Orthogonal Acceleration Time of Flight Mass Spectrometer Wrap-Around Correction
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Solution Overview
Problem
Conventional orthogonal acceleration Time of Flight mass spectrometers face issues with time of flight spectral wrap-around, leading to incorrect mass to charge ratio assignments due to the periodicity of the orthogonal acceleration electric field, resulting in suboptimal ion sampling duty cycles, especially for ions with lower mass to charge ratios.
Innovation Solution
The method involves repeatedly energizing the orthogonal acceleration electrode with a periodicity less than the time of flight of ions having the maximum mass to charge ratio, allowing for the combination and comparison of mass spectral data sets to identify and correct for wrap-around effects, thereby enhancing the sampling duty cycle and accuracy across a wide range of mass to charge ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the periodicity of the orthogonal acceleration electric field is set to prevent time of flight spectral wrap-around, then measurement precision is improved, but productivity decreases due to reduced ion sampling duty cycle
Solution Approach 1:
The patent applies periodic action by using multiple orthogonal acceleration frequencies (f1, f2, f3) in sequence. Each frequency operates periodically to accelerate ion packets, and by combining data from multiple periods with different frequencies, the system achieves both high measurement precision (preventing wrap-around at each frequency) and high productivity (increasing overall sampling duty cycle through multi-frequency operation).
Solution Approach 2:
The patent segments the ion sampling process into multiple frequency components. Instead of using a single periodic frequency, the system divides the sampling into several orthogonal acceleration events at different frequencies (f1, f2, f3), each contributing a portion of the total sampling duty cycle. This segmentation allows the system to overcome the limitation of single-frequency operation while maintaining precision at each segment.
2Measurement precision
If the time period between successive orthogonal acceleration events is increased to accommodate high mass to charge ratio ions, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The system uses multiple periodic acceleration frequencies to reduce the effective time period between acceleration events. By operating at higher frequencies (f2, f3) in addition to the base frequency (f1), the system achieves more frequent sampling without increasing the maximum time period for any single frequency, thus preventing wrap-around while reducing overall time loss.
Solution Approach 2:
The patent maintains continuity of useful action by continuously accelerating ion packets at multiple overlapping frequencies. Instead of having long idle periods between acceleration events, the system ensures continuous ion packet generation and acceleration through multi-frequency operation, eliminating unnecessary time losses while maintaining the precision required to prevent spectral wrap-around.
3Productivity
If the orthogonal acceleration frequency is increased to improve sampling duty cycle, then productivity is improved, but measurement precision deteriorates due to spectral wrap-around
Solution Approach 1:
The patent segments the high-frequency sampling into multiple discrete frequency components (f1, f2, f3). Each frequency component operates at a level that prevents spectral wrap-around, maintaining measurement precision. The segmented frequencies collectively achieve the high overall sampling duty cycle that would be impossible at any single frequency, thus resolving the contradiction between productivity and precision.
Solution Approach 2:
The system uses coordinated periodic actions at multiple frequencies to achieve high productivity without sacrificing precision. Each frequency (f1, f2, f3) performs periodic acceleration at controlled intervals that prevent wrap-around, while the combination of these periodic actions creates an effective high-duty-cycle sampling system that improves productivity.
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 increases the ion sampling duty cycle and improves the accuracy of mass spectrometry by reducing wrap-around errors, allowing for more efficient and precise analysis of ions across a broader range of mass to charge ratios.
Implementation Method 1
An orthogonal acceleration electric field is then periodically applied across the orthogonal acceleration region
Implementation Method 2
The length of the orthogonal acceleration region, the energy of the ions and the frequency of application of the orthogonal acceleration electric field determine the sampling duty cycle for sampling ions for analysis in the Time of Flight mass analyser
Implementation Method 3
Ions having approximately the same energy but different mass to charge ratios will have different velocities
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
A Time of Flight mass analyser is disclosed wherein the time period between successive orthogonal acceleration pulses is less than the time of flight of ions having the maximum mass to charge ratio of interest. As a result, some ions are subject to wrap-around and will appear in a subsequent mass spectrum. Mass spectra obtained at two different sampling rates may be compared and mass peaks relating to ions which have and have not been subject to wrap-around may be identified.