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| Fourier Transform Ion Cyclotron Resonance Mass Spectrometry |
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FTICR-MS: Fourier transform ion cyclotron
resonance mass spectrometry. An MS
configuration that detects signals on metal
plates from electrical currents produced by
ion oscillations. The hallmark of FT-MS is
its high resolution; 1-2 ppm mass accuracy or
lower can be achieved. A drawback is the long
cycle time required for acquisition of MS and
particularly MS/MS spectra. Fourier transform
analysis consists of determining the ion
cyclotron resonances (which refers to the
number of orbits completed/sec), not by
scanning slowly through the spectrum as a
function of frequency, but by recording the
oscillating charge induced in a detector
plate by orbiting ions as they approach and
recede from that plate. FT of that
time-domain data then yields ALL of the
cyclotron frequencies at once, for a time
saving by a factor of ~10,000. The FTICR-MS
consists of an ion source, some ion optics to
transfer the ions into the magnetic field,
and the Ion Cyclotron Resonance (ICR) cell or
Penning trap. After ion's are trapped in the
ICR cell, they are excited by a resonant
excitation pulse into a coherent orbit. The
excitation amplifier is then turned off and
the ions continue to orbit at their final
radius. Ions moving near electrodes cause an
image charge to form on these electrodes to
balance the ions' electric field. In the case
of a circular orbit, this image charge will
oscillate at the ion's resonant frequency,
and can be detected by a sensitive
preamplifier circuit, digitized, and stored
in computer memory.
http://www.cprmap.com/proteomic_technologies/
mass_spectrometry/1271.html
Tags : Fourier transform ion cyclotron resonance mass spectrometry |
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Affichage : 5921
Durée : 82 s |
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