Image Charge Signal Peak Filtering via Phase Angle Validity
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Solution Overview
Problem
Ion trap mass spectrometry faces challenges in processing image charge/current signals with multiple harmonic components, leading to overlapping peaks that complicate the determination of mass/charge ratios, especially when ions have a wide range of mass/charge ratios, and existing methods are computationally intensive or require multiple pick-up electrodes.
Innovation Solution
A method involving a validity test based on phase angle analysis is applied to identify and exclude peaks not belonging to selected harmonic components, using a predetermined relationship between phase angle and frequency to form a new image charge/current signal that enhances mass resolution and reduces computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fourier transform is applied to image charge/current signals with multiple harmonic components, then frequency spectrum is obtained, but overlapping peaks occur when ions have wide range of mass/charge ratios
Solution Approach 1:
The frequency spectrum is segmented by harmonic components. The method identifies and separates peaks belonging to different harmonic orders (fundamental, second harmonic, third harmonic, etc.) using phase angle analysis. This segmentation prevents overlapping peaks from different harmonics from being confused, thereby improving mass resolution even when ions have a wide range of mass/charge ratios.
Solution Approach 2:
The method changes the parameter used for peak identification from frequency alone to a combination of frequency and phase angle. By introducing phase angle as an additional discriminating parameter, the method can distinguish between peaks at the same frequency that belong to different harmonic components, thus preventing peak overlap and improving measurement precision.
2Measurement precision
If existing methods are used to process signals with multiple harmonic components, then mass analysis is achieved, but computational complexity increases
Solution Approach 1:
The method extracts only the necessary information (phase angle at peak frequency) from the Fourier transform output to identify harmonic components. By taking out just the phase angle parameter at each peak frequency and comparing it against expected values for different harmonic orders, the method achieves accurate mass analysis with minimal computational overhead, avoiding complex processing algorithms.
Solution Approach 2:
The Fourier transform output itself provides the phase angle information needed for harmonic identification. The method uses the self-contained phase angle data already present in the frequency spectrum without requiring additional measurements or complex external processing, thereby reducing computational complexity while maintaining accuracy.
3Reliability
If multiple pick-up electrodes are used to reduce harmonic interference, then signal quality improves, but device complexity increases
Solution Approach 1:
The method replaces the mechanical/apparatus-based solution of using multiple pick-up electrodes with a signal processing-based solution. Instead of physically separating harmonic components through multiple sensors, the method uses phase angle analysis in the frequency domain to identify and separate harmonic peaks computationally, thereby maintaining signal quality while reducing device complexity.
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 allows for higher mass resolution and reduced computational requirements, enabling accurate determination of mass/charge ratios without the need for multiple pick-up electrodes, by selectively retaining peaks that meet specific phase angle criteria, thus improving the clarity of mass spectra.
Implementation Method 1
If ions are trapped using an electrostatic field, the ion trap is commonly referred to as an 'electrostatic' ion trap
Implementation Method 2
obtain, non-destructively, an image charge/current signal representative of trapped ions undergoing oscillatory motion
Implementation Method 3
This image charge/current signal is usually converted to the frequency domain e.g. using a Fourier transform ('FT'), preferably a fast Fourier transform ('FFT')
Data Source
Figure 1a~1b
Figure 1c
Figure 2
AI summary
A method of processing an image charge/current signal representative of trapped ions undergoing oscillatory motion. The method includes applying a validity test to each of a plurality of peaks in the image charge/current signal in the frequency domain, wherein applying the validity test to a peak in the image charge/current signal in the frequency domain includes determining whether a phase angle associated with the peak meets a predetermined condition. The method also includes forming a new image charge/current signal that: includes data representative of one or more peaks that have passed the validity test; and excludes data representative of one or more peaks that have failed the validity test. The method may be performed by a mass spectrometry apparatus.