Dual-Section Ion Guide Assembly for Precise Ion Stream Modulation
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Solution Overview
Problem
Existing ion guide assemblies are not precise enough in modulating a stream of ions according to a modulation function, leading to inaccuracies in determining ion mobility, especially when larger ions are involved, as they take longer to traverse a given distance due to higher collision cross-sections, resulting in artificial features in ion mobility spectra.
Innovation Solution
The ion guide assembly features a dual section design with distinct sets of conveying electrodes generating different traveling waves, where the first section has a more compact arrangement and higher trapping effect, allowing ions to move uniformly regardless of mobility, and the second section has a longer wavelength and lower trapping effect, enabling precise modulation of ions by controlling the amplitudes and velocities of these waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single section ion guide is used with uniform traveling waves, then the structure is simple, but modulation precision is insufficient and larger ions cannot be accurately separated
Solution Approach 1:
The ion guide is divided into two distinct sections: a first section with conveying electrodes generating traveling waves for uniform ion transport, and a second section with different wave parameters for precise modulation. This segmentation allows each section to perform its specific function optimally, resolving the contradiction between measurement precision and structural simplicity.
Solution Approach 2:
Different sections of the ion guide are assigned different local properties: the first section uses traveling waves with specific amplitude and velocity for uniform conveyance, while the second section uses different wave parameters for precise modulation. This local differentiation enables high precision ion mobility determination without requiring the entire structure to be complex.
2Measurement precision
If DC voltages are used to convey ions, then the structure is simple, but larger ions are pushed out of potential wells by gas resistance, causing inaccurate mobility measurement
Solution Approach 1:
Instead of using static DC voltages, the patent applies periodic traveling waves to the conveying electrodes. These traveling waves create moving potential wells that continuously propel ions forward while maintaining confinement, preventing larger ions from being pushed out by gas resistance. The periodic nature of the waves enables accurate mobility measurement of all ion sizes.
3Measurement precision
If ion gate modulation is applied, then ion mobility can be determined, but the modulation is not precise enough leading to artificial features in spectra
Solution Approach 1:
The patent employs dynamic control of the ion gate with precisely timed opening and closing operations. The gate is synchronized with the traveling waves to achieve precise modulation of ion packets. This dynamic control eliminates artificial features in spectra by ensuring accurate temporal modulation, resolving the contradiction between modulation precision and time loss.
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 allows for more precise modulation of ions, ensuring that ions of varying mobilities are conveyed uniformly in the first section and separated based on mobility in the second section, enhancing the accuracy of ion mobility determination by minimizing the impact of ion size on traversal time.
Implementation Method 1
the first arrangement of conveying electrodes is adapted for generating first travelling waves having a first travelling wave amplitude and travelling along the first section of the ion guide path at a first travelling wave velocity for conveying the ions along the first section of the ion guide path
Implementation Method 2
the ion gate is adapted to provide an open state for allowing the ions passing the ion gate position when being conveyed along the ion guide path and a closed state for preventing the ions from passing the ion gate position
Data Source
Figure 1
Figure 2~3
AI summary
An ion guide (10), modulating a stream of ions according to a modulation function, wherein the stream of ions includes at least N different ion species, wherein N is at least 1. This ion guide (10) forms an ion guide path, wherein the ions of the stream of ions are conveyed along the ion guide path in a conveying direction to form the stream of ions. The ion guide (10) includes an ion gate (12) arranged at an ion gate position on the ion guide path, wherein the ion gate (12) is adapted to provide an open state for allowing the ions passing the ion gate position when being conveyed along the ion guide path and a closed state for preventing the ions from passing the ion gate position. The ion guide (10) further includes a first arrangement (13) of conveying electrodes (230) arranged along the ion guide path, the first arrangement (13) of conveying electrodes (230) extending over a first section of the ion guide path, wherein the first section of the ion guide path reaches from at least the ion gate position downstream to at least a transition position on the ion guide path, wherein the first arrangement (13) of conveying electrodes (230) is adapted for generating first travelling waves having a first travelling wave amplitude and travelling along the first section of the ion guide path at a first travelling wave velocity for conveying the ions along the first section of the ion guide path. Furthermore, the ion guide (10) includes a second arrangement (14) of conveying electrodes (240) arranged along the ion guide path, the second arrangement (14) of conveying electrodes (240) extending over a second section of the ion guide path, wherein the second section of the ion guide path reaches from the transition position downstream, wherein the second arrangement (14) of conveying electrodes (240) is adapted for generating second travelling waves having a second travelling wave amplitude and travelling along the second section of the ion guide path at a second travelling wave velocity for conveying the ions along the second section of the ion guide path. According to the method, the stream of ions is modulated with the ion gate (12) according to the modulation function and AC voltages are applied to the first arrangement (13) of conveying electrodes (230) for generating the first travelling waves and to the second arrangement (14) of conveying electrodes (240) for generating the second travelling waves for conveying the ions downstream of the ion gate (12) along the first section and the second section of the ion guide path in the conveying direction away from the ion gate (12), wherein for each ion species of the at least N different ion species, a ratio A is the average velocity of the ions of the respective ion species in the first section of the ion guide path divided by the first travelling wave velocity, wherein for each ion species of the at least N different ion species, a ratio B is the average velocity of the ions of the respective ion species in the second section of the ion guide path divided by the second travelling wave velocity, wherein the first travelling wave amplitude, the first travelling wave velocity, the second travelling wave amplitude and the second travelling wave velocity are chosen such that for each ion species of the at least N different ion species, the ratio A is larger than the ratio B.