bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid chromatography/mass spectrometry analyses of small molecules using electrospray and fast‐atom bombardment ionization
Authors: Reiser Robert W. , Fogiel Arthur J. 
Published: May 2005

AbstractElectrospray ionization and fast‐atom bombardment (FAB) are both soft ionization techniques which typically give prominent molecular ions of thermally labile and highly polar molecules. These two complementary techniques were compared on the same magnetic sector mass spectrometer, a Finnigan MAT 900. Comparisons were made of sensitivity, versatility, ease of use, and most importantly for our work, structure elucidation of unknowns arising from research with agricultural chemicals. Both known standards and ‘real world’ unknowns were analyzed by liquid chromatography/mass spectrometry (LC/MS) with both interfaces. The same reversed‐phase micro‐LC system was used with both ionization techniques, using 0.32 mm i.d. packed capillary LC columns at flow rates of 1–2 μL/min. Improved performance in the continuous‐flow FAB mode was obtained by use of a screen target. The advantages, disadvantages and similarities of these two ionization techniques are discussed.
Application of thermally assisted electrospray ionization mass spectrometry for detection of noncovalent complexes of bovine serum albumin with growth hormone releasing factor and other biologically active peptides
Authors: Baczynskyj Lubomyr , Bronson George E. , Kubiak Teresa M. 
Published: May 2005

AbstractIon‐spray ionization mass spectrometry with gentle conditions for solvent removal has been reported as a useful tool for detection of high‐affinity noncovalent complexes of biological relevance formed in solution. Two main objectives of this study were (i) to find whether other types of electrospray ionization (ESI) sources, e.g. where the solvent is removed with the help of heat (thermally assisted electrospray), could be utilized for detection of noncovalent biological complexes of high and low affinity and (ii) to find whether ESI‐MS can be used for detection of the association of bovine serum albumin (BSA) with biologically active peptides. Using a well‐defined high‐affinity association of FK506 with its binding protein (FKBP) as model system we proved that ESI‐MS with thermally assisted interphase can be used for detection of the FK506‐FKBP complexes in a similar way as was previously shown for electrospray mass spectrometry (Ganem et al., J. Am. Chem. Soc. 113, 6294 (1991)). In mixtures of BSA with a 9–10 molar excess of biologically active peptides, such as growth hormone releasing factor (GRF), glucagon, bradykinin or insulin in ammonium acetate at pH 7.5, complexes with a ratio of 1:1, 1:2 and in some cases 1:3 were detected. On the other hand, these complexes disappeared upon acidification, pointing to their noncovalent nature. To our knowledge, this is the first evidence that relatively weak and nonselective association of proteins (represented here by BSA) with peptide ligands have been detected by ESI‐MS in addition to well documented examples of highly specific molecular recognition phenomena like, for example, those reported for receptor‐ligand, enzyme‐substrate, or enzyme‐inhibitor systems. Our results also show that electrospray ion sources of different design are amenable for performing studies of binding.
Electron ionization and fast‐atom bombardment mass spectrometry of some new macrocycles containing triethanolamine derivatives and 1,3,5‐triazine moieties
Authors: Corda Luciana , Delogu Giovanna , Maccioni Elias , Podda Gianni , Seraglia Roberta , Traldi Pietro 
Published: May 2005

AbstractThe behaviour of four open‐chain analogues of crown ethers (polypodands) have been studied under both electron ionization and fast‐atom bombardment conditions with the aid of mass‐analyzed ion kinetic energy spectroscopy and accurate mass measurements. In electron ionization, extensive fragmentations, closely related to the original structures, are observed, while fast‐atom bombardment, leading to the formation of abundant protonated molecules, allows easy establishment of the molecular weight. The presence of odd‐electron cations in distonic form and the occurrence of cyclization reactions are discussed.
Conformation dependence in the chemical ionization mass spectra of 3‐pinanones
Authors: Joseph Youssefi M. , Boschung André F. , Thomas Alan F. , McLafferty F. W. 
Published: May 2005

AbstractThe conformation of the rigid isomer pair of cis‐ and trans‐3‐pinanones was investigated using methane, isobutane, and ammonia chemical ionization (CI) mass spectrometry as a tool to study the dependence of the mass spectrometric fragmentation patterns. The methane and the isobutane CI mass spectra of the cis and trans isomers were found to be different enough to permit the differentiation of the isomers. Each isomer exhibited distinctive fragmentation paths. The isobutane mass spectra of the cis isomer was dominated by the loss of H2O from the pseudo‐molecular ion, whereas the loss of C2H4O was the predominant fragment for the trans isomer. Molecular modeling and quantum‐chemical computations were used to calculate the conformers of lowest energy for the two isomers. The theoretical calculations were then used to explain the differences observed in the chemical ionization mass spectra.In addition, high resolution mass spectrometry measurements, deuterium labeling experiments and energy calculations of the hypothetical transition states and ionized species were helpful and were used to propose mechanisms for the CI mass spectral fragmentation.
Characterization of new diimines of carbon suboxide by tandem mass spectrometry
Authors: Flammang Robert , Laurent Sophie , Barbieux‐Flammang Monique , Van Haverbeke Yves , Wentrup Curt 
Published: May 2005

AbstractBis‐aryliminopropadiene radical‐cations, [ArNCCCNAr′]+·, have been generated by dissociative ionization of isoxazolopyrimidine precursors and structurally characterized by collisional activation mass spectrometry; the corresponding neutral cumulenes have also been produced in neutralization‐reionization experiments.
Characterization of hematology lysing reagents containing quaternary ammonium halides using fast‐atom bombardment mass spectrometry
Authors: Bambagiotti‐Alberti Massimo , Coran Silvia , Giannellini Valerio , Favretto Donata , Traldi Pietro 
Published: May 2005

AbstractPositive‐ and negative‐ion fast‐atom bombardment (FAB) mass spectrometry has been employed to characterize pure dodecyl‐, tetradecyl‐ and hexadecyl‐trimethylammonium chlorides and bromides, compounds of high interest as lysing agents in hematologic analyses. In parallel, the same approach has been used for some commercially available lysing reagent products. While in positive‐ion FAB mass spectra the presence of the abundant ions corresponding to the intact quaternary ammonium cations (Q+) is accompanied by the presence of [Q2X]+ (X = Cl, Br) species, in the negative‐ion mode cluster ions such as [QX2]− are the sole ionic species that are easily evident. The mechanism for the formation of [Q2X]+ and [QX2]− species has been studied and some suggested explanations are given.
Dehalogenation reactions in frit fast‐atom bombardment mass spectrometry of substituted hydroquinones
Authors: Claramunt R. M. , Escolastico C. , Sanz D. , Aubagnac J‐L. , Gilles I. 
Published: May 2005

AbstractThe reduction reaction consisting in the substitution of a chlorine by a hydrogen atom, already known in fast‐atom bombardment (FAB) mass spectrometry, has been established for the first time in Frit FAB mass spectrometry in the case of 2‐chloro‐1,4‐hydroquinone and 2,5‐dichloro‐1,4‐hydroquinone. Comparison of the spectra obtained with mobile phases containing either glycerol or meta‐nitrobenzyl alcohol has been performed for both compounds.
Application of ion mobility spectrometry to the identification of trace levels of explosives in the presence of complex matrices
Authors: Garofolo Fabio , Migliozzi Vincenzo , Roio Bernardo , Davies John H. 
Published: May 2005

AbstractMethods are described for the analysis of trace levels of explosives on materials collected at the scene of real detonations. The methods exploition mobility spectrometry (IMS) to confirm and enhance the results obtained by high performance liquid chromatography with an ultraviolet detector (HPLC‐UV). Solvent‐extracted samples contain many interfering substances and are cleaned up by solid‐phase extraction (SPE) prior to HPLC fractionation. Explosive‐containing HPLC fractions are analysed by IMS after removal of solvent by vacuum centrifuge. IMS detection limits for explosives, typically a few hundreds of picograms, are at least an order of magnitude lower than those for UV detection. SPE and HPLC fractionation also removes interfering substances that can otherwise suppress IMS detection. Explosives discussed are di‐ and trinitrotoluene, ethylene glycol dinitrate, nitroglycerin, pentaerythritol tetranitrate, hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine, octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetraazine, and N‐methyl‐N,2,4,6‐tetranitroaniline.
Electron ionization mass spectra of hydroxymethyltetrathiafulvalenes and bis(hydroxymethyl)tetrathiafulvalenes
Authors: Blanchard Philippe , Duguay Guy , Garin Javier , Orduna Jesús , Gorgues Alain , Sallé Marc 
Published: May 2005

AbstractThe mass spectra of hydroxymethyltetrathiafulvalenes and bis(hydroxymethyl)tetrathiafulvalenes have been studied by electron ionization, metastable analysis and accurate mass measurements. The elimination of water from molecular ions of bis(hydroxymethyl)tetrathiafulvalenes has been investigated with the aid of isotopic labelling and the structures of the ions thus formed have been established by collision‐induced dissociation studies.
Generation and characterization of dihydroxycarbene, HOCOH, by neutralization/reionization mass spectrometry
Authors: Wiedmann Fred A. , Cai Jinnan , Wesdemiotis Chrys 
Published: May 2005

AbstractDihydroxycarbene is produced in the gas phase by neutralization of the HOCOH+· radical cation which is formed by dissociative electron ionization of oxalic acid. Reionization ∼0.3 μs later shows that HOCOH can survive intact and, thus, exists as a stable species with appreciable barriers for dissociation or rearrangement to formic acid (HCOOH). Within the time scale of the experiment, a small fraction of the carbene decomposes to H2O + CO. comprison of the experimental results with ab initio theory shows that the dissociating HOCOH molecules are generated in the electronically excited triplet state, while the klarge amount of surviving carbene molecules is formed in the singlet ground state.
Characterization of coal by matrix‐assisted laser desorption ionization mass spectrometry. I. The argonne coal samples
Authors: Herod Alan A. , Li Chun‐Zhu , Parker John E. , John Phillip , Johnson Chris A. F. , Smith Gerry P. , Humphrey Paul , Chapman John R. , Kandiyoti Rafael , Games D. E. 
Published: May 2005

AbstractThe Argonne set of coals cover the rank range from lignite to semi‐anthracite; these samples have been studied by matrix‐assisted laser desorption mass spectrometry (MALDI‐MS) in a time‐of‐flight mass spectrometer equipped with a nitrogen laser at 337 nm, using sinapinic acid as matrix. The coal particle size was less than 5 microns. The characteristics of the MALDI‐MS spectra of the set of coals were found to be rank‐related; desorption from high‐rank coals was found to take place with greater relative ease than from low‐rank coals. Two major features were found in all spectra: a homologous series of peaks in the 200–500 u mass range and an intense peak between 1000 and 5000 u, the particular shape of the peak depending on coal rank. A continuum of lower intensity peaks extending to very large molecular masses was found in all spectra, the upper limit of molecular masses increasing with coal rank at the same laser fluence. The effect of changes in laser power on spectra was investigated: upper mass limits were found to increase with power up to the detection limit of the instrument but low‐mass parts of spectra were found to distort, possibly due to detector overloading. A maximum laser fluence value acceptable over the coal‐rank range represented by these samples could therefore not be easily defined. None of the mass spectra showed evidence of the presence of either carbon clusters or fullerene formation, indicating that laser fluences did not reach intensities high enough to induce substantial secondary reactions. Comparing molecular mass distributions detected by MALDI of coal pyrolysis tars and directly from coals suggests the MALDI and pyrolytic mechanisms of volatile release to be structurally different; in particular, the preferential evaporation of lighter species which occurs during pyrolytic tar evolution (and during field‐ionization mass spectroscopy) appears to evole material with a more restricted range of molecular masses compared to laser desorption mechanisms.
Substituent effects in the mass spectrometry of 4‐substituted camphors studied under electron and chemical ionization
Authors: Vainiotalo Pirjo , Kettunen Sari , Pihlaja Kalevi , Morris David G. 
Published: May 2005

AbstractThe electron ionization mass spectra of fourteen 4‐substituted (4‐X) camphors have been recorded and analyzed using metastable ion analysis and exact mass measurement. With respect to camphor, alkyl substituents changed the relative importance of different fragmentation pathways, though they did not induce new fragmentations. Substituents X connected to the camphor framework through an atom having a lone pair of electrons were generally lost as HX. Overall the fragmentation behaviour was essentially independent of the inductive substituent constant. Under chemical ionization conditions, only methane of the reagent gases produced extensive fragmentations of these compounds; isobutane, acetone and ammonia were ineffective. The nature of the fragmentations was independent of both the inductive substituent constant of the substituent X and the proton affinity and heat of formation of the corresponding neutral compound HX.
Influence of cooling time on the internal energy of ions subjected to resonance excitation in a quadrupole ion trap
Authors: Liere P. , Blasco T. , March R. E. , Tabet J.‐C. 
Published: May 2005

AbstractThis study demonstrates the influence of cooling time, applied prior to (and after) resonance excitation, on the internal energy carried by ions subjected to tickle excitation. Competitive fragmentations of ionized butylbenzene have been used to estimate the internal energy average transferred during collision processes. Two competitive effects have been observed by using a delay time before tickle: kinetic energy relaxation (up to 15 ms) related to an internal energy decrease effect and, at higher cooling time values, collisional excitation with helium buffer gas allows one to increase the internal energy of precursor ions.
Mass spectral fragmentation of some cycloalkane‐condensed 4,5‐dihydro‐3(2H)‐pyridazinones and 4,5‐dihydro‐6H‐1,2‐oxazin‐6‐ones
Authors: Mäki Esa , Stàjer Géza , Csende Ferenc , Vainiotalo Pirjo , Pihlaja Kalevi 
Published: May 2005

AbstractThe electron ionization mass spectra of 10 cycloalkane‐condensed 4,5‐dihydro‐3(2H)‐pyridazinones and four cycloalkane‐condensed 4,5‐dihydro‐6H‐1,2‐oxazin‐6‐ones were studied. The molecular ions of these compounds were very stable and in most cases formed the base peaks of the spectra. Otherwise the spectra of compounds having different fused cycloalkane rings deviated considerably from each other. The spectra of cis‐ and trans‐fused cyclohexane derivatives showed characteristic differences.
Study by mass spectrometry and gas chromatography of toluene oxidation in a low‐pressure plasma reactor
Authors: Langleron M. , Cavadias S. , Amouroux J. 
Published: May 2005

AbstractThe aim of the present work is to study the oxidation reactions between an aromatic hydrocarbon, toluene and oxygen. Experiments have been performed in a low‐pressure plasma tubular reactor supplied by an RF 13.56 MHz generator. On‐line mass spectrometry and off‐line gas chromatography were used for a qualitative and quantitative analysis of the effluents. The reaction can lead to the formation of products in the solid (deposited on the wall of the reactor), liquid or gas state. Hydrocarbons (benzene, ethylbenzene, diphenylethane), as well as oxygenated species resulting from competition between the oxidation of the aromatic ring (phenol, cresols) and the oxidation of the alkyl side chain (benzyl alcohol, benzaldehyde), can be obtained. The power and the amount of added oxygen were studied by comparing the mass spectrometry and gas chromatography results. Reaction mechanisms are discussed.
Mass spectrometric chemical balance of CF4 decomposition in a plasma reactor
Authors: Alayoubi S. , Khairallah Y. , Arefi F. , Amouroux J. , Gonnord M. F. 
Published: May 2005

AbstractThe decomposition of carbon tetrafluoride (CF4) in two types of plasma reactor has been investigated by using mass spectrometry. The optimization of the plasma process requires the establishment of an adequate chemical balance between major components and also traces in the reactor effluent, in order to minimize toxic emissions by control of the proper reactor parameters. On‐line mass spectrometric characterization of the effluent has been used to optimize the CF4 decomposition yield. A GC/MS protocol has been developed to quantify both major and minor components of the effluent in order to evaluate its toxicity.
The CID spectra of hydrated oxygen ions
Authors: Susič Robert , Kralj Bogdan , Žigon Dušan 
Published: May 2005

AbstractA steady production of positive hydrated oxygen molecular ions has been achieved by the introduction of H2O vapour into the ion source of a mass spectrometer under chemical ionization conditions using O2 reagent gas. Collision‐induced dissociation, mass‐analyzed ion kinetic energy (CID MIKE) spectra (R. G. Cooks, J. H. Beynon, R. M. Caprioli and G. R. Lester, Metastable Ions, Elsevier, Amsterdam, 1973) of the m/z=50 ions, which correspond to the H2O·O ions, show a prominent loss of a water molecule, but no significant hydrogen loss. By contrast, the CID MIKE spectra of the H2O ions obtained under identical conditions indicate an important successive loss of hydrogen and oxygen atoms, giving rise to an intense H2O+· peak. Conversely, with H2O·O, a relatively loosely‐bound adduct of the two stable moieties is indicated, a ‘cluster’ that fragments into its constituents with a preferential charge retention on the species of lower ionization energy.
State‐selective single‐electron capture by Ar4+ in He, Ne and Ar
Authors: Lee Anthony R. , Wilkins Adam C. R. , Brenton A. Gareth 
Published: May 2005

AbstractTranslational energy spectra have been obtained for single‐electron capture by 8 keV Ar4+ ions in He, Ne and Ar. The spectra for He and Ne targets display eight well‐resolved peaks, the majority of which correspond to capture involving a rearrangement of the electron core configuration. By contrast, the five channels observed in the spectrum for the Ar target are all associated with core‐conserved electron‐capture processes. One pronounced peak in the spectra for He and Ne cannot be explained on the basis of capture from the ground 3P or metastable 1D and 1S states of the Ar4+ ions, and appears to originate from capture by Ar4+ in the hitherto unidentified metastable 5S0‐state at ∼ 7.5 eV above the ground state. All observed channels are spin‐conserved.
Direct analysis of C60 and related compounds with electrospray mass spectrometry
Authors: Liu Tsang‐Yu , Shiu Lung‐Lin , Luh Tien‐Yau , Her Guor‐Rong 
Published: May 2005

AbstractWithout performing any charge transfer chemical reaction, C60 and its derivatives could be analyzed directly by electrospray mass spectrometry. Oxidation or reduction at the metal/solution interface of the probe tip was probably responsible for the formation of these radical cations and anions. This technique appeared to be superior to desorption chemical ionization and fast‐atom bombardment ionization in the analysis of C60 derivatives because the mass spectra were characterized by molecular ions with little or no fragmentation.
Utility of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry for the analysis of low molecular weight compounds
Authors: Lidgard Ray , Duncan Mark W. 
Published: May 2005

AbstractA range of low molecular weight compounds (<800 Da) have been examined by matrix‐assisted laser desorption time‐of‐flight mass Spectrometry to demonstrate the general analytical utility of this technique. The compound classes investigated included: carbohydrates, quaternary ammonium salts, sterols, nucleosides, purine and pyrimidine bases, amino acids, catecholamines, opioids, antibiotics, prostaglandins and a range of macrocyclic metal complexes of porphyrins and phthalocyanines. Many of the compounds tested are of biochemical, geochemical, industrial and/or therapeutic interest. Most organic analytes gave intense protonated molecules, but some were characterized by sodium adduct ions (i.e., [M + Na]+). The metal‐containing compounds formed radical‐cation molecular ions. In all instances the ions detected could be assigned, and excellent agreements between calculated and experimental mass values were obtained.
Effusive molecular beam from a capillary array for improved resolution time‐of‐flight and collision spectrometry
Authors: Bapat Bhas , Krishnakumar E. 
Published: May 2005

AbstractWe report here high mass resolution obtained with an electron impact, Wiley–McLaren type time‐of‐flight spectrometer employing an effusive molecular beam from a capillary array instead of the conventional gas cell. The improvement in resolution is due to the subthermal transverse velocity spread achievable from the well‐directed target beam produced by the capillary array. We also discuss the advantage of using the capillary array in various other spectrometry applications such as translational energy spectrometry and electron spectrometry where the energy resolution is limited by the thermal motion of the target gas.
Polycarbon sulfides CnS (n = 2–6) and corresponding hydrides HCnS.. Neutralization–reionization mass spectrometry and ab initio molecular orbital study
Authors: Flammang Robert , Van Haverbeke Yves , Wong Ming Wah , Wentrup Curt 
Published: May 2005

AbstractA series of polycarbon sulfide radical cations, CnS+· (n = 2–6), have been detected in the 70 eV electron impact mass spectrum of benzothiazole. Application of collisional activation and neutralization–reionization mass spectrometry indicates their connectivity and the stability of the corresponding neutral molecules CnS in the gas phase. Closed shell HCnS+ ions (n = 2–6) and the corresponding radicals HCnS. have similarly been identified in the dilute gas phase of the mass spectrometer. The experimental results are supported by ab initio molecular orbital calculations at the QCISD(T)/6–311G** (based on additivity approximation) + ZPVE level.
Behaviour of catechin and ellagic acid subjected to thermally‐assisted hydrolysis–methylation/gas chromatography/mass spectrometry
Authors: Galletti Guido C. , Bocchini Paolo 
Published: May 2005

AbstractCatechin and ellagic acid, two basic constituents of important natural polyphenols such as condensed tannins and ellagitannins, were subjected to thermally‐assisted hydrolysis–methylation in the presence of tetramethylammonium hydroxide (25% aq.). The reaction was carried out at 600°C for 5 s using a platinum filament pyrolyzer which, in turn, was connected to a gas chromatograph/ion trap detector mass spectrometer. The permethylated compounds determined in the pool of the reaction products suggest that the reaction occurring is different from a simple methylation of free hydroxyls after thermal degradation and entails thermal fission of different bonds than those involved in conventional pyrolysis or chemical hydrolysis as the main decomposition pathway. The mass spectra of the permethylated hydrolysis products of catechin and ellagic acid are of practical use in the analysis of plant materials containing condensed tannins and ellagitannins.