bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrospray mass spectrometric studies of some phosphonium cations
Authors: Colton Ray , Traeger John C. , Harvey Justin 
Published: May 2005

AbstractA series of methylphosphonium cations derived from mono‐ and polyphosphines were generated by interaction of the phosphine with methyl iodide. Electrospray mass spectra of the cations were obtained directly from dichloromethane–methanol solutions. In all cases the intact phosphonium cations were observed, often as the base peak, emphasizing the ‘soft’ nature of this type of ionization. Some of the polyphosphines showed additional peaks at m/z 16 and 32 units higher than the molecular ions due to oxidation of the non‐methylated phosphine groups. Collisionally activated dissociation mass spectra show a consistent mode of fragmentation with the formation of alkene ions being dominant. Where comparisons arc possible, there is a close correlation with the electron impact mass spectra of the neutral phosphines.
Decompositions of ammonium adducts of some isomeric sesquiterpene alcohols under collisional activation
Authors: Madhusudanan K. P. , Srivastava Rashmi , Kulshreshtha D. K. , Fraisse D. 
Published: May 2005

AbstractThe decompositions of the ammonium adducts of some sesquiterpene alcohols have been studied using collisional activation mass spectrometry. Losses of ammonia and water are the two primary fragmentation pathways of these adduct ions. Some of the isomeric pairs show differences in the abundances of the fragment ions, whereas others give similar ion abundances in the two isomers.
Electrospray mass spectrometry of lanthanide β‐diketone complexes. II‐Ligand‐exchange processes involving acetate ions and Ln(tfc)3 complexes
Authors: Curtis Jonathan M. , Derrick Peter J. , Schnell André , Constantin Emilie , Gallagher Richard T. , Chapman John R. 
Published: May 2005

AbstractElectrospray ionization on Ln(tfc)3 complexes (Ln = Eu, Yb; tfc = D‐3‐trifluoroacetylcamphorate) was performed with samples dissolved in methanol–water containing acetic acid. The spectra were obtained with a four‐sector mass spectrometer. The mass spectra exhibit ions containing tfc ligand in addition to ions with acetato ligand. Electro‐spray and tandem mass spectra are presented.
Mass spectrometric studies of platinum(II) complexes of carbonyl‐stabilized arsonium ylides
Authors: Facchin G. , Zanotto L. , Seraglia R. , Traldi P. 
Published: May 2005

AbstractA fast atom bombardment (FAB) mass spectrometric study was carried out on the two O‐coordinated carbonyl‐stabilized arsonium ylide Pt(II) complexes {(dppe)PtCI[OC(R)C(H)AsPh3]}BF4 ((dppe) = Ph2PCH2CH2Ph2; R = CH3 (1), OCH3 (3)) and on the two corresponding C‐coordinated isomers {(dppe)PtCl[Ph3AsC(H)COR]}BF4 (R = CH3 (2), OCH3 (4)). The mass spectral analysis of complexes 1 and 2 reveals that it is possible to distinguish the two isomeric forms mainly on the basis of the relative abundance of the protonated triphenylarsine oxide at m/z 323 while the different coordination modes of the ylide in complexes 3 and 4 are evidenced by the different fragmentation pathways of these two derivative;. Further, the reaction between [(dppe)PtCl]2(BF4)2 and the appropriate ylide performed under FAB conditions indicates that in both cases the first complex formed is the C‐coordinated isomer, in agreement with that observed in the condensed phase.
Calculation of the kinetic energy release of charge separation processes
Authors: Vékey Károly , Pócsfalvi Gabriella 
Published: May 2005

AbstractKinetic energy release (KER) was studied by experimental methods and semiempirical (MNDO and AM1) molecular orbital calculations in the case of various charge separation processes: loss of a methyl ion from [CH3C4CH3]2+, [CH3C3CH3]2+ and [N,N‐dimethyl‐p‐phenylenediamine]2+. It was found that the KER corresponding to the width of a dish‐topped peak at half‐height is very close to the mean KER of the process. The calculated potential energy curves of these reactions show significant reverse critical energies, a large part of which was found to be due, in agreement with conventional assumptions, to electric repulsion between the two separating singly charged products. The bond order between the two separating ions is nearly zero in the transition state, so exchange of internal energy between them is unlikely. These explain the good agreement between the (calculated) reverse critical energy and the measured kinetic energy release.
Comparison of ion trap and sector instruments in the study of fragmentation patterns of coumarins
Authors: Podda G. , Bonsignore L. , Loy G. , Catinella S. , Traldi P. 
Published: May 2005

AbstractThe mass spectra of a series of differently substituted coumarins were obtained by high‐ and low‐energy collision experiments. The results obtained by the two techniques show peculiar differences, mainly in the presence, under ion trap conditions, of a high relative abundance of M+·. The results support the validity of the ion trap technique basic studies of mass Spectrometry.
Mass spectrometry of some fluorinated alcohols
Authors: Carbini M. , Conte L. , Gambaretto G. , Catinella S. , Traldi P. 
Published: May 2005

AbstractThe 70 eV electron impact mass spectrometric behaviour of some fluorinated alcohols, i.e. 2‐fluoroethanol, 2,2,2,‐trifluoroethanol, 2,2,3,3‐tetrafluoropropan‐1‐ol and 1.3‐difluoropropan‐2‐ol, was studied in detail by means of mass‐analysed ion kinetic energy Spectrometry, deuterium‐labelling experiments and comparison with unfluorinated analogues. Composite metastable peaks related to HF losses were rationalized by invoking the presence of two concurrent decomposition pathways, the first consisting in a 1,2‐elimination and the second requiring the implication of hydroxyl hydrogen. This last process and other decomposition routes suggest the presence of H. bridging between the hydroxyl oxygen atom and fluorine.
Liquid chromatography/thermospray mass spectrometry of monosaccharides and their derivatives
Authors: Lipták Miklós , Dinya Zoltán , Sztaricskai Ferenc J. , Litkei György , Jekö Jáozsef 
Published: May 2005

AbstractThermospray (TSP) mass spectrometry has proved to be a useful technique for analysing various highly polar compounds. The use of a quadrupole mass spectrometer equipped with a thermospray/plasmaspray interface in the analysis of more than 30 monosaccharides and sugar derivatives is described. A 1:1 mixture of methanol or acetonitrile and 0.1 M aqueous ammonium acetate as eluent at 1 cm3 min−1 affords the best results. The correct setting of the capillary tip temperature and repeller voltage was fundamental for the ionization of carbohydrates. The/optimum values of these parameters were 240–250°C and 220–240 V, respectively. The thermospray mass spectra of most carbohydrates exhibit strong [M + NH4]+ ions which provide molecular mass information. The underivatized and derivatized monosaccharides could be grouped according to the presence or absence and the relative abundances of [M + NH4 − H2O]+, [M + H]+ and [M + NH4]+ ions.
Electron impact ionization mass spectra of some substituted dipyrido[1,2‐a:4,3‐d]pyrimidinones
Authors: Mäki Esa , Pihlaja Kalevi , Huber Imre , Fülöp Ferenc , Bernáth Gábor , Vainiotalo Pirjo 
Published: May 2005

AbstractThe electron impact ionization mass spectra of dipyrido [1,2‐a:4,3‐d]pyrimidinones are strongly influenced by the degree of aromaticity of the fused rings. The molecular ions of the compounds are fairly stable. The main routes of fragmentation involve formation of the [M – H]+ ion and loss of substituents, H2CN˙, CO and alkyl radicals.
Fast atom bombardment mass spectrometric study of alkali metal cationized unsaturated C‐glycosides
Authors: Brakta Mohamed , Chaguir Brahim , Sinou Denis , Becchi Michel , Bobenrieth Marie Joëlle , Banoub Joseph 
Published: May 2005

AbstractFast atom bombardment mass spectrometry of alkali metal cationized unsaturated C‐glycosides is a useful method for the determination of the molecular masses of these compounds. The mass‐analyzed ion kinetic energy and collision‐activated dissociation mass‐analyzed ion kinetic energy spectra of the pairs of anomers are distinguishable and are characteristic of each anomer.
Ion–molecule reactions by chemical ionization: Determination of rate constants
Authors: Torroni Sandro , Innorta Giuseppe , Scagnolari Francesco , Foffani Antonio , Curcuruto Ornella 
Published: May 2005

AbstractTungsten hexacarbonyl was studied by chemical ionization mass spectrometry using carbon monoxide as reagent gas. The variation of the relative abundances of ions as a function of reactant gas pressure was used for evaluating the relative rate constants for consecutive reactions. The results are in agreement with the rate constant ratios obtained from ion trap mass spectrometric data.
Protonation susceptibility and fragmentation capability of functional groups in chemical ionization mass spectrometry of simple bifunctional compounds. Semi‐quantitative interpretation of spectra
Authors: Nakata Hisao , Kadoguchi Kenji , Konishi Hideyuki , Takeda Naohito , Tatematsu Akira 
Published: May 2005

AbstractPositive‐ion, methane‐mediated chemical ionization mass spectra were measured for simple bifunctional aromatic compounds of the type m‐XCH2C6H4CH2Y, where X = NH2 and N(CH3)2, and Y = OH and OCH3. Essentially only three peaks of ions, [MH]+, [MH – XH]+ and [MH – YH]+, have appeared for each compound. Since the two functional groups XCH2– and YCH2– do not interact with each other after protonation or after fragmentation, they are assumed to be protonated and to undergo fragmentations independently. The relative protonation susceptibility and fraction of fragmenting [MH]+ can be estimated for each functional group in these compounds. A semi‐quantitative interpretation of the observed spectra is presented.
Sputtered ammonium dinitramide: Tandem mass spectrometry of a new ionic nitramine
Authors: Doyle Robert J. 
Published: May 2005

AbstractThe recently synthesized ammonium dinitramide (ADN) is an ionic compound containing the ammonium ion and a new oxide of nitrogen, the dinitramide anion (O2NNNO2−). ADN has been investigated using high‐energy xenon atoms to sputter ions directly from the surface of the neat crystalline solid. Tandem mass spectrometric techniques were used to study dissociation pathways and products of the sputtered ions. Among the sputtered ionic products were NH4+, NO+, NO2−, N2O2−, N2O, N3O4− and an unexpected high abundance of NO3−. Tandem mass spectra of the dinitramide anion reveal the uncommon situation where a product ion (NO3−) is formed in high relative abundance from metastable parent ions but is formed in very low relative abundance from collisionally activated parent ions. It is proposed that the nitrate anion is formed in the gas phase by a rate‐determining isomerization of the dinitramide anion that proceeds through a four‐centered transition state. The formation of the strong gas‐phase acid, dinitraminic acid (HN3O4), the conjugate acid of the dinitramide anion, was observed to occur by dissociation of protonated ADN and by dissociation of ADN aggregate ions with the general formula [NH4(N(NO2)2)n] NH4+, where n = 1–30.
Influence of instrumental parameters and sample preparation on mass‐analysed ion kinetic energy spectra with fast atom bombardment exemplified with the oxonium ion of peracetylated ribopyranose
Authors: Blok‐Tip Leonore , Heerma Wigger , Haverkamp Johan 
Published: May 2005

AbstractWhen mass‐analysed ion kinetic energy (MIKE) spectra are required to discriminate between isomeric ions formed under conditons of fast atom bombardment (FAB) in the ion source, severe interference may be observed. The interfering peaks in MIKE spectra obtained with a reversed‐geometry instrument can arise from different sources. Moreover, the intensity distribution of the true ions from the selected precursor ion may depend strongly on the instrument being used. This means that the FAB–MIKE or collisionally induced dissociation (CID) spectrum is not an absolute characteristic of a particular ion. The [M + H − HOAc]+ ion in the spectrum of peracetylated ribopyranose is used as an example to illustrate this and to trace and discuss the origin of the phenomena observed.
Reactions of propene and cyclopropane radical cations with neutral ethylene
Authors: Vollmer D. L. , Gross M. L. 
Published: May 2005

AbstractThe gas‐phase reactions of propene and cyclopropane radical cations with neutral ethylene were investigated by using Fourier transform, chemical ionization and tandem mass spectrometries. Both reactions form covalent C5H10 adduct ions. The adduct ions are hypothesized to form initially as distonic radical cations that isomerize via a substituted cyclopropane intermediate and are detected as the most stable C5H10 isomer, the 2‐methylbut‐2‐ene radical cation. The rate constant for each reaction is approximately 20% of the theoretical collision rate, indicating that product ions are formed in one out of every five collisions of the C3H6 radical cations with neutral C2H4.
A new ion source for liquid chromatography/thermospray mass spectrometry with a magnetic sector field mass spectrometer
Authors: Hau J. , Nigge W. , Linscheid M. 
Published: May 2005

AbstractA new and simple ion source for thermospray on a sector field mass spectrometer has been designed, which is based on two sets of electrostatic quadrupole lenses to focus the divergent ion beam that emanates from the extraction cone into the ion source region. To illustrate the performance of the source, the on‐line separation and detection of a few samples are shown using scanning and single‐ion monitoring techniques. Examples are a mixture of phena‐zines and samples of caffeine and adenosine. With single ion motoring, 5 ng of a phenazine, 300 pg of caffeine and ∼1 ng of adenosine were detected. Further, it is shown that declustering and collision‐induced fragmentation occur inside the sampling cone, resulting in peak broadening on the low‐mass side of signals of protonated species. Minimizing the collision‐induced dissociation of erythromycin was used to optimize the flow‐rate of the liquid chromatograph and the pressure in the source housing.
Dependence on scattering angle of the internal energy distribution of products of charge‐changing collisions
Authors: Riederer D. E. , Lu L. , Cooks R. G. 
Published: May 2005

AbstractThe internal energy distributions arising from charge‐changing collisions were measured as a function of scattering angle, θ, for the ‘thermometer’ molecule W(CO)6. The experiments were performed by modifying a reverse‐geometry mass‐analyzed ion kinetic energy (MIKE) spectrometer by adding angle‐resolving slits which allow measurement of the scattering angle in the non‐focusing plane of the instrument. Charge exchange of W(CO) with benzene to give W(CO), and charge stripping of W(CO) on collision with O2 to give W(CO), were studied at 6 keV with the product ions being collected over laboratory scattering angles selected in the range 0–0.60°. The results show that charge‐changing collisions accompanied by scattering have the potential for depositing extremely large internal energies. The observation of the W(CO)2+ ion formed in dissociative charge stripping of W(CO) shows that it is possible to deposit at least 27 eV into the colliding W(CO) ion; of this energy, 15 eV is used for the charge‐stripping process, leaving 12 eV of internal energy in the nascent W(CO). Even greater internal energies (more than 15 eV) can be deposited into scattered W(CO) produced by charge exchange of the doubly charged ion. The availability of such high internal energies has potential use in causing dissociation of refractory ions such as those of biomolecules. The average internal energy, εAVE, deposited increases with the scattering angle at a rate of 10 eV degree−1 for charge exchange, and at approximately 5 eV degree−1 for charge stripping and for simple collision‐induced dissociation (CID). This observation suggests that non‐zero angle charge stripping and CID may occur via similar mechanisms in which direct vibrational activation occurs in small impact parameter collisions which also lead to angular scattering. The higher internal energies and larger εAVE vs. θ dependence observed for charge exchange are consistent with the formation of the products upon a highly repulsive surface associated with coulombic repulsion between the separating products.
Chemical ionization mass spectrometry of C2H4/C2D4 mixtures using iodine as reagent gas
Authors: Gable Kevin P. , Phan Thuy N. , Griffin Don 
Published: May 2005

AbstractGas‐phase ionization of ethylene with positive ions generated from molecular I2 leads to the formation of the iodiranium ion, m/z 155. No fragmentation or crossover is seen from a mixture of C2H4 and C2D4, although a net isotope effect (I155/I159 = 1.41 ± 0.02) is observed.
Mass spectra of aromatic 3‐methylisoxazolo‐ and 2‐methyloxazolopyridines
Authors: Ponticelli Fabio , Giomi Donatella , Papaleo Sandro , Tedeschi Piero 
Published: May 2005

AbstractThe fragmentation patterns of aromatic 3‐methylisoxazolo‐ and 2‐methyloxazolopyridines were investigated by high‐resolution mass spectrometry and collisionally activated B/E and B2/E linked scans. The isoxazolopyridines give mass spectra near identical with those of the corresponding oxazolopyridines, both showing mainly a competitive loss of CO and CH3CN from the molecular ion. However, the ratio of these concomitant pathways depends substantially on the type of fusion between the five‐ and six‐membered rings.
Large translational energy loss and scattering in collision‐induced dissociation processes
Authors: Vékey Károly , Czira Gábor 
Published: May 2005

AbstractLarge translational energy losses (TEL) of between 10 and 35 eV have been observed and studied in the collision‐induced decomposition (CID) of some CsI clusters, Cs3I2+, Cs5I4+ and Cs14I13+. The TEL was found to depend strongly on the collision energy. In some cases the TEL was greater than the centre of mass collision energy, showing that recoil energy of the target is undoubtedly important. The results suggest further that, at least for projectiles consisting of heavy atoms, most of the TEL is due to a scattering process. From the TEL and CID peak shapes approximate collision angle distributions were also determined.
Tandem mass spectrometric approaches for the analysis of alkylguanines in human urine
Authors: Cushnir J. R. , Naylor S. , Lamb J. H. , Farmer P. B. 
Published: May 2005

AbstractHuman exposure to carcinogenic alkylating agents can lead to the formation of covalently bound adducts in DNA, some of which are excreted in urine as alkylated purines following DNA degradation and repair. Tandem mass spectrometric methods have been developed for the qualitative and quantitative determination of such alkylpurines in human urine. Short‐chain alkyl‐ and hydroxyalkylguanines have been synthesized with the substituents at theN‐7‐,O6‐ andN2‐positions of guanine. Examination of the product ion scans of their molecular ions (electron impact (EI) ionization) revealed that the ion atm/z151, [guanine]+, was common to all of the alkylguanines studied, with the exception of the methylated analogues. Precursor ion scans of this ion on partially purified human urine extracts showed the presence of several ions (e.g.m/z179, 195) which were consistent with molecular ions for alkylguanines. The presence of these and other constituents was confirmed by product ion spectra of molecular ions (EI and fast atom bombardment), and by high‐performance liquid chromatographic separation prior to tandem mass spectrometry (MS/MS). Evidence was obtained for the presence ofN‐7‐methyl‐,N2‐dimethyl‐,N2‐dimethyl‐,N2‐ethyl‐ andN‐7‐(2‐hydroxyethyl)guanine. Quantitative methods were established for these five alkyl guanines using gas chromatography mass spectrometry (GC/MS) and GC/MS/MS. Deuterated internal standards were synthesized and added to the urine prior to extraction of alkylpurines by Sep‐Pak cartridge chromatography. The products were converted into theirtert‐butyldimethylsilyl derivatives and analysed by selected ion monitoring (SIM) of [M – 57]+or by multiple reaction monitoring (MRM) of the fragmentation M+˙→ [M – 57]+. The MRM method yielded values forN‐7‐methylguanine of 2.57 ± S.D. 1.32 mg day−1(n= 6),N2‐methylguanine of 0.31 ± 0.10 mg day−1(n= 10) andN2‐dimethylguanine of 0.21 ± 0.23 mg day−1(n= 10).N2‐Ethyl‐ andN‐7‐(2‐hydroxyethyl)guanine could only be detected by SIM at levels of ∼0.5 and 2 μg day−1, respectively. The MRM analyses, although inherently less sensitive than the SIM analyses, exhibit greater selectivity and consequently fewer contaminant ions.
Boundary‐effect activated dissociation in ion trap tandem mass spectrometry
Authors: Creaser C. S. , O'Neill K. E. 
Published: May 2005

AbstractThe potential of boundary‐effect activated dissociation (BAD) in ion trap tandem mass spectrometry (MS/MS) is discussed. Several classes of compounds were investigated and the BAD product ion tandem mass spectra were compared with those from collisionally activated dissociation (CAD) where an auxilliary r.f. ‘tickle’ voltage is used. The energy deposition in BAD MS/MS is generally lower than that for optimized CAD, but the experiments are easier to perform. An example of the BAD MS/MS of C10 alkylbenzenes and benzothiophene in diesel fuel using gas chromatographic introduction and predicted r.f. and d.c. voltages is presented.
The potential of composite pyrolysis gas chromatographic mass spectra in the study of lignocellulosics
Authors: Reeves James B. , Galletti Guido C. 
Published: May 2005

AbstractThe objective of this work was to evaluate the use of composite mass spectral (CMS) data from pyrolysis gas chromatography/mass spectrometry (PY–GC/MS) for lignocellulosic materials. Various forages, by‐products and fiber fractions derived from them were examined as CMS by PY–GC/MS. The PY–GC/MS system consisted of a heated platinum filament, a capillary gas chromatograph and an ion trap detector (ITD) mass spectrometer operated under electron impact conditions. Mass spectra were then composited in several ways by summing all the mass spectra acquired within retention times corresponding to major product classes. CMS data were entered in a dedicated library and compared using the ITD library editor software. The usefulness of such a simple procedure for studies related to lignocellulose analysis, such as forage recognition, development of analytical methods and digestibility/maturity correlation, is discussed.
Effects of functional group interactions on the dissociation reactions of protonated amino alcohols
Authors: Eichmann Erika S. , Brodbelt Jennifer S. 
Published: May 2005

AbstractThe dissociation reactions of protonated amino alcohols were examined in a quadrupole ion trap mass spectrometer. Multi‐stage collision‐induced dissociation techniques were used to characterize the ions and their fragments and to assist in the determination of the dissociation mechanisms. In addition, semi‐empirical calculations were used to rationalize the results on the basis of the thermodynamics of the reactions in question. The reaction of special interest was the double elimination of water and ammonia. For this high‐energy process, it is shown that the initial deamination step is the thermodynamically favored one in most cases. The enthalpies of formation for the various precursor and product ions and also those for some of the reaction intermediates were estimated using molecular modelling and semi‐empirical calculation methods. The values obtained indicated that the minimum endothermicity of the sequential deamination–dehydration reaction ranges from 209 to 460 kJ mol−1 for the compounds studied here. Moreover, protonation at the amine site was found to be energetically favored by 38–192 kJ mol−1 over protonation at the hydroxyl site.