bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulsed axial activation in the ion trap: A new method for performing tandem mass spectroscopy (MS/MS)
Authors: Lammert S. A. , Cooks R. G. 
Published: May 2005

AbstractA short DC voltage pulse is applied to one endcap of a quadrupole ion‐trap mass spectrometer to activate trapped ions. High internal‐energy deposition is achieved as evidenced by 91+/92+ peak ratios in excess of 20 for dissociation of the n‐butylbenzene molecular ion.1 The amount of internal energy can be controlled directly by vaarying the amplitude of the pulse. Dissociation efficiencies are less than those typically observed for collision‐induced dissociation in the ion trap and range from 50% at low internal energy deposition to 5% at maximum internal energy deposition.
Sensitivity of fast‐atom bombardment mass spectrometry to various polymorphic forms of cortisone acetate
Authors: Gubskaya A. V. , Boryak O. A. , Kosevich M. V. , Shelkovsky V. S. , Blagoy Yu. P. 
Published: May 2005

AbstractThe present paper discussses non‐traditional possibilities of the applications of mass spectrometry to the detection and study of differences in crystal polymorphic forms. The parameter of fast‐atom bombardment which is sensitive to different polymorphs, namely the rate of the formation of cluster ions of an analyte with the glycerol matrix, was chosen for study. Using as an example the analysis of four different samples of cortisone acetate, varying in their polymorphic forms, treatment procedures, and dispersion of the crystalinepowder, it is shown that the relative intensity of the cluster ion [MGH]+ (where M repressents the analyte and G a molecule of glycerol) differs for two of the polymorphic forms and is the same for one of these forms, whether it is obtained by recrystallization from chloroform or by cryogrinding. Analysis of the time dependences of the [MGH]+ ion intensity allowewd us to detect finer effects in the samples, associated with cryogrinding, namely differences in solubility and presumably, mechanoactivation.
Structure of underivatized branched oligosaccharides by negative‐ion fast‐atom bombardment mass spectrometry
Authors: Garozzo D. , Impallomeni G. , Mantaudo G. , Spina E. , Daolio Sergio 
Published: May 2005

AbstractWe report here a study by negative‐ion fast‐atom bombardment (FAB) mass spectromatry of branched oligosacharides containing a 3‐O glyesidie linkage. Our result show that discrimination of the monosaccharide unit linked in the 3‐O position is made possible by the analysis of the negative‐ion FAB mass spectra. In the mass spectrum of A‐trisaccharide (α‐Fuc1‐2‐(α‐GalNAc1‐3)‐Gal) the peak at m/z 307 can be explained as elimination of a neutral molecule of GalNAc(221 u) from the molecular ion. Also in the mass spectrum of 3‐fucosyllaactose (α‐Fuc1‐3‐(β‐Gall‐4)‐Glc) an intense peak at m/z 323, corresponding to the elimination of the fucose linked at the 3 position of glucose is present. To investigate further the fragmentations of the 3‐O‐linked sugars, the negative‐ion FAB mass spectra of disaccharides have also been studied.
Cation attachment in the analysis of polystyrene and polyethylene glycol by laser‐desorption time‐of‐flight mass spectrometry
Authors: Llenes Christopher F. , O'Malley Rebecca M. , Cotter R. J. 
Published: May 2005

AbstractAl+, Cr+ and Cu+ gas‐phase ions have found to attach effciently to two polymers, polystyrene and polyethylene glycol (PEG) in laser‐desorption time‐of‐flight experiment, and are shown to be viable alternatives to be commonly used Na+, K+ and Ag+ ions. At high laser powers, in the range 8.0 × 107 to 2.0 × 108 W/cm2, ions can be attached by desorption from a support made of the apporoptite meal. An alternative method is to add the metal ion in the form of a salt containing the metal in the +1 oxidation state, when such salt are available. This method requires lowe laser powers, in the range 2.0 × 107 to 8.0 × 107 W/cm2. The two desorption/attachment methods are characterized by different optiomal time‐delay values for recording of spectra. Polystyrence has been found to have a hight affinity for attachemnt to Al+, Cr+, and Cu+ than to K+, while PEG has ben found to have a hight affinity for K+ than for Al+, Cr+. These preferential attachments are discussed in terms of the hard and soft acids and bases principle.
Black canyons for ions stored in an ion‐trap mass spectrometer
Authors: Eades Donald M. , Yost Richard A. , Cooks R. G. 
Published: May 2005

AbstractEffects from higher order non‐linear resonances, ‘black canyons’, have been observed for ions stored within the quadrupole ion‐trap mass spectrometer. At specific qz values, higher‐order field effects were observed to cause decreased intensity of chemical ionization (CI) reagent ions, due to ineffcient storage, as well as collision‐induced dissociation. Efects have been observed, whether or not the CI reagent ions are mass‐selected, and exibit increased severity with longer storage times. Previous reports have shown ‘black holes’ due to inefficient storage of product ions in tandem (MS/MS) spectra, but have reported no such effects in normal mass spectra. Without employing resonant excitation, higher‐order field effects were investigated and found to occur continuously along iso‐βz lines for βz = 1/3, 1/2, and 2/3. Described in this paper are the directs from higher‐order fields on ions stored at specific az values, and indirec effects by those ions. Also described in this paper is new evidence for ‘black canyons’ occurring at βz = 1/3 at negative az values.
Gas phase relative proton affinities from selected‐ion flow tube (SIFT) rate constant measurements
Authors: Dotan I. , Iraqi M. , Petrank A. , Lifshitz C. , Viggiano A. A. 
Published: May 2005

AbstractA new method of measuring equilibrium constants of proton transfer gas phase reactions is proposed. The method is based on measuring only the endothermic direction. The expression developed is: Kkexp(BR)kc/{(kckexp)k′c}, where kexp is the measured rate constant, BR is the branching ratio of the proton transfer channel, kc and k′c are the forward and reverse collision rates. Two reaction systems were measured: the equilibrium between methanol and chloroacetonitrile and the equilibrium between ethanol and acetaldehyde. Both equilibrium constants were calculated by measuring forward end reverse rate constants and by the new method. There is good agreement between the two methods and with previously published values.
Analysis of organic pollutants in air by thermal desorption/gas chromatography/mass spectrometry using a home‐made cryofocusing device
Authors: Pucci Sergio , Raffaeli Andrea , Lazzaroni Raffaello , Salvadori Piero 
Published: May 2005

AbstractThis paper describes a simple and cheap home‐made cryofocusing device useful in thermal desorption/gas chromatography/mass spectrometry (GC/MS) to achive the refocusing of the substances desorbed, in order to us use different flow rates during the desorption time (higher flow rate) and the GC/MC analysis (lower flow rate). Some preliminary results of the qualitative and quantitave determinatino of organic pollutants present in air are also presented. The combinatin used, comprising dynamic adsorption/thermal desorption/cryofocusing/GC/MS, allowed us to reach detection limits in the upper ng/m3 (that is, the upper part‐per‐trillion range) per single component.
Quantitation by fast‐atom bombardment mass spectrometry: Assay of cytidine 3′, 5′ ‐cyclic monophosphate‐responsive protein kinase
Authors: Newton Russell P. , Khan Jalal A. , Brenton A. Gareth , Langridge James I. , Harris Frank M. , Walton Terence J. 
Published: May 2005

AbstractA protein kinase, stimulated by cytidine 3′, 5′ ‐cyclic monophosphate, is conventionally assayed by monitoring the incorporation of radiolabelled phosphate from adenosine triphosphate into a histone substrate. Here the assay of the protein kinase is carried out by positive‐ion fast‐atom bombardment mass spectrometric analysis of the enzyme incubation mixture after the reaction has been terminated. The data so obtained show good agreement with data obtained by the conventional radiometric assay: the intrinsic advantage of the mass spectrometric assay is the capacity for multiple component monitoring; the ability of the kinase to bind competing cyclic nucleotides togeter with integral adenosine triphosphatase (ATPase) and phosphodiesterase activity can also be assessed.
252Cf plasma‐desorption mass spectrometry of lipid a from Enterobacter agglomerans
Authors: Cole Richard B. , Domelsmith Linda N. , David Connie M. , Laine Roger A. , DeLucca Anthony J. , Promé J. C. 
Published: May 2005

AbstractEndotoxins from gram‐negative bacteria are believed to be causative agents of byssinosis, an occupational pulmonary disease associated with exposure to cotton dust in textile mills. Lipid A preparations from Enerobacter agglomerans, a gram‐negative bacterium commonly found in cotton and cotton dust, have been analyzed using plasma‐desorption mass spectrometry. Results indicate the existence of at least two lipid A types which differ only by the presence of an additional oxygen atom whose position has been localized to the acyloxyacyl ester‐linked side‐chain of the distal portion of the molecule. The lower molecular weight compound of the two structures has the same molecular weight and presumably the same empirical formula as a well‐characterized lipid A from Salmonella minnesota. The mass spectra of lipid A compounds obtained from S. minnesota and E. agglomerans show strong similarities. Palmitoyl, hydroxymyristoyl, myristoyl, and lauroyl side‐chains which are known to be prest in the former are inferred from spectral evidence to be present in the latter.
C‐terminal sequencing of peptides using electrospray ionization mass spectrometry
Authors: Rosnack Kenneth J. , Stroh Justin G. 
Published: May 2005

AbstractA low‐flow reactor is described for the on‐line monitoring of peptides digested with carboxypeptidase P by electrospray ionization. Two peptides were analyzed using this technique: glucagon (average MW 3482.8 Da), and apomyoglobin (average MW 16 951.5). Both peptides gave interpretable results. The first 19 amino acids of glucagon were successfully sequenced. Apomyoglobin yielded sequence information to the 30th amino acid with some gaps. At 300 nL/min, 50% of the first 30 amino acids were sequenced and at 1μL/min, 67% of the first 30 amino acids were observed.
Sequence distribution of β‐hydroxyalkanoate units in bacterial copolyesters determined by desorption chemicl ionization mass spectrometry
Authors: Abate Rosaria , Garozzo Domenico , Rapisardi Roberto , Bllistrei Alberto , Montaudo Giorgio 
Published: May 2005

AbstractThe sequence distributions of poly(β‐hydroxyalknoate) copolymers were determined by analyzing oligomers obtaned by the pyrolysis direct‐chemical‐ionization (DCI) mass spectrometry technique. Oligomers up to nonamers were identified and the comparison between the experimental and calculated peak intensities makes it possible to calculate repeating unit compositions and sequence distributions. Comparison with other earlier methods are given.
Disentangling electrospray spectra with maximum entropy
Authors: Ferrige A. G. , Seddon M. J. , Green B. N. , Jarvis S. A. , Skilling J. , Staunton J. 
Published: May 2005

AbstractSoftware using maximum entropy (MaxEnt) analysis has been developed, and used to econvolute complete electrospray spectra of protein mixtures. It automatically produces zero‐charge mass spectra on a molecular mass scale, along with probabilistic quantification so that the reliability of features in the spectrum can be ascertained. Because maximum entropy is faithful to the experimental data, the results tend to have improved resolution and signal‐to‐noise ratio. This improved performance, particularly regarding resolution, is demonstrated on a haemoglobin containing two β‐globins separated by 12 Da at m/z 15 867 (0.08%). A separation of 12 Da was previously the closest at which mass measurement of two globins was practicable. Also, two hiherto unresolved β‐globins from a second haemoglobin, separated by 9 Da (0.06%) were resolved by MaxEnt and their masses accurately measured. These are the first results using rigorous MaxEnt analysis in electrospray mass spectrometry.
Capillary column gas chromatography/tandem mass spectrometry verification of chemical warfare agents
Authors: D'Agostino P. A. , Porter C. J. 
Published: May 2005

AbstractChemical weapons use, although prohibited by the 1925 Geneva Protocol, has been reported in several armed conflicts including the Iran/Iraq war. The use of these weapons during this conflict and the concern over possible use of chemical warfare (CW) agents during the Persian Gulf war has heightened international awareness and prompted many nations to pursue with incresed vigour the signature of a new Chemical Weapons Convention. The most recent draft of the Chemical Weapons Convention contains a number of provisions aimed at developing a treaty that will enable nations to ensure compliance by all signatory nations. Compliance monitoring will be required in a number of scenarios, including the verification of alleged use, the storage and destruction of chemical weapons stocks and ensuring that industrial sites are not illegally producing CW agents. It follows from this draft treaty that compliance monitoring will require a high level of sophisticated analytical support to ensure the establishment of an enforceable treaty. The United Nations Conference on Disarmament therefore formed a multi‐national Technical Group on Instrumentation to address the analytical challenges confronting signatory nations.
Bimolecular reactions of ˙CH2CH2OCH: A comparison with the chemical properties of CH3CH2OCH and ionized trimethylene oxide
Authors: Kenttämaa Hilkka I. , Kiminkinen L. K. Marjatta , Orlowski Joseph C. , Stirk Krista M. 
Published: May 2005

AbstractThe chemical properties of the distonic radical cation ˙CH2CH2OCH are compared with those of its conventional isomer, ionized trimethylene oxide, and its even‐electron analog, the ethoxymethyl cation (CH3CH2OCH). The rate constants and branching rations have been determined for the gas‐phase reactions of the three ions with several neutral reagents in a dual‐cell Fourier‐transform ion cyclotron resonance device. The reactivity of each ion is found to be quite distinct. Fast electron transfer dominates most of the bimolecular reactions of ionized trimethyleene oxide. The ethoxymethyl cation reacts slowly or not at all with the reagents studied, and the only reaction observed is ethyl cation transfer. The distonic ion ˙CH2CH2OCH undergoes vedry fast reactions with all the neutral reagents, and, in sharp contrast to the other two ions, shows remarkably versatile reactivity. This ion rapidly transfers ionized ethylene to most of the neutral molecules studied. Facile electron transfer occurs with some of the neutral reagents while others abstract a pproton from the ion. Abstraction of a radical by the distonic ion‐a reaction reported earlier for dimethyl disulfide—is not observed for any other reagent.
The stretched quadrupole ion trap: Implications for the Mathieu au and qu parameters and experimental mapping of the stability diagram
Authors: Johnson Jodie V. , Peddeer Randall E. , Yost Richard A. , March R. E. 
Published: May 2005

AbstractThe effect of the radial and axial dimensions on the Mathieu stability diagram (in terms of DC and RF voltages) is discussed with relation to the ‘stretched’ geometry employed in the Finningan MAT quardrupole ion‐trap mass spectrometer (ITMS). Equations are presented for the conversion of the Mathieu au and qu parameters to DC voltages and RF voltages, respectively, and vice versa on the ITMS. A TURBOBASIC program is discussed which will provide data for graphing of a stability diagram in (RF, DC) space. Experimentally determined boundaries of the stability diagram are in good agreement with an approximate model for the stretched trap.
Matrix‐assisted laser desorption/ionization mass spectrometry of nucleic acids with wavelengths in the ultraviolet and infrared
Authors: Nordhoff E. , Ingendoh A. , Cramer R. , Overberg A. , Stahl B. , Karas M. , Hillenkamp F. , Crain P. F. , Chait B. 
Published: May 2005

AbstractA number of different matrices have been tested and compared for ultraviolet and ubfrared (UV and IR) matrix‐assisted lasedr desorption/ionization (MALDI) of oligodeoxyribonucleotides and mixtures thereof, as well as ribonucleic acids (tRNA from yeast and rRNA from Ecoli). A new technique for removing alkali cations from nucleic acid samples during sample preparation on the sample support is demonstrated. The amount of oligonucleotide sample consumed during a typical measurement in IR‐MALDI‐MS was determined.
High resolution accurate mass measurement of product ions formed in an electrospray source on a sector instrument
Authors: Starrett Anne M. , DiDonato Gerald C. 
Published: May 2005

AbstractThe high resolution accurate mass measurement of product ions formed by collisionally activated dissociation in an electrospray source has been achieved using a reversed‐geometry double‐focusing mass spectrometer and accelerating voltage scans. Accurate mass measurements of product ions from angiotensin I, angiotensin II, leucine enkephalinamide, substance P (1–9) and a synthetic compound of pharmaceutical interest were obtained with an average error of <5 ppm.
Desorption chemical ionization mass spectrometry of arsenic compounds present in the marine and terrestrial environment
Authors: Cullen William R. , Eigendorf Guenter K. , Pergantis Spiros A. 
Published: May 2005

AbstractThe advantages of desorption chemical ionization mass spectrometry (DCI‐MS) for characterizing arsenic compounds that exist in the environment include the presence in the spectra of recognizable molecular ions as well as structurally characteristic fragment ions. Satisfactory spectra can be obtained with 100 ng arsenic on the DCI filament, making the technique eminently suitable for the investigation of environmental samples.
Thermal surface ionization of quaternary ammonium salts in particle‐beam mass spectrometry
Authors: van der Hoeven R. A. M. , Tinke A. P. , Niessen W. M. A. , van der Greef J. 
Published: May 2005

AbstractThe applicability of thermal surface ionization in liquid chromatography/particle‐beam mass spectrometry is investigated for the analysis of quaternary ammonium compounds. The compounds are mass anlyzed in a filament‐off mode of operation with a particle‐beam interface. An intense signal of the molecular cations is observed, while fragmentation can be induced by gas collisions and characterized using tandem mass spectrometry. A significant gain in signal‐to‐noise ratio in thermal surface ionization relative to electron ionization is observed.
Enhanced mass resolution in a quadrupole ion trap
Authors: Londry Frank A. , Wells Georgy J. , March Raymond E. 
Published: May 2005

AbstractThe versatility of the quadrupole ion trap as a mass spectrometer in which the mass resolution may be varied over a wide range has been demonstrated. Mass resolution of 0.8 × 107 and 1.2 × 107 have been obtained for ions of m/z 414 and m/z 614, respectively, well in excess of the normal value of 3m, where m is the mass of ion. At the highest mass resolution, peak‐widths at half‐maximum are but 52 × 10−6 u. While it has been shown previously that enhanced mass reslution in the quadrupole ion trap can be achieved by reduction of the mass scanning rate, the range of mass resolutions reported here were achieved by reducing the mass scanning rate, in stages, by an overall factor of ca 5.5 × 104.
Fast‐atom bombardment mass spectrometric determination of methyl[1‐(butylcarbamoyl)‐1H‐benzimidazol‐2‐yl]carbamate (benomyl) in wettable powder formulations
Authors: Singh Raj P. , Brindle Ian D. , Jones Timothy R. B. , Miller Jack M. , Chiba Mikio 
Published: May 2005

AbstractIn this Communication we report, for the first time, a direct method for the determination of benomyl (methyl [1‐(butylcarbamoyl)‐1H‐benzimidazol‐2‐yl]carbamate) in wettable powder formulations by fast‐atom bombard‐ment mass spectrometry (FAB‐MS). Solutions of desired concentrations of benomyl were prepared in 5 M hydrochloric acid. The matrix compound, glycerol, was added at 10% (v/v) to these solutions for obtaining FAB mass spectra. The results of the analysis of wettable powder samples, carried out by FAB‐MS, compared well (p > 0.05) with those obtained by reversed‐phase high performance liquid chromatography.
Influence of acetylation on the [M + Na]+ ion formation of simple phenol and aniline compounds under fast‐atom bombardment conditions
Authors: Takayama Mitsuo , Tanaka Yoshiaki , Nomura Taro 
Published: May 2005

AbstractThe influence of acetylation on the formation of sodium adduct [M + Na]+ ions, under fast‐atom bombardment conditions, has been investigated using monosubstituted phenol and aniline compounds. The acetylation of o‐isomers, except for the nitrophenols, highly enhanced the [M + Na]+ ion formation, while m‐ and p‐isomers showed little effect on acetylation except for p‐methoxyphenol and aniline. The favorable effect of acetylation on [M + Na]+ ion formation is explained by the conformational flexibility of COAc and GNHAc functions and the carbonyl oxygen as a cation‐accepting site, which are advantageous for the multisite interaction with a Na+ ion.
Liquid chromatography/mass spectrometry analysis of an enkephalin mixture using an autospec dynamic liquid secondary‐ion mass spectrometer interface
Authors: Woolfitt A. R. , Harbach C. A. J. 
Published: May 2005

AbstractA mixture of four enkephalins was separated by reverse‐phase high‐performance liquid chromatography combined with dynamic liquid secondary‐ion mass spectrometry. A newly developed screen/wick target made the method sensitive and reproducible.
Electron impact mass spectrometry and metastable ion studies on some 2‐(o‐hydroxyphenyl‐2(3H)‐thiazoline‐imine) and 1,3,4‐thiadiazine derivatives
Authors: Hadjieva P. , Kalcheva V. , Tosheva M. , Danieli B. , Catinella S. 
Published: May 2005

AbstractThe electron‐impact induced mass spectrometric behaviour of nine differently substituted 2‐(o‐hydroxyphenyl)‐2(3H)imino‐4‐thiazolines and one 2‐(o‐hydroxyphenyl)‐imino‐l,3,4‐thiadiazinc has been studied in detail with the aid of accurate mass measurements, linked‐scans for metastable‐ion studies and deuterium‐labelling experiments. The related fragmentation pathways are strongly dependent on the presence of a substituent nitrogen atom in pt, ition 3, which can promote a hydrogen rearrangement process on the inline nitrogen and the further cleavage of the iminic bond. In the case of an arylic substituent, specific fragmentation channels are activated, due to the high stability of the resultant product ions.
An investigation of the precision of isotopic abundances determined by secondary ion mass spectrometry
Authors: Testino Samuel A. , Busch Kenneth L. 
Published: May 2005

AbstractThe precision with which the isotopic abundances of palladium and tin can be measured under secondary ion mass spectrometric (SIMS) conditions typically used for organic compound analysis has been determined. The relative abundances of the isotopic peaks, and their associated standard deviations, vary with the number of scans averaged to achieve a spectrum. A representative spectrum is not obtained until more than 40 scans are averaged. In addition, there is a strong correlation between standard deviation and absolute signal intensity. This relationship can allow one to determine the number of scans that need to be averaged to predict true experimental abundances reliably, based on signal intensities.
Fast‐atom bombardment mass spectrometry in the stereochemical characterization of a new group of C30 nuphar alkaloids
Authors: Bortolini O. , Labianco A. , Curcuruto O. , Traldi P. , Wròbel J. T. , Iwanow A. 
Published: May 2005

AbstractA new group of thio‐C30 nuphar alkaloids has been obtained from the three main stereoisomers by complete oxidation of the sulphur and both the tertiary nitrogen sites. High‐resolution mass spectrometry and metastable‐ion decomposition analysis were used to distinguish and characterize diastereoisomers.