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1.
In the mass spectra of several transition metal chelates with diethyldithiocarbamate as a ligand, intense peaks are present which could be assigned to extraneous metal (particularly nickel) containing ions. Using an Au-Rh coated ion source, evidence was obtained for the occurrence of exchange reactions in the region of the filament assembly. 相似文献
2.
The Orbitrap: a new mass spectrometer 总被引:15,自引:0,他引:15
Hu Q Noll RJ Li H Makarov A Hardman M Graham Cooks R 《Journal of mass spectrometry : JMS》2005,40(4):430-443
3.
M. S. Kim T. G. Morgan E. E. Kingston F. M. Harris 《Journal of mass spectrometry : JMS》1983,18(12):582-586
Alkane ions generated by 70 eV electron ionization are irradiated in the source of a reversed geometry, double focusing mass spectrometer by 2.41 eV (514.5 nm) photons from an argon ion laser. The ions in the chamber are extracted, accelerated to 6 keV and spectra obtained by scanning the field of the magnet. The laser light is mechanically chopped and changes in the peak heights of the mass spectra resulting from photodissociation of ions in the ion chamber are recorded using a phase-sensitive detector to give what are referred to as photoinduced spectra. The peaks for the molecular ions of alkanes are large relative to other peaks in the photoinduced spectra, a situation which contrasts with that for the mass spectra. The relative photodissociation cross-sections of several alkanes, C6? C10, C12 and C16, have been measured and those of linear and branched [C10H22]+˙ ions are compared. Some of the characteristic features of the photoinduced spectra make the identification of the sample simpler than from mass spectra. The method is applied to the analysis of some alkane mixtures and its potential in analytical work discussed. 相似文献
4.
The processes of hydrogenation of a mixture of trifluoromethylfullerenes was studied in situ by means of positive-and negative-ion mass spectrometry. The effective addition of 1, 5, and 11 hydrogen atoms was revealed. The appearance energies of positive trifluoromethylfullerene ions C 60 (CF3) n + (n = 1–8) and C60(CF3) n H+ (n = 1, 3, 5, 7) were determined. 相似文献
5.
《Rapid communications in mass spectrometry : RCM》2018,32(9):677-685
Rationale
Recent trends towards miniature and portable quadrupole mass spectrometry (QMS) entail challenges in instrumental sensitivity, which is influenced by 3D fringe field effects on ion transmission in the Quadrupole Mass Filter (QMF). The relationship of these effects with the gap from the ion source to the QMF entrance (source gap) is significant and little explored. We examine transmission characteristics experimentally and use the results to test the predictive accuracy of a recently developed 3D QMF simulation model. The model is then applied to directly investigate optimal transmission m/z ranges across multiple source gaps.Methods
A portable single filter quadrupole mass spectrometer is used to analyse transmission characteristics across a range of common gases. We use an experimental approach originally proposed by Ehlert, enhanced with a novel method for absolute calibration of the transmission curve. Custom QMF simulation software employs the boundary element method (BEM) to compute accurate 3D electric fields. This is used to study the effects of the source gap on transmission efficiency.Results
Experimental findings confirm a centrally peaked transmission curve; simulations correctly predict the optimal transmission location (in m/z) and percentage, and extend the experimental trend. We compare several methods for determining fringe field length, demonstrating how the size of the physical source gap influences both the length and the intensity of the fringe field at the QMF entrance. A complex relationship with ion transmission is revealed in which different source gaps promote optimal transmission at differing m/z ranges.Conclusions
The presented results map the relationship between the source gap and transmission efficiency for the given instrument, using a simulation method transferrable to other setups. This is of importance to miniature and portable quadrupole mass spectrometers design for specific applications, for the first time enabling the source gap to be tailored for optimal transmission in the desired mass range.6.
The ionic species [C12H11]+ has been formed by ion-molecule reactions in benzene at high pressure (?0.5 Torr). This ion has been shown to be stable for at least 10?5 s and its structure has been inferred by a study of its unimolecular and collision induced fragmentations in both the first and second field free regions of the ZAB-2F mass spectrometer. 相似文献
7.
8.
1,2-Dithiolylium salts are thermolysed in the ion source of a mass spectrometer; some salts (group I) undergo thermolysis to give a stable dithiolyl radical where subsequent ionization gives rise to a mass spectrum in which the parent ion corresponds to the dithiolyl ion. The radical may be stabilized before ionization by expulsion of a hydrogen atom to form a neutral dithiole derivative, and then mass spectra exhibit abundant molecular ions corresponding to such dithiole derivatives.Other salts (group II) may expel a proton with formation of a carbene and subsequent dimerization to a tetrathiafulvalene.The thermolytic behaviour of 1,2-dithiolylium salts is compared with their electrochemical behaviour and several analogies are found. 相似文献
9.
Calculations have been carried out, using the Quasi-Equilibrium Theory of Mass Spectra to show that a decrease in penetration of the accelerating field intol the ion source of a mass spectrometer may significantly increase the number of primary daughter ions [A]+ produced from a molecular ion [M]+ in the source. The calculations show that this effect appears to be more important than the decay of [M]+ between source and collector in implementing an increase in [A]+/[M]+ at the collector with decreasing accelerator potential. 相似文献
10.
K. P. Jochum H.-J. Laue H. M. Seufert A. W. Hofmann 《Analytical and bioanalytical chemistry》1994,350(10-11):642-644
Isotope dilution measurements of geological reference materials are described using a newly developed multi-ion counting (MIC) system for a spark source mass spectrometer. Compared with the conventional photoplate detection system, there are considerably improved analytical features of the MIC system, especially the high sensitivity which leads to short measuring times of 1 min to 1 h for trace element analysis on the μg/g — ng/g level. 相似文献
11.
The coupling of a caesium ion source to a triple quadrupole mass spectrometer is described. The potential of this combination for examining thermally labile, non-volatile molecules, such as thiamine hydrochloride, is examined. Emphasis is placed on the advantages the various scanning modes of tandem mass spectrometry provide in ion structure elucidation and the investigation of desorption ionization mechanisms. Use of the caesium ion source for desorption of neutral molecules which are chemically ionized by an auxiliary gas is demonstrated. This procedure may be especially useful for examining non-volatile, non-ionic samples. 相似文献
12.
《Polyhedron》1986,5(3):703-706
Tetraalkylthiuram sulfides and sodium dialkyldithiocarbamates reacted with the metals (Fe, Ni, Cr and Cu) present in the ion source of a mass spectrometer to give their metal complexes. 相似文献
13.
The mass spectra of twelve 13C labeled compounds have been measured in order to investigate the fragmentation of the 1-heptyl iodide molecular ion. A mechanism is proposed for each reaction leading to the ions containing the iodine atom. The loss of olefin from the heptyl ion derived from the 1-heptyl iodide proceeds via extensive rearrangement of the linear ion. A non-linear intermediate structure obtained via protonated substituted cyclopropane is suggested to explain the major fragmentation reactions of the heptyl ion. 相似文献
14.
The radiative lifetimes of the 7p 2 P 3/2, 1/2 states of silver and the hyperfine structure of the 7p 2 P 3/2 state have been measured using pulsed laser excitation and direct observation of the induced fluorescence light decay. In order to excite this doublet, VUV radiation at 185 nm was applied, as generated by frequency tripling and anti-Stokes Raman shifting of the output of a Nd: YAG laser pumped dye laser. The lifetimes were found to be τ=255(20) ns and τ=285(25) ns for theJ=3/2 state andJ=1/2 state, respectively. The hyperfine structure of the 7p 2 P 3/2 state was measured by the quantum beat method. The magnetic dipole interaction constant for the107Ag isotope was found to bea=?4.5(2) MHZ. 相似文献
15.
Alfred O. Nier 《Journal of the American Society for Mass Spectrometry》1991,2(6):447-452
This article is a review of the events leading to the development of the double-focusing tandem mass spectrometer system, which is sometimes called the Johnson-Nier geometry. An essential feature of the geometry is that it eliminates second-order angular aberration, enhancing the sensitivity, without a loss in resolution. Flexibility in the choice of ion source and collector designs is assured because both are outside of regions of electric and magnetic fields. The vacuum housing permits high-temperature baking, ensuring ultrahigh vacuum conditions. Although introduced initially for the purpose of determining precise atomic masses, the design has found its greatest application in studies of structure of heavy molecules, making use of the high resolution to identify fragments. In many cases the composition of a molecule, or fragment, can be deduced from its exact mass by utilizing the known atomic masses of likely constituent atoms. 相似文献
16.
A simple but accurate potentiometric method for the estimations of mercaptans in 0.01M perchloric acid has been developed, based on their oxidation with 1-Chlorobenzotriazole. Quantitative oxidation solely to the disulphide stage is ensured by using critical amounts of methanol, acetonitrile and potassium iodide. Chloride, mercury(II) and copper(II) interfere. A back-titration procedure can also be used. The oxidation products have been identified. 相似文献
17.
Kidera M Takahashi K Enomoto S Mitsubori Y Goto A Yano Y 《European journal of mass spectrometry (Chichester, England)》2007,13(4):239-248
The ionization efficiency of an electron cyclotron resonance ion source (ECRIS) is generally high, and all elements can be fundamentally ionized by the high-temperature plasma. We focused our attention on the high potentiality of ECRIS as an ion source for mass spectrometers and attempted to customize the mass spectrometer equipped with an ECRIS. Precise measurements were performed by using an ECRIS that was specialized and customized for elemental analysis. By using the charge-state distribution and the isotope ratio, the problem of overlap such as that observed in the spectra of isobars could be solved without any significant improvement in the mass resolution. When the isotope anomaly (or serious mass discrimination effect) was not observed in ECR plasma, the system was found to be very effective for isotope analysis. In this paper, based on the spectrum (ion current as a function of an analyzing magnet current) results of low charged state distributions (2+, 3+, 4+, ...) of noble gases, we discuss the feasibility of an elemental analysis system employing an ECRIS, particularly for isotopic analysis. The high-performance isotopic analysis obtained for ECRIS mass spectrometer in this study suggests that it can be widely applied to several fields of scientific study that require elemental or isotopic analyses with high sensitivity. 相似文献
18.
The gas phase degradation reactions of the chemical warfare agent (CWA) simulant, dimethyl methylphosphonate (DMMP), with the hydroperoxide anion (HOO(-)) were investigated using a modified quadrupole ion trap mass spectrometer. The HOO(-) anion reacts readily with neutral DMMP forming two significant product ions at m/z 109 and m/z 123. The major reaction pathways correspond to (i) the nucleophilic substitution at carbon to form [CH(3)P(O)(OCH(3))O](-) (m/z 109) in a highly exothermic process and (ii) exothermic proton transfer. The branching ratios of the two reaction pathways, 89% and 11% respectively, indicate that the former reaction is significantly faster than the latter. This is in contrast to the trend for the methoxide anion with DMMP, where proton transfer dominates. The difference in the observed reactivities of the HOO(-) and CH(3)O(-) anions can be considered as evidence for an alpha-effect in the gas phase and is supported by electronic structure calculations at the B3LYP/aug-cc-pVTZ//B3LYP/6-31+G(d) level of theory that indicate the S(N)2(carbon) process has an activation energy 7.8 kJ mol(-1) lower for HOO(-) as compared to CH(3)O(-). A similar alpha-effect was calculated for nucleophilic addition-elimination at phosphorus, but this process--an important step in the perhydrolysis degradation of CWAs in solution--was not observed to occur with DMMP in the gas phase. A theoretical investigation revealed that all processes are energetically accessible with negative activation energies. However, comparison of the relative Arrhenius pre-exponential factors indicate that substitution at phosphorus is not kinetically competitive with respect to the S(N)2(carbon) and deprotonation processes. 相似文献
19.
An atomospheric-sampling glow-discharge ionization source has been interfaced with an ion-trap mass spectrometer. Under optimum conditions, the efficiency of ion injection is 1–5%. Several factors have a significant effect on the ion injection efficiency, including the voltages on the three-element lens system situated between the ion-source exit and the ion-trap entrance end-cap, the pressure of the bath gas present in the ion-trap vacuum housing, the nature of the bath gas and the amplitude of the radiofrequency voltage applied to the ring electrode during ion injection. Collision-induced dissociation (and electron detachment from anions) is also observed for some ions on injection, depending on the conditions. The most important experimental variables in determining the extent to which dissociation (or electron detachment) occurs are the nature of the bath gas, the bath gas presure and the radiofrequency voltage applied to the ring electrode during injection. These effects are illustrated with data obtained for polyatomic anions injected from the golw-discharge ion source. 相似文献
20.
A universal dual-electrospray (ESI) source is demonstrated on a quadrupole orthogonal-accelerated time-of-flight mass spectrometer (Q-ToF-MS) for both genomic and proteomic applications. This facile source modification enables internal calibration for consistent mass measurements by a mainstream MS platform and requires no mixing of analyte and calibrant prior to ion formation. In this report, the dual-sprayer is demonstrated in the negative-ion mode for internal calibration of polymerase chain reaction (PCR) amplicons generated from synthetic and genomic templates as well as a proteolytic digest of a naturally phosphorylated protein. For all PCR amplicons, experimentally determined average mass measurements are well within the instrument specifications of better than 0.01%. For the proteolytic fragments of the phosphoprotein, average mass errors of the isotopically resolved peptides are better than 10 ppm. 相似文献