometry 11 (1984), S. 301-307 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under ammonia and methane chemical ionization conditions, using a liquid chromatographic moving belt interface for sample introduction, molecular weight information has been observed for two representative N-phenylcarbamates, propham (isopropyl N-phenylcarbamate) and chlorpropham [isopropyl N-(3-chlorophenyl)carbamate]. Displacement reactions can occur in which the side-chain is expelled as a neutral olefin via a hydrogen rearrangement. The temperature dependence of these spectra has been studied and the relative concentration of [MH]+ ions increases with decreasing temperature.
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  • 155
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    Biological Mass Spectrometry 11 (1984), S. 308-309 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the new Finnigan moving belt liquid chromatographic/mass spectrometric interface some cardiac glycosides and oligosaccharides have been reinvestigated using C1- negative chemical ionization. Abundant [M+CI]- ions are found with all cardiac glycosides and raffinose.
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  • 156
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    Biological Mass Spectrometry 11 (1984) 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 157
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    Biological Mass Spectrometry 11 (1984), S. 310-314 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure elucidation of a novel branched-chain hexasaccharide glycoside, muscaroside B, has been aided by fast atom bombardment mass spectrometry Muscaroside A - a straight-chain analogue having the same 27-norlanostane skeleton and spirofused tetrahydrofuran ring - and digitonin - a branched-chain steroidal glycoside -  were used as standards.
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  • 158
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    Biological Mass Spectrometry 11 (1984), S. 315-319 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of fragmentation in the chemical ionization mass spectra of thermally demethylated choline esters has been investigated using various deuterated analogs of acetylcholine as models. The reagent gases employed included CH4, C2H4, NH3 and N2H3. Prominent [MH]+ or [M2H]+ ions were observed respectively in all cases. A 1,3-hydrogen rearrangement in the acetyl portion followed by loss of ketene was seen in CH4 chemical ionization spectra, as well as cleavage of the CH2—N bond after protonation on the nitrogen. Alpha cleavage produced ions analogous to the m / z 58 ion which is found as the base peak in the electron impact spectra of demethylated choline esters. A major difference between the fragmentation after electron impact and chemical ionization was seen in the m/z 72 region. The McLafferty rearrangement observed after electron impact was not found after chemical ionization. Rather, a mechanism involving protonation of the carboxyl group followed by simple cleavage of the CH2—O bond was consistent with the present results for the variously labelled analogs and reagent gases. Finally, in the chemical ionization mass spectra of demethylated acetylcholine little retention of the H+ or 2H+ was found in the observed fragment ions.
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  • 159
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    Biological Mass Spectrometry 11 (1984), S. 332-339 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Numerous abnormal metabolites were identified in large amounts in the urine of hypoglycin-treated rats using capillary gas chromatography/mass spectrometry-computer analysis. These metabolites are not detectable in significant amounts in normal rats' urine. Ten of them have not been previously associated with hypoglycin administration: these are several hydroxy compounds, including those from the valine and isoleucine pathways, 2-oxo-adipic acid, n-butyrylglycine and isovaleryl glucuronide. These results indicate that the pathways of isoleucine and valine netabolism are inhibited at their respective acyl-CoA dehydrogenation steps, as is the case for fatty acid, leucine and lysine metabolism, as previously shown. The mass spectra of the trimethylsilyl derivatives of cis, cis-4,7-decadiene-1,10-dioic, cis-4-decene-1,10-dioic, cis-4-octene-1,8-dioic acids, and (methylenecyclopropyl)acetylglycine, which were previously identified using nuclear magnetic resonance and oxidative cleavage or acid hydrolysis, are presented for the first time.
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  • 160
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    Biological Mass Spectrometry 11 (1984), S. 320-331 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metabolism of allylisopropylacetamide (AIA) (1) in microsomal preparations from phenobarbital-pretreated rats is shown to proceed by way of three cytochrome P-450-dependent pathways: (i) aliphatic (C-3) hydroxylation, (ii) allylic (C-3) hydroxylation and (iii) olefin oxidation. The latter represents the major route of biotransformation and leads ultimately to the formation of the γ-butyrolactone 2. In order to elucidate the mechanism by which AIA is converted to this γ-Iactone, and to gain information on the nature of chemically reactive intermediates in the process, the metabolism of AIA to 2 was investigated in 18O2 or H218 O and the pattern of label incorporated into the product was determined by gas chromatography/mass spectrometry (GC/MS). The results support the formation of AIA epoxide as an initial product of olefin oxidation and indicate that this species undergoes rapid intramolecular rearrangement to a protonated iminolactone which, in turn, is hydrolysed to the stable γ-lactone. On the other hand, the ‘dihydrodiol’ metabolite of AIA, which would be expected to result from direct hydrolysis of AIA epoxide, was not detected in incubation products and, furthermore, the 18O labeling data specifically exclude the possibility that it served as a precursor of 2. It may be concluded, therefore, that AIA epoxide and the protonated iminolactone to which it gives rise represent reactive intermediates in the oxidation of AIA which may play a key role in the alkylation of certain cellular constituents which accompanies metabolism of AIA by liver enzymes.
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  • 161
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    Biological Mass Spectrometry 11 (1984), S. 340-347 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A rapid, mild procedure is described for the synthesis of picolinyl esters of branched-chain, cyclic and unsaturated fatty acids, dicarboxylic acids and hydroxy acids by the reaction of the derived acid chloride with 3-pyridylcarbinol. The mass spectra of these derivatives contained abundant diagnostic ions resulting from radical-induced cleavage of the hydrocarbon chain following random hydrogen abstraction by the nitrogen atom of the pyridine ring. Ions thus represented cleavage, without further rearrangement, at each carbon-carbon bond and enabled methyl groups and double bonds to be located. The spectra of the polyenoic acids were more complex than those of their monoenoic analogues, but major ions whose mass differences could be represented by the series  - 14, 26, 14, 26, 14 -  could be used to localize the double bonds. The position of the double bond most remote from the carboxylic ester group could be established by the position of an abundant ion produced by loss of an allylic radical containing the terminal carbon atoms of the chain. Derivatives of the hydroxy acids, although not prepared in quantitative yield, also gave diagnostic spectra. The spectra of the derivatives of the dicarboxylic acids contained abundant molecular ions and again showed diagnostic cleavages of the hydrocarbon chain.
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  • 162
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements of protein and amino acid metabolism in man using stable isotopes and selected ion monitoring gas chromatographic/mass spectrometric techniques are limited by the requirement of relatively high levels of labelling for adequate precision ( 〉 0.05 at % excess). We describe here a means of extending the scope of such studies by measurement of lower levels of enrichment achieved in gaseous CO2 derived from whole blood or protein-bound amino acids following the administration of tracer amounts of appropriately labelled substrates. Construction and operation of a novel glass vacuum line required for this work are described in detail and specific applications relevant to clinical investigations are outlined. Measurements of both the total amount of CO2 and its 13C enrichment are performed in an isotope-ratio mass spectrometer which provides acceptable levels of accuracy and reproducibility for both measurements ( ±0.1% and ±0.0001 at% excess respectively).
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  • 163
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    Biological Mass Spectrometry 11 (1984), S. 353-359 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trimethylsilyl (TMS) ethers, acetates, cyclic alkane boronates (of diols) and nicotinates were evaluated as derivatives for determining the structure of n-, iso- and anteiso- long-chain alcohols and 1,2-diols. The nicotinates were the most satisfactory for both the mono- and dihydric compounds; their spectra contained a series of ions produced by radical-induced cleavage following random hydrogen abstraction from the aliphatic chain, and the differences in relative abundances of these ions reflected the position of methyl branching. In the spectra of all the derivatives studied, ions at m/z 56 and 70 were characteristic of the iso- and anteiso-structures respectively, but only in the spectra of the acetates of the monohydric alcohols were the relative abundances of these ions diagnostically useful. The cyclic alkane boronates were found to be poor indicators of chain structure. Several new fragmentations of the TMS derivatives of primary alcohols are reported.
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  • 164
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    Biological Mass Spectrometry 11 (1984), S. 360-366 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectrometric fragmentation of cyclophosphamide (CP) has been studied in detail using linked field scanning, isotope labelling, low energy ionization and accurate mass measurements. The molecular ion is of low abundance and it favours loss of HCI and ·CH2CI to form the base peak at m/z 211. All the other ions are formed by sequential fragmentation processes. The direct bond rupture between phosphorus and the N-chloroethyl group produces two ions m/z 120 and m/z 92. The ion m/z 56 is a triplet. Many of the ions in the spectrum are produced by several competing pathways. Several of the rearrangement mechanisms involve a single hydrogen transfer. Quantitative differences between two commercial CP preparations were observed in the linked field scanning spectra. Differences in the abundances of the metastable ions strongly suggest that there is an intense isomeric competition in the decomposition pathways. The experimental evidence supports the conclusion that the two CP preparations differ in their isomeric composition and these differences are related to their stereoisomers. The rates of the individual fragmentation pathways are dependent upon the isomeric structure of the parent molecule and might also be reflected by different rates of metabolism of the isomers of the drug in vivo.
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  • 165
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    Biological Mass Spectrometry 11 (1984), S. 392-395 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fast atom bombardment (FAB) mass spectrometry has been used to measure the reaction rate of trypsin with the synthetic substrate p-toluenesulfonyl-L-arginine methyl ester (TAME). Rates were measured by FAB mass spectrometry both in real time by monitoring the reaction as it proceeded on the probe inside the mass spectrometer, and also by individual analysis of a series of aliquots removed with time from a batch reaction. The results were then compared to the rates measured using the usual spectrophotometric (UV) assay run with the same reaction mixture. The results showed that the initial rates of trypsin cleavage were the same for these three methods at approximately 0.15 μmol product produced min-1 μg-1 enzyme. After 5 min, the rates determined by FAB mass spectrometry using timed aliquots and the UV assay remained about the same, whereas the real-time measurement decreased substantially to approximately 0.002 μmol product min-1 μg-1 enzyme. The results are discussed with respect to the particular advantages and disadvantages of these methods for following enzyme reactions.
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  • 166
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    Biological Mass Spectrometry 11 (1984), S. 396-399 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The computer program PAAS 3 is developed to determine the probable amino acid sequences of a peptide from sequence ion peaks experimentally obtained by mass spectrometry.
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  • 167
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    Biological Mass Spectrometry 11 (1984), S. 403-407 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure for peptide sequencing using an immobilized exopeptidase column directly coupled to a thermospray mass spectrometer is described. The amino acids sequentially released from the C-terminus of the peptide chain are directly introduced into a thermospray ion source by a flowing aqueous buffer. The buffer is essential for the direct production of ions from solution. The method eliminates the need to derivatize the amino acids for detection and, by comparison to standard injections, amino acid sequence information can be obtained in less than two minutes. With the present configuration, detection limits are typically in the low picomolar range.
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  • 168
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    Biological Mass Spectrometry 11 (1984), S. 421-427 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The components of a gas chromatographic mass spectrometric-selected ion monitoring (SIM) assay for thyroxine (T4) in human serum are described. The internal standard for the assay was synthesized from deuterium-labelled 3,5-diiodotyrosine and 3,5-diiodo-4-hydroxyphenylpyruvic acid. A novel method was developed for isolating the products of the coupling reaction. The results obtained by gas chromatography mass spectrometry SIM were compared with those of radioimmunoassay. The gas chromatographic mass spectrometric SIM assay would form the basis of a reference assay for T4.
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  • 169
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas chromatographic mass spectrometric assay for clonidine in plasma with a detection limit of a few picograms per ml was required. The p-trifluoromethylbenzyl, pentafluorobenzyl and pentafluorobenzoyl derivatives of clonidine were synthesized and the electron capture negative ion chemical ionization mass spectra of these compounds show extensive fragmentation with prominent ions at m/z 35 and 37 due to the two chlorine atoms in the clonidine molecule. Selected ion monitoring of specific high mass ions in these mass spectra indicated that the required sensitivity could not be obtained with these derivatives. Several bis(trifluoromethyl)pyrimidines were synthesized and these compounds were found to give an intense negative ion current under conditions of resonance electron capture. Consequently, a derivative of clonidine containing a bis(trifluoromethyl)aryl group was synthesized by reacting the drug with 3,5-bis(trifluoromethyl)benzoyl chloride. The negative ion mass spectrum of the reaction product has a base peak at m/z 673 and, when this ion is specifically monitored, an amount of derivative equivalent to 1 picogram of clonidine can be detected. This allowed the development of an assay for clonidine in plasma with a precision of 8% (SD) at 50 pg ml-1, 22% (SD) at 20 pg ml-1 and a lower limit for quantitative determination of 10 pg ml-1. Plasma concentrations of clonidine In 10 subjects given a single 50μg oral dose are reported.
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  • 170
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Numerous amines of biological interest can acetylated in aqueous solution, extracted and then perfluoroacylated for analysis by electron-capture gas chromatography. The structures of the products which are obtained can be confirmed by recording and interpreting their mass spectra. The electron impact mass spectral behaviour of various derivatized amines (amphetamine, ephedrine, p-hydroxyamphetamine, 3-methoxytyramine, norephedrine, normetanephrine, norpseudoephedrine, p-octopamine, 2-phenylethylamine, phenylethanolamine, pseudoephedrine, phentermine, m-tyramine and p-tyramine) is described.
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  • 171
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    Biological Mass Spectrometry 11 (1984), S. 495-495 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 172
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fast atom bombardment (FAB) is useful for the characterization of all major metabolites of the analgesic acetaminophen (APAP). It is particularly useful for providing mass spectra of the polar glucuronide and sulfate conjugates which eluded identification by field desorption and other more conventional methods of ionization. A protocol is described for the use of FAB in the identification of urinary APAP metabolites isolated by reversed phase high-performance liquid chromatography (HPLC) following therapeutic dosages of the drug. A tentative set of recommendations for the off-line use of HPLC and FAB is directed towards solving problems encountered when using these two analytical techniques in concert. In addition, a method for calculating the signal to background ratio (S/B) for analyte peaks in FAB spectra from selected relative ion intensities is proposed. Examples are presented that show the potential of S/B as an empirical parameter for judging the quality of FAB spectra.
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  • 173
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metabolism of 1,1,1,2,2-pentafluorohexane with liver microsomes from phenobarbital-treated rats gave only one metabolite, namely, the 5-hydroxy derivative. Under similar conditions 1,1-difluorocyclohexane was metabolized to give mainly the 3- and 4-hydroxy derivatives in the ratio 1:∼5.5 The structures of these metabolites were established by chemical ionization (CI) and/or electron impact (EI) mass spectrometry and confirmed by synthesis in the case of 1,1-difluorocyclohexan-4-ol. Oxidation of 1,1-difluorocyclohexane with lead tetrakis(trifluoroacetate) also gave, inter alia, the 3- and 4-hydroxy derivatives. In saturated hydrocarbons complete replacement of hydrogen by fluorine at one particular carbon will not only block microsomal hydroxylation thereat but will also inhibit hydroxylation at neighbouring hydrogen-bearing carbons, (α almost completely, β markedly, γ slightly).
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  • 174
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    Biological Mass Spectrometry 11 (1984), S. 535-538 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that a fast evaluation of field desorption mass spectrometric profiles can be obtained, using quotient spectra and calculation of quotient weight factors. The characteristics of a program developed for this purpose are described and as an example this approach has been applied to detect metabolites in urine samples.
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  • 175
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    Organic Magnetic Resonance 22 (1984) 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 176
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A temperature variation study of the nuclear quadrupole resonance (NQR) frequencies for the two resonance lines in 1,2,4,5-tetrabromobenzene was carried out in the range 77-300 K. The far-infrared spectrum of 1,2,4,5-tetrabromobenzene was recorded and the low-frequency vibrational modes noted. From the nine observed frequencies, the torsional modes contributing to the change in NQR frequencies with temperature are identified by correlating the calculated values of the NQR frequencies at different temperatures with the observed values.
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  • 177
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    Organic Magnetic Resonance 22 (1984), S. 6-10 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analysis of the 1H NMR spectra of several monothiocarbonohydrazones, some of them synthesized for the first time, shows that they exist as two structural isomers. Whereas, in general, the derivatives of aromatic aldehydes conform to a linear structure, the aliphatic carbonyl derivatives conform to heterocyclic or linear structures, depending on the size of the substituent groups. This dual behaviour is explained in terms of extended conjugation and steric hindrance.
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  • 178
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of eleven 3-N,N-dialkylamino-5,5-dimethylcyclohex-2-en-1-ones have been determined. The chemical shifts of the three sp2 carbons and of the two methylene carbons on the cyclohexenone moiety have been subjected to factor analysis. Two factors are necessary and sufficient to account for more than 93% of the total variance. The more important axis (79%) corresponds to a factor closely related to the inductive and steric effects of the alkyl nitrogen substituents. The second parameter is more difficult to interpret and could correspond to the ‘ipso effects’ of amino groups.
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  • 179
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of 28 enethiolizable β-thioxo esters and 6 enethiolizable β-thioxo thioloesters have been recorded in order to establish the tautomeric phenotypes of these compounds. All compounds investigated are essentially enethiolic. The carbonyl-conjugated (Z)-enethiol form is the exclusive or predominant tautomer of open-chain β-thioxo esters and thioloesters, thioacylmalonates and medium-sized 2-alkoxycarbonylcycloalkanethiones. The carbonyl-conjugated (E)-enethiol form is identifiable for open-chain α-unsubstituted β-thioxo esters and thioloesters, and abundant for open-chain α-substituted β-thioxo esters. Non-conjugated enethiol forms [i.e. (Z)- and (E)-isomeric β,γ-unsaturated β-mercapto esters] are abundant tautomeric constituents of ω-substituted and higher 2-alkoxycarbonylcycloalkanethiones. The chemical shifts of the carbon atoms directly involved in the tautomeric change have been rationalized in terms of substituent screening contributions. Deuterium isotope effects on the central carbon atoms of selected deuterio-enethiolic compounds have been measured in order to depict the ester group rotamerism in CO-conjugated (Z)-enethiols. The abundance of the CO-conjugated (E)-enethiols, as well as the preferred population of the non-conjugated (Z)-enethiol form relative to the non-conjugated (E)-enethiol form, is rationalized in terms of the occurrence of a no-bond interaction between the lone-pair electrons of the enethiolic sulphur atom and the ‘chelating’ methylene hydrogen atoms of cis-alkyl groups.
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  • 180
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the complexation of the (R)-MTPA (α-methoxy-α-trifluoromethyl-α-phenylacetic acid) ester of cis-4-tert-butylcyclohexanol with Eu(fod)3 is very similar to that of the corresponding trans-ester and ketones with Eu(fod)3. Further evidence is provided that the MTPA moiety exists as two different rotamers. The LIS technique, used as a tool for structure and conformation elucidation, was found by means of a Monte Carlo error analysis not to be dependent on small experimental errors.
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  • 181
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    Organic Magnetic Resonance 22 (1984), S. 29-33 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syn and anti rotamers of o-tolyl-di-tert-butylcarbinol, 2a and 2b, respectively, have been studied by 1H NMR at 200 MHz and by natural abundance 13C NMR at 50 MHz. 1H-{1H} NOE enhancement factors are consistent with the known structures and the calculated geometries of these compounds. The relaxation time, T1, of the 2-Me protons in 2b is unexpectedly higher than that for 2a. The 13C relaxation times of the 2-Me and the quaternary carbon of the tert-butyl group are also both higher in 2b than in 2a, suggesting that the rotation of these groups is faster in the less stable isomer. The activation energies for t-Bu rotation, measured by 1H DNMR, agree with this conclusion. Further confirmation is provided by theoretical calculation of the 2-Me and t-Bu rotation barriers based on Allinger's MM2 force field. Comparison of measured ΔG
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  • 182
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    Organic Magnetic Resonance 22 (1984), S. 34-38 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Assignments of the 13C NMR signals of the dammarane triterpenes, 3β,25,30-trihydroxy-(20R,24R)-epoxydammaran-16-one 3,30-diacetate (trevoagenin A diacetate) (2), its 20S-isomer (trevoagenin B diacetate) (3) and their related (20R)-3β,30-diacetoxy-16-oxo-25,26,27-trisnordammarane-24,20-lactone (4) and its 20S-isomer (5) have been achieved. Suitable tetrahydrofuran models have been synthesized in order to aid the 13C NMR assignments of the side-chain carbons of the above-mentioned compounds. The remarkable chemical shift differences observed for C-21 and C-22 between each pair of the C-20 epimers (2, 3 and 4, 5) allowed the confirmation of the C-20 stereochemistry of these ocotillol-type dammarane triterpenes.
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  • 183
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    Organic Magnetic Resonance 22 (1984), S. 47-51 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: All resolvable 13C13C Spin-Spin Coupling constants in 1- and 2-methylnaphthalene have been measured in natural abundance by the two-dimensional INADEQUATE method. The results have been interpreted in terms of HMO theory.
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  • 184
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    Organic Magnetic Resonance 22 (1984), S. 39-46 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computer-assisted method of conformational analysis for porphyrin molecules bearing flexible side-chains has been developed. The method utilizes the ring current-induced chemical shift changes of the side-chain protons which arise from the porphyrin macrocycle and any attached aryl rings. The treatment has been applied to a series of carotenoporphyrin molecules, which are important as models for a variety of photophysical processes in biological systems. Chemical shift data of sufficient accuracy for the conformational analysis were obtained from 500 MHz NMR experiments. The conformations of the carotenoporphyrins varied from extended ones with the carotenoid well away from the porphyrin ring to tightly folded species, depending on molecular constitution. The analytical method can be extended to other porphyrin-based systems.
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  • 185
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    Organic Magnetic Resonance 22 (1984), S. 52-54 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ring mobility of some 1,5-benzodiazepine-2,4-diones and 1,4-benzodiazepin-2-one has been investigated by the temperature dependence of their 1H NMR spectra. The activation parameters have been obtained, and the influence of N-1 substitution on the ring mobility is discussed, taking into account previously reported data for similar compounds.
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  • 186
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    Organic Magnetic Resonance 22 (1984), S. 55-56 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 17O NMR spectra have been obtained in the FT mode for some furan and isoxazole derivatives. The chemical shifts, mainly governed by the electronegativities of the atoms bonded to the central oxygen, are also affected by alkylation on the different positions of the ring systems, which gives rise to β and γ effects similar to those observed for simple aliphatic ethers.
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  • 187
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    Organic Magnetic Resonance 22 (1984) 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 188
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    Organic Magnetic Resonance 22 (1984), S. 61-62 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A full assignment of the 13C signals of four pentacyclic triterpenes confirms the results obtained by 1H NMR analysis of steroidal methyls, resolving the stereochemistry of the oxidation product of 3-β-acetoxyolean-12-en-30-oic acid methyl ester.
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  • 189
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    Organic Magnetic Resonance 22 (1984), S. 57-60 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The NMR spectra of the diastereomeric complexes formed by the coordination of nitrogenous enantiomeric bases with cobalt(III) meso-tetraphenylporphyrin (CoTPP) allow the immediate differentiation of these complexes. The spectra are interpreted on the basis of symmetry (RR and SS) and pseudo-chirality (RS and SR) considerations. The effects are observed in both the proton and carbon spectra and the complexes are stable in both CDCl3 and DMSO-d4 solution. This technique, in principle, allows the ready determination of the optical purity of multifunctional ligands.
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  • 190
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    Organic Magnetic Resonance 22 (1984), S. 63-66 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The intrinsic ASIS of formyl protons in p-X-benzaldehydes, dimethylformamide and diphenylformamide in a series of aromatic hydrocarbon solvents have been calculated. These values of Δ¯xα of the formyl protons present excellent correlations in aromatic hydrocarbon solvents, and are factorizable into solute and solvent factors Ux and Vα, respectively. The Ux values are linearly related to the value of σp of the substituent in the solute. The Vα values depend on the substitution pattern of the benzene ring of the solvent molecules.
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  • 191
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    Organic Magnetic Resonance 22 (1984), S. 67-74 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 14N nuclear quadrupole resonance (NQR) spectra of several nitrogen mustard compounds are reported and analyzed in the framework of the Townes and Dailey theory. For the aniline derivatives, a correlation exists between l-σ (where l is the nitrogen lone pair electron density and σ the average N—C sigma-bond electron density) and the enhanced Hammett sigma constant σ-. An improved correlation is obtained between l-σ and σR-, which emphasizes the importance of resonance effects in determining l-σ. The increase of hydrolysis and alkylation rates with increasing values of l-σ is in agreement with the identification of the aziridinium ion as the intermediate in aromatic nitrogen mustard hydrolysis and alkylation. A possible correlation is noted between the 35Cl NQR spectra for some of the mustards and measures of toxic and antitumor activity.
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  • 192
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    Organic Magnetic Resonance 22 (1984), S. 80-85 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organometallic rhodium(I) derivatives have been studied by 103Rh NMR. The chemical shift range extends from 609 ppm ([Rh.cp.cod]) to 2714.7 ppm ([Rh.fod.cod]). These results are supported by 13C and 31P NMR results, and give information about the bonding in these derivatives. Most of the complexes contain the cycloocta-1,5-diene ligand. For these complexes a linear correlation is observed between δRh and δC (olefinic carbons) (27 points, R = 0.960). For the phosphine derivatives a linear correlation is found between δRh and 1J(RhP) and, also, between δRh and parameters characterizing the basicity of the phosphine ligand. The correlation of δRh with ligand properties has been extended to a wider range of complexes by using the ‘influence parameters’ defined previously (10 points, R = 0.947). The sensitivity of δRh to steric factors is also proved.
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  • 193
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    Organic Magnetic Resonance 22 (1984), S. 86-89 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of four ortho- and seven para-quinone methides were assigned using chemical shift and long-range carbon-proton coupling information. The carbonyl shifts are compared with those in ortho- and para-benzoquinones. The chemical shifts of the carbonyls of the p-quinone methides are observed at δ 186.2-186.4 for the three ortho-di-tert-butyl-substituted compounds and at δ 180.7-181.5 for the four ortho-oxy-substituted compounds. In the three o-quinone methides with meta, para-dioxy substituents, the carbonyl signals are at δ 184.2-185.4. The carbonyl signal of the one o-quinone methide with no oxygen substitution is shifted downfield to δ 200.9, apparently as a result of hydrogen bonding to the nearby hydroxyl.
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  • 194
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    Organic Magnetic Resonance 22 (1984), S. 75-79 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton magnetic resonance (1H NMR) was used to study cis-trans isomerization in N-methyl-N-(1-methylthio-2-propenyl)formamide and N-benzyl-N-(1-methylthio-2-propenyl)formamide, two analogs of the thiol form of thiamine. Benzene dilution studies and shift reagent studies were used to make resonance assignments, which indicate that the predominant isomer for each analog has the C—C bond trans to the carbonyl oxygen. Shift reagent studies, using Pr(fod)3 in CCl4 or CDCl3, suggest that the reagent may be bonding to both the nitrogen and oxygen atoms of the substrate. For some of the systems studied, varying ρ at constant temperature had the same spectral effect as varying temperature at constant ρ.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 195
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 22 (1984), S. 90-92 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some shielding calculations, using Pople's SOS model, are reported for B, C, N, F, P and Si as a function of changes in bond length and pyramidal bond angle. In all cases considered, the shielding is predicted to decrease as the bond length increases, which is in line with the available experimental data. The observed temperature variation of the nitrogen and phosphorus shieldings of NH3, PH3 and PF3 could be accounted for by a decrease in the pyramidal angle at higher temperatures. A similar angular variation for NF3 is predicted to cause a shielding variation, with temperature, in the same sense as that reported for NH3 and PH3, but opposite to that for PF3.
    Additional Material: 2 Tab.
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  • 196
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    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 22 (1984), S. 114-116 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of tetraalkyl-porphyrin and -chlorin complexes of nickel(II) were studied. The 13C NMR of (5,10,15,20-tetramethylchlorinato)nickel(II) supports the model of asymmetric charge distribution in this chlorin, as derived from the structure analysis and from previous proton NMR studies.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 197
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of nine dichlorinated bicyclo[2.2.1]heptanes (norbornanes) have been measured and assigned. The pairwise effects of chlorine substituents which cause deviations from the additivity of single-substituent effects were investigated and are discussed. The largest effect found is the high-field shift of carbons bearing vicinal cis substituents. In the case of geminal substitution deviations from additivity were found to be to low field and large in the γ, smaller in the β and negligible in the α chemical shifts. The observed deviations for 1,3-disubstituted cases vary from -3.2 to +1.1 ppm at different carbons, allowing no simple explanation. Replacement of α-hydrogen in a diaxial 1,3-arrangement by CH3, OH or CI causes the single substituent effect, namely the γa effect, to change considerably.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 198
    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.
    Type of Medium: Electronic Resource
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  • 199
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 22 (1984), S. 127-128 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C and 15N NMR chemical shifts and 13C-31P and 15N-31P coupling contants are reported for a series of ten 4-substituted-1-dimethylphosphonopiperazines.
    Additional Material: 1 Ill.
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  • 200
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 22 (1984), S. 125-127 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13NMR data recorded in the pulsed Fourier transform mode are re- ported for 1- and 2-naphthyltrimethyl- stannanes and 9-phenanthryltrimethyl- stannane. Assignments of ring carbon resonances are based on magnitudes of tin-carbon spin-spin coupling constants, substituent chemical shifts, spin-lattice relaxation times and proton coupled spectra.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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