摘要:

AbstractThe single‐ionization energies of the free radicals CF2Cl˙and CFCI2˙have been measured by double‐charge‐transfer spectroscopy. The values obtained were 9.0 ± 0.5 eV and 8.5 ± 0.5 eV for CF2Cl˙and CFCl2˙, r

ISSN:0951-4198    

DOI:10.1002/rcm.1290030902

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractFast‐atom bombardment mass spectrometry has been used to obtain spectra of conjugated benzo(a)pyrene (bap) metabolites using a 1:1, glycerol+thioglycerol matrix. bap Glucuronides give positive‐and negative‐ion spectra with peaks due to [M + H]+and [M − H]−ions and a Major fragment peak (base peak) at [bapOH]+and [bapO]−. bap Sulfates (sodium salts) give similar negative‐ion spectra with [M − Na]−and [bapO]−peaks, but the positive‐ion spectra are dominated by sodium and glycerol

ISSN:0951-4198    

DOI:10.1002/rcm.1290030903

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractThe observation of sharp limits to the chain lengths of alkyl cations derived by low energy collision‐induced dissociation of isotopically labelled trimethyltetradecylammonium cations, as well as the selectively limited scrambling of its isotope label, has prompted the proposal of a new mechanistic model for alkyl cation fragmentation. The model invokes protonated cyclopropane intermediates which may reopen to branched structures, or fragment (if suitably substituted) to form smaller alkyl cations and neutral olefins. The model accounts completely for the absence of daughter ions with fewer than three or more than six carbon atoms, while its semi‐quantitative application provides a reasonable match to the observed isotope scrambl

ISSN:0951-4198    

DOI:10.1002/rcm.1290030904

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractThe ion PhSiH 2−undergoes a number of fragmentations upon collisional activation, including losses of H˙, H2(mainly to form PhSi−), and SiH2, together with formation of HSi−. The ion/molecule chemistry of PhSiH 2−is characteristic of silyl anion systems and bears no analogy to that of benzyl anion reactions; for example with N2O and CO2it forms Ph(H)2SiO−as the sole ionic product, while with CS2it yie

ISSN:0951-4198    

DOI:10.1002/rcm.1290030905

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractA method employing liquid secondary‐ion mass spectrometry (SIMS) in conjunction with metastable‐ion measurements (linked scanning at constant B/E) to obtain sequence‐specific information for three synthetic polyamine isomers was developed. The normal liquid SIMS spectra gave molecular weight information, but important sequence ions were of low intensity or obscured by the background. The metastable‐ion spectra contained important fragment ions in particular due to cleavage along the polyamine chain. One of the three synthetic isomers was identical with a toxin present in the venom of the digger wasp. In conjunction with nuclear magnetic resonance spectroscopic studies, this should be a powerful method for the structural characterization of other closely related toxins present in the venom of th

ISSN:0951-4198    

DOI:10.1002/rcm.1290030906

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractPreliminary results obtained with a home‐made Fourier transform ion cyclotron resonance mass spectrometer on the sequential clustering reactions of silane using yttrium cation activation are reported. [YSinH2n]+and [YSinH2n−2]+ions are formed. So far, we have observed these ions up ton=7, and a sequential clustering mechanism is proposed. The ion structures are characterized by collision‐induced dissociation, and kinetic measurements to determine the formation and decay rates of each ion are perf

ISSN:0951-4198    

DOI:10.1002/rcm.1290030907

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractA technique for the simplification of fast‐atom bombardment (FAB) spectra of polysulfonic acids, especially azo dyes complicated by sodium, is discussed. The sodium may be present as the sulfonate salt or the salt may be formed during FAB analysis from impurities present in the sample. The incorporated sodium as well as other impurities which may be present in commercial samples are removed by means of a simple cationic‐exchange‐resin procedure, yielding simplified and unambiguous FAB spectra of the sodium‐free m

ISSN:0951-4198    

DOI:10.1002/rcm.1290030908

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractNegative‐ion fast‐atom bombardment linked‐scan spectra at constant B/E have been shown to allow differentiation of the linkage position in hexose‐hexose‐disaccharides. Sequence information can also be obtained when there is a molecular weight difference between the monosaccharide units in the carbohydrate

ISSN:0951-4198    

DOI:10.1002/rcm.1290030909

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractReaction‐intermediate spectra are reported for peptide mixtures using a hybrid BEQQ and a pentaquadrupole mass spectrometer. In this extended tandem mass spectrometry scan, the protonated molecule and a terminal fragment ion are selected with the first and third mass analyzers, respectively. A subsequent linked scan at constant B/E (hybrid instrument) or a scan of the middle quadrupole (pentaquadrupole instrument) produces the reaction‐intermediate spectrum. The resulting spectra are simpler than conventional tandem mass spectrometry daughter‐ion spectra and display only sequence ions of one group, viz. A, B and C or X, Y and Z. This information facilitates structural elucidation and is obtainable on nanomole amounts of pe

ISSN:0951-4198    

DOI:10.1002/rcm.1290030910

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractCrystalline Ce(C5H7O2)4has been synthesized directly from the reaction of hydrated cerium(IV) oxide with acetylacetone, (C5H8O2), and its electron‐ionization (EI) mass spectrom is reported. The compound exists as a monomer (mass 536) in the gaseous state. The mass spectrum, like those of M(C5H7O2)4(M = Zr or Th) and CeL4(L = fluorinated β‐diketonate), shows the dominant ion signal to be due to the [Ce(C5H7O2)3]+ion that arises from the loss of one C5H7O2from the molecular ion. An internal electron‐transfer affords [Ce(C5H7O2)3]+˙. Fragmentation of [Ce(C5H7O2)3]+˙ to [Ce(C5H7O2)2]+is similar to that observed for the tris‐chelates of trivalent transition metals and La(C5H7O2)3. The ion [Ce(C5H7O2)2]+ultimately breaks down to [CeO]+through the sequential loss of three even‐electron neutral species, CH3COCHCCH2, H2O and CH3COCHCCH2without invoking any further reduction of the Ce centre. Mechanisms are given for the loss of the three even‐electron species from the bis(acetylacetonato)cerium(III) ion fragment. Theoretical simulations of patterns of the fragment ions [Ce(C5H7O2)3]+˙, [Ce(C5H7O2)2]+˙, and [Ce(C5H7O2)OH]+have been made and compared with those of the corresponding experimental results in support of the suggested mode

ISSN:0951-4198    

DOI:10.1002/rcm.1290030911

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY