摘要:

AbstractWe report on the first application of Fourier‐transform ion cyclotron resonance mass spectrometry to the very highly charged ions produced in the high‐energy electron beam ion trap (SuperEBIT) at the Lawrence Livermore National Laboratory. Initial results are described, and spectra are presented from ions as highly charged as Cs

ISSN:0951-4198    

DOI:10.1002/rcm.1290080202

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractCharge‐state distributions in the positive‐ion electrospray (ES+) mass spectra of some proteins are monitored at various temperatures of the ion source. The observed shifts in charge‐state profiles favouring higher charge‐states are linked to heat‐induced conformations cited by other research groups. To gain more insight into the origin of the observed shifts, a number of measurements were also performed at different flow rates of the electrospray drying gas, on both aqueous and organic solutions of protein. The flow rate of the drying gas was found to influence the relative intensities of high charge‐states induced by heat or organic solvents to a small extent, but it did not produce substantial shifts in the charge‐state distributions observed in room temperatures ES+mass spectra of aque

ISSN:0951-4198    

DOI:10.1002/rcm.1290080203

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractA quartz crystal microbalance (QCM) is employed to determine the desorption yield of neutral particles in matrix‐assisted laser desorption ionization. For ferulic acid, the matrix substance used, the QCM mass resolution of 1 ng corresponds to a detection limit of ≈︁1012particles. Sample exposure effects are studied at different fluences by measuring the total desorption yield after consecutive laser pulses fired on the same spot on the sample. The dependence of the total yield on the fluence is studied for different angles of incidence of the laser beam. Varying the distance between the QCM and the sample yields information about the angular spread of the desorbed neutral particles. Additional information about the fluence threshold for the production of charged particles is gained by direct electronic measurements of sample cha

ISSN:0951-4198    

DOI:10.1002/rcm.1290080204

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractUnder methane chemical ionization conditions, multinuclear ions of ferrocene [Fen(C5H5)n+1]+(n= 2, 3 and 4), resulting from the ion/molecule reactions in the gas phase, were detected by mass spectrometry. Structures for these ions are elucidated, according to their mass‐analyzed ion kinetic energy spectra, to be triple‐, quadrupole‐, and quintuple‐decker sandwiches, respectively, and the formation pathways for them are also di

ISSN:0951-4198    

DOI:10.1002/rcm.1290080205

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractThe electron impact‐induced fragmentation processes of eleven differently substituted 5‐amino salicylic acids were studied by means of mass‐analyzed ion kinetic energy (MIKE) spectroscopy, parent‐ion spectroscopy and accurate mass measurements. Most of the fragmentation processes are related to the cleavages of the 5‐amino substituents. Unusual behaviour is that related to the CO2loss from the molecular ion, quite significant in the normal electron ionization spectra and completely undetectable in the MIK

ISSN:0951-4198    

DOI:10.1002/rcm.1290080206

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractA series of pyrilium hydrochlorides (Py+ClO−4) have been studied by means of both electron ionization and fast‐atom bombardment (FAB) methods. Only for some compounds does electron ionization show the formation of Py+, together with [Py—H]+·ions. Metastable ion data indicate that the former also originate through H·loss when their formation could be explained by loss of perchloric acid through a thermal process directly from the salt. Many fragment ions, related to the original structures, are also detected. In contrast, in FAB conditions, all the compounds show the formation of Py+without any fragmentation products, proving its effectiveness in the easy identification of the related molecular species. Only by the mass‐analyzed ion kinetic energy spectra of Py+ions can a valid characterization of the compounds under study be

ISSN:0951-4198    

DOI:10.1002/rcm.1290080207

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractThe major collision‐induced fragmentation of CH2CC(H)(O−) occurs following hydride transfer to form CH2CH−CO which then loses carbon monoxide to form deprotonated

ISSN:0951-4198    

DOI:10.1002/rcm.1290080208

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractThe structures of underivatized di‐ and tripeptides may be determined from a consideration of the collision‐induced dissociations of their [M—H]−ions. There are three types of fragmentation, viz. (i) the backbone cleavage which provides sequencing information, (ii) α side‐chain cleavage irrespective of the position of the amino acid residue, and (iii) cleavages which are characteristic of amino acid residues in specific positions, in particular the N‐ or C‐term

ISSN:0951-4198    

DOI:10.1002/rcm.1290080209

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractWe demonstrate the advantages of utilizing a broad‐band filtered noise field (FNF) for preferential mass injection of laser desorbed ions into an ion‐trap mass spectrometer (ITMS). The FNF waveform is applied to the endcap electrodes of the ITMS during the laser‐desorption period, and its amplitude and frequency spectrum are adjusted to resonantly eject all ions except those with selected mass‐to‐charge ratios. In single‐pulse laser desorption, the FNF rapidly ejects desorbed matrix ions without reducing the number of target ions that are trapped. When the FNF is used in conjunction with multipole laser‐desorption events, accumulation of targetm/zions results in a 40‐fold increase in sensitivity over single‐shot laser desorption. In addition, the application of sequential filtered noise fields for multiple stages of mass spectral interrogatio

ISSN:0951-4198    

DOI:10.1002/rcm.1290080210

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractThe feasibility of using capillary electrophoresis/mass Spectrometry, with negative‐ion electrospray ionization, for applications of relevance to the dyeing and textile industries has been shown. Structurally similar examples of solubilized vat dyes of different halogen content have been separated and identified with a view to investigating the photodegradation processes which occur when the dyes are subjected to UV light. Separations of the various species formed when a mordant dye is chrome treated are also presented, indicating the ability to study complex formation arising from the different chrome dyeing method

ISSN:0951-4198    

DOI:10.1002/rcm.1290080211

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY