DMS Shield Flow Structure for Ion Signal Quality
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Solution Overview
Problem
In chemical analysis using DMS/FAIMS, ions near the edges of the flow channel are inadvertently filtered out, reducing the signal quality and signal-noise ratio due to uneven ion distribution and electrical field effects.
Innovation Solution
A parallel non-ionized gas flow is introduced on both sides of the ionized gas flow to create a 'shield flow' that prevents unwanted ion neutralization, allowing only desired ions to pass through the filter, thereby improving signal quality and signal-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ions are distributed evenly over the flow channel cross-section, then the filtering process can be applied uniformly, but ions near the edges are inadvertently filtered out reducing signal quality
Solution Approach 1:
The flow channel cross-section is segmented into a central region and edge regions. The central region allows ion passage while the edge regions are configured to filter or neutralize ions near the boundaries. This spatial segmentation prevents edge ions from being inadvertently filtered out while maintaining uniform filtering in the central area.
Solution Approach 2:
Different regions of the flow channel are given different functional qualities. The central region is designed for ion transmission with specific field characteristics, while the edge regions are designed with different field characteristics that prevent edge ion loss. This local differentiation of properties ensures that ions in different positions experience appropriate treatment.
2Measurement precision
If a high-frequency variable electric field is applied for ion filtering, then ion separation is achieved, but edge ions are neutralized reducing the measurement signal
Solution Approach 1:
The electric field is segmented into different spatial zones within the flow channel. The central zone applies the high-frequency variable electric field for ion separation, while the edge zones apply different field configurations that prevent neutralization of edge ions. This spatial segmentation of the electric field enables simultaneous ion separation and edge ion preservation.
Solution Approach 2:
The electric field characteristics are made local rather than uniform. Different regions of the flow channel experience different electric field strengths, frequencies, or phases. The central region experiences the full high-frequency variable field for separation, while edge regions experience modified fields that prevent ion neutralization, thus preserving the measurement signal.
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
The shield flow structure enhances the signal quality and signal-noise ratio by ensuring only intended ions are filtered, maintaining the desired passband and reducing edge ion neutralization, thus improving the measurement signal.
Implementation Method 1
the ionized gas flow is filtered using the DMS/FAIMS method, in order to remove at least some of the ions from the ionized gas flow
Implementation Method 2
In an asymmetrical field, the ions oscillate in the filter at an asymmetrical velocity, which causes a net transfer of ions towards the electrodes in an advantageous direction relative to the field
Implementation Method 3
The electrical-field-dependence of the ions is very small and this difference can be compensated by increasing the DC component CV to the frequency-changing field, which cancels a specific type of field dependence
Implementation Method 4
A parallel mainly non-ionic gas flow, which is on at least one side of the ionized gas flow, is led along with the ionized gas flow to the filter structure. The use of the solution prevents, or at least reduces, the filtering of ions that it is wished to pass through the filtering.
Data Source
Figure 1
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Figure 4~5
AI summary
The invention relates to a method for chemical analysis, in which a gas flow is ionized, the ionized gas flow (24) is led to a filtering area (28) fitted to the flow channel (18), the ionized gas flow is filtered using the DMS/FAIMS method, in order to remove at least some of the ions (25, 105) from the gas flow. A parallel mainly non-ionized gas flow (13), which is on at least one side of the ionized gas flow, is led to the filtering area together with the ionized gas flow. The invention also relates to a. corresponding structure.