DC Ion Guide for Mass-Selective Ejection
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Solution Overview
Problem
Conventional RF quadrupole ion guides face challenges in wide mass to charge ratio range operations due to pseudo-potential radial barriers, leading to low mass to charge ratio cutoff and energy spread issues, which affect system duty cycle and ion transmission efficiency.
Innovation Solution
An ion guide with a plurality of segmented rod electrodes and a DC potential well that varies in form, shape, and amplitude along the x-direction, allowing for switching between ion guide and mass filter modes using AC excitation fields, enabling resonant, mass-to-charge ratio instability, or non-linear ejection, and facilitating mass-to-charge ratio separation based on time of flight or ion mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional RF quadrupole ion guides are used for wide mass to charge ratio range transmission, then the mass to charge ratio range is improved, but low mass to charge ratio cutoff and energy spread issues occur due to pseudo-potential radial barriers
Solution Approach 1:
The patent changes the fundamental field configuration from RF quadrupole to DC quadrupole, transforming the confinement mechanism from pseudo-potential barriers to direct electrostatic fields. This parameter change eliminates mass-to-charge ratio dependent confinement while maintaining ion transmission, resolving the contradiction between wide mass range and low mass cutoff issues
Solution Approach 2:
The patent replaces the RF electromagnetic field system with a DC electrostatic field system. By substituting the time-varying RF fields with static DC fields, the invention eliminates the pseudo-potential radial barriers that cause mass-dependent confinement, achieving mass-independent ion transmission across a wide range
2Measurement precision
If RF quadrupole ion guides operate in resolving mode for mass filtering, then mass to charge ratio filtering ability is improved, but system duty cycle decreases due to scanning requirements
Solution Approach 1:
The DC quadrupole ion guide is designed to perform multiple functions: it can operate as a wide-range ion guide, a mass filter, a time-of-flight separator, or an ion mobility separator. This multi-functionality allows the system to maintain high duty cycle while providing analytical capabilities, resolving the contradiction between filtering precision and productivity
Solution Approach 2:
The patent introduces dynamic switching capability between different operational modes (ion guide mode, mass filter mode, time-of-flight mode, ion mobility mode). By making the system dynamically adaptable to different measurement needs, it maintains high duty cycle while providing precise mass filtering when required
3Measurement precision
If ions are ejected from pseudo-potential wells in RF quadrupole guides, then mass filtering is achieved, but energy spread increases affecting coupling to second analyser
Solution Approach 1:
By replacing RF fields with DC fields, the invention eliminates pseudo-potential wells and their associated energy spread problems. Ions are confined and transmitted through direct electrostatic fields rather than being trapped in oscillating pseudo-potential wells, maintaining low energy spread while achieving mass filtering capability
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
The solution enhances the ion guide's ability to transmit a wider mass to charge ratio range with improved resolution and sensitivity, reducing energy spread and increasing system duty cycle, allowing for efficient ion separation and analysis.
Implementation Method 1
a DC quadratic potential is superimposed on the RF voltage applied to the plane of electrodes such that an axial DC potential well is formed in the z-direction
Implementation Method 2
Ions enter the ion guide in the x-direction and are confined in the y-direction by applying opposite phases of an RF voltage to adjacent rows of electrodes
Implementation Method 3
the third device may be arranged and adapted to eject ions having desired or undesired mass to charge ratios from the ion guide by resonant ejection by applying an AC excitation field in the second (z) direction
Implementation Method 4
In the second mode of operation ions may be separated in the third (x) direction according to their mass to charge ratio on the basis of their time of flight
Implementation Method 5
In the second mode of operation ions may be separated in the third (x) direction according to their ion mobility or on the basis of their differential ion mobility
Data Source
Figure 1a~1d
Figure 2a~2c
AI summary
An ion guide is disclosed comprising a plurality of electrodes. A first device is arranged and adapted to apply a RF voltage 103 to at least some of the electrodes in order to form, in use, a pseudo-potential well which acts to confine ions in a first (y) direction within the ion guide. A second device is arranged and adapted to apply a DC voltage to at least some of the electrodes in order to form, in use, a DC potential well which acts to confine ions in a second (z) direction within the ion guide. A third device is arranged and adapted to cause ions having desired or undesired mass to charge ratios to be mass to charge ratio selectively ejected from the ion guide in the second (z) direction.