Hexapole-Quadrupole Ion Guide for Mass Spectrometer Sensitivity
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Solution Overview
Problem
Mass spectrometers using atmospheric pressure ion sources face challenges in enhancing ion transport efficiency due to trade-offs between ion confinement and convergence abilities in existing ion guides, and contamination issues in ion funnels lead to performance deterioration.
Innovation Solution
A mass spectrometer with an ion transport optical system featuring N rod electrodes arranged in a hexapole-quadrupole configuration, where at least two electrodes are tilted to form a quadrupole arrangement on the emission side, allowing for inverted radio-frequency voltages and different DC voltages to enhance ion confinement and convergence, reducing contamination risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of rod electrodes in a multipole ion guide is increased to improve ion confinement ability, then ion confinement ability is improved, but ion convergence ability deteriorates
Solution Approach 1:
The ion guide is divided into multiple sections with different numbers of rod electrodes. The first section has a larger number of rod electrodes (6 or more) to provide strong ion confinement ability, while the second section has fewer rod electrodes (4) to provide strong ion convergence ability. This segmentation allows each section to optimize for its specific function without compromising the other.
Solution Approach 2:
Different sections of the ion guide are assigned different structural characteristics tailored to their specific functions. The first section (confinement section) uses a multipole configuration with more electrodes for strong radial confinement, while the second section (convergence section) uses a quadrupole configuration with fewer electrodes for strong axial convergence. Each local region has optimized properties for its intended purpose.
2Productivity
If the opening diameter of electrodes in an ion funnel is narrowed to improve ion convergence ability, then ion convergence ability is improved, but electrode contamination increases
Solution Approach 1:
The ion guide is segmented into two functional sections: a confinement section with larger opening diameter that prevents contamination, and a convergence section with smaller opening diameter that achieves ion convergence. This segmentation allows the system to achieve ion convergence without requiring the entire electrode structure to have a narrow opening, thereby reducing contamination risk.
Solution Approach 2:
The first section with larger opening diameter acts as an intermediary that guides ions while maintaining a contamination-resistant structure. It serves as a buffer zone that allows ions to be confined and prepared before entering the second section where actual convergence occurs, protecting the main convergence electrodes from direct exposure to contaminated ion streams.
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 improves ion transport efficiency, increasing analytical sensitivity by efficiently collecting and converging ions, while minimizing electrode contamination and maintaining performance stability.
Implementation Method 1
a pseudopotential is generated in the space surrounded by the rod electrodes by application of radio-frequency voltages whose phases are inverted to each other between adjacent rod electrodes around the ion optical axis, so that ions are confined and transported
Implementation Method 2
The radio-frequency ion guides confine ions in a predetermined space and transport them, mainly using a pseudopotential generated by a radio-frequency electric field
Data Source
AI summary
An ion guide (20) provided in a first intermediate vacuum chamber includes six rod electrodes (211 to 216) and a voltage generation unit. The six rod electrodes (211 to 216) are in a hexapole arrangement on the ion incident side, and the two rod electrodes (211 and 214) are tilted with respect to the Z-axis in a manner approaching a central axis (201) as they progress in the ion transport direction, so that the four rod electrodes (211, 214, 215, and 216) are in a quadrupole arrangement. The voltage generation unit applies radio-frequency voltages ±V cos ωt whose phases are inverted to each other between adjacent rod electrodes of the six rod electrodes (211 to 216) around the central axis (201), applies a DC voltage U1 to the four electrodes (211, 214, 215, and 216) by which ions pass through them in an excellent manner, and applies a DC voltage U2 different from U1 to the other two rod electrodes (212 and 213).