Ion Mobility Spectrometer Segmented Drift Tube Resolution
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Solution Overview
Problem
Current ion mobility separation methods face challenges in achieving high resolution at lower pressures, requiring longer drift tubes and increased demands on vacuum systems, making them impractical for commercial instruments.
Innovation Solution
The use of an ion gate that applies DC and/or RF potentials to control ion transmission, allowing ions within specific time windows to pass through while storing those outside the window in ion traps for repeated separation, thereby enhancing resolution without the need for lengthy drift tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a relatively long drift tube is employed to achieve high resolution mobility separation at lower pressures, then resolution is improved, but device complexity and vacuum system demands increase
Solution Approach 1:
The drift tube is divided into multiple segmented electrodes along its length, allowing independent voltage control of each segment. This segmentation enables the creation of localized electric field regions that can be dynamically adjusted, effectively replacing the need for a single long drift tube with multiple shorter, controllable sections that work together to achieve the same separation resolution.
Solution Approach 2:
The patent employs dynamic voltage control where transient DC potentials are applied to different segments at different times rather than maintaining static fields throughout. This dynamic approach allows ions to be accelerated and separated in staged manner, improving resolution without requiring proportionally longer drift tube lengths, as the electric field configuration changes actively during the ion transit.
2Measurement precision
If a relatively long drift tube is used to maintain low field limit for high resolution, then resolution is improved, but vacuum system demands increase
Solution Approach 1:
By segmenting the drift tube into multiple independently controlled sections, the patent can maintain appropriate field strengths in each segment without requiring the entire tube to be extremely long. This allows the system to achieve high resolution while operating at lower overall pressure requirements, as each segment contributes to the cumulative separation effect.
Solution Approach 2:
The patent dynamically changes the electric field parameters (voltage, duration, spatial distribution) across different segments during ion transit. This parameter modulation allows the system to maintain ions within the low field regime where mobility separation is most effective, achieving high resolution without the need for excessively long drift tubes that would demand higher vacuum systems.
3Measurement precision
If transient DC potentials are applied to segments of an RF ion guide, then ion mobility separation is achieved, but device complexity increases
Solution Approach 1:
The patent implements physical segmentation of the drift tube into multiple electrodes or electrode sections, each capable of independent voltage control. This segmentation is essential for applying transient DC potentials to different regions, enabling the traveling wave mechanism that separates ions by mobility while maintaining RF confinement in the radial direction.
Solution Approach 2:
The segmented electrodes serve multiple functions simultaneously: they provide RF confinement potentials for radial ion guidance, apply transient DC separation potentials for mobility-based ion sorting, and create the traveling wave pattern for ion transport. This multi-functionality reduces the need for separate dedicated components for each function, thereby managing device complexity more effectively.
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 allows for improved ion mobility separation resolution at lower pressures by selectively transmitting ions within defined time windows, reducing the length of the drift tube required and optimizing vacuum system demands.
Implementation Method 1
ions separate along the longitudinal axis according to their ion mobility
Implementation Method 2
RF pseudo-potential well may be arranged to confine ions radially
Implementation Method 3
a DC electric field must be generated which is orthogonal to the RF radial confinement
Implementation Method 4
The transient DC potentials generate a travelling wave which moves along the axial direction and translates ions along the ion mobility separator
Data Source
Figure 1
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Figure 3A
AI summary
An ion mobility spectrometer is disclosed wherein ions are passed through an ion mobility spectrometer (5) and become temporally separated. Ions having a relatively high ion mobility are transmitted by a non-destructive ion gate (6) but ions having a relatively low ion mobility are subsequently trapped within the ion mobility spectrometer (5) when the ion gate (6) is switched so as to prevent ions from being onwardly transmitted. Ions which are transmitted by the ion gate (6) are trapped in a downstream ion trap (7). The ions are then returned back upstream to a second upstream ion trap (4).