Ion Source Of Mass Spectrometer Research Articles

Hydroxylation of aromatic hydrocarbons in mass spectrometer ion sources under atmospheric pressure ionization and chemical ionization conditions

On montre que le benzene reagit avec l'air dans la source du spectrometre de masse pour donner du phenol ionise, du phenol protone et d'autres produits. La reaction a egalement lieu pour d'autres composes aromatiques dont le toluene, le xylene et le naphtalene

Metastable and collision induced fragmentation of some small cluster ions: Ar2+ Ar3+, ArN2+ and N4+

AbstractThe results of a study on collision induced dissociation and a search for metastable reactions of four gas phase ion‐molecule clusters, Ar2+, Ar3+, ArN2+ and N4+, are presented. The ionic clusters were formed in a high pressure mass spectrometer ion source which was cooled to enhance the association products. Subsequent fragmentations were studied using mass analyzed ion kinetic energy spectrometry. Decomposition pathways consistent with experimental collision induced dissociation peak shapes and ab initio potential diagrams are presented for the fragmentation of Ar2+ and N4+. Mechanisms for the collision induced dissociation of Ar3+ and ArN2+ are suggested. No metastable reactions for any of the cluster ions were observed. This result is in conflict with the results of Märk et al. using electron impact ionization of neutral van der Waals' clusters formed in a supersonic nozzle beam.

Evaluation of an electrostatically-collimated ion source in an isotopic-ratio mass spectrometer

Electrostatic collimation or focussing of the electron beam has been used in the ion source of an isotope-ratio mass spectrometer and its performance evaluated. The design details of the ion source and the mass spectrometer are given. The sensitivity is comparable to that in the magnetic collimation mode. The reproducibility of the sensitivity with electrostatic collimation for various filament assemblies is good. The output vs. pressure curves determined for electrostatic collimation, magnetic collimation and a combined electrostatic and magnetic collimation show good linearity. This combined field collimation is also found to give good sensitivity, comparable to the conventional source, but at a much lower electron emission. The electrostatically-collimated ion source was used for precision isotope ratio determinations of nitrogen gas samples collected from a cylinder. The relative internal standard deviation on a single sample ratio was better than 0.025%. The relative external standard deviation for repeated analysis of 19 samples drawn from the same cylinder over an 8-hour period was 0.08%. The advantages of using such an ion source are listed.

Crossedelectric-magnetic field electron-capture ion source

A method for thermalizing electrons is presented which involves the acceleration of electrons away from a hot filament with crossed electric-magnetic (EXB) fields in a magnetron configuration. It is shown that during a part of the resulting cycloidal path the electron velocity is significantly less than the initial velocity. The electron accelerates as it leaves the surface at a rate only slightly less than if there were no magnetic field, which prevents charge build-up at the surface. As the electron traverses the cycloid it is decelerated during the 2nd, 3rd and 4th quadrants, then re-accelerated as it approaches the end of the 4th quadrant to regain its original velocity. The minimum velocity occurs during the 4th quadrant, and corresponds to an electron temperature of 200–500°C for the electric and magnetic fields commonly encountered in the ion sources of magnetic sector mass spectrometers. An ion source modeled from this principle is presented.

Conditioning of ion sources for mass spectrometry of plasmas

Mass spectrometry is a useful diagnostic technique for monitoring plasma species and plasma–surface interactions. In order to maximize the sensitivity of measurements of hydrogen-fueled fusion plasmas or hydrogen-based discharge cleaning and etching plasmas, the ion sources of mass spectrometers are operated at or near the high pressure limit of 10−4 Torr (10−2 Pa). Such high ambient pressures of hydrogen give rise to high background levels of residual gases such as H2O, CO, and CH4, due to surface reactions on the ion source electrodes. For a commonly used ion source configuration, the residual gas production is a linear function of the ambient H2 pressure. Hydrogen conditioning can reduce the absolute residual gas levels. Steady state residual gas production is observed in a conditioned ion source, which is related to a balance of diffusion and sorption on the electrode surfaces.

New on-source miniature atomic FAB and alkali ion SIMS sources

Miniature atom and ion sources have been developed which mount directly onto the mass spectrometer ion source, within the vacuum chamber. The new sources are inexpensive to construct and require no external mounting flange. The use of an ion versus atom beam has been found to be unimportant, although the particle mass and impact energy have important effects on the intensity of quasimolecular ions, apparently due to the deposited momentum. A model of ionization of samples suspended in a liquid matrix and bombarded by energetic particles is proposed, in which ionization occurs in the “gas phase” by a charge-cascade mechanism similar to chemical ionization.

Experiments With The Combination Of A Micro Liquid Chromatograph And A Chemical Ionization Quadrupole Mass Spectrometer, Using A Capillary Interface For Direct Liquid Introduction : Some theoretical considerations concerning the evaporation of liquids from capillaries into vacuum

The total effluent from a micro liquid chromatograph, operating at a flow-rate of 8 μl/min, has been introduced into the ion source of a quadrupole mass spectrometer, which is used in the chemical ionization mode. The solvent vapour serves as the reactant gas. The interface is constructed from flexible fused-silica capillary tubing. The capillary extends into the ion source and the tip of the capillary is in thermal contact with the source via a copper block. Transfer of heat is necessary to support evaporation of the liquid. Calculations on the rate of evaporation indicate that the liquid vaporizes inside the capillary. It is shown that the rate of evaporation and the distance between the liquid front and the end of the capillary are strongly dependent on temperature.

On the mechanism of formation of rhenium compounds in a mass spectrometer with a rhenium filament

During mass spectrometric investigations of chlorination reactions of metal oxides, peaks corresponding to ReO 3Cl were detected in the background spectrum. The presence of HReÓ 4 was also revealed. The partial pressures of HReO 4 and ReO 3Cl are approximately proportional to the 1.5th power of the O 2 partial pressure. Formation of ReO 3Cl is due to the interaction of chlorine containing compounds with the hot rhenium filament of the mass spectrometer ion source.

Identification of polymers by mass spectrometry, 2. Polymers containing 1‐trifluoromethylvinylene, 1,4‐phenylene, and/or 2,5‐thiophenediyl units

AbstractPolymers containing 1‐trifluoromethylvinylene, 1,4‐phenylene, and/or 2,5‐thiophenediyl units (6a, b and 8a‐d), obtained by base‐free Wittig condensation reactions with phase transfer catalysts, were investigated combining direct evaporation in the ion source of a double focusing mass spectrometer with the “Linked‐Scan” metastable technique. This method could be shown to allow the unequivocal identification and differentiation of components in polymers up to high mass regions (m/z ≤ 3000). The degree of polycondensation up to 18 aromatic/heteroaromatic units in the chain was determined by mass chromatography, which correlated with the HPLC results. Terminal groups and sequence ions were characterized by comparison of metastable transitions of selected ions with model compounds. Detailed information on the polycondensation reaction was obtained. In addition to linear products, cyclic species with 3 to 18 arylene‐1‐trifluoromethylvinylene units were formed. The main fragmentations may be explained by sterical effects of both the α‐trifluoromethylstilbene moiety and the heteroaromatic analogues in the polymeric chains.

Mass spectra of polar organic compounds in aqueous solutions introduced into an inductively coupled plasma

AbstractAerosols of 1.5% aqueous solutions of glycine, glucose and tartaric acid were introduced into an atmospheric pressure inductively coupled plasma that served as the ion source of a quadrupole mass spectrometer. Protonated water cluster ions were the major ions observed during nebulization of deionized water. Protonated molecular ions were observed at count rates in the range 1000‐10000 counts s−1. Detection limits for [MH]+ ions of glycine, glucose and tartaric acid were 100, 2000 and 160 μg ml−1, respectively. Numerous fragment ions of the above compounds were observed. Both the number of fragment peaks and their count rates decreased as the forward power supplied to the plasma increased.

Parameters of high-frequency vacuum breakdown in a mass-spectrometer ion source

The electrical and optical characteristics of hf vacuum breakdown are experimentally investigated. It is shown that the breakdown current amplitude can reach 20 A with a voltage of up to 30 kV on the electrodes and a discharge duration of 20–25 nsec.

Lasers in solid state mass spectrometry

Abstract

Characterization of leukemic and normal white blood cells by Curie-point pyrolysis—mass spectrometry: I. Numerical evaluation of the results of a pilot study

A preliminary study was undertaken to determine the usefulness of Curie-point pyrolysis—mass spectrometry followed by computer analysis for character diseased white blood cells. White blood cells from normal, infected, polyeyrhemic and leukemic persons were pyrolyzed in front of the electron impact ion source of a quadrupole mass spectrometer on 510°C and 355°C Curie-point filaments. Visual inspection and computer assisted pattern analysis using the ARTHUR program revealed marked differences in the spectra among the different diagnostic categories. The 510°C pyrolysis—mass spectra from leukemic patients were found to have increased intensity at mass peaks related to RNA and DNA as well as decreased intensity at mass peaks related to choline containing phospholipids when compared to controls. The spectra from the polyeyrhemic patient and the two infected patients were found to have intermediate intensities for these two characteristic series. Pyrolysis at 355°C was found to enhance the differences seen in the 510°C pyrolysis spectra. Though the number of patients is too small to allow rigorous statistical analysis of the observed differences, numerical analysis of the spectra appears to hint at the possibility of using Curie-point pyrolysis—mass spectrometry as a diagnostic tool in discriminating different types of leukemias. An investigation with many more samples is needed to confirm these preliminary findings.

Capillary gas chromatographic-mass spectrometric determination of histamine in tuna fish causing scombroid poisoning

A documented case of “scombroid poisoning” is reported by confirming the presence of high histamine levels in fresh tuna fish tissues by gas chromatography-mass spectrometry. Histamine is confirmed by in situ trimethylsilylation of the tissue extract on a 12-m SP-2100 fused-silica capillary column connected directly to a mass spectrometer ion source operated in the positive ion chemical ionization mode using methane as reactant gas. The trimethylsilyl derivative of histamine is readily resolved by the high-resolution fused-silica capillary column and confirmed in the complex tissue extract by this very simple but specific procedure.

The gas phase reactivity of the dimethylchloronium ion with alkylbenzenes

The reactivity of the dimethylchloronium ion with a series of aromatic hydrocarbons has been studied in a high pressure mass spectrometer ion source using the technique of reactant ion monitoring. Benzene is unreactive but all others, from toluene to mesitylene, react by CH3+ transfer to yield σ-bonded complexes. The relative rate of reaction increases with increasing exothermicity in line with current theories of nucleophilic displacement reactions.

Negative ion-molecule reactions in formic acid.

Negative ion-molecule reaction has been investigated for formic acid utilizing a conventional type mass spectrometer. At elevated pressure negative ions react with neutral species in the ion source of mass spectrometer. It was found that a negative ion of mass 91 is produced by the reaction of the HCOO- ion with neutral formic acid asHCOO-+HCOOH→HCOOHCOOH-This reaction has two processes, i.e. a dissociative resonance electron capture (DREC) process and a high energy electron process. From the studies of HCOOH gas pressure dependence it was observed that the intensities of the HCOO- and HCOOHCOOH- ions in a DREC process increase with first and second order of the HCOOH gas pressure, whereas in a high energy electron process, they increase with fourth and seventh order of the pressure, respectively. The reaction rate constants of two processes were determined as (6.8 ±1.5) ×10-13 cc/molecule.sec for a DREC process and (1.3 ±0.5) ×10-37 cc3/molecule3·sec for a high energy electron process.

Rearrangement and hydrogen abstraction reactions of amine cation radicals: a gas-phase analogy to the Hofmann-Löffler-Freytag reaction

Low-energy molecular ions of gas-phase primary and secondary aliphatic amines undergo reciprocal NH/CH exchange of hydrogen atoms prior to fragmentation on the microsecond time-scale; the subsequent decomposition reactions are significantly different from those observed in the mass spectrometer ion source.

A photoionization study of hydrogen-bound clusters in a supersonic molecular beam

Hydrogen bonding of methanol, methanol- d, ethinol, and trifluoroethanol is investigated with a supersonic molecular beam as a sampling system for a photoionization quadrupole mass spectrometer. Monochromatized vacuum ultraviolet synchrotron radiation is used as the ionizing source. Cluster ions belonging to the series (ROII) n H + are detected when sampling up to 100-torr alcohol vapor with the molecular beam. No parent cluster molecular ions are detected. Experiments are described which exclude ion—molecule reactions in the mass spectrometer ion source as a possible origin of the cluster ions. Experimental evidence shows that nozzle temperature primarily influences the equilibrium distribution of clusters present in the nozzle source. From the dependences of relative cluster ion intensifies on nozzle source temperature, the heats of formation of oligomers of the alcohols are estimated. Cooperative hydrogen bonding is not detected, except for trifluoroethanol, while the trimer is found to be the most stable cluster.

Ion Source of Quadrupole Type Mass Spectrometer for Isotope Measurement of UF6

Ion Source of Quadrupole Type Mass Spectrometer for Isotope Measurement of UF₆

ChemInform Abstract: FAST RADICAL REACTIONS IN A MASS SPECTROMETER ION SOURCE: RADICAL ADDITION TO 7,7,8,8‐TETRACYANOQUINODIMETHANE

Chemischer InformationsdienstVolume 11, Issue 4 Preparative Organic Chemistry ChemInform Abstract: FAST RADICAL REACTIONS IN A MASS SPECTROMETER ION SOURCE: RADICAL ADDITION TO 7,7,8,8-TETRACYANOQUINODIMETHANE C. N. MCEWEN, C. N. MCEWENSearch for more papers by this authorM. A. RUDAT, M. A. RUDATSearch for more papers by this author C. N. MCEWEN, C. N. MCEWENSearch for more papers by this authorM. A. RUDAT, M. A. RUDATSearch for more papers by this author First published: January 29, 1980 https://doi.org/10.1002/chin.198004146AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume11, Issue4January 29, 1980 RelatedInformation