摘要:

AbstractAddition of a hydroxy‐containing matrix to an aldehyde was observed in fast‐atom bombardment (FAB). This FAB‐induced interference reaction, observed in the case of a microbial alkaline protease inhibitor, shows a characteristic time behaviour. This can be explained by a first‐order reaction kinetics scheme which leads to quilibrium, for which rate and equilibrium constants were also determined. These data suggest that in situ reaction kinetics can be studied by FAB mass spect

ISSN:0951-4198    

DOI:10.1002/rcm.1290050102

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractIon‐structure investigation of the [MH]+ions from chalcone has been carried out by collision experiments performed with an ion‐trap mass spectrometer (ITMS), operating with the application of a supplementary RF voltage. The data so obtained, together with those achieved by comparison with labelled model compounds, have led to a clear identification of the [MH]+ion structure, proving the high potentialities of the ITMS in such

ISSN:0951-4198    

DOI:10.1002/rcm.1290050103

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractThe coupling of gas chromatography/mass spectrometry provides the most useful technique for structure elucidation and quantitative analysis of organic compounds in environmental samples. The technique finds its application in all environmental media: air, water, wastes, soil, particularly in connection with reliable sampling and sample preparation. Alternative separation and ionization techniques are used in practice on special occassions, such as the assessment of the health hazard caused by an unknown compound, when structure elucidation cannot be performed by the standard gas chromatography/mass spectrometry equipment.

ISSN:0951-4198    

DOI:10.1002/rcm.1290050104

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractAll‐electron,ab initiomolecular orbital calculations have been performed on electronic states of CH 42+using perturbative configuration interaction procedures and large sets of Gaussian basis functions with a view to attempting reconciliation between contemporary quantum‐chemical information and different sets of experimen‐tal data from charge‐stripping, threshold photoionization, and double‐charge‐transfer mass spectrometry. Metastable electronic states of CH 42+are predicted for D4hand D2dsymmetries, with charge‐stripping experiments likely to populate spin singles of the former symmetry. Investigation of the dissociation of CH 42+(D4h) to CH 3+(D3h)+ H+along the C2vsymmetry pathway indicates that theoretical and experimental data on metastable states of this dication are in accord only if non‐Frank‐Condon t

ISSN:0951-4198    

DOI:10.1002/rcm.1290050105

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractA new, attractive application of the phase‐system switching (PSS) technique is demonstrated. The PSS system is used in combination with liquid chromatography coupled to continuous‐flow fast‐atom bombardment mass spectrometry (LC/CF‐FABMS) to achieve flow‐rate reduction from 1.0 mL/min in the high‐performace liquid chromatography (HPLC) system to 15μL/min going into the mass spectrometer. In PSS, a compound of interest, in this case erythromycin 2′‐ethylsuccinate, is enriched after the analytical separation, on a short trapping column, from which it is desorbed subsequently to the LC/MS interface. Optimal mobile phases and flow‐rates can be used for the HPLC separation as well as for the mass spectrometric detection. Desorption of the analyte is achieved either by using a flow‐rate of 15 μL/min without a splitter or a flow‐rate of 230 μL/min with a splitter. Compared to the LC/CF‐FAB MS methods using a conventional bore HPLC column and a splitter, improved detection limits for the model compound were ach

ISSN:0951-4198    

DOI:10.1002/rcm.1290050106

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractA numerical method has been developed to obtain the kinetic energy release distribution from a mass‐analysed ion kinetic energy peak profile for a metastable ion decomposition occurring in a collision cell floated at high voltage. The method has been applied to the unimolecular dissociation of thetert‐butylbenzene molecular ion. The kinetic energy release distribution thus obtained was nearly invariant to the applied voltage. Peak tailing due to dissociation in the field region could be reproduced adequately The method may be useful for the investigation of unimolecular ion decomposition in narrow time‐ and energy‐

ISSN:0951-4198    

DOI:10.1002/rcm.1290050107

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

Abstract2,3‐dihydroxypropyl benzyl ether, a glycerol derivative, is a suitable matrix for fast‐atom bombardment analysis. It has been shown to be superior to glycerol and thioglycerol for the detection of molecular ions of cobyra

ISSN:0951-4198    

DOI:10.1002/rcm.1290050108

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractA new ionization technique based on a modification of the conventional plasma‐desorption mass spectrometric apparatus is described. An electron avalanche produced by the microchannel plates of a secondary electron multiplier is found to desorb a sufficient amount of (quasi‐)molecular ions of non‐volatile thermally labile molecules. Spectra of several substances with molecular masses up to 1250 u are presented. The mechanism of electron avalanche desorption is now under investig

ISSN:0951-4198    

DOI:10.1002/rcm.1290050109

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractAcetone chemical ionization mass spectra of cycloalkenes clearly show the operation of transannular interaction in medium sized rings in the form of water loss from [M + 43]+adduct ions. Based on labelling studies a mechanism has been proposed.

ISSN:0951-4198    

DOI:10.1002/rcm.1290050110

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractThe effusion method, together with mass spectral analysis, has been used to study ion/molecule equilibria involving the negative ion BF 4−. The experimental data obtained have made it possible to calculate enthalples for the reactions:and the enthalpy of formation ΔHf(BF 4−, 298) as ( −1716±8) kj/mol. The fluorine anion affinity of BF3has been determined as FA((BF3)g, 298)=(331±8)kj/mol−1and compared with L

ISSN:0951-4198    

DOI:10.1002/rcm.1290050111

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY