PNNL-13501 - Pacific Northwest National Laboratory

Study Control Number: PN00037/1444
Dynamics Studies of Surface-Induced Dissociation Processes
Anil K. Shukla, Jean H. Futrell
The use of mass spectrometry for analyses of high mass ions is an area of increasing emphasis in analytical research due
to the importance of high mass ions to such research areas as proteomics. However, the successful use of mass
spectrometry to analyze high mass ions requires the development of new approaches and techniques. The purpose of this
project is to gain a fundamental understanding of one such technique—surface collision-induced dissociation.
Project Description
Ion-surface collisions have long been used for
characterizing and modifying surfaces. In recent years,
with the introduction of new soft ionization techniques of
electrospray and matrix assisted laser desorption, widely
used techniques of collision-induced dissociation (ionneutral
gas collisions) do not appear to be efficient in
dissociating very high mass ions. Several laboratories
have demonstrated that ion-surface collisions can be used
more efficiently than gas-phase collisions to dissociate
impacting ions of high masses. Unfortunately, the basic
understanding of the ion-surface collision phenomenon,
especially of processes leading to dissociation of
polyatomic ions of even low masses is not well
understood. Questions remain regarding the role of the
surface and its characteristics, ion characteristics, and
physical phenomena, such as image-charge interaction
potential, that must be answered before the technique can
be universally applied on a routine basis. We are,
therefore, building a prototype system where we will use
well-defined ion beams (mass, energy, intensity,
divergence, surface impact angle) and surfaces (tailored,
self-assembled monolayers) for collisions and to monitor
the mass, scattering, and energy of product ions from their
reactions. We hope to determine, not only the necessary
parameters, but also the mechanisms of energy transfer
and dissociation phenomena in ion-surface collisions.
Results and Accomplishments
The unique instrument under development for the
proposed research on the dynamics of surface-induced
dissociation processes is shown schematically in Figure 1.
The design of the instrument has been finalized and
construction and assembly of the components inside the
collision chamber are nearing completion. The first-stage
mass spectrometer (JEOL, GCmate) for use as the mass
and energy analyzed ion beam source for surface-induced
8 FY 2000 Laboratory Directed Research and Development Annual Report
dissociation experiments in the collision chamber was
tested using a set of ions that are of interest for further
studies. It is now being modified to interface with the
collision chamber, and necessary ion optics to decelerate
the ion beam to the desired lower collision energy have
been constructed. An energy analyzer and quadrupole
mass filter will be mounted on a rotator for angle- and
energy-distribution measurements of secondary ions.
Necessary electronics for the control of the experiment
and data collection are being acquired.
Ion Source
Source Slit
Alpha Slit
Magnet
DC Quadrupole Lenses
Beta Slit
Energy Analyzer
Quadrupole Mass Filter
Rotation Range
Electric Sector
Figure 1. Ion-surface collision instrument
Surface
Electron Multiplier
Conversion Dynode
Tandem Mass Spectrometry of Nitrobenzyl Alcohols
The performance of the first-stage mass spectrometer was
evaluated for stability and ion beam characteristics using
isomers of nitrobenzyl alcohol. Using linked scans to
determine their dissociation pathways, we observed that
the nitro-nitrite rearrangement leading to the loss of
nitrous oxide from the molecular ion is almost completely
suppressed in ortho-nitrobenzyl alcohol. In meta- and
para-nitrobenzyl alcohol, there is some evidence for this
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Collector Slit
Einzel Lens
Deceleration Lenses