Quadrupole Mass Filter with Perpendicular Magnetic Field
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Solution Overview
Problem
In quadrupole mass spectrometers, carrier gas-derived ions entering along the central axis of the quadrupole mass filter cause noise due to the lack of an electric field on the central axis, leading to low measurement accuracy despite efforts to separate sample and carrier gas molecules.
Innovation Solution
A magnetic field is introduced within the quadrupole mass filter, intersecting the central axis, to deflect low-mass carrier gas ions away from the filter, while allowing sample ions to pass through by adjusting the magnetic field strength based on the mass-to-charge ratio of the analysis target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC electric field is applied to quadrupole mass filter to separate ions by mass-to-charge ratio, then mass analysis capability is improved, but carrier gas-derived ions incident along the central axis pass through without deflection causing noise
Solution Approach 1:
The patent combines the quadrupole mass filter (applying AC electric field) with a magnetic field applied perpendicular to the central axis. This merging of two field types allows the system to maintain mass analysis capability while adding deflection of central-axis incident ions, thereby reducing noise from carrier gas ions that would otherwise pass through undeflected
Solution Approach 2:
The magnetic field acts as an intermediary mechanism that deflects carrier gas ions incident along the central axis before they reach the detector. This intermediary field works in conjunction with the quadrupole's electric field to separate sample ions from carrier gas ions, with the magnetic field specifically addressing the limitation of undeflected central-axis ions
2Measurement precision
If electrodes are added to deflect light carrier ions, then separation capability is improved, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical/electrical approach of adding more deflection electrodes with a magnetic field approach. Instead of complicating the electrode structure to deflect central-axis ions, the invention uses a magnetic field applied perpendicular to the axis, which naturally deflects moving charged particles (carrier gas ions) without requiring additional complex electrode arrangements
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 effectively separates carrier gas from sample ions, reducing noise and enhancing measurement accuracy by efficiently excluding low-mass carrier gas ions and allowing high-mass sample ions to be detected.
Implementation Method 1
a magnet that forms a magnetic field in at least a part of an inside of the quadrupole mass filter in a direction intersecting the central axis
Implementation Method 2
an AC electric field is applied to four rod electrodes called a quadrupole mass filter arranged so as to surround the central axis to generate an oscillating electric field that allows only ions with a predetermined mass-to-charge ratio to pass through
Data Source
AI summary
A quadrupole mass spectrometer includes: a quadrupole mass filter with four rod electrodes arranged so as to surround a central axis; and a magnet that forms a magnetic field in at least a part of an inside of the quadrupole mass filter in a direction intersecting the central axis.