A new hybrid mass spectrometer for the investigation of ion/molecule reactions

Abstract

An RF-only quadruple collision cell, fitted with retardation and acceleration lenses, has been installed in a field-free region of a large-scale tandem mass spectrometer. This new arrangement has allowed decelerated, mass-selected ions (ca. 5 eV kinetic energy) to react with reagent gases and reaccelerated, mass-selected products (cu. 8 keV) to be subsequently identified by collisional activation mass spectrometry. The system was tested by looking at ion/molecule reactions of cyelobutanone molecular ions, previously studied by FTICR mass spectrometry Collisional activation (CA) mass spectrometry is a well-established technique for the characterization of fast-ion beams.' Isomeric ions are usually clearly distinguished because the technique provides not only fingerprint spectra of isomers, but also direct structural information, since simple, site-specific cleavages are frequently induced. CA mass spectrometry has more recently been implemented as the powerful neutralization-reionization (NR) technique' which, due to a higher energy deposition in the ions,3 gives rise to spectra which are even more structurally significant.In some instances, however, the interpretation of CA spectra is not straightforward and a further stage of mass spectrometric analysis, i.e. an MS/MS/MS (MS3) experiment is then r e q~i r e d .~ In these experiments, collision-induced fragments are mass-selected and subjected to a further collisional activation step. It must be recognized that such experiments may just displace the initial problem and other kinds of information are therefore required. The occurrence of post-collisional isomerization of ions may also introduce ambiguities; such processes have been reported recently for some sulfur-containing organic ions.The reactivity of ions towards neutral reagents provides another method for isomer differentiation. Such reactions are most easily performed in a chemical ionization (CI) source and, if the source is installed on a sector instrument, mass-selected products can be identified by high-energy collisional activation.6 It is, however, often difficult to identify unambiguously the reaction which leads to a specific product, since different ions and neutrals are present at the same time. This difficulty can be overcome by the use of Fourier-transform ion cyclotron resonance (FTICR) methodology which allows mass-selected ions to be collisionally stabilized, to react with appropriate reagents or to be collisionally dec~mposed.~ Note, however, that fragmentation of these precursor ions takes place at low kinetic energy.Other recent instrumentation allowing inter uliu the study of ion/molecule reactions has been recently reviewed by Cooks et aL8 Among the different approaches, results obtained by these authors using a home-built pentaquadrupole instrument appear quite Authors for correspondence promi~ing.~ Again, collision-induced dissociations of the ion/molecule products are obtained in the low kinetic energy regime.We describe in this paper the modification of a large sector mass spectrom...

Nitrosation of thiols and thioethers in the gas phase: A combined theoretical and experimental study

“…As far as the NO ϩ transfer process is concerned, the occurrence of slightly endothermic processes in our experimental setting is not unexpected since no thermalization step precedes the ion-molecule reaction processes and therefore hot ions can not be expelled from the ion beam [8].…”

“…The solid samples were introduced with a direct insertion probe, whereas the liquid samples were injected into the ion source via a heated septum inlet (180°C). This instrument has been modified with an rf-only quadrupole collision cell between E 2 and E 3 as reported elsewhere [8]. This modification allows the study of associative ion-molecule reactions of decelerated ions having about 5 eV kinetic energy.…”

Decarboxylation of metastable methyl benzoate molecular ions

“…The installation of the rf-only quadrupole collision cell (Q cell) inside the instrument between E 2 and E 3 has also been reported [6]. The products of dissociation of metastable ions within the quadrupole (without collision gas) can be recorded by scanning the field of the second magnet; this kind of spectra will be referred to in the text as "resolved" MIKE spectra.…”

Characterization of New Sulfide Ions (C2S3•+) from Ethenedithione by Ion−Molecule Reactions

“…In its hybrid "sectors-quadrupole-sectors" configuration, the AutoSpec 6F mass spectrometer allows also the study of ion-molecule reactions at near thermal energies. 4,5 Such ion-molecule reactions may complement in several instances the collisional activation data. We have therefore investigated the behavior of the C 2 S 3 •+ ions toward several neutral reagents including dimethyl disulfide (DMDS), nitric oxide, acetonitrile, and methyl isocyanide.…”

“…4,5 The performed MS experiments include collisional activation (CA) at high (8 keV) and low (ca. 20-30 eV) translational energies of the incident ion beams, neutralization-reionization (NR) experiments, and ion-molecule reactions at near-thermal (∼5 eV) energies.…”