Selective Ion Mobility Filter for Isomeric Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current ion mobility spectrometers face limitations in achieving high mobility resolution due to diffusion broadening in long drift regions, leading to low separation capabilities for isomeric ions with similar charge-related mass but different collision cross-sections, necessitating the development of more efficient methods to select and analyze ions based on mobility.
Innovation Solution
The use of at least two consecutive mobility high pass and/or low pass filters, either for collecting ions within a predetermined range of mobilities or generating a constant beam of ions with predetermined mobility, allows for improved ion selection and analysis, enabling higher resolution mobility spectra and fragment ion mass spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long drift region is used to achieve high mobility resolution, then the separation capability for isomeric ions is improved, but diffusion broadening increases leading to reduced resolution
Solution Approach 1:
The drift region is divided into multiple segments with different gas flow velocities. The first segment has a higher gas flow velocity that reduces diffusion broadening, while subsequent segments have progressively lower velocities that maintain separation. This segmentation allows the system to achieve high mobility resolution without the full length penalty of a single long drift region, as each segment contributes differently to the overall separation process.
Solution Approach 2:
The gas flow velocity is changed progressively along the drift region length. By varying this parameter spatially - starting high and decreasing - the system optimizes the balance between reducing diffusion effects and maintaining ion separation. This parameter change strategy allows achieving high resolution with a shorter effective drift length compared to uniform velocity systems.
2Object-affected harmful factors
If a short drift region is used to reduce diffusion broadening, then mobility resolution is maintained, but the separation capability for ions with similar mobilities is reduced
Solution Approach 1:
The drift region is divided into multiple segments with different gas flow velocities. The first segment has a higher gas flow velocity that reduces diffusion broadening, while subsequent segments have progressively lower velocities that maintain separation. This segmentation allows the system to achieve high mobility resolution without the full length penalty of a single long drift region, as each segment contributes differently to the overall separation process.
Solution Approach 2:
The system uses dynamic gas flow control where the gas flow velocity is not static but varies along the drift region. This dynamic approach allows the system to adapt the gas flow conditions to optimize both diffusion reduction and ion separation, achieving high resolution with a shorter effective drift length compared to static uniform velocity systems.
3Loss of time
If high electric field strength is applied to increase ion drift velocity, then measurement time is reduced, but ion diffusion increases reducing resolution
Solution Approach 1:
The gas flow velocity is changed progressively along the drift region length. By varying this parameter spatially - starting high and decreasing - the system optimizes the balance between reducing diffusion effects and maintaining ion separation. This parameter change strategy allows achieving high resolution with a shorter effective drift length compared to uniform velocity systems.
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, allowing for the separation of ions with mobility differences as low as one percent, significantly improving the ability to distinguish between isomeric ions and increasing the number of ions available for detailed analysis.
Implementation Method 1
a laminar gas flow through the tube in a given direction and at a given velocity
Implementation Method 2
at least one electric field barrier inside the tube, which barrier has a maximum field strength
Implementation Method 3
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
Implementation Method 4
both filters are enclosed by an RF multipole field for radial confinement of the ions
Data Source
AI summary
Ions with a predetermined ion mobility range are produced by filtering ions entrained in a stream of moving gas with two ion mobility low pass filters located consecutively in the gas stream. Each filter is formed by applying a DC electric field to the gas stream which causes the ions to move in a direction opposite to the gas flow. Ions are collected between the two filters and transferred to a detector or analyzing device. In one embodiment, the maximum field strength of the electric field barrier in the first ion mobility low pass filter is continued as a plateau of essentially constant field strength up to the electric field barrier in the second ion mobility low pass filter, which has a maximum field strength higher that the maximum field strength of the electric field barrier in the first ion mobility low pass filter.