Open Electrostatic Trap Mass Spectrometer Duty Cycle
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Solution Overview
Problem
Existing multi-pass time-of-flight mass spectrometers face limitations in duty cycle and dynamic range due to space charge saturation, which restricts the acceptance of high ion fluxes from modern ion sources, especially at high speeds of data acquisition.
Innovation Solution
The introduction of an open electrostatic trap with a non-fixed flight path allows ion packets to experience multiple isochronous oscillations, enabling the reconstruction of mass spectra from partially overlapping signals and extending the space charge capacity and dynamic range by varying the number of oscillations and their span, thereby enhancing sensitivity and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-pass time-of-flight mass spectrometers are used to increase resolution, then the flight path is extended, but space charge saturation occurs which limits duty cycle and dynamic range
Solution Approach 1:
The patent applies dynamics by making the number of oscillations variable rather than fixed. Ions can complete different numbers of oscillations (N, N-1, N-2, etc.) before detection, creating a dynamic system where the flight path length adapts to individual ion trajectories and space charge conditions, thereby maintaining high resolution while increasing duty cycle and dynamic range
Solution Approach 2:
The patent segments the ion packet into multiple groups that complete different numbers of oscillations. Each group is detected separately, allowing the system to process higher ion fluxes without space charge saturation by distributing ions across multiple detection windows rather than requiring all ions to complete the same fixed number of oscillations
2Measurement precision
If the number of oscillations is increased to improve resolution, then sensitivity increases, but space charge saturation occurs which limits the acceptance of high ion fluxes
Solution Approach 1:
The system dynamically adjusts the effective flight path by allowing ions to complete variable numbers of oscillations. This enables the analyzer to accept high ion fluxes from modern ion sources by distributing the ion burden across multiple oscillation cycles and detection windows, preventing space charge saturation while maintaining high resolution through the isochronous nature of the oscillations
Solution Approach 2:
The patent uses preliminary time-of-flight separation before the oscillation cycles to pre-sort ions based on their mass-to-charge ratio. This preliminary action reduces the ion flux burden during the oscillation phases, preventing space charge saturation while still allowing high-resolution analysis through the subsequent variable-number oscillation cycles
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 significantly increases the duty cycle and sensitivity of mass spectrometers, enabling the analysis of higher ion fluxes and improving the combination of resolution, sensitivity, and dynamic range, particularly in tandem mass spectrometry and other forms of ion separation methods.
Implementation Method 1
arrangements of electrostatic fields, by ion trajectories and by detection principles. In conventional E-Traps, the fields do trap ions in all three directions and ions may be trapped indefinitely. In M-TOF, ion packets propagate through the electrostatic analyzer along a fixed flight path to a detector. In open E-traps, ions also propagate through the analyzer while being confined in at least one direction, but the flight path is not fixed—it may contain an integer number N of oscillations within some span ΔN before ions reach a detector.
Implementation Method 2
Time-of-flight mass spectrometers (TOF MS) are widely used in analytical chemistry for identification and quantitative analysis of various mixtures. Sensitivity and resolution of such analysis is an important concern for practical use.
Data Source
AI summary
An open electrostatic trap mass spectrometer is disclosed for operation with wide and diverging ion packets. Signal on detector is composed of signals corresponding to multiplicity of ion cycles, called multiplets. Using reproducible distribution of relative intensity within multiplets, the signal can be unscrambled for relatively sparse spectra, such as spectra past fragmentation cell of tandem mass spectrometer, past ion mobility and differential ion mobility separators. Various embodiments are provided for particular pulsed ion sources and pulsed converters such as orthogonal accelerators, ion guides, and ion traps. The method and apparatus enhance the duty cycle of pulsed converters, improve space charge tolerance of the open trap analyzer and extends the dynamic range of time-of-flight detectors.