Quadrupole Mass Filter Electrode Layout for Ion Entry and Exit Losses
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Solution Overview
Problem
Conventional quadrupole mass spectrometers face challenges in improving ion passing efficiency at the ion inlet and outlet regions due to asymmetric electric fields, leading to decreased analysis sensitivity and increased costs and complexity in power supply units.
Innovation Solution
The quadrupole mass spectrometer employs a configuration where pre- and post-rod electrodes are aligned on inscribed circles with varying radii, applying the same frequency RF voltage to these electrodes to improve ion passing efficiency while maintaining simplicity in power supply units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-rod electrodes and post-rod electrodes are provided to reduce electric field disturbance at rod ends, then ion passing efficiency is improved, but device complexity and power supply complexity increase
Solution Approach 1:
The patent merges the voltage control of pre-rod electrodes and post-rod electrodes with the main rod electrodes by applying the same RF voltage signal to all electrodes. This unified voltage control approach eliminates the need for separate power supply circuits for pre and post rod electrodes, thereby reducing power supply complexity while maintaining the ion passing efficiency benefits of having pre and post rod electrodes
Solution Approach 2:
The patent makes the power supply unit universal by using a single RF voltage signal that serves multiple functions: it controls the main rod electrodes for mass filtering and simultaneously controls the pre-rod and post-rod electrodes for reducing electric field disturbance. This multi-functionality reduces the overall complexity of the power supply system
2Reliability
If pre-rod electrodes are provided to converge ions with wide m/z range, then ion passing efficiency is improved, but the DC potential distribution causes divergence actions that reduce analysis sensitivity
Solution Approach 1:
The patent introduces asymmetry in the pre-rod electrode configuration by setting different DC voltage values for pre-rod electrodes positioned in the X-axis direction versus those positioned in the Y-axis direction. Specifically, pre-rod electrodes in the X-axis direction are given a positive DC voltage while those in the Y-axis direction are given a negative DC voltage, creating an asymmetric electric field that compensates for the natural divergence caused by the main rod electrode potential distribution
Solution Approach 2:
The patent applies different DC voltage values to pre-rod electrodes based on their specific spatial position and orientation. By tailoring the DC voltage applied to each pre-rod electrode according to its location (X-axis vs Y-axis direction), the patent creates locally optimized electric field conditions that improve ion convergence in specific directions while maintaining overall ion passing efficiency and analysis sensitivity
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 passing efficiency across all stages, including entry, transition, and exit regions, thereby improving analysis sensitivity without increasing power supply complexity or cost.
Implementation Method 1
A voltage of +(U+V cos ωt) created by superimposing a radio-frequency (RF) voltage V cos ωt on a DC voltage U is applied to two rod electrodes facing each other across the central axis
Implementation Method 2
ions having m/z can pass through the quadrupole mass filter selectively
Data Source
AI summary
A quadrupole mass spectrometer includes a quadrupole mass filter including: a main rod portion including four main rod electrodes; a pre-rod portion including four pre-rod electrodes, where, at an end opposite to the main rod portion, the four pre-rod electrodes are disposed to be aligned on an inscribed circle having the same radius centered on the ion optical axis, and, at the other end facing the main rod portion, two pre-rod electrodes facing each other across the ion optical axis and the other two pre-rod electrodes are disposed to be aligned on an inscribed circle having different radii centered on the ion optical axis; a main voltage applying unit to apply, to each main rod electrode, a voltage created by superimposing a DC voltage and an RF voltage; and a pre-voltage applying unit to apply an RF voltage having a same frequency as the RF voltage to each pre-rod electrode.