bluuebunny/crossref_metadata_2025_split huggingface dataset:
Matrix‐assisted laser desorption/ionization Fourier‐transform mass spectrometry of oligodeoxyribonucleotides
Authors: Stemmler E. A. , Hettich R. L. , Hurst G. B. , Buchanan M. V. 
Published: May 2005

AbstractConditions for the matrix‐assisted laser desorption/ionization (MALDI) of oligodeoxyribonucleotides at 355 nm, developed using a 3‐Tesla Fourier‐transform ion cyclotron resonance mass spectrometer (FTMS), are reported. Efficient ion trapping and matrix selection are critical to the desorption and detection of oligonucleotides by FTMS. The achievable upper mass limit for the MALDI‐FTMS of bio molecules on our 3‐Tesla system has been extended from approximately 2 kDa to 6 kDa through the use of pulsed‐trapping‐plate ion deceleration techniques. By implementing the deceleration techniques, molecular ions for bovine insulin (MW = 5733.5), an oligodeoxythymidylic acid, pd[T]10(MW = 3060.0), and a mixed‐base 12‐mer (MW = 3611.5) have been measured. For the analysis of oligonucleotides by FTMS, selection of an appropriate MALDI matrix is essential for the generation of [MH]−ions. 3‐Hydroxypicolinic acid provides a significant improvement over 2,5‐dihydroxybenzoic acid for production of deprotonated molecules particularly for mixed‐base oligomers. MALDI studies using FTMS have been duplicated using a newly constructed time‐of‐flight mass spectrometer (TOFMS) and oligonucleotide fragmentation on the TOFMS is reduced relative to that observed by FTMS. This may be a consequence of the longer times (milliseconds) required for FTMS detection.
Solvation of transition‐metal ion complexes in the gas phase
Authors: Wilson Kimber L. , Buckner Steven W. 
Published: May 2005

AbstractSolvation of the gas‐phase transition‐metal d0 complexes ScO+, YO+, YCHCN+ and NbO with some protic and aprotic solvents has been studied using Fourier‐transform ion cyclotron resonance mass spectrometry. The relative rate constants for formation of the solvated oxides show strong non‐monotonic fluctuations with increasing extent of solvation. For ScO+ and YO+ the third solvent molecule attaches more rapidly than the second, while for NbO the second attaches more rapidly than the first. This behavior suggests that in spite of the formal d0 character of the metal centers in these systems, simple electrostatic binding is not occurring. In contrast, YCHCN+ shows a continuous decrease in the rate for solvation with up to three molecules of CH3CN. The effects of solvation on the subsequent reactions of the metal oxides has been studied. YO+ solvation (with up to three H2O or two NH3 molecules) does not affect its arene CH bond activation reactions. However, solvation of ScO+ and NbO with one or two NH3 or H2O molecules shuts off benzene dehydrogenation.
Electrospray ionization mass spectrometry coupled with size‐exclusion chromatography
Authors: Prokai Laszlo , Simonsick William J. 
Published: May 2005

AbstractThe coupling of electrospray ionization mass spectrometry with gel permeation chromatography (GPC) has been used for the separation of a commercial polydisperse mixture of octylphenoxypoly(ethoxy)ethanol. Stable electrospray conditions are obtained upon using, as GPC solvent, tetrahydrofuran containing 10−5−10−4M sodium salt which also provides for the formation of intact molecular ions through cationization. Selected‐ion chromatograms of sodiated species allow for the monitoring of the elution profiles of individual oligomers, and can be used for the calibration of the GPC.
Multiply pulsed collision gas for ion axialization in fourier‐transform ion cyclotron resonance mass spectrometry
Authors: Guan Shengheng , Marshall Alan G. 
Published: May 2005

AbstractWe present a new multiply pulsed collision‐gas technique forion axialization for Fourier‐transform ion cyclotron resonace (FTICR) high‐resolution mass analysis. Ions are axialized in the source trap of a dural‐trap FTICR spectrometer y aimuthal quadrupolar irradiation for several tens of seconds at a steady‐state pressure maintained y repeated pulses of coolision gas (argon), folowed by removal of the collision gas and detection at a much lower pressure after transfer to the analyzer trap. Magnitufe‐mode FTICR mass resolving power, m/Δm≈︁1770000, for [M + K]+ ions from laser‐desorbed/ionized leucne enkephalin at m/z 594 is demonstrated. This resolving power is the highest yet reported for a peptide with any type of laser desorption/ionization mass analyzer.
Characterization of melanins by pyrolysis/gas chromatography/mass spectrometry
Authors: Vas György , Vékey Károly , Czira Gábor , Tamás József , Favretto Donata , Traldi Piero , Bertazzo Antonella , Costa Carlo , Allegri Graziella 
Published: May 2005

AbstractVarious natural and synthetic melanins were studied by the pyrolysis/gas chromatography/mass spectrometry technique, using both resistive and Curie‐point heating. The results obtained by the two pyrolysis procedures are different and complementary. By means of Curie‐point pyrolysis, at long times and high temperatures low molecular weight gases are produced from various melanins; the yields of the common pyrolysis products are also dependent on the melanin under study. By resistive heating, higher molecular weight compounds are produced, mainly nitrogen and oxygen heterocyclic systems, and differences are still evident among the products from the different melanins.
Suppression effects on a reduction process in fast‐atom bombardment mass spectrometry
Authors: Murthy Vemisetty S. , Miller Jack M. 
Published: May 2005

AbstractVarious methods of suppression of the reduction process occurring in fast‐atom bombardment (FAB) mass spectrometry have been studied, using the organic dyes rhodamine B and methylene blue as reference compounds. Our results indicate that transition metal chlorides have a strong influence on the suppression of the reduction process, while stannous chloride exhibits a remarkable suppression effect despite being a strong reducing agent. We suggest that the metal radicals generated in glycerol solution are responsible for these suppression effects. This phenomenou strongly supports the mechanism of hydrogen radical addition to the substrate molecules, postulated earlier as the cause of the reduction process. Co‐solvents in the matrix have also been found to suppress the reduction ions along with other matrix‐interfering ions. These studies help shed some light on the FAB ionization mechanism.
Non‐linear resonance conditions and their relationships to higher multipole fields in ion traps and quadrupole mass filters
Authors: Wang Yang 
Published: May 2005

AbstractDeviations of electrode shapes from pure quadrupole systems result in the superposition of higher multipole fields onto the quadrupole field. Non‐linear resonances are generated due to these higher multipole fields. These non‐linear resonances can be thought of as internal resonances, which must fulfil appropriate conditions. In this paper, general non‐linear resonance conditions for a time‐variable, three‐dimensional, non‐linear quadrupole system are derived, using previously described methods. The occurrence of resonances depends on the electrode shapes of the non‐linear quadrupole systems which control the weight factors of the higher multipole fields. With special electrode shapes, for example shapes with symmetry, the resonance effects are reduced. Different higher multipoles (for example, octopoles and dodecapoles) generate non‐linear resonances which fulfil different and/or the same resonance conditions. Each resonance condition can be described by resonance lines within the stable regions of the stability diagram. Resonant ion motion possesses the characteristic that groups of ion frequencies are simultaneously resonant. These properties are analyzed and corresponding results are given.
Analysing the complexation of amino acids and peptides with β‐cyciodextrin using electrospray ionization mass spectrometry
Authors: Camilleri Patrick , Haskins Neville J. , New Anthony P. , Saunders Martin R. 
Published: May 2005

AbstractThe formation of non‐covalently bound inclusion complexes between ß‐cyclodextrin and peptides containing aromatic acid residues has been confirmed by elcctrospray ionization mass spectrometry. This preliminary study has indicated that phenylalanine and tryptophan residues can form 1:1 complexes with ß‐cyclodextrin whereas no evidence for such a complex could be found for tyrosine residues. Bradykinin, which contains two phenylalanine residues, formed both 1:1 and 1:2 complexes.
Multiresidue pesticide analysis by ion‐trap mass spectrometry
Authors: Cairns Thomas , Chiu Kin S. , Navarro David , Siegmund Emil 
Published: May 2005

AbstractThe ion trap has been demonstrated to be able to detect and quantify 245 target pesticides extracted via the Luke method while providing concurrent confirmation of presence via full scan data at the sub‐ppm level. The precision and accuracy of the analytical approach was determined to be no greater than 15% relative standard deviation. A comparision study of over 100 incurred residues analyzed by the ion trap and gas chromatography with an array of element‐selective detectors has indicated that sample clean‐up will probably be necessary before quantification is acceptable for all target compounds. The data obtained using a combination of gas chromatography and mass spectrometry and presented for 250 target pesticides constitutes the basic information required to duplicate and extend the methodology.
High temperature mass spectrometric study of oxide systems and materials
Authors: Stolyarova V. L. 
Published: May 2005

AbstractHigh temperature mass spectrometry is a powerful tool for studying the vaporization processes and thermodyna‐mic properties of different types of materials such as glasses, ceramics and coatings. This paper illustrates the main advantages of this method for investigations of oxide systems and the approaches available to predict the relative volatilities as well as the thermodynamic properties of materials based on these systems.
Reactions in the mass spectrometry of 2,4,6‐N‐tetranitro‐N‐methylaniline (tetryl)
Authors: Yinon Jehuda , Zitrin Shmuel , Tamiri Tsippy 
Published: May 2005

AbstractDespite the presence of the ions at m/z 242 and m/z 243 in the electron ionization (EI) and chemical ionization (CI) mass spectra of tetryl, respectively, no such daughter ions were observed in the collision‐induced dissociation spectra of the M+· ion in EI and of the [M+H]+ ion in CI. This supports the thesis that these ions are formed through hydrolysis of tetryl to N‐methylpicramide in the ion source before ionization. It was found that the hydrolysis is considerably stronger under CI consitions, but can be minirnized in EI. The structure of the molecular ion at m/z 242 in the EI mass spectrum of N‐methylpicramide was found to be similar to that of the [MH‐NO2]+ ion in the CI mass spectrum of tetryl.
Quantification of abscisic acid using liquid chromatography/thermospray ionization tandem mass spectrometry for selected reaction monitoring
Authors: Okamoto Masahiko , Takahashi Ken‐ichi , Doi Tadashi 
Published: May 2005

AbstractA liquid chromatography/thermospray ionization tandem mass spectrometry (LC/TSP‐MS/MS) method was developed for the quantification of abscisic acid (ABA) in crude plant extracts without derivatization. By this technique interfering chemical background ions are eliminated and a detection limit for ABA olf 0.2 ng is achieved. Reproducibility for quantification is attained by parallel reaction monitoring of ABA and added ABA‐d6 used as an internal standard. The standard curve is linear over the range 200 pg to 10 ng of injected ABA. As examples of the application of the methodology, the quantification of ABA in some plant tissues is given.
Multiresidue pesticide analysis by ion‐trap technology: A clean‐up approach for mass spectral analysis
Authors: Cairns Thomas , Luke Milton A. , Chiu Kin S. , Navarro David , Siegmund Emil G. 
Published: May 2005

AbstractPrevious studies using the ion trap as a potential replacement for an array of element‐sensitive detectors indicated that only semi‐quantitative results at the 50–100 ppb range could be obtained for 245 pesticides because of interfering endogenous sample matrix compounds. The development of a new clean‐up procedure for a wide range of fruits and vegetables, specifically for use in an ion trap, has been undertaken to improve recoveries at the low ppm level to within analytically acceptable ranges (80–120%). This clean‐up involved the use of three solid‐phase extractions. The use of a C‐18 SepPak column removed the majority of hydrocarbon‐like molecules while the anion‐exchange column (QMA) removed all colored compounds and flavors, and finally the use of an aminopropyl column removed all sugars. Preliminary results from this study using 24 selected pesticides in four different sample matrices have indicated an acceptable improvement over previous results.
Simultaneous isolation of two different m/z ions in an ion‐trap mass spectrometer and their tandem mass spectra using filtered‐noise fields
Authors: Kenny Donald V. , Callahan Patrick J. , Gordon Sydney M. , Stiller Steven W. 
Published: May 2005

AbstractFor the first time, molecular ions from two different compounds have been simultaneously isolated in an ion‐trap mass spectrometer and their subsequent tandem mass spectra (MS/MS) obtained. Isolation was achieved by applying a filtered‐noise field (FNF) to the end‐caps of a FinniganMAT ion‐trap mass spectrometer (ITMS) using the Teledyne MEC/Hitachi HST‐1000 Enhancement Kit. The HST‐1000 generates a broadband waveform that would normally eject all ions from the trap. However, by setting notches in the waveform that correspond to certain resonant frequencies, individual masses can be isolated and stored in the trap without the need for the conventional DC voltage on the ring electrode. Using this FNF technique, the molecular ions of p‐dichlorobenzene (m/z 146) and 1,3,5‐trimethylbcnzene (m/z 120) were simultaneously isolated from a 42‐component mixture of volatile organic compounds. Each molecular ion was collisionally dissociated by applying a resonance excitation (‘tickle’) voltage from the HST‐1000, and the spectrum for each molecular ion was obtained by scanning the RF voltage to the ring electrode.
Quantitative analysis of low molecular weight compounds of biological interest by matrix‐assisted laser desorption ionization
Authors: Duncan Mark W. , Matanovic Gabrijela , Cerpa‐Poljak Anne 
Published: May 2005

AbstractInternal standards were used to demonstrate that matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry can be applied to the quantitative analysis of low molecular weight polar compounds. Three examples were tested: a standard curve for 3,4‐dihydroxyphenylalanine (DOPA) was prepared using a stable isotope analogue (i.e., [13C6]DOPA) as an internal standard; [2H16]‐acetylcholine was employed as an internal standard for the quantification of acetylcholine; and in the final example, the peptide Ac‐Ser‐Ile‐Arg‐His‐Tyr‐NH2 was used as an internal standard for the quantification of the peptide H‐Ser‐Ala‐Leu‐Arg‐His‐Tyr‐NH2. In each instance, straight line fits (r2>0.95) demonstrate that MALDI is a viable approach for the quantitative analysis of low molecular weight analytes.
Multiresidue analysis of sulfonamides using liquid chromatography with atmospheric pressure chemical ionization mass spectrometry
Authors: Doerge Daniel R. , Bajic Steve , Lowes Steve 
Published: May 2005

AbstractSulfonamide antibiotics are widely used to prevent bacterial infections in livestock, and residues are commonly found in milk and meat. This is of toxicological and regulatory concern because sulfamethazine produces thyroid tumors in rodents. Unadulterated milk was purified using solid‐phase extraction and six sulfonamides were added prior to analysis by liquid chromatography coupled to atmospheric pressure chemical ionization mass spectrometry. The mass spectra of all sulfonamides consisted exclusively of protonated molecules at low sampling cone voltage and, under these conditions, estimated detection limits were 0.05–0.5 ng, corresponding to 0.25–2.5 ppb in milk. The response curve for sulfamethazine was linear over a concentration range (1.25–20 ppb) that encompasses the regulatory level of interest in milk (10 ppb). Increasing the sampling cone voltage caused collision‐induced dissociation of sulfonamides that resulted in formation of ions that are diagnostic for the variable heterocyclic base and constant sulfanilyl portions of the molecule. At intermediate sampling cone voltages, multiple fragment ions were formed with reproducible intensity ratios. This process can be used to provide additional confirmation of target sulfonamides. Monitoring a common fragment ion formed at high sampling cone voltage permitted class‐specific multiresidue detection of the six sulfonamides with minimal losses in sensitivity. An analytical method is proposed for the detection, confirmation and quantification of sulfonamides and metabolites in milk with sensitivity equal to or greater than those obtained with less specific methods involving liquid chromatography with a UV detector. The relative simplicity of this technique and the availability of benchtop instrumentation suggests that routine screening and confirmation analyses of sulfonamide contaminants in milk is practicable.
Laser‐desorption Fourier‐transform mass spectrometry of triazines adsorbed on solid‐phase extraction membranes
Authors: Krier G. , Masselon C. , Muller J. F. , Nélieu S. , Einhorn J. 
Published: May 2005

AbstractUntil the present, analysis of aqueous solutions of atrazine has been conducted using a combination of liquid chromatography or gas chromatography with mass spectrometry, after a preconcentration step. We explore herein a new approach for studying support‐phase‐extracted atrazine and hydroxyatrazine samples. Solid‐phase extraction membranes are inserted directly into the cell of a Fourier‐transform mass spectrometer for analysis after laser ionization. It appears that atrazine and its metabolite have very different ionization processes. In the case of hydroxyatrazine, the [M + H]+ ion signal can be correlated to the concentration of the extracted solution. These encouraging results might open the route to a quantification method.
The Fourier‐transform laser microprobe mass spectrometer with external ion source as a tool for inorganic micro‐analysis
Authors: Struyf Herbert , Van Roy Wim , Van Vaeck Luc , Van Grieken René , Caravatti Pablo 
Published: May 2005

AbstractFocused‐laser ionization of solids and subsequent analysis of the generated ions by Fourier‐transform mass spectrometry is suitable for the characterization of inorganic and organic constituents. This paper describes selected examples to illustrate the capability of structural characterization of inorganic substances and the problems associated with the critical nature of the energy deposition phenomena which can complicate the use of the method. Selected examples from practical problem solving in material applications are presented to evidence the feasibility of local analysis by Fourier‐transform laser microprobe mass spectrometry.
Desorption—ionization of organic compounds studied by Fourier‐transform laser microprobe mass spectometry
Authors: Van Roy Wim , Struyf Herbert , Van Vaeck Luc , Gijbels Renaat , Caravatti Pablo 
Published: May 2005

AbstractThe recently developed FT LMMS with an external ion source has been applied to selected organic molecules. Some aspects of the ion formation processes from solids under focused laser irradiation at 266 nm were investigated. Specifically, the effect of laser energy and the time profile of ion production were studied. First, the generation of intact cations, fragments and thermal decomposition products from a quaternary ammonium salt were evaluated at distinct times after the laser pulse. The mass spectra of phenol red in its neutral and salt form were recorded under different conditions with respect to laser irradiation power density conditions and ion formation after the laser pulse. The results allow the refinement of previous concepts about ionization in LMMS.
A regiospecific cycloaddition: Successive reactions of ·CH2CH2OH with CH2O
Authors: Mourgues Philippe , Audier Henri Edouard , Hammerum Steen 
Published: May 2005

AbstractFour dominant reactions can be observed when the β‐distonic ion ·CH2CH2OH reacts in the cell of a Fourier‐transform ion cyclotron resonance spectrometer with a number of neutral molecules: protonation of the neutral molecule, ethylene radical‐cation transfer, hydride abstraction from the neutral molecule, and charge exchange. Among the ethylene transfer reactions, which can lead to a variety of other distonic ions, we have throroughly studied the reaction with formaldehyde. The reaction of a first molecule of CH2O yields ·CH2CH2OCH. The addition of a second one leads to 1,3‐dioxane which stabilizes by H· loss. This latter reaction is regiospecific.
Laser‐desorption Fourier‐transform mass spectrometry of [Ta6X12]X2·8H2O, X=C1, Br
Authors: Srzić Dunja , Tolić Ljiljana Paša , Martinović Suzana , Plavšic Dejan , Klasinc Leo 
Published: May 2005

AbstractThe gas phase of hexanuclear Ta clusters of type [Ta6X12]X2·8H2O, X=Cl, Br was investigated using laser‐desorption Fourier‐transform mass spectrometry. The [Ta6X12]Xions (m/z=1581 for X=Cl,m/z=2205 for X=Br) are the most characteristic peaks in their negative‐ion laser‐desorption mass spectra. Additional fragmentations observed are the result of loss of halogen and metal from [Ta6X12]X. Positive ions are observed only in the laser‐desorption mass spectra of [Ta6Br12]Br·8H2O.
Fast‐atom bombardment mass spectrometry of new polydentate schiff bases. 1. The case of variously substituted mono‐and bis‐salicylaldimine derivatives
Authors: Catinella S. , Traldi P. , Guerriero P. , Tamburini S. , Vigato P. A. 
Published: May 2005

AbstractThe mass spectrometric behaviour of ten variously substituted mono‐ and bis‐salicylaldimine derivatives has been studied by fast‐atom bombardment and metastable‐ion studies. In general, well detectable protonated molecules are present and fragmentation processes mainly related to aldimine chain cleavages are evidenced. Interesting cyclization reactions leading to particularly stable product ions are discussed.
Investigation of a series of neuroactive glycine dipeptide derivatives by fast‐atom bombardment and mass‐selected collision‐induced dissociation mass spectrometry
Authors: Henczi Maria , Weaver Donald F. , Borossay József 
Published: May 2005

AbstractGlycylglycine (glygly) and 40 related acetamide derivatives were synthesized and investigated by fast‐atom bombardment mass spectrometry. The protonated molecules were mass selected and their collision‐induced dissociations were analyzed by tandem mass spectrometry. The data obtained allow a fragmentation pattern to be established for these glygly analogues and permit detailed structural information on the main fragment ions to be ascertained.
Multinuclear ions of ferrocene [Fen(C5H5)n+1]+ (n = 2, 3 and 4) in the gas phase identified by mass spectrometry
Authors: Tu Ya‐Ping , Wu La‐Duo 
Published: May 2005

AbstractUnder methane chemical ionization conditions, multinuclear ions of ferrocene [Fen(C5H5)n+1]+ (n = 2, 3 and 4), resulting from the ion/molecule reactions in the gas phase, were detected by mass spectrometry. Structures for these ions are elucidated, according to their mass‐analyzed ion kinetic energy spectra, to be triple‐, quadrupole‐, and quintuple‐decker sandwiches, respectively, and the formation pathways for them are also discussed.
Collision‐induced dissociations of three C3H3O− isomers. An interesting hydride‐transfer reaction
Authors: Dua Suresh , Bowie John H. 
Published: May 2005

AbstractThe major collision‐induced fragmentation of CH2CC(H)(O−) occurs following hydride transfer to form CH2CH−CO which then loses carbon monoxide to form deprotonated ethene (C2H).