bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative trace analysis by combined chromatography and mass spectrometry using external and internal standards
Authors: Boyd R. K. 
Published: May 2005

AbstractThis review covers established methods for trace organic analysis by quantitative Chromatography. Although these methods are of more general applicability, they are widely used in practice with mass spectrometric detection. In the important class of methods employing surrogate internal standards (usually isotopically labelled versions of the target analytes), mass spectrometry is almost always obligatory in view of the inability to chromatographically resolve such a standard from the analyte in all but a few exceptional cases. The relative strengths and weaknesses of the methods are compared, and distinctions are drawn between ‘best’ methods for different circumstances, e.g., quality control of pharmaceutical preparations compared with analyses of environmental samples.
The 1,2‐phehyl migration of deprotonated benzyldiphenylamine in the gas phase
Authors: Reeks Lachlan B. , Dua Suresh K. , Bowie John H. 
Published: May 2005

AbstractDeprotonated benzyldiphenylamine and its ring‐substituted benzyl derivatives undergo the nitrogen analogue of the Wittig rearrangement in the gas phase to form deprotonated benzhydrylanilines as product anions. The analogous process occurs under base‐catalysed conditions in the condensed phase. The collision‐induced loss of benzene from the rearrangement ion is used as a probe for the rearrangement. It is proposed that this is a stepwise reaction in which the second step (the deprotonation of the CH position by the incipient phenyl anion) is rate‐determining.
Formation of giant fullerene gas‐phase ions (C, 60 ⩽ 2n ⩽ 500): Laser desorption/electron ionization Fourier‐transform Ion cyclotron resonance mass spectrometric evidence
Authors: Wood Troy D. , Van Cleef Garrettt W. , Mearini Michael A. , Coe James V. , Marshall Alan G. 
Published: May 2005

AbstractLaser desorption (followed by electron ionization) Fourier‐transform ion cyclotron resonance (LD/EI‐FTICR) mass spectra have been obtained for thin and thick deposits of purified C60 as well as benzene extracts of fullerene‐laden arc‐welded graphite soot under identical mass spectral conditions. Thick (but not thin) deposits exhibit ‘giant fullerene’‐like carbon cluster‐ion distributions, in either positive‐ or negative‐ion mode; giant fullerene ions observed by mass spectrometry therefore do not necessarily prove that neutral giant fullerenes were present in the original sample, which is consistent with recent laser vaporization and plasma desorption mass spectrometry results. FTICR‐MS of the residual soot remaining after benzene extraction yielded much more abundant ‘giant fullerene’ ions extending above C, which are probably derived both directly from the corresponding giant neutral carbon clusters in the sample and by the nucleation process seen for thick deposits of the extracts. The results shown here firmly establish the importance of sample thickness in the mass spectrometric examination of fullerene soot.
Development of a laser microprobe fourier transform mass spectrometer with external ion source
Authors: Van Vaeck L. , Van Roy W. , Struyf H. , Adams F. , Caravatti P. 
Published: May 2005

AbstractLaser microprobe mass spectrometry (LMMS) employs focused laser‐beam irradiation of solids and subsequent mass analysis of the ions produced. The technique is suitable for the local analysis of inorganic and organic constituents with a spatial resolution in the micrometer range. The Fourier transform mass spectrometer (FTMS) is an analyser of choice for LMMS because high mass resolution and accurate mass determination can be routinely achieved at adequate sensitivity. This paper describes the first LMMS instrument using FTMS with an external ion source. The design considerations and the experimental performance are described with respect to such analytical parameters as spatial resolution and sensitivity. A comparison between time‐of‐flight mass spectrometry and IT‐LMMS for diagnostic analysis of organic molecules is interpreted in terms of the ion formation processes. Finally, the analysis of a selected integrated circuit evidences the feasibility of local analysis with a spatial resolution of 5 μm.
Electron‐impact induced fragmentations of some quinazolinediones and benzoxazinones
Authors: Himottu Marja , Pihlaja Kalevi , Stájer Géza , Vainiotalo Pirjo 
Published: May 2005

AbstractMass spectral fragmentations of 3‐substituted 2,4(1H,3H)‐quinazolinediones, 2‐phenylimino‐4H‐3,l‐benzoxazin‐4‐ones and 2‐thioxo‐2,3‐dihydroquinazolidin‐4(1H)‐one were examined using metastable‐ion analy sis and exact mass measurements. The isomeric compounds were easy to distinguish from their mass spectra. For quinazolinediones, the most surprising feature was the loss of CO2 showing that a rearrangement due to anilino migration must occur in these compounds. In comparison, the benzoxazinones showed no elimination of carbon dioxide.
Reduction of space‐charging in the quadrupole ion trap by sequential injection and simultaneous storage of positively and negatively charged ions
Authors: Williams Jon D. , Cooks R. Graham 
Published: May 2005

AbstractExperiments were performed to establish the effects produced by the sequential introduction and simultaneous trapping of large quantities of positive and negative ions in the quadrupole ion trap. Injection conditions were controlled so that the trap stored only positively charged ions, only negatively charged ions, or both positively and negatively charged ions. Improved peak shapes and mass resolution were observed in positive‐ and negative‐ion mass spectra without loss of ion signal when ions of opposite charge were present in the trap. These results indicate that space‐charging of the trap can be relieved by the addition of ions of opposite charge.
Kinetics of isobaric ion/molecule reactions determined by the flowing afterglow‐triple quadrupole technique
Authors: Brickhouse Mark D. , Chyall Leonard J. , Sunderlin Lee S. , Squires Robert R. 
Published: May 2005

AbstractAn experimental method is described for determining the kinetics of gas‐phase ion/molecule reactions involving reactant and product ions with the same nominal or exact masses (i.e., isobaric ion/molecule reactions) using a flowing afterglow‐triple qvadrupole instrument. The method involves formation of specific monitor ions in the triple quadrupole analyzer by collision‐induced dissociation, exothermic ion/molecule reactions or energy‐resolved ion/molecule reactions for use in determining the kinetics of reaction of one component of an isobaric ion mixture in the flow tube. The measured depletion of these types of monitor ions is shown to provide a reliable means of determining the rate coefficient for the overall reaction taking place when a neutral reagent is added to the flow reactor.
Bimolecular reactions involving the radical site of the distonic ion ·CH2CH2CH2CO+
Authors: Stirk Krista M. , Smith Rebecca L. , Orlowski Joe C. , Kenttämaa Hilkka I. 
Published: May 2005

AbstractA systematic comparison of the reactivity of the γ‐dictonic ion ·CH2CH2CH2CO+ to that of its even‐electron analog, CH3CH2CH2CO+, and a related conventional radical cation, ionized cyclopentanone, was carried out using a dual‐cell Fourier‐transform ion cyclotron resonance mass spectrometer. Each of the ions exhibits unique chemical reactivity. The conventional radical cation reacts with neutral reagents primarily by electron transfer. The even‐electron acylium ion CH3CH2CH2CO+ is unreactive towards most of the neutral molecules studied; slow proton transfer is the only reaction observed with a few reagents. In sharp contrast to the behavior of these two ions, the distonic ion undergoes a variety of reactions with each neutral reagent. Most of these reactions involve a homolytic bond cleavage in the neutral reagent, leading to abstraction of an atom or a radical by the ion. Although reactions directly involving the charge site are not common for this ion, many of its reactions are likely to be catalyzed by the charge site. Initial bond formation at the charge site stabilizes the collision complex, extending its lifetime. This binding may also favorably position the neutral molecule for a subsequent reaction with the radical site of the ion. Accordingly, relatively facile radical abstraction reactions were observed for those reagents which react through a favorable six‐membered transition state after bonding to the charge site. These neutral reagents react similarly, but at a slower rate, with the lower homolog, ·CH2CH2CO+, presumably because a six‐membered transition state is not accessible in this case.
Plasma desorption mass spectrometry of anthocyanidins
Authors: Wood Karl V. , Bonham Connie C. , Ng Jocelyn , Hipskind John , Nicholson Ralph 
Published: May 2005

AbstractPlasma desorption mass Spectrometry (PDMS), developed for the mass analysis of biopolymers, has found application in the analysis of anthocyanidins, an important class of color‐producing compounds in plants. Anthocyanidins, which have hitherto proven extremely difficult to analyze by any type of mass spectrometric technique, can be analyzed routinely to nanogram levels using PDMS. A simple extraction/hydrolysis scheme can be used to screen for these compounds.
Mass spectrometric investigation of the evaporation properties of Ba2CaWO6 and Ba2SrWO6
Authors: Popovič Arkadij , Bencze Laszlo , Marsel Jože , Lesar Antonija , Vass‐Balthazar K. , Kaposi O. 
Published: May 2005

AbstractThe vaporization of Ba2CaWO6 and Ba2SrWO6 was investigated by Knudsen‐cell mass spectrometry. According to the results obtained with a Knudsen cell made of tungsten, the reduction of barium‐calcium tungstates is a non‐equilibrium process magnified image whereas the sublimation of BaWO4 and its decomposition in the gas phase to BaO(g) and WO3(g) are equilibrium reactions. From the temperature dependence of the partial pressure BaWO4(g)
magnified image
the enthalpy of sublimation is obtained as ΔH = 469 ± 4kJ/mol, which is in excellent agreement with the value obtained by third‐law calculations. The origin of the most abundant ions in the gas phase, i.e., BaWO, BaWO, BaO+ Ba+ etc, has been explained from measurements of the corresponding ionization energy (IE) and appearance energy (AE) values.The difference between the AE values for Ba2CaWO6 and Ba2SrWO6 is negligible. The presence of BaWO4 in the condensed phase was confirmed by X‐ray diffraction measurements. Neither X‐ray analysis nor the mass spectra show the presence of CaWO4 or SrWO4 in the solid phase or in the gas phase.
Gas chromatography/mass spectrometric analysis of urinary nucleosides in cancer patients; potential of modified nucleosides as tumour markers
Authors: Langridge James I. , McClure Tom D. , Ei‐Shakawi Salah , Fielding Andrew , Schram Karl H. , Newton Russell P. 
Published: May 2005

AbstractAnalysis of urine from cancer patients by capillary gas chromatography/mass spectrometry positively identified 14 urinary nucleosides including several modified nucleosides. Levels of the modified nucleosides 1‐methyl‐adenosine, 2‐methylguanosine, N2,N2‐dimethylguanosine and 1‐methylinosine as well as the total nucleoside level were elevated in the urine when a malignant tumour was present; the levels of N2,N2‐dimethylguanosine were found to correlate with the stage of the cancer.
Collisional ion activation in the ion trap by a three‐step tickle function
Authors: Paradisi Cristina , Traldi Pietro , Vettori Umberto 
Published: May 2005

AbstractThe effects of performing ion resonance collisional activation in two steps separated by an intermediate phase were studied. The results show that the time duration and the tickle frequency setting used in this intermediate stage determine the phase of the tickle output in the second activation stage which it is essential to control, to ensure the efficiency of the activation process. The following interpretation is offered: the activation process can be efficiently resumed after a period of interruption, provided the tickle voltage in the second activation step is in‐phase with the axial motion of the ions induced by the tickle field during the first activation stage.
Electron impact mass spectrometry and metastable ion studies on 2‐[3‐hydroxy‐2‐pyridyi]‐2‐(3h)‐thiazolimine and 1,3,4‐thiadiazine derivatives
Authors: Hadjieva P. , Kalcheva V. , Tosheva M. , Danieli B. , Catinella S. 
Published: May 2005

AbstractThe mass spectrometric behaviour of some 2‐[3‐hydroxy‐pyridyl]‐2‐(3H)‐thiazolimine and 1,3,4‐thiadiazine derivatives was studied in detail under electron ionizing conditions by means of accurate mass measurements, deuterium‐labelling experiments and metastable ion studies. The resultant fragmentation patterns were highly complicated with cleavage of the amine bond and of the thiazoline ring. The main differences between the decomposition mechanism of thiazoline and thiadiazine derivatives lies in the retro‐synthetic ring transformation processes, observed in the case of thiadiazine compounds only.
Mass spectral fragmentation patterns of unsymmetric furylacrylic acid dicarbonyldichlorides and dianilides: 2,3‐dichloro‐3‐(5‐chloro‐carbonyI)‐2‐furyl‐acrylcarbonylchloride and 2,3‐dichioro‐3‐(5‐anilido‐2‐furyi)‐2‐acrylcarbonylanilide
Authors: Karminski‐Zamola Grace , Dogan Jasna , Bajić Miroslav 
Published: May 2005

AbstractElectron ionization mass spectrometry is shown to provide a valid analytical toot for the structural characterization of the title compounds. Diagnostic fragmentation pathways of an unsymmetrically substituted 2,5‐furan dicarbonyl dichloride and dianilide were observed.
Analysis of clenbuterol in human plasma using liquid chromatography/atmospheric‐pressure chemical‐ionization mass spectrometry
Authors: Doerge Daniel R. , Bajic Steve , Lowes Steve 
Published: May 2005

AbstractClenbuterol is a β‐agonist drug used illegally as a growth stimulant in meat‐producing animals and human athletes. The analysis of clenbuterol in spiked human plasma was performed using on‐line liquid chromatography/atmospheric‐pressure chemical‐ionization mass spectrometry (LC/APCI‐MS) using a conventional bore LC column (flow rate = 1.0 mL/min). At low sampling cone voltages, the mass spectrum was predominantly the [M + H]+ ion but diagnostic fragment ions were formed upon incremental increases in sampling cone voltage. The detection limit (signal‐to‐noise ratio of 3) using selected‐ion monitoring of the [M + H]+ ion was 0.1 ng on‐column (l0 ppb). This is a 50‐fold better sensitivity of detection than that previously reported for an on‐line thermospray LC/MS method. The extraction procedures were not optimized for maximum sensitivity and the lack of interferences suggests that much lower detection limits for clenbuterol in plasma are attainable.
Electronic effects in the electron ionization fragmentations of 2‐aryl substituted octahydro‐1,3‐ and ‐3,1‐benzoxazines
Authors: Vainiotalo Pirjo , Lehtelä Pirjo‐Liisa , Fülöp Ferenc , Bernáth Gábor , Vuorilehto Lauri , Pihlaja Kalevi 
Published: May 2005

AbstractThe 70 eV electron ionization mass spectra of 27 2‐aryl substituted octahydro‐1,3‐ and ‐3,1‐benzoxazines have been recorded in order to find out how the site and stereochemistry of the ring fusion and especially the nature of the substitutent X on the 2‐phenyl group affect their fragmentation patterns. The structural isomers showed clearly different spectra; however, stereoisomeric differentiation was possible only with 1,3‐derivatives. The fragment‐ion peaks connected with the ionized ring and open chain forms of the compounds studied were clearly present in all the spectra. Analogously to the results obtained in solution, the electron‐withdrawing ability of X increased the abundance of the fragments originating from the ring form. Also, the relative importance of different fragmentation channels varied according to the electron donating or withdrawing ability of the substituent X.
Direct observation of UV‐crosslinked protein–nucleic acid complexes by matrix‐assisted laser desorption lonization mass spectrometry
Authors: Jensen Ole N. , Barofsky Douglas F. , Young Mark C. , Von Hippel Peter H. , Swenson Stephen , Seifried Steven E. 
Published: May 2005

AbstractInteractions between proteins and nucleic acids arc important in the fundamental cellular processes that drive replication, recombination, dynamic alteration and repair of DNA, transcription and processing of RNA, synthesis of proteins, and regulation of enzyme activities. As part of an effort to develop a general, sensitive mass spectrometric strategy for the characterization of protein–nucleic acid interactions, we have used matrix‐assisted laser desorption‐ionization (MALDI) time‐of‐flight mass spectrometry to analyze protein–nucleic acid complexes that have been covalently crosslinkcd by ultraviolet (UV) light. In general, the application of MALDI mass spectrometric techniques to studies of U V‐induced crosslinking of nucleoprotein complexes is demonstrated to be feasible. Specifically, MALDI mass analysis was used to determine the molecular weights of the phage T4 gene 32 protein (gp32) crosslinked to the oligonucleotide (dT)20, and the Escherichia coli transcription termination factor rho, photoaffinity labeled with 4‐thio‐uridine‐diphosphate (4sUDP). The covalent gp32:(dT)20 complex is readily detected at a concentration of 1–2 μM in 1 μL of an unpurined solution of reactants thai has been exposed to a single, 266 nm UV laser pulse. Mass spectrometric molecular weight determinations of the covalent rho:4sUDP complex add directness and specificity to the ATPase inactivation assay normally used to monitor the formation of 4sUDP photoafluiity labeled rho. It is found that successful MALDI mass spectrometry of protein–nucleic acid complexes is as critically dependent on the choice of solvents and additives as it is on the primary matrix compound.
Isotope ratio measurements in lead using three‐photon one‐colour resonance ionization mass spectrometry
Authors: Telle H. H. , Telyatnikov A. L. , McNaghton E. D. , Brown R. A. , McCormick A. 
Published: May 2005

AbstractResonance effects on measured isotope ratios in lead using three‐photon one‐colour resonance ionization mass spectrometry are discussed. The shape of the ionization signal is considered for the case of a non‐monochromatic laser field. The intensity of the laser radiation is adjusted to be low enough not to cause saturation of the transitions. The variation of the measured isotope ratio as a function of laser frequency is considered. It is shown that the deviation of the measured from the expected isotope ratio, for a Lorentzian laser lineshape equals the ratio of the isotope shift to the laser bandwidth. Unfortunately, the background noise in the experiments makes verification of this behaviour difficult for the isotopes of low abundance.
Ion mobility spectrometry as a detection technique for the separation sciences
Authors: Jones Dennis , Brenton A. Gareth , Games David E. , Brittain Alan H. , Taylor Stephen , Kennedy David , Smith Peter 
Published: May 2005

AbstractThe development of a high temperature ion mobility, spectrometer is described for interfacing to chromatographic techniques, in particular, gas chromatography and high‐performance liquid chromatography. The performance of the system is assessed by measuring ion mobility constants for both positive and negative ions. The sensitivity of the detector was determined and found to allow the detection of trace components down to tens of picogrammes (pg) for halogenatcd compounds, in the negative‐ion mode of operation. Standard mixtures of potychlorinated biphenyls (PCBs) were studied by gas chromatography/ion mobility Spectrometry with the aim of quantitating extracts of soil samples. A novel method of interfacing to liquid chromatography has been evaluated using a membrane separator of large surface area and high efficiency for removing the mobile phase. Preliminary data for liquid chromatocraphy/ion mobility spectrometry is reported.
Electron‐ionization mass spectra of aminomethyltetrathiafulvalenes
Authors: Garín J. , Orduna J. , Uriel S. 
Published: May 2005

AbstractElectron‐ionzation mass spectra of aminomethyltetrathiafulvalenes were studied by exact mass measurements and metastable‐ion analysis. Cleavages of the C‐N bond and the exocyclic C‐C bond with or without hydrogen rearrangement are the most characteristic fragmentations for these compounds. Ions at m/z 204 and 134 were characterized as tetrathiafulvalene and l,3‐dithiol‐2‐thione molecular ions by collisional activation.
Mass spectrometric location of double‐bond position in isomeric dodecenols, without chemical derivatization
Authors: Yuan Gu , He Meiyu , He Xiaoran , Horiike Michio , Kim Chul‐Sa , Hirano Chisato 
Published: May 2005

AbstractA new procedure is presented for locating double‐bund position in dodecenols. Ten isomers of chemically unmodified dodecenol were analysed by two kinds of mass spectrometers. A series of spectra obtained with a magnetic sector instrument were interpreted by analysing the similarity of mass spectral patterns based on a ‘fuzzy’ reasoning method, in which the intensity ratios of six diagnostic pairs of the predominant ions were defined as standard parameters. The method was tested with other series of spectra from a quadrupole mass spectrometer, and the original double‐bond position in each isomer was located unambiguously.
Investigating the non‐covalent interaction of cytidylic acids, with Ribonuclease A by electrospray mass spectrometry
Authors: Camilleri Patrick , Haskins Neville J. 
Published: May 2005

AbstractElectrospray mass spectrometry has been applied to probe the binding of 2′‐CMP,3′‐CMP and 2′3′‐CMP to RNaseA. Results show that, in the presence of excess amounts of these molecules, binding also appears to occur at a secondary site on the enzyme.
Quantitative aspects of the matrix‐assisted laser desorption mass spectrometry of complex oligosaccharides
Authors: Harvey D. J. 
Published: May 2005

AbstractComparative studies of the matrix‐assisted laser desorption ionization of complex oligosaccharides were made using a range of mono, di‐ and tri‐substituted benzoic acids, substituted coumarins and cinnamic acids. The best results were obtained with 2,5‐dihydroxybenzoic acid (2,5‐DHB). Detection limits using this matrix were in the range of 100 fmol for complex and high mannose sugars, some 2‐fold better than those obtained with α‐cyano‐4‐ hydroxycinnamic acid and 10‐fold better than with an earlier oligosaccharide matrix, 3‐amino‐4‐hydroxybenzoic acid. The strongest signals were achieved with a matrix‐to‐sample ratio of about 5000:1. Little correlation was found between the measured peak height and sample loading when 3‐amino‐4‐hydroxybenzoic acid was used as the matrix and the signal appeared to saturate at a sample level of around 30 pmol. However, good correlation was found between the amount of sample loaded onto the target and the response when an analogous compound was used as an internal standard and peak ratios were measured. In contrast to this, the use of 2,5‐dihydroxy‐benzoic acid as the matrix enabled the oligosaccharide to be measured over the range 100fmol to at least 100pmol with an excellent linear correlation between sample quantity and response and without the need of a standard. No evidence of saturation was found with this matrix. With 2,5‐DHB (other matrices were not tested), the oligosaccharide signal strength was found to fall with increasing molecular weight in a linear manner and similar to that found previously with proteins. Signal strength from individual sugars also fell when these were measured in mixtures. Derivatization (peracetylation) generally caused an increase in signal strength.