Supplemental Electrodes for Quadrupole Mass Filter Field Correction
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Solution Overview
Problem
Current quadrupole mass spectrometers face challenges in achieving a pure quadrupolar electric field due to slot-induced field distortions, which affect both linear ion trap and quadrupole mass filter modes, and existing compensation methods are not adjustable or effective in correcting manufacturing defects.
Innovation Solution
A two-dimensional quadrupole device with supplemental insert electrodes within slots, allowing for independent optimization of RF voltages for ion trap and quadrupole mass filter modes, and adjustable compensation for mechanical distortions, to achieve a more pure quadrupolar field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If slots are added to electrodes for ion ejection, then ion trap functionality is enabled, but field distortion increases and quadrupole mass filter performance deteriorates
Solution Approach 1:
The electrode structure is segmented into main rod electrodes and supplemental insert electrodes. The supplemental electrodes are divided into multiple segments positioned at different locations within the slots, allowing independent voltage control for each segment to compensate for field distortions caused by the slot openings.
Solution Approach 2:
The supplemental insert electrodes are positioned locally within the slots at specific locations where field distortion is most problematic. By applying localized compensating voltages only at these critical positions, the field uniformity is restored without affecting the overall slot functionality for ion ejection.
2Reliability
If fixed compensation methods are used for slot-induced field distortion, then some field correction is achieved, but adjustability for different operating modes and manufacturing defects is lost
Solution Approach 1:
The voltage applied to the supplemental insert electrodes is made dynamic and adjustable rather than fixed. The system allows real-time modification of electrode voltages to optimize performance for different operating modes (ion trap vs. quadrupole mass filter) and to compensate for manufacturing variations in each specific device.
Solution Approach 2:
The electrical parameters (voltages) of the supplemental insert electrodes are changed and optimized based on the operating mode and manufacturing defects. By adjusting voltage magnitudes and phases of individual supplemental electrodes, the system adapts to different operational requirements and compensates for device-specific variations.
3Manufacturing precision
If supplemental insert electrodes are added within slots, then field distortion compensation is improved, but device complexity increases
Solution Approach 1:
The supplemental insert electrodes are nested within the existing slot structures of the main rod electrodes. This nested configuration allows the compensation electrodes to be integrated into the existing device geometry without requiring complete structural redesign, thereby limiting the increase in overall device complexity.
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
Enables the same apparatus to function effectively as both a linear ion trap and a quadrupole mass filter with improved field correction, enhancing ion transmission and mass spectrometry performance by minimizing field distortions and accommodating manufacturing variations.
Implementation Method 1
consist of four elongated electrodes, each electrode having a hyperbolic-shaped surface, arranged in two electrode pairs aligned with and opposed across the centerline midway between each electrode pair
Implementation Method 2
Opposite phases of an RF voltage are applied between the rods separated in the X dimension, versus those separated in the Y dimension. This applied RF voltage affects the movement of ions in the X and Y dimensions, including the containment of the ions within the device
Implementation Method 3
at least one supplemental insert electrode is disposed at least partially within the slot along a portion of the length of the slot... such that it can be experimentally optimized to independent respective optimum values for operation of the device in either an ion trap mode or a quadrupole mass filter mode
Implementation Method 4
a dipole resonant excitation voltage is applied across the electrodes of the apertured electrode pair... while the amplitude of the RF voltage is ramped. This operation causes the trapped ions to come into resonance with the applied excitation voltage in order of their m/z ratios
Implementation Method 5
By properly choosing the magnitude of DC and RF voltages applied to the rods, the range of ions that pass completely through the apparatus can be restricted to only a desired narrow m/z range
Data Source
AI summary
An apparatus for a mass spectrometer comprises: a set of four rod electrodes defining an ion occupation volume therebetween having entrance and exit ends, at least one of the rod electrodes having a slot passing therethrough; first and second ion optics disposed adjacent to the entrance and exit ends, respectively; a voltage supply system; and at least one supplemental electrode disposed at least partially within the at least one slot, wherein the voltage supply system is configured so as to supply a radio-frequency (RF) voltage, a direct-current (DC) filtering voltage and an oscillatory dipole resonant ejection voltage across members of the set of rod electrodes and so at to supply a secondary ion-trapping RF voltage and a secondary DC filtering voltage to the at least one supplemental electrode and to supply DC voltages across the rod electrodes and each of the first and second ion optics.