bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass spectrometric studies on some F(CF2)n(CH2)mH semifluorinated alkanes
Authors: Napoli M. , Krotz L. , Conte L. , Seraglia R. , Traldi P. 
Published: May 2005

AbstractNine Semifluorinated alkanes, F(CF2)n(CH2)mH, were analysed by electron ionization and electron‐capture mass spectrometry. Both techniques showed the presence of H…︁F bridges between the zigzag hydrocarbon chain and the twisted fluorocarbon one. In particular, this interaction can explain the extensive sequential HF losses detected in electron‐capture mass spectrometry. The low abundance of fragments corresponding to cleavage of a CF2‐CH2 bond indicate a relatively high bond strength.
Matrix isolation applied to the 252Cf plasma‐desorption mass spectrometry of underivatized oligosaccharides
Authors: Metzger J. O. , Woisch R. , Tuszynski W. , Angermann R. , Puls J. 
Published: May 2005

AbstractA number of different low molecule weight and volatile compounds have been tested and compared as matrices in 252Cf plasma‐desorption mass spectrometry (PDMS) measurements of oligosaccharides. Some heteroaromatic amines (2‐aminothiazole and 3‐aminopyridine), hydroxyanthraquinones (alizarin and quinalizarin) and phthaleins (fluorescein) proved to be especially suited to enhancing the quasimolecular ion intensity of oligosaccharides. Discrimination effects could be reduced by matrix addition and thus, quantitative results of PDMS could be improved. Oligosaccharides with broad molecular weight distribution (dextrin 10 and dextran T 1.5) have been successfully analyzed by PDMS. The mass spectra obtained compared quite well with ion chromatograms of the respective oligosaccharides.
Triton X‐100 as a reference compound for ammonia high‐resolution chemical ionization mass spectrometry and as a tuning and calibration compound for thermospray
Authors: Brinded Keith A. , Tiller Philip R. , Lane Stephen J. 
Published: May 2005

AbstractThe non‐ionic surfactant Triton X‐100, 1‐(1,1,3,3,‐tetramethylbutyl)‐4‐[poly(1,2‐ethanediol)]benzene, has been evaluted as a reference material for positive‐ion high‐resolution ammonia chemical ionization (CI) mass spectrometry and as a tuning and calibration material for positive‐ion thermospray mass spectrometry (TSP). When ammonia is used as the CI reagent gas, Triton‐X‐100 produces evenly spaced ions that 44 u apart. Triton X‐100 cab be volatilized from a solids prove and is routinely used as the reference material for high‐resolution measurements. A reference table has been constructed from the theoretical values for the different masses. Triton X‐100‐Reduced and Triton X‐405‐Reduced were also evaluated as additional reference com‐pounds. As a calibration and tuning compound for TSP, Triton X‐100 affords an envelope of ions centred around m/z 600–700 with ions observed above m/z 1000. Triton X‐100‐Reduced affords a similar envelope although the ions observed are 6 u higher in mass.
An investigation into the stereochemistry of the boronate di‐esters of some monosaccharides using tandem mass spectrometry
Authors: New Anthony P. , Haskins Neville J. , Games David E. 
Published: May 2005

AbstractThe aim of this work was to probe the stereochemistry of a series of monosaccharides. Firstly, the underivatized sugars were investigated using linked‐scans and tandem mass spectrometry on a ‘hybrid’ instrument (hybrid MS/MS) and secondly, a comparison of linked‐scan and hybrid MS/MS was carried out on the butyl and phenyl boronate di‐esters. In situ derivatization of the sugar to the boronate di‐ester allows a negative‐ion fast‐atom bombardment (FAB) investigation with greater sensitivity than for the underivatized sugar. The linked‐scan data allow a great deal of information on the structure and chemistry of the sugars to be obtained, but the sensitivity at lower mass is limited. The hybrid MS/MS data give similar fragmentation information, plus improved sensitivity at lower molecular weight.
A low‐pressure penning ion source for volatile organic compounds
Authors: Kohler M. , Schlunegger U. P. 
Published: May 2005

AbstractA Penning ion source for volatile organic compounds is described. Design, operating conditions, and properties of the ions generated are reported. The source operates at pressures ranging from 10−5 to 10−3 mbar; a sensitivity of 1.4 × 10−4 A/mbar is achieved. Mass spectra of 4‐methyl‐2‐pentanone, ethyl benzoatc, dimethyl sulfoxide, trichlorofluoromethane and 1,1,2‐trichlorotrifluoroethane obtained at low discharge currents are almost identical with their corresponding electron impact spectra at 70 eV. Two different discharge modes, depending on pressure, were found. The average energy of the ions is proportional to the potential of the ion source (〈E〉 = 0.64U, energy given in eV). Multiply charged Ar ions, Arn+, up to n = 4, have been observed.
Electron impact ionization of fullerenes: Appearance energies of C, n = 1, 2 and 3
Authors: Baba Magapu Sai , Narasimhan Thirupattur S. Lakshmi , Balasubramanian Rajagopalan , Mathews Cherian K. 
Published: May 2005

AbstractThe ionization efficiency curves for the production of singly, doubly and triply charged ions from C70 by electron impact are reported, for the first time, up to an electron energy of 80 eV. Appearance energies were derived by linear extrapolation of ionization efficiency curves as 7.8±0.5 eV, 16.0±0.5 eV and 33.0±1.0 eV respectively for C, C and C. The shape of the ionizaiion efficiency curves suggests that there are several energies at which resonant absorption to excited states takes place. Relative abundances of the three ions at various electron energies are also presented. An estimate for the appearance energy of C is given.
A high resolution gas chromatographic/mass spectrometric method for the determination of N‐0923 in human and monkey plasma
Authors: Zavitsanos Paul A. , Siddiqui Waheed , Curtis Michael 
Published: May 2005

AbstractA method that combines gas chromatography and mass spectrometry (GC/MS) for the determination of N‐0923 in human and monkey plasma is detailed. This novel drug holds promise for the treatment of Parkinson's disease. Clinical use of N‐0923 will result both in low peak plasma concentrations and in a short half‐life; consequently, a highly sensitive method will be required. Previous methods using high‐performance liquid chromatography with electrochemical detection have given reliable data in high dose studies in animals to 0.3–1.0 ng/mL in plasma but are not considered adequate for studies at clinical levels in humans. The data in this paper will show that GC/MS can offer a new direction in the determination of N‐0923 in human and monkey samples, with reliable data to 25 pg/mL in plasma. This method is presented as a novel approach to the determination of N‐0923, and as a starting point for further development.
Internal ion impact ionization for Fourier‐transform ion cyclotron resonance
Authors: Wood Troy D. , Marshall Alan G. , Schweikhard Lutz 
Published: May 2005

AbstractA general scheme for ionization and fragmentation of ions in Fourier‐transform ion cyclotron resonance mass spectrometry (FT‐ICRMS) is introduced. The technique is based upon excitation of high‐frequency (i.e. lowmass) primary ions (e.g. N, Al+, H2O+·) which may be generated by standard ionization methods (e.g. electron ionization or laser desorption) inside the trap. Generation of the primary ions is followed by excitation of their cyclotron motion to high translational energy to serve as projectile ions. The projectiles serve two functions: to ionize neutral gas atoms and/or molecules (secondary ions) within the trap internal ion impact ionization (IIII), and to collisionally activate the secondary ions to induce fragmentation. Ionization by IIII is analogous to charge‐exchange ionization, in which a primary ion reacts with neutral analyte to produce ionization. When the projectile ions' cyclotron orbits are not excited (even for very long delay periods between ionization and detection), lower ion abundances are observed for the secondary ions derived from the neutral analyte(s), verifying that high energy ion impact must be responsible for the relatively high ion abundances observed when projectile cyclotron motion is excited: i.e., the mechanism of IIII is likely to be high‐energy charge exchange. Several advantages of the new technique include: accessibility of very high impact energy (keV) in FT‐ICRMS in both the laboratory and the center‐of‐mass frames of reference; ease in controlling the average energy transferred from projectiles to sample neutrals by moderation of the projectile ion's cyclotron radius; and the high ion‐molecule reaction rates attainable in FT‐ICR due to the long path length for trapped primary projectile ions at low pressure. Theory of ion formation and the problems associated with this technique (e.g. formation of secondary ions at different pre‐excitation ICR orbits) are discussed.
In situ analysis of a new perylene quinone in lichens by Fourier‐transform laser microprobe mass spectrometry with external source
Authors: Mathey Annick , Van Roy Wim , Van Vaeck Luc , Eckhardt Gert , Steglich Wolfgang 
Published: May 2005

AbstractThe application of Fourier‐transform laser microprobe mass spectrometry to lichens is described. The in situ detection of a new perylene quinone in samples of the tropical species Laurera sanguinaria Malme and Graphis haematites Fée was achieved with minimal specimen preparation. The high mass resolution and mass accuracy of the instrument eliminates the need for additional characterization of the isolated substances by high resolution electron impact mass spectrometry and direct introduction probe.
Mass spectrometric investigation on some pyrilium salts by different. Ionization methods and metastable ion studies
Authors: Hadjieva P. , Deligeorgiev T. , Fontana S. , Catinella S. , Traldi P. 
Published: May 2005

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 achieved.
A review of the collision‐induced dissociations of deprotonated dipeptides and tripeptides. An aid to structure determination
Authors: Waugh Russell J. , Bowie John H. 
Published: May 2005

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‐terminal positions.
Selective injection of laser desorbed ions into a quadrupole ion trap with a filtered noise field
Authors: Garrett A. W. , Cisper M. E. , Nogar N. S. , Hemberger P. H. , Goeringer Douglas E. 
Published: May 2005

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 target m/z ions 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 interrogation is demonstrated.
The application of capillary electrophoresis/mass spectrometry using negative‐ion electrospray ionization to areas of importance in the textile industry
Authors: Tetler Lee W. , Cooper Paul A. , Carr Chris M. 
Published: May 2005

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 methods.
Optimization of skimmer voltages of an electrospray ion source coupled with a magnetic sector instrument
Authors: Murata Hiroshi , Takao Toshifumi , Shimonishi Yasutsugu , Matsuo Takekiyo 
Published: May 2005

AbstractAn electrospray ion source designed for a magnetic sector instrument usually has two skimmers, which are located behind a capillary exit with separate pumping stages to reduce the pressure from that of ambient air to a valve suitable for the sector instrument. This work describes an evaluation of these two skimmer voltages with respect to the charge‐state distributions and the focusing efficiency of ions. The skimmer voltages were found to be closely related to the m/z values of the detected ions. The optimal difference voltage between skimmers 1 and 2 increased in proportion to the m/z values of the ions, irrespective of the molecular masses of the associated substances. This phenomenon is ascribable to the ion‐focusing effect in this region rather than to the effects of energetic collisions in the region of the skimmers, and suggests that the skimmer voltages should be adjusted in accordance with the m/z values of the detected ions for efficient acquisition of all distributed ions. The work demonstrates the functional role of the skimmers in electrospray ionization mass spectrometry with a magnetic sector instrument by examining several types of peptides and proteins, as well as an analysis of a complex mixture of peptides.
Influence of laser focusing in matrix‐assisted laser desorption/ionization
Authors: Riahi Karim , Bolbach Gérard , Brunot Alain , Breton Francis , Spiro Marenglen , Blais Jean‐Claude 
Published: May 2005

AbstractThe influence of laser focusing on the target in matrix‐assisted laser desorption/ionization (MALDI) has been studied. The emission of stable and metastable molecular ions of bovine insulin depends on both the laser energy and the distance between the target and the laser focal plane. The results clearly show that the laser fluence is the important parameter in MALDI. The fluence threshold of metastable‐ion emission is higher than that of stable‐ion emission. Beyond this threshold, the emission of stable ions reaches a plateau. This is due to the spatial inhomogeneity of the laser energy distribution. A phenomenological model including two fluence thresholds for the stable‐ and metastable‐ion emission has been developed and compared to the experimental data.
The use of low‐energy collisionally activated dissociation negative‐ion tandem mass spectrometry for the characterization of dog and human urinary metabolites of the drug BW 1370U87
Authors: Taylor Lester C. E. , Johnson Robert L. , John‐Williams Lisa St. , Johnson Tom , Chang Sai Y. , Baillie T. A. 
Published: May 2005

AbstractLiquid chromatography (LC) combined with atmospheric pressure chemical ionization mass spectrometry was used to identify phase I and II metabolites of the drug BW 1370U87 in dog and human urine. Additional analysis of individual high‐performance liquid chromatograph fractions collected from dog urine by combined gas chromatography/mass spectrometry identified one metabolite which was not detected by LC/MS methods. Using negative‐ion LC/MS, the majority of BW 1370U87 metabolites in human urine were identified as glucuronic acid conjugates of phase I oxidative metabolites. The negative‐ion fragmentation produced by low‐energy collisionally activated decomposition (CAD), studied by tandem mass spectrometry experiments, confirmed that these compounds were drug‐related and allowed metabolite structures to be assigned. Product‐ion spectra of the metabolites were dominated by the loss of neutral molecules from even‐electron deprotonated [M − H]− ions.
Collision‐induced dissociation of some protonated peptides with and without mass selection
Authors: Hamdan Mahmoud , Curcuruto Ornella 
Published: May 2005

AbstractCollision‐induced dissociation (CID) of several protonated peptides formed by positive‐ion electrospray (ES+) and by Cs+ fast‐ion bombardment are reported. The CID spectra of ions formed by the first ionization method were effected at elevated extraction cone voltages within the ion source of a single quadrupole instrument, while linked‐fields‐scan measurements at constant B/E of ions formed by the latter technique were performed within the collision cell of a trisector instrument. For molecular masses below 1000 Da, the two sets of spectra yielded identical sequencing information; however, for higher molecular masses the similarity was less evident. This divergence between the two sets of measurements is partially attributed to dominant doubly charged ions and less efficient dissociation of sodium adduct ions at elevated cone voltages.
A comparison of the mass spectrometric behaviour of trimethylindium adducts with N,N,N′‐triathylethylenediamines and of the related dimethylindium N,N,N′‐trialkylethylenediamido derivatives
Authors: Carta Giovanni , Rossetto Gilberto , Marco Nadia Di , Zanella Pierino , Favretto Donata , Traldi Pietro 
Published: May 2005

AbstractThe electron ionization mass spectrometric behaviour of dimethylindium N,N,N′‐trialkylethylenediamides and, for comparison, of trimethylindium adducts with the related N,N,N′‐trialkylethylenediamines, is discussed. The extensive decomposition processes observed under fast‐atom bombardment conditions are rationalized in terms of the condensed‐phase reactivity of the compounds under study.
An inductive detector for time‐of‐flight mass spectrometry
Authors: Park Melvin A. , Callahan John H. , Vertes Akos 
Published: May 2005

AbstractIn this paper we describe the underlying principles of, and demonstrate some of the attributes of, an inductive detector for use in time‐of‐flight mass spectrometry. Unlike a microchannel plate detector, the detection efficiency of the inductive detector is not dependent on ion velocity. Also, the inductive detector cannot be saturated in the same manner as a microchannel plate detector. Because the inductive detector detects only charged species, the neutral species normally observed in linear time‐of‐flight matrix‐assisted laser desorption/ionization spectra do not appear in spectra obtained with the inductive detector. Further, price and availability of the material needed to fabricate an inductive detector are virtually independent of detector size. Perhaps one of the most important features of the inductive detector is that it is a largely non‐destructive detector.
Mass spectra of some 2,4‐disubstituted 1,3‐cyclopentanediones
Authors: Lazarević Zvjezdana , Vorkapić‐Furač Jasna , Tralić‐Kulenović Vesna 
Published: May 2005

AbstractA study of the electron impact mass spectrometry is reported for eight, stable, previously synthesized, enolic isomers of 2‐aroyl‐4‐aracyl‐1,3‐cyclopentanediones.
Analysis of neuropeptides by perfusion liquid chromatography/electrospray ion‐trap mass spectrometry
Authors: Lin Hung‐Yu , Voyksner Robert D. 
Published: May 2005

AbstractPerfusion high‐performance liquid chromatography (HPLC) combined with electrospray ion trap mass spectrometry (ITMS) was evaluated for the determination of neuropepetides in plasma. Perfusion HPLC offers the capability of resolving neuropeptides spiked into plasma in 5 min compared to the 30–60 min separations performed on packed capillary C18 columns. Electrospray combined with the ITMS provides the ability to ionize these neuropeptides and mass analyze them with high sensitivity and specificity. Sub‐picomole quantities of neuropeptides injected on‐column could be specifically detected in a plasma matrix. The electrospray‐ITMS mass spectrum of each neuropeptide showed multiply charged ions which could be used to determine or confirm their molecular weights.
The application of electrospray and neutral‐loss mass spectrometry to the identification of the metabolites of S12813 in rat liver slices
Authors: Brownsill Robin , Combal Jean‐Philippe , Taylor Albert , Bertrand Marc , Luijten Wim , Walther Bernard , Games D. E. 
Published: May 2005

AbstractThe metabolism of S12813, (3‐{2‐[4‐phenyl piperazin‐1‐yl] ethyl}‐2‐oxo‐2,3‐dihydro oxazolo [4, 5‐b] pyridine chlorohydrate), in rat liver slice incubates was examined by high performance liquid chromatography combined with mass spectrometry. Electrospray ionization was used together with tandem mass spectrometric techniques of analysis (MS/MS). Polar phase I and phase II metabolites were identified as C‐oxidation products, which were then conjugated to form either sulphate or glucuronide metabolites. On the basis of the identifications made, a metabolic pathway of S12813 in rat liver slices has been proposed.
Measurement of isotope effect on photodetachment cross‐sections of OH− and OD− by Fourier‐transform ion cyclotron resonance mass spectrometry
Authors: Naito Yasuhide , Ueno Hitoshi , Huramatsu Eiji , Inoue Masao 
Published: May 2005

AbstractIsotope effect on photodetachment cross‐sections of OH− and OD− ions was studied using a Fourier‐transform ion cyclotron resonance mass spectrometer. The ions were produced by electron impact from a mixture of H2O and D2O gases, trapped in a cylindrical cell and irradiated by a 337 nm photon beam from a nitrogen pulsed laser. Intensities of both ions were measured simultaneously with and without irradiation. This allowed the determination of the ratio of the photodetachment cross‐sections of OH− and OD− ions without knowledge of the photon flux intensity and the geometrical overlap factor of laser beam and ion cloud in the cell. From the present result the difference in the equilibrium internuclear distances between OH− and OH was estimated as r(OH−) r(OH) ≈︁ −0.0074 Å.
Matrix‐assisted laser desorption/ionization: Dependence of the ion yield on the laser beam incidence angle
Authors: Westman Ann , Huth‐Fehre Thomas , Demirev Plamen , Bielawski Jacek , Medina Nelson , Sundqvist Bo U. R. , Karas M. 
Published: May 2005

AbstractSome basic properties of matrix‐assisted laser desorption/ionization (MALDI) have been investigated by varying the angle between the pulsed UV‐laser beam and the target surface, thus determining its influence on the MALDI process. The minimum deposited laser energy needed for protein ion production (the threshold energy) and the protein‐yield dependence on the laser energy have been determined for incidence angles between 35° and 60° with respect to the target surface normal. The measurements demonstrate that neither the threshold energy nor the dependence of the protein yield on the laser energy vary with the incidence angle within the range studied. Hence the corresponding parameters that involve the area of irradiation, namely the threshold laser fluence as well as the ion‐yield dependence on fluence have a cosine dependence on the incidence angle. Furthermore, the threshold energy at constant incidence angle scales with the mass of the analyte molecule for proteins in the range from 5700 to 66 000 u.