Radiant energy – Ionic separation or analysis – Methods
Reexamination Certificate
2011-06-21
2011-06-21
Johnston, Phillip A (Department: 2881)
Radiant energy
Ionic separation or analysis
Methods
C250S291000, C250S292000
Reexamination Certificate
active
07964842
ABSTRACT:
The invention relates to the evaluation of mass spectra from mass spectrometers in which ions are excited to mass-specific oscillating or orbiting motions, and the ion motion is recorded as a time signal. The invention provides methods to detect parameter drift that occurs during the recording of a time signal in such a “frequency mass spectrometer” by analyzing the instantaneous frequency or the phase spectrum of a frequency component, and provides a method to correct for influence of the frequency drift on the mass spectrum correspondingly. In one embodiment a Fourier transformation converts a measured time signal into a frequency spectrum and examines the phase spectrum of a frequency component to establish whether this phase spectrum deviates from the phase spectrum of a harmonic time signal. The phase spectrum of a harmonic time signal is either linear or constant. In another embodiment the time domain signal is processed using a Short Time Fourier Transformation function to determine an instantaneous frequency, which can be used to correct the parameter drift, yielding a corrected time signal. From the corrected time signal a mass spectrum with better mass resolution can be derived, as can be seen from corrected mass signal profile compared with uncorrected mass signal profile.
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Köster Claus
Michelmann Karsten
Bruker Daltonik GmbH
Johnston Phillip A
O'Shea Getz P.C.
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