Ion Mobility Spectrometer With Segmented Electrodes
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Solution Overview
Problem
Ion mobility spectrometers face challenges in achieving high resolution and reducing diffusion losses at lower pressures, requiring long drift tubes which are space-constrained and complex to construct, and existing solutions complicate rapid ion transfer or increase construction complexity.
Innovation Solution
The method involves introducing ions into a drift space for separation, reflecting or deflecting them back into the space at lower pressure for further separation, utilizing multiple stages of ion mobility and inertial ion motion with longer mean free paths, allowing the same drift space to be reused multiple times for extended separation lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long drift tube is employed to achieve high resolution ion mobility separation at low pressures, then the resolution is improved, but the device complexity and space requirements increase
Solution Approach 1:
The drift tube is divided into multiple axially-spaced segments with individual electrodes, allowing independent voltage control for each section. This segmentation enables the creation of complex electric field patterns (such as traveling waves or reflected waves) that can achieve high resolution separation without requiring an excessively long continuous drift tube, thus reducing overall device complexity while maintaining separation performance.
Solution Approach 2:
The patent introduces temporal dimension by applying time-varying voltages to the segmented electrodes, creating traveling or reflected wave patterns that move ions through the drift tube. This transforms the separation mechanism from a simple spatial gradient to a dynamic spatiotemporal field, achieving high resolution in a more compact configuration by utilizing the time dimension for ion manipulation.
2Loss of energy
If the drift tube length is increased to reduce diffusion losses at lower pressures, then the separation resolution is improved, but the instrument size and construction complexity increase
Solution Approach 1:
The patent employs periodic voltage applications to the segmented electrodes, creating oscillating electric fields that periodically accelerate and redirect ions. This periodic action keeps ions confined to the drift tube region for extended periods, increasing the effective path length for separation without physically extending the drift tube, thereby reducing diffusion losses while maintaining a compact instrument size.
Solution Approach 2:
The segmented electrode design allows preliminary configuration of electric field patterns that pre-confine ions to specific regions before the main separation process. By establishing these preliminary field patterns, ions are kept within the drift tube volume longer, reducing premature diffusion losses without requiring a longer physical tube length.
3Speed
If transient DC potentials are applied to segments of the ion guide to create traveling waves, then ion transport speed is improved, but the device complexity increases
Solution Approach 1:
The segmented electrode structure serves multiple functions: it can generate traveling waves for rapid ion transport, create reflected waves for high-resolution separation, establish static field patterns for ion confinement, or apply time-varying patterns for ion cooling. This multi-functionality allows a single segmented electrode system to replace what would otherwise require multiple separate ion manipulation devices, reducing overall system complexity while maintaining high ion transport speeds.
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 enables high-resolution ion mobility separation with a compact design, allowing for a practically unlimited increase in separation path length and resolution without the complexity of long drift tubes, while minimizing diffusion losses.
Implementation Method 1
ions are caused to drift through a space under the influence of a constant applied electric field... as the ions travel through the tube under the influence of the constant electric field they attain a constant drift velocity and separate in the axial direction according to their ion mobility
Implementation Method 2
Operation of the ion mobility spectrometer at lower pressures frequently leads to greater diffusion losses... The buffer gas is often arranged flowing in the opposite direction to the direction of ion travel
Implementation Method 3
an RF pseudo-potential well may be arranged in the drift tube to confine ions radially so that it acts as an ion guide and may be used to transport ions efficiently
Implementation Method 4
The transient DC potentials are superimposed on top of an RF voltage which acts to confine the ions radially and/or any constant DC offset voltage. The transient DC potentials thereby generate a so-called travelling wave which moves along the length of the ion guide in the axial direction and which acts to move ions along the length of the ion mobility spectrometer
Data Source
AI summary
A method of ion mobility spectrometry wherein ions undergo multiple stages of ion mobility separation and multiple stages of inertial ion motion wherein the mean free path between ion collisions with gas is significantly longer than in the stages of ion mobility separation, wherein each stage of inertial ion motion lies between successive stages of ion mobility separation.