The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Low energy methyl glycolate radical cations , 1, abundantly lose HCO , yielding protonated methyl formate H-C(OH)OCH +3 . Tandem mass spectrometry based experiments on 2 H, 13 C and 18 O labelled isotopologues show that this loss is largely (about 75%) atom specific. Analysis of the atom connectivity in the product ions indicates that the reaction proceeds...
A Bi + ion emitter has been developed and studied which is modeled on the silica gel matrices that have been used to produce ions from a variety of elements such as Pb, Ag and Te for isotope ratio measurements. Studies with this model system demonstrate that this ion emitter is a liquid glass and that ion emission originates from the surface of the liquid glass. The large difference in ion...
Precise determinations of the isotopic compositions of molybdenum, tellurium, tin and tungsten were obtained utilizing an inductively coupled plasma (ICP) source magnetic sector mass spectrometer equipped with multiple collectors. The results of this study are comparable to those measured by conventional and negative thermal ionization mass spectrometry (TIMS and NTIMS) and the values recommended...
Results and experience are presented for a method of fractionation free measurements in thermal ionization mass spectrometery. The method can be used not only on multi-collector mass spectrometers, where the isotopes of interest can be measured simultaneously, but also on a thermal ionization quadrupole mass spectrometer using a special scanning and heating sequence. The total evaporation method...
A novel ceramic-like material has been produced and tested which has the property of emitting perrhenate anions for several thousand hours when heated in vacuum to temperatures between 1073 and 1173 K. Previously reported versions of this material were inferior to the material discussed here, probably owing to loss of perrhenate from reduction within the host matrix. The earlier materials, as well...
Glow discharge mass spectrometry (GDMS) has been evaluated for its ability to measure isotope ratios in solids. Isotope ratios were measured for B, Cu, Sr, Ag, Sb, Re and Pb in concentrations ranging from 15 ppm to pure metal. External precision of better than 0.03% has been achieved for isotope ratios measured using pure solid elemental samples; typical precision is better than 0.1% for elements...
The third-order trajectories of charged particles in crossed electric and magnetic fields have been calculated, and the results are expressed in the form of a transfer matrix. The differential equations are solved algebraically using the symbolic computation program Mathematica. The relativistic effects are taken into account. The transfer matrix elements can be expressed in both algebraic and...
Negative primary ions have an advantage for SIMS measurements when positive secondary ions are being observed, because they gain energy from the secondary ion accelerating voltage. Having both Cs + and I - ions available from the same ion source enables maximum bombarding energy to be obtained for both positive and negative secondary ion spectra without interrupting the vacuum.
An isotope dilution-thermal ionization mass spectrometry method for the determination of parts-per-million levels of iron in zirconium is required for precise, accurate analyses in studies of the effects of iron on the irradiation deformation of nuclear alloys. A two-stage purification procedure was developed to avoid the signal suppression and interference caused by the zirconium matrix. After...
Infrared multiphoton absorption is introduced as a method of direct heating of gas phase molecules prior to field ionization. This approach appears to be a very effective way to increase fragmentation following field ionization of the vibrationally excited molecules. Comparison is made with the method of electrical heating of the emitter which results in an indirect heating of the molecules prior...
Argides, dimers, and doubly charged metal ions were investigated as possible species to use for elemental quantification in glow discharge mass spectrometry. These species showed a behavior similar to that of the metal ion when discharge power was varied, and similar to that of the metal atom when discharge pressure was varied. Quantification of several National Institute of Standards and Technology...
From the inception of analytical mass spectrometry numerous efforts have been undertaken to minimize artifacts in mass spectra. While double-focusing techniques brought about significant progress in that interference signals in ion-source mass spectra can now be excluded, for MS/MS studies several kinds of artifacts exist when only two sectors are used in MS n (n 2) experiments. Tandem...
Simulations and experiments on the motion of collections of ions show that impulsive excitation, applied in the axial direction, forces ions into coherent motion with characteristic secular frequencies. A version of the ion trap simulation program, itsim, which accounts for the effects of ion/molecule collisions, is applied to show that this motion is remarkably stable even in the presence of bath...
Virtually all Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry experiments are based on ion confinement in a Penning trap: namely, a spatially homogeneous static magnetic field B, and a three-dimensional axial (along B) quadrupolar electrostatic trapping potential. In addition, it is desirable to provide an alternating azimuthal (i.e. in a plane perpendicular to B) spatially uniform...
An abundance sensitivity of < 10 ppb has been achieved with the redesigned retarding potential quadrupole (RPQ-II) on the Finnigan MAT 262 test instrument at the Finnigan MAT applications laboratory, and on the instrument installed at the Open University. The Open University instrument is equipped with a deflection unit after the RPQ-II to select a Faraday collector or a secondary electron multiplier...
Three-dimensional ion trajectories in Wien filters were calculated in a third-order approximation. The results were expressed as a total transfer matrix with aberration coefficients. Two-dimensional image shapes at an image plane were simulated by using these results. Focusing properties of the systems with a homogeneous Wien filter and a stigmatic Wien filter were investigated as examples. Third-order...
The development of a tandem mass spectrometric method, involving reactive collisions in a quadrupole collision cell, to study the reactions of metal ions with organic substrates is reported. This approach is evaluated by studying the reactions of singly charged transition metal ions with cyclopentene. The transition metal ions Sc + through Cu + were produced by fast atom bombardment...
The intent of this study was to determine the fraction of soluble uranium attributable to the Rocky Flats Plant (RFP) operations which is recoverable from waters and suspended sediments drawn from ponds on site at RFP. Samples were collected from late 1992 through 1993. Thermal ionization mass spectrometry (TIMS) measurement techniques indicate that the water samples contain both naturally occurring...
Proton-bound clusters of acetic acid and mixed clusters of acetic acid and water evaporate neutral dimers of acetic acid. This attribute is shared with liquid acetic acid. Clusters are considered to bridge the gap between the gas phase and condensed phases. The evaporation of dimers begins to be observed with the heptamer. Cluster binding energies to monomer and dimer units were deduced from kinetic...
A matrix-assisted laser desorption ionization (MALDI) source has been coupled to the ion chromatography instrument developed at UCSB. The source produces a strong, consistent signal for several hours on a single sample. In this paper we report the application of this method to a series of poly(ethylene glycol) (PEG) polymers cationized by sodium. Data have been taken for Na + PEG5 to Na...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.