bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tandem mass spectrometry of fatty acid methyl esters. Evidence for bicyclic product ions
Authors: Cairns Thomas , Siegmund Emil G. 
Published: May 2005

AbstractProduct‐ion spectra derived from both protonated and hydride‐abstracted molecules of long chain esters have revealed an unusual homologous series of ions which suggest a cyclization mechanism to form stabilized bicyclodecenes or bicyclononenes.
Electrostatic quadrupole lens simulation in potential array relaxation programs
Authors: Jayaweera Palitha , Ramaley Louis , Boerboom A. J. H. 
Published: May 2005

AbstractLens and ion trajectory simulation programs, such as the popular program SIMION, which employ potential array relaxation methods, are very useful in designing and modifying ion lens systems. Unfortunately, these programs cannot simulate lenses of certain geometries such as quadrupoles. Several approaches for portraying static DC quadrupole lenses accurately in such programs have been investigated. These include user programming, an option in the latest version of SIMION, and array modification. The most convenient and accurate method involves modifications to the lens arrays employing relaxation techniques similar to those used in SIMION itself. These have been incorporated into a self‐contained computer program named QREFINE, which is available to interested parties.
Strategy for sequencing peptides as mono‐ and dilithiated adducts using a hybrid tandem mass spectrometer
Authors: Leary Julie A. , Williams Todd D. , Bott Geoffrey 
Published: May 2005

AbstractA strategy for sequencing peptides using the mono‐ and dilithiated quasimolecular ions is proposed. Low energy collision‐induced dissociation (CID) of the monolithiated species produced primarily [An+LiH]+ and [Bn+H+OLi]+ ions while that of the dilithiated species produced [An+LiH]+ and [Yn+Li+H]+ ions. The precursor parent ion in the monolithiated adduct is proposed to be a mixture of lithiated neutral peptide (1) and protonated lithium salt (2). Mechanisms for the formation of the [An+LiH]+ and [Yn+Li+H]+ ions are proposed. Four peptides of known composition but unknown sequence were successfully sequenced using the combined data from the CID spectra of the mono‐ and dilithiated species.
Comparison of fast‐atom bombardment, thermal ionization and inductively coupled plasma mass spectrometry for the measurement of 64Zn/67Zn stable isotopes in human nutrition studies
Authors: Eagles J. , Fairweather‐Tait S. J. , Mellon F. A. , Portwood D. E. , Self R. , Götz A. , Heumann K. G. , Crews H. M. 
Published: May 2005

AbstractFast‐atom bombardment, thermal ionization and inductively coupled plasma mass spectrometry are contrasted in comparative measurements of 64Zn/67Zn isotope ratios on samples isolated in the course of a human mineral‐nutrition experiment. The data are evaluated with reference to the precision normally required in enriched stable‐isotope mineral‐nutrition studies, and the convenience of the mass spectrometric techniques is also compared.
Collisionally activated decomposition spectra of normal nucleosides and nucleotides using a four‐sector tandem mass spectrometer
Authors: Sakurai T. , Matsuo T. , Kusai A. , Nojima K. 
Published: May 2005

AbstractCollisionally activated decomposition spectra derived from normal nucleosides and nucleotides have been studied using a four‐sector tandem mass spectrometer. The selectivity for a precursor ion has been improved by the use of the first two sectors as a double‐focusing mass spectrometer, and the mass resolution of daughter spectra has been enhanced using the next two sectors as a second double‐focusing mass spectrometer. Reliable and reproducible data with respect to the structure of nucleosides and nucleotides have been obtained.
Do ion trap and quadrupole lead to identical results in the analysis of terpenoic compounds?
Authors: Galletti G. C. , Traldi P. , Bonaga G. , Chapman J. R. 
Published: May 2005

AbstractThe ion trap detector (ITD) is effective in the analysis of terpenoic mixtures from essential oils. ITD spectra are compared in library searches with spectra from a quadrupole mass spectrometer. ITD generally leads to lower FIT values, although its efficiency in terms of structural identification is comparable to that of quadrupolar systems.
Isotope label scrambling in alkyl cations. A mechanistic proposal
Authors: Tuinman A. A. , Cook K. D. , Macfarlane Ronald D. 
Published: May 2005

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 scrambling.
Do the benzyl and silabenzyl anions show similar ion chemistry in the gas phase?
Authors: O'Hair Richard A. J. , Bowie John H. 
Published: May 2005

AbstractThe ion PhSiH 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 is characteristic of silyl anion systems and bears no analogy to that of benzyl anion reactions; for example with N2O and CO2 it forms Ph(H)2SiO− as the sole ionic product, while with CS2 it yields Ph(H)2SiS−.
Cluster‐ion formation between solvent and matrix using fast‐atom bombardment mass spectrometry
Authors: Haskins N. J. , New A. P. 
Published: May 2005

AbstractFast‐atom bombardment ionization requires the sample to be in solution. This is often achieved by predissolving the sample in a suitable solvent. However, spectra can be obscured by solvent/matrix cluster ions. This work has examined a number of common solvents and their propensity for clustering with glycerol or other matrices.
Instrument‐independent database for collisionally activated dissociation in radiofrequency‐only quadrupoles. Single‐collision versus multiple‐collision conditions
Authors: Martinez Richard I. , Ganguli B. , Cooks R. G. 
Published: May 2005

AbstractThe collisionally actived dissociation (CAD) of the acetone cation (m/z 58) and of the acetyl cation (m/z 43) from acetone were studied under single‐collision and multiple‐collision conditions. A kinetics‐based measurement protocol developed at the National Institute of Standards and Technology was used to measure the CAD spectra (i.e., the product distributions (branching ratios) of the CAD fragment ions). A protocol is proposed for a second interlaboratory round robin to explore the feasibility (or lack thereof) of measuring standardized, instrument‐independent CAD spectra under multiple‐collision conditions.
A coordinated approach towards the molecular weight determination of peptides by gel electrophoresis and fast‐atom bombardment mass spectrometry
Authors: Camilleri Patrick , Haskins Neville J , Hill Andrew J , New Anthony P , Games D. E. 
Published: May 2005

AbstractThe molecular weight of peptides can be determined by fast‐atom bombardment mass spectrometry (FAB‐MS) following polyacrylamide gel electrophoresis (PAGE). Initial results combining the fast and efficient separation of peptides by PAGE and the unambiguous determination of molecular weights by FAB‐MS have been demonstrated for the three peptides bradykinin, neurotensin and gramicidin S. This method has also been applied to the determination of the molecular weights of two fragments from the tryptic digest of horse‐heart cytochrome c.
Isomer discrimination of polycyclic aromatic hydrocarbons in negative‐ion chemical ionization mass spectrometry using carbon dioxide
Authors: Elson C. M. , Sim P. G. 
Published: May 2005

AbstractThe negative‐ion chemical ionization mass spectra of a group of isomeric polycyclic aromatic hydrocarbons (PAH) have been studied using CO2 as reagent buffer gas. The spectra show reproducible and characteristic differences between members of the set, implying that this technique offers some potential for distinguishing among groups of PAH isomers.
Potential misidentification of trichlorophenylethanol in imported peppers
Authors: Cairns Thomas , Siegmund Emil G. , Barry Thomas L. , Petzinger Glenn 
Published: May 2005

AbstractDuring regulatory analyses for the determination of pesticide residues on agricultural commodities, a frequently encountered trichlorinated compound was misidentified by the NBS library search routine. This case history illustrates the need for more rigorous confirmation criteria when dealing with multi‐chlorinated compounds where fragmentation can be dominated by methyl loss followed by loss of CO and HCl.
A terbody complex intermediate in [alkyl ether…︁\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm H}\limits^ + $\end{document}…︁alcohol] ions
Authors: Monteiro C. , Audier H. E. , Mourgues P. , Berthomieu D. 
Published: May 2005

AbstractIons of the form [alkyl ether…︁\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm H}\limits^ + $\end{document}…︁alcohol] have been generated in the ion‐source of a VG ZAB 2F mass spectrometer and studied in the 2nd field‐free region. The metastable ions only give the protonated alkyl ether fragment if there is no tertiary carbon in the α position of the oxygen atoms. If there is a tertiary carbon, the formation of protonated ether competes with other processes involving the elongation of the OCα (tertiary) bond(s). With tertiary alcohols and nontertiary ethers, this elongation leads to a terbody complex in which the tertiary carbocation is solvated by the ether and a molecule of water or, if the ether contains one tertiary group, a terbody complex is formed where the tertiary carbocation is solvated by two molecules of alcohol. Furthermore, a permutation between tertiary groups is observed when both ether and initial alcohol bear such substituents. Most probably, the formation of terbody complexes competes with other mechanisms, concerted processes, for instance.
Determination of the charge state of ions in thermospray mass spectra
Authors: Chan K. , Wintergrass D. , Straub K. 
Published: May 2005

AbstractAnalysis of the profiles of isotope clusters can be used to determine the charge state of ions in thermospray mass spectrometry. This observation was verified by comparison of experimental results with theoretical calculations. The applicability of this technique was illustrated by the characterization of peptides whose molecular weights were in the range of 500 to 5000 Da. Using thermospray ionization on a quadrupole mass spectrometer, [M + 2H]2+ and [M + 3H]3+ ions of the peptides were identified. These multiply charged ions enabled us to characterize molecules with molecular weights exceeding the normal mass range of the instrument.
Quadrature heterodyne method for fourier‐transform ion cyclotron resonance mass spectrometry
Authors: Fujiwara Makoto , Katakura Hisao , Inoue Masao 
Published: May 2005

AbstractIn Fourier‐transform ion cyclotron resonance (FT‐ICR) mass spectra resulting from the signals detected with a single pair of detection plates (i.e., real‐time‐domain signals), the foldback of spectral information about the Nyquist frequency occurs. In heterodyne mode FT‐ICR mass spectrometry, using quadrature reference signals, a complex ICR signal consisting of two quadrature reference signals, a complex ICR signal consisting of two quadrature signal components can be acquired easily. By Fourier transform of the signal, the reflection of peaks about the Nyquist frequency in the frequency‐domain spectrum can be eliminated. As a result, the available bandwidth of the spectrum is doubled. Validity of this quadrature heterodyne method is confirmed by the experimentally obtained spectrum of Xe+ ions.
Collision‐energy ramp. A modification to an RF‐only quadrupole collision cell
Authors: Bott Geoffrey , Ogden Sherri , Leary Julie A. 
Published: May 2005

AbstractA modification to the electronics controlling the collision energy of an RF‐only quadrupole collision cell in a BEqQ geometry mass spectrometer is described. The modification allows the collision energy to be ramped from 0–500 eV while scanning the quadrupole mass analyser. The collision‐induced dissociation spectra generated using a ramped collision energy exhibit a 10%–100% increase in product‐ion abundance.
On‐line combination of supercritical‐fluid chromatography with fast‐atom bombardment mass spectrometry
Authors: Matsuura K. , Takeuchi M. , Nojima K. , Kobayashi T. , Saito T. 
Published: May 2005

AbstractStudies on combined supercritical‐fluid chromatography (SFC) using a packed column, with fast‐atom bombardment mass spectrometry (FAB‐MS) are described. The interfacing was successfully carried out by simply coupling a frit interface between the liquid chromatograph (LC) and the mass spectrometer. The interface was equipped with a pneumatic splitter and post‐column addition device delivering FAB matrix material to a release valve which maintained a constant back‐pressure at the column outlet. Using a 1% glycerol solution as a matrix compound in the release valve, the SFC/FAB‐MS combination operates as well as a normal LC/MS instrument. The performance was demonstrated with a mixture of α‐, β‐ and γ‐tocopherol and Triton X‐100 (poly(ethylene glycol) p‐isooctylphenyl ether).
Reproducing daughter‐ion spectra using the transmission oscillation properties of quadrupole collision cells
Authors: Lamb John H. , Naylor Stephen 
Published: May 2005

AbstractThe transmission oscillation properties of parent ions through an RF‐only quadrupole are investigated as a function of collision energy, radicfrequency of the quadrupole, and type and pressure of target gas. It is shown that small variations of collision energy can result in substantial differences in daughter‐ion spectra obtained from the same parent ion. Since absolute values of collision energy are difficult to determine, reproducible daughter‐ion spectra are problematical to acquire.In this work we show that reproduction of daughter‐ion spectra, using the transmission properties of the collision cell, is possible. The characteristics of an RF‐only quadrupole (Q*) are such that the parent ion intensity at the second detector varies as a function of collision energy and displays sinusoidal properties. By using the nodes and anti‐nodes of the parent‐ion transmission it is possible to achieve reproducible daughter‐ion spectra of a wide range of biopolymers. The tuning of Q* is mass‐dependent and not compound‐dependent. Hence it is possible to optimize and tune Q* using an isobaric (or almost) standard such as one of the ions of perfluorotri‐n‐butylamine (electron ionization) or a glycerol cluster ion (fast‐atom bombardment mass spectrometry) before subjecting valuable sample to tandem mass spectrometry.
Experience in the use of a 4‐sector instrument and array detector and its application in peptide analysis
Authors: Burlingame A. L. , Walls F. C. , Falick A. , Evans S. , Riddoch A. , Buchanan R. 
Published: May 2005

AbstractA 4‐sector EBEB mass spectrometer, fitted with a liquid secondary‐ion mass spectrometer (Cs+) ion source and an array detector has been in use at UCSF for the past 18 months. Using this period, calibration procedures have been developed and operating software refined such that the instrument can now be operated in the tandem mass spectrometry (MS/MS) mode using the array on a routine basis and with a high sample throughput. The instrument has been applied successfully to the analysis of a wide range of peptides, up to molecular weights in excess of 2500. The array is usually operated with a mass resolution of about 1500 full width at half maximum (FWHM), and under these conditions a fragment ion dynamic range of 3000:1 is obtainable. Mass assignment is typically reproducible to within 0.1 u.
Electron‐ionization‐Induced fragmentation of N‐monosubstituted 2‐phenylacetamides
Authors: Jeremić Ljiljana A. , Kobilarov Nestor L. , Petrović Slobodan D. 
Published: May 2005

AbstractElectron‐ionization‐induced mass spectra of N‐monosubstituted 2‐phenylacetamides were recorded and their fragmentation patterns were studied by metastable‐ion analyses. Representative deuterated analogues of these compounds have also been synthesized and their mass spectra compared with those of the unlabelled parent compounds. The most typical fragmentation for N‐alkyl‐, N‐isoalkyl‐ and N‐cycloalkyl‐2‐phenylacetamides is cleavage of the bond β to the carbonyl function, resulting in an ion fragment of m/z 92, following the transfer of hydrogen and elimination of a corresponding ketene. The primary fragmentation process for N‐aryl substituted 2‐phenylacetamides is the loss of an aromatic hydrogen atom from the molecular ion. The other principal fragmentation processes observed with these compounds are discussed.
Accurate mass measurement of positive ions produced by ammonia chemical ionization
Authors: Lawrence David L. 
Published: May 2005

AbstractA technique is described which enables the accurate mass measurement of positive ions produced under ammonia chemical ionization (NH3‐CI) conditions using a mixture of perfluorinated alkanes (referred to commonly as perfluorokerosene or PFK) as the secondary mass reference even though these perfluorinated compounds do not form positive ions under NH3‐CI conditions. By creating a ‘composite’ spectrum of analyte under NH3‐CI conditions, and PFK under electron ionization (EI) conditions, while signal averaging in memory, mass measurement of the analyte peaks can be accomplished. Combined capillary gas chromatography/accurate mass measurements of components at sub‐part‐per‐million levels in environmental extracts are described as well as confirmation of novel eicosanoid structures.
A facile method for the localization of a double bond in aliphatic compounds
Authors: Schneider B. , Budzikiewicz H. 
Published: May 2005

AbstractOlefinic aliphatic compounds can be transformed on a microscale into the corresponding epoxides by reaction with m‐chloroperbenzoic acid. The crude reaction mixture can be analysed without further work‐up, by gas chromatography followed by chemical ionization mass spectrometry or desorption chemical ionization mass spectrometry with nitric oxide as the chemical ionization gas.
Electron ionization mass spectrometry of synthetic C60
Authors: Luffer Debra R. , Schram Karl H. 
Published: May 2005

AbstractNovel carbon clusters isolated in the solid phase have been characterized by electron ionization (EI) mass spectrometry. The crystalline material contains the C60 and C70 molecules in a ratio of 37:1. Both of these molecules form singly charged ions that appear at m/z 720 and 840, respectively, and doubly charged ions that appear at m/z 360 and 420, respectively. Only the C60 molecule produces the triply charged species, at m/z 240. C60 undergoes fragmentation by losing successive multiples of C2 through C16. The C70 molecule only loses the fragments C2 and C4. Collisionally activated decomposition of these molecules in the first field‐free region did not reveal any more extensive fragmentation than was observed under EI conditions.
Mass spectrometric investigation of 2‐aminopropiophenones and some of their metabolites
Authors: Pokrajac M. , Miljković B. , Bisailović B. 
Published: May 2005

AbstractComplex metabolic mixtures of 2‐aminopropiophenones, obtained both after in vitro and human in vivo metabolism of these compounds, have been investigated using both mass spectrometry and gas chromatography/mass spectrometry. The mass spectrometric fragmentation schemes of the compounds have been proposed and verified. The schemes are based on the characteristic fragments obtained by alpha‐cleavage of these compounds using direct inlet mass spectrometry or gass chromatography/mass spectrometry. these findings were confirmed with chemical ionization mass spectrometry, when quasi‐molecular (MH+) ions were obtained as the highest relative abundane ions for all the compounds investigated, and were used in metabolic investigations of 2‐aminopropiophenones.
Matrix/sample interactions in ultraviolet laser‐desorption of proteins
Authors: Doktycz Stephen J. , Savickas Philip J. , Krueger Duane A. 
Published: May 2005

AbstractExamination, by optical microscopy, of the matrix/analyte morphology of a sample propared from a droplet in matrix‐assisted UV laser‐desorption mass spectrometry (MUVLDMS) reveals that the matrix crystallizes to a large extent, thus altering the concentration of the material in regions on the surface from that of the bulk applied solution. Microscopy reveals that vanillic acid and to a lesser extent nicotinic acid matrices form prominent crystalline rings around the dried sample spot while sinapic acid forms a more uniform dispersion of the crystallized matrix. Insulin analyte investigated in this report tendss to form a thin isotropic phase in the center of the drops. The first reported use of a KrF excimer laser (249 nm) in MUVLDMS is also discussed.
Modification of a commercially available thermospray interface and its use for the analysis of sulfonated azo dyes by liquid chromatography/mass spectrometry
Authors: Groeppelin A. , Linder M. W. , Schellenberg K. , Moser H. 
Published: May 2005

AbstractA standard commercial thermospray interface was modified by replacing the stainless‐steel capillary by another stainless‐steel capillary with a larger internal diameter. A fused‐silica capillary was then placed within the whole length of the stainless‐steel capillary and connected to the liquid chromatograph. A thermospray interface modified in this way exhibits a more inner surface, resulting in an increased sensitivity for analysing sulfonated azo dyes. Analysis of sub‐microgram quantities is possible only with the modified interface.
Molecular weight determination of a polyamidoamine Starburst polymer by electrospray ionization mass spectrometry
Authors: Kallos G. J. , Tomalia D. A. , Hedstrand D. M. , Lewis S. , Zhou J. 
Published: May 2005

AbstractElectrospray ionization mass spectrometry has been demonstrated to be a useful technique for the molecular weight determination of a Starburst polymer. Mass spectra of multiply charged ions are deconvoluted to provide molecular weight information of many components in a non‐separated mixture. These data may also be used for determining a polydispersity value for this systhetic polymer system.
Suitability of fast‐ion bombardment mass spectrometry for the investigation of 1,4‐dihydropyridine derivatives
Authors: Hamdan M. , Scandola M. , Franchi D. , Tarzia G. , Gaviraghi G. 
Published: May 2005

AbstractPositive/negative fast‐ion bombardment (FIB+/FIB−, negative‐ion chemical ionization (CI−) and positive‐ion electron ionization (EI+)mass spectrometry are used to investigate a number of 1,4‐dihydropyridine derivatives. The FIB+ mass spectra presented, acquired at fixed Cs+ ion‐gun voltage as well as at different voltages ranging from 1–16 kV, display a close resemblance to their EI+ mass spectral counterparts. Comparison of the FIB− data with data acquired in ammonia CI− demonstrates that for the type of compound investigated in this work, the latter ionization technique yields a superior molecular anion signal and negligible fragmentation. Some of the FIB+ mass spectra presented display a number of unmistakeable qualitative differences which are tentatively attributed to the isomeric stereo‐chemistry of the compounds investigated.
Cationization of destruxins (cyclodepsipeptides) under fast‐atom bombardment
Authors: Lange C. , Mulheim C. , Vey A. , Pais M. 
Published: May 2005

AbstractCationization ability is presented using fast‐atom bombardment mass spectrometry and fast‐atom bombardment tandem mass spectrometry. The sodium cation has the best potential for cationizing A‐ and E‐destruxins (cyclodepsipeptides), E‐destruxin having a greater ability to cationize with Na+ than A‐destruxin.