Varying Multipole Ion Guide for Mass Spectrometry
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Solution Overview
Problem
Conventional ion guides in mass spectrometry face inefficiencies due to non-optimal ion transmission conditions for ions of varying mass-to-charge ratios, leading to suboptimal ion signal and instrument sensitivity, as the dimensions of the ion beam are not optimized for both entry and exit.
Innovation Solution
An ion transport apparatus with a varying RF electrical field along its axis, featuring a major higher-order multipole component at the entrance and a predominantly lower-order multipole component at the exit, which converges the ion beam from a larger cross-section at the entrance to a smaller cross-section at the exit, optimizing ion acceptance and emission apertures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a uniform RF electrical field is applied along the ion guide axis, then the ion beam maintains a uniform cylindrical cross-section, but the ion transmission conditions are not optimal for both entry and exit simultaneously
Solution Approach 1:
The ion guide is divided into multiple sections along the axial direction, with each section applying a different multipole field configuration. The first section uses a higher-order multipole field (n1≥3/2) for optimal ion entry, while the second section uses a lower-order multipole field (n2≥3/2) for optimal ion exit. This segmentation allows each section to be optimized for its specific function, resolving the contradiction between transmission efficiency and configuration complexity.
Solution Approach 2:
Different regions of the ion guide are assigned different field characteristics tailored to local requirements. The entrance region employs a higher-order multipole field to optimize ion acceptance, while the exit region uses a lower-order multipole field to optimize ion emission. This local differentiation of field quality enables optimal performance at both ends without requiring a uniformly complex configuration throughout.
2Quantity of substance
If a higher-order multipole field is used at the ion entrance, then ion acceptance is optimized, but the field configuration becomes more complex
Solution Approach 1:
The electrode system is segmented into different groups corresponding to different sections of the ion guide. The first group of electrodes generates the higher-order multipole field for optimal ion acceptance at the entrance, while the second group generates the lower-order multipole field for optimal ion emission at the exit. This segmentation allows the complex higher-order field to be applied only where needed for ion acceptance, rather than throughout the entire guide.
Solution Approach 2:
The multipole order parameter of the RF field is changed along the axial direction of the ion guide. By varying the multipole order from n1≥3/2 at the entrance to n2≥3/2 at the exit, the system optimizes ion acceptance at the entrance while simplifying the field configuration at the exit. This parameter change allows the system to achieve optimal ion acceptance without maintaining complex configuration throughout.
3Quantity of substance
If a lower-order multipole field is used at the ion exit, then ion emission is optimized, but the ion beam cross-section is larger than ideal for focused transmission
Solution Approach 1:
The ion guide is segmented into an entrance section and an exit section with different field configurations. The exit section uses a lower-order multipole field to optimize ion emission, while the overall converging field configuration from the higher-order entrance section ensures the ion beam cross-section is appropriately reduced by the time it reaches the exit. This segmentation allows independent optimization of emission and beam size.
Solution Approach 2:
The higher-order multipole field in the entrance section performs a preliminary focusing action on the ion beam, reducing its cross-section before the ions reach the exit section. This preliminary action ensures that when the lower-order multipole field optimizes ion emission at the exit, the ion beam already has an appropriately reduced cross-section for focused transmission to downstream devices.
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 configuration enhances ion transmission efficiency by increasing ion acceptance at the entrance and reducing ion emission at the exit, resulting in a well-confined ion stream optimized for transfer to downstream devices, thereby improving ion signal and instrument sensitivity.
Implementation Method 1
the ions passing through the ion guide are subjected to a two-dimensional, radio-frequency (RF) trapping field that focuses the ions along an axial path through the electrode structure
Implementation Method 2
The plurality of electrodes is configured for applying an RF electrical field that varies along the longitudinal axis
Implementation Method 3
at the ion entrance end, the RF electrical field includes a major first multipole component of 2n1 poles where n1≧3/2, and at the ion exit end the RF electrical field includes predominantly a second multipole component of 2n2 poles where n2≧3/2 and n21
Implementation Method 4
converges the ion beam from a larger cross-section at the entrance to a smaller cross-section at the exit, optimizing ion acceptance and emission apertures
Data Source
AI summary
An ion transport apparatus includes an ion entrance end, an ion exit end, and electrodes arranged along a longitudinal axis from the ion entrance end toward the ion exit end. The electrodes are configured for applying an RF electrical field that varies along the longitudinal axis such that at the ion entrance end, the RF electrical field comprises a major first multipole component of 2n1 poles where n1≧3/2, and at the ion exit end the RF electrical field comprises predominantly a second multipole component of 2n2 poles where n2≧3/2 and n2<n1.