bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐resolution ion partitioning technique for a one‐section ion‐cyclotron‐resonance spectrometer cell
Authors: Nikolaev E. N. , Mordehai A. V. , Talrose V. L. 
Published: May 2005

AbstractA technique for isolation of mass‐selected ions in a specially designed one‐section ion‐cyclotron‐resonance cell is described. To demonstrate the potentialities of this technique a model experiment has been performed in which all ions (CO+·, H2O+·, Ar+·, H+…︁) were removed from the cell and only ions of N2+ were left. The removal of the ions was carried out simultaneously, in the direction of the magnetic field. The technique is readily adapted to existing instruments.
Use of m‐nitrobenzyl alcohol as a matrix in fast‐atom bombardment negative‐ion mass spectrometry of polar compounds
Authors: Aubagnac J.‐L. 
Published: May 2005

AbstractFast‐atom bombardment negative‐ion mass spectra of various polar compounds (cyclopeptides, nucleosides, organometallic salts) with a m‐nitrobenzyl alcohol (NBA) matrix exhibit identical characteristics. First, several ions at high masses allow characterization of the molecular weight. Second, at low masses, only ions characteristic of the NBA matrix are observed.
Evidence for a reaction window in double‐electron‐capture reactions in collisions involving the molecular target CH3Br
Authors: Langford M. L. , Harris F. M. 
Published: May 2005

AbstractDouble‐electron‐capture reactions in which singly charged projectile ions A+ convert to negative ions A− in collisions with molecules M are endoergic. Non‐zero cross‐sections for the reactions occur when the endoergicities fall within a ‘reaction window’. The existence of a window for reactions with CH3Br molecules is demonstrated in this investigation by altering the population of ground and excited states of the resulting CH3Br2+ ions using three projectile ions, S+˙, OH+ and F+ which markedly alters the endoergicities of the double‐electron‐capture reactions. Analysis of the energy‐loss spectra indicates that the reaction window for CH3Br is between endoergicities of about 8 and 22 eV. Using F+ as the projectile ion, it is shown that the population of the more highly excited states of CH3Br2+ is enhanced.
A method for the structural determination of cannabichromene metabolites by mass spectrometry
Authors: Harvey D. J. , Brown N. K. 
Published: May 2005

AbstractReady identification of hydroxy metabolites of cannabichromene (CBC) by mass spectrometry of their trimethylsilyl derivatives is prevented by the dominant fragmentation to give a substituted chromenyl ion; this suppresses ions diagnostic of the position of metabolic hydroxylation. To overcome this difficulty, metabolites were hydrogenated over a rhodium/alumina catalyst to reduce the double bond responsible for chromenyl ion formation and to redirect the fragmentation to the site of metabolic attack. This resulted in the production of abundant diagnostic fragment ions enabling all monohydroxy‐CBCs to be readily identified.
Ion cyclotron resonance signal‐detection at multiples of the cyclotron frequency
Authors: Nikolaev E. N. , Gorshkov M. V. , Mordehai A. V. , Talrose V. L. 
Published: May 2005

AbstractA Fourier‐transform mass spectrometric technique for detecting ion cyclotron resonance signals at multiple cyclotron frequencies is proposed and initial experimental results are presented. The technique is readily adapted to existing instruments.
Electrospray ionization on a high‐performance magnetic‐sector mass spectrometer
Authors: Meng Chin‐Kai , McEwen Charles N. , Larsen Barbara S. 
Published: May 2005

AbstractThe feasibility of interfacing an electrospray ion source to a high‐performance magnetic‐sector mass spectrometer is demonstrated. Spectra of peptides and small proteins are obtained with good sensitivity, resolution and mass accuracy. The advantages of using a high‐performance mass spectrometer in conjunction with electrospray ionization are discussed.
An MNDO study of substituent effects on the electronic structure and geometry in the ionization of CH3R compounds (R = H, F, Cl, OH, SH, NH2)
Authors: Hrušá Jan , Tkaczyk Martin 
Published: May 2005

AbstractMNDO calculations on compounds CH3R (where R  H, F, Cl, OH, SH, NH2) enable qualitative correlations to be made between the changes in bond length during ionization and the observed fragmentation of the ion formed. The relatively simple, semi‐empirical MNDO method gives data adequate for the calculation of the geometries and energies involved.
Ion‐spray mass spectrometry of marine toxins II. Analysis of diarrhetic shellfish toxins in plankton by liquid chromatography/mass spectrometry
Authors: Pleasance S. , Quilliam M. A. , de Freitas A. S. W. , Marr J. C. , Cembella A. D. 
Published: May 2005

AbstractA combined liquid chromatography/mass spectrometry (LC/MS) method using ion‐spray ionization is described for the sensitive determination of okadaic acid and dinophysistoxin‐1, the principal toxins implicated in cases of diarrhetic shellfish poisoning. The method is used to confirm the presence of okadaic acid in a culture of the dinoflagellate species Prorocentrum concavum and in natural populations of dinoflagellates from eastern Canadian waters. Several analogues of the toxin have also been detected. Quantitative results are comparable to those obtained by high performance liquid chromatography with fluorescence detection. With slight modifications, the LC/MS method is also used to analyse the fluorescent anthrylmethyl ester of okadaic acid. Preliminary tandem mass spectrometric results, obtained using fast‐atom bombardment ionization, are presented for okadaic acid.
Quantitative analysis of 1‐stearoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphoserine by negative‐ion fast‐atom bombardment mass spectrometry
Authors: Chen Su , Kirschner Günther , Benefenati Emilio 
Published: May 2005

AbstractNegative‐ion fast‐atom bombardment mass spectrometry was evaluated as a means for quantitative analysis of individual molecular species of glycerophosphatidylserine (GPS). With 200 ng of 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphoserine (GPS di 16:0) as an internal standard, the calibration curve for 1‐stearoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphoserine (GPS 18:0–18:1) was linear over a range of 50–1000 ng (signal‐to‐noise ratio >4), with a correlation coefficient of 0.998. When the curve was derived from a mixture of GPS molecular species, only a slight variation in the ion intensity ratio of GPS 18:0–18:1 to GPS di 16:0 occurred. The method provides the possibility of quantifying GPS 18:0–18:1 among GPS species in the low nanogram range.
Sequential multiple‐scan monitoring using an ion‐trap mass spectrometer
Authors: Creaser C. S. , Mitchell D. S. , O'Neill K. E. , Trier K. J. 
Published: May 2005

AbstractNovel scan routines, termed ‘multiple‐scan monitoring’ cycles, have been developed for the rapid sequential acquisition of data from two or more scan types using ion‐trap mass spectrometry. These cycles allow data to be acquired from multiple‐scan functions with a cycle time compatible with combined chromatography/mass spectrometry and other sample introduction methods. Multiple‐scan monitoring is illustrated for the measurement of the components of a test mixture, and for the determination of sulphamethazine and tetrachlorodibenzo‐p‐dioxin.
Thermospray ionization with repeller‐induced collisionally activated dissociation of dyes
Authors: Yinon Jehuda , Jones Tammy L. , Betowski Leon D. 
Published: May 2005

AbstractThermospray ionization with repeller‐induced collisionally activated dissociation (repeller‐CAD) has been used to acquire mass spectra of a series of dyes. These were obtained by applying a voltage of 400 V on the wire repeller. The mass spectra contained a large number of fragment ions which were useful for structural elucidation. Some of these fragment ions were found to be similar to those obtained by thermospray tandem mass spectrometry with CAD and some of them were similar to those obtained by electron ionization using a particle beam liquid chromatograph/mass spectrometry interface. The results indicate that more than one mechanism is involved in the fragmentation process.
Effect of different target gases on low‐energy collision‐activated dissociation of peptides
Authors: Naylor Stephen , Lamb John H. 
Published: May 2005

AbstractExperimental variables affecting the daughter‐ion spectra of a series of protonated peptides [MH]+, produced by fast‐atom bombardment ionization, using a low energy (0–450 eV) quadruple collision cell are investigated. The parameters studied include target gas pressure, collision energy, cross‐sectional area and acidity of the target gas. The results show that low‐mass immonium ions are preferentially formed both at high collision energies (> 200 eV) and at target gas pressures > 10−6 mBar (where multiple collisions occur in the gas cell). Positive fragment ion abundance is maximized when acidic gases are used as the target gases, and this is rationalized on the basis of a proton‐transfer reaction from the target gas to the amide nitrogen of the peptide bond promoting fragmentation.
Do deprotonated semicarbazones undergo the negative‐ion Beckmann rearrangement in the gas phase?
Authors: Adams Gregory W. , Bowie John H. 
Published: May 2005

AbstractMost deprotonated semicarbazones do not undergo the negative‐ion Beckmann rearrangement: instead, simple radical and/or neutral loss is noted, e.g., Me2CNNHCON̄H→[Me2CNNH−(OCNH)]→OCN−+Me2CNNH2. However, dimethyl derivatives do undergo minor fragmentation possibly indicative of a Beckmann rearrangement, e.g., .
Electron ionization mass spectra of some cyclohexane fused 2‐N‐phenyliminoperhydro‐1,3‐oxazines and related thiazines
Authors: Pihlaja Kalevi , Lötjönen Lenita , Fülöp Ferenc , Bernáth Gábor , Vainiotalo Pirjo 
Published: May 2005

AbstractThe 70 eV electron ionization mass spectra of six cyclohexane fused 2‐N‐phenyliminoperhydro‐1,3‐oxazines and six related thiazines were recorded and their fragmentation patterns were studied by metastable‐ion analysis and exact mass measurement. All the compounds examined lost a hydrogen atom from their molecular ion in a process best described as intramolecular cyclization. The most typical fragmentations were the loss of various alkyl radicals from the M+· or [MH]+ ions with the simultaneous migration of one or more hydrogen atoms from the carbocyclic part to the heterocyclic part of the molecule. N‐Substitution clearly affected the type and extent of different reactions. In general, the fragmentation patterns of the thiazine derivatives were more complicated than those of the related oxazines. In all cases studied, the cis‐ and trans‐fused isomers gave rise to so similar spectra that their adequate differentiation was not possible.
Mass spectrometric investigation of diphenylacetylene (tolane)
Authors: Srzić Dunja , Žinić Mladen , Meić Zlatko 
Published: May 2005

AbstractThe electron‐ionization induced fragmentation of diphenylacetylene and its d1, d2, d5 and d10 analogues has been studied by mass spectrometry. The main fragment ions found in the mass spectrum of diphenylacetylene are due to the loss of two hydrogen radicals in a stepwise process and expulsion of C2H2 from the molecular ion in parallel fragmentation pathways producing the fragment ions at m/z 176 and m/z 152, respectively, the latter having possibly a biphenylene radical cation structure. Knowing the actual composition of deuterated derivatives, and the fragmentation pattern of diphenylacetylene, the distribution of the label in these ions was calculated under the assumption that this distribution is statistical. The final results were compared with the experimentally observed spectra of deuterated compounds. This comparison favours the assumption of hydrogen randomization prior to m/z 176 and m/z 152 formation. In contrast to the loss of hydrogen radicals and of C2H2, the formation of m/z 139, 126 and 102 does not involve any major hydrogen scrambling between the phenyl rings.
Collisionally‐activated dissociation of methane molecular ion. Analysis of a mass‐analysed ion kinetic energy peak shape
Authors: Kim Byung Joo , Kim Myung Soo 
Published: May 2005

AbstractCollisionally‐activated dissociation (CAD) of methane molecular ion to methyl ion is studied in the kiloelectronvolt collision energy region by mass‐analysed ion kinetic energy (MIKE) spectrometry. The CAD‐MIKE peak shape was deconvoluted using the algorithm developed previously. The kinetic energy release distribution evaluated from the deconvoluted peak shape exhibits a bimodal feature. This is attributed to the participation of two different mechanisms for collisional activation, leading to electronic and vibrational excitations, respectively.
Time‐of‐flight mass spectrometry of nucleic acids by laser ablation and ionization from a frozen aqueous matrix
Authors: Nelson Randall W. , Thomas Robert M. , Williams Peter 
Published: May 2005

AbstractPositive‐ion time‐of‐flight mass spectra of sodium salts of oligodeoxyribonucleic acids (DNA), and a protein, lysozyme, have been obtained using pulsed‐laser ablation and ionization of frozen aqueous solutions from a cooled copper substrate. The efficiency of positive‐ion formation was found to increase when the ablating laser was tuned to a frequency corresponding to resonant electronic transitions in sodium or copper atoms. Molecular ions of double‐stranded oligomeric nucleic acids, with little fragmentation, were observed at masses up to ∼18 500 Da. Single‐stranded nucleic acids could be fragmented by lowering the laser power‐density to reduce the the substrate heating rate. A dimer ion of lysozyme, at mass ∼29 000 Da, was detected at an impact energy on the electron multiplier of only 3.5 keV.
Design and performance of an electrospray ionization source for a doubly‐focusing magnetic sector mass spectrometer
Authors: Gallagher Richard T. , Chapman John R. , Mann Matthias 
Published: May 2005

AbstractDesign considerations for an electrospray ionization source on a double‐focusing magnetic sector mass spectrometer are discussed. A source with two additional pumping stages before the source housing has been constructed. High sensitivity for multiply charged ions from high molecular weight proteins up to 66 kDa is demonstrated with this source.
Fluorine influence in the mass spectrometric patterns in β‐hydroxy alkyl aryl sulphoxides. Part 5
Authors: Seraglia R. , Traldi P. , Bravo P. , Resnati G. , Bortolini O. , Cavicchio G. 
Published: May 2005

AbstractThe electron ionization mass spectrometry of some β‐hydroxy alkyl aryl sulphoxides halogenated in the γ‐position is described and the mechanism of the common fragmentation patterns are discussed with the aid of linked scans at constant B/E, mass‐analysed ion kinetic energy spectra and labelling experiments. The influence of the presence of halogens is also discussed.
Tandem mass spectrometry in the clinical analysis of variant hemoglobins
Authors: Falick A. M. , Shackleton C. H. L. , Green B. N. , Witkowska H. E. 
Published: May 2005

AbstractA combination of mass spectrometric techniques (electrospray mass spectrometry, liquid secondary‐ion mass spectrometry (LSIMS), tandem mass spectrometry) has been used for variant hemoglobin detection and characterization. Electrospray mass spectrometry allowed analysis of mixtures of intact globins giving the molecuar weights (accuracy 1–2 Da), and information about relative amounts of globins present, simultaneously. Abnormal hemoglobins detected in this way and by other means (screening, clinical symptoms) were fractionated by C‐4 reverse phase high‐performance liquid chromatography (HPLC), and the separated globin chains (or the mixture of whole precipitated globin) were digested with trypsin. The tryptic peptides were separated by C‐18 reverse phase HPLC and analysed by LSIMS to narrow down the mutation site to a single peptide. In some instances, the molecular weight of a variant peptide was sufficient to determine the mutation uniquely. When molecular weight information alone was insufficient to identify the mutation and its site, the peptide was sequenced by tandem mass spectrometry on a 4‐sector instrument. In cases where more than one possible mutation site was present in the peptide and the mutation resulted in a change of only 1 Da in the peptide mass, the resolution and mass measurement accuracy of the 4‐sector machine were esential in determining the correct sequence. The practical application of the methodologies presented is illustrated by the identification and analysis of Hb G‐San Jose, Hb Willamette and Hb D‐Iran.
A membrane‐inlet tandem mass spectrometer for continuous monitoring of volatile organic compounds
Authors: Lauritsen F. R. , Bohatka S. , Degn H. 
Published: May 2005

AbstractA tandem mass spectrometer designed especially for process control can be simplified in several ways by comparison with those instruments used for analysis. A low‐cost membrane‐inlet triple quadrupole mass spectrometer is described that has been designed especially for process control together with examples of continuous monitoring of different organic compounds in mixtures.
Identification of phosphoramide mustard/DNA adducts using tandem mass spectrometry
Authors: Cushnir Julia R. , Naylor Stephen , Lamb John H. , Farmer Peter B. , Brown Nigel A. , Mirkes Philip E. 
Published: May 2005

AbstractThe reaction pathway of alkylating agents is often exploited in the design of bifunctional anti‐cancer drugs. These drugs form mono‐DNA adducts as well as inter‐ and intra‐strand cross‐linked adducts, notably by reaction at DNA bases, including the N‐7‐position of guanine (G). A positive‐ion fast‐atom bombardment (FAB) mass spectrum of an in vitro preparation of DNA alkylated with phosphoramide mustard (the active metabolite of the anti‐cancer drug cyclophosphamide) indicated the presence of the two mono‐DNA adducts N‐(2‐chloroethyl)‐N‐[2‐(7‐guaninyl)ethyl] amine, designated NORG, and N‐(2‐hydroxyethyl)‐N‐[2‐(7‐guaninyl)ethyl] amine, designated NORGOH, (MH+ 257/259 and 239, respectively) but not the presence of the cross‐linked adduct N,N‐bis‐[2‐(7‐guaninyl)ethyl] amine, designated GNORG (MH+ 372). Using synthetic standards, daughterion spectra of NORG, NORGOH and GNORG were obtained (matrix 0.2 M p‐toluene sulphonic acid in glycerol) by positive‐ion FAB tandem mass spectrometry (FAB‐MS/MS). The daughter‐ion spectra of both mono‐DNA adducts NORG and NORGOH contained a fragment ion at m/z 152 [G + H]+, whereas the cross‐linked adduct, GNORG, showed an ion at m/z221, [MH − G]+. Evidence for the presence of NORG, NORGOH and GNORG in the in vitro preparation was obtained by performing a double parent‐ion scan on m/z 152 and 221. The presence of GNORG was further supported by performing a single parent‐ion scan on m/z 221. The use of this MS/MS technique should eliminate the need for intricate sample purification in the identification of GNORG in biological extracts.
The analysis of smokestack samples for dioxins by gas chromatography/mass spectrometry and gas chromatography/tandem mass spectrometry
Authors: Moore Colin , Moncur John , Jones David , Wright Barry 
Published: May 2005

AbstractA CONCEPT 1 SQ hybrid mass spectrometer has been used to show the potential of high resolution mass spectrometry and hybrid tandem mass spectrometry (MS/MS) for dioxin analysis. The usual method chosen for gas chromatography/mass spectrometry (GC/MS) determination of polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) is selected‐ion monitoring (SIM) at high resolution, the high resolution imparting a degree of specificity to the analysis. An alternative technique is to use low resolution (1000) gas chromatography/tandem mass spectrometry on a hybrid mass spectrometer, where the specificity of MS/MS is utilized. Data are presented illustrating the potential of both techniques from a single instrument, the CONCEPT 1 SQ.
Deuterium exchange studies in the identification of alkylated DNA bases found in urine, by tandem mass spectrometry
Authors: Cushnir Julia R. , Naylor Stephen , Lamb John H. , Farmer Peter B. 
Published: May 2005

AbstractHumans are exposed to a large number of carcinogens which may react at various sites throughout the body, including the N‐7‐, N2‐, and O6‐positions of guanine. The effects of this are various but may result in depurination and eventual excretion of the modified base in the urine. Various alkylguanine derivatives with substituents at the N‐7‐, N2‐ and O6‐positions were synthesized and daughter‐ion spectra obtained. Apart from the methyl and dialkylguanines all other spectra exhibited an ion at m/z 151 using electron ionization (EI) and m/z 152 using fast‐atom bombardment (FAB). The daughter‐ion spectra of dialkylguanines contained an ion at m/z 150 (EI). Hence, scans of m/z 150 and 151 using EI, to detect all parent‐ions from which they are formed (parent‐ion scans) should indicate the presence of alkyl and dialkylguanine bases in a complex biological matrix such as human urine. Parent‐ion scans of m/z 150 and 151 (EI) of a partially purified human urine sample exhibited numerous ions, including a prominent ion at m/z 179. A daughter‐ion spectrum of m/z 179 revealed fragment ions that suggested the presence of N2‐dimethylguanine and an ethylated guanine. Any confusion due to the presence of daughter ions from different alkylguanines in the same spectrum can be resolved by the fact that an ethylated guanine has four exchangeable protons, whereas N2‐dimethylguanine has only three. By performing hydrogen/deuterium exchange it is possible to distinguish the N2‐dimethylguanine from ethylated guanine isomers. Daughter‐ion spectra of m/z 180–183 (EI) and 182, 184 (FAB) on human urine enabled us to identify the presence of N2‐dimethylguanine and N2‐ethylguanine.
Theoretical studies of ion trajectories in quadrupole systems
Authors: Barber M. , Gordon D. B. , Woods M. D. 
Published: May 2005

AbstractA brief introduction to the mathematical theory of quadrupole systems is given and the configuration of hyperbolic and circular cross‐section rods is considered. Application of the theory of electrostatics to the latter case indicates that multipole contributions to the field occur which influence the ion trajectories. We have considered motion in the x‐z plane of a static quadrupole (DC‐only) for the simplest case of a 1:1 combination of quadrupole and dodecapole contributions. The quadrupole contribution to ion motion is simple harmonic and may be described as a sine function, whereas the dodecapole contribution may only be obtained by solving the appropriate elliptic integral. This solution gives rise to a sine (amplitude) or sn function. In the case of collision cells (RF‐only) we have attempted to solve the Mathieu equation both analytically and numerically. Both stable and unstable trajectories may be calculated from these solutions and are presented in various formats. Some consideration is also given to the problems of collisional interaction and the associated difficulties likely to be encountered when the study is expanded to include this phenomenon.
The use of tandem mass spectrometry for the differentiation of bile acid isomers and for the identification of bile acids in biological extracts
Authors: Eckers Christine , New Anthony P. , East Philip B. , Haskins Neville J. 
Published: May 2005

AbstractTandem mass spectrometric (MS/MS) techniques have been widely used for the differentiation of isomeric compounds, since their spectra may show differences sufficient to distinguish between them. There are several different ways by which the MS/MS data can be obtained depending on the energies of the ions and the collisions. In this paper MS/MS spectra have been obtained for a group of isomeric bile acids using: 1, low‐energy ions and low‐energy collisions in a triple quadrupole mass spectrometer by liquid chromatography/MS/MS; 2, high‐energy ions and low‐energy collisions in a hybrid mass spectrometer by fast‐atom bombardment MS/MS. Liquid chromatography combined with tandem mass spectrometry (LC/MS/MS) has also been used to identify the bile acids present in biological matrices such as bile extracts.