摘要:

AbstractA series of very large all‐carbon molecules has been successfully extracted with quinoline from fullerene‐rich carbon soots produced by the vaporization of graphite in a helium atmosphere using the contact are method. The present extracts (black powder) were found not to be soluble either in benzene or toluene, which are normally used as extraction solvents for C60and C70. The secondary ion mass spectrum (SIMS) of the extracts reveals that they contain a series of even‐numbered gigantic carbon molecules C70+2n(n⩾1) up to at least C500. The SIMS spectra exhibit a remarkably wide distribution of carbon molecules which has a broad maximum at around C130‐C150. The possibility of the isolation of such large carbon molecules, which are possibly fullerenes, is also

ISSN:0951-4198    

DOI:10.1002/rcm.1290060702

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractMethod of multivariate statistical analysis have been applied to the mass spectra of pyrrolidin‐1‐yloxy derivatives. A graphical representation of the results obtained by using fragment‐specific features proides a staightforward method of visualizing mass spectra/structure relationships. The explanatory power of the relatioonships can be assessed by finding linear discriminant components in the space of fragement‐type features. Computer‐generated spectral‐type features, when used as spectral classifiers, show statistilcally comparable performance on the same set of m

ISSN:0951-4198    

DOI:10.1002/rcm.1290060703

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractA gas chromatography/mass spectrometry (GC/MS) method for measuring very low levels of enrichment of d5‐phenylalanine (0.002–0.09 atom percent excess) is described. This method makes it possible to determine the enrichment of amino acid incorporated into tissue protein during studies of protein synthesis in man. Phenylalamine is enzymatically converted to phenylethylamine and the d5‐enrichment is measured in the heptafluorobutyryl derivative by selective‐ion recording under electron ionization conditions. The coefficients of variation for muscle‐protein hydrolysate samples enriched with d5‐phenylalanine at the 0.005 and 0.05 atom percent excess levels were 6.0 and 1.2%, respectively. This precision at low enrichment and the small amount of contrast to the conventional approach which uses GC/MS for plasma amino acids (typically 2–20 atom percent excess) but gas isotope‐ratio mass spectrometry for protein‐bound amino acids, the enrichment of both plasmafree and protein‐bound d5‐phenylalanine can be measured wit

ISSN:0951-4198    

DOI:10.1002/rcm.1290060704

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractIon/molecule reactions in nitrotoluene/NO and nitroluene/OCS systems were studied in an ion cyclotron resonance mass spectrometer. The formation of an adduct ion between m‐nitrotoluene and NO (or OCS to a lesser extent) differentiates it from theo‐ andp‐nitrotoluene isomers can be distinguished by their different decomposition rates into C7H6NO+and C7H6NO+fragment

ISSN:0951-4198    

DOI:10.1002/rcm.1290060705

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractThe kinetics fo production of proton‐bound dimers of dimethyl‐ and diisopropyl‐tartrate were analyzed were analyzed by the method of initial slopes. From the pressure dependence of the apparent bimolecular rate constatn, the back‐dissociation rate and radiative stabilization of the intermediate excited collision complex was calculated. The back‐dissociation (10.3 and 2.8 × 103s−1) and radiative (8.2 and 7.1 s−1) rates are compared to literature values for functionally similar acetone. In contrast to acetone these dimers exhibit a back‐dissociation reaction to regenerate the monomer species. These results can be taken to imply a lower binding energy in these dimers due to steric effects. Competing reactions to form ions ofm/z145 and 235 were also observed for the dimethyl and diisopropyl est

ISSN:0951-4198    

DOI:10.1002/rcm.1290060706

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractDaughter‐ion spectra obtained by ion‐trap mass spectrometry have been successfully employed in the field of drug abuse investigation. Selection and collison‐induced fragmentation of molecular‐ion species of morphine and cocaine lead to an easy identification of such molecules in hair extracts of heroin and cocaine

ISSN:0951-4198    

DOI:10.1002/rcm.1290060707

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractHigh‐resolution double‐charge‐transfer spectroscopy has been used to measure the double‐electron‐capture reactions with CH4. Using kilo electron volt OH+, CI+and F+projectile ions it is possible in double‐electron‐capture reactions with CH4molecules to populate the ground triplet state of CH 42+. The energy of this state relative to the gound state of CH4is found to be 38.2±0.4 eV, while the fiest excited triplet state is found at a double‐ionization energy of 46.7±0.8 eV. In double‐electron‐capture reactions involving H+projectile ions and CK4molecules, low‐lying singlet states of CH 42+are populated. The energies of the four lowest singlet states in CH 42+were measured to be 39.2±0.4, 40.5±0.4, 42.1±1 and 51.0±1 eV. High‐resolution photon‐induced Auger‐electron spectra of the CH4molecule have been recorded. The KLL Auger Spectrum shows four distinct structures in the 30–70 eV double‐ionization evergy range centred at 40.3±0.1, 47.03, 53.2±0.3 and 6.9±0.3 eV. The previou

ISSN:0951-4198    

DOI:10.1002/rcm.1290060708

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractIon‐trap chemical‐ionization performance has been imporved by application of a modified scan function for the rejection of the undesired electron‐ionization‐like (EI‐like) ions formed at the beginning of the reaction ionization period. The net effect of this software modification to the automatic reaction control is to produce chemical ionization (CI) spectra that are no longer adulterated with conventration‐dependent EI‐like ions. Under such improved conditions, CI spectra from an ion trap can now be dirctly compared with CI spectra produced on conventional quardrupole and magnet‐scann

ISSN:0951-4198    

DOI:10.1002/rcm.1290060709

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractIsomeric glycerophosphatidylcholine molecular species containing fatty acyl chains differing by 2 Da (1‐stearoyl‐2‐oleoyl‐ and 1‐oleoyl‐2‐stearoyl‐sn‐glycero‐3‐phosphocholine) can be identified by the determination of trhe fatty acid chain esterified to the sn‐1 position in the glycerol backbone based on the electric sector voltage differences of [M‐86‐R2COOH]−anions derived from phosphatidic acid parent ions (M minus choline group) produced by negative‐ion fast‐atom bombardment combined with mass‐analyzed ion kinetic evergy analyses. Three volt differences can be observed in the spectra. The study further demonstrates that this approach is also effective in distinguishing such molecular species as isomers of glycerophosphatidic acid, glycerophosphatidyl‐ethanolamine and glycerophosphatidylserine and in characterizing the molecular species, differing by 2 Da, of the bovine brian glycerophosphatidylserine (1‐stearoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphoserine) and the rabbit kidney glycerophos‐phatidylethanolamine (1

ISSN:0951-4198    

DOI:10.1002/rcm.1290060710

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractNovel aspects of utilizing RF‐only pre‐filters in a quadrupole mass spectrometer are presented. Theoretical considerations converning the optimization of the spectrometer by means of the pre‐filter length and the ion entrance velocity are given and are given and are compared with the results of model calculations. Experimental results are shown to illustrate the advantages of the setup constructed according to the proposed optimization method over both the single mass filter and one with a pre‐filter of conventional length range. The most effectively focusing pre‐filters are shown to have integer multiples of an elementary length. The predictions have only been verified experimentally for helium. Apoproximeately 150% improvement was measured for helium transmission with respect to the single analyser with the suggestede parameters. Since the resolution always inporoves with length at a certain ion velocity, it is preferable to make use of some of the higher local minima of the suggestede optimizing

ISSN:0951-4198    

DOI:10.1002/rcm.1290060711

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY