Ion Mobility Peak Compression Using Intermittent Traveling Waves
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Solution Overview
Problem
Conventional ion mobility separations face challenges such as peak broadening due to diffusion and ion roll over, leading to low signal-to-noise ratio and limited resolution, especially in long path lengths, and are hindered by space charge effects that restrict the initial ion population, making high-resolution detection difficult.
Innovation Solution
The application of an intermittent traveling wave to compress ion distributions into narrower peaks by varying the duty cycle, allowing for increased signal-to-noise ratio and resolution through regrouping ions into fewer mobility 'bins' using a combination of continuous and intermittent traveling waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the separation distance is increased to improve resolution, then ion mobility separation resolution is improved, but peak broadening due to diffusion and ion roll over increases, leading to lower signal-to-noise ratio
Solution Approach 1:
The patent applies periodic resetting of the traveling wave potential minima to compress ion packets that have broadened during separation. The traveling wave is periodically stopped and reset, causing ions to be refocused into narrow peaks at the resetting location, thereby recovering signal intensity while maintaining separation resolution.
Solution Approach 2:
The patent performs preliminary separation of ions over a long distance to achieve high resolution, then applies a compression phase to refocus the broadened ion packets before detection. This preliminary separation followed by compression allows the system to benefit from both long path length separation and narrow peak detection.
2Quantity of substance
If the initial ion population is increased to improve signal-to-noise ratio, then detection sensitivity is improved, but space charge effects increase, limiting further ion population accumulation
Solution Approach 1:
The periodic resetting of the traveling wave allows continuous accumulation of ions over multiple cycles. Ions are injected continuously, separated, and then compressed periodically, enabling accumulation of large ion populations without requiring all ions to be present simultaneously in the separation region, thereby reducing space charge effects.
Solution Approach 2:
The patent segments the ion population into multiple packets that are separated in time and space, then compressed individually. This segmentation allows each packet to be handled with fewer ions, reducing space charge effects, while the cumulative signal from multiple packets provides high detection sensitivity.
3Quantity of substance
If multiple passes are used to increase ion population and resolution, then both signal-to-noise ratio and resolution are improved, but peak broadening accumulates, eventually filling the entire path and making the approach ineffective
Solution Approach 1:
The periodic resetting of the traveling wave compresses ion packets after each separation pass, preventing peak broadening from accumulating. By refocusing ions into narrow peaks at regular intervals, the system can perform multiple passes without the peaks eventually filling the entire path, maintaining effectiveness over many cycles.
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 achieves higher signal-to-noise ratio and peak resolution by compressing ions into narrower distributions, enabling larger ion populations and repeated separations with improved detection efficiency.
Implementation Method 1
In a traveling wave (TW) separation, ions of different mobilities separate based on their relative motion in a moving electric field
Implementation Method 2
The TW creates periodic highs and valleys, and the ions are trapped in valleys if the field moves very slowly relative to their mobilities
Implementation Method 3
compressing distributions of ions into narrower peaks or redistribution of ion peaks by applying an intermittent traveling wave
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3A~3B
AI summary
Methods and apparatuses for ion peak compression and increasing resolution of ions are disclosed. Packets of ions are introduced into a device. A first electric field is applied for dispersing the ion packets temporally or spatially according to their mobilities A second intermittent traveling wave is applied for regrouping or merging the dispersed ion packets into a lesser number of trapping regions with narrower peaks. The ions packets are compressed into the narrower peak regions by varying a duty cycle of the intermittent traveling wave.