bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic boronates in the mass spectrometry of ecdysteroids
Authors: Vaisar Tomáš , Píš Jaroslav
Published: May 2005

For the structural elucidation of ecdysteroids a reaction with phenylboronic acid has been employed. This reaction takes place exclusively on the C20,C22 diol moiety, thus facilitating fast and easy detection of this moiety in the molecule od ecdysteroid. This derivatization also redirects fragmentation to C17/C20 bond cleavage with charge retention on both fragments enabling assessment of the structure both of the steroid nucleus and of the side‐chain. Possible reaction of phenylboronic acid with the diol moiety of the glycosyl group of the glycoside od ecdysteroid, producing di‐adduct, is demonstrated; participation of the 5β‐hydroxy group of 5β,20‐dihydroxyecdysone in the formation of such a di‐adduct is discussed; and the role of theenol form of the 6‐carbonyl group is proved.
Laser mass spectrometry of polydeoxyribothymidylic acid mixtures
Authors: Tang K. , Allman S. L. , Jones R. B. , Chen C. H. , Araghi S.
Published: May 2005

Matrix‐assisted laser desorption/ionization mass spectrometry has been used to mass analyze synthetic oligomers of poly‐T ranging in size from 20 to 100 nucleotides. Both positively‐ and negatively‐charged parent molecular ions were observed.
Mass spectral fragmentation processes in nitronaphthalenes. A study using tandem mass spectrometry and collision‐induced dissociation
Authors: Yinon Jehuda
Published: May 2005

Mass spectral fragmentation processes and pathways of a series of nitro, dinitro and trinitro derivatives of naphthalene have been studied. Collision‐induced dissociation mass spectra were obtained using a tandem BB mass spectrometer. Major fragmentation pathways included loss of NO2 from the molecular ion, followed by loss of NO and/or CO. Additional fragmentations included loss of OH from the molecular ion ion some of the compounds investigated.
Dimerization of the ketene cation radical in the gas phase
Authors: Dass Chhabil
Published: May 2005

The dimerization of the ketene cation radical was investigated by using tandem mass spectrometry. Ketene was ionized by low‐energy charge‐exchange with CS· reagent ions. The high‐pressure environment in the ion source permits collisional stabilization of the ion/molecule adduct, which was characterized by obtaining its collisionally activated dissociation (CAD) mass spectrum. Comparison with the CAD spectrum of diketene+· revealed that the structure of the adduct is identical with that of the ionized diketene species. The singly occupied molecular orbital‐lowest unoccupied molecular orbital (SOMO‐LUMO) interaction was invoked to explain the formation of the ion/molecule adduct.
New methods for computational ion structure evaluation by means of tandem mass spectrometry
Authors: Hayek Erich W. H. , Stanek Wolfgang , Krenmayr Peter
Published: May 2005

New methods are presented for the evaluation of ion structures and fragmentation pathways using tandem mass spectrometry (MS/MS) with low energy collision‐induced dissociation. As an aid for mass spectroscopists, they incorporate a PC software package (named PDNL, written in Turbo‐PASCAL 5.5 (Borland), running under DOS (Microsoft) with mouse‐control). A database of almost 300 low energy MS/MS spetra is available for library searches. It utilizes a new, intensity‐based matching algorithm fitting to the demand of MS/MS data. Computational methods have been developed for (i) the separation of the spectra of unresolved isobaric ions and evaluation of the ratio of the ion abundances, (ii) the evaluation of single‐collision spectra using the multi‐collisional data map, and (iii) the elucidation of collision‐induced dissociation fragmentation pathways. Principal component analyses of sets of at least eight MS/MS spectra were used for a quick comparison of these spectra and for a summary of inter‐ion relationships.
1993 directory of mass spectrometry manufacturers and suppliers
Authors: Lammert S. A.
Published: May 2005

A directory of companies which supply mass spectrometers and mass spectrometry components and services. This directory updates an earlier version.
The elusive HNCOH+ ion characterized by a double‐collision experiment in the mass spectrometer
Authors: McGibbon Graham A. , Terlouw Johan K. , Burgers Peter C.
Published: May 2005

Previous studies have shown that the gas‐phase protonation of isocyanic acid, HNCO, exclusively yields the N‐protonated ion, the aminoformylium ion, H2NCO+, 1, which is thermodynamically the most stable [H2, C, N, O]isomer. In the present paper it is shown that the O‐protonated species, the elusive isoformylaminylium ion, HNCOH+, 2, can be generated by successive degradation of ionized N‐methyl‐O‐methylcarbamate in a 3‐stage tandem (MS/MS/MS) type experiment: CH3NHC(O)OCH· → CH3NHCOH+· → HNCOH+· The species is identified from its characteristic collisional activation (CA) mass spectrum. From a comparison of the CA mass spectra of the2H‐labelled isotopomers DNCOH+ and HNCOD+ with that of the isomeric ion HDNCO+ it follows that collisionally excited ions (>400 kJ/mol) of 2 may isomerize into 1.
Differentiation of anomeric glycosyl azides using mass spectrometric methods
Authors: Kralj B. , Kramer V. , Žigon D. , Kobe J. , Štimac A.
Published: May 2005

Electron ionization (EI), chemical ionization and mass‐analysed ion kinetic energy (MIKE) spectra have been applied with the aim of obtaining an unambiguous differentiation between the anomeric 2,3‐O‐isopropylidene α‐and β‐D‐ribofuranosyl azide derivatives. The MIKE spectra of their metastable [M  CH3]+ ions, originating from EI, showed a decomposition pattern allowing distinction between the anomers. The origin of the ions in the EI mass spectra, supported by examination of the deuterium‐labelled derivatives, makes it possible to identify the actual azido group orientation in a particular anomer.
Negative‐ion fast‐atom bombardment tandem mass spectrometry for the structural study of polyether compounds: Structural verification of yessotoxin
Authors: Naoki Hideo , Murata Michio , Yasumoto Takeshi
Published: May 2005

We have examined the applicability of tandem mass spectrometry to the structural elucidation of polyether compounds. The polyether toxin named yessotoxin was isolated from scallops which were implicated in food poisoning. The toxin consists of fused polycyclic ethers as does ciguatoxin, and bears two sulfate esters in the molecule. The negative‐ion fast‐atom bombardment tandem mass spectrum of the toxin showed a series of ions due to fragmentation at positions characteristic of cyclic ethers. With the mass spectrometric data alone, we succeeded in assigning the number and location of eleven ether rings in yessotoxin, which agreed with those previously deduced by nuclear magnetic resonance studies.
A model for peak shape in slow‐scan‐rate quadrupole ion trap mass spectronnetry
Authors: Amster I. Jonathan
Published: May 2005

The results of calculations are presented that address the effect of the scan rate on peak shape and position for slow‐scan‐irate detection in the quedrupole ion trap. The calculations are based on a model for signal detection that account for the change in the number of ions in the trap as the ejection field sweeps across a peak. The calculations predict that reduced scan rates lead to peak narrowing, peak asymmetry, and a shift in the apparent mass in the in resulting mass spectrum.
In situ reduction suitable for matrix‐assisted laser desorption/ionization and liquid secondary ionization using tris(2‐carboxyethyl)phosphine
Authors: Fischer Wolfgang H. , Rivier Jean E. , Craig A. Grey
Published: May 2005

The suitability of the hydrochloride salt of tris(2‐carboxyethyl)phosphine (TCEP) for in situ reduction with matrix‐assisted laser desorption/ionization (MALDI) and liquid secondary ionization (LSI) mass spectrometry is evaluated. TCEP can be used to irreversibly reduce organic disulfldes to thiols in water and is active at an acidic pH. We found that TCEP was suitable for partial reduction of bovine insulin deposited on the target and mixed with either sinapinic acid in MALDI or glycerol and m‐nitrobenzyl alcohol in LSIMS. When TCEP was added to insulin deposited on the target without prior mixing of sinapinic acid the in situ MALDI protocol resulted in almost complete reduction.
Sequeince‐ion studies in peptides: The generation of C″ ions
Authors: van Dongen W. D. , de Koster C. G. , Heerma W. , Haverkamp J.
Published: May 2005

The mechanism for the formation of C″‐type ions from protonated peptides, produced under conditions of fast‐atom bombardment and rollisional activation was investigated. Comparison of the tandem mass spectra of the [M + H]+ ions of a model peptide and the corresponding [Md + D]+ ions, in which all exchangeable hydrogens are replaced with deuterium, revealed that neither the carboxylic hydrogen not a hydrogen from a nitrogen atom is involved in the process of migration of a hydrogen which leads to the formation of Cn″‐type ions. The most feasible position from which the transferred hydrogen originates is that at the first C‐atom in the side‐chain of the adjacent ainino acid.
Translational energy spectroscopy. I. Theory and practical considerations
Authors: Enos Christopher S. , Brenton A. Gareth
Published: May 2005

Non‐dissociative collision processes are classified and the accepted notation is given. The basic kinematics of binary collisions are derived and practical considerations based on Massey's adiabatic criterion together with the effects of pressure and temperature are discussed. A general description of instrumental developments and the performance achieved are given and the predictions of the Wigner spin conservation rule as regards the spectroscopic states of the products are summarized.
Analysis of cyclic nucleotide‐related enzymes by continuous‐flow fast‐atom bombardment mass spectrometry
Authors: Langridge James I. , Brenton A. Gareth , Walton Terence J. , Harris Frank M. , Newton Russell P.
Published: May 2005

Continuous‐flow fast‐atom bombardment mass Spectrometry has been developed to directly monitor cyclic nucleotide (substrate) and its product levels from an on‐going phosphodiesterase reaction. Analysis of cAMP and cCMP phosphodiesterase incubates have been performed where the temporal evolution of the enzymic reaction is monitored and the effect of enzyme concentration upon the rate of reaction determined. Quantitative data on the enzyme kinetics have been obtained, in the form of Lineweaver‐Burke plots, that are shown to correlate well with well‐established radiometric methods.
Applications of electrospray mass spectrometry to studies on the structural properties of ribonuclease A and ribonuclease B
Authors: Camilleri P. , Haskins N. J. , Rudd P. M. , Saunders M. R.
Published: May 2005

Deuterium‐exchange experiments were performed on ribonuclease A (RNase A) and its glycosylated form, ribonuclease B (RNase B), using electrospray ionization mass spectrometry. The number of exchangeable protons was found to be similar for both forms of the enzyme, indicating that the oligosaccharide moiety on RNase B does not exert any influence on protein conformation. Four main glycoform populations were identified in RNase B, each of which was homogeneous and associated with one phosphate group. Spectra for RNase A were heterogeneous due to the presence of 0–3 phosphate groups bound to the enzyme.
The collision‐induced fragmentations of deprotonated allyl alcohol and its monomethyl derivatives
Authors: Dua Suresh , Bowie John H. , Hayes Roger N.
Published: May 2005

Deprotonated allyl alcohol undergoes collision‐induced losses of H2, CH2O and C2H4 with minor hydrogen randomization occurring prior to or during these dissociations. A further fragmentation involves loss of methane: labelling studies (with CH2CHCD2O−) suggest that this loss is preceded by the equilibration CH2CHCD2O− ⇌ CD2CHCH2O−. The methyl homologues of allyl alcohol form isomeric C3H ions: the charge reversal spectra of these isomers confirm that CH2CHCH, CH2C̄CMe and HC̄CHMe are separate species, and also suggest that all three of the corresponding positive ions are formed on the charge‐reversal time‐scale.
Differentiation between selected pairs of tripeptide diastereomers by tandem mass spectrometry on a hybrid tandem mass spectrometer
Authors: Schwartz Brenda L. , McClain Robert D. , Erickson Bruce W. , Bursey Maurice M.
Published: May 2005

Low‐energy collisionally activated decomposition (CAD) and unimolecular decomposition of the [M + H]+ ions for X‐L‐Pro‐L‐Phe, where X is L‐Ala, D‐Ala, L‐Asp, or D‐Asp, allow easy differentiation between the LLL and DLL diastereomers. Tandem mass spectrometric (MS/MS) studies of the [M + H]+ ions formed by fast‐atom bombardment (FAB) at various ion kinetic energies (Elab values) on a hybrid tandem instrument produced ions of different intensities for the diastereomers. The ratio of NH3 to H2O loss is 0.3 for the L‐Ala peptide but 1.7 for the D‐Ala isomer at 5 eV. In some L‐Ala spectra, the [M + H − NH3]+ ion does not appear at all. The y2 ion is up to twice as abundant in the L‐Ala spectra as in the D‐Ala, while the b2 ion is somewhat more abundant for CAD of the D‐Ala peptide for most collision energies investigated. The D‐Asp peptide produces a b2 ion that is more than half‐again as abundant as in the case of the L‐Asp isomer, and an [M + H − H2O]+ ion that is up to twice as abundant in the D‐Asp CAD spectra as in those of the L‐Asp. The y1, a2, and phenylalanine immonium ions are each up to twice as abundant in the L‐Asp spectra as in those of the D‐Asp isomer. The major differences are correlated with force‐field calculations on hydrogen‐bonded tautomers.
Detection and characterization of fumonisin mycotoxins as their methyl esters by liquid chromatography/particle‐beam mass spectrometry
Authors: Young J. Christopher , Lafontaine Pierre
Published: May 2005

The diazomethane‐derived tetramethyl esters of fumonisins can be introduced readily into mass spectrometers using flow injection analysis or liquid chromatography (LC) via a particle‐beam interface to yield chemical ionization and electron‐ionization spectra. The esters of fumonisins B1, B2, and B3 were well resolved on a C18 reversed‐phase column when eluted with a gradient of water + methanol + acetonitrile in the presence of 0.05% trifluoroacetic acid. Enhancement of analyte transport through the particle‐beam interface to afford increased ion abundances was achieved by addition of carriers. Polyfunctional amino acid carriers, such as L‐glutamic acid or L‐serine, effected at least 100‐fold increases in sensitivity. In the LC mode, post‐column addition of aqueous L‐serine was the most advantageous because background interference was limited to lower masses, and because of higher solubility, and ease of cleaning.
Determination of saxitoxin by liquid chromatography/thermospray–mass spectrometry
Authors: Wils E. R. J. , Hulst A. G.
Published: May 2005

The determination of the paralytic shellfish poison saxitoxin by liquid chromatography/thermospray‐mass spectrometry (LC/TS‐MS) was investigated. It was found that a commercial sample contained an impurity, which was identified as the plasticizer tris(2‐butoxyethyl) phosphate. Spraying of saxitoxin in acid solution at pH 2 led to a useful TS mass spectrum, containing some fragment ions in addition to the protonated molecule. Using pentafluoropropionic acid as a counter‐ion, saxitoxin could be determined by LC/TS‐MS on a C18 re versed‐phase column. By injecting the relatively large volume of 1 mL, a concentration of 30 ng/mL could be measured.
Electron ionization‐tandem mass spectrometry of glycosphingolipids. Part II. The identification of a carbohydrate sequence corresponding to a novel repetitive blood group a heptaglycosylceramide
Authors: Holgersson Jan , Curtis Jonathan M. , Morris Michael R. , Teller Lee W. , Derrick Peter J. , Samuelsson Bo E.
Published: May 2005

In a previous paper, the presence in human kidney vein tissue of a novel blood group A heptaglycosylceramide based on the type‐3 carbohydrate chain GalNAcαl‐3(Fucαl‐2)Galα1‐3GalNAcαl‐3(Fucα1‐2)Galβl‐4Glcβl‐1 Ceramide, was suggested based on thin‐layer immunostaining and electron ionization mass Spectrometry. Ions corresponding lo a structure containing two deoxyhexoses, two hexosamines and three hexoses were identified, but no information was obtained from mass spectrometry concerning the carbohydrate sequence5. In the present paper, we report the identification of carbohydrate sequence ions corresponding to a type‐3 chain A heptaglyco‐sylceramide by electron ionization‐tandem mass spectrometry of a permethylated‐reduced glycosphingolipid mixture isolated from human kidney vein tissue. The use of a microchannel‐plate‐array detector increased the sensitivity for collision‐induced dissociation spectra by a factor of at least ten over a conventional electron multiplier.
Laser mass spectrometry of oligonucleotides with isomer matrices
Authors: Tang K. , Allman S. L. , Jones R. B. , Chen C. H. , Araghi S.
Published: May 2005

Various isomer matrices were used for laser‐desorption ionization of mixtures of oligomers. It was found that the efficiency of production of oligomer ions changed drastically when different isomers were used as matrices. For selected matrix materials, parent oligomer ions with sizes up to 64 bases were observed.
Spontaneous desorption: Dependence of the desorption rate on the grid parameters
Authors: Schoppmann Ch. , Voit H.
Published: May 2005

The desorption rate for ‘spontaneous desorption’ (SD) has been investigated using various grids with different geometrical dimensions (line width, line distance). The experimental results can be understood if one assumes that the keV ions which sputter ions from the sample in an SD process originate exclusively at the grid via field‐enhanced desorption of adsorbates (FEDA). This means that SD is a two‐step process. The first step is FEDA, the second step is a sputter process.
The loss of amine from electron ionized large‐ring cycloalkylamines
Authors: Lefèvre Odile , Mollova Névéna , Longevialle Pierre
Published: May 2005

Large‐ring ionized cycloalkylamines of low internal energy lose ammonia and homologous alkyl radicals competitively. It is shown by deuterium‐labelling experiments, that ammonia is lost mainly after ring‐contraction of the original parent ion to an alkyl‐monosubstituted cyclohexylamine isomer. This fragmentation is preceded by abundant hydrogen exchanges occurring mainly in this rearranged structure, but also, for the largest ring compounds, to some extent in the original structure.
Characterization of the oxidation products of paralytic shellfish poisoning toxins by liquid chromatography/mass spectrometry
Authors: Quilliam Michael A. , Janeček Mojmir , Lawrence James F.
Published: May 2005

Periodate oxidation of the toxins responsible for paralytic shellfish poisoning (PSP) yields fluorescent products that are useful for trace analysis by reversed‐phase liquid chromatography. Some toxins are oxidized to the same product, while others are transformed to a mixture of products; in ail cases, the products are too unstable to be isolated preparatively. A mobile phase containing heptafluorobutyric acid as an ion‐pair agent was developed to improve compatibility with liquid chromatography/mass spectrometry (LC/MS) analysis. Several LC/MS techniques were investigated: chemical ionization with the moving belt interface, atmospheric‐pressure chemical ionization, thermospray, continuous‐flow fast‐atom bombardment, and ion‐spray. Only LC/ion‐spray MS was able to provide spectra of the oxidized products. The products were characterized as purines resulting from: (a) breakage of the C4–C12 bond and aromatization of the remaining rings (loss of 4 hydrogens); (b) partial elimination of a carbamoyl or N‐sulfocarbamoyl side‐chain (this is promoted by the presence of an N‐1‐hydroxy group); and (c) partial hydrolysis of an N‐suifocarbamoyl side‐chain to a carbamoyl group.
Analysis of the squalestatins by on‐line packed capillary liquid chromatography/dynamic liquid secondary‐ion/mass spectrometry
Authors: Lane S. J. , Brinded K. A. , Taylor N. L.
Published: May 2005

A mixture of four squalestatins was separated and characterized by gradient‐packed capillary liquid chroma‐tography combined with dynamic liquid secondary‐ion mass spectrometry (LSIMS). Thioglycerol/glycerol matrix was added post‐column. Negative‐ion LSIMS was found to afford spectra typified by strong molecular ions with structurally informative fragments. The new method showed improvements in sensitivity and specificity for this class of compound when compared to existing thermospray methods.
Enhanced efficiency of surface‐induced dissociation of slow molecular ions at grazing incidence
Authors: Schmidt Lothar , Fritsch Hans‐Walter , Jungcfas Hartmut
Published: May 2005

Ions of m/z > 104 colliding with a solid surface at kinetic energies of 10–30 keV induce sputtering of secondary ions rather than emission of secondary electrons. Impact energies of 1 keV or lower lead to surface‐induced dissociation (SID) resulting in the release of specific fragment ions and this could also be employed for the detection of large ions in mass spectrometry. The present study using plasma‐desorption time‐of‐flight mass spectrometry gives evidence that the secondary ion yield of tlte SID‐process is maximal at grazing incidence. For impact energies ranging from 0,66 to 1.4 keV the SID efficiency is nearly constant and can be higher for large than for small organic ions colliding with a flat surface at grazing incidence angles.
The mass spectrometry service centre at Swansea: A small jewel in the crown of the science and engineering research council
Authors: Ballantine J. A.
Published: May 2005

The National Centre, set up by the Science and Engineering Reasearch Council in 1985, currently services the specialist mass spectrometry requirements of over 140 chemistry research teams, covering most of the British universities and carrying out about 9500 analyses each year, using mainly soft‐ionization techniques. Its work has featured in 1276 publilcatons during the past three years and the Centre has become invaluable to the progress of many research teams in Britain.
Contributions of fast‐atom bombardment mass spectrometry to studies of cyclic nucleotide biochemistry
Authors: Newton Russell P.
Published: May 2005

Cyclic nucleotides are biochemical second messengers which mediate the actions of many hormones and neurotransmitters. Fast‐atom bombardment (FAB) mass spectrometry and mass‐analysed ion kinetic energy (MIKE) spectra have provided a means of unambiguous identification of these compounds, and in addition to identifying endogenous putative cyclic nueleotides and their synthetic analogues FAB/MIKE analysis has now been applied to good effect to both qualitative and quantitative studies of cyclic nuclcotide‐related enzymes. Here the application of this mass spectrometric technique to cyclic nucleotides is described and its impact upon this field reviewed.
A radial‐field mass spectrometer with ‘T‐2’ deflection voltage
Authors: Akram A. G. , Miles H. T.
Published: May 2005

Mass analysis of ions emanating from a laser‐produced plasma requires some means of overcoming their wide energy spread, such as, for example, through the use of an ion reflector in time‐of‐flight spectrometers. An alternative approach to this problem is to allow the ions to move freely from the plasma into a spectrometer in which a radial deflection field varies in time in such a way that the deflection trajectory of an ion is independent of its energy. This paper describes the theory of such a spectrometer and investigates the focusing properties of the system. It is found that the required time‐varying field does not destroy the focusing features known for a radial field system except that under these new conditions first‐order focusing occurs at a turning angle of 144°, which contrasts with a focusing angle of 127° for a radial‐field spectrometer operating with a constant deflection field. The ion trajectories for the time‐varying field have been sutdied using numerical methods and results from these are presented. An approximate theory is also included which is in excellent agreement with the numerical computations and which yields simple results for use in spectrometer design.
State compositional analysis of diatomic cation beams using charge‐inversion spectrometry
Authors: Reid C. J.
Published: May 2005

The utility of charge‐inversion Spectrometry in the state analysis of diatomic cation beams is demonstrated by a brief summary and by reference to novel work on beams of NO+, SH+, CS+ and CI. A previously unknown state, of 3.5 eV relative energy and presumably of 4Σ+ symmetry was observed to be populated in a beam of CS+ ions formed from CS2. Evidence for the longevity ( > 10−5s) of the Ã2II state of CS+ and the b̃3II state of NO+ is also presented.
Double‐charge‐transfer spectroscopy using a modified Finnigan 8230 spectrometer
Authors: Andrews S. R. , Harris F. M.
Published: May 2005

A Finnigan 8230 mass spectrometer has been converted to a translational‐energy‐loss spectrometer suitable for double‐charge‐transfer (DCT) spectroscopy. Its performance was investigated by obtaining DCT spectra when 3keV OH+ projectile ions interacted with xenon atoms and ethene molecules. Well‐separated peaks were obtained which correspond to the populating of dicationic electronic states differing in energy by about 1 eV.
Simultaneous detection of ions and neutrals produced by matrix‐assisted laser desorption
Authors: Mowry Curtis D. , Johnston Murray V.
Published: May 2005

Ionic and neutral products of matrix‐assisted laser desorption were simultaneously detected in a time‐of‐flight mass spectrometer. The neutrals were photoionized with coherent vacuum ultraviolet radiation. Mass spectra were obtained for primary and secondary alkyl amines in various absorbing matrices. Based upon relative signal intensities of directly formed analyte ions and photoionized analyte neutrals, the ratio of neutrals‐to‐ions ejected was found to be of the order of 10000 or greater with desorption irradiances near the threshold for ion formation. The ratio decreased with increasing irradiance of the desorption laser beam. This dependence is consistent with a collisional mechanism tor analyte‐ion formation during the desorption event that is initiated by photoionization of the matrix. Matrices which gave large signal intensities of directly formed analyte ions also gave large signal intensities of photoionized analyte neutrals. Conversely, matrices which gave small signal intensities of directly formed arelyte ions also gave small signal intensities of photoionized analyte neutrals. These results suggest that the efficiency of analyte vaporization by matrix‐assisted laser desorption is an intrinsic property of the matrix‐analyte pair, independent of the ion‐formation process.
The potential of pyrolysis—(methylation)/gas chromatography/mass spectrometry in the analysis of wine polyphenolics
Authors: Galletti Guido C. , Antonelli Andrea
Published: May 2005

The phenolic compounds of a red Italian wine were separated by column chromatography into three fractions: (a) monomers, (b) red polymers and (c) yellow and brown polymers (tannins). Polymers were subjected to pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) using a heated‐filament pyrolyzer coupled to a capillary gas chromatograph and an ion‐trap‐detector mass spectrometer. Samples were pyrolysed as such or mixed with an aqueous solution of tetramethylammonium hydroxide in order to perform a simultaneous pyrolysis‐methylation (SPM). Pyrograms showing diagnostic markers for flavonoids and phenolic acids are reported. Advantages and limitations of both PY/GC/MS and SPM/GC/MS are discussed.
Optimization of a commercial liquid chromatography/mass spectrometry interface by statistical experimental design
Authors: Huang S. K. , Glancy S. B. , Stansbury W. F.
Published: May 2005

The efficiency of delivering 4‐methoxy phenyl acetic acid particle beam emerging from a commercial liquid chromatography/mass spectrometry interface into the ion source of the mass spectrometer was optimized using response surface modeling (RSM) of the statistical experimental design. It was found that the temperature and pressure of the nebulizer, and the temperature of the desolvation chamber are the major factors for the optimization.
Fast‐atom bombardment mass spectrometric analysis of cyclic nucleotide and nucleotide triphosphate analogues used in studies of cyclic nucleotide‐related enzymes
Authors: Langridge James I. , Evans Andrea M. , Walton Terence J. , Harris Frank M. , Brenton A. Gareth , Newton Russell P.
Published: May 2005

Two isomers of adenosine 3′,5′‐cyclic monophosphate, which show agonist and antagonist activity with cyclic AMP‐dependent protein kinase, were found to yield essentially identical positive‐ion fast‐atom bombardment (FAB) mass spectra, but S1 and S2 fragments of differing relative intensities in their collision‐induced dissociations, studied using mass‐analysed ion kinetic energy (CID/MIKE) spectra. Halogen‐substituted cyclic nucleotides, used in differentiating between protein kinase cyclic nucleotide binding sites, produced FAB mass spectra and CID/MIKE spectra with fragmentations generally analogous to those of the parent cyclic nucleotides; the bromo‐derivatives showed a greater propensity for dehalogenation than the chloro‐derivatives. The adenosine triphosphate analogues, adenylyl‐(β,γ‐methylene)‐diphosphate and adenylyl‐imidodiphosphate, alternative substrates for adenylyl cyclase, showed similar fragmentations with the methylene and imido groups blocking cleavage between the β and γ phosphate groups. The fragmentations observed are discussed in the context of the use of these compounds in the assay of protein kinase and adenylyl cyclase activity by quantitative mass spectrometry.
Collision‐induced dissociation and charge‐reversal processes of isomeric C6H4X− (X = F, Cl and Br) anions
Authors: Tomperi Päivi H. , Matimba Henri E. K , Ingemann Steen , Nibbering Nico M. M.
Published: May 2005

The NH ion reacts with fluoro‐ and chlorobenzene in the cell of a Fourier‐transform ion cyclotron resonance instrument only by proton abstraction, whereas the reaction with bromobenzene also yields Br− ions. The deprotonation of these halogen‐substituted benzenes occurs the 2‐, 3‐ or 4‐positions as revealed by deuterium labelling in combination with high kinetic energy (8keV) collision‐induced dissociation (CID) experiments performed with a double‐focusing quadrupole hybrid mass spectrometer. The 2‐fluoro‐ and 3‐ fluorophenyl anions eliminate HF following collision with an oxygen molecule. By contrast, the collisions between 4‐fluorophenyl anions and O2 do not yield detectable amounts of negatively charged fragment ions owing to the exclusive occurrence of electrom detachment. Electron detachment is also the only process observed in the 8 keV CID experiments with chlorophenyl anions and 3‐ and 4‐bromophenyl anions, whereas the ion formed by proton abstraction from the 2‐position in bromobenzene dissociates to Br− and 1,2‐dehydrobenzene. The 8 keV collision‐induced charge‐reversal spectra of the anions formed by proton abstraction from the 2‐, 3‐ or 4‐positions in a given halogen‐substituted benzene are virtually identical, indicating that this method does not provide insight into the position of the charge with respect to the halogen atom in the substituted phenyl anions.
Verification of the position of the phosphate group in some synthetic phosphopeptides by fast‐atom bombardment and tandem mass spectrometry
Authors: Nijenhuis A. A. , Fokkens R. H. , Nibbering N. M. M. , van Oijen A. H. , de Bont H. B. A. , Liskamp R. M. J. , van Boom J. H.
Published: May 2005

Some synthetically obtained linear and cyclic phosphopeptides of low molecular weight have been studied by fast‐atom bombardment and tandem mass spectrometry to verify the position of the phosphate group in these compounds. Based upon the occurrence/non‐occurrence of loss of phosphoric acid from low abundance fragment ions induced by low‐ and high‐energy collisions with target gases, it is shown that the position of the phosphate group in the phosphopeptides studied can be determined unequivocally.
Double‐electron transfer from Xe to Xe4+ at low energies as observed in the trap of a fourier‐transform ion cyclotron resonance mass spectrometer
Authors: von Köding Holger , Pinkse Frans A. , Nibbering Nico M. M.
Published: May 2005

Multiply charged Xen+ ions with n⩽5 were generated by electron impact on xenon gas in the external ion source of a Fourier‐transform ion cyclotron resonance (FT‐ICR) mass spectrometer. These ions were transferred to and trapped in the low pressure FT‐ICR cell. Subsequently, xenon ions with a particular mass and charge state were selected by ejection of all other unwanted ions from the FT‐ICR cell and allowed to react with neutral xenon atoms. It was found that, in the interactions between Xe4+ ions and neutral xenon atoms, not only does a single electron transfer take place, but also a double electron transfer.
Award announcement
Authors: Cornides I.
Published: May 2005

The Curt Brunnée Research Award.
Mass spectrometry of some C6F13‐compounds and their C6H13‐analogs
Authors: Napoli M. , Krotz L. , Scipioni A. , Seraglia R. , Traldi P.
Published: May 2005

The 70 eV electron ionization mass spectrometric behaviour of some C6F13‐compounds has been studied in detail by means of mass‐analyzed ion kinetic energy spectroscopy and compared with that of the C6H13‐analogs. As a general trend, the incorporation of fluorine leads to a strengthening of the alkyl chain; in fact the extensive primary fragmentation processes related to the chain cleavages observed for hydrocarbon derivatives are strongly suppressed in the case of the corresponding fluorocarbons. Moreover, the interaction of fluorine with functional groups leads to unexpected decomposition processes. The CH2CF2 bond, often considered in condensed‐phase chemistry as a weak point in the molecule, never undergoes fragmentation.
Enthalpies of formation of the negative ions MnO, MnO and MnO as determined by the ion/molecule equilibrium method
Authors: Rudnyi E. B. , Kaibicheva E. A. , Sidorov L. N.
Published: May 2005

Admixture of potassium chromate to manganese oxide has allowed us to generate measurable concentrations of the negative ions MnO, MnO, and MnO in the vapours over manganese oxide at 1300–1500 K. Equilibrium constants with the participation of these ions have been measured and the enthalpies of formation {ΔfH(MnO, 0 K) = (−266±13)kJmol−1, δfH,(MnO, 0 K) = (−538±14) kJmol−1, δfH(MnO, 0 K) = (−669±17)kJ mol−1}, dissociation energies and the electron affinity (EA) of MnO2 {EA = 292kJ mol−1} have been estimated. The use of manganese‐containing negative ions to measure the activity of manganese oxides is discussed.
Radical molecular anions formed from organic molecules under negative‐ion fast‐atom bombardment conditions: An unexpected finding during studies on the metabolism of bis(2‐ethylhexyl) phthalate
Authors: Egestad Börje , Sjöberg Per
Published: May 2005

Urinary metabolites of bis(2‐ethylhexyl) phthalate were studied using fast‐atom bombardment mass spectrometry (FAB‐MS). It was found that the ß‐glucosides of mono(2‐ethyl‐5‐hydroxyhexyl) phthalate and mono(2‐ethyl‐5‐oxohexyl) phthalate gave radical molecular unions, M −·, under negative‐ion FAB conditions. This was also shown to occur for the methyl ester of mono(2‐ethylhexyl) phthalate ß‐glucuronide, an artefact formed during the work‐up procedure.
A new method of trapping ions produced by matrix‐assisted laser desorption lonization in a quadrupole ion trap
Authors: Doroshenko Vladimir M. , Cotter Robert J.
Published: May 2005

A novel method for trapping ions produced by matrix‐assisted laser desorption ionization (MALDI) using controlled gating of the trapping field is suggested. Because it does not use collisions with helium atoms for reducing ion kinetic energy, trapping can be accomplished at low pressures of the buffet gas. The method has been implemented on an ion‐trap detector, modified for MALDI experiments inside an ion trap with axial introduction of the sample probe. High mass resolution (1 part in 12 000) is reported.
Accurate mass determination of a high molecular weight protein using electrospray lonization with a magnetic sector instrument
Authors: Dobberstein P. , Schroeder E.
Published: May 2005

Accurate mass determination on the 13+ ion of myoglobin, MW 16951, has been performed with a magnetic sector mass spectrometer equipped with a newly designed electrospray ion source. At a mass resolution of 20000 a mass deviation of 1 ppm from the expected value has been achieved.
Application of electrospray ionization mass spectrometry with maximum‐entropy analysis to allelic ‘fingerprinting’ of major urinary proteins
Authors: Evershed Richard P. , Robertson Duncan H. L. , Beynon Robert J. , Green Brian N.
Published: May 2005

Mixtures of a specific group of proteins, the major urinary proteins (MUPs), believed to have a role in odorant binding, have been analysed by electrospray ionization mass spectrometry. The data obtained from conventional transformed electrospray data confirm that the molecular weights of the protein mixtures, deduced from published sequences, lie in the molecular weight range 18600 to 19 000 Da. Application of maximum‐entropy analysis to the raw electrospray data has confirmed a heterogeneity in MUP composition, consistent with allelic similarities (and differences) between the different mouse strains. This work demonstrates the use of maximum entropy in the assessment of protein content and in the subsequent resolution enhancement of naturally occurring protein mixtures containing components of closely similar molecular mass.
Surface chemical changes of mixed‐oxide films in Cl2 anodic production
Authors: Daolio Sergio , Facchin Bruno , Pagura Cesare , Battisti Achille De , Barbieri Andrea
Published: May 2005

The recent development of specific and sensitive surface techniques has prompted new studies of electrode properties, in particular of their catalytic activity. Many papers have reported the use of X‐ray photoelectron spectrometry, Rutherford backscattering spectrometry, secondary ion mass spectrometry etc. in the analysis of mixed‐oxide films, and interesting results concerning electrochromic and catalytic properties have been shown. The influence of the method of preparation has also been confirmed, together with the important role of microstructural composition. In previous studies, our group performed composition analyses and depth profiles of RuO2/TiO2 and IrO2/TiO2 mixed‐oxide coatings by secondary ion mass spectrometry (SIMS). Many positive‐and negative‐ion species are of particular interest in characterizing electrodes synthesized by different methods. This paper presents the results obtained by SIMS analysis of IrO2/RuO2/TiO2 films before and after their use in CI2 anodic production. Mass spectra obtained under different experimental conditions are reported and the aspects related to surface compositon modifications induced by Cl2 evolution on electrode films are discussed.
Mass spectral fragmentation patterns of some thieno[3,2‐b]‐ and thieno[2,3‐b]‐thiophene‐2‐carbonylchlorides and ‐2‐carbonylanilides
Authors: Karminski‐Zamola Grace , Cvetko Magda , Švob Vladimir
Published: May 2005

The electron impact mass spectra of some thieno[3,2‐b]‐ and thieno[2,3‐b]‐thiophene‐2‐carbonylchlorides and ‐2‐carbonylanilides are discussed. Dominant peaks in the anilides are formed by cleavage of the C‐N amide bond and these ions fragment further by cleavage of CO. The fragment ion C3HS⌝+˙ m/z 69 is characteristic of carbonylchlorides and also carbonylanilides.
Correlation between the intensity of fragment ions in fast‐atom bombardment and the NMR chemical shift of hydrogen‐bonded hydroxyl protons of 6‐prenylfavonoids
Authors: Fukai Toshio , Nomura Taro
Published: May 2005

Correlation between the relative abundances of fragment ions from fast‐atom bombardment mass spectrometry and the chemical shifts of OH‐5 signals in 1H NMR 6‐prenylated flavonoids is discussed. The correlation may reflect the interaction between 6‐prenylated flavonoid and matrix.
Effects of target identity and collision energy on the fragmentation of some mass‐selected protonated neuropeptides
Authors: Curcuruto Ornella , Hamdan Mahmoud
Published: May 2005

A number of protonated neuropetides formed by 10 keV Cs+ ion bombardment are mass selected and their collision‐induced dissociations (CID) with helium, argon, xenon and isobutane are monitored using a collision energy of 200 eV. Data obtained by fixing the collision gas and using translational energies in the range 50–250 eV are also presented. The present data imply that optimzation of the CID spectra presented can be achieved through a judicious choice of both the target gas and the translational energy of the mass‐selected ion. The combined effect of the two experimental parameters on the relative abundances of the major sequence ions and on the loss of side‐chain moieties is discussed.
CF bond cleavage in collisionally activated dissociation of polyfluorinated molecular ions: Empirical structure‐upward‐shift correlation
Authors: Lee Young Jin , Kim Myung Soo
Published: May 2005

In an effort to understand the apparent upward shift in the translational energy of C6F· generated by collisionally activated dissociation (CAD) of the hexafiuorobenzene molecular ion, CADs of various molecular ions have been investigated. An interesting empirical correlation has emerged: namely, the loss of fluorine atoms directly attached to aromatic systems has displayed the upward shift. On the other hand, the F‐loss from polyfluorinated aliphatic molecular ions, either saturated or unsaturated, has shown the usual downward shift.
Peak profiles of ions originating from solid surfaces in time‐of‐flight mass spectrometers incorporating reflectrons
Authors: Loanoviciu D. , Cuna C. , Ardelean P.
Published: May 2005

Peak shapes were simulated in time‐of‐Hight mass spectrometers incorporating reflectrons, assuming short‐duration, constant ion‐production rates from plane surfaces. Calculations were performed for various initial velocity distributions: both Maxwell‐Boltzmann and exponential distributions for laser desorption, Gries distribution for secondary ions and Riggi‐Furstenau distribution for plasma‐desorption generated ions. The influence of an exponential decrease of the ion production rate on the peak shape was also illustrated in some cases.
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

Nine 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

A 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

The 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

The 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

A 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

The 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.