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.
A simple procedure has been developed to select ions in a Fourier transform ion cyclotron resonance (FT-ICR) ion trap. This procedure involves the use of correlated single- and swept-frequency excitation fields to eject unwanted ions from the FT-ICR ion trap. Correlation with the effective cyclotron frequency of the ions which are to be selected leads to optimization of the parameters controlling...
Molecular orbital calculations (Becke3LYP/3-21G(d)) indicate that the distonic acylium ions CH 2 CH 2 CH 2 CO + and CH 2 CH 2 CO + are localized σ-radicals with a spin density of 0.95 e and 0.92 e at the terminal methylene carbon, respectively. Most of the positive charge (+0.88) is localized on the carbonyl carbon. The radical...
A combination of the pick-up technique and high resolution mass spectrometric methods have been used to generate and study doubly charged cluster ions of the form [Sr(CH 3 CH 2 CH 2 OH) n ] 2+ . As a result of charge transfer, no ions are observed for n = 1 and the parent ion distribution rises to a sharp maximum at n = 4, suggesting a first solvation...
UV irradiation of a T-rich hexadeoxynucleotide, d(TATTAT), produced four photoproducts, which can be cleanly separated from starting material and each other by reverse-phase HPLC. The structures of the photoproducts were investigated by using 1D 1 H-NMR, which allows the nature, but not the location, of the photoproduct between adjoining Ts or between T and A to be determined. Both fast...
This work describes the implementation of the particle-in-cell simulation method with Monte-Carlo Langevin and hard sphere ion-neutral collisions in our two dimensional Cartesian and cylindrical coordinate system codes. The particle-in-cell method efficiently and accurately solves complex dynamics involving many interacting particles. In our case many means simulation runs with thousands to...
Carbon cluster cations from C +5 to C +19 were generated by laser ablation/ionization of graphite in the Fourier-transform ICR ion trapping mass spectrometer, and dissociated by excimer laser pulses with photon energy 6.43 eV. Branching ratios and relative apparent cross-sections were determined. Further mechanistic and thermochemical information was sought by several...
Fourier transform ion cyclotron resonance mass spectrometry has been used to examine the reactions of Si(CH 3 ) +3 with EGDN and PETN. In addition, the reactions of Si(CH 3 ) +3 with EGDN and PETN was examined in a magnetic sector mass spectrometer. No adduct formation was observed with either EGDN or PETN in the Fourier transform ion cyclotron resonance...
The internal energy content of CF + (X 1 Σ + ,v) ions and its time evolution have been probed using the monitor ion technique in a triple FTICR spectrometer. Vibrationally excited CF + ions were produced by electron impact on CF 3 H. Charge transfer reactions on NO, C 2 H 5 I, CH 3 I and CS 2 were used in this study. The experimental...
Coenzyme A (CoA) thioesters play a central role in many biochemical reactions, and methods for sensitive identification of these compounds are important for studies of cellular processes. The direct analysis of intact long-chain fatty acyl CoA esters was investigated using matrix assisted laser desorption time-of-flight and electrospray ionization mass spectrometry. Both techniques resulted in the...
Unimolecular dissociations of diclofop acid and three of its esters were studied using electron capture negative-ion mass spectrometry, to determine to what extent the gas-phase chemistry correlated with transformation products reported for the herbicide in soils and microbial biofilms. Electron capture of the trimethylsilyl (TMS) and pentafluorobenzyl (PFB) esters along with H + abstraction...
Multiply-charged cations derived from the positive ion electrospray of the oligonucleotide 5 -d(CTTAGCGCTAAG)-3 were subjected to reactions with the (M - CF 3 ) - and (M - F ) - anions derived from perfluoro-1,3-dimethylcyclohexane in a quadrupole ion trap. Both single strand ions and double strand ions formed from the self-complementary oligonucleotide were...
Our high resolution ion mobility apparatus has been modified by attaching an electrospray source to perform measurements for biological molecules. While the greater resolving power permits the resolution of more conformations for BPTI and cytochrome c, the resolved features are generally much broader than expected for a single rigid conformation. A major advantage of the new experimental configuration...
Heats of formation calculated with the G2(MP2), G2(MP2,SVP), CBS-Q, and CBS-q methods for 46 aliphatic nitrogen- and oxygen-containing molecules and ions with up to three carbon atoms are compared with experimental results and with each other. The values obtained theoretically for aliphatic amine radical cations and immonium ions are uniformly higher than the experimental values, in a few cases by...
An understanding of the chemistry of the ion-molecule reactions occurring in an ion mobility system is a prerequisite to fully exploiting the potential of Ion Mobility Spectrometry for the detection and monitoring of pollutants. Whilst it is commonly thought that clustering around a proton is the dominant process occurring in the positive ion mode, previous studies have shown that much more complex...
The gas phase basicity of butyramide (2a), caproamide (3a), isobutyramide (5a), pivalamide (6a), cyclopentanecarboxamide (7a), cyclohexanecarboxamide (8a), their N-methyl derivatives 2b-8b and their N,N-dimethyl derivatives 2c-8c have been determined by the deprotonation method using FT-ICR spectrometry (2a-8a only) and by the kinetic method observing the metastable decomposition of proton-bound...
The usefulness of the determination of kinetic energy release (KER) distributions instead of single KER values is not widely known, though the KER distributions provide more detailed and accurate information about the studied process. To confirm this fact the KER distribution has been determined from the peak shape of the metastable peak corresponding to the charge separation reaction HONO 2...
The MD + ions of a variety of amino acids and small peptides have been prepared using CD 4 and (CD 3 ) 2 CO as chemical ionization reagents. Using tandem mass spectrometry the fragmentation reactions of these MD + ions have been studied, both those occurring unimolecularly on the metastable ion time scale (CD 4 CI) and those occurring following collisional...
This work describes the application of negative ion chemical ionization, optimized for dissociative electron attachment (DEA), to location of unknown trace chlorinated compounds in complex gas chromatograms by selected ion recording (SIR) of m/z 35 and 37. The DEA-SIR technique is compared with other GC detectors, including the electron capture detector, electrolytic conductivity detector, the atomic...
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.