bluuebunny/crossref_metadata_2025_split huggingface dataset:
A fast‐atom bombardment tandem mass spectrometry screening procedure for the presence of involatile sulphonated dyestuff intermediates
Authors: Monaghan J. J. , Morden W. E. 
Published: May 2005

AbstractThe introduction of more rigorous regulations aimed at controlling the use of sulphonated dyestuffs and dyestuff intermediates has pointed to the need for screening methods for the presence of these involatile compounds. Although much work has been caried out recently on the mass spectrometric behaviour of these compounds, it has been concerned principally with the production of molecular weight information using novel ionization methods rather than with any attempt to obtain structurally diagnostic fragment ions. In this mass spectrometric investigation of a range of naphthalene sulphonic acid salts, positive‐ion and negative‐ion fast‐atom bombardment (FAB) mass spectra have been obtained and FAB‐tandem mass spectrometry (MS/MS) has been used to acquire spectra (daugher‐ion, parent‐ion and neutral‐loss) in an attempt to develop a useful screening method. On known compounds, best results were found when using a negative‐ion neutral‐loss scan to detect the loss of 64 mass units (corresponding to loss of SO2). This was confirmed by successful use of this scan to screen a sample of sulphonate residues.
Loss of H2 from metastable CH3SiH ions
Authors: Tobita Seiji , Nakajima Katsuyoshi , Tajima Susumu , Shigihara Atsushi 
Published: May 2005

AbstractUnimolecular dissociations of metastable methylsilyl cations CH3SiH3+ are investigated by mass‐analysed ion kinetic energy (MIKE) spectrometry. The predominant fragmentation is H2 loss which proceeds via at least two distinct mechanisms with substantially different kinetic energy releases. Their reaction mechanisms are inferred from the results of experiments and MNDO calculations. The MIKE spectrum of the deuterium‐labelled ion, CH3SiD2+ indicates that the H and D atoms are randomized before dissociation.
Variation of kinetic energy release and average internal energy with temperature and electron energy for unimolecular ionic transitions
Authors: Selim Ezzat T. M. , Rabbih M. A. , Fahmey M. A. 
Published: May 2005

AbstractThe kinetic energy released and the intensity ratios [m*]/[M]+ or [m*]/[F]+ (where m* is a metastable peak, and [M]+ and [F]+ are molecular‐ion and fragment‐ion peaks, respectively) for seven unimolecular ionic transitions generated from benzyl alcohol and benzylamine have been studied as a function of ion‐source temperature and ionizing electron energy. Only during HCN elimination from [C7H8N]+ fragment ion does the kinetic energy released and the intensity ratio [58.9]/[106]+ display a temperature dependence. On the other hand, the kinetic energy released during only two transitions, generated from benzyl alcohol, displays a significant electron‐energy dependence while the intensity ratios [m*]/[M]+ or [m*]/[F]+ for all the transitions studied exhibit marked decrease with decreasing electron energy starting at about 40 eV.
Mass spectrometric study of vaporization processes and thermodynamic properties in the GeO2·P2O5 system
Authors: Stolyarova V. L. , Shornikov S. I. , Ivanov G. G. , Shultz M. M. 
Published: May 2005

AbstractThe Knudsen effusion mass spectrometric method was used to study the vaporization processes and thermodynamic properties of the GeO2·P2O5 system at 1423 K. GeO, PO2, P4O10, GePO3 and O2 molecules were identified in the gas phase above the GeO2·P2O5 system. A correlation was shown between the phase diagram and the thermodynamic properties attained in the GeO2·P2O5 system.
Mass spectral characteristics of some 3,5‐disubstituted 4‐isoxazolecarboxylic acids
Authors: Maksimović Milka , Nikolin Ana , Nikolin Branko 
Published: May 2005

AbstractMass spectrometry has been applied for the structural study of some new unsymmetrically 3,5‐disubstituted 4‐isoxazolecarboxylic acids prepared by a modification of the general procedure of Quilico and Fusco. The new glucoside, 3‐[2‐(β‐D‐glucopyranosiloxy)‐5‐chlorophenyl]‐5‐methyl‐4‐isoxazolecarboxylic acid (1) and 3‐(2‐hydroxy‐3,5‐dichlrophenyl)‐5‐methyl‐4‐isoxazolecarboxylic acid (2) have been prepared starting from the glucoside helicin, 2‐(β‐D‐glucopyranosiloxy) benzaldehyde or the corresponding aglucon, the salicylaldehyde, respectively. Fragmentation patterns of 2 and its analogue 3‐(2‐hydroxy‐5‐chlorophenyl)‐5‐methyl‐4‐isoxazolecarboxylic acid (3), obtained by the cleavage of the glycosidic linkage of 1 are discussed. The principal fragmentation routes of these compounds are formulated to occur via azirine intermediates.
Diatomic monociations and dications containing germanium and a rare gas atom
Authors: Curtis Jonathan M. , Rong Lu‐Shan 
Published: May 2005

AbstractDiatomic dications and monocations GeY2+ and GeY+˙, where Y = Ne, Ar, Kr or Xe, have been detected on the microsecond time scale. They are characterized via appearance energies, charge stripping of GeY+˙ ions, and mass‐analysed ion kinetic energy spectroscopy. The formation of GeAr+˙ is found to involve an excited state of Ar in a Hornbeck‐Molnar process.
Energy transfer limits in collisions with fast targets
Authors: Turecek Frantisek , Alexander Anthony J. 
Published: May 2005

AbstractThe kinematics of ion/neutral collisions are analysed in terms of projectile and target kinetic energies and relative velocities. High (keV) center‐of‐mass collision energies are achievable for high‐mass ions or neutrals colliding with keV target atoms, electrons or ions. The center‐of‐mass collision energy depends only very little on the fast‐target mass. Applications in collisionally‐activated dissociation of high‐mass ions and neutrals are discussed.
A collisional study of some C60 and C70 fullerene ions
Authors: Young Alex B. , Cousins Lisa M. , Harrison Alex G. 
Published: May 2005

AbstractThe high‐energy collision‐induced dissociation (CID) mass spectra of C, C, C, C and C are reported. In all cases, fragmentation occurs by loss of an even number of carbon atoms, in agreement with photodissociation studies of C and C. No charge‐separation reactions are observed for the multiply charged ions. Collision‐induced dissociation of C leads to a slight preference for formation of C, while dissociation of C and C shows a more pronounced preferenced for formation of C and C, respecstively. Under electron‐capture Chemical‐ionization conditions the fullerenes readily capture an electron to form the molecular anions. Collision‐induced dissociation of C and C leads to elimination of 1, 2 and 4 carbon atoms; the elimination of one carbon is unique among larger carbon cluster ions. Charges inversion of the molecular anions leads to formation of the respective molecular cations and fragementation of these cations by loss of an even number of carbon atoms. Formation of C is slightly preferred in the C case, while C is the most abundant ion in the charge inversion mass spectrum of C.
Electron ionization fragmentations of some N‐substituted 2‐N‐methylimino‐4,5‐tetramethyleneperhydro‐3, 1‐oxazines and related thiazines
Authors: Pihlaja Kalevi , Liukko‐Sipi Sirpa , Fülöp Ference , Bernáth Gábor , Vainiotalo Prijo 
Published: May 2005

AbstractThe 70 eV electron ionization mass spectra of six cyclohexane fused 2‐N‐methyliminoperhydro‐3,1‐oxazines and six related thiazines were recorded and their fragmentation behaviour studied by metastable‐ion analysis and exact mass measurement. For the unsubstituted compounds, decompositions which can be rationalized to start as a simple α‐cleavages with respect to the ring nitrogen atom were dominant. Many of these reactions were accompanied by a hydrogen‐atom transfer to the neutral fragment lost. N‐substitution prompted more extensive hydrogen migrations to take place, where hydrogen atoms were transferred to the heterocyclic part of the molecule. Only methyl‐substituted compounds showed remarkable sterochemical specificity, thus allowing isomeric differentiation to take place.
Standard reference spectra for tandem mass spectrometry quality assurance, performance evaluation and proficiency testing: Tandem mass spectrometers which use RF‐only multipole collision cells
Authors: Martinez Richard I. , Betowski Leon D. 
Published: May 2005

AbstractThe collisionally activated dissociation (CAD) of the acetone cation (m/z 58) can be used for quality assurance, performance evaluation, and proficiency testing of CAD measurements in tandem mass specstrometry (MS/MS) instruments which use RF‐only multipole collision cells. The absolute branching ratios (product distributions) of the CAD fragment ions, when measured as a function of the center‐of‐mass collision energy Ecm, can provide an objective basis for quality assurance whenever MS/MS methods are used (viz, to validate how well the target thickness, ion‐containment efficiency, and collision energy are being controlled in various instruments).
Continuous‐flow fast‐atom bombardment on an external‐ion‐source Fourier transform ion cyclotron resonance mass spectrometer
Authors: Watson C. H. , Kruppa G. , Wronka J. , Laukien F. H. , Van Binst G. 
Published: May 2005

AbstractA continuous‐flow sample interface for fast‐atom bombardment has been developed for use on an external‐ion‐source Fourier transform ion‐cyclotron resonance mass specstrometer. The new interface provides a quick and convenient means for sample introduction. A suppression of common glycerol matrix ions was observed when compared to static analysis. High mass resolution, exact mass measurements, and tandem mass spectrometry spectra were obtained on a sample of Gramicidin S.
The realization of a low‐energy ion‐scattering technique with an ion cyclotron resonance spectrometer
Authors: Nikolaev E. N. , Mordehai A. V. , Frankevich V. E. 
Published: May 2005

AbstractA low energy ion scattering technique for investigation of the first monolayer of a surface has been realized in an ion cyclotron resonance mass spectrometer. The secondary‐ion mass spectrometry mode is also available in the same configuration. Preliminary results are shown for the analysis of the metal surface of a magneto‐optical recording film.
Investigation of collisional‐activation decomposition process and spectra in the transport regions of an electrospray single‐quadrupole mass spectrometer
Authors: Voyksner Robert D. , Pack Terry 
Published: May 2005

AbstractThe use of collisional‐activation dissociation (CAD) in the electrospray region was evaluated for generating structural information on several pesticides and antibiotics. The collision energy used to generate the CAD spectra could be varied easily by changing the capillary/skimmer potential difference, imparting fromOeV to above 16 eV internal energy to the near thermal ions generated by electrospray, The internal energy distribution for low‐energy collisions (capillary/skimmer potential difference of 20 V) closely matches the curves generated by a triple‐quadrupole mass spectrometer. Furthermore, the CAD spectra for selected compounds generated by electrospray in the transport region at a capillary/skimmer potential differences of 30–50 V closly resembled those obtained from the [M + H]+ ion by a triple quadrupole using 30eV collision energy. The CAD of ions in the transport region resulted in 70% to 80% daughter‐ion yields and minimal loss in overall ion current compared to the ion current for protonated or cationized parent molecules. The major daughter ions for 10 pg of Aldicarb and penicillin G could be detected (signal‐to‐noise ratio>5) under full‐scan CAD conditions.
Comparison of intensities between doubly charged ions [M+2H]2+ and singly charged ions [M+H]+ of gramicidin S by electrospray mass spectrometry
Authors: Sakairi Minoru , Yergey Alfred L. 
Published: May 2005

AbstractThe reason why the intensity of doubly charged ions [M+2H]2+ of gramicidin S is higher than that of singly charged ions [M+H]+ in electrospray is investigated by ion evaporation theory. As a result of comparison between the total free energies of extracting [M+2H]2+ and [M+H]+ from a charged droplet to infinity, it is found that the total free energy of [M+2H]2+ is estimated to be lower than that of [M+H]+. This clearly supports the experimental result. In addition, the importance of the electrostatic contribution in electrospray is demonstrtated by showing the result that the total free energy of [M+2H]2+ without electrostatic contribution is higher than that of [M+H]+.
Four interfaces for liquid chromatography/atmospheric‐pressure‐ionization mass spectrometry
Authors: Sakairi Minoru , Yergey Alfred L. 
Published: May 2005

AbstractMixture analyses are demonstrated using the liquid chromatograph/atmospheric‐pressure‐ionization mass spectrometric system with four modes. These modes are atmospheric‐pressure spray with electron ionization, atmospheric‐pressure chemical ionization, atmospheric‐pressure spray ionization, and electrospray ionization modes. This system can deal with a wide variety of compounds from hydrocarbons with low polarity to proteins with high polarity.
High mass material (>104 daltons) in a coal liquefaction extract, by laser‐desorption mass spectrometry
Authors: John P. , Johnson C. A. F. , Parker J. E. , Smith G. P. , Herod A. A. , Gaines A. F. , Li C.‐Z. , Kandiyoti R. 
Published: May 2005

AbstractThe use of a laser‐desorption mass spectrometer to examine a coal liquefaction extract known to contain high‐molecular‐mass material (from size‐exclusion chromatography) has shown the presence of components of molecular mass in excess of 104Da for the first time. The molecules detected differ from each other in molecular mass by a few hundred or a few thousand Da. These preliminary results indicate that the basic coal‐structure molecules probably consist of aromatic clusters on a chin, in reasonable agreement with current theories of coal structure.
A kinetic method of distinguishing isomeric C3H cations
Authors: Riveros José M. , Zhu Zhiqing 
Published: May 2005

AbstractA method is described of studying ion/molecule kinetics in a Fourier‐transform ion cyclotron resonance spectrometer of ions produced at precursor pressures of 6 × 10−9 mBar with a neutral gas introduced through a pressure pulse of variable time. The analysis of the kinetic curves of the proton‐transfer reactions of C3H cations to CH3OH yields either single or double exponential decays that can readily be used to obtain the percentages of allyl and 2‐propenyl cations produced by different precursors. Allyl bromide is shown to produce 100% allyl cations while 2‐bromopropene at 13 eV yields roughly 74% of 2‐propenyl and 26% of allyl cations.
Mass‐specific selection of ions in Fourier‐transform ion cyclotron resonance mass spectrometry. Unintentional off‐resonance cyclotron excitation of selected ions
Authors: Heck Albert J. R. , de Koning Leo J. , Pinkse Frans A. , Nibbering Nico M. M. 
Published: May 2005

AbstractMass‐specific selection of ions in Fourier‐transform ion cyclotron resonance (FT‐ICR) ion trap is shown to be hampered by unavoidable off‐resonance cyclotron exctron excitation of the ions to be selected. This unintentional off‐resonance cyclotron excitation is caused by radio‐frequency fields which are applied during the selection procedure to eject unwanted ions by on‐resonance excitationof their cyclotron motion. The experimental results indicate that the effective cyclotron motion of the ions subjected to an off‐resonance single‐frequency RF field is alternatingly excited and de‐excited with a periodicity equal to 2π/(ω0−ωeff), where ω0is the frequency of the excitation field and ωeff is the effective ion cyclotron frequency. Furthermore, it has been demonstrated that the translational energy gained during off‐resonance cyclotron excitation can be predicted quantitatively by theory. The net translational energy can be minimized below 1 eV if the duration of the individual single‐rfrequency excitation fields is set to k2π/(ω0−ωeff), where k has to be an integer, representing the number of full off‐resonance excitation/de‐excitation periods. The unintentional off‐resonance cyclotron excitation is shown to lead to an instrumental upper limit for the mass selectivity of ion selection, the so‐called front‐end resolution. This upper limit is proportional to the cell diameter, and the square of the magnetic field strength, and inversely proportional to the noise level of the excitation RF‐field, and the mass of the ions to be selected. It is demonstrated that an instrumentally dictated maximum mass resolution of better than 50000 can be obtained for the selection of ions with a nominal mass‐to‐charge ratio of 79.
Electron ionization mass spectrometry of phenylpyridazinylmethanols and phenylpyridazinyl ketones
Authors: Pittenauer Ernst , Allmaier Günter , Schmid Erich R. , Krenmayr Peter , Heinisch Gottfried , Budzikiewicz H. 
Published: May 2005

AbstractThe mass spectrometric fragmentation behaviour of four monosubstituted pyridazines (phenyl‐3‐ and phenyl‐4‐pyridazinylmethanol, phenyl‐3‐pyridazinyl and phenyl‐4‐pyridazinyl ketone) was investigated. Fragmentation pathways were established by combined interpretation of the data obtained from high resolution measurements and from low‐energy collision‐activated dissociation mass spectra of the molecular ions as well as of several important fragment ions. A clear differentiation between these 3‐ and 4‐substituted 1,2‐diazines is possible for both sets of pyridazines. Only the spectra of the 3‐isomers exhibit an abundant [MH]+ peak, which indicates a cyclization of these ions involving one ring nitrogen atom. Another difference between the two isomeric phenylpyridazinylmethanols is the loss of OH from the molecular ion, as detected for the C‐3 substituted compound only. For the phenylpyridazinyl ketones, the loss of CO from the molecular ion, which is only observed with the 3‐isomer, permits an unequivocal differentiation.
Fast‐atom bombardment mass spectrometry and metastable‐ion studies for the characterization of isomeric fluorosugars
Authors: Kiremire B. T. , Chirello D. , Traldi P. , Bravo P. , Resnati G. 
Published: May 2005

AbstractCharacterization of stereoisomeric 3,4‐dideoxy‐3‐fluoro‐hexoses has been carried out using fast‐atom bombard‐ment. Diagnostic fragments were observed in the daughter‐ion spectra of the [M‐H]− and [M+H]+ ionic species. Notable differences were also observed in the relataivae abundances of ionic species corresponding to [M‐H]−, [M‐H‐HF]− and [C11H11O2]− ions.
Use of a moving‐belt interface for on‐line high‐performance liquid chromatography/mass spectrometry characterization of polycyclic aromatic compounds of molecular weight up to 580 Da in environmental samples
Authors: Perreault H. , Ramaley L. , Sim P. G. , Benoit F. M. , Wise S. A. 
Published: May 2005

AbstractThe applicability of the moving belt high‐performance liquid chromatography/mass spectrometry (HPLC/MS) interface to the analysis of high molecular weight polycyclic aromatic compounds (PACs) in a complex sample derived from coaltar is investigated. This interface provides good preservation of chromatographic integrity and useful electron ioniation spectra of thermally stable PACs of low to moderate volatility up to molecular masses of at least 580 Da. It is concluded that this HPLC/MStechnique will be useful in the analysis of such complex samples, provided a large enoughsuite of standard compounds can be made available.
Anionic rearrangements of deprotonated α‐alkoxyvinyltrimethylsilanes in the gas phase
Authors: Eichinger Peter C. H. , Bowie John H. 
Published: May 2005

Abstractα‐Alkoxyvinyltrimethylsilanes deprotonate to form two species −CHC(SiMe3)OR and CH2C(Si(Me)2CH2−)OR. The silylcarbanion undergoes the unusual rearrangement reaction CH2C(Si(Me3)2CH2−)OR → ((CH2CO)Me2RSiCH2−) Me2RSiCH2− + CH2CO. Loss of (R‐H) occurs when R ≥ Et; it is suggested that this is a reaction of the vinvl anion system.
Electrospray ionization mass spectra of hemoglobin and transferrin by a magnetic sector mass spectrometer. Comparison with theoretical isotopic distributions
Authors: Wada Yoshinao , Tamura Jun , Musselman Brian D. , Kassel Daniel B. , Sakurai Toru , Matsuo Takekiyo 
Published: May 2005

AbstractElectrospray ionization mass spectra of human hemoglobin chains and of transferrin were acquired on a magnetic sector mass spectrometer. The observed molecular ion for each hemoglobin chain was in good agreement with the theoretical isotopic distribution at a reasonable resolution of 2000. The clear separation of a variant ß‐chain in admixture with the normal counterpart at mass 15867 that differed from it by 14 Da (0.09%) ensured that a smaller mass difference could be detected. The molecular ions for human transferrin were too broad compared with the theoretical shape to determine the molecular mass accurately, probably due to the heterogeneity of the carbohydrate moiety. A decrease in mass by neuraminidase digestion, however, determined the average number of sialic acids in the molecule.
Desorption of ions from locust tissues. II. Metabolites of E‐destruxin using negative‐ion fast‐atom bombardment mass spectrometry
Authors: Lange C. , Loutelier C. , Cherton J.‐C. , Cassier P. , Vey A. , Pais M. 
Published: May 2005

AbstractDetoxification of E‐destruxin into E‐diol‐destruxin, conjugated glutathion‐E‐destruxin, cysteinyl‐E‐destruxin, and phosphorylated‐E‐destruxin in vivo in Locusta migratoria is demonstrated using direct negative‐ion fast‐atom bombardment mass spectrometry (FAB‐MS) without the need for prior extraction or purification.
The correct molecular weight of myoglobin, a common calibrant for mass spectrometry
Authors: Zaia Joseph , Annan Roland S. , Biemann Klaus 
Published: May 2005

AbstractMyoglobins from horse heat muscle, horse skeletal muscle and sperm whale are widely used as calibration standards or test compounds for various mas spectrometric methodologies. In all such cases reproted in the literature, a molecular weight value is used (16950.5 and 17199, respectively) which is based on the assumption that amino acid 122 in this 153 amino‐acid‐long protein is asparagine, overlooking a published suggestion that it is aspartic acid instead. Since the mass assignment accuracy for matrix‐assisted laser desorption mass spectrometry is reproted to be ±0.01% and for electrospray ionization ±0.0025%, and error of one mass unit in ∼ 17000 would be significant. The mass‐to‐charge ration of ions of the tryptic peptide encompassing amino acid 122 derived from commercially available horse heart and horse skeletal myoglobins, the apomyoglobin of the latter, and the tryptic and chymotryptic peptide of sperm whale myoglobin proved that in both proteins amino acid 122 is indeed aspartic acid, rather than asparagine. This finding was further confirmed by the collision‐induced dissociation sectra of the [M+H]+ ions of the tryptic peptides from the horse myoglobins and the chymotriptic peptide from sperm whale myoglobin. Thus, the correct molecular weight of horse myoglobinis 16951.49 and that of the sperm whale protein is 17199.91.
Ionspray mass spectrometry of marine toxins. IV. Determination of diarrhetic shellfish poisoning toxins in mussel tissue by liquid chromatography/mass spectrometry
Authors: Pleasance Stephen , Quilliam Michael A. , Marr Julie C. 
Published: May 2005

AbstractAn Improved liquid chromatographic/mass spectrometric (LC/MS) method utilizing gradient elution and ion‐spray ionization is described for the sensitive determination of okadaic acid and dinophysistoxin‐1, the principal toxins implicated in cases of diarrhetic shellfish poisoning. The method was used to confirm the presence of both toxins, together with a recently identified isomer of okadaic acid, dinophysistoxin‐2, in various samples of cultivated blue mussels (Mytilus edulis) from Canadian and European Waters. The method provided a mass detection limit of 0.4 ng for each toxin, thus allowing detection of 40 ng per g of whole mussel tissue (or approximately 10 ng/g if only the digestive glands were used in the assay). Quantitative results obtained by LC/MS were in good agreement with those obtained by derivatization and high‐performance liquid chromatography with fluorescence detection.