Quadrupole Ion Guide Field Terminator for Mass Spectrometry
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Solution Overview
Problem
Ion transmission efficiency into and out of linear quadrupole ion guides in mass spectrometry is poor due to unstable ion trajectories caused by fringe fields at the axial ends, particularly affecting higher-mass ions and those with lower kinetic energy.
Innovation Solution
The implementation of a quadrupole ion guide assembly with field terminators, comprising a quadrupole lens with auxiliary DC potentials applied to plates positioned at the entrance and exit ends, which terminate the quadrupole DC field, stabilizing ion trajectories and improving transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quadrupole ion guide is used for mass filtering, then mass resolution is improved, but ion transmission efficiency deteriorates due to fringe fields at axial ends
Solution Approach 1:
A field terminator comprising four plates arranged in a quadrupole configuration is introduced as an intermediary component between the ion source and the quadrupole ion guide. This field terminator generates a controlled quadrupole field that acts as a transition region, mediating the unstable fringe field effects and improving ion transmission into the main quadrupole guide without compromising mass resolution.
Solution Approach 2:
The field terminator is positioned at the axial ends of the quadrupole ion guide to perform preliminary field termination before ions enter or exit the main quadrupole region. By pre-establishing a controlled field environment at the entrance and exit, ions are stabilized before experiencing the full quadrupole field, reducing trajectory instability and improving transmission efficiency.
2Stability of the object's composition
If DC potentials are applied to terminate quadrupole field at axial ends, then ion trajectory stability is improved, but device complexity increases
Solution Approach 1:
The field terminator uses DC potentials applied to four plates to dynamically control and terminate the quadrupole field at the axial ends. By adjusting the DC voltage parameters on these plates, the field distribution can be optimized to stabilize ion trajectories during transition regions, achieving improved stability through parameter control rather than structural complexity.
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 creating more stable transition regions at the entrance and exit ends of the quadrupole ion guide, allowing for better focusing and reduced loss of ions, especially for higher-mass and lower kinetic energy ions, while maintaining high mass resolution.
Implementation Method 1
applying auxiliary DC potentials to four plates of a quadrupole lens, the plates being spaced from each other around the guide axis and positioned at an axial distance from the entrance end or the exit end, wherein each plate is axially aligned with a respective one of the guide electrodes, and wherein the auxiliary DC potentials are applied at magnitudes and polarities relative to the main DC potentials effective for terminating the quadrupole DC field at the plates
Data Source
AI summary
A field terminator includes a plurality of electrode plates positioned around a guide axis at a radial distance therefrom. The plates generate a quadrupole DC field such that a polarity on each plate is opposite to a polarity on the plates adjacent thereto. The plates may be positioned at an axial end of a quadrupole ion guide such as a mass filter. In addition to an RF field, the ion guide may generate a quadrupole DC field. The DC field of the plates may be opposite in polarity to that of the ion guide.