bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of active hydrogen in organic compounds by electron‐impact mass spectrometry
Authors: Dinya Zoltán , Lipták Miklós , Szabó Pál , Sztaricskai Ferenc , Vékey Karoly 
Published: May 2005

AbstractWe report here detailed studies of Bose et al.'s (J. Org. Chem. 47, 4008 (1982)) simple method for obtaining electron‐impact (EI) mass spectra from non‐volatile and/or thermolabile organic compounds by using ammonium salts. Good quality mass spectra can be obtained by mixing the analyte with different ammonium salts (mainly with NH4Cl) in a given ratio, the mixture being introduced through a conventonal direct probe. A wide variety of ammonium salts has been used to study the effect of the anion and to determine the optimum analyte:NH4X ratio and the other experimental parameters (i.e., electron energy, source temperature etc). A very simple and cheap means of determination of active hydrogen in hydroxyl, carboxyl, sulfhydryl, amino and amido etc groups by EI mass spectrometry using deuterated ammonium chloride (ND4CI) is described. The method is based on exchange of active hydrogen for deuterium occurring in situ in the ion source. This technique allows drect comparison of spectra before and after deuteration and the number of active hydrogens can be identified in most cases. The applicability of this method is demonstrated on different model compounds.
Relative affinities of alkylnitriles for the CoCl+ ion in the gas‐phase
Authors: Chen Lin‐Zhi , Miller Jack M. , Murthy Vemisetty S. 
Published: May 2005

AbstractThe relative CoCI+ ion affinities of six alkylnitriles have been estimated using Cooks' kinetic method in mass spectrometer using fast‐atom bombardm ent ionization. An approximate ordering for the relative affinities is given and discussed.
Electrospray mass spectrometry of Malayan pit viper (Calloselasma rhodostoma) venom
Authors: Sweetman G. M. A. , Garner G. V. , Gordon D. B. , Tetler L. , Theakston R. D. G. 
Published: May 2005

AbstractA high‐performance liquid chromatography protocol has been developed for the analysis of snake venoms. This system has been used to isolate eight fractions from Malayan pit viper (Calloselasma rhodostoma) venon. The fractions have been analysed using electrospray mass spectrometry. A number of major components were found with masses ranging from 13670 to 22750 Da.
The application of ‘MaxEnt’ to high resolution mass spectrometry
Authors: Ferroge A. G. , Seddon M. J. , Skilling J. , Ordsmith N. 
Published: May 2005

AbstractThe MaxEnt technique has premviously been successfully applied to the deconvolution of electrossppray mass spectra. The latest version of the Cambridge University software, ‘MemSys5’, has now been applied to high resolution mass spectra. Initial results have shown that peaks requiring an instrument resolution of almost 200 000 to separate them are readily resolved by MaxEnt on data acquired at a resolution of only 50, 000. Moreover, the MaxEnt results are accompanied by quantitative and realistic error bars.
A new reduction process in fast‐atom bombardment mass spectrometry: Substitution of a nitro group by a hydrogen
Authors: Aubagnac J.‐L. , Gilles I. , Astier R. , Gosselin G. , Imbach J. L. , Bergogne M. C. 
Published: May 2005

AbstractA new example of the resuction phenomenon often observed in fast‐atom bombardment mass spectrometry is described, involving the substitution of a nitro function by a hydrogen atom. This reaction, clearly visible with glycerol as metrix, takes place to only a very limited extent with m‐nitrobenzylalcohol.
Three‐dimensional deconvolution of multiply charged spectra
Authors: Labowsky Michael , Whitehouse Crag , Fenn John B. 
Published: May 2005

AbstractA three‐dimensional surface of signal vs molecular weight and adduct ion mass (H+, Na+, NH+ 3, etc) is introduced as an analysis tool for determining the mass of higher‐molecular‐weight compounds from their representations as a series of multiply charged peaks in a mass spectrum produced by electrospray ionization. This three‐dimensional approach has distinct advantages over conventional two‐dimensional analysis techniques with regard to detecting errors in the mass scale calibration, assessing the confidence level of a deconvoluted molecular‐weight assignment and in analyzing complex multiply charged spectra of mixtures. Special techniques are introduced which allow analysis of multiply charged spectra; containing adduct ion mixtures. solvent molecules absorbed on the parent molecule and ‘peaks’ resulting from partial dissociation of the parent molecule.
ortho‐Rearrangements of o‐alkylphenoxide anions
Authors: Reeks Lachlan B. , Eichinger Peter C. H. , Bowie John H. 
Published: May 2005

AbstractThe collision‐induced mass spectra of the o‐methyl and o‐ethylphenoxide anions show loss of formaldehyde and acetaldehyde, respectively. These processes are rationalized in terms of a reversible rearrangement o‐RC6H4O− ⇌ [(C6H4)−OR] (R = alkyl).
Species‐selectivity effects in the production of electrospray ions
Authors: Hiraoka Kenzo , Murata Konosuke , Kudaka Ichiro 
Published: May 2005

AbstractPositive‐ and negative‐ion production from electrosprayed charged liquid droplets has been studied. For acidified solutions of arginine, Arg‐Arg‐Arg, Lys‐Lys, and (CH3)4NBr in methanol + water (80/20, v/v), the relative intensities of CH3OH2+ ions were found to decrease faster than those of other sample ions as the distance (d) between the capillary tip and the interface plate was increased. The radial distribution of ion intensities in the spray cone was also examined. While the CH3OH2+ ions and multiply charged ions had maximum intensities in the central region of the spray cone, NH4+ and singly charged oligopeptide ions were found to be distributed in its peripheral region. The observed species‐selectivity effects in the production of electrospray ions were interpreted in terms of the volatility of ions in the charged liquid droplets. The negative‐ion intensities of the oligopeptide Glu‐Glu were enhanced greatly when ammonia was added to the solution. An optimum ammonia concentration which gives the strongest negative‐ion signals was ∼10−4M.
Pyrolysis/gas chromatography/mass spectrometry and Fourier‐transform infrared spectroscopy of amber
Authors: Galletti Guido C. , Mazzeo Rocco 
Published: May 2005

AbstractAmber samples from archaeological objects belonging to the collection of the Museo Civico Archeologico of Bologna were analysed by pyrolysis/gas chromatography/(ion‐trap) mass spectrometry (PY/GC/MS) and Fourier‐transform infrared spectroscopy (FTIR) to assess the geographic origin of the fossil resin. Both techniques showed potential in the study of amber, because they require small sample amounts, virtually no sample preparation and provide a fingerprint which is highly diagnostic of the material under investigation. Typical pyrograms, mass spectra and FTIR spectra are shown and compared to those obtained from standard amber of known geographical origin. The usefulness of composite mass spectra, namely mass spectra obtained by summing all or part of the mass spectra acquired within the pyrogram, to create a library of PY/GC/MS data and to compare samples is evaluated.
Pyrolysis/gas chromatography/ion‐trap mass spectrometry of the ‘tooth brush’ tree (Salvadora persica L.)
Authors: Galletti Guido C. , Chiavari Giuseppe , Kahie Yassin Duale 
Published: May 2005

AbstractChemical characterization of ‘tooth brush’ tree (Salvadora persica L.) sticks was carried out using a pyrolysis/ gas chromatograph coupled to an ion‐trap detector mass spectrometer. Electron impact and chemical ionization mass spectra, along with chromatographic profiles obtained by both flame ionization and nitrogen/phosphorous detectors, enabled the structure of some eighty pyrolysis fragments to be proposed. These were mainly lignin and polysaccharide derivatives of phenolic and furanic natures, respectively. However, compared with the pyro‐grams of other well‐studied lignocellulosic materials, S. persica showed several unique nitrogen‐containing compounds, some of which were tentatively identified as pyrrolidine, pyrrole and piperidine derivatives on the basis of their mass spectra and chromatographic elution order.
Investigation of some steroids by means of thermospray and tandem mass spectrometry
Authors: Curcuruto O. , Franchi D. , Hamdan M. , Favretto D. , Traldi P. 
Published: May 2005

AbstractThe detection limits of a number of steroids have been determined by means of loop‐injection thermospray (TS) mass spectrometry. The measured limits were found to be in the range 1 pg‐1O ng/μL. Combined positive‐ion TS/tandem mass spectrometry yielded clear qualitative differences between mass selected protonatcd testosterone and estriol ions, both of which have the same nominal molecular weight. These differences are necessary for the correct identification of either species which may be present within a complex mixture. The heights of the peaks due to the two competing reaction channels, [M + H]+ and [M + NH4]+, were monitored as a function of the repeller voltage in the range 100‐350 V, and the implications of the acquired data are discussed.
Studies on the interaction of elfamycin antibiotics with elongation factor‐Tu by mass spectroscopic techniques
Authors: Sottani C. , Islam K. , Soffientini A. , Zerilli L. F. , Seraglia R. 
Published: May 2005

AbstractElfamycin antibiotics have been studied by mass spectrometry, using direct‐liquid‐introduction chemical ionization and fast‐atom bombardment (FAB), but these techniques are not suitable for the identification of the interaction product between antibiotic and elongation factor‐Tu (EF‐Tu). A new mass spectrometric technique, matrix‐assisted laser desorption (MALD), has been employed to clearly identify the complex formed between EF‐Tu and kirromycin. Using MALD operated in the positive‐ion mode, molecular weight values of 43 330 and 44 234 Da were obtained for EF‐Tu and the adduct EF‐Tu/kirromycin, respectively; both are close to the theoretically calculated values of 43 225 and 44 060. These measurements suggest that MALD techniques can be used to obtain useful information on EF‐Tu/elfamicyn antibiotic interaction. Other techniques, such as desorption chemical ionization, FAB and thermospray have been used to obtain information on the fragmen‐tation patterns of some elfamycins (kirrotmycin, aurodox, efrotomycin). In particular, the positive‐ion FAB spectrum of efrotomycin obtained by using a matrix of glycerol and water containing K+ ions, contained the quasimolecular ion [M + K]+ at m/z 1184. Thermospray appeared to be the best technique for structural elucidation studies. In fact, positive‐ion spectra of kirromycin, aurodix and efrotomycin are characterized by significant fragmentation ions, while molecular ions are of very low intensity.
Pyrolysis/gas chromatography/mass spectrometry in the analysis of asphaltenes
Authors: Nali M. , Corana F. , Montanari L. 
Published: May 2005

AbstractA study on the flash pyrolysis of asphaltenes using gas chromatography/mass spectrometry is reported. Six n‐heptane‐precipitated asphaltene samples, characterized by elemental analysis and nuclear magnetic resonance (NMR), were selected because of their different compositions. By considering the main pyrolysis products some structural parameters were worked out. The results obtained from the pyrolysis data were compared to those deriving from elemental analysis and NMR. In spite of the severe thermal treatment (650°C for 20 s) undergone by the asphaltenes, the pyrolysis products qualitatively reflect structural differences shown in the original samples by NMR (a non‐destructive technique).
Analysis of microcystins from cyanobacteria by liquid chromatography with mass spectrometry using atmospheric‐pressure ionization
Authors: Edwards Christine , Lawton Linda A. , Beattie Kenneth A. , Codd Geoffrey A. , Pleasance Stephen , Dear Gordon J. 
Published: May 2005

AbstractA combined liquid chromatographic mass spectrometric method was developed for the analysis of microcystins (hepatotoxic cyclic heptapeptides) produced by cyanobacteria (blue‐green algae). The method was used to confirm the identity of microcystins, tentatively identified by high‐performance liquid chromatography using diode‐array detection, in extracts from natural‐bloom material and a sample of river water where hepatotoxic cyanobacteria were present. The potential of tandem mass spectrometry for obtaining structural information and providing a selective screen for these compounds was also investigated.
Gas‐phase reactivity of ambident thio‐enolate and oximate anions
Authors: Freriks Ivo L. , de Koning Leo J. , Nibbering Nico M. M. 
Published: May 2005

AbstractThe gas‐phase chemical behaviour of ambident thio‐enolate anions from thioacetaldehyde and oximate anions from acetaldoxime and acetone oxime has been studied using the method of Fourier‐transform ion cyclotron resonance mass spectrometry. It appears that the thio‐enolate anions, generated by an efficient base‐induced E2 elimination of ethene from ethyl vinyl sulfide, exhibit a strong preference for addition via the sulfur rather than via the carbon nucleophilic center in the reactions with a series of unsaturated polyfluorocarbon compounds. This preferred addition via the sulfur nubleophilic center is considered to be promoted both by specific frontier orbital and by electgrostatic interactions between the reactants. Further, acetaldoxime and acetone oximate anions exclusively react via the oxygen nucleophilic center with the series of unsaturated polyfluorocarbon compounds. Electrostatic interactions are held responsible for the reaction selectivity of the oximate anions. This is in contrast with the corresponding enolate anions, for which it is considered that the previously studied ambident chemical behaviour is governed by specific frontier orbital interactions.
Gas‐phase chemistry of metal carbonyl anions: Reactions of Fe(CO) with methanol and its 13C‐, D‐ and 18O‐labelled analogues studied by fourier‐transform ion cyclotron resonance mass spectrometry
Authors: van den Berg K. J. , Ingemann S. , Nibbering N. M. M. , Gregor I. K. 
Published: May 2005

AbstractThe reactions of the metal dicarbonyl anion Fe(CO) with methanol and five of its isotopomers, namely CD3OH, CH3OD, CD3OH and CH318OH have been studied by the use of Fourier‐transform ion cyclotron resonance mass spectrometry. Three competitive reaction channels have been identified in these trapped‐ion/molecule studies which, for methanol, lead to the formation of three primary reaction products, namely [HFe(CO)(OCH)3]− formed in a decarbonylation channel; Fe(CO) in a channel involving CH and OH bond activations and bis‐dehydrogenation of a collision complex; and also [(CH2O)Fe(CO)2]− in a separate channel involving the elimination of a single H2 molecule. The primary product ion [HFe(CO)(OCH)3]− further reacts with methanol to give a bis‐alkoxy substituted metal carbonyl ion [(CH3O)2Fe(CO)]− at trapping times of several seconds. Complex deuterium isotope effects of an interactive nature with respect to the three reaction channels also have been observed.
Enhancement of resolution in matrix‐assisted laser desorption using an ion‐trap storage/reflectron time‐of‐flight mass spectrometer
Authors: Chien Benjamin M. , Michael Steven M. , Lubman David M. 
Published: May 2005

AbstractA quadrupole ion‐trap storage/reflectron time‐of‐flight mass spectrometer (IT/RETOFMS) has been used to enhance resolution in the ultraviolet matrix‐assisted laser desorption/ionization (MALDI) of peptides. The MALDI of peptides is performed directly inside an ion‐trap storage device using 266 nm laser radiation from a 2,5‐dihydroxybenzoic acid matrix. Helium buffer gas is used to collisionally cool the hot desorbed ions and to rapidly relax the ions to the center of the ion trap. The result is that upon ejection into the TOF device, a resolution of nearly 6200 is obtained‐for Substance P using a 90 ms storage time. A resolution of 3000–6000 is consistently obtained for peptides up to 2100 u used in this study. The individual ion peaks from the isotopic distribution are easily resolved under these conditions. In addition, the ion trap is found to be useful as an ion‐storage device for enhancing the signal where multiple laser desorption pulses can be stored per cycle in the trap before ejection into the RETOF. Also, using the relatively high resolving power of the IT/RETOF instrument, excellent mass accuracy can be obtained using the matrix background and bradykinin as internal standards.
The analysis of mock DNA sequencing reactions using matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Fitzgerald Michael C. , Zhu Lin , Smith Lloyd M. 
Published: May 2005

AbstractA mock sequencing experiment is described in which matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry is used to analyze mixtures of synthetic oligodeoxynucleotides chosen to match the first 24 DNA fragments generated in typical sequencing reactions using a standard M13mp19 template and primer. The experiments permitted the evaluation of important issues relating to resolution, sensitivity, multiple charging, and adduct formation. Mass resolutions (full width at half maximum) were between 100 and 200, and it was relatively straightforward to assign bases in the sequencing simulation using subpicomolar quantities of material. These results demonstrate the potential of MALDI mass spectrometry in DNA sequence analysis.
Quantitative applications of matrix‐assisted laser desorption/ionization with time‐of‐flight mass spectrometry: Determination of copolymer composition in bacterial copolyesters
Authors: Abate R. , Ballistreri A. , Montaudo G. , Garozzo D. , Impallomeni G. , Critchley G. , Tanaka K. 
Published: May 2005

AbstractPoly(β‐hydroxybutyrate‐co‐β‐hydroxyvalerate) of microbial origin has been analyzed by matrix‐assisted laser desorption/ionization (MALDI) in a time‐of‐flight mass spectrometer, after partial methanolysis, using two different instruments, Our results show that the mass spectral intensities recorded in the MALDI mode correlate with previously reported fast‐atom bombardment and direct chemical ionization data. MALDI compares favourably with these other two techniques in that it is more suitable to the analysis of complex mixtures and of higher molecular masses.
Automated routine thermospray mass spectrometry in the analysis of potential drug compounds
Authors: Tiller Philip R. , Lane Stephen J. 
Published: May 2005

AbstractA System to automate the analysis of routine mass spectrometry samples, using either a thermospray or particle‐beam interface, has been developed. This has allowed unattended operation and has freed expert mass spectrometrists to address ‘real’ problems. The system also acts as a filter to the problem‐solving service.
Complete third‐order resolution formulae for time‐of‐flight mass spectrometers incorporating reflectrons
Authors: Ioanoviciu D. 
Published: May 2005

AbstractThe resolution of single‐ and double‐stage, homogeneous electric mirror time‐of‐flight mass spectrometers can be calculated with the derived formulae for detectors located normally to the ion flight direction or parallel to the mirror face. These formulae account for contributions to the peak width from ion initial velocity and position in the source (‘turn around’ time included), from ion‐packet longitudinal and transverse size at the source final grid, as well as due to the angular ion spread. Third‐order terms are included for beam size, angular aperture and velocity spread, the incidence angle being small. The field‐free space needed to obtain energy focusing in time is connected with the length of the accelerating space inside the source.
Photofragmentation in Fourier‐transform ion cyclotron resonance: Use or misuse?
Authors: Gäumann Tino , Zhao Guohong , Zhu Zhiqing 
Published: May 2005

AbstractThe noise in a sector or quadrupele mass spectrometer is determined by the source, i.e. the number of ions present in the signal, whereas in Fourier‐transform ion cyclotron resonance it is detector limited. In addition, the Fourier transform spreads white noise equally over the whole spectrum. Thus the accuracy for broad‐band spectra is generally rather low. However, the precision, i.e. the reproducibility of successive spectra, is astonishingly high. This fact has been used with much success, for example in collisionally activated dissociation in Hadamard spectra. It is shown that photofragmentation spectra are also very reproducible and thus allow—at least in principle—a ‘kinetic deconvolution’ of a series of such spectra. In such a case, nonlinear regression has to be applied to the data. Since in most kinetics problems several exponential functions are involved, and since it is well known that these exponential functions are notoriously difficult to approximate with a Marquardt‐Levenberg algorithm, the validity of the results may be questionable. Three examples (protonated benzene, cycloheptatriene, deuterated toluene) are chosen to demonstrate some of the difficulties and pitfalls of the procedure.
Mass measurement accuracy of matrix‐assisted laser desorbed biomolecules: A Fourier‐transform ion cyclotron resonance mass spectrometry study
Authors: Solouki Touradj , Gillig Kent J. , Russell David H. 
Published: May 2005

AbstractThe use of binary matrices and internal calibrants to improve the mass measurement accuracy in matrix‐assisted laser desorption ionization (MALDI) with Fourier‐transform ion cyclotron resonance (FTICR) mass spectro‐metry is described. Binary matrices enhance the analyte ion yield and enable a complete MALDI‐FTICR mass spectrum to be obtained from a single laser shot. The advantage of single‐laser‐shot data acquisition is that it eliminates line‐broadening due to shot‐to‐shot frequency variations. It is shown that unresolved product ions, mainly due to loss of H2O and/or NH3, shift the centroid of an unresolved multi‐component peak. A mass measurement accuracy of 12 ppm was obtained for the bovine insulin [M+H]+ ion using melittin as an internal calibrant.
Recognition of quaternary ammonium compounds using mass spectrometry
Authors: Fisher Dixie L. , Arthur Moseley M. , Mullis James O. , Norwood Daniel L. , Baillie Thomas A. 
Published: May 2005

AbstractLiquid secondary‐ion mass spectrometry (LSIMS) experiments were performed on a series of model quaternary ammonium chlorides [MCl−] in order to develop a strategy, via an understanding of cluster‐ion formation, for recognition of quarternary ammonium structures. Model structures contained a single quaternary site and various other structural features (for example, conjugated quaternary systems and carboxylic acid groups), using amine hydrochlorides as controls. Cluster ions were examined with both positive‐ and negative‐ion LSIMS, using a range of matrix modifiers. Precursor scans, or ‘molecular weight confirmation scans’, of M (the charged molecular ion of quaternary ammonium compounds) and [M+H]+ ions were used to assist in the observation of cluster ions and to unambiguously demonstrate precursor/product relationships. Positive‐ion experiments typically showed dimeric clusters of [2MQ+ A]+ (A=anion) and [2MQ−H]+ ions, while negative ion experiments produced [MQ + 2A]− ions. Observation of these cluster ions coupled with the lack of an [M−H]− ion are a distinguishing feature of quaternary amines. Additional cluster ions were targeted for distinguishing between protonated amines and quaternary amonium compounds containing a carboxylic acid group. A strategy for recognizing and distinguishing quaternary ammonium structures using LSIMS is proposed, and some initial experiments with thermospray and electrospray are discussed.