Mass Filter Electrode Aperture for Ion Trajectory Control
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Solution Overview
Problem
Mass filters in mass and/or ion mobility spectrometers face performance degradation due to surface charging from unwanted ions, leading to reduced transmission and resolution, as unstable ions impact and contaminate the electrodes, requiring frequent cleaning.
Innovation Solution
A two-stage mass filtering system where a lower resolution first mass filter filters out unwanted ions, preventing them from reaching the higher resolution second mass filter, with apertures or recesses in electrodes configured to direct unstable ions away from the central axis, reducing surface charging and maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a higher resolution mass filter is used alone, then measurement precision is improved, but surface charging from unwanted ions degrades performance over time
Solution Approach 1:
The mass filtering system is divided into two separate stages: a first mass filter with lower resolution that removes the majority of unwanted ions, and a second mass filter with higher resolution that provides precise mass analysis. This segmentation protects the second filter from surface charging while maintaining high measurement precision.
Solution Approach 2:
The first mass filter acts as an intermediary component between the ion source and the second mass filter. It pre-filters the ion beam to remove unwanted ions before they reach the second filter, thereby protecting it from contamination and performance degradation.
2Measurement precision
If a single high resolution mass filter is used, then measurement precision is improved, but device complexity increases due to frequent cleaning requirements
Solution Approach 1:
By segmenting the mass filtering function into two filters with different resolution requirements, the system reduces maintenance complexity. The first filter, designed for lower resolution, can be easily cleaned or replaced without affecting the high-resolution capabilities of the second filter.
3Productivity
If a lower resolution first mass filter is added upstream, then productivity is improved by extending operational time, but device complexity increases
Solution Approach 1:
The mass filtering system is segmented into two functional stages with different resolution characteristics. The first filter handles the bulk of ion filtering at lower resolution, extending operational lifetime, while the second filter maintains high resolution for accurate mass analysis.
Solution Approach 2:
The first mass filter acts as a sacrificial or disposable component that can be easily cleaned or replaced. It absorbs the burden of handling unwanted ions, protecting the more valuable second filter from contamination and extending the overall system's 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 configuration extends the operational time of the mass filter by minimizing surface charging, maintaining good transmission characteristics and reducing contamination, thus enhancing the overall instrument's performance.
Implementation Method 1
A quadrupole mass filter transmits ions that satisfy conditions of stability within the quadrupole field, wherein the stability conditions are defined by the dimensionless parameters q and a
Implementation Method 2
V is the amplitude of the RF voltage applied to the quadrupole electrodes, ω is the angular frequency of the RF voltage applied to the quadrupole
Implementation Method 3
Ions having values of a and q that result in unstable ion trajectories generally impact on the rods of the quadrupole and are lost. This property is exploited when the quadrupole rod set is used as a mass filter, such that the majority of the ions that are not desired to be transmitted by the mass filter impact on the inner surfaces of the rod electrodes
Data Source
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AI summary
A mass filter is disclosed having at least one electrode (42-48) comprising an aperture (43) or recess. Voltages are applied to the electrodes (42-48) of the mass filter such that ions having mass to charge ratios in a desired range are confined by the electrodes and are transmitted along and through the mass filter, whereas ions (47,49) having mass to charge ratios outside of said desired range are unstable and pass into the aperture (43) or recess such that they are filtered out by the mass filter. The aperture (43) or recess reduces or eliminates the number of ions that would otherwise impact the electrode surface facing the ion transmission axis and hence reduces degradation of the ion transmission properties of the mass filter.