Frequency Mass Spectrometer Drift Correction
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Solution Overview
Problem
Frequency mass spectrometers face challenges in maintaining constant instrument parameters during long measuring times, leading to temporal frequency modulations and reduced mass resolution due to parameter drifts, especially from space charge and electric potential variations.
Innovation Solution
A method to detect and correct parameter drifts by determining the instantaneous frequency of time signals, transforming the time axis to maintain constant frequency profiles, and converting the signals into corrected frequency mass spectra, thereby improving mass determination accuracy and reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long measuring times are used to improve mass resolution, then mass resolution is improved, but parameter drift occurs leading to frequency modulation and reduced accuracy
Solution Approach 1:
The patent applies feedback by continuously monitoring the instantaneous frequency of ion packets and using this information to correct for parameter drifts. The system measures the actual frequency deviations caused by space charge and other parameters, then applies corrections to compensate for these drifts, ensuring accurate mass determination even during long measurement periods.
Solution Approach 2:
The patent changes the approach from attempting to maintain absolutely constant parameters to actively measuring and compensating for parameter changes. By determining instantaneous frequency as a function of time and analyzing drift characteristics, the system adapts to changing conditions rather than relying on perfect parameter stability.
2Quantity of substance
If space charge effects are present in the ICR measuring cell, then ion detection is enabled, but cyclotron frequencies drift temporally reducing mass resolution
Solution Approach 1:
The patent converts the harmful space charge effect into a useful signal by measuring the instantaneous frequency shifts it causes. Rather than trying to eliminate space charge, the system uses its frequency-modulating effect as information about the ion population, then compensates for it to maintain both detection capability and mass resolution.
3Reliability
If electric potentials for axial trapping are increased to improve ion confinement, then ion trapping is improved, but cyclotron frequency changes leading to frequency modulation
Solution Approach 1:
The patent uses feedback to monitor and compensate for frequency changes induced by electric potential adjustments. By continuously determining instantaneous frequency and comparing it to reference values, the system can correct for frequency modulations caused by trapping potential variations, maintaining both ion confinement and frequency accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances mass resolution and accuracy by compensating for temporal parameter changes, particularly addressing space charge effects and improving reproducibility across successive measurements.
Implementation Method 1
The image currents are recorded as time signals ('transients') and converted into a frequency spectrum by a Fourier transformation.
Implementation Method 2
the excited ions generate image currents in detection electrodes
Implementation Method 3
ion packets are excited to mass-specific cyclotron motions in a strong magnetic field
Data Source
AI summary
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.