Lateral Ion Introduction in RF Ion Guides
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Solution Overview
Problem
Existing RF ion guides experience asymmetric disturbances and significant analyte ion losses during lateral introduction of ions, particularly due to asymmetry in the RF field, which is problematic for guiding ions to mass filters and reaction cells without causing fringe field interference.
Innovation Solution
The implementation of devices with at least two-fold rotational symmetry at the point of lateral ion introduction, including modifications to pole rods and additional electrodes, ensures symmetrical RF fields and the use of insulated electrode segments with DC voltages for loss-free deflection of ions into the ion guide, maintaining pseudopotential symmetry and minimizing ion losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ions are introduced laterally into the RF ion guide, then ion introduction capability is improved, but asymmetric disturbances and analyte ion losses occur
Solution Approach 1:
The patent applies asymmetry principle by intentionally introducing asymmetric electrode structures (deflecting electrodes with DC voltage) to compensate for the asymmetric disturbances caused by lateral ion introduction. The asymmetric deflecting electrodes create a controlled asymmetric field that guides ions into the ion guide while counterbalancing the fringe field interference, thus resolving the contradiction between enabling lateral introduction and preventing ion losses.
2Adaptability or versatility
If lateral introduction of ions is implemented, then ion guide functionality is improved, but RF field asymmetry increases
Solution Approach 1:
The patent deliberately introduces asymmetric deflecting electrodes with DC voltage to counterbalance the asymmetric disturbances from lateral ion introduction. This controlled asymmetry compensates for the RF field asymmetry caused by the lateral inlet, maintaining overall field stability while enabling enhanced ion guide functionality.
Solution Approach 2:
The patent changes the voltage parameters by applying DC voltage to specific deflecting electrodes in addition to the RF voltage. This parameter change allows dynamic control of the electric field distribution, enabling compensation for RF field asymmetry while maintaining the benefits of lateral ion introduction.
3Adaptability or versatility
If conventional lateral introduction is used, then ion introduction is possible, but fringe field interference occurs
Solution Approach 1:
The patent extracts and separates the deflection function from the main ion guide structure by introducing dedicated deflecting electrodes with DC voltage. This extraction allows independent control of the deflection field, enabling ions to be guided into the ion guide while isolating the fringe field interference to specific regions, thus reducing its harmful effects on overall system performance.
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 reduces asymmetric disturbances and achieves efficient, loss-free deflection of laterally introduced ions into the ion guide, maintaining axial focusing and minimizing ion losses, even when introducing ions at right angles, thereby enhancing the performance of RF ion guides in mass spectrometry.
Implementation Method 1
In the interior, the multipole RF field generates a so-called 'pseudopotential ', which drives the ions above a threshold mass to the central axis
Implementation Method 2
appropriate DC voltages can be applied to neighboring, insulated segments of the pole rods. The ions injected through the hexapole channel can then be accurately deflected into the longitudinal direction of the ion guide in a transverse DC quadrupole field
Implementation Method 3
electrode discs (22) and (25) are inserted into the gaps with an RF voltage of opposite polarity. Between each rod pair, hexapole field channels (27) are generated
Implementation Method 4
If the ion guides are operated with a collision gas at a pressure between 0.01 and 10 pascal, the ion motions are damped and the ions are collected in the axis of the system because of the effect of the pseudopotential
Data Source
AI summary
An ion guide system includes an ion guide with pole rods, a device for laterally introducing an ion species, and a mass spectrometer for analyzing product ions of reactions between different ion species. The device is configured and positioned such that an RF field with at least two-fold rotational symmetry with respect to the axis is generated. The device includes shortened pole rods and/or further electrodes. The pole rods and the further electrodes have at least two-fold rotational symmetry. The symmetry of the RF field allows ions to travel straight ahead through the ion guide with no hindrance. Such arrangements are particularly suitable for bringing together largely loss-free positive and negative ion species for reacting them. The reactions may be used to fragment multiply charged biopolymer ions by electron transfer or to remove excess charges of multiply charged biopolymer ions.