Selective Ion Mobility Spectrometer Using Consecutive Filters
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Solution Overview
Problem
Current ion mobility spectrometers face limitations in achieving high resolution due to diffusion broadening in long drift regions and high electric field strengths, resulting in low mobility resolution and the need for large apparatus, which complicates the differentiation of ion species with similar mobilities.
Innovation Solution
The use of at least two consecutive mobility high pass and/or low pass filters to select ions within a predetermined range of mobilities, either for collection or to generate a constant beam of ions with predetermined mobility, allowing for further investigation or analysis by a mass spectrometer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long drift regions are used to improve ion mobility resolution, then mobility resolution is improved, but device size and complexity increase
Solution Approach 1:
The invention divides the ion mobility separation function into multiple discrete filters arranged in series. Each filter performs a segment of the separation task by selecting ions within a specific mobility range, collectively achieving high-resolution separation without requiring a single long drift region.
Solution Approach 2:
The invention transitions from temporal separation in a single spatial dimension (long drift region) to simultaneous spatial separation across multiple dimensions (series of filters). Each filter acts as an independent spatial stage, enabling high resolution through multi-stage filtering rather than extended drift time.
2Speed
If high electric field strengths are applied to improve ion mobility measurement, then measurement speed is improved, but diffusion broadening increases reducing resolution
Solution Approach 1:
The invention segments the ion beam into multiple mobility components using series filters, each operating at optimized field strengths. This allows each filter stage to operate at lower field strengths that minimize diffusion broadening, while the cumulative effect across stages maintains measurement efficiency.
Solution Approach 2:
The invention employs dynamically adjustable filter parameters including electric field strength and gas flow rate. By optimizing these parameters at each filter stage, the system balances ion transmission speed with minimal diffusion broadening, achieving both speed and resolution.
3Measurement precision
If conventional single filter approach is used, then device simplicity is maintained, but ion mobility resolution is insufficient
Solution Approach 1:
The invention uses multiple filters in series, where each filter is a relatively simple component. The segmentation of the separation task across multiple simple stages achieves high resolution without requiring any single component to be overly complex.
Solution Approach 2:
The invention combines multiple filters with different mobility selection characteristics in series. By merging these filters, the system achieves a cumulative separation effect that provides high resolution while using standard, well-understood filter technologies.
4Productivity
If continuous ion beam is maintained for analysis, then productivity is improved, but ion mobility selection precision decreases
Solution Approach 1:
The invention maintains continuous ion beam transmission through the series of filters, ensuring uninterrupted analysis and high productivity. Each filter is designed to transmit selected ions continuously without interruption, preserving both throughput and selection precision.
Solution Approach 2:
The continuous ion beam is segmented by mobility into multiple streams through the series filters. Each filter stage performs precise selection on a portion of the beam, enabling high-resolution separation while maintaining overall continuous operation and high throughput.
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 enhances ion mobility resolution by selectively collecting or filtering ions, enabling more detailed analysis and improving the ability to distinguish between ions with closely related mobilities, potentially achieving higher resolution without the need for lengthy drift regions.
Implementation Method 1
The large number of collisions with the gas molecules results in a constant drift velocity vd for each ion species which is proportional to the electric field strength E: vd=μ×E. The proportionality factor μ is called the 'ion mobility' of the ion species.
Implementation Method 2
In the gas of the drift region, these ion clouds are subject to diffusion, caused by collisions statistically distributed in terms of spatial directions and kinetic energies due to the molecular Brownian motion.
Data Source
AI summary
Ions with a predetermined range of ion mobilities are produced by filtering input ions with at least two consecutive ion mobility high pass and/or low pass filters. Each ion mobility filter is formed by entraining ions in a moving gas and applying a DC electric field to the ions which causes the ions to move in a direction opposite to the gas flow. An ion mobility high pass filter is formed when the DC electric field drives the ions against the flow of gas, whereas an ion mobility low pass filter is formed when a the gas flow drives entrained ions against an DC electric field barrier.