PNNL-13501 - Pacific Northwest National Laboratory

Study Control Number: PN99069/1397
Surface-Induced Dissociation of Polyatomic Cations
Anil K. Shukla, Julia Laskin, Eduard V. Denisov, Jean H. Futrell
Mass spectrometry for analyses of high mass ions is an area of increasing emphasis in analytical research because of the
importance of high mass ions to such research areas as proteomics. Ion cyclotron resonance mass spectrometers have
particular relevance to these analyses because of their unique capability to collect all the ions up to high masses at
extremely high resolution and quantitatively monitor reactions over the time range from microseconds to seconds. The
purpose of this project is to develop a novel optimized surface collision activation ion cyclotron resonance prototype that
will provide information on the reactivity and thermochemistry of high mass ions.
Project Description
A number of studies have shown the applicability of ionsurface
collisions leading to the dissociation of ions as an
efficient and attractive alternative to normally used ionneutral
gas collisions in analysis and structural
characterizations. Most of these studies have used sector
and quadrupole mass analyzers for this purpose, where
scattering losses and slower dissociation (~10 to
50 microseconds) contribute significant uncertainties in
the intensity measurements. Ion cyclotron resonance
mass spectrometers have the unique capability of
collecting all the ions up to very high masses at extremely
high resolution and quantitatively monitoring reactions
over the time range from microseconds to seconds. Since
the resolution in ion cyclotron resonance is directly
related to the background pressure, gas phase collisions
drop the effective mass resolution by several orders of
magnitude. This complication is bypassed with surface
rather than neutral collisions. Development of an
optimized ion cyclotron resonance surface collision
activation instrument, therefore, enables the determination
of complete activation and dissociation processes
including step-wise ion dissociation. We propose to build
an ion cyclotron resonance system using a 7-tesla
superconducting magnet with capabilities to introduce
mass-selected, energy-relaxed ion beams inside the ion
cyclotron resonance cell, where it can be reacted with a
well-defined surface to determine all fragmentation
processes simultaneously. We have developed
procedures to determine kinetic energy of ions and model
ion intensity distributions to estimate internal energy
distributions of all fragment ions. We hope that a
combination of all these techniques, if successful, will
provide us additional information on the reactivity and
thermochemistry of high mass ions.
Results and Accomplishments
The instrumentation for Fourier transform ion-cyclotron
resonance mass spectrometer using a 7-tesla
superconducting magnet was developed. The vacuum
chambers, electrospray source with a hydrodynamic ion
funnel, mass selection by radio frequency direct current
quadrupole, thermalization of ions in a radio frequencyonly
quadrupole, and necessary ion optics for the transfer
of ions into the cell inside the magnetic field have been
constructed. A load-lock system for the introduction and
easy replacement of a surface is under construction. The
system is being tested under vacuum for ion formation,
their transmission characteristics, and various parameters
to optimize experimental conditions. A schematic view
of the instrument is shown in Figure 1. The data system
for the instrument and necessary electronics for the radio
frequency and direct current supplies have been built, and
delivery of the 7-tesla magnet is anticipated in October
2000.
Figure 1. A schematic view of the instrument with 7-tesla
superconducting magnet
Analytical and Physical Chemistry 23