AN ELECTROSTATIC ION TRAP FOR FOURIER TRANSFORM MASS
SPECTROMETRY Matt Lappin
Slide 2
OVERVIEW Motivation and background Fourier transform mass
spectrometry Electrostatic harmonic potential ion trap Design and
functionality Simulation Electronics and peripheral systems
Slide 3
MOTIVATION Saturns moon Titan has interesting properties
Methane cycle akin to Earths water cycle Organonitrogen rich
atmosphere and organic sand on the surface Electrostatic discharge
during rare sandstorms could provide activation energy for a
reaction to produce a basic amino acid Titan
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MOTIVATION Voyager and Cassini missions successful in probing
Titan Simulations of Titans atmosphere indicate that there is the
potential for life Many mission proposals to visit Titan in the
coming decade to search for life, and a critical instrument to
include would be a mass spectrometer
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MOTIVATION Space bound mass spectrometer must be: Small Low
power Precise over the desired mass range of 1-300 amu, as this is
where the chemicals necessary for life will be found The
electrostatic ion trap mass spectrometer proposed here meets these
requirements
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OVERVIEW Motivation and background Fourier transform mass
spectrometry Electrostatic harmonic potential ion trap Design and
functionality Simulation Electronics and peripheral systems
Slide 7
FOURIER TRANSFORM MS Mass spectrometry involves ionizing a
compound and measuring the abundance of ions produced at each mass
level FTMS detects oscillation in the time domain of these ions and
converts the time domain signal into a frequency spectrum
Oscillation is engineered so that the frequency is related to the
mass to charge ratio
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Magnetic field of strength B causes oscillation of ions with
frequency w = qB/m Detection plates provide time domain signal
Fourier transform provides frequency spectrum, which is
proportional to mass spectrum FOURIER TRANSFORM MS
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Most mass spectrometers detect ions (destructively) using an
electron multiplier. ICR detects ions from their image charge RF
Sweep to Accelerate the Ions Transient Ion Image Current Signal
Mass Spectrum
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ORBITRAP Electrostatic Complicated ion injection Tranverse
oscillation frequency related to m/z
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OVERVIEW Motivation and background Fourier transform mass
spectrometry Electrostatic harmonic potential ion trap Design and
functionality Simulation Electronics and peripheral systems
Slide 12
THE AUTORESONANT ION TRAP MS A.V. Ermakov and B.J. Hinch of
Rutgers used a similar trap in their autoresonant ion trap mass
spectrometer (ART-MS) Verified f is proportional to 1/(m/z) for
ions in the mass range 1-300 Da ART-MS uses resonant ejection, not
FT-MS, which requires RF sweep Ermakov, A.V.; Hinch, B.J. An
autoresonant ion trap mass spectrometer. Rev. Sci. Instrum. 81,
013107 (2010); doi: 10.1063/1.3276686
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THE ELECTROSTATIC HARMONIC POTENTIAL ION TRAP 1 kV, switched 3A
current source Held at a positive potential (5V) Can be pulsed to
10V Plate to protect macor filament clamp (0V) To detector (0V) for
image current detection The trap is 2.5 long and has a 1
diameter.
Stainless steel plates and alumina tubes/spacers: Kimball
Physics eV parts Assembled by Caltech CCE Insturment Shop Source
Trap Trapping plates(1kV) Signal plate CONSTRUCTION
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ELECTRONICS Vacuum
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ELECTRONICS
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SIGNAL DETECTION CIRCUITS Image Charge Detection Mass
Spectrometry: Pushing the Envelope with Sensitivity and Accuracy.
John W. Smith, Elizabeth E. Siegel, Joshua T. Maze, and Martin F.
Jarrold. Analytical Chemistry 2011 83 (3), 950-956 Image Credit:
Amptek, Inc.
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SUMMARY AND CONCLUSIONS Verified that the instrument should
work based on SIMION simulation Instrument assembly is in progress
Tests to come after the completion of assembly
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ACKNOWLEDGMENTS I would like to thank all members of the
Beauchamp group, especially Professor Beauchamp and graduate
student Daniel Thomas, for all of your help. I would also like to
thank Jeff Groseth in the CCE Electronics shop for helping with the
assembling the electronics for the spectrometer, and the CCE
Machine shop for help with machining and assembling parts of the
instrument.
