Tandem Ion Traps for Mass Spectrometry Resolution
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Solution Overview
Problem
Conventional ion trap mass spectrometers face challenges with spectral resolution decline and space charge effects, leading to lost mass spectral peaks, spontaneous emptying, and spectral distortion due to high ion density.
Innovation Solution
A tandem mass spectrometer system with two ion traps is operated in tandem, where ions are selectively transferred and ejected using mass-selective axial ejection techniques, controlling RF and DC voltages and auxiliary AC fields to manage ion density and reduce space charge effects, allowing for higher resolution and reduced ion trap length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ions are accumulated in high density in a single ion trap, then ion detection sensitivity is improved, but spectral resolution declines and space charge effects cause peak loss and distortion
Solution Approach 1:
The patent divides the ion accumulation function into two separate ion traps (first and second ion traps). The first ion trap accumulates ions at high density, while the second ion trap receives transmitted ions at lower density. This segmentation allows each trap to operate within optimal density ranges, preventing space charge effects from degrading spectral resolution while maintaining high overall ion detection capability.
Solution Approach 2:
The second ion trap acts as an intermediary between the first ion trap and the detector. Ions are transmitted from the first trap through a mass gate to the second trap, which then transmits them to the detector. This intermediary trap buffers the ion population, reducing space charge effects on the spectral measurement while preserving detection sensitivity.
2Device complexity
If a single ion trap is used to accumulate all ions, then device complexity is reduced, but ion trap length must be increased to maintain resolution
Solution Approach 1:
Instead of using one long ion trap, the patent segments the system into two shorter ion traps connected by a transmission region with a mass gate. Each trap can be optimized for its specific function (accumulation vs. transmission/detection), allowing the overall system to achieve the required resolution without needing a single excessively long trap structure.
3Measurement precision
If mass-selective transmission is implemented between traps, then spectral resolution is improved, but operation complexity increases
Solution Approach 1:
The mass gate operates periodically, alternately transmitting ions of different mass ranges from the first ion trap to the second ion trap. This periodic operation allows systematic coverage of the full mass range through multiple cycles, achieving high mass selectivity and spectral resolution while maintaining manageable operational complexity through automated cyclic control.
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 spectral resolution, reduces space charge effects, and maintains high ion trap efficiency by selectively ejecting ions, thereby preventing peak loss and distortion, and allowing for narrower mass ranges in the second ion trap.
Implementation Method 1
Appropriate RF/DC voltages can be applied to the electrodes to establish a three dimensional field that traps ions within a specified mass-to-charge range
Implementation Method 2
Linear quadrupoles may also be configurable as ion trap mass spectrometers, with radial ion confinement being provided by an applied RF voltage and axial ion confinement by DC potential barriers
Implementation Method 3
mass-selective detection of ions trapped within a linear ion trap can utilize radial ejection of ions, as taught by U.S. Pat. No. 5,420,425, or axial ejection of ions (MSAE), as taught by U.S. Pat. No. 6,177,668
Data Source
AI summary
A method for operating tandem ion traps is provided, involving a) accumulating ions in the first ion trap at a first time; b) transmitting a first plurality of ions out of the first ion trap and into the second ion trap at a second time, the first plurality of ions having masses within a first mass range; c) retaining a second plurality of ions in the first ion trap at the second time, the second plurality of ions having masses within a second mass range different from the first mass range; d) transmitting the first plurality of ions out of the second ion trap at a third time; and, e) transmitting the second plurality of ions out of the first ion trap and into the second ion trap at the third time.