The observation of metastable transitions in a double-focussing mass spectrometer using a linked scan of the accelerating and electric-sector voltages

Weston, A. F.; Jennings, Keith R.; Evans, S.; Elliott, R. M.

doi:10.1016/0020-7381(76)80158-1

Cited by 86 publications

(16 citation statements)

References 6 publications

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“…The reactions of metastable ions in the field-free region immediately preceding the first electric analyzer (the first FFR) were studied by simultaneous scanning of the first electric and magnetic sector fields, keeping B/E = constant ("linked scan"). 5 The rate constants of the fragmentation reactions that are examined with the MIKE technique are roughly an order of magnitude lower than those examined with linked scanning.…”

Section: Mass Spectrometrymentioning

confidence: 93%

The Unimolecular Reactions of Ionized Methylacetamides

Jensen

Hammerum

2004

Eur J Mass Spectrom (Chichester)

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The formation of CH 5 N +• ions by expulsion of CO from ionized acetamide was described by Drewello et al. 1 in 1987. They identified the product ion as • CH 2 NH 3 + , the α-distonic isomer of the methylamine molecular ion. The two higher homologs, ionized N-methylacetamide and N,N-dimethylacetamide, react analogously, expelling CO with formation of the α-distonic isomers of the dimethylamine and trimethylamine radical cations. 2 In the ion source, the [M -CO] +• ions are formed in only low yield, but CO expulsion is the major reaction of the metastable methylacetamide molecular ions and, alongside loss of ketene, of the dimethylacetamide molecular ions. The formation of the α-distonic isomers rather than the amine molecular ions is slightly surprising, inasmuch as the α-distonic isomers of secondary and tertiary amines are less stable than their conventional molecular ion counterparts; 2 when produced by decarbonylation the ions will be formed with a polar molecule in close proximity, which could potentially promote catalyzed isomerization. 3 We have, therefore, examined the distonic ions formed from the methylacetamides in the mass spectrometer ion source as well as the reactions of the metastable precursor ions, making use of mass analyzed ion kinetic energy (MIKE) spectrometry, deuterium labeling and ab initio quantum chemistry. Methods Mass spectrometryThe unimolecular ionic gas-phase reactions were studied with a Jeol HX/HX110A mass spectrometer operated in three-sector mode (EBE), with which it is possible to examine the dissociation reactions that take place in the ion source and in the field-free region (FFR) in front of each sector. The energy of the ionizing electrons was 70 eV and the accelerating voltage was 10 kV; the ion source sample pressure was between 1 and 2 × 10 -6 torr.The reactions of metastable ions were examined with mass analyzed ion kinetic energy (MIKE) spectrometry, 4 which was used to monitor those reactions of mass-selected ions that take place in the field-free region after the magnetic analyzer (the third FFR). The reactions of metastable ions in the field-free region immediately preceding the first electric analyzer (the first FFR) were studied by simultaneous scanning of the first electric and magnetic sector fields, keeping B/E = constant ("linked scan"). 5 The rate constants of the fragmentation reactions that are examined with the MIKE technique are roughly an order of magnitude lower than those examined with linked scanning.A specific product ion formed by reaction in the first field-free region can be transmitted through the magnet by selecting the values of B and E that would allow transmission in a B/E = constant scan. The spontaneous and collisioninduced reactions of this ion in the third field-free region can then be examined by scanning the second electric sector (a MIKE scan). The reactions of the product ions formed when metastable amide molecular ions dissociate in the first fieldfree region were examined in this manner.Collision-induced dissociation (CID) 6 spe...

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Section: Mass Spectrometrymentioning

confidence: 93%

The Unimolecular Reactions of Ionized Methylacetamides

Jensen

Hammerum

2004

Eur J Mass Spectrom (Chichester)

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“…This Barber-Elliott "defocusing" technique revealed signals of metastable ions associated with a selected product ion. 48 The product and precursor ion scans are illustrated in the 2D full data domain, i.e. the set of all ion intensities connecting product and precursor ions as shown in Figure 2.…”

Section: Types Of Scansmentioning

confidence: 99%

Direct analysis of complex mixtures by mass spectrometry

Cooks

Jarmusch

Wleklinski

2015

International Journal of Mass Spectrometry

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Mixture analysis can provide information on individual components if the sample is first subjected to chromatographic separation. Two critical capabilities, soft ionization and the ability to mass-select and then dissociate ions of a particular m/z, coalesced in 1975, allowing direct analysis of complex mixtures by mass spectrometry. Chemical ionization was used as the soft ionization method and mass-analysis used the ion kinetic energy spectrometer (MIKES). Soft molecular ionization produces a set of ions that are structural surrogates of the neutral molecules; they can be mass-selected and allowed to spontaneously dissociate (i.e. as metastable ions) or fragmented upon energy transfer e.g. in the course of collision-induced dissociation (CID). The second stage of mass analysis provides information about the atomic connectivity in the precursor ion and by implication in the original molecule. This review focuses on the development of complex mixture analysis by mass spectrometry and allied topics. Discussion of the activation techniques associated with (collision-induced dissociation, surface-induced dissociation and metastable ion dissociation) emphasizes the importance of energy transfer phenomena and the internal energies distributions of ions to explain the observed mass spectra. The translational to internal energy transfer in collisions is readily accessed in the MIKES where the second stage mass analyzer is a kinetic energy/charge analyzer. Collisions in the keV range can also be used to change ion the charge state via the processes of charge exchange, electron stripping, or charge inversion. New ionization sources for analysis of non-volatile compounds that were introduced during the time period (1975-1990) of this review included secondary ion mass spectrometry, plasma desorption and field ionization and they are briefly discussed. Several types of scans were developed to rapidly access information of the individual components, including chemically specific scans (e.g. neutral loss scans of mass 30 for nitro compounds).

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“…The attainable resolution was much higher than in MIKES, but ion source detuning was still a problem. The characteristics of their new method were later investigated in collaboration with Keith Jennings (Weston et al, ). Simultaneously and independently, Mike Lacey and Colin Macdonald at CSIRO in Canberra had developed (Lacey & Macdonald, ) this same technique.…”

Section: My Gateway To Mass Spectrometry: the Swansea Connectionmentioning

confidence: 99%