Ion Mobility Spectrometry AC Gate Segmented Drift Tube
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Solution Overview
Problem
Ion mobility spectrometers (IMS) face limitations in resolution due to interference from chemical and biological molecules with similar ion mobilities, leading to false positives and difficulties in detecting low levels of target substances.
Innovation Solution
The implementation of a cross-directional gas flow in a drift tube and a segmented drift tube design, combined with the use of AC voltage on the ion gate, allows for improved ion separation and peak resolution by reducing the ion depletion area and filtering ions based on size and mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ion mobility spectrometry is used, then the system can detect ions, but resolution is limited due to interference from molecules with similar ion mobilities
Solution Approach 1:
The drift tube is divided into multiple segments, each containing a specific chemical modifier that interacts differently with various ion types. This segmentation allows for enhanced separation of ions with similar mobilities by creating distinct interaction zones along the drift path.
Solution Approach 2:
Chemical modifiers are introduced as intermediary substances in the drift tube that selectively interact with different ion types. These modifiers act as mediators that enhance the differentiation between ions with similar mobilities through specific chemical interactions.
2Ease of operation
If a gating device is used to regulate ion injection, then ion packets can be controlled, but manufacturing precision is difficult to achieve
Solution Approach 1:
The mechanical gating device is replaced with an electric field-based ion selection mechanism. Voltages applied to grid elements create electric fields that selectively transmit or block ions based on their mobility, eliminating the need for precise mechanical fabrication while maintaining operational control.
Solution Approach 2:
The system controls ion transmission by changing electrical parameters (voltages on grid elements) rather than relying on mechanical dimensions. This allows dynamic adjustment of ion packet characteristics through voltage control, avoiding manufacturing precision requirements.
3Measurement precision
If AC voltage is applied to the ion gate, then ion separation is improved, but device complexity increases
Solution Approach 1:
AC voltage is applied periodically to the ion gate grid elements, creating time-varying electric fields that enhance ion separation. The periodic nature of the voltage application allows for improved peak resolution while using standard AC power supplies and control circuits.
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 the sensitivity and resolution of IMS systems, effectively reducing interference and improving the ability to detect and identify chemical and biological molecules by providing higher peak resolution and selective ion transmission.
Implementation Method 1
IMS separate ionic species based on their ion mobility in a given media (either gas or liquid)
Implementation Method 2
The group of ions are pre-separated by an AC ion gate comprising applying at least one AC voltage to at least one of the grid elements of the AC ion gate to pass a pulse of selected ions into the drift tube
Data Source
AI summary
An ion mobility spectrometry apparatus and method used to separate ions and select some of the ions using an AC gate; the selected ions are further separated along a drift axis of a drift tube, where the AC gate is controlled using a series of AC voltages and/or frequencies to select different ions for the drift tube.