Spherical Ion Trap for Electron Transfer Dissociation
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Solution Overview
Problem
Conventional 3D ion traps exhibit low fragmentation efficiency for positively charged analyte ions during Electron Transfer Dissociation reactions due to minimal ion fragmentation observed, and they have limited ion trapping volume compared to 2D and linear ion traps.
Innovation Solution
A modified Electron Transfer Dissociation device with a plurality of electrodes forming a spherical or ellipsoidal ion trapping volume, where ions are cooled to near thermal temperatures, and a neutrally charged bath gas is used to maintain low mean kinetic energy differences between ions and gas molecules, enhancing fragmentation efficiency and ion trapping capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional 3D ion trap is used for Electron Transfer Dissociation, then the device structure is simple, but the fragmentation efficiency is low
Solution Approach 1:
The ion trap is segmented into multiple functional zones along the ion trajectory: an ion storage region, a reaction region with controlled gas pressure for ETD, and a detection region. This segmentation allows optimization of fragmentation efficiency in the reaction zone while maintaining overall device functionality, resolving the contradiction between simple structure and high fragmentation efficiency
Solution Approach 2:
A neutral bath gas (e.g., nitrogen or helium) is introduced as an intermediary medium in the reaction region to facilitate energy transfer and enhance fragmentation efficiency during ETD reactions, while not interfering with the overall device simplicity. The gas acts as a mediator between ions and the reaction process, improving productivity without significantly complicating the device structure
2Volume of stationary object
If a conventional 3D ion trap is used, then the device is compact, but the ion trapping volume is limited
Solution Approach 1:
The ion trap transitions from a conventional 3D configuration to a linear or near-linear geometry, extending the trapping volume along the axial dimension. This dimensional reconfiguration allows for larger ion trapping capacity while maintaining a compact footprint in the radial direction, effectively increasing the stationary object volume without proportionally increasing overall device complexity
3Stability of the object's composition
If RF voltages are applied in a conventional ion trap, then ion confinement is achieved, but RF heating effects increase ion kinetic energy
Solution Approach 1:
Different regions of the ion trap are assigned different RF voltage characteristics: the storage region uses standard RF confinement, while the reaction region employs modified RF parameters or DC offsets to minimize heating effects. This local differentiation allows maintained ion confinement stability while controlling ion kinetic energy and temperature in the fragmentation zone
Solution Approach 2:
RF voltages are applied in periodic pulses rather than continuously, with synchronization to the ion arrival and reaction cycles. The periodic application provides ion confinement when needed while allowing kinetic energy dissipation during off-periods, thereby maintaining confinement stability while reducing average ion temperature and heating effects
4Productivity
If ions are cooled to near thermal temperatures, then fragmentation efficiency increases, but the device requires additional cooling mechanisms
Solution Approach 1:
The neutral bath gas in the reaction region serves a dual function: it acts as a buffer gas to collisionally cool ions to near thermal temperatures, enhancing fragmentation efficiency, while simultaneously serving as the primary medium for the ETD reaction. This self-service approach achieves ion cooling without requiring separate active cooling mechanisms, maintaining device simplicity while improving 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
The device significantly increases ion-ion collision rates and fragmentation efficiency, providing a larger ion trapping volume with reduced RF heating effects, leading to improved sensitivity in Electron Transfer Dissociation reactions compared to conventional 2D and 3D ion traps.
Implementation Method 1
a neutrally charged bath gas is used to maintain low mean kinetic energy differences between ions and gas molecules
Implementation Method 2
Electron Transfer Dissociation involves causing highly charged positive analyte ions to interact or collide with negatively charged reagent ions. As a result of an ion-ion reaction the positively charged analyte ions are caused to fragment into a plurality of fragment or product ions
Data Source
AI summary
A mass spectrometer is disclosed comprising an Electron Transfer Dissociation cell. Positive analyte ions are fragmented into fragment ions upon colliding with singly charged negative reagent ions with the cell. The cell comprises a plurality of ring electrodes which form a spherical trapping volume. Ions experience negligible RF heating over the majority of the trapping volume which enables the kinetic energy of the analyte and reagent ions to be reduced to just above thermal temperatures. An Electron Transfer Dissociation cell having an enhanced sensitivity is thereby provided. Fragment ions created within the cell may be cooled and may be transmitted onwardly to an orthogonal acceleration Time of Flight mass analyser enabling a significant improvement in the resolution of the mass analyser to be obtained.