bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow injection Thermospray® mass spectrometry for the automated analysis of potential agricultural chemicals
Authors: Hayward Mark J. , Snodgrass Joseph T. , Thomson Michael L.
Published: May 2005

Flow injection Thermospray mass spectrometry (TSP‐MS) has been developed and utilized for molecular weight and structural confirmation for thousands of potential new agricultural chemicals. Initially, it was necessary to find TSP conditions which provide an optimal compromise between providing reproducible, informative mass spectra and being sufficiently universal and rugged for a wide variety of compound types. By acquiring both positive‐ and negative‐ion spectra for each sample, the range of compounds that can be analyzed successfully is greatly expanded. The method developed is sufficiently universal that flow injection TSP‐MS now provides the required information in approximately 70% of the mass spectrometric structural confirmations performed at the Agricultural Research Division of American Cyanamid. The success in using flow injection TSP‐MS led to the development of instrumentation to fully automate these analyses. An IBM PC/AT® compatible computer is used to control sample delivery, data acquisition and data output. The PC performs the functions of both terminal and operator for a Finnigan® TSQ 46 triple quadrupole mass spectrometer and its Data General Nova® 4X data system, while simultaneously controlling a Micromeritics® 725 (Alcott®) autosampler and its Reodyne® 8126 pneumatically actuated 6‐port sampling valve. Furthermore, the need to document analyses in a manner that is consistent with Good Laboratory Practices has led to automated documentation for the instrument analysis log, as well as for the headers of the electronic data files and the printed spectral output. The new automated flow injection TSP‐MS system described here was constructed using only commercially available equipment and has notably improved efficiency by reducing the instrument time required to record spectra and by minimizing analyst intervention.
The confirmation and quantitation of LSD in urine using gas chromatography/mass spectrometry
Authors: Bukowski N. , Eaton A. N.
Published: May 2005

Confirmation and quantitation of LSD, as its trimethyI silyI derivative, is carried out using a commercial gas chromatography/mass spectrometry system. The method uses 4 times less sample than previous methods, extends column life by reducing the amount of derivatizing agent used and can detect and quantify LSD at the 10 pg mL−1 level.
Matrix‐assisted laser desorption time‐of‐flight mass spectrometry of oligonucleotides using 3‐hydroxypicolinic acid as an ultraviolet‐sensitive matrix
Authors: Wu Kuang Jen , Steding Anna , Becker Christopher H.
Published: May 2005

Matrix‐assisted laser desorption time‐of‐flight mass spectrometry has been used to produce quasimolecular ion signals from underivatized mixed‐base single‐stranded DNA oligomers ranging from 10 to 67 nucleotides in length. These results were obtained with a new matrix material, 3‐hydroxypicolinic acid (3‐hydroxypyridine‐2‐carboxylic acid)which showed significant improvement over many previously reported matrices studied in terms of mass range available, signal‐to‐noise ratio, and the ability to analyze mixed base oligomers. The desorption and simultaneous ionization was by pulsed laser light at 10 to 50 mJ/cm2, studied at 266, 308, and 355 nm. Spectra taken at 266 nm provided the smallest amounts of doubly charged and dimer ions—characteristics desirable for DNA sequencing by this technology. Negative‐ion spectra were uniformly superior to positive‐ion spectra. This new matrix also is quite effective for molecular weight determinations of peptides and proteins in both positive‐ and negative‐ion modes.
Laser mass spectrometry of dibenzodioxin, dibenzofuran and two isomers of dichlorodibenzodioxins: Selective ionization
Authors: Weickhardt C. , Zimmermann R. , Boesl U. , Schlag E. W.
Published: May 2005

Laser‐induced mass spectra and UV spectra of dibenzodioxin, dibenzofuran, and two isomers of dichlorodibenzodioxin measured by means of resonance‐enhanced multiphoton ionization in a supersonic molecular beam are presented. The UV spectra show sharp bands and large wavelength shifts both being specific to the number and position of the chlorine atoms. The mass spectra are free of fragments. Therefore the prerequisites for isomer selective ionization and detection of these substances are fulfilled. This encourages further work on polychlorinated dibenzodioxins and dibenzofurans.
Observation of intact (heme‐bound) myoglobin by electrospray ionization on a double‐focusing mass spectrometer
Authors: Loo Joseph A. , Giordani Anne B. , Muenster Helmut
Published: May 2005

A noncovalently bound complex, the heme‐apomyoglobin protein system (Mr 17 568), was detected using electrospray ionization on a double‐focusing mass spectrometer with an array detector. The kilovolt energy conditions used for ion transmission and focusing did not cause significant amounts of fragmentation of the weakly‐bound complex. With a high‐performance array detector, femtomolar sensitivity was achieved for myoglobin in water.
Enlarging the stability domain for ion trap tandem mass spectrometry (MS/MS)
Authors: Gordon D. B. , Woods M. D.
Published: May 2005

The low‐ mass cut‐off in ion trap tandem mass spectrometry (MS/MS) is significantly improved by employing a sawtooth driving function on the ring electrode in place of the usual sinusoidal AC potential. The theory is explained with examples involving both the ‘tickle’ and ‘boundary‐effect’ MS/MS methods.
Chemical archaeology of kava, a potent brew
Authors: Hocart Charles H. , Fankhauser Barry , Buckle David W.
Published: May 2005

Kava lactones, which are present in the intoxicating Pacific Island drink, kava, have now been detected in a number of archaeological artefacts using selected‐ion monitoring techniques in conjunction with gas chromatography/electron impact‐mass spectrometry. Thus it is now possible to link unequivocally kava drinking, a major aspect of the ceremonial culture of many Pacific societies, to the archaeological record. In addition, a new variation of the kava lactone skeleton was tentatively identified in the form of 7,8‐dihydro‐5,6‐dehydrokawain and 7,8‐dihydro‐5,6‐dehydromethysticin.
Charge‐transfer ionspray liquid chromatography/mass spectrometry analyses of fullerenes and related compounds from flame‐generated materials
Authors: Anacleto J. F. , Quilliam M. A. , Boyd R. K. , Howard J. B. , Lafleur A. L. , Yadav T.
Published: May 2005

A flame‐generated, fullerene‐rich material (J. B. Howard et al., Nature 352, 139 (1991)) has been characterized by liquid chromatography coupled on‐line to ionspray mass spectrometry. Charge‐transfer complexation, using a post‐column addition of either an electron donor or acceptor, was utilized as a pre‐ionization technique. Analyses in the positive‐ion mode showed that the thermally metastable constituents of the flame‐generated material, tentatively identified previously (J. F. Anacleto et al., Rapid Commun. Mass Spectrom. 6, 214 (1992)) as fullerene isomers on the basis of atmospheric pressure chemical ionization muss spectrometry, yielded mass spectra consistent with their identification as fullerene adducts with highly uiuaturated moieties CnH2n−4 with n = 5, 6, and 7. The molecular radical cations of these adduct species were susceptible to facile fragmentation yielding the molecular ions of the corresponding fullerenes. The negative‐ion mode experiments failed to provide any information regarding the identity of these metastable constituents.
Charge‐remote fragmentation of bile acids derivatized with amino‐sulphonic acids
Authors: Griffiths W. J. , Zhang J. , Sjövall J.
Published: May 2005

Negative‐ion fast‐atom bombardment mass spectra of free and conjugated bile acids are dominated by [M  H]− pseudomolecularions. Collision‐induced dissociations of these pseudomolecular ions give charge‐remote fragmentation patterns which are useful for structural identification. Taurine (2‐aminoethanesulrtionic acid)‐conjugated bile acids have a high cross‐section for charge‐remote fragmentation, and give the most informative and intense spectra among the naturally occurring bile acids. In the present study, collision‐induced dissociation spectra of bile acids derivatized with different aliphatic and aromatic aminosulphonates, and with 2‐amlnoethyl hydrogen sulphate have been compared. All show charge‐remote fragmentation patterns. Determination of the intensities of the fragment ions shows that the highest sensitivity is usually obtained with aromatic aininosulpho‐nate derivatives.
Dilithiated fragments of a monolithiated precursor ion? Unraveling linked scan spectra at constant B/E using labeled lithium ions
Authors: Kiplinger Jeffrey P.
Published: May 2005

Liquid secondary‐ion mass spectra of the macrocyclic immunosuppressant rapamycin, ionized from a matrix containing lithium chloride, show intense [M + Li]+ peaks and little or no [M + 2Li − H]+. Linked scanning, at constant B/E, of the [M + Li]+ ion proved difficult to interpret, so a labeling experiment using 6LiCl was performed. Several prominent fragments were observed to contain two lithium ions, and precursor ion scans (constant B2/E) confirmed that these were derived from a metastable [M + 2Li − H]+ precursor. Due to poor precursor‐ion resolution in fragment‐ion scans at constant B/E, mono‐ and dilithiated precursors separated by only 6 u may produce fragments observed in each other's spectra. We find that use of labeled 6LiCl quickly and simply alleviates interpretation problems associated with this effect.
Three structural types of carbon cluster anions and the magic numbers
Authors: Jiao Charles Q. , Phelps Donald K. , Lee Samuel , Huang Yongqing , Freiser Ben S.
Published: May 2005

The distribution of negative carbon clusters, C, is studied in the size range from 4 to 100 atoms using a Smalley compact supersonic source interfaced to a Fourier transform mass spectrometer. Tht mass spectrum of the anion clusters shows three regions which, based on earlier work, can be assigned to three different types of structures: chain, monocyclic and fullerene. The boundaries observed for the three regions in the mass spectrum suggest that the transition from chain to cyclic structure occurs between C and C, and the one from cyclic structure to fullerene occurs in the region of C to C. Magic numbers in the cyclic cluster region are found to be 17, 21, 25, 29 and 33 (n = 4m + l), and in the fullerene region, 60 and 74. Water can react with carbon clusters in the supersonic source to form hydrogenation products followed by electron attachment to give CnH− and CnH (for even n smaller than about 22). With argon as the target gas, only small C (n < 14, except n = 4) are observed to undergo low energy collision‐induced dissociation (CID) yielding mainly C. While CID of CnH− gives C, no product was observed during CID of CnH.
Desorption–ionization and in‐flight fragmentation of monoalkali‐glycine adducts: Plasma‐desorption mass spectrometry and Ab initio calculations
Authors: Bouchonnet Stéphane , Flament Jean Pierre , Hoppilliard Yannik
Published: May 2005

Interpretation of 252Cf plasma‐desorption mass spectra of glycine and alkali salt mixtures is correlated to thermochemical values. The interpretation of direct spectra is based on a model considering competitive fragmentations among the ionic bonds involved in the crystalline structure; the desorption yield of Li, Na, K, Rb and Cs alkali‐glycine adduct ions is shown to depend upon the relative lattice energies of the different salts bound in the solid mixture. Ab initio calculations were performed at the 6‐31G*//3‐21G level to evaluate the dissociation energies associated with the in‐flight decomplexation reactions GlyCat+ → Gly + Cat+ (1) for Cat+ = Li+, Na+ and K+ whether we consider that the GlyCal+ desorbed species enter the field‐free area in their ‘preformed geometry’ or that they rearrange during the acceleration step. The experimental metastable transition rates associated with these reactions were determined to be in good agreement with the theoretical values for both GlyCat+ geometries under consideration. We calculated the cation affinities of glycine to be 271 kJ/mol, 188kJ/mol and 127kJ/mol for Li+, Na+ and K+, respectively. The fragmentation of GlyCat+ species into immonium ions, GlyCat+ → [H2N–CH2]+ + CO + HOCat (2), is also experimentally and theoretically investigated. The competition between reactions (1) and (2) is favourable to (2) for Cat+ = H+ and to (1) for Cat+ = Li+, Na+ and K+. From both competitive reactions, the comparison between theoretical values and experimental observations allows one to estimate the average internal energy of the GIyCat+ desorbed species at about 300 kJ/mol in the field‐free area of the mass spectrometer.
Selective elimination of low‐molecular‐weight ions in MALDI‐TOF mass spectrometry using a bipolar pulsed electrostatic particle guide
Authors: Just Craig L. , Hanson Curtiss D.
Published: May 2005

This study addresses a problem inherent in the use of microchannel plates as detectors for matrix‐assisted laser desorption/ionization. We have developed a unique new method of ion transport using fast bipolar pulsing of an electrostatic particle guide to provide ion deflection and enhanced ion transmission. This mode of operation effectively eliminates the intense low‐mass component of the spectrum which normally saturates microchannel ‐plate detectors, while at the same time transporting the higher‐mass component with high efficiency. Enhancement of the resulting signal‐to‐noise ratio has been achieved.
Molecular ion beam method of isotopic analysis: Effect of error propagation, a case study with Li2BO
Authors: Datta B. P. , Khodade P. S. , Parab A. R. , Goyal A. H. , Chitambar S. A. , Jain H. C.
Published: May 2005

The isotopic analysis of boron has been carried out using different pairs of isotopic Li2BO ions as monitors. The precision of the mass spectromctric measurements of different molecular abundance ratios is roughly the same. However, the values of the 10B/11B abundance ratio calculated from the experimental ratios of different pairs of isotopic molecular ions show large variations. These variations are shown to be a logical consequence of the calculation step which leads to the magnification of measurement errors to different extents for different peak ratios. Similar arguments would apply for the isotopic analysis of any element employing the molecular ion beam technique. The effect of isotopic fractionation on the molecular abundances is also discussed. The important implication of the present investigation is that it sets the guidelines for selecting suitable monitor molecules to avoid such errors.
Analysis of taxol and related taxanes from taxus canadensis using liquid chromatography combined with mass spectrometry or tandem mass spectrometry
Authors: Blay P. K. S. , Thibault P. , Thiberge N. , Kiecken B. , Lebrun A. , Mercure C.
Published: May 2005

A liquid chromatography/mass spectrormetry (LC/MS) method using nebulizer‐assisted electrospray (ionspray) is described for the analysis of taxol and related taxane analogs in plant extracts from Taxus canadensis. The method used a reverse‐phase liquid chromatography gradient elution which was entirely compatible with the operation of ionspray ionization. Abundant protonated molecules with limited fragmentation were obtained using this ionization technique, and provided adequate sensitivity for monitoring taxol in crude resin extracts. The LC/MS method was evaluated for the analysis of taxol present at levels of 0.2% in resin extracts. Using selected‐ion monitoring, the method provided detection limits of 50 ng/mL. In addition, other taxane analogs were identified in crude resin extracts using liquid chromatography combined with tandem mass spectrometry. Parent‐ion scans for a fragment ion characteristic of the taxane nucleus provided the necessary selectivity and sensitivity for the identification of potentially active diterpenes in complex extracts.
Pyrolysis/gas chromatography/mass spectrometry of lignin from paper‐industry effluents decolorized by trametes versicolor
Authors: Terrón María C. , Martín Carmen , Manzanares Paloma , Galletti Guido C. , González Aldo E.
Published: May 2005

The pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) results after fungal treatment of paper‐industry effluents suggested a decrease of the relative amounts of lignin pyrolysis products and of the syringyl/guaiacyl ratio, in addition to some oxidation rate of the C3‐alkyl chain in lignin units. The results obtained pointed to the potential of PY/GC/MS for monitoring the extent of fungal modification of lignins by biological systems based on the use of Trametes versicolor.
Mass spectrometric discrimination between per‐O‐acetylated aldopentoses applied to an oligosaccharide
Authors: Blok‐Tip Leonore , Heerma Wigger , Haverkamp Johan
Published: May 2005

Unimolecular decomposition spectra of oxonium ions from peracetylated pentoses can be used for identification purposes. The fast‐atom bombardment mass spectra of an oligosaccharide with a pentose residue at the non‐reducing terminus also contain this oxonium ion, which allows identification of this monosaccharide residue by a tandem mass spectrometry experiment. The applicability of this method is demonstrated using a xylopentaose.
A new reduction process in fast‐atom bombardment mass spectrometry: Transformation of an azido group into an amino group
Authors: Aubagnac J.‐L. , Gilles I. , Gosselin G. , Perigaud C. , Labataille P. , Imbach J.‐L.
Published: May 2005

A new example of the reduction phenomenon often observed in fast‐atom bombardment mass spectrometry is described, involving the transformation of an azido group into an amino group. This reaction, noticeable with glycerol as a matrix, does not occur with m‐nitrobenzylalcohol.
Taxoid side‐chain structure determination by electrospray ionization tandem mass spectrometry
Authors: Bitsch Francis , Shackleton Cedric H. L. , Ma Wenwen , Park Gary , Nieder Matthew
Published: May 2005

A method to elucidate the side‐chain structure of novel taxoids was developed through use of electrospray ionization tandem mass Spectrometry. The intact side‐chain fragments produced by source fragmentation in the atmosphere‐to‐vacuum interface were further dissociated in the collision cell of a triple quadrupole mass spectrometer. The distinctive collisionally induced dissociation mass spectra were remarkably informative and gave detailed information on the side‐chain functionalities. This technique proved valuable in the characterization of new taxoids produced by yew‐tree cell cultures.
The influence of collisional cooling on boundary‐activated decomposition in an ion‐trap mass spectrometer
Authors: March Raymond E. , Londry Frank A. , Fontana Stefano , Catinella Silvia , Traldi Pietro
Published: May 2005

When the working point of a precursor ion confined within a quadrupole ion trap is moved to the vicinity of a boundary of the stability diagram, fragmentation of the precursor ion can be induced by virtue of energy gained from the radio‐frequency trapping field. This behaviour is known as the ‘border effect’. When the isolated precursor ion is subjected to a cooling period of variable duration, in the presence of helium buffer gas and prior to experiencing the ‘border effect’, a high degree of control of the fragmentation pattern is achieved. The cooling period causes decreases in both ion kinetic energy and ion axial excursions. From this preliminary study, it is suggested that the deposition of internal energy during the ‘border effect’ can be varied by changing the duration of the cooling period. In addition to a degree of control of internal energy deposition, the amount of energy which can be deposited in this manner, though unknown, appears to exceed those energy levels achievable with resonance excitation and the ‘border effect’ without collisional cooling, in that an additional fragmentation channel is accessed.
Matrix‐assisted laser desorption ionization of oligonucleotides with various matrices
Authors: Tang K. , Allman S. L. , Chen C. H.
Published: May 2005

Ferulic acid, 3‐hydroxypicolinic acid (3‐HPA), and 2,5‐dihydroxybenzoic acid (2,5‐DHB) were used as matrices in MALDI of various oligonucleotides. It was found that 2,5‐DHB is an excellent matrix for polydeoxyribothymi‐dylic acid. A poly‐T oligonucleotidc with a size of 130 bases was successfully detected. 3‐HPA was found to be a good matrix for MALDI of homo‐oligomeric deoxynucleotides as well as those containing four different bases. Parent ions of pd(A)60, d(T)100 d(G)40, and d(C)40 were observed, and a mixed‐base oligonucleotide of 150‐mer was also detected. Polymer ions of poly‐A as large as 420‐mer were measured; however, the efficiency for detecting poly‐T with 3‐HPA as a matrix was slightly worse than when 2,5‐DHB was used. Comparisons of three matrices for various oligonucleotides is also presented.
Characterization of alkyl‐ and aryl‐tins by means of electrospray mass spectrometry
Authors: Jones Tammy L. , Betowski Leon D.
Published: May 2005

The organotins, mainly the trialkyltins and triphenyltins, have a widespread application as fungicides, anti‐fouling coatings for porous and non‐porous surfaces, herbicides, insecticides, and generic biocides. Traditional environmental monitoring methods can only give limited speciation of the organometallics. The speciation of a wide variety of alkyl‐ and aryl‐tin isomers using liquid chromatography coupled with mass spectrometry under positive‐ionization conditions is reported. Detection of the organotins was enhanced by the use of acetic acid in the methanol mobile phase. There were unexpected high‐mass ions with multiple tin‐isotope patterns present in many of the spectra. These high‐mass species were possibly attributable to tin polymers, whose presence has been observed by others using X‐ray methods.
Application of electrospray ionization to the observation of higher fullerene anions
Authors: Fujimaki Susumu , Kudaka Ichiro , Sato Tetsuya , Hiraoka Kenzo , Shinohara Hisanori , Saito Yahachi , Nojima Kazutetsu
Published: May 2005

Negative‐ion electrospray mass spectrcmetry for the detection of higher fullerene anions is discussed. The fullerenes were reduced in dimethoxyethane/aromatic solvent using NaK amalgam and analyzed by electrospray ionization mass spectrometry using a double‐focusing mass spectrometer. All the C ions (n = 2k, and k is an integer) could be detected up to n = 102 except for 60 < n < 70 and n = 72. The detection efficiency of C76 is found to be considerably lower than that for C78, probably because the C ion reacts further in solution and is converted to undetectable reaction products. In addition to the fullerene anions, large peaks due to methoxy‐substituted fullerene anions, Cn(OCH3), are observed. The intensities of these ions grow with time.
Low‐energy ion/molecule products from collisions with ammonia
Authors: Morris Michael , Thibault Pierre , Boyd Robert K.
Published: May 2005

Multiple clustering of ammonia molecules to triply protonated bovine insulin B chain has been observed in a novel collision cell incorporated as part of a triple quadrupole mass spectrometer. The nature of the phenomenon was examined as a function of both the collision energy and the collision gas thickness in the cell. Increased clustering was observed with higher collision‐gas thickness and lower collision energy. Initial experiments indicate that the number of ammonia molecules clustering to the precursor ion may be dependent on the number of available acidic sites.
Ion‐trap mass spectrometry with an inductively coupled plasma source
Authors: Barinaga Charles J. , Koppenaal David W. , McLuckey Scott A.
Published: May 2005

A new mass spectrometry technique using an inductively coupled plasma (ICP) ionization source and an ion‐trap mass spectrometer (ITMS) detector is described and evaluated for elemental and isotopic analysis. Initial results obtained with the ICP‐ITMS technique include sub‐ppb detection of bare ions for, most elements, complete destruction of typical polyatomic matrix ions (e.g., CIO+, ArO+, and ArCl+), and effective neutralization of strong Ar+ ion currents. The latter effects allow observation of clearer mass spectra at m/z < 80 and potentially improved detection of ‘problem’ elements in ICP‐MS (e.g., K, Ca, V, Fe, As, and Se). Formation of poly‐oxide and ‐hydroxide ions of metals with high oxide bond strengths were observed and require system modifications to alleviate.
Determination of substituent effects on the proton affinities of natural nucleosides by the kinetic method
Authors: Liguori Angelo , Napoli Anna , Sindona Giovanni , Cooks R. G.
Published: May 2005

The kinetics of the unimolecular dissociations of proton‐bound dimers produced by fast‐atom bombardment from nucleosides and reference amines enables the evaluation of the proton affinities (PA) of ribonucleosides. The PAs of cytosine, guanosine, adenosine, uridine and deoxyuridine have been thus determined. These values and those already available for the corresponding DNA homologues allow the evaluation of the effect of the hydroxyl group in position 2′ of the sugar moiety, which lowers the PAs of RNA nucleosides by 0.6–1 kcal/mol, and of the methyl group in position 5 of the thymine ring which enhances the basicity of deoxythymidine over deoxyuridine by 0.6 kcal/mol.
First Fourier‐transform ion cyclotron resonance signals of very highly charged atomic ions
Authors: Beiersdorfer P. , Beck B. , Elliott S. , Marrs R. , Schweikhard L.
Published: May 2005

We report on the first application of Fourier‐transform ion cyclotron resonance mass spectrometry to the very highly charged ions produced in the high‐energy electron beam ion trap (SuperEBIT) at the Lawrence Livermore National Laboratory. Initial results are described, and spectra are presented from ions as highly charged as Cs53+.
Probing conformational changes in some proteins by positive‐ion electrospray mass spectrometry
Authors: Hamdan M. , Curcuruto O.
Published: May 2005

Charge‐state distributions in the positive‐ion electrospray (ES+) mass spectra of some proteins are monitored at various temperatures of the ion source. The observed shifts in charge‐state profiles favouring higher charge‐states are linked to heat‐induced conformations cited by other research groups. To gain more insight into the origin of the observed shifts, a number of measurements were also performed at different flow rates of the electrospray drying gas, on both aqueous and organic solutions of protein. The flow rate of the drying gas was found to influence the relative intensities of high charge‐states induced by heat or organic solvents to a small extent, but it did not produce substantial shifts in the charge‐state distributions observed in room temperatures ES+ mass spectra of aqueous solutions.
Observation of large multimers in the electrospray ionization mass spectrometry of peptides
Authors: Busman Mark , Knapp Daniel R. , Schey Kevin L. , Smith Richard
Published: May 2005

Large multimeric ions were detected from electrospray ionization (ESI) mass spectrometry of peptides, using a quadrupole mass spectrometer of standard mass range. Multimers, up to heptamers, were seen for angiotensin I; and multimers, up to pentamers, were observed for renin substrate. The appearance of the multimeric species could be controlled by manipulation of sampling conditions in the ESI interface. The relevance of the observation of large multimers to proposed mechanisms of ESI is discussed. Implications of the observation of large multimers to efforts to deduce higher order structure of biomolecules from ESI mass spectrometric experiments are also noted.
Charge‐remote fragmentation of sulphated and glucuronidated bile acids and their 2‐aminoethanesulphonic acid derivatives
Authors: Griffiths William J. , Zhang Jie , Sjövall Jan
Published: May 2005

Negative‐ion fast‐atom bombardment mass spectra of bile acids show prominent [M—H]− pseudomolecular ions, and few fragment ions. Collision‐induced dissociation of such pseudomolecular ions gives charge‐remote fragmentations which are useful in structural identifications. It has been shown that bile acids conjugated with taurine (2‐aminoethanesulphonic acid) give more intense and informative collision‐induced dissociation spectra than unconjugated bile acids. In this laboratory, a procedure for the aminosulphation of biological samples, for analysis by tandem mass spectrometry, has been developed. In the present study, a comparison has been made between the collision‐induced dissociation spectra of a series of sulphated and glucuronidated bile acids and their 2‐aminoethanesulphonic acid derivatives.
Liquid chromatography/mass spectrometry analyses of small molecules using electrospray and fast‐atom bombardment ionization
Authors: Reiser Robert W. , Fogiel Arthur J.
Published: May 2005

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

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

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

The conformation of the rigid isomer pair of cis‐ and trans‐3‐pinanones was investigated using methane, isobutane, and ammonia chemical ionization (CI) mass spectrometry as a tool to study the dependence of the mass spectrometric fragmentation patterns. The methane and the isobutane CI mass spectra of the cis and trans isomers were found to be different enough to permit the differentiation of the isomers. Each isomer exhibited distinctive fragmentation paths. The isobutane mass spectra of the cis isomer was dominated by the loss of H2O from the pseudo‐molecular ion, whereas the loss of C2H4O was the predominant fragment for the trans isomer. Molecular modeling and quantum‐chemical computations were used to calculate the conformers of lowest energy for the two isomers. The theoretical calculations were then used to explain the differences observed in the chemical ionization mass spectra.

In addition, high resolution mass spectrometry measurements, deuterium labeling experiments and energy calculations of the hypothetical transition states and ionized species were helpful and were used to propose mechanisms for the CI mass spectral fragmentation.
Characterization of new diimines of carbon suboxide by tandem mass spectrometry
Authors: Flammang Robert , Laurent Sophie , Barbieux‐Flammang Monique , Van Haverbeke Yves , Wentrup Curt
Published: May 2005

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

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

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

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

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

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

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

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

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

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

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

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

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

Translational energy spectra have been obtained for single‐electron capture by 8 keV Ar4+ ions in He, Ne and Ar. The spectra for He and Ne targets display eight well‐resolved peaks, the majority of which correspond to capture involving a rearrangement of the electron core configuration. By contrast, the five channels observed in the spectrum for the Ar target are all associated with core‐conserved electron‐capture processes. One pronounced peak in the spectra for He and Ne cannot be explained on the basis of capture from the ground 3P or metastable 1D and 1S states of the Ar4+ ions, and appears to originate from capture by Ar4+ in the hitherto unidentified metastable 5S0‐state at ∼ 7.5 eV above the ground state. All observed channels are spin‐conserved.