Ion Trap Counter Ion Cooling for Mass Spectrometer Resolution
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Solution Overview
Problem
Mass spectrometers face challenges in reducing space charge effects that lead to increased spatial distribution of ions, affecting transmission and resolution, particularly in orbital trapping and Time of Flight (ToF) analyzers.
Innovation Solution
The introduction of counter ions of opposing charge, which are cooled simultaneously with analyte ions in an ion trap, reduces the spatial distribution of analyte ions by balancing out the net charge, thereby minimizing space charge effects and improving the accuracy and resolution of ion injection into mass analyzers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of trapped analyte ions is increased, then the signal intensity is improved, but the spatial distribution of ions increases rapidly due to space charge effects
Solution Approach 1:
Counter ions are introduced as an intermediary species to mediate the space charge effects. These counter ions, having opposite charge to the analyte ions, partially neutralize the space charge and reduce the repulsive forces between analyte ions, thereby maintaining tighter spatial distribution even at higher ion densities
Solution Approach 2:
The net charge parameter of the ion ensemble is changed by introducing counter ions. This parameter change reduces the overall space charge effect, allowing higher ion densities to be maintained without the proportional increase in spatial distribution that would normally occur
2Manufacturing precision
If the spatial distribution of analyte ions is reduced, then the transmission and resolution of the mass analyser is improved, but the number of ions that can be trapped is limited due to space charge effects
Solution Approach 1:
Counter ions serve as a mediating species that enables higher ion densities to be trapped while maintaining acceptable spatial distribution. The counter ions reduce the net repulsive forces, allowing more analyte ions to be confined in the extraction trap without proportionally increasing the spatial spread
3Manufacturing precision
If counter ions are introduced into the ion trap, then the spatial distribution of analyte ions is reduced, but the device complexity increases
Solution Approach 1:
The ion trap system is extended to perform multiple functions: trapping and cooling analyte ions, trapping and cooling counter ions, and facilitating their mutual neutralization. This multi-functionality is achieved by using the same trap structure and cooling mechanisms for both ion types, minimizing additional hardware complexity
Solution Approach 2:
The operational parameters of the ion trap are dynamically adjusted to accommodate both analyte and counter ions. Voltages, cooling rates, and trapping conditions are optimized to simultaneously confine both ion types while maintaining their respective spatial distributions and enabling effective neutralization
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 the transmission efficiency and resolution of mass analyzers by reducing the spatial and temporal spread of analyte ions, allowing for a higher number of ions to be trapped and stored, and improving the signal-to-noise ratio and duty cycle.
Implementation Method 1
Coulombic repulsion, or space charge, between the trapped analyte ions opposes the confining forces of the applied potential and pseudopotential wells
Implementation Method 2
The presence of the counter ions in the extraction trap, in particular mixed with the analyte ions, results in a reduction of the spatial distribution of the analyte ions confined in the ion trap
Implementation Method 3
cooling the analyte ions and the counter ions simultaneously in the ion trap such that a spatial distribution of the analyte ions in the ion trap is reduced
Data Source
AI summary
A method of injecting analyte ions into a mass analyser comprises: injecting analyte ions of a first charge and counter ions of a second charge into an ion trap; cooling the analyte ions and the counter ions simultaneously in the ion trap such that a spatial distribution of the analyte ions therein is reduced; and injecting the analyte ions as an ion packet from the ion trap into the mass analyser. A mass spectrometer controller is configured to: cause an ion source to inject an amount of analyte ions of a first charge and an amount of counter ions of a second charge into an ion trap; cause the ion trap to simultaneously cool the analyte ions and the counter ions in the ion trap, thereby reducing a spatial distribution of the analyte ions therein; and cause the ion trap to inject the analyte ions into a mass analyser.