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  • Artikel  (14)
  • Analytical Chemistry and Spectroscopy  (14)
  • 1990-1994  (14)
  • 1955-1959
  • 1
    Digitale Medien
    Digitale Medien
    A new approach to confirmation by infrared spectrometry (1990)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 4 (1990), S. 61-77 
    Details
    ISSN: 0886-9383
    Schlagwort(e): Infrared ; Spectroscopy ; Spectrometry ; Retrieval ; Confirmation ; Chemometrics ; Adequate peaks ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In the series of analytical techniques for identification of chemical substances, infrared spectrometry presents by far the highest information content. However, the information is most complicated too. It concerns a multitude of band positions, band intensities and band shapes, which, moreover, can be disturbed by matrix and other effects. The high redundancy, however, allows conclusions to be made by a qualitative, subjective procedure.IR is often used to prove the equality between a sample and a reference material, e.g. in quality control of a production process. In forensic control, the question to be answered is mostly not to prove equality, but whether or not the presence of a compound in a sample, e.g. a drug, can be proved. Moreover, testing has to be performed according to objective rules.To fulfil these requirements, a new retrieval algorithm, the ‘Adequate Peaks Search’, is presented. It concerns representing the reference spectra by sets of adequate peak positions and the sample spectrum by a set of all peak positions, whereafter the cross-sections of the sample set and the reference sets are determined. The concept ‘adequate peak’ is defined and criteria have been formulated to evaluate the results into a positive (presence of the analyte is proved) or negative (presence is not proved) conclusion.The detection limit when the Adequate Peaks Search (APS) method was applied was four to seven times lower than that attained by a number of experts.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cem.1180040108
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  • 2
    Digitale Medien
    Digitale Medien
    Electron impact mass spectra of synthetically modified milbemycinsFor a preliminary account of this work, see Ref. 1. (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 635-642 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The potent endectocide 23-(O-methyloximino)-F28249α and related compounds were identified and characterized by mass spectrometry. The fragmentation pathway of 23-(O-methyloximino)-F28249α was identified by its high-resolution mass spectrum and the electron impact unit mass spectra of its homologs. This fragmentation pathway is presented and discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210280527
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  • 3
    Digitale Medien
    Digitale Medien
    Inverse two-dimensional 31P, 103Rh{1H}NMR of cationic rhodium(I) complexes containing chelating diphosphines (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. S118 
    Details
    ISSN: 0749-1581
    Schlagwort(e): 103Rh NMR ; 31P NMR ; Inverse 2D NMR ; Square planar ; Cation ; Diphosphine ; Paramagnetic shift ; Chemical shift correlation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of new and known Rh(I) complexes [Rh(R2P(CH2)nPR2)2]Y and [Rh(diene)(R2P(CH2)nPR2)]Y (R = Me, Et, Ph, C6F5, C6H4CF3; Y = Cl, ClO4, PF4, BF4, OSO2CF3; diene = norbornadiene, cyclooctadiene) were prepared and their 103Rh NMR spectra were recorded on a 100-MHz spectrometer by using inverse two-dimensional 31P, 103Rh{1H} NMR. This technique provides quick access to 103Rh NMR data (2-8 h for ca. 0.1 M samples) when dealing with Rh-phosphine complexes. The 103Rh NMR data are discussed. All δ(103Rh) of the cationic Rh(I) complexes appear at the lower frequency end of the Rh(I) range, i.e. between -1350 and + 200 ppm, which is in agreement with the fact that the Rh shift is determined by σp and with a large ΔE in square-planar d8 complexes. The relative change in ΔE between complexes is not large and the changes in paramagnetic shift for these complexes are essentially determined by their relative σ-donor capacities. δ(103Rh) shows an inverse correlation with δ(31P), which was rationalized by invoking the chelate ring size containing the Rh centre and the bidentate phosphine ligands.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260291320
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  • 4
    Digitale Medien
    Digitale Medien
    Characterization of a synthetic 37-residue fragment of a monoclonal antibody against herpes virus by capillary electrophoresis/electrospray (ionspray) mass spectrometry and 252Cf plasma desorption mass spectrometry (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1994), S. 346-352 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A peptide comprising 37 amino acids of the antigen binding site of a monoclonal antibody directed against glycoprotein D of herpes simplex virus was synthesized. The synthetic peptide and the impurities formed in the synthesis were characterized by capillary electrophoresis/ionspray mass spectrometry and by 252Cf plasma desorption-time of flight mass spectrometry. The measured average molecular mass of the synthetic peptide was 4627.16 Da, which was only 0.08 Da higher than the calculated value (4627.08 Da). The plasma desorption mass spectrum of the synthetic peptide showed a protonated molecule at m/z 4624.1, which was 4 Da lower than the calculated one (4628.09 Da). The amino acid sequence of the peptide was confirmed in part by electrospray (ionspray) mass spectrometry using a high nozzle skimmer voltage difference. Five impurities were separated and identified by capillary electrophoresis/mass spectrometry and two of them also appeared in the plasma desorption mass spectrum.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200230608
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  • 5
    Digitale Medien
    Digitale Medien
    Phenolic acids dimers in the cell walls of barley (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1994), S. 71-74 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Using gas chromatography/mass spectrometry we have observed six peaks in the single ion chromatograph at m/z 674 of the alkaline extract of barley straw cell walls. The breakdown pattern of these ions suggests that they could all be isomers of 5,5′-bis-dehydroferulic acid. Since only the 5,5′ linkage is reported to be present in plants this tentatively suggests that these compounds exhibit stable orientational isomerism about this bond. Plausible breakdown mechanisms are presented which allow for the complete assignment of structure to all the isomers. These mechanisms suggest that the two pairs of breakdown ions at m/z 556 and 467, and 265 and 193 are representative of trans and cis double bonds, respectively.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200230205
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  • 6
    Digitale Medien
    Digitale Medien
    Identification of cyclobutane-type dimers of substituted cinnamic acids by gas chromatography/mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 46-53 
    Details
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Substituted cinnamic acids were dimerized, under fluorescent or UV light, as a glassy coating on a vial then subsequently analysed by GC/MS. Mass Spectrometric analysis of the dimers formed by each acid allowed the assignment of the dimer as a truxillic or truxinic structure since these structures had distinctive fragmentation patterns; the breakdown of the truxillic acids involves a McLafferty rearrangment before fragmentation occurs, whereas the truxinic acids, which have both carboxy groups on one side and both aromatic groups on the other, fragment asymmetrically to give characteristic stilbene and dicarboxylate fragments. It is apparent from the results of the dimerization of the lcinnamic acids that, under the conditions used here, if the monomeric acid had the capacity for hydrogen bonding using the ring substituent as well as the carboxy group, the dimerization products would be overshelmingly truxillic in structure. However, if only the carboxy group could hydrogen bond, the products would be almost exclusively traxinic in structure.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/rcm.1290060110
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  • 7
    Digitale Medien
    Digitale Medien
    Application of dicyandiamide as a matrix additive in fast atom bombardment mass spectrometry (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 25 (1990), S. 317-322 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Dicyandiamide (DCDA) is used as a chemical additive in the fast atom bombardment (FAB) matrix 3-mercaptopropane-l,2-diol (thioglycerol) and propane-l,2,3-triol (glycerol). It is demonstrated that DCDA can be used to generate adduct ions [M + H + DCDA]+ for a variety of common organic functional groups to confirm the molecular ion [M + H]+. It is particularly useful for aromatic and alkyl amines and these compounds were therefore investigated in greater detail. Primary and secondary amines on heating react with DCDA to produce biguanides. DCDA can be used as a derivatizing reagent, but the reaction times are typically longer than 12 h and, therefore, it has limited utility. Biguanides can be detected at the nanogram level in full-range FAB mass spectral analysis.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210250606
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  • 8
    Digitale Medien
    Digitale Medien
    Solution and solid phase 13C NMR studies of cyclic and acyclic 1,2-dialkoxybenzenes and their mononitro derivatives (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 1094-1095 
    Details
    ISSN: 0749-1581
    Schlagwort(e): 13C NMR ; Solid-state NMR ; CP/MAS ; Dioxygenated benzenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 13C NMR chemical shifts are reported for 1,2-dimethoxybenzene (veratrole) and related benzodioxane, benzodioxepane and benzodioxenane systems and their 4-nitro derivatives in solution and in the solid state. Results are discussed in terms of the stereoelectronic influence of substituents.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260311214
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  • 9
    Digitale Medien
    Digitale Medien
    Structure elucidation and proton and carbon-13 assignment of a pentasaccharide glycoside from Agave americana (1994)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 213-219 
    Details
    ISSN: 0749-1581
    Schlagwort(e): Tigogenin ; DQCOSY ; TOCSY ; HMQC ; HMBC ; Selective reverse INEPT ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A glycoside extracted from the rhizomes of Agave americana was identified as 3-O-[{{β-D-xylosyl(1 → 3)}{β-D-xylosyl(1 → 3) - β - D - glucopyranosyl(1 → 2)} - β - D - glucopyranosyl(1 → 4)} - β - D - galactopyranosyl] - (25R) - 5α - spirostan-3β-ol by concerted use of proton and carbon-13 2D NMR methods. Complete assignments for the sugar resonances were obtained with standard methods, but the presence of chemical shift degeneracies prevented an unequivocal determination of two of the glycosidic linkage points by the HMBC experiment. Further two-dimensional experiments failed to resolve the ambiguity, but a clear identification of the linkages was obtained using a selective reverse INEPT experiment with homonuclear double resonance.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260320405
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  • 10
    Digitale Medien
    Digitale Medien
    1H and 13C NMR spectra of pseudomorphine and dimethylpseudomorphine (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 1018-1022 
    Details
    ISSN: 0749-1581
    Schlagwort(e): Pseudomorphine ; Dimethylpseudomorphine ; 1H and 13C NMR ; Chemical shift assignments ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 1H and 13C NMR spectra of 7,7′,8,8′-tetradehydro-4,5:4′,5′-diepoxy-17,17′-dimethyl-[2,2′-bimorphinan]-3,3′,6,6′-tetrol; [2,2′-bimorphine] (pseudomorphine) and 7,7′,8,8′-tetradehydro-4,5:4′,5′-diepoxy-17,17′-dimethyl-[2,2′-bimorphinan]-3,3′-dimethoxy-6,6′-diol; 2,2′-bimorphine (dimethylpseudomorphine) were measured and assigned using DEPT, COSY, HETCOR, NOESY, NOE difference techniques and selective proton decoupled carbon NMR experiments.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260281204
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