Ion Guide Mass Selective Ejection Using Supplemental RF Voltage
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Solution Overview
Problem
Current ion guides in mass spectrometry face challenges in efficiently transferring ions from high-pressure regions to low-pressure regions while maintaining mass selectivity, leading to reduced duty-cycles in tandem quadrupole mass spectrometers due to narrow mass windows.
Innovation Solution
An ion guide design incorporating a plurality of electrodes with a primary RF voltage and a supplemental RF voltage applied with a longer axial repeat unit, creating axial DC and/or AC or RF voltage barriers, allowing ions to gain sufficient axial kinetic energy to overcome these barriers and exit in a mass-to-charge ratio-dependent manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional RF ion guide is used to transfer ions from high-pressure to low-pressure regions, then ion transmission is achieved, but the duty-cycle is reduced due to narrow mass windows in tandem quadrupole mass spectrometers
Solution Approach 1:
The patent applies dynamic control of RF voltages (both primary and supplemental) to the ion guide electrodes, enabling real-time adjustment of ion ejection based on mass-to-charge ratio. This dynamic voltage modulation allows the system to adaptively transfer ions across pressure boundaries without being constrained by fixed narrow mass windows, thereby increasing duty-cycle and reducing time loss.
2Productivity
If mass selective ejection is implemented to increase duty-cycle, then transmission efficiency improves, but device complexity increases due to multiple RF voltage applications
Solution Approach 1:
The ion guide electrodes serve multiple functions: they provide radial ion confinement through the primary RF voltage, enable mass-selective ejection through the supplemental RF voltage, and facilitate ion transfer across pressure boundaries. This multi-functionality allows the same electrode structure to achieve both confinement and selective ejection, improving transmission efficiency without proportionally increasing device complexity.
Solution Approach 2:
The patent utilizes parameter changes in the RF voltages (frequency, amplitude, phase) applied to the electrodes to achieve mass-selective ejection. By modulating these electrical parameters, the system can selectively eject ions based on their mass-to-charge ratio while using the same physical electrode structure, thereby improving transmission efficiency without requiring additional complex hardware components.
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 design enhances the duty-cycle of mass spectrometers by enabling mass-selective ejection of ions, increasing the transmission efficiency and resolving power, particularly in tandem quadrupole instruments.
Implementation Method 1
Known RF ion guides are designed to exploit this phenomenon by creating a pseudo-potential well wherein the minimum of the pseudo-potential well lies along the central axis of the ion guide and wherein ions are confined radially within the ion guide
Implementation Method 2
It is also well known that the time averaged force on a charged particle or ion due to an AC inhomogeneous electric field is such as to accelerate the charged particle or ion to a region where the electric field is weaker
Implementation Method 3
a second device arranged and adapted to apply one or more DC and/or AC or RF voltages to one or more electrodes in order to create one or more axial DC and/or AC or RF voltage barriers so as to confine at least some ions axially within the ion guide
Implementation Method 4
a fourth device arranged and adapted to progressively increase, progressively decrease, progressively vary, scan, linearly increase, linearly decrease, increase in a stepped, progressive or other manner or decrease in a stepped, progressive or other manner the amplitude, height or depth and/or frequency of either the first RF voltage and/or the second RF voltage such that at least some of the ions overcome the one or more axial DC and/or AC or RF voltage barriers and emerge axially from the ion guide
Data Source
AI summary
An ion guide is disclosed wherein an axial DC voltage barrier is created at the exit of the ion guide. A primary RF voltage is applied to the electrodes in order to confine ions radially within the ion guide. A supplemental RF voltage is also applied to the electrodes. The supplemental RF voltage has a greater axial repeat length than that of the primary RF voltage. The amplitude of the supplemental RF voltage is increased with time causing ions to become unstable and gain sufficient axial kinetic energy such that the ions overcome the axial DC voltage barrier. Ions emerge axially from the ion guide in mass to charge ratio order.